Next Article in Journal
Chemoprevention of Lung Cancer: Prospects and Disappointments in Human Clinical Trials
Previous Article in Journal / Special Issue
Molecular Targeted Agents for Gastric Cancer: A Step Forward Towards Personalized Therapy

Cancers 2013, 5(1), 92-130; doi:10.3390/cancers5010092

Review
Mouse Models of Gastric Cancer
Yoku Hayakawa 1, James G. Fox 2, Tamas Gonda 1, Daniel L. Worthley 1, Sureshkumar Muthupalani 2 and Timothy C. Wang 1,*
1
Department of Medicine and Irving Cancer Research Center, Columbia University Medical Center, New York, NY 10032, USA
2
Division of Comparative Medicine, MIT, Cambridge, MA 02139, USA
*
Author to whom correspondence should be addressed; E-Mail: tcw21@columbia.edu.
Received: 5 December 2012; in revised form: 8 January 2013 / Accepted: 15 January 2013 /
Published: 24 January 2013

Abstract

: Animal models have greatly enriched our understanding of the molecular mechanisms of numerous types of cancers. Gastric cancer is one of the most common cancers worldwide, with a poor prognosis and high incidence of drug-resistance. However, most inbred strains of mice have proven resistant to gastric carcinogenesis. To establish useful models which mimic human gastric cancer phenotypes, investigators have utilized animals infected with Helicobacter species and treated with carcinogens. In addition, by exploiting genetic engineering, a variety of transgenic and knockout mouse models of gastric cancer have emerged, such as INS-GAS mice and TFF1 knockout mice. Investigators have used the combination of carcinogens and gene alteration to accelerate gastric cancer development, but rarely do mouse models show an aggressive and metastatic gastric cancer phenotype that could be relevant to preclinical studies, which may require more specific targeting of gastric progenitor cells. Here, we review current gastric carcinogenesis mouse models and provide our future perspectives on this field.
Keywords:
gastric cancer; mouse model; metaplasia; Helicobacter felis; Helicobacter pylori; INS-GAS mice

1. Introduction

Gastric cancer remains the 2nd leading cause of cancer mortality worldwide, with an overall 5-year survival rate that is less than 25% [1,2]. Critical to understanding the mechanisms involved in gastric cancer, and devising preventive and therapeutic interventions, is the need to develop an authentic animal model. Mice have a different gastric anatomy compared to humans. In mice the gastric fundus equivalent is lined by squamous, rather than oxyntic glandular epithelium. Thus, in mice, the squamocolumnar junction does not universally approximate the gastroesophageal junction as it does in normal human anatomy. In addition, rodents rarely develop spontaneous gastric cancer, although some reports have described spontaneous gastric adenocarcinomas in cotton rats (Sigmodon hispidus), and in the Z strain of the African rodent Mastomys natalensis [3,4,5,6,7]. However, these animals when they develop gastric tumors more frequently exhibit enterochromaffin-like cell carcinoids. Thus, experimental efforts have focused on identifying chemical, infectious or genetic means to induce gastric cancer in animals.

Prior to the discovery of Helicobacter pylori infection, major etiological factors were thought to be a diet rich in salt and nitrates/nitrites, along with a low intake of ascorbic acid and carotenoids [8], and thus early animal models utilized nitrosamines, such MNNG in rats [9,10] and MNU in mice to induce gastric tumors [11].

With the discovery of H. pylori by Marshall and Warren [12], and subsequently studies showing a strong association with gastric cancer [13,14,15,16,17], the focus shifted to the development of animal models of Helicobacter-associated gastric cancer. A variety of animals, including mice, rats, Mongolian gerbils, cats, guinea, pigs, ferrets, pigs, and macaques, have been experimentally infected with a variety of different Helicobacter species. Because of the ability to manipulate the mouse genome, mice have become the animal model of choice for cancer research. While the greatest interest has been in mouse models, only a limited number of H. pylori strains have been identified that successfully colonize the mouse stomach. The most robust and useful models to date have been H. pylori SS1-infected mice, and H. felis originally isolated from the stomach of cats and dogs [18]. Both of these gastric Helicobacters are capable of long-term colonization and have the ability to induce chronic gastritis and precancerous lesions in mice. However, the SS1 strain is not able to induce gastric cancer in most inbred strains of mice, while it does cause gastric carcinoma in C57BL/129 mice [19,20]. Chronic H. felis infection has been shown to induce severe inflammation, atrophy, metaplasia, dysplasia and gastric cancer in C57BL/6 mice [21].

While genetically engineered mouse models of cancer were developed in the 1980’s, transgenic models of gastric cancer were slow to emerge. Initial models included some containing a variety of oncogenes that were known to transform but had no known association with human gastric cancer, such as the SV40 T antigen, which binds to pRb and disrupts its function [22]. Human carcino-embryonic antigen (CEA) promoter/SV40 T antigen transgenic mice were reported to develop antral hyperplasia or gastric cancer [23,24]. Stomach-specific SV40 T antigen transgenic mice using H/K-ATPase-β subunit gene promoter [25] developed hyperplasia and abnormal cell distribution within the gastric glandular unit, and rarely developed dysplasia. Other early models included transgenic mice carrying the human adenovirus type 12 (Ad12) early region 1 under control of the mouse mammary tumor virus (MMTV) long terminal repeat (LTR), which developed adenocarcinoma or adenosquamous carcinoma [26]. In addition, transgenic mice expressing HPV-16 early region of the bovine keratin 6 gene promoter developed glandular stomach tumors [27]. However, these models did not progress to cancer through the atrophy-metaplasia-dysplasia sequence, as described by Correa [28], nor were they associated with Helicobacter infection or chronic inflammation.

INS-GAS mice as a model of spontaneous gastric cancer were first described in 2000. These mice were reported to develop atrophic gastritis and intestinal metaplasia, followed by corpus cancer with a high incidence rate, and tumor development was accelerated by H. felis infection, suggesting that this model closely mimicked the clinical course of human gastric carcinogenesis [29]. This initial mouse model was followed by the H/K-ATPase-IL-1β transgenic mice, which progressed through the atrophy-metaplasia-dysplasia sequence and validated human genetic data that implicated the IL-1β gene locus as a major risk factor for gastric cancer [30]. Other studies using genetic mouse models of gastric cancer have been reported, and are detailed below. These genetic mouse models have provided considerable insight on the role of the stroma, also known as the tumor microenvironment, which has been recognized as a critical factor in various types of cancer. Modulation of cytokines, chemokines or the signaling pathways upstream has also demonstrated unequivocally the importance of inflammatory responses in gastric cancer development [31,32,33,34].

Nevertheless, despite the significant advances made utilizing diverse mouse models, these models have all shown some limitations, including modest gastric pathology, slow time course, and the absence of invasive or metastatic tumors. In addition, it is important to keep in mind that the response to infection or genetic manipulation is highly dependent on the mouse genetic background, gender, diet and housing conditions. Animal stress associated with overcrowding, inadequate sanitation, and variations in temperature, humidity, and light cycles may predispose resistant animals to adverse disease outcomes. Especially in the case of the enterohepatic Helicobacter species, differences in study outcomes may be attributed to persistent colonization by these murine Helicobacters [35,36,37].

Here we review these genetic or chemical models of gastric carcinogenesis, and compare their pathological features, limitations and contribution to our understanding of gastric carcinogenesis. We also emphasize the impact of comprehensive genomic analysis on new or emerging transgenic mouse models.

2. Chemical Carcinogenesis Models of Gastric Cancer

To explore the mechanisms of gastric cancer development and establish a useful animal model of gastric tumorigenesis, investigators examined the utility of a variety of chemical carcinogens. In particular, researchers focused on N-nitroso compounds, which are generated in the stomach by anaerobic bacteria following ingestion of nitrates and nitrites, which were thought to be an important inducer of human cancer. N-methyl-N-nitro-N-nitrosoguanidine (MNNG) was the first nitrosamine shown by researchers to induce stomach tumors in rats. In 1966, Schoental et al. administered MNNG to rats using a stomach tube, resulting in squamous cell carcinoma in the rat forestomach [38]. In 1967, Sugimura et al. modified their method, administering MNNG orally to rats continuously in the drinking water, and achieved for the first time a high incidence of antropyloric adenocarcinoma [10]. MNNG was later found to be a very potent gastric carcinogen in Mongolian gerbils [39,40]. Exposure to 400 ppm MNNG in drinking water for 50 weeks resulted in gastric adenocarcinomas in 63.6% of gerbils [40]. Using MNNG-induced gastric cancer model, it has been reported that administration of high-salt diet [41,42], calcium-deficient diet [43], catechol [44], or IL-1β [45] promotes gastric cancer development.

Rats and gerbils are limited as model systems, given the absence of genetic models, and thus investigators explored the effect of oral administration of nitrosamines in inbred strains of mice. However, mice proved to be remarkably resistant to MNNG-induced gastric carcinogenesis. Danon et al. infected female Balb/c mice with H. heilmannii and administered 150 ppm MNNG in drinking water for 38 weeks and found that the treated mice developed squamous cell carcinomas in the mouth and forestomach, but not adenocarcinoma in the glandular stomach [46].

Researchers then explored the utility of N-methyl-N-nitrosourea (MNU) as a gastric carcinogen in mouse models. Tatematsu et al. treated Balb/c mice with 0.5 mg MNU by weekly intragastric intubation, but found that most of the mice died due to squamous cell carcinoma in the forestomach. Interestingly, when the mouse forestomach was removed surgically prior to MNU treatment, well-differentiated adenocarcinoma developed in the glandular stomach with 100% incidence rate by 40 weeks [11]. Thus, the glandular stomach was indeed sensitive to the carcinogenic effects of MNU, but the phenotype was obscured by the greater sensitivity of the forestomach, at least at that specific dose and route of administration. Tatematsu et al. went on to demonstrate that 30–120 ppm MNU given in drinking water was preferable to oral gavage, without the induction of tumors of the forestomach [47]. The efficiency of tumor induction by MNU was found to depend on its concentration rather than total intake [48], and MNU in the drinking water at 240 ppm on alternate weeks (total exposure; 5 weeks) was effective in inducing gastric cancer in 6 strains of mice that were studied [49]. Consequently, the protocol of 240 ppm MNU treatment in the drinking water for 5 weeks (every other week) is currently a standard and widely used murine method of gastric carcinogenesis. MNU-induced tumors in mice are located mainly in the gastric antrum, and pathologically are uniformly well- or moderately-differentiated adenocarcinomas (Figure 1). The tumors are rich in stromal cells, and occasionally invade into the submucosa although signet ring-cell carcinoma and metastatic tumors are rarely, if ever seen.

The MNU mouse model of gastric cancer has been extensively used for investigating the role of various signaling pathways or transcription factors in gastric carcinogenesis, including the roles of p53 [50], NF-κB [51], MAPK pathway [52,53], Cox-2 [54,55], β-catenin [54], E-cadherin [56], and KLF4 [57]. Although MNU is an alkylating agent that can potentially induce the formation of DNA adducts and GC > TA transversion mutations, only rare mutations have been observed in N-nitroso-compounds (NOC)-induced gastric tumors of rodents [58], raising questions about the precise mechanism of carcinogenesis. MNU is also known to modify amino acids in histone proteins, especially histone H3 lysine residues, leading to chromatin remodeling [59]. Indeed, MNU treatment in mice affects the expression of TFF1, an important gastric-specific tumor suppressor gene, through epigenetic modifications. DNA and histone methylation, and promoter methylation of the TFF1 gene have also been observed in human gastric cancer [60]. This suggests that epigenetic effects are likely to constitute a key mechanism of NOC-induced carcinogenesis.

One potential criticism of the MNU mouse model of gastric cancer is the absence of Helicobacter spp.-associated chronic inflammation. While the MNU model does not proceed through a classical atrophy-metaplasia-dysplasia sequence, this latter H. pylori-dependent pathway results in achlorhydria with subsequent bacterial overgrowth; NOCs may be generated from nitrates and nitrites in this setting, and thus the argument can be made that the generation of N-nitroso compounds may play a role in Helicobacter-associated carcinogenesis. A recent study used a combination of MNU and H. felis infection [60], and achieved a very rapid induction of antral gastric cancer. This same combination was reported to induce a high frequency of gastric cancer in H. pylori-infected Mongolian gerbils compared to gerbils receiving MNU only [61,62]. Thus, the combination of Helicobacter spp. infection followed by MNU treatment mimics in some ways the proposed pathogenesis of human antral carcinogenesis.

Cancers 05 00092 g001 1024
Figure 1. MNU-induced mouse tumor. Top panels: Low and high magnification images of the distal corpus showing gastric dysplasia (glandular proliferation with architectural distortion and cytological atypia in the superficial half of the mucosa) associated with oxyntic loss and pyloric-type glandular metaplasia. (Bar: Left 200× or 80 μM, Right 400× or 40 μM) Bottom panels: Low and high magnification images of a gastric tumor biopsy specimen showing dysplastic glands with lamina propria invasion, effacement and associated desmoplasia and inflammation. (Bar: Left 100× or 160 μM, Right 400× or 40 μM).

Click here to enlarge figure

Figure 1. MNU-induced mouse tumor. Top panels: Low and high magnification images of the distal corpus showing gastric dysplasia (glandular proliferation with architectural distortion and cytological atypia in the superficial half of the mucosa) associated with oxyntic loss and pyloric-type glandular metaplasia. (Bar: Left 200× or 80 μM, Right 400× or 40 μM) Bottom panels: Low and high magnification images of a gastric tumor biopsy specimen showing dysplastic glands with lamina propria invasion, effacement and associated desmoplasia and inflammation. (Bar: Left 100× or 160 μM, Right 400× or 40 μM).
Cancers 05 00092 g001 1024

3. Helicobacter Infection Models

Given the key role of Helicobacter pylori infection in the etiology and pathogenesis of gastric cancer, researchers pursued the development of animal models of gastric Helicobacter infection. The first studies supporting a potent carcinogenic role for Helicobacter species in the gastric mucosa was the ferret model of Helicobacter mustelae infection [63,64,65]. Ferrets naturally infected with H. mustelae exposed to one dose of 100 mg/kg MNNG developed gastric cancer, while H. mustalae infected ferrets did not [63]. Unfortunately, SPF ferrets not infected with H. mustelae were not available to ascertain whether these animals also would develop MNNG-induced gastric cancer. Subsequently, aged H. mustelae-infected ferrets have been reported to develop gastritis, dysplasia, and gastric adenocarcinoma [66].

With respect to H. pylori, several H. pylori strains, such as the G1.1 strain [67], the TN2 strain [68], or the B128 strain [69], have the ability to colonize Mongolian gerbils, and induce gastric adenocarcinoma. This has allowed researchers to infect Mongolian gerbils with a variety strains, including their isogenic mutants, in order to investigate the importance of bacterial virulence factors in gastric carcinogenesis [67,68,70].

Interestingly, mice in general and the C57BL/6 strain in particular are proved to be remarkably resistant to colonization with various H. pylori strains [71,72]. Thus, alternative mouse models of gastric Helicobacter infection were explored. In 1990, Helicobacter felis, a close relative of H. pylori that was isolated from the cat stomach, was shown to readily colonize the mouse stomach in large numbers [73]. Several papers reported that H. felis had the ability to induce severe gastritis and atrophy in mice [73,74,75]. Moreover, with a longer time period of observation, analysis of H. felis-infected mice showed gastric metaplasia, dysplasia and invasive cancer [21,76]. After 12–16 months of infection, extensive dysplastic lesions were evident in the gastric corpus at the squamocolumnar junction (SCJ) along the lesser curvature. After more extended periods of infection (up to 2 years), large polypoid antral tumors develop and mimic closely lesions found in humans infected with H. pylori [77,78]. In the H. felis infection model, eradication of Helicobacter infection at early time points led to a regression of inflammation, restoration of parietal cells, reestablishment of normal architecture, and prevention against development of adenocarcinoma. Bacterial eradication at 1 year was also associated with the reappearance of parietal cells and partial restoration of architecture. Thus, eradication studies in mice have revealed that inflammation, metaplasia, and dysplasia are reversible with early eradication therapy, and that progression to dysplasia can be arrested with eradication therapy at a later time point [79,80]. In humans, eradication of H. pylori in patients with gastritis but not dysplasia is linked to a decrease in the incidence of gastric adenocarcinoma epidemiologically [81,82], thus supporting findings in mouse models. Antibiotic treatment to eradicate H. pylori in gerbils and INS-GAS mice also arrests progression to gastric lesions [73,83].

Strains of H. pylori that can colonize mice—the so-called “mouse adopted strains of H. pylori”—have been developed. Among H. pylori mouse adapted strains reported to date, the Sydney strain of H. pylori (SS1) has been the best characterized and most useful in murine model systems [20]. Relatively high levels of colonization were achieved in inbred C57BL/6 mice, while colonization levels in Balb/c, DBA/2, and C3H/He strains were lower [20]. After 8 months of infection, active gastritis and severe atrophy were observed, along with detectable levels of bacteria [20]. However, even with a 2-year follow-up, lesions did not progress to gastric cancer in mice infected with SS1 or other strains, 119p and G50, although some mice developed gastric lymphoma [84]. H. pylori SS1 infection did result in development of carcinomas in situ in C57BL/129 mice 15 months after infection [19]. H. pylori infection also causes gastric cancer in genetically modified mice, for example, INS-GAS mice (see below) [85].

In H. pylori, the cag pathogenicity island (cag-PAI), a 40-kb genomic fragment containing 31 genes, encodes a type IV secretion (TFSS) apparatus used to inject bacterial proteins such as the 120-kilodalton protein CagA into host epithelial cells [78]. A series of in vitro reports have established that injection of CagA into host cells leads to phosphorylation of CagA by host cell kinases, resulting in activation of SHP-2 tyrosine phosphatase, NF-κB signaling pathways, and MAPK signaling pathways [86,87,88]. The H. pylori peptidoglycan is also injected into host cells via the type IV secretory system, leading to activation of Nod1, an intracellular pathogen recognition molecule with specificity for gram-negative peptidoglycans [89], and mice deficient in Nod1 are more susceptible than wild-type (WT) mice to infection by cag-positive strains of H. pylori [89].

Interestingly, while the H. pylori SS1 strain was initially reported to possess an intact cag-PAI, the SS1 strain used in subsequent studies does not appear to express CagA, which may be explain to some extent the limited virulence of SS1 in mice [90]. Systemic expression of CagA in transgenic mice has led to the development of gastrointestinal and hematological malignancies [91]. mice deficient in Nod1 are more susceptible than wild-type mice to infection by cag-positive strains of H. pylori [89]. Arnold et al. used CagA-positive SS-1 (PMSS1, which was original strain isolated from a patient) and showed that mice infected with PMSS1 rapidly develop gastritis, gastric atrophy, epithelial hyperplasia, and metaplasia in a type IV secretion system-dependent manner [92]. These results suggest that CagA and/or the cag-PAI may play an important role in gastric carcinogenesis. Nevertheless, in mice, cag-negative strains such as H. felis appear to be at least as carcinogenic as cag-positive H. pylori strains. Although the ability of PMSS1 to inject CagA into host cells decreases gradually after 1 month infection and disappear after 3 months, strong inflammation and phenotypic changes could be sustained for more than 6 months [92]. In addition, inactivation in a H. pylori strain of the cagE gene coding for TFSS delayed the progression to carcinoma, but neoplasia ultimately developed in all infected INS-GAS mice with the H. pylori mutant [85]. Thus, taken together, these observations might suggest that the induction of gastric preneoplasia in mice is affected by host factors, such as the inflammatory response or other genetic factors.

Support for the importance of host genetic factors modulating gastric carcinogenesis includes observations regarding Helicobacter colonization of various inbred mouse strains, which revealed markedly different responses [75,76,93]. For example, the C57BL/6 strain is more sensitive than the Balb/c strain to H. felis-induced gastric atrophy. Potential explanations include the more T-helper-1 (Th1)-dependent immune response in C57BL/6 mice, compared to a Th2-dominant immune response in Balb/c mice [76], or possibly the reduced activity of phospholipase A2 in C57BL/6 mice [76,94]. Susceptible strains such as C57BL/6 mice show much higher levels of pro-inflammatory cytokines such as IFN-γ. The use of immunodeficient mice or mice which are deficient or overexpressing cytokines such as IFN-γ, IL-10, IL-4, or IL-7, have been useful for investigating the role of the host’s immune system in development and severity of gastritis and following mucosal changes [32,95,96,97,98,99,100,101,102]. In addition, in susceptible strains such as C57BL/6 mice, H. felis-induced proliferation and apoptosis are markedly increased compared with resistant strains [76]. The role of apoptosis was further studied through the combination of Helicobacter infection and mice which lack apoptosis-related genes, such as Fas [103,104], p53 [21], or IKK-β [105]. These studies have supported the notion that increased apoptosis is critical in the development of atrophy, metaplasia, and dysplasia.

Mouse models of Helicobacter infection have been used to examine the role of other co-factors in gastric carcinogenesis, such as gender, diet, and co-infection. Gender may be important, since gastric cancer is much more prevalent in men compared to women. Helicobacter infection of some murine strains, such as H. felis or H. pylori infection of INS-GAS mice (see below), results in greater gastric carcinogenesis in male mice compared to female mice [85,106]. However, C57BL/6 mice infected with H. felis did not show significant gender differences in the incidence of gastric carcinoma [21,85], suggesting the different mechanisms of carcinogenesis in these models. Indeed, some studies of Helicobacter infection in mice indicate that female C57BL/6 mice are more susceptible to gastric disease [107,108]. High salt diets, and diets rich in nitrates and nitrites, have been associated with an increased gastric cancer risk. Treatment with N-nitroso compounds, such as MNU, prior to H. pylori infection caused more severe preneoplastic changes and increased gastric cancer as mentioned above [109,110]. C57BL/6 mice infected with SS1 and fed a high-salt diet developed more pronounced gastric atrophy and foveolar hyperplasia [111]. Concurrent parasitic infection may also alter the effects of Helicobacter infection. Co-infection of C57BL/6 mice with the helminth, Heligmosomoides polygyrus, along with H. felis, reduced the severity of gastric atrophy and preneoplastic lesions seen with H. felis alone [112]. This was associated with a shift from the usual Th1 mucosal immune response to a polarized Th2 response. Finally, gastric atrophy due to chronic H. pylori infection is associated with bacterial overgrowth, which has been postulated to be an additional risk factor for gastric cancer. Germ-free INS-GAS mice infected with H. pylori developed less severe and delayed gastric preneoplastic lesions compared with SPF-conditioned INS-GAS mice [113], suggesting that commensal bacterial flora in the stomach also influenced the development of gastric cancer.

Mouse models of Helicobacter-induced gastric cancer make it possible to explore the origin of cancer cells and surrounding tissues. By using a bone marrow transplantation technique, Houghton et al. reported that chronic infection of C57BL/6 mice with H. felis results in population of the stomach with bone marrow-derived cells (BMDCs), and that these cells progress through metaplasia and dysplasia to intraepithelial cancer [114]. These findings were confirmed in an independent study, which showed that H. pylori infection also recruits and accumulates BMDCs in gastric epithelium [115]. Fibroblasts around gastric cancer, which have been called cancer-associated fibroblasts (CAFs) recently, are expanded by H. felis infection, and they were reported to be partly derived from bone marrow [31,116].

Taken together, studies to date have demonstrated that mouse models of chronic Helicobacter infection are robust and reproducible models that provide insights into the molecular mechanism of gastric carcinogenesis. However, there are limitations to Helicobacter mouse models, which include: the limited strains of H. pylori, particularly cag positive strains, that are able to colonize in mice; the slow time course for the development of tumors; the low incidence rate of advanced or invasive gastric cancer; anatomical differences (e.g., forestomach) between human and mice; the predominance of high grade dysplasia/early gastric cancers; and the absence of metastatic disease in these carcinogenesis models.

4. Genetically Engineered Mouse Models

Progress in genetic engineering technology leading to the development of transgenic or knockout mice has been useful for developing additional models of gastric cancer that have also shed light on the role of host genetic factors in gastric cancer development. These have included overexpression (or deficiencies) of growth factors and cytokines, as well as mutation of classical tumor suppressor genes and oncogenes. Below we have summarized six sets of animal models that have been reasonably well validated and that have provided unique insights into the pathogenesis of gastric adenocarcinoma. In addition, we mention briefly several other useful genetic models.

4.1. INS-GAS Mice

Although Zollinger-Ellison syndrome patients associated with syndrome type I MEN are likely to develop ECL cell carcinoid tumors [117], clear evidence of epidemiological correlation between hypergastrinemia and gastric cancer in human has not been reported. However, a subset of patients infected with H. pylori show mild-moderate increases in circulating levels of amidated gastrin, and thus a role for gastrin in gastric cancer was suggested, given its known role as a growth factor for the stomach [118]. Twenty years ago, the insulin-gastrin (INS-GAS) transgenic mice were created, initially to study the role of gastrin on pancreatic islet cell formation [119]. The INS-GAS transgene consisted of the insulin promoter upstream of the human gastrin coding sequences, and resulted in the overexpression of amidated gastrin (primarily G-17) in the pancreatic β-cells, leading to two-fold elevations in serum levels of human amidated gastrin. When crossed with MT-TGF-α transgenic mice, the combination of gastrin and TGF-α was able to synergistically stimulate islet growth, although neither peptide alone was sufficient to stimulate pancreatic islet growth [120]. However, given the increases in circulating gastrin, subsequent investigations focused on the effects of gastrin on the gastric mucosa [29]. Young INS-GAS mice showed increased maximal gastric acid secretion and parietal cell mass, but interestingly progressed later to decreased parietal cell mass (atrophy), hypochloryhydria and worsening hypergastrinemia, in association with increased epithelial proliferation [29,121,122]. Over time, INS-GAS mice (in an FVB background) showed progression to gastric metaplasia and dysplasia, with the development of invasive gastric cancer in the corpus at 20 months of age (Figure 2). Infection of INS-GAS mice with H. felis or H. pylori led to accelerated development of intramucosal carcinoma (in <12 months), with submucosal invasion and intravascular invasion [29,85]. Interestingly, the FVB/N inbred strain was most susceptible, while uninfected INS-GAS mice in a C57BL/6-background also developed mild gastric corpus hyperplasia and low-grade dysplasia [123], they did not progress to gastric cancer, even in the setting of H. felis infection.

Cancers 05 00092 g002 1024
Figure 2. INS-GAS mouse tumor. Gross image: Stomach of a H. pylori-infected male INS-GAS mouse at 7 mpi showing coalescing diffuse tumors of the glandular stomach. Bottom panels: Low and high magnification H&E images of the stomach of an Hp-infected male INS-GAS mouse at 7 mpi showing diffuse high grade dysplastic/neoplastic glandular proliferation with lamina propria invasion consistent with the diagnosis of intramucosal carcinoma. Other features present include prominent mixed inflammation, erosions, mucosal/glandular degeneration/necrosis, glandular ectasia, oxyntic loss, severe hyperplasia, pseudopyloric and foveolar type metaplasia as well as glandular herniation.

Click here to enlarge figure

Figure 2. INS-GAS mouse tumor. Gross image: Stomach of a H. pylori-infected male INS-GAS mouse at 7 mpi showing coalescing diffuse tumors of the glandular stomach. Bottom panels: Low and high magnification H&E images of the stomach of an Hp-infected male INS-GAS mouse at 7 mpi showing diffuse high grade dysplastic/neoplastic glandular proliferation with lamina propria invasion consistent with the diagnosis of intramucosal carcinoma. Other features present include prominent mixed inflammation, erosions, mucosal/glandular degeneration/necrosis, glandular ectasia, oxyntic loss, severe hyperplasia, pseudopyloric and foveolar type metaplasia as well as glandular herniation.
Cancers 05 00092 g002 1024

Although H. pylori infection on its own is slow to induce gastric atrophy, and is unable to induce gastric cancer in the majority of strains of WT mice, it is highly effective as a gastric carcinogen in INS-GAS mice. Thus, multiple studies from independent laboratories have now confirmed that H. pylori infection of INS-GAS mice leads to accelerated gastric cancer. The model has been widely used, particularly to examine the importance of various kinds of gene expressions [34,124,125,126,127,128], antagonists or inhibitors [129,130], bacterial factors or commensal flora [80,83,85,113], gender difference or sex hormones [106,131,132,133], dietary cofactors [134], and apoptotic factors [135,136] in gastric carcinogenesis, as well as to analyze non-gastric diseases such as colon cancer [137,138], intestinal crypt regeneration [139], or iron-deficiency anemia [140] (Table 1). In addition, the model has proved highly useful for studies of cancer prevention, given the high degree of reproducibility and the relative rapid development of cancer in this model.

Table Table 1. Applications of INS-GAS mouse model.

Click here to display table

Table 1. Applications of INS-GAS mouse model.
Purpose of analysisResults
Pancreatic islet cell formation [120]gastrin and TGF-α synergistically stimulate islet growth
H. pylori and gastric mucosa [29]progression to gastric atrophy, metaplasia, dysplasia, and cancer
Colonic carcinogenesis by AOM [137,138]progastrin, not gastrin, promotes colon carcinogenesis
Gender differences [85,106]greater gastric carcinogenesis in male INS-GAS mice with H. pylori
Importance of CagE [85]loss of cagE temporally retards but does not abrogate cancer progression
Interaction with G-Gly [124]G-gly synergizes with amidated gastrin to stimulate acid secretion and inhibits atrophy
CCK2R and Histamine receptor inhibitors [129]CCK2R and H2R antagonists synergistically inhibit gastric atrophy and cancer
Intestinal crypt regeneration [139]hypergastrinemia increases regeneration of intestinal injury
Apoptosis of gastric epithelium [135,136]gastrin induces apoptosis and contribute to gastric carcinogenesis
Gene expression profiling [125]identify up- and down-regulating genes among 12,000 cDNA
TFF2 expression [126]TFF2 expression in the gastric fundus was elevated in INS-GAS mice
Swedish variant of moist oral smokeless tobacco [134]tobacco promotes cancer formation in H. pylori-infected INS-GAS mice
Reg-1 expression [127]Reg1 is increased in the stomachs of H. felis-infected INS-GAS mice
Role of 17-beta-estradiol [131,132,133]17beta-estradiol has protective effects on gastric cancer development
Eradication of Helicobacter [79,80,83]eradication inhibits mouse gastric carcinogenesis
Commensal bacterial flora in the stomach [113]SPF mice are more susceptible to gastric cancer than germ-free mice
Antral carcinogenesis [60,123]gastrin suppresses antral carcinogenesis
HB-EGF, MMP-7, EMT protein [128]neutralisation of gastrin in INS-GAS mice reduced MMP-7, HB-EGF and EMT proteins
Acetic acid and cytoreduction [130]acetic acid could be a potent cytoreductive treatment of gastric cancer
Effect of IL-8 [34]IL-8 promotes gastric carcinogenesis in INS-GAS mice
H. pylori-induced iron deficiency [140]marked changes in expression of gastric iron transporters in H. felis-infected INS-GAS mice

4.2. Gastrin Knockout Mice

As noted above, while a subset of H. pylori-infected patients exhibit significant hypergastrinemia (e.g., 2-fold elevations in gastrin), most patients infected with H. pylori do not. In fact, many H. pylori infected patients with pan-gastritis who develop gastric atrophy show depressed levels of circulating gastrin. Thus, it was not entirely surprising when several laboratories reported that gastrin knockout (GAS-KO or GAS−/−) mice were also susceptible to stomach cancer. However, in contrast to the hypergastrinemic INS-GAS mice which developed corpus cancers, GAS−/− mice exhibited antral gastric cancers. GAS−/− mice (C57BL/6 strain) were first generated by Koh et al., and the initial phenotype reported was fairly unremarkable, with mild changes in gastric architecture, including a slight decrease in the number of parietal and enterochromaffin-like cells [141]. However, an independent group reported that a separate line of 129/Sv GAS−/− mice, showed hypochlorhydria and bacterial overgrowth, resulting in increased gastric inflammation [142]. Moreover, these GAS−/− mice that were kept in conventional (non-SPF) housing conditions developed spontaneous antral tumors [143]. These findings were confirmed by an independent group, and the GAS−/− mice were also found to be more susceptible to MNU-induced antral cancer compared to WT mice in the same genetic background [60].

Taken together, these reports suggest that gastrin has distinct functions in the gastric corpus and gastric antrum. Indeed, in contrast to the gastrin response observed in the corpus, hypergastrinemic INS-GAS FVB mice infected with H. felis showed decreased mucosal changes in the antrum relative to WT mice [123], and INS-GAS mice were found to be more resistant to MNU-induced antral tumors [60]. The antral tumor suppressive function of gastrin could be explained to some extent by its effect on stimulating acid secretion leading to inhibition of bacterial overgrowth. However, Dimaline et al. first reported that gastrin regulates TFF1 gene expression, providing a link between gastrin and a known tumor suppressor gene (see below). Tomita et al. went on to demonstrate that gastrin regulates TFF1 expression in vivo and in vitro through DNA methylation and histone modification [60]. Therefore, these studies suggest that amidated gastrin (e.g., G-17) increases corpus proliferation and cancer susceptibility, but (through TFF1) decreases antral proliferation and cancer susceptibility. The distinct effects of gastrin on proximal versus distal gastric cancers are consistent with the distinct epidemiology and behavior of tumors at these two anatomical sites, and emphasizes the importance of pathological descriptions clearly distinguishing the corpus and the antrum as separate tumor sites.

4.3. TFF1 Knockout Mice and Gp130 Mutant Mice

The human and mouse TFF1 (formerly known as pS2) proteins belong to the family of trefoil peptides, which are characterized by the presence of one to six cysteine-rich P domains. TFF1 proteins are normally expressed in the epithelial cells of the gastric mucosa, and are abnormally expressed in gastrointestinal diseases and various cancers. To elucidate the function of TFF1, Lefebvre et al. disrupted the mouse TFF1 gene by homologous recombination, generating TFF1−/− mice (F2 129/Svj mixed background) [144]. Mice deficient in TFF1 expression displayed hyperplastic gastric epithelium with markedly elongated gastric pits, and multifocal intraepithelial or intramucosal carcinomas were observed in 30% of mice [144]. A recent study has shown that loss of TFF1 leads to activation of IKK complex-regulated NF-κB transcription factors, resulting in enhanced NF-κB-mediated inflammatory responses during the progression to gastric tumorigenesis [145].

A reduction in TFF1 gene expression has been observed in about 50% of human distal stomach cancers, and promoter hypermethylation has also been found rather than mutation of the TFF1 gene [146,147,148]. A well-defined positive transcriptional regulator of TFF1 is the peptide hormone gastrin [149]. Gastrin inhibits TFF1 repression and thus suppresses MNU-induced antral gastric carcinogenesis [60]. In Helicobacter-infected human or mouse tissues, TFF1 was moderately epigenetically repressed, but much greater TFF2 repression was observed in stomach cancer [60]. Clyne et al. reported that H. pylori bound to the TFF1 dimer in vitro and that this interaction enables binding to gastric mucin, suggesting that TFF1 may act as a receptor for the organism [150,151]. However, in vivo evidence for direct H. pylori-TFF1 interaction has been lacking. Thus, further studies are needed to clarify the possible association between TFF1 and H. pylori.

While TFF1 is expressed predominantly in foveolar surface mucous or pit cells of the stomach, TFF2 is expressed in the deeper glandular epithelium in the distal stomach and the acini of Brunners glands in the duodenum [152,153,154]. Genetically engineered mice deficient in TFF2 show a minimal phenotype, with only a slight reduction in proliferation rates in the gastric mucosa [155] but H. pylori-infected TFF2-deficient mice develop more advanced premalignant lesions of atrophy, metaplasia, and dysplasia than WT mice [156]. Furthermore, the fundus of gp130F/F/TFF2−/− mice displayed glandular atrophy and metaplasia. These results suggest that TFF2 negatively regulates preneoplastic progression and subsequent tumor development in the stomach [157].

Gp130 is a common co-receptor for the cytokines IL-6 and IL-11. Mice with a mutation of the gp130 receptor (gp130F/F mice), which abrogates Src-homology tyrosine phosphatase 2 (SHP2)-Ras-ERK signaling following gp130 engagement, have a dramatic gastric phenotype. Gp130F/F mice progress rapidly to gastric neoplasia, with evidence of gastric adenomas by 3 months of age [158,159]. Interestingly, mutation of the gp130 receptor leads to downregulation of the TFF1 gene, and the phenotype of gp130F/F mice in many ways mimics that of TFF1−/− mice. The main cytokine driver of gp130 signaling in the stomach is IL-11, with IL-6 having little activity in the antral stomach [160,161]. IL-11 appears to promote chronic gastric inflammation and associated tumorigenesis mediated by excessive activation of STAT3 and STAT1 [162].

4.4. H/K-ATPase-IL-1β Transgenic Mice

Polymorphisms of the IL-1β that are predicted to increase IL-1β signaling have been shown to increase the risk of a number of human tumors, particularly gastric cancer [30]. IL-1β is a pleiotropic proinflammatory cytokine that has profound effects on inflammation and immunity, and is upregulated by H. pylori infection [30]. Tu et al. generated stomach-specific expression of human IL-1β in transgenic mice by using the murine H/K-ATPase promoter to direct expression of a constitutively active form of human IL-1β. H/K-ATPase-IL-1β transgenic mice (C57BL/6 background) exhibited spontaneous gastric inflammation and slow progression (over 1.5 years) to gastric atrophy, metaplasia and gastric cancer (Figure 3). In addition, infection of these mice with H. felis resulted in strong synergy and rapid progression (in <1 year) to cancer [163]. Thus, H/K-ATPase-IL-1β transgenic mice confirm the genetic findings in human patients that elevated expression of IL-1β represents a risk factor for gastric cancer, and that IL-1β can synergize with Helicobacter infection to drive cancer formation. In addition, it raises the possibility that IL-1β itself may represent a final common pathway for Helicobacter pathogenesis.

Cancers 05 00092 g003 1024
Figure 3. H/K-ATPase-IL-1β mouse: Inflammation, Metaplasia and Dysplasia. Low and high magnification images of the gastric corpus depicting prominent mucosal and submucosal granulocytic and lymphocytic inflammation with oxyntic loss, mucous metaplasia, foveolar and glandular hyperplasia, as well as dysplasia characterized by glandular architectural abnormalities such as misorientation, splitting, elongation, back to back formation, crowding and mild cellular atypia. (Bar: Left 100× or 160 μM, Right 400× or 40 μM).

Click here to enlarge figure

Figure 3. H/K-ATPase-IL-1β mouse: Inflammation, Metaplasia and Dysplasia. Low and high magnification images of the gastric corpus depicting prominent mucosal and submucosal granulocytic and lymphocytic inflammation with oxyntic loss, mucous metaplasia, foveolar and glandular hyperplasia, as well as dysplasia characterized by glandular architectural abnormalities such as misorientation, splitting, elongation, back to back formation, crowding and mild cellular atypia. (Bar: Left 100× or 160 μM, Right 400× or 40 μM).
Cancers 05 00092 g003 1024

Several molecular mechanisms of cancer development in IL-1β transgenic mice have been suggested. First, IL-1β stimulates through the IL-1 receptor the NF-κB pathway, which is strongly associated with a variety of cancers. NF-κB activation in inflammatory cells leads to increased production of IL-6, TNF-α, and other cytokines that have been associated with cancer development. Second, IL-1β of tumor cell origin has been shown in other studies to stimulate hematological alterations manifested by extensive accumulation in the spleen of Gr-1+CD11b+ immature myeloid cells that induce tumor-mediated immune suppression [164]. Indeed, IL-1β transgenic mice showed early recruitment of myeloid-derived suppressor cells (MDSCs) to the stomach [163]. Third, a recent study suggested that IL-1β suppresses Sonic Hedgehog (Shh) gene expression in parietal cells by inhibiting acid secretion and the release of cellular calcium, followed by gastric atrophy [165].

The H/K-ATPase-IL-1β mouse model of gastric cancer has been useful for elucidating the important contributions of stromal cells in the tumor microenvironments, including CAFs or inflammatory cells. Quante et al. showed that at least 20% of CAFs originate from bone marrow (BM) and are derived from mesenchymal stem cells (MSCs), and that MSC-derived CAFs which are recruited to the dysplastic stomach express IL-6, Wnt5a and BMP4, show DNA hypomethylation, and promote tumor growth [31]. Moreover, CAFs are involved in creation of a niche to sustain cancer progression in SDF-1-dependent manner [33]. Tu et al. analyzed the role of T cells in gastric carcinogenesis by using IL-1β the transgenic model, and reported that IFN-γ overexpression suppressed gastric carcinogenesis because helper T cell (Th) 1 and Th17 immune responses were inhibited by IFN-γ through Fas induction and apoptosis in CD4 T cells [32].

Taken together, the IL-1β transgenic mouse model is considered to be one of the best mouse models of gastric cancer reported to date. In combination with other strains of genetically engineered mice, it should be useful for clarifying further the early steps of cancer initiation and the critical interactions that take place between the epithelial and stromal components of the gastric mucosa.

4.5. K-ras Transgenic Mice

K-ras is one of the most commonly mutated proto-oncogene in a variety of human cancers [166]. While normally its activity is tightly regulated, somatic mutations occur that render its activity constitutive and thereby oncogenic [167]. Oncogenic activations of K-ras have been found in human gastric cancers, although they are not as common (0–18%) in both intestinal type and diffuse type gastric cancers as reported in other solid tumors, such as pancreatic or colorectal cancer [168]. While oncogenic K-ras leads to increased signaling through a number of proliferative (e.g., MAPK) pathways, it has also been strongly linked to the development of chronic inflammation and cancer [169]. In genetically engineered mouse models of pancreatic cancer based on PDX1-directed K-ras mutations, significant inflammatory and stromal responses correlate with cancer progression [170]. To analyze the function of oncogenic K-ras on the stomach cancer development in mice, the K19-promoter, which targets expression to the progenitor zone of the gastric neck/isthmus [171], was used to direct expression of K-ras-V12 mutant gene. K19-K-ras-V12 transgenic mice (F2 mixed C57BL/6 × DBA background) showed an early upregulation of chemokines such as CXCL1 and recruitment of bone marrow-derived inflammatory cells and fibroblasts, following by the gradual development of parietal cell loss, metaplasia and dysplasia, in a manner that closely resembled H. felis-induced gastric preneoplasia and carcinogenesis [171,172]. Thus, these data suggest that K-ras-dependent chronic inflammation, leading to the recruitment of bone marrow-derived cells that contribute to the stromal microenvironment, can initiate gastric carcinogenesis.

In a separate study, investigators introduced a conditional K-ras G12D mutation in the K19-positive lineage in adult mice by crossing K19-CreERT knock-in mice with LoxP-STOP-LoxP-KrasG12D mice. The phenotype of these mice included numerous hyperplasias, metaplasias and adenomas in the stomach as well as in the oral cavity, colon and lungs [173]. Another group bred UBC9-CreERT transgenic mice with LoxP-STOP-LoxP-KrasG12D mice in order to determine the effect in mice of widespread, systemic activation of K-ras [174]. Ubiquitous K-ras activation in mice had rapid and dramatic effects on both the forestomach and glandular stomach, and resulted in severe inflammation, hyperplasia, metaplasia, and activated progenitor cells, although neoplastic changes in other organs were not detected. These latter results suggest that, amongst all the tissues in which K-ras is activated, the stomach appears to be unusually susceptible to the effects of K-ras mutation at early time points, pointing to a crucial role of K-ras activation in initiation of gastric precancerous changes.

4.6. Wnt1 and COX-2 Transgenic Mice

Oncogenic activations of β-catenin have been found in about 20% of intestinal type gastric cancers, but not in diffuse type gastric cancers [168,175]. On the other hand, mutation of the Apc gene, while extremely common in colorectal cancer, is rarely seen in gastric cancer [168]. Nevertheless, familial adenomatous polyposis (FAP) due to germ-line mutations in the Apc gene, and characterized by the formation of thousands of colonic polyps and a high likelihood of colon carcinoma, is also associated with an increased risk of gastric polyps and cancer [176,177]. This suggests that Wnt signaling is likely to play a causal role in gastric cancer development. Thus, mice carrying a heterozygous Apc gene mutation (Apc1648) developed gastric dysplasia and polyposis in the antrum [178]. In addition, K19-Wnt1 transgenic mice were noted to have an increase of undifferentiated gastric epithelial cells along with the spontaneous development of small preneoplastic lesions in the gastric mucosa [179]. These data support a potential role for Wnt signaling in gastric carcinogenesis.

The COX-2/PGE2 pathway is also thought to play an important role in gastric tumorigenesis. Overexpression of cyclooxygenase 2 (COX-2) is frequently detected in gastric cancer [180]. COX-2 transgenic mice, where the human COX-2 cDNA was driven from the cytomegalovirus (CMV) promoter, showed an increase in MNU-induced gastric cancer development [55]. Treatment with celecoxib, a selective COX-2 inhibitor, reduced MNNG-induced gastric cancer incidence and growth in rats [181]. A combination of sulindac (a nonspecific COX inhibitor) and antimicrobial eradication prevent progression of gastric cancer in H. pylori-infected INS-GAS mice [182]. Finally, hyperplastic gastritis induced by H. pylori is associated with upregulated COX-2 expression, and gastric hyperplasia was significantly reduced by treatment with the selective COX-2 inhibitors [183,184,185].

In 2004, K19-C2mE transgenic mice were reported that simultaneously expressed both COX-2 and microsomal prostaglandin E synthase (PGES)-1 in the gastric epithelial cells. The transgenic mice developed hyperplastic lesions, metaplasia (SPEM), and tumorous growths in the glandular stomach with heavy macrophage infiltrations [186,187]. These findings suggest that an increased level of PGE2 enhances macrophage infiltration, thus contributing to gastric tumor development. When K19-Wnt1 mice were crossed with K19-C2mE to construct compound transgenic mice (K19-Wnt1/C2mE mice), the K19-Wnt1/C2mE mice developed mucous metaplasia followed by the spontaneous development of gastric adenocarcinoma [179]. The tumors consisted of dysplastic epithelial cells, which sometimes invaded the smooth muscle layers. These results clearly indicate that the simultaneous activation of the Wnt and PGE2 pathways can promote dysplastic gastric tumors through a metaplasia-carcinoma sequence. Moreover, ablation of CD44 (a gastric cancer stem cell marker [188]) in K19-Wnt1/C2mE mice (i.e., CD44−/−K19-Wnt1/C2mE mice) suppressed gastric tumor growth [189], suggesting that CD44-targeted therapy may impair tumor growth ability.

4.7. Other Mouse Models of Gastric Cancer

Other murine models have been reported that show a significant gastric neoplastic phenotype, and these will be discussed briefly. These have included manipulations of genes in the TGF-β/Smad pathway, RUNX3, MLH1/MSH2, p53, KLF4 and CDH1 (Table 2).

The TGF-β/Smad signaling pathway is commonly altered in gastric cancer [190,191,192], and TGF-β1 knockout mice (mixed C57BL/6/Sv/129 background) developed severe epithelial hyperplasia and metaplasia in the stomach [193]. Hahm et al. established TGF-β2 dominant-negative mice (mixed C57BL/6 × Sv/129 background) under the TFF1 promoter, and these mice showed a higher proliferation index and a higher incidence of gastric cancer with H. pylori infection [194]. Heterozygous Smad4 knockout mice (mixed C57BL/6 × Sv/129 background and C57BL/6 background) exhibited spontaneous gastric tumor development [195,196]. Interestingly, T-cell specific deletion of Smad4 induces gastric tumors, as well as colon, duodenal and oral cavity tumors, with induction of inflammatory cytokines [197,198].

Table Table 2. Mouse models of gastric cancer.

Click here to display table

Table 2. Mouse models of gastric cancer.
ModelIncidenceDurationLocationPhenotype
MNU<70%12 monthsAntrumAdenoCa, Dysplasia [11,47,48,49]
H. felis80%18 monthsSCJ/TransitionAdenoCa, Dysplasia, Metaplasia, Atrophy [21]
MNU + H. pylori80%12 monthsAntrumAdenoCa, Dysplasia, Metaplasia, Atrophy [110]
MNU + H. felis100%36 weeksAntrumAdenoCa, Dysplasia, Metaplasia, Atrophy [60]
CEA/SV40100%50 daysAntrumAdenoCa, Dysplasia, Invasion to submucosa and duodenum [24]
MMTV/Ad1282%(male)3–4 monthsSCJAdenoCa, AdenosquamousCa [26]
HPV-16100%246–352 daysAntrumCarcinoid, Metastasis to lymph node and liver [27]
MTH1−/−13%18 monthsAntrumAdenoCa, Dysplasia, Hyperplasia, Lung and liver tumors [199]
TFF1−/−30%5 monthsAntrumIntramucosal carcinoma, Hyperplasia, Activation of NF-kB [144,145]
Smad4+/−100%12–18 monthsCorpus/AntrumAdenoCa, Dysplasia, Hyperplasia, Duodenal tumor [195,196]
GB-Smad4F/F100%12–18 monthsAntrumDysplasia, Hyperplasia [197]
INS-GAS75%20 monthsCorpusAdenoCa, Dysplasia, Metaplasia, Atrophy, Synergized with H. felis [29]
GAS−/−60%12 monthsAntrumDysplasia, Metaplasia, Atrophy, Susceptible to MNU [60,143]
Gp130F/F100%6 monthsAntrumAdenoma, Decreased TFF1 expression [158,159]
IL-1β<70%12 monthsTransitionAdenoCa, Dysplasia, Metaplasia, Atrophy, Synergized with H. felis [163]
K19/K-ras37.5%16 monthsCorpusDysplasia, Metaplasia, Atrophy [172]
Wnt1/C2me100%20 weeksSCJAdenoCa, Dysplasia, Metaplasia, Attenuated by CD44 ablation [179,189]
CDH1+/− + MNU45.8%40 weeksAntrumSignet-ring cell Ca, Adenoma [56]
CDH1/p53100%12 monthsCorpusPoorly differentiated AdenoCa, Signet-ring cell Ca [200]
RUNX3−/− + MNU71%52 weeksCorpus/AntrumAdenoCa, Metaplasia, Hyperplasia [201]
Villin-KLF4F/F29%80 weeksAntrumAdenoma, Susceptible to MNU [57]

RUNX3 is a member of the RUNX gene family which regulates the Smad gene family transcription and TGF-β signaling. RUNX3 is frequently inactivated in gastric cancer by protein mislocalization [202]. RUNX3 knockout mice (F2 offspring) showed elongated gastric glands and increased proliferation in the gastric mucosa [203]. Ito et al. recently reported that RUNX3 knockout mice (Balb/c background) showed loss of chief cells and development of SPEM, and also displayed higher susceptibility to adenocarcinoma by treatment with MNU [201], supporting a role for RUNX3 as a tumor suppressor of gastric cancer.

Interestingly, alterations in p53 and DNA mismatch repair genes in mice have not produced dramatic gastric phenotypes, pointing to important differences between mice and humans. Alterations in DNA mismatch repair genes, such as MLH1 and MSH2, are associated with the Lynch syndrome (formerly known as hereditary non-polyposis colorectal cancer or HNPCC), which is characterized with increases in not only colorectal cancer but also ovarian, endometrium, liver, skin, brain, and gastric cancer [204]. However, mice lacking MLH1 or MSH2 do not develop gastric cancer, even with H. felis infection (Fox JG and Wang TC, unpublished data). Similarly, the p53 gene is the most commonly mutated tumor suppressor in a wide variety of human cancers. However, while H. felis-infected p53 hemizygous mice were reported to have a higher proliferative index and a higher gene mutation frequency than the infected control mice [205,206], they did not show increased progress to gastric cancer, although p53 heterozygous mice were more sensitive than WT counterparts to MNU [50,207]. However, a subsequent study demonstrated that the incidence of pre-neoplastic and invasive gastric carcinomas was decreased in p53 hemizygous mice [21], and an independent group reported that no differences in gastric apoptotic or proliferation indices between p53+/+ and p53+/– mice after infection with H. pylori SS1 strain [208]. These results point to the limitations of using constitutive p53 knockout mice in modeling gastric cancer in mice, given the likely distinct roles of p53 in epithelial cells and inflammatory cells.

Krüppel-like factor 4 (KLF4) is a potential tumor suppressor in patients with various cancers, including gastric cancer [209]. Disruption of Klf4 in mice using the Villin-Cre-mediated system, which targets not only the intestine but also antral stem/progenitor cells [57] induced spontaneous antral tumors. MNU treatment enhanced cancer development in these mice. Therefore, inactivation of Klf4 in Villin-positive gastric progenitor cells can lead to transformation of the gastric mucosa and tumorigenesis of the gastric antrum.

To date, most murine models that develop gastric cancer have shown similarities to the well differentiated, intestinal-type of gastric cancer, but not to the diffuse type of gastric cancer. In human gastric cancer, loss of expression of the CDH1 gene encoding for E-cadherin has frequently been detected [210], often due to promoter hypermethylation [168,211], particularly in diffuse-type lesions. Germline mutations of the CDH1 gene have been observed in hereditary diffuse type gastric cancer [212]. CDH1 knockout mice (C57BL/6 background) have been generated, and in the MNU carcinogenesis model, CDH1+/− mice developed signet ring cell carcinoma with a high tumor incidence rate [56]. Recently Shimada et al. generated conditional CDH1 and p53 double knockout mice under targeting by the H/K-ATPase promoter [200]. In these conditional double knockout mice, intramucosal and invasive cancers composed of signet ring cells were found from 6 to 9 months, while mice lacking only the CDH1 gene developed no cancers. These observations support the notion that CDH1 plays a critical role in especially diffuse type gastric cancer, but mouse gastric cancer development requires not only CDH1 loss but also an additional mutation or carcinogen exposure.

5. Models of Precancerous Change

H. pylori-associated gastric cancer in humans is preceded by a cascade of precancerous lesions, and cancer emerges following a number of discrete stages, including chronic gastritis, gastric atrophy, intestinal metaplasia, and dysplasia. Thus, in addition to mouse models of gastric cancer, there are a number of genetically engineered models that show decreased numbers of parietal cells, or gastric atrophy, along with metaplasia. In this section, we review briefly a number of models of atrophy and metaplasia that could be considered for use in experimental studies (Table 3). However, most of these models do not appear to progress to neoplasia, and most have not been examined for susceptibility to cancer in response to carcinogens.

Table Table 3. Mouse models of precancerous changes.

Click here to display table

Table 3. Mouse models of precancerous changes.
ModelDurationPhenotype
H.pylori (SS-1)6–9 monthsAtrophy, SPEM [20]
TGF-α transgenic3 monthsAtrophy [122,213]
H/K-ATPase/DT28–80 daysAtrophy [214]
H/K-ATPase/TkGanciclovir treatmentAtrophy [215]
H/K-ATPase-α−/−10 weeksAtrophy [216]
H/K-ATPase-β−/−17 daysAtrophy [217,218]
NHE2−/−17 daysAtrophy [219]
Car9−/−4 weeksAtrophy [220]
CCK2R−/−18 weeksAtrophy [221,222]
H/K-ATPase/Shh−/−3–8 monthsPit cell hyperplasia, loss of parietal cell function [223]
DMP-7777–14 daysAtrophy, SPEM [224,225]
L-6357 daysAtrophy, SPEM [226]
Cdx2 transgenic120 daysIntestinal metaplasia [227,228]
Cdx1 transgenic120 daysIntestinal metaplasia [229]

5.1. Models of Gastric Atrophy

There are a number of genetically engineered mouse models, which exhibit parietal cell loss, i.e., gastric atrophy. Indeed, one strategy to achieve more rapid progression to gastric cancer is to ablate parietal cells, which appear to protect the homeostasis of the stomach in part through acid secretion. As mentioned above, MT-TGF-α transgenic mice show a form of atrophic gastritis, with loss of parietal cells along with foveolar hyperplasia [122,213]. Using the promoter of the β-subunit of the H/K-ATPase gene driving diphtheria toxin or herpes simplex 1 thymidine kinase, researchers were able to partially ablate parietal cells [214,215]. Interestingly, with loss of mature parietal cells in both of these models, there was concomitant loss of chief or zymogenic cells, along with an increase in progenitor cells. Thus, accumulating data indicate that the parietal cell itself or its secreted products plays a critical role on maintaining gastric gland homeostasis and controlling the development of cancerous changes.

In many of these mouse models with impaired parietal cell function, hypochlorhydria leads to hypergastrinemia, which then induces foveolar hyperplasia. Thus, mice with a disrupted H/K-ATPase β-subunit gene exhibit abnormal parietal cell morphology, achlorhydria, hypergastrinemia, and hypertrophied gastric mucosa [216,217]. When crossed with GAS−/− mice, gastric hypertrophy in the H/K-ATPase-β-deficient mice disappeared, confirming that this phenotype is largely hypergastrinemia-dependent [218]. Similarly, targeted disruption of the Na+/H+ exchanger isoform 2 (NHE2) gene or carbonic anhydrase gene have also been reported to induce parietal cell loss [219,220]. Transgenic mice with parietal cell-specific deletion of Sonic Hedgehog (Shh) (H/K-ATPase-Cre/Shh−/−) also developed gastric hypochlorhydria, hypergastrinemia, and a phenotype that resembled foveolar hyperplasia with hyperproliferation of surface mucous cells [223]. Therefore, Shh may also function as a gastric morphogen, regulating gastric epithelial cell function and differentiation. In contrast, mice deficient in gastrin or its receptor cholecystokinin-B exhibit impaired acid secretion and reduced parietal cell numbers, but do not show foveolar hyperplasia [141,221,222,230]. As noted above, gastrin knockout mice are more susceptible to mouse induced antral carcinogenesis, but most other mouse models have not been tested in carcinogenesis trials.

5.2. Models of Metaplasia

Recently, it has become clear that there are two distinct types of metaplasia in the stomach that precede and are associated with gastric cancer [231]. (1) Spasmolytic polypeptide-expressing metaplasia (SPEM), also known as pseudopyloric metaplasia, is characterized by the presence of TFF2- and MUC6-immunoreactive cells in the gastric fundus with morphological characteristics similar to deep antral gland cells or Brunner’s gland cells. (2) The other is classical intestinal metaplasia (IM), which is characterized by the presence of cells with the morphology of goblet cells and expression of MUC2 and TFF3. Both types of metaplasia are Alcian blue-positive. For many years, IM was thought to be a direct precursor of gastric cancer; however, while the association of intestinal-type cancers with chronic H. pylori infection and oxyntic atrophy in human is well accepted, little evidence directly links intestinal metaplasia with dysplastic transformation [232]. Indeed, many investigators have come to the conclusion that SPEM is more likely to be the relevant precursor to gastric adenocarcinoma [233].

In most of the mouse models progressing to dysplasia described above, including mouse models of H. felis infection and transgenic mouse models (such as INS-GAS and H/K-ATPase-IL-1β mice), which demonstrate severe parietal cell loss, the fundic mucosa is replaced with a mucous cell metaplasia which was shown to be TFF2-expressing SPEM. Importantly, in these mouse models which progress to cancer, SPEM represents the only observed metaplasia, with no goblet cell IM being present. In addition, a short term model of parietal cell ablation has been described, using the neutrophil elastase inhibitor, DMP-777, which was shown to be a parietal cell-specific protonophore. DMP-777 treatment has allowed the examination of SPEM induction after acute oxyntic atrophy in the absence of significant inflammatory infiltrate. Mice or rats treated for 3 days with DMP-777 demonstrate a rapid loss of parietal cells [224,225]. The acute oxyntic atrophy is followed by SPEM in the fundus after 7–10 days. A structurally related β-lactam compound L-635, which retains potent parietal cell protonophore activity, but does not have any significant activity against neutrophil elastase, also induces gastric atrophy. In contrast with DMP-777 treatment, submucosal and intramucosal inflammatory infiltration was observed, and L-635 caused a more rapid and marked mucous cell TFF2-positive metaplasia [226]. These results indicated that a combination of parietal cell loss and inflammation could potentiate the development of SPEM.

Transgenic mice expressing the intestine-specific homeobox gene, Cdx2, under H/K-ATPase or Foxa3 promoter showed the disappearance of parietal cells and the replacement by classical IM [227,228]. Moreover, mice overexpressing Cdx1, another intestine-specific homeobox gene, also developed IM [229]. However, no further progression to gastric carcinogenesis was observed in these transgenic mice, consistent with the notion that IM may not be the primary precursor of gastric cancer. However, the effect of Helicobacter infection on the gastric phenotype of these mice has not been assessed. Thus, further studies are needed to clarify the precise relationship between classical intestinal metaplasia and malignant transformation.

6. Conclusions and Future Perspectives

Numerous mouse models with interesting gastric phenotypes are now available for studies of gastric carcinogenesis. These include transgenic mice (e.g., INS-GAS, H/K-ATPase-IL-1β, K19-Wnt1/C2mE), knockout mice (GAS−/−, Tff1−/−, gp130F/F), Helicobacter infection (H. felis, H. pylori) and carcinogen (MNU) models. These models have defined potential roles for gender, diet, bacterial flora, inflammatory cytokines, T helper immune response, acid secretion, virulence, and colonization properties of H. pylori strains and host genetic background. Reasonable models are now available for studies of early stage pathogenesis and cancer prevention.

The mouse stomach consists of four different parts: forestomach, cardia, corpus, and antrum. Some models have been described in which forestomach tumor, i.e., squamous cell carcinoma, is induced with a carcinogen or by genetic alterations [26,46,47]. These models are not useful for investigating the mechanism of human gastric cancer, as humans do not have a forestomach and gastric squamous cell carcinoma is very rare. While there has been no model that resembles human cardia cancer, a variety of corpus and antral cancer models have been reported as described above. However, in order to select appropriate mouse models of gastric cancer, investigators need to consider the histopathology, the cell type of origin and the geographic distribution of the resultant cancer. Sometimes, a given physiological stimuli will show a different phenotype between the corpus and antrum, such as seen in gastrin transgenic and knockout mice [29,60,143].

Unfortunately, genetic models of metastatic gastric cancer similar to those developed for pancreatic cancer, comprising two or three mutations targeted to specific cell lineages, are not available. These models could facilitate preclinical studies and the testing of newer therapeutics. The major limitations in the development of these models have been the weak and scattered activity of promoters used in the stomach and the lack of stomach specific promoters that target antral progenitors but are not expressed elsewhere (Table 4). K19-Cre and Foxa3-Cre constructs, for example, are expressed in the stomach and can be used as a model for the analysis of gastric cancer, but these promoter constructs are also expressed in the intestine, colon and pancreas, as well as other tissues [105,172]. Recent lineage tracing studies revealed several stem/progenitor markers of gastrointestinal tissue, including Lgr5, Bmi1, Hopx, Lrig, Sox2, and Sox9 [234,235,236,237,238,239]. Among them, Lgr5, Lrig, and Sox2 have been reported to be expressed in the mouse stomach. Lgr5 positive cells are likely to be stem cells in the gastric antrum [234,240], and can be used for mutagenic targeting to the distal stomach, but Lgr5 is also widely expressed in the intestine and elsewhere making targeted stomach mutations impractical. Similarly, Lrig and Sox2 are expressed in the intestine and other organs as well as the stomach. Villin-Cre constructs also can target antral glands, but are also expressed in whole intestine [241]. On the other hand, stomach specific promoters such as the H/K-ATPase promoter are not ideal since they target more mature parietal cells, which are unlikely to be the precursor lineage of distal gastric cancers.

Table Table 4. Promoters for establishing gene expression in the stomach.

Click here to display table

Table 4. Promoters for establishing gene expression in the stomach.
GeneLocationLineage tracing in the stomach
TFF1Surface of stomach (pit cell area)
TFF2Isthmus of corpus & base of antrumGive rise to parietal, mucous neck, and chief cells [242]
H/K-ATPaseCorpus (parietal cell)Give rise to all gastric lineages of the corpus glands with Notch activation [243]
Foxa3Whole stomach, other organ from endoderm
K19Whole stomach, intestine, colon, etc.
Lgr5Cardia, Antrum, intestine, colon, etc.Give rise to all major cell types in the cardia, antrum and transition zone [240]
Sox2Corpus, Antrum, Esophagus, Forestomach, etc.Give rise to all major cell types in the corpus and the antrum [236]
Mist1Corpus (chief cell), Brunner gland, pancreasGive rise to chief cell and drug-induced SPEM [226]
VillinAntrum, intestine, colonGive rise to all gastric lineages of the antral glands with IFN-γ treatment [241]

One potential candidate for a gastric targeting vector might be TFF1, which shows specific expression in foveolar cells of the stomach. To date, one study has reported the use of the TFF1 promoter to disrupt TGF-β2 specifically in the stomach [194]. Further studies using TFF1-specific gene engineering should be considered. Both TFF2-CreERT and Mist1-Cre mice are available. In the corpus, TFF2 and Mist1 are known to be potent progenitor cell lineages. Mist1-expressing cells in the stomach give rise to SPEM after stimulation [226]. TFF2mRNA-expressing cells are localized to the isthmus and are progenitors for mucus neck, parietal and zymogenic cells, but not for pit or enterochromaffin-like cell lineages [242]. TFF2 is also expressed in the base of the antral glands, suggesting that TFF2 could be a potent candidate promoter vector for targeting the stomach. In order to obtain stomach-specific gene control, other stomach-specific stem/progenitor markers should be explored by using emerging lineage tracing technique in vivo and stem cell culture methods in vitro.

Recent exome sequencing or GWAS studies have clarified significant gene mutations in human gastric cancer, such as PSCA, PLCE1, FAT4 and ARID1A [244,245,246,247]. Newer mouse models which contain these gene alterations should be useful for investigating the function of these genes. In turn, comprehensive analysis of genetic and epigenetic changes of mouse gastric cancer should also be helpful for identifying additional genetic changes or epigenetic modifications which are not covered by exome sequencing or GWAS studies focusing on human gastric cancer.

In summary, several mouse models of gastric cancer are available, which have distinct mechanisms, as well as different tumor phenotypes such as time course, locations, and pathology. Researchers are thus able to use appropriate mouse models for their studies and are commensurate with their rationale and hypothesis. Newly emerging research methods, including lineage tracing or genome-wide comprehensive analysis, and also by examining non-epithelial targets, should prove helpful for understanding both the cause and ultimately the cure of gastric cancer.

References

  1. Ferlay, J.; Shin, H.R.; Bray, F.; Forman, D.; Mathers, C.; Parkin, D.M. Estimates of worldwide burden of cancer in 2008: GLOBOCAN 2008. Int. J. Cancer 2010, 127, 2893–2917. [Google Scholar] [CrossRef]
  2. Jemal, A.; Bray, F.; Center, M.M.; Ferlay, J.; Ward, E.; Forman, D. Global cancer statistics. CA Cancer J. Clin. 2011, 61, 69–90. [Google Scholar] [CrossRef]
  3. Kawase, S.; Ishikura, H. Female-predominant occurrence of spontaneous gastric adenocarcinoma in cotton rats. Lab. Anim. Sci. 1995, 45, 244–248. [Google Scholar]
  4. Waldum, H.L.; Rørvik, H.; Falkmer, S.; Kawase, S. Neuroendocrine (ECL cell) differentiation of spontaneous gastric carcinomas of cotton rats (Sigmodon hispidus). Lab. Anim. Sci. 1999, 49, 241–247. [Google Scholar]
  5. Cui, G.; Qvigstad, G.; Falkmer, S.; Sandvik, A.K.; Kawase, S.; Waldum, H.L. Spontaneous ECLomas in cotton rats (Sigmodon hispidus): Tumours occurring in hypoacidic/hypergastrinaemic animals with normal parietal cells. Carcinogenesis 2000, 21, 23–27. [Google Scholar] [CrossRef]
  6. Koga, T.; Takahashi, K.; Sato, K.; Kikuchi, I.; Okazaki, Y.; Miura, T.; Katsuta, M.; Narita, T. The effect of colonisation by Helicobacter pylori in Praomys (Mastomys) natalensis on the incidence of carcinoids. J. Med. Microbiol. 2002, 51, 777–785. [Google Scholar]
  7. Kumazawa, H.; Takagi, H.; Sudo, K.; Nakamura, W.; Hosoda, S. Adenocarcinoma and carcinoid developing spontaneously in the stomach of mutant strains of Mastomys natalensis. Virchows Arch. A Pathol. Anat. Histopathol. 1989, 416, 141–151. [Google Scholar] [CrossRef]
  8. Correa, P.; Haenszel, W.; Cuello, C.; Tannenbaum, S.; Archer, M. A model for gastric cancer epidemiology. Lancet 1975, 2, 58–60. [Google Scholar]
  9. Saito, T.; Sugimura, T. Biochemical studies on carcinogenesis in the glandular stomach of rats with N-methyl-N'-nitro-N-nitrosoguanidine. Gann 1973, 64, 373–381. [Google Scholar]
  10. Sugimura, T.; Fujimura, S. Tumour production in glandular stomach of rat by N-methyl-N'-nitro-N-nitrosoguanidine. Nature 1967, 216, 943–944. [Google Scholar] [CrossRef]
  11. Tatematsu, M.; Ogawa, K.; Hoshiya, T.; Shichino, Y.; Kato, T.; Imaida, K.; Ito, N. Induction of adenocarcinomas in the glandular stomach of BALB/c mice treated with N-methyl-N-nitrosourea. Jpn. J. Cancer Res. 1992, 83, 915–918. [Google Scholar] [CrossRef]
  12. Marshall, B.J.; Warren, J.R. Unidentified curved bacilli in the stomach of patients with gastritis and peptic ulceration. Lancet 1984, 1, 1311–1315. [Google Scholar] [CrossRef]
  13. Forman, D.; Newell, D.G.; Fullerton, F.; Yarnell, J.W.; Stacey, A.R.; Wald, N.; Sitas, F. Association between infection with Helicobacter pylori and risk of gastric cancer: Evidence from a prospective investigation. BMJ 1991, 302, 1302–1305. [Google Scholar] [CrossRef]
  14. Nomura, A.; Stemmermann, G.N.; Chyou, P.H.; Kato, I.; Perez-Perez, G.I.; Blaser, M.J. Helicobacter pylori infection and gastric carcinoma among Japanese Americans in Hawaii. N. Engl. J. Med. 1991, 325, 1132–1136. [Google Scholar] [CrossRef]
  15. Parsonnet, J.; Friedman, G.D.; Vandersteen, D.P.; Chang, Y.; Vogelman, J.H.; Orentreich, N.; Sibley, R.K. Helicobacter pylori infection and the risk of gastric carcinoma. N. Engl. J. Med. 1991, 325, 1127–1131. [Google Scholar] [CrossRef]
  16. Uemura, N.; Okamoto, S.; Yamamoto, S.; Matsumura, N.; Yamaguchi, S.; Yamakido, M.; Taniyama, K.; Sasaki, N.; Schlemper, R.J. Helicobacter pylori infection and the development of gastric cancer. N. Engl. J. Med. 2001, 345, 784–789. [Google Scholar] [CrossRef]
  17. Fox, J.G.; Wang, T.C. Helicobacter pylori—Not a good bug after all! N. Engl. J. Med. 2001, 345, 829–832. [Google Scholar] [CrossRef]
  18. Lee, A.; Hazell, S.L.; O’Rourke, J.; Kouprach, S. Isolation of a spiral-shaped bacterium from the cat stomach. Infect. Immun. 1988, 56, 2843–2850. [Google Scholar]
  19. Rogers, A.B.; Taylor, N.S.; Whary, M.T.; Stefanich, E.D.; Wang, T.C.; Fox, J.G. Helicobacter pylori but not high salt induces gastric intraepithelial neoplasia in B6129 mice. Cancer Res. 2005, 65, 10709–10715. [Google Scholar] [CrossRef]
  20. Lee, A.; O'Rourke, J.; de Ungria, M.C.; Robertson, B.; Daskalopoulos, G.; Dixon, M.F. A standardized mouse model of Helicobacter pylori infection: Introducing the Sydney strain. Gastroenterology 1997, 112, 1386–1397. [Google Scholar] [CrossRef]
  21. Fox, J.G.; Sheppard, B.J.; Dangler, C.A.; Whary, M.T.; Ihrig, M.; Wang, T.C. Germ-line p53-targeted disruption inhibits helicobacter-induced premalignant lesions and invasive gastric carcinoma through down-regulation of Th1 proinflammatory responses. Cancer Res. 2002, 62, 696–702. [Google Scholar]
  22. Fanning, E.; Knippers, R. Structure and function of simian virus 40 large tumor antigen. Annu. Rev. Biochem. 1992, 61, 55–85. [Google Scholar] [CrossRef]
  23. Montag, A.G.; Oka, T.; Baek, K.H.; Choi, C.S.; Jay, G.; Agarwal, K. Tumors in hepatobiliary tract and pancreatic islet tissues of transgenic mice harboring gastrin simian virus 40 large tumor antigen fusion gene. Proc. Natl. Acad. Sci. USA 1993, 90, 6696–6700. [Google Scholar]
  24. Thompson, J.; Epting, T.; Schwarzkopf, G.; Singhofen, A.; Eades-Perner, A.M.; van der Putten, H.; Zimmermann, W. A transgenic mouse line that develops early-onset invasive gastric carcinoma provides a model for carcinoembryonic antigen-targeted tumor therapy. Int. J. Cancer 2000, 86, 863–869. [Google Scholar] [CrossRef]
  25. Li, Q.; Karam, S.M.; Gordon, J.I. Simian virus 40 T antigen-induced amplification of pre-parietal cells in transgenic mice. Effects on other gastric epithelial cell lineages and evidence for a p53-independent apoptotic mechanism that operates in a committed progenitor. J. Biol. Chem. 1995, 270, 15777–15788. [Google Scholar]
  26. Koike, K.; Hinrichs, S.H.; Isselbacher, K.J.; Jay, G. Transgenic mouse model for human gastric carcinoma. Proc. Natl. Acad. Sci. USA 1989, 86, 5615–5619. [Google Scholar] [CrossRef]
  27. Searle, P.F.; Thomas, D.P.; Faulkner, K.B.; Tinsley, J.M. Stomach cancer in transgenic mice expressing human papillomavirus type 16 early region genes from a keratin promoter. J. Gen. Virol. 1994, 75, 1125–1137. [Google Scholar] [CrossRef]
  28. Correa, P. Human gastric carcinogenesis: A multistep and multifactorial process—First American Cancer Society Award Lecture on Cancer Epidemiology and Prevention. Cancer Res. 1992, 52, 6735–6740. [Google Scholar]
  29. Wang, T.C.; Dangler, C.A.; Chen, D.; Goldenring, J.R.; Koh, T.; Raychowdhury, R.; Coffey, R.J.; Ito, S.; Varro, A.; Dockray, G.J.; et al. Synergistic interaction between hypergastrinemia and Helicobacter infection in a mouse model of gastric cancer. Gastroenterology 2000, 118, 36–47. [Google Scholar]
  30. El-Omar, E.M.; Carrington, M.; Chow, W.H.; McColl, K.E.; Bream, J.H.; Young, H.A.; Herrera, J.; Lissowska, J.; Yuan, C.C.; Rothman, N.; et al. The role of interleukin-1 polymorphisms in the pathogenesis of gastric cancer. Nature 2001, 412, 99. [Google Scholar]
  31. Quante, M.; Tu, S.P.; Tomita, H.; Gonda, T.; Wang, S.S.; Takashi, S.; Baik, G.H.; Shibata, W.; Diprete, B.; Betz, K.S.; et al. Bone marrow-derived myofibroblasts contribute to the mesenchymal stem cell niche and promote tumor growth. Cancer Cell 2011, 19, 257–272. [Google Scholar] [CrossRef]
  32. Tu, S.P.; Quante, M.; Bhagat, G.; Takaishi, S.; Cui, G.; Yang, X.D.; Muthuplani, S.; Shibata, W.; Fox, J.G.; Pritchard, D.M.; et al. IFN-γ inhibits gastric carcinogenesis by inducing epithelial cell autophagy and T-cell apoptosis. Cancer Res. 2011, 71, 4247–4259. [Google Scholar] [CrossRef]
  33. Shibata, W.; Ariyama, H.; Westphalen, C.B.; Worthley, D.L.; Muthupalani, S.; Asfaha, S.; Dubeykovskaya, Z.; Quante, M.; Fox, J.G.; Wang, T.C. Stromal cell-derived factor-1 overexpression induces gastric dysplasia through expansion of stromal myofibroblasts and epithelial progenitors. Gut 2012, 62, 192–200. [Google Scholar]
  34. Asfaha, S.; Dubeykovskiy, A.N.; Tomita, H.; Yang, X.; Stokes, S.; Shibata, W.; Friedman, R.A.; Ariyama, H.; Dubeykovskaya, Z.A.; Muthupalani, S.; et al. Mice that Express Human Interleukin-8 Have Increased Mobilization of Immature Myeloid Cells, which Exacerbates Inflammation and Accelerates Colon Carcinogenesis. Gastroenterology 2012, 144, 155–166. [Google Scholar]
  35. Rogers, A.B.; Fox, J.G. Inflammation and Cancer. I. Rodent models of infectious gastrointestinal and liver cancer. Am. J. Physiol. Gastrointest. Liver Physiol. 2004, 286, G361–G366. [Google Scholar] [CrossRef]
  36. Lemke, L.B.; Ge, Z.; Whary, M.T.; Feng, Y.; Rogers, A.B.; Muthupalani, S.; Fox, J.G. Concurrent Helicobacter bilis infection in C57BL/6 mice attenuates proinflammatory H. pylori-induced gastric pathology. Infect. Immun. 2009, 77, 2147–2158. [Google Scholar] [CrossRef]
  37. Ge, Z.; Feng, Y.; Muthupalani, S.; Eurell, L.L.; Taylor, N.S.; Whary, M.T.; Fox, J.G. Coinfection with Enterohepatic Helicobacter species can ameliorate or promote Helicobacter pylori-induced gastric pathology in C57BL/6 mice. Infect. Immun. 2011, 79, 3861–3871. [Google Scholar] [CrossRef]
  38. Schoental, R. Carcinogenic activity of N-methyl-N-nitroso-N'-nitroguanidine. Nature 1966, 209, 726–727. [Google Scholar] [CrossRef]
  39. Ohgaki, H.; Kawachi, T.; Matsukura, N.; Morino, K.; Miyamoto, M.; Sugimura, T. Genetic control of susceptibility of rats to gastric carcinoma. Cancer Res. 1983, 43, 3663–3667. [Google Scholar]
  40. Tatematsu, M.; Yamamoto, M.; Shimizu, N.; Yoshikawa, A.; Fukami, H.; Kaminishi, M.; Oohara, T.; Sugiyama, A.; Ikeno, T. Induction of glandular stomach cancers in Helicobacter pylori-sensitive Mongolian gerbils treated with N-methyl-N-nitrosourea and N-methyl-N'-nitro-N-nitrosoguanidine in drinking water. Jpn. J. Cancer Res. 1998, 89, 97–104. [Google Scholar] [CrossRef]
  41. Takahashi, M.; Kokubo, T.; Furukawa, F.; Kurokawa, Y.; Tatematsu, M.; Hayashi, Y. Effect of high salt diet on rat gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine. Gann 1983, 74, 28–34. [Google Scholar]
  42. Tatematsu, M.; Takahashi, M.; Fukushima, S.; Hananouchi, M.; Shirai, T. Effects in rats of sodium chloride on experimental gastric cancers induced by N-methyl-N-nitro-N-nitrosoguanidine or 4-nitroquinoline-1-oxide. J. Natl. Cancer Inst. 1975, 55, 101–106. [Google Scholar]
  43. Tatsuta, M.; Iishi, H.; Baba, M.; Uehara, H.; Nakaizumi, A.; Taniguchi, H. Enhancing effects of calcium-deficient diet on gastric carcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats. Jpn. J. Cancer Res. 1993, 84, 945–950. [Google Scholar] [CrossRef]
  44. Wada, S.; Hirose, M.; Shichino, Y.; Ozaki, K.; Hoshiya, T.; Kato, K.; Shirai, T. Effects of catechol, sodium chloride and ethanol either alone or in combination on gastric carcinogenesis in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine. Cancer Lett. 1998, 123, 127–134. [Google Scholar] [CrossRef]
  45. Uedo, N.; Tatsuta, M.; Iishi, H.; Baba, M.; Yano, H.; Ishihara, R.; Higashino, K.; Ishiguro, S. Enhancement by interleukin-1 beta of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats: A possible mechanism for Helicobacter pylori-associated gastric carcinogenesis. Cancer Lett. 2003, 198, 161–168. [Google Scholar] [CrossRef]
  46. Danon, S.J.; Eaton, K.A. The role of gastric Helicobacter and N-methyl-N'-nitro-N-nitrosoguanidine in carcinogenesis of mice. Helicobacter 1998, 3, 260–268. [Google Scholar] [CrossRef]
  47. Tatematsu, M.; Yamamoto, M.; Iwata, H.; Fukami, H.; Yuasa, H.; Tezuka, N.; Masui, T.; Nakanishi, H. Induction of glandular stomach cancers in C3H mice treated with N-methyl-N-nitrosourea in the drinking water. Jpn. J. Cancer Res. 1993, 84, 1258–1264. [Google Scholar] [CrossRef]
  48. Yamachika, T.; Nakanishi, H.; Inada, K.; Tsukamoto, T.; Shimizu, N.; Kobayashi, K.; Fukushima, S.; Tatematsu, M. N-methyl-N-nitrosourea concentration-dependent, rather than total intake-dependent, induction of adenocarcinomas in the glandular stomach of BALB/c mice. Jpn. J. Cancer Res. 1998, 89, 385–391. [Google Scholar] [CrossRef]
  49. Yamamoto, M.; Furihata, C.; Ogiu, T.; Tsukamoto, T.; Inada, K.; Hirano, K.; Tatematsu, M. Independent variation in susceptibilities of six different mouse strains to induction of pepsinogen-altered pyloric glands and gastric tumor intestinalization by N-methyl-N-nitrosourea. Cancer Lett. 2002, 179, 121–132. [Google Scholar] [CrossRef]
  50. Yamamoto, M.; Tsukamoto, T.; Sakai, H.; Shirai, N.; Ohgaki, H.; Furihata, C.; Donehower, L.A.; Yoshida, K.; Tatematsu, M. p53 knockout mice (−/−) are more susceptible than (+/−) or (+/+) mice to N-methyl-N-nitrosourea stomach carcinogenesis. Carcinogenesis 2000, 21, 1891–1897. [Google Scholar] [CrossRef]
  51. Sakamoto, K.; Hikiba, Y.; Nakagawa, H.; Hayakawa, Y.; Yanai, A.; Akanuma, M.; Ogura, K.; Hirata, Y.; Kaestner, K.H.; Omata, M.; et al. Inhibitor of kappaB Kinase Beta Regulates Gastric Carcinogenesis via Interleukin-1alpha Expression. Gastroenterology 2010, 139, 226–238. [Google Scholar] [CrossRef]
  52. Shibata, W.; Maeda, S.; Hikiba, Y.; Yanai, A.; Sakamoto, K.; Nakagawa, H.; Ogura, K.; Karin, M.; Omata, M. c-Jun NH2-terminal kinase 1 is a critical regulator for the development of gastric cancer in mice. Cancer Res. 2008, 68, 5031–5039. [Google Scholar]
  53. Hayakawa, Y.; Hirata, Y.; Nakagawa, H.; Sakamoto, K.; Hikiba, Y.; Kinoshita, H.; Nakata, W.; Takahashi, R.; Tateishi, K.; Tada, M.; et al. Apoptosis signal-regulating kinase 1 and cyclin D1 compose a positive feedback loop contributing to tumor growth in gastric cancer. Proc. Natl. Acad. Sci. USA 2011, 108, 780–785. [Google Scholar]
  54. Takasu, S.; Tsukamoto, T.; Cao, X.Y.; Toyoda, T.; Hirata, A.; Ban, H.; Yamamoto, M.; Sakai, H.; Yanai, T.; Masegi, T.; et al. Roles of cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression and beta-catenin activation in gastric carcinogenesis in N-methyl-N-nitrosourea-treated K19-C2mE transgenic mice. Cancer Sci. 2008, 99, 2356–2364. [Google Scholar] [CrossRef]
  55. Leung, W.K.; Wu, K.C.; Wong, C.Y.; Cheng, A.S.; Ching, A.K.; Chan, A.W.; Chong, W.W.; Go, M.Y.; Yu, J.; To, K.F.; et al. Transgenic cyclooxygenase-2 expression and high salt enhanced susceptibility to chemical-induced gastric cancer development in mice. Carcinogenesis 2008, 29, 1648–1654. [Google Scholar] [CrossRef]
  56. Humar, B.; Blair, V.; Charlton, A.; More, H.; Martin, I.; Guilford, P. E-cadherin deficiency initiates gastric signet-ring cell carcinoma in mice and man. Cancer Res. 2009, 69, 2050–2056. [Google Scholar] [CrossRef]
  57. Li, Q.; Jia, Z.; Wang, L.; Kong, X.; Guo, K.; Tan, D.; Le, X.; Wei, D.; Huang, S.; Mishra, L.; et al. Disruption of Klf4 in villin-positive gastric progenitor cells promotes formation and progression of tumors of the antrum in mice. Gastroenterology 2012, 142, 531–542. [Google Scholar] [CrossRef]
  58. Tsukamoto, T.; Mizoshita, T.; Tatematsu, M. Animal models of stomach carcinogenesis. Toxicol. Pathol. 2007, 35, 636–648. [Google Scholar] [CrossRef]
  59. Boffa, L.C.; Bolognesi, C. Methylating agents: Their target amino acids in nuclear proteins. Carcinogenesis 1985, 6, 1399–1401. [Google Scholar] [CrossRef]
  60. Tomita, H.; Takaishi, S.; Menheniott, T.R.; Yang, X.; Shibata, W.; Jin, G.; Betz, K.S.; Kawakami, K.; Minamoto, T.; Tomasetto, C.; et al. Inhibition of gastric carcinogenesis by the hormone gastrin is mediated by suppression of TFF1 epigenetic silencing. Gastroenterology 2011, 140, 879–891. [Google Scholar] [CrossRef]
  61. Cao, X.; Tsukamoto, T.; Nozaki, K.; Tanaka, H.; Shimizu, N.; Kaminishi, M.; Kumagai, T.; Tatematsu, M. Earlier Helicobacter pylori infection increases the risk for the N-methyl-N-nitrosourea-induced stomach carcinogenesis in Mongolian gerbils. Jpn. J. Cancer Res. 2002, 93, 1293–1298. [Google Scholar] [CrossRef]
  62. Maruta, F.; Sugiyama, A.; Ishida, K.; Ikeno, T.; Murakami, M.; Kawasaki, S.; Ota, H.; Tatematsu, M.; Katsuyama, T. Timing of N-methyl-N-nitrosourea administration affects gastric carcinogenesis in Mongolian gerbils infected with Helicobacter pylori. Cancer Lett. 2000, 160, 99–105. [Google Scholar] [CrossRef]
  63. Fox, J.G.; Wishnok, J.S.; Murphy, J.C.; Tannenbaum, S.R.; Correa, P. MNNG-induced gastric carcinoma in ferrets infected with Helicobacter mustelae. Carcinogenesis 1993, 14, 1957–1961. [Google Scholar] [CrossRef]
  64. Fox, J.G. Gastric disease in ferrets: Effects of Helicobacter mustelae, nitrosamines and reconstructive gastric surgery. Eur. J. Gastroenterol. Hepatol. 1994, 6, S57–S65. [Google Scholar]
  65. Fox, J.G.; Dangler, C.A.; Sager, W.; Borkowski, R.; Gliatto, J.M. Helicobacter mustelae-associated gastric adenocarcinoma in ferrets (Mustela putorius furo). Vet. Pathol. 1997, 34, 225–229. [Google Scholar] [CrossRef]
  66. Fox, J.G.; Correa, P.; Taylor, N.S.; Lee, A.; Otto, G.; Murphy, J.C.; Rose, R. Helicobacter mustelae-associated gastritis in ferrets. An animal model of Helicobacter pylori gastritis in humans. Gastroenterology 1990, 99, 352–361. [Google Scholar]
  67. Wirth, H.P.; Beins, M.H.; Yang, M.; Tham, K.T.; Blaser, M.J. Experimental infection of Mongolian gerbils with wild-type and mutant Helicobacter pylori strains. Infect. Immun. 1998, 66, 4856–4866. [Google Scholar]
  68. Ogura, K.; Maeda, S.; Nakao, M.; Watanabe, T.; Tada, M.; Kyutoku, T.; Yoshida, H.; Shiratori, Y.; Omata, M. Virulence factors of Helicobacter pylori responsible for gastric diseases in Mongolian gerbil. J. Exp. Med. 2000, 192, 1601–1610. [Google Scholar] [CrossRef]
  69. Israel, D.A.; Salama, N.; Arnold, C.N.; Moss, S.F.; Ando, T.; Wirth, H.P.; Tham, K.T.; Camorlinga, M.; Blaser, M.J.; Falkow, S.; et al. Helicobacter pylori strain-specific differences in genetic content, identified by microarray, influence host inflammatory responses. J. Clin. Invest. 2001, 107, 611–620. [Google Scholar] [CrossRef]
  70. Marchetti, M.; Rappuoli, R. Isogenic mutants of the cag pathogenicity island of Helicobacter pylori in the mouse model of infection: Effects on colonization efficiency. Microbiology 2002, 148, 1447–1456. [Google Scholar]
  71. Ehlers, S.; Warrelmann, M.; Hahn, H. In search of an animal model for experimental Campylobacter pylori infection: Administration of Campylobacter pylori to rodents. Zentralbl. Bakteriol. Mikrobiol. Hyg. A 1988, 268, 341–346. [Google Scholar]
  72. Cantorna, M.T.; Balish, E. Inability of human clinical strains of Helicobacter pylori to colonize the alimentary tract of germfree rodents. Can. J. Microbiol. 1990, 36, 237–241. [Google Scholar] [CrossRef]
  73. Lee, A.; Fox, J.G.; Otto, G.; Murphy, J. A small animal model of human Helicobacter pylori active chronic gastritis. Gastroenterology 1990, 99, 1315–1323. [Google Scholar]
  74. Lee, A.; Chen, M.; Coltro, N.; O'Rourke, J.; Hazell, S.; Hu, P.; Li, Y. Long term infection of the gastric mucosa with Helicobacter species does induce atrophic gastritis in an animal model of Helicobacter pylori infection. Zentralbl Bakteriol 1993, 280, 38–50. [Google Scholar] [CrossRef]
  75. Sakagami, T.; Dixon, M.; O'Rourke, J.; Howlett, R.; Alderuccio, F.; Vella, J.; Shimoyama, T.; Lee, A. Atrophic gastric changes in both Helicobacter felis and Helicobacter pylori infected mice are host dependent and separate from antral gastritis. Gut 1996, 39, 639–648. [Google Scholar] [CrossRef]
  76. Wang, T.C.; Goldenring, J.R.; Dangler, C.; Ito, S.; Mueller, A.; Jeon, W.K.; Koh, T.J.; Fox, J.G. Mice lacking secretory phospholipase A2 show altered apoptosis and differentiation with Helicobacter felis infection. Gastroenterology 1998, 114, 675–689. [Google Scholar]
  77. Stoicov, C.; Saffari, R.; Cai, X.; Hasyagar, C.; Houghton, J. Molecular biology of gastric cancer: Helicobacter infection and gastric adenocarcinoma: Bacterial and host factors responsible for altered growth signaling. Gene 2004, 341, 1–17. [Google Scholar] [CrossRef]
  78. Houghton, J.; Wang, T.C. Helicobacter pylori and gastric cancer: A new paradigm for inflammation-associated epithelial cancers. Gastroenterology 2005, 128, 1567–1578. [Google Scholar] [CrossRef]
  79. Cai, X.; Carlson, J.; Stoicov, C.; Li, H.; Wang, T.C.; Houghton, J. Helicobacter felis eradication restores normal architecture and inhibits gastric cancer progression in C57BL/6 mice. Gastroenterology 2005, 128, 1937–1952. [Google Scholar] [CrossRef]
  80. Lee, C.W.; Rickman, B.; Rogers, A.B.; Ge, Z.; Wang, T.C.; Fox, J.G. Helicobacter pylori eradication prevents progression of gastric cancer in hypergastrinemic INS-GAS mice. Cancer Res. 2008, 68, 3540–3548. [Google Scholar] [CrossRef]
  81. Sepulveda, A.R.; Coelho, L.G. Helicobacter pylori and gastric malignancies. Helicobacter 2002, 7, 37–42. [Google Scholar] [CrossRef]
  82. Ley, C.; Mohar, A.; Guarner, J.; Herrera-Goepfert, R.; Figueroa, L.S.; Halperin, D.; Johnstone, I.; Parsonnet, J. Helicobacter pylori eradication and gastric preneoplastic conditions: A randomized, double-blind, placebo-controlled trial. Cancer Epidemiol. Biomarkers Prev. 2004, 13, 4–10. [Google Scholar] [CrossRef]
  83. Lee, C.W.; Rickman, B.; Rogers, A.B.; Muthupalani, S.; Takaishi, S.; Yang, P.; Wang, T.C.; Fox, J.G. Combination of sulindac and antimicrobial eradication of Helicobacter pylori prevents progression of gastric cancer in hypergastrinemic INS-GAS mice. Cancer Res. 2009, 69, 8166–8174. [Google Scholar] [CrossRef]
  84. Wang, X.; Willén, R.; Svensson, M.; Ljungh, A.; Wadström, T. Two-year follow-up of Helicobacter pylori infection in C57BL/6 and Balb/cA mice. APMIS 2003, 111, 514–522. [Google Scholar] [CrossRef]
  85. Fox, J.G.; Wang, T.C.; Rogers, A.B.; Poutahidis, T.; Ge, Z.; Taylor, N.; Dangler, C.A.; Israel, D.A.; Krishna, U.; Gaus, K.; et al. Host and microbial constituents influence Helicobacter pylori-induced cancer in a murine model of hypergastrinemia. Gastroenterology 2003, 124, 1879–1890. [Google Scholar]
  86. Higashi, H.; Tsutsumi, R.; Muto, S.; Sugiyama, T.; Azuma, T.; Asaka, M.; Hatakeyama, M. SHP-2 tyrosine phosphatase as an intracellular target of Helicobacter pylori CagA protein. Science 2002, 295, 683–686. [Google Scholar] [CrossRef]
  87. Maeda, S.; Yoshida, H.; Ogura, K.; Mitsuno, Y.; Hirata, Y.; Yamaji, Y.; Akanuma, M.; Shiratori, Y.; Omata, M. H. pylori activates NF-kappaB through a signaling pathway involving IkappaB kinases, NF-kappaB-inducing kinase, TRAF2, and TRAF6 in gastric cancer cells. Gastroenterology 2000, 119, 97–108. [Google Scholar] [CrossRef]
  88. Mitsuno, Y.; Yoshida, H.; Maeda, S.; Ogura, K.; Hirata, Y.; Kawabe, T.; Shiratori, Y.; Omata, M. Helicobacter pylori induced transactivation of SRE and AP-1 through the ERK signalling pathway in gastric cancer cells. Gut 2001, 49, 18–22. [Google Scholar] [CrossRef]
  89. Viala, J.; Chaput, C.; Boneca, I.G.; Cardona, A.; Girardin, S.E.; Moran, A.P.; Athman, R.; Memet, S.; Huerre, M.R.; Coyle, A.J.; et al. Nod1 responds to peptidoglycan delivered by the Helicobacter pylori cag pathogenicity island. Nat. Immunol. 2004, 5, 1166–1174. [Google Scholar] [CrossRef]
  90. Crabtree, J.E.; Ferrero, R.L.; Kusters, J.G. The mouse colonizing Helicobacter pylori strain SS1 may lack a functional cag pathogenicity island. Helicobacter 2002, 7, 139–140. [Google Scholar] [CrossRef]
  91. Ohnishi, N.; Yuasa, H.; Tanaka, S.; Sawa, H.; Miura, M.; Matsui, A.; Higashi, H.; Musashi, M.; Iwabuchi, K.; Suzuki, M.; et al. Transgenic expression of Helicobacter pylori CagA induces gastrointestinal and hematopoietic neoplasms in mouse. Proc. Natl. Acad. Sci. USA 2008, 105, 1003–1008. [Google Scholar]
  92. Arnold, I.C.; Lee, J.Y.; Amieva, M.R.; Roers, A.; Flavell, R.A.; Sparwasser, T.; Müller, A. Tolerance rather than immunity protects from Helicobacter pylori-induced gastric preneoplasia. Gastroenterology 2011, 140, 199–209. [Google Scholar] [CrossRef]
  93. Mohammadi, M.; Redline, R.; Nedrud, J.; Czinn, S. Role of the host in pathogenesis of Helicobacter-associated gastritis: H. felis infection of inbred and congenic mouse strains. Infect. Immun. 1996, 64, 238–245. [Google Scholar]
  94. Ottlecz, A.; Romero, J.J.; Lichtenberger, L.M. Helicobacter infection and phospholipase A2 enzymes: Effect of Helicobacter felis-infection on the expression and activity of sPLA2 enzymes in mouse stomach. Mol. Cell. Biochem. 2001, 221, 71–77. [Google Scholar] [CrossRef]
  95. Roth, K.A.; Kapadia, S.B.; Martin, S.M.; Lorenz, R.G. Cellular immune responses are essential for the development of Helicobacter felis-associated gastric pathology. J. Immunol. 1999, 163, 1490–1497. [Google Scholar]
  96. Eaton, K.A.; Mefford, M.; Thevenot, T. The role of T cell subsets and cytokines in the pathogenesis of Helicobacter pylori gastritis in mice. J. Immunol. 2001, 166, 7456–7461. [Google Scholar]
  97. Smythies, L.E.; Waites, K.B.; Lindsey, J.R.; Harris, P.R.; Ghiara, P.; Smith, P.D. Helicobacter pylori-induced mucosal inflammation is Th1 mediated and exacerbated in IL-4, but not IFN-gamma, gene-deficient mice. J. Immunol. 2000, 165, 1022–1029. [Google Scholar]
  98. Ismail, H.F.; Fick, P.; Zhang, J.; Lynch, R.G.; Berg, D.J. Depletion of neutrophils in IL-10−/− mice delays clearance of gastric Helicobacter infection and decreases the Th1 immune response to Helicobacter. J. Immunol. 2003, 170, 3782–3789. [Google Scholar]
  99. Berg, D.J.; Lynch, N.A.; Lynch, R.G.; Lauricella, D.M. Rapid development of severe hyperplastic gastritis with gastric epithelial dedifferentiation in Helicobacter felis-infected IL-10−/− mice. Am. J. Pathol. 1998, 152, 1377–1386. [Google Scholar]
  100. Ohana, M.; Okazaki, K.; Oshima, C.; Andra’s, D.; Nishi, T.; Uchida, K.; Uose, S.; Nakase, H.; Matsushima, Y.; Chiba, T. A critical role for IL-7R signaling in the development of Helicobacter felis-induced gastritis in mice. Gastroenterology 2001, 121, 329–336. [Google Scholar] [CrossRef]
  101. Sayi, A.; Kohler, E.; Hitzler, I.; Arnold, I.; Schwendener, R.; Rehrauer, H.; Müller, A. The CD4+ T cell-mediated IFN-gamma response to Helicobacter infection is essential for clearance and determines gastric cancer risk. J. Immunol. 2009, 182, 7085–7101. [Google Scholar]
  102. Sayi, A.; Kohler, E.; Toller, I.M.; Flavell, R.A.; Müller, W.; Roers, A.; Müller, A. TLR-2-activated B cells suppress Helicobacter-induced preneoplastic gastric immunopathology by inducing T regulatory-1 cells. J. Immunol. 2011, 186, 878–890. [Google Scholar] [CrossRef]
  103. Jones, N.L.; Day, A.S.; Jennings, H.; Shannon, P.T.; Galindo-Mata, E.; Sherman, P.M. Enhanced disease severity in Helicobacter pylori-infected mice deficient in Fas signaling. Infect. Immun. 2002, 70, 2591–2597. [Google Scholar] [CrossRef]
  104. Houghton, J.M.; Bloch, L.M.; Goldstein, M.; von Hagen, S.; Korah, R.M. In vivo disruption of the fas pathway abrogates gastric growth alterations secondary to Helicobacter infection. J. Infect. Dis. 2000, 182, 856–864. [Google Scholar] [CrossRef]
  105. Shibata, W.; Takaishi, S.; Muthupalani, S.; Pritchard, D.M.; Whary, M.T.; Rogers, A.B.; Fox, J.G.; Betz, K.S.; Kaestner, K.H.; Karin, M.; et al. Conditional deletion of IkappaB-kinase-beta accelerates helicobacter-dependent gastric apoptosis, proliferation, and preneoplasia. Gastroenterology 2010, 138, 1022–1034.e10. [Google Scholar]
  106. Fox, J.G.; Rogers, A.B.; Ihrig, M.; Taylor, N.S.; Whary, M.T.; Dockray, G.; Varro, A.; Wang, T.C. Helicobacter pylori-associated gastric cancer in INS-GAS mice is gender specific. Cancer Res. 2003, 63, 942–950. [Google Scholar]
  107. Sheh, A.; Lee, C.W.; Masumura, K.; Rickman, B.H.; Nohmi, T.; Wogan, G.N.; Fox, J.G.; Schauer, D.B. Mutagenic potency of Helicobacter pylori in the gastric mucosa of mice is determined by sex and duration of infection. Proc. Natl. Acad. Sci. USA 2010, 107, 15217–15222. [Google Scholar]
  108. Crabtree, J.E.; Court, M.; Aboshkiwa, M.A.; Jeremy, A.H.; Dixon, M.F.; Robinson, P.A. Gastric mucosal cytokine and epithelial cell responses to Helicobacter pylori infection in Mongolian gerbils. J. Pathol. 2004, 202, 197–207. [Google Scholar] [CrossRef]
  109. Shimizu, N.; Kaminishi, M.; Tatematsu, M.; Tsuji, E.; Yoshikawa, A.; Yamaguchi, H.; Aoki, F.; Oohara, T. Helicobacter pylori promotes development of pepsinogen-altered pyloric glands, a preneoplastic lesion of glandular stomach of BALB/c mice pretreated with N-methyl-N-nitrosourea. Cancer Lett. 1998, 123, 63–69. [Google Scholar] [CrossRef]
  110. Han, S.U.; Kim, Y.B.; Joo, H.J.; Hahm, K.B.; Lee, W.H.; Cho, Y.K.; Kim, D.Y.; Kim, M.W. Helicobacter pylori infection promotes gastric carcinogenesis in a mice model. J. Gastroenterol. Hepatol. 2002, 17, 253–261. [Google Scholar] [CrossRef]
  111. Fox, J.G.; Dangler, C.A.; Taylor, N.S.; King, A.; Koh, T.J.; Wang, T.C. High-salt diet induces gastric epithelial hyperplasia and parietal cell loss, and enhances Helicobacter pylori colonization in C57BL/6 mice. Cancer Res. 1999, 59, 4823–4828. [Google Scholar]
  112. Fox, J.G.; Beck, P.; Dangler, C.A.; Whary, M.T.; Wang, T.C.; Shi, H.N.; Nagler-Anderson, C. Concurrent enteric helminth infection modulates inflammation and gastric immune responses and reduces helicobacter-induced gastric atrophy. Nat. Med. 2000, 6, 536–542. [Google Scholar] [CrossRef]
  113. Lofgren, J.L.; Whary, M.T.; Ge, Z.; Muthupalani, S.; Taylor, N.S.; Mobley, M.; Potter, A.; Varro, A.; Eibach, D.; Suerbaum, S.; et al. Lack of commensal flora in Helicobacter pylori-infected INS-GAS mice reduces gastritis and delays intraepithelial neoplasia. Gastroenterology 2011, 140, 210–220. [Google Scholar] [CrossRef]
  114. Houghton, J.; Stoicov, C.; Nomura, S.; Rogers, A.B.; Carlson, J.; Li, H.; Cai, X.; Fox, J.G.; Goldenring, J.R.; Wang, T.C. Gastric cancer originating from bone marrow-derived cells. Science 2004, 306, 1568–1571. [Google Scholar]
  115. Varon, C.; Dubus, P.; Mazurier, F.; Asencio, C.; Chambonnier, L.; Ferrand, J.; Giese, A.; Senant-Dugot, N.; Carlotti, M.; Mégraud, F. Helicobacter pylori infection recruits bone marrow-derived cells that participate in gastric preneoplasia in mice. Gastroenterology 2012, 142, 281–291. [Google Scholar] [CrossRef]
  116. Worthley, D.L.; Giraud, A.S.; Wang, T.C. Stromal fibroblasts in digestive cancer. Cancer Microenviron 2010, 3, 117–125. [Google Scholar] [CrossRef]
  117. Rindi, G.; Bordi, C.; Rappel, S.; La Rosa, S.; Stolte, M.; Solcia, E. Gastric carcinoids and neuroendocrine carcinomas: Pathogenesis, pathology, and behavior. World J. Surg. 1996, 20, 168–172. [Google Scholar] [CrossRef]
  118. Ferrand, A.; Wang, T.C. Gastrin and cancer: A review. Cancer Lett. 2006, 238, 15–29. [Google Scholar] [CrossRef]
  119. Wang, T.C.; Brand, S.J. Function and regulation of gastrin in transgenic mice: A review. Yale J. Biol. Med. 1992, 65, 705–740. [Google Scholar]
  120. Wang, T.C.; Bonner-Weir, S.; Oates, P.S.; Chulak, M.; Simon, B.; Merlino, G.T.; Schmidt, E.V.; Brand, S.J. Pancreatic gastrin stimulates islet differentiation of transforming growth factor alpha-induced ductular precursor cells. J. Clin. Invest. 1993, 92, 1349–1356. [Google Scholar] [CrossRef]
  121. Miyazaki, Y.; Shinomura, Y.; Tsutsui, S.; Zushi, S.; Higashimoto, Y.; Kanayama, S.; Higashiyama, S.; Taniguchi, N.; Matsuzawa, Y. Gastrin induces heparin-binding epidermal growth factor-like growth factor in rat gastric epithelial cells transfected with gastrin receptor. Gastroenterology 1999, 116, 78–89. [Google Scholar] [CrossRef]
  122. Goldenring, J.R.; Ray, G.S.; Soroka, C.J.; Smith, J.; Modlin, I.M.; Meise, K.S.; Coffey, R.J. Overexpression of transforming growth factor-alpha alters differentiation of gastric cell lineages. Dig. Dis. Sci. 1996, 41, 773–784. [Google Scholar] [CrossRef]
  123. Takaishi, S.; Tu, S.; Dubeykovskaya, Z.A.; Whary, M.T.; Muthupalani, S.; Rickman, B.H.; Rogers, A.B.; Lertkowit, N.; Varro, A.; Fox, J.G.; et al. Gastrin is an essential cofactor for helicobacter-associated gastric corpus carcinogenesis in C57BL/6 mice. Am. J. Pathol. 2009, 175, 365–375. [Google Scholar] [CrossRef]
  124. Cui, G.; Koh, T.J.; Chen, D.; Zhao, C.M.; Takaishi, S.; Dockray, G.J.; Varro, A.; Rogers, A.B.; Fox, J.G.; Wang, T.C. Overexpression of glycine-extended gastrin inhibits parietal cell loss and atrophy in the mouse stomach. Cancer Res. 2004, 64, 8160–8166. [Google Scholar]
  125. Takaishi, S.; Wang, T.C. Gene expression profiling in a mouse model of Helicobacter-induced gastric cancer. Cancer Sci. 2007, 98, 284–293. [Google Scholar] [CrossRef]
  126. Tu, S.; Chi, A.L.; Lim, S.; Cui, G.; Dubeykovskaya, Z.; Ai, W.; Fleming, J.V.; Takaishi, S.; Wang, T.C. Gastrin regulates the TFF2 promoter through gastrin-responsive cis-acting elements and multiple signaling pathways. Am. J. Physiol. Gastrointest. Liver Physiol. 2007, 292, G1726–G1737. [Google Scholar] [CrossRef]
  127. Steele, I.A.; Dimaline, R.; Pritchard, D.M.; Peek, R.M.; Wang, T.C.; Dockray, G.J.; Varro, A. Helicobacter and gastrin stimulate Reg1 expression in gastric epithelial cells through distinct promoter elements. Am. J. Physiol. Gastrointest. Liver Physiol. 2007, 293, G347–G354. [Google Scholar] [CrossRef]
  128. Yin, Y.; Grabowska, A.M.; Clarke, P.A.; Whelband, E.; Robinson, K.; Argent, R.H.; Tobias, A.; Kumari, R.; Atherton, J.C.; Watson, S.A. Helicobacter pylori potentiates epithelial:mesenchymal transition in gastric cancer: Links to soluble HB-EGF, gastrin and matrix metalloproteinase-7. Gut 2010, 59, 1037–1045. [Google Scholar]
  129. Takaishi, S.; Cui, G.; Frederick, D.M.; Carlson, J.E.; Houghton, J.; Varro, A.; Dockray, G.J.; Ge, Z.; Whary, M.T.; Rogers, A.B.; et al. Synergistic inhibitory effects of gastrin and histamine receptor antagonists on Helicobacter-induced gastric cancer. Gastroenterology 2005, 128, 1965–1983. [Google Scholar] [CrossRef]
  130. Okabe, S.; Kodama, Y.; Cao, H.; Johannessen, H.; Zhao, C.M.; Wang, T.C.; Takahashi, R.; Chen, D. Topical application of acetic acid in cytoreduction of gastric cancer. A technical report using mouse model. J. Gastroenterol. Hepatol. 2012, 27, 40–48. [Google Scholar] [CrossRef]
  131. Ohtani, M.; García, A.; Rogers, A.B.; Ge, Z.; Taylor, N.S.; Xu, S.; Watanabe, K.; Marini, R.P.; Whary, M.T.; Wang, T.C.; et al. Protective role of 17 beta-estradiol against the development of Helicobacter pylori-induced gastric cancer in INS-GAS mice. Carcinogenesis 2007, 28, 2597–2604. [Google Scholar] [CrossRef]
  132. Ohtani, M.; Ge, Z.; García, A.; Rogers, A.B.; Muthupalani, S.; Taylor, N.S.; Xu, S.; Watanabe, K.; Feng, Y.; Marini, R.P.; et al. 17 β-estradiol suppresses Helicobacter pylori-induced gastric pathology in male hypergastrinemic INS-GAS mice. Carcinogenesis 2011, 32, 1244–1250. [Google Scholar] [CrossRef]
  133. Sheh, A.; Ge, Z.; Parry, N.M.; Muthupalani, S.; Rager, J.E.; Raczynski, A.R.; Mobley, M.W.; McCabe, A.F.; Fry, R.C.; Wang, T.C.; et al. 17β-estradiol and tamoxifen prevent gastric cancer by modulating leukocyte recruitment and oncogenic pathways in Helicobacter pylori-infected INS-GAS male mice. Cancer Prev. Res. (Phila.) 2011, 4, 1426–1435. [Google Scholar] [CrossRef]
  134. Stenström, B.; Zhao, C.M.; Rogers, A.B.; Nilsson, H.O.; Sturegård, E.; Lundgren, S.; Fox, J.G.; Wang, T.C.; Wadström, T.M.; Chen, D. Swedish moist snuff accelerates gastric cancer development in Helicobacter pylori-infected wild-type and gastrin transgenic mice. Carcinogenesis 2007, 28, 2041–2046. [Google Scholar] [CrossRef]
  135. Cui, G.; Takaishi, S.; Ai, W.; Betz, K.S.; Florholmen, J.; Koh, T.J.; Houghton, J.; Pritchard, D.M.; Wang, T.C. Gastrin-induced apoptosis contributes to carcinogenesis in the stomach. Lab. Invest. 2006, 86, 1037–1051. [Google Scholar] [CrossRef]
  136. Przemeck, S.M.; Varro, A.; Berry, D.; Steele, I.; Wang, T.C.; Dockray, G.J.; Pritchard, D.M. Hypergastrinemia increases gastric epithelial susceptibility to apoptosis. Regul. Pept. 2008, 146, 147–156. [Google Scholar] [CrossRef]
  137. Singh, P.; Velasco, M.; Given, R.; Wargovich, M.; Varro, A.; Wang, T.C. Mice overexpressing progastrin are predisposed for developing aberrant colonic crypt foci in response to AOM. Am. J. Physiol. Gastrointest. Liver Physiol. 2000, 278, G390–G399. [Google Scholar]
  138. Singh, P.; Velasco, M.; Given, R.; Varro, A.; Wang, T.C. Progastrin expression predisposes mice to colon carcinomas and adenomas in response to a chemical carcinogen. Gastroenterology 2000, 119, 162–171. [Google Scholar] [CrossRef]
  139. Ottewell, P.D.; Duckworth, C.A.; Varro, A.; Dimaline, R.; Wang, T.C.; Watson, A.J.; Dockray, G.J.; Pritchard, D.M. Gastrin increases murine intestinal crypt regeneration following injury. Gastroenterology 2006, 130, 1169–1180. [Google Scholar] [CrossRef]
  140. Thomson, M.J.; Pritchard, D.M.; Boxall, S.A.; Abuderman, A.A.; Williams, J.M.; Varro, A.; Crabtree, J.E. Gastric Helicobacter Infection Induces Iron Deficiency in the INS-GAS Mouse. PLoS One 2012, 7, e50194. [Google Scholar]
  141. Koh, T.J.; Goldenring, J.R.; Ito, S.; Mashimo, H.; Kopin, A.S.; Varro, A.; Dockray, G.J.; Wang, T.C. Gastrin deficiency results in altered gastric differentiation and decreased colonic proliferation in mice. Gastroenterology 1997, 113, 1015–1025. [Google Scholar] [CrossRef]
  142. Zavros, Y.; Rieder, G.; Ferguson, A.; Samuelson, L.C.; Merchant, J.L. Genetic or chemical hypochlorhydria is associated with inflammation that modulates parietal and G-cell populations in mice. Gastroenterology 2002, 122, 119–133. [Google Scholar] [CrossRef]
  143. Zavros, Y.; Eaton, K.A.; Kang, W.; Rathinavelu, S.; Katukuri, V.; Kao, J.Y.; Samuelson, L.C.; Merchant, J.L. Chronic gastritis in the hypochlorhydric gastrin-deficient mouse progresses to adenocarcinoma. Oncogene 2005, 24, 2354–2366. [Google Scholar]
  144. Lefebvre, O.; Chenard, M.P.; Masson, R.; Linares, J.; Dierich, A.; LeMeur, M.; Wendling, C.; Tomasetto, C.; Chambon, P.; Rio, M.C. Gastric mucosa abnormalities and tumorigenesis in mice lacking the pS2 trefoil protein. Science 1996, 274, 259–262. [Google Scholar] [CrossRef]
  145. Soutto, M.; Belkhiri, A.; Piazuelo, M.B.; Schneider, B.G.; Peng, D.; Jiang, A.; Washington, M.K.; Kokoye, Y.; Crowe, S.E.; Zaika, A.; et al. Loss of TFF1 is associated with activation of NF-κB-mediated inflammation and gastric neoplasia in mice and humans. J. Clin. Invest. 2011, 121, 1753–1767. [Google Scholar] [CrossRef]
  146. Beckler, A.D.; Roche, J.K.; Harper, J.C.; Petroni, G.; Frierson, H.F.; Moskaluk, C.A.; El-Rifai, W.; Powell, S.M. Decreased abundance of trefoil factor 1 transcript in the majority of gastric carcinomas. Cancer 2003, 98, 2184–2191. [Google Scholar] [CrossRef]
  147. Fujimoto, J.; Yasui, W.; Tahara, H.; Tahara, E.; Kudo, Y.; Yokozaki, H. DNA hypermethylation at the pS2 promoter region is associated with early stage of stomach carcinogenesis. Cancer Lett. 2000, 149, 125–134. [Google Scholar] [CrossRef]
  148. Carvalho, R.; Kayademir, T.; Soares, P.; Canedo, P.; Sousa, S.; Oliveira, C.; Leistenschneider, P.; Seruca, R.; Gött, P.; Blin, N.; et al. Loss of heterozygosity and promoter methylation, but not mutation, may underlie loss of TFF1 in gastric carcinoma. Lab. Invest. 2002, 82, 1319–1326. [Google Scholar]
  149. Khan, Z.E.; Wang, T.C.; Cui, G.; Chi, A.L.; Dimaline, R. Transcriptional regulation of the human trefoil factor, TFF1, by gastrin. Gastroenterology 2003, 125, 510–521. [Google Scholar] [CrossRef]
  150. Clyne, M.; Dillon, P.; Daly, S.; O'Kennedy, R.; May, F.E.; Westley, B.R.; Drumm, B. Helicobacter pylori interacts with the human single-domain trefoil protein TFF1. Proc. Natl. Acad. Sci. USA 2004, 101, 7409–7414. [Google Scholar]
  151. Reeves, E.P.; Ali, T.; Leonard, P.; Hearty, S.; O'Kennedy, R.; May, F.E.; Westley, B.R.; Josenhans, C.; Rust, M.; Suerbaum, S.; et al. Helicobacter pylori lipopolysaccharide interacts with TFF1 in a pH-dependent manner. Gastroenterology 2008, 135, 2043–2054.e2. [Google Scholar] [CrossRef]
  152. Rio, M.C.; Bellocq, J.P.; Daniel, J.Y.; Tomasetto, C.; Lathe, R.; Chenard, M.P.; Batzenschlager, A.; Chambon, P. Breast cancer-associated pS2 protein: Synthesis and secretion by normal stomach mucosa. Science 1988, 241, 705–708. [Google Scholar]
  153. Hanby, A.M.; Poulsom, R.; Singh, S.; Elia, G.; Jeffery, R.E.; Wright, N.A. Spasmolytic polypeptide is a major antral peptide: Distribution of the trefoil peptides human spasmolytic polypeptide and pS2 in the stomach. Gastroenterology 1993, 105, 1110–1116. [Google Scholar]
  154. Hanby, A.M.; Poulsom, R.; Elia, G.; Singh, S.; Longcroft, J.M.; Wright, N.A. The expression of the trefoil peptides pS2 and human spasmolytic polypeptide (hSP) in “gastric metaplasia” of the proximal duodenum: Implications for the nature of “gastric metaplasia”. J. Pathol. 1993, 169, 355–360. [Google Scholar] [CrossRef]
  155. Farrell, J.J.; Taupin, D.; Koh, T.J.; Chen, D.; Zhao, C.M.; Podolsky, D.K.; Wang, T.C. TFF2/SP-deficient mice show decreased gastric proliferation, increased acid secretion, and increased susceptibility to NSAID injury. J. Clin. Invest. 2002, 109, 193–204. [Google Scholar]
  156. Fox, J.G.; Rogers, A.B.; Whary, M.T.; Ge, Z.; Ohtani, M.; Jones, E.K.; Wang, T.C. Accelerated progression of gastritis to dysplasia in the pyloric antrum of TFF2−/− C57BL6 × Sv129 Helicobacter pylori-infected mice. Am. J. Pathol. 2007, 171, 1520–1528. [Google Scholar] [CrossRef]
  157. Peterson, A.J.; Menheniott, T.R.; O'Connor, L.; Walduck, A.K.; Fox, J.G.; Kawakami, K.; Minamoto, T.; Ong, E.K.; Wang, T.C.; Judd, L.M.; et al. Helicobacter pylori infection promotes methylation and silencing of trefoil factor 2, leading to gastric tumor development in mice and humans. Gastroenterology 2010, 139, 2005–2017. [Google Scholar] [CrossRef]
  158. Jenkins, B.J.; Grail, D.; Nheu, T.; Najdovska, M.; Wang, B.; Waring, P.; Inglese, M.; McLoughlin, R.M.; Jones, S.A.; Topley, N.; et al. Hyperactivation of Stat3 in gp130 mutant mice promotes gastric hyperproliferation and desensitizes TGF-beta signaling. Nat. Med. 2005, 11, 845–852. [Google Scholar]
  159. Tebbutt, N.C.; Giraud, A.S.; Inglese, M.; Jenkins, B.; Waring, P.; Clay, F.J.; Malki, S.; Alderman, B.M.; Grail, D.; Hollande, F.; et al. Reciprocal regulation of gastrointestinal homeostasis by SHP2 and STAT-mediated trefoil gene activation in gp130 mutant mice. Nat. Med. 2002, 8, 1089–1097. [Google Scholar]
  160. Jackson, C.B.; Judd, L.M.; Menheniott, T.R.; Kronborg, I.; Dow, C.; Yeomans, N.D.; Boussioutas, A.; Robb, L.; Giraud, A.S. Augmented gp130-mediated cytokine signalling accompanies human gastric cancer progression. J. Pathol. 2007, 213, 140–151. [Google Scholar] [CrossRef]
  161. Judd, L.M.; Ulaganathan, M.; Howlett, M.; Giraud, A.S. Cytokine signalling by gp130 regulates gastric mucosal healing after ulceration and, indirectly, antral tumour progression. J. Pathol. 2009, 217, 552–562. [Google Scholar] [CrossRef]
  162. Ernst, M.; Najdovska, M.; Grail, D.; Lundgren-May, T.; Buchert, M.; Tye, H.; Matthews, V.B.; Armes, J.; Bhathal, P.S.; Hughes, N.R.; et al. STAT3 and STAT1 mediate IL-11-dependent and inflammation-associated gastric tumorigenesis in gp130 receptor mutant mice. J. Clin. Invest. 2008, 118, 1727–1738. [Google Scholar]
  163. Tu, S.; Bhagat, G.; Cui, G.; Takaishi, S.; Kurt-Jones, E.A.; Rickman, B.; Betz, K.S.; Penz-Oesterreicher, M.; Bjorkdahl, O.; Fox, J.G.; et al. Overexpression of interleukin-1beta induces gastric inflammation and cancer and mobilizes myeloid-derived suppressor cells in mice. Cancer Cell 2008, 14, 408–419. [Google Scholar] [CrossRef]
  164. Song, X.; Krelin, Y.; Dvorkin, T.; Bjorkdahl, O.; Segal, S.; Dinarello, C.A.; Voronov, E.; Apte, R.N. CD11b+/Gr-1+ immature myeloid cells mediate suppression of T cells in mice bearing tumors of IL-1beta-secreting cells. J. Immunol. 2005, 175, 8200–8208. [Google Scholar]
  165. Waghray, M.; Zavros, Y.; Saqui-Salces, M.; El-Zaatari, M.; Alamelumangapuram, C.B.; Todisco, A.; Eaton, K.A.; Merchant, J.L. Interleukin-1beta promotes gastric atrophy through suppression of Sonic Hedgehog. Gastroenterology 2010, 138, 562–572.e2. [Google Scholar]
  166. Bos, J.L. Ras oncogenes in human cancer: A review. Cancer Res. 1989, 49, 4682–4689. [Google Scholar]
  167. Ellis, C.A.; Clark, G. The importance of being K-Ras. Cell. Signal. 2000, 12, 425–434. [Google Scholar] [CrossRef]
  168. Ushijima, T.; Sasako, M. Focus on gastric cancer. Cancer Cell 2004, 5, 121–125. [Google Scholar] [CrossRef]
  169. Frame, S.; Balmain, A. Integration of positive and negative growth signals during ras pathway activation in vivo. Curr. Opin. Genet. Dev. 2000, 10, 106–113. [Google Scholar] [CrossRef]
  170. Hingorani, S.R.; Petricoin, E.F.; Maitra, A.; Rajapakse, V.; King, C.; Jacobetz, M.A.; Ross, S.; Conrads, T.P.; Veenstra, T.D.; Hitt, B.A.; et al. Preinvasive and invasive ductal pancreatic cancer and its early detection in the mouse. Cancer Cell 2003, 4, 437–450. [Google Scholar] [CrossRef]
  171. Brembeck, F.H.; Schreiber, F.S.; Deramaudt, T.B.; Craig, L.; Rhoades, B.; Swain, G.; Grippo, P.; Stoffers, D.A.; Silberg, D.G.; Rustgi, A.K. The mutant K-ras oncogene causes pancreatic periductal lymphocytic infiltration and gastric mucous neck cell hyperplasia in transgenic mice. Cancer Res. 2003, 63, 2005–2009. [Google Scholar]
  172. Okumura, T.; Ericksen, R.E.; Takaishi, S.; Wang, S.S.; Dubeykovskiy, Z.; Shibata, W.; Betz, K.S.; Muthupalani, S.; Rogers, A.B.; Fox, J.G.; et al. K-ras mutation targeted to gastric tissue progenitor cells results in chronic inflammation, an altered microenvironment, and progression to intraepithelial neoplasia. Cancer Res. 2010, 70, 8435–8445. [Google Scholar]
  173. Ray, K.C.; Bell, K.M.; Yan, J.; Gu, G.; Chung, C.H.; Washington, M.K.; Means, A.L. Epithelial tissues have varying degrees of susceptibility to Kras(G12D)-initiated tumorigenesis in a mouse model. PLoS One 2011, 6, e16786. [Google Scholar]
  174. Matkar, S.S.; Durham, A.; Brice, A.; Wang, T.C.; Rustgi, A.K.; Hua, X. Systemic activation of K-ras rapidly induces gastric hyperplasia and metaplasia in mice. Am. J. Cancer Res. 2011, 1, 432–445. [Google Scholar]
  175. Park, W.S.; Oh, R.R.; Park, J.Y.; Lee, S.H.; Shin, M.S.; Kim, Y.S.; Kim, S.Y.; Lee, H.K.; Kim, P.J.; Oh, S.T.; et al. Frequent somatic mutations of the beta-catenin gene in intestinal-type gastric cancer. Cancer Res. 1999, 59, 4257–4260. [Google Scholar]
  176. Park, J.G.; Park, K.J.; Ahn, Y.O.; Song, I.S.; Choi, K.W.; Moon, H.Y.; Choo, S.Y.; Kim, J.P. Risk of gastric cancer among Korean familial adenomatous polyposis patients. Report of three cases. Dis. Colon Rectum. 1992, 35, 996–998. [Google Scholar] [CrossRef]
  177. Abraham, S.C.; Nobukawa, B.; Giardiello, F.M.; Hamilton, S.R.; Wu, T.T. Fundic gland polyps in familial adenomatous polyposis: Neoplasms with frequent somatic adenomatous polyposis coli gene alterations. Am. J. Pathol. 2000, 157, 747–754. [Google Scholar]
  178. Fox, J.G.; Dangler, C.A.; Whary, M.T.; Edelman, W.; Kucherlapati, R.; Wang, T.C. Mice carrying a truncated Apc gene have diminished gastric epithelial proliferation, gastric inflammation, and humoral immunity in response to Helicobacter felis infection. Cancer Res. 1997, 57, 3972–3978. [Google Scholar]
  179. Oshima, H.; Matsunaga, A.; Fujimura, T.; Tsukamoto, T.; Taketo, M.M.; Oshima, M. Carcinogenesis in mouse stomach by simultaneous activation of the Wnt signaling and prostaglandin E2 pathway. Gastroenterology 2006, 131, 1086–1095. [Google Scholar] [CrossRef]
  180. Ristimäki, A.; Honkanen, N.; Jänkälä, H.; Sipponen, P.; Härkönen, M. Expression of cyclooxygenase-2 in human gastric carcinoma. Cancer Res. 1997, 57, 1276–1280. [Google Scholar]
  181. Hu, P.J.; Yu, J.; Zeng, Z.R.; Leung, W.K.; Lin, H.L.; Tang, B.D.; Bai, A.H.; Sung, J.J. Chemoprevention of gastric cancer by celecoxib in rats. Gut 2004, 53, 195–200. [Google Scholar] [CrossRef]
  182. Lee, C.W.; Rickman, B.; Rogers, A.B.; Muthupalani, S.; Takaishi, S.; Yang, P.; Wang, T.C.; Fox, J.G. Combination of sulindac and antimicrobial eradication of Helicobacter pylori prevents progression of gastric cancer in hypergastrinemic INS-GAS mice. Cancer Res. 2009, 69, 8166–8174. [Google Scholar]
  183. Xiao, F.; Furuta, T.; Takashima, M.; Shirai, N.; Hanai, H. Effects of cyclooxygenase-2 inhibitor on gastric acid secretion in Helicobacter pylori-infected C57BL/6 mice. Scand. J. Gastroenterol. 2001, 36, 577–583. [Google Scholar] [CrossRef]
  184. Xiao, F.; Furuta, T.; Takashima, M.; Shirai, N.; Hanai, H. Involvement of cyclooxygenase-2 in hyperplastic gastritis induced by Helicobacter pylori infection in C57BL/6 mice. Aliment. Pharmacol. Ther. 2001, 15, 875–886. [Google Scholar] [CrossRef]
  185. Hahm, K.B.; Song, Y.J.; Oh, T.Y.; Lee, J.S.; Surh, Y.J.; Kim, Y.B.; Yoo, B.M.; Kim, J.H.; Han, S.U.; Nahm, K.T.; et al. Chemoprevention of Helicobacter pylori-associated gastric carcinogenesis in a mouse model: Is it possible? J. Biochem. Mol. Biol. 2003, 36, 82–94. [Google Scholar] [CrossRef]
  186. Oshima, H.; Oshima, M.; Inaba, K.; Taketo, M.M. Hyperplastic gastric tumors induced by activated macrophages in COX-2/mPGES-1 transgenic mice. EMBO J. 2004, 23, 1669–1678. [Google Scholar] [CrossRef]
  187. Oshima, M.; Oshima, H.; Matsunaga, A.; Taketo, M.M. Hyperplastic gastric tumors with spasmolytic polypeptide-expressing metaplasia caused by tumor necrosis factor-alpha-dependent inflammation in cyclooxygenase-2/microsomal prostaglandin E synthase-1 transgenic mice. Cancer Res. 2005, 65, 9147–9151. [Google Scholar] [CrossRef]
  188. Takaishi, S.; Okumura, T.; Tu, S.; Wang, S.S.; Shibata, W.; Vigneshwaran, R.; Gordon, S.A.; Shimada, Y.; Wang, T.C. Identification of gastric cancer stem cells using the cell surface marker CD44. Stem Cells 2009, 27, 1006–1020. [Google Scholar] [CrossRef]
  189. Ishimoto, T.; Nagano, O.; Yae, T.; Tamada, M.; Motohara, T.; Oshima, H.; Oshima, M.; Ikeda, T.; Asaba, R.; Yagi, H.; et al. CD44 variant regulates redox status in cancer cells by stabilizing the xCT subunit of system xc(-) and thereby promotes tumor growth. Cancer Cell 2011, 19, 387–400. [Google Scholar] [CrossRef]
  190. Markowitz, S.D.; Roberts, A.B. Tumor suppressor activity of the TGF-beta pathway in human cancers. Cytokine Growth Factor Rev. 1996, 7, 93–102. [Google Scholar]
  191. Yang, H.K.; Kang, S.H.; Kim, Y.S.; Won, K.; Bang, Y.J.; Kim, S.J. Truncation of the TGF-beta type II receptor gene results in insensitivity to TGF-beta in human gastric cancer cells. Oncogene 1999, 18, 2213–2219. [Google Scholar] [CrossRef]
  192. Wu, M.S.; Lee, C.W.; Shun, C.T.; Wang, H.P.; Lee, W.J.; Chang, M.C.; Sheu, J.C.; Lin, J.T. Distinct clinicopathologic and genetic profiles in sporadic gastric cancer with different mutator phenotypes. Genes Chromosomes Cancer 2000, 27, 403–411. [Google Scholar] [CrossRef]
  193. Crawford, S.E.; Stellmach, V.; Murphy-Ullrich, J.E.; Ribeiro, S.M.; Lawler, J.; Hynes, R.O.; Boivin, G.P.; Bouck, N. Thrombospondin-1 is a major activator of TGF-beta1 in vivo. Cell 1998, 93, 1159–1170. [Google Scholar] [CrossRef]
  194. Hahm, K.B.; Lee, K.M.; Kim, Y.B.; Hong, W.S.; Lee, W.H.; Han, S.U.; Kim, M.W.; Ahn, B.O.; Oh, T.Y.; Lee, M.H.; et al. Conditional loss of TGF-beta signalling leads to increased susceptibility to gastrointestinal carcinogenesis in mice. Aliment. Pharmacol. Ther. 2002, 16, 115–127. [Google Scholar]
  195. Xu, X.; Brodie, S.G.; Yang, X.; Im, Y.H.; Parks, W.T.; Chen, L.; Zhou, Y.X.; Weinstein, M.; Kim, S.J.; Deng, C.X. Haploid loss of the tumor suppressor Smad4/Dpc4 initiates gastric polyposis and cancer in mice. Oncogene 2000, 19, 1868–1874. [Google Scholar] [CrossRef]
  196. Takaku, K.; Miyoshi, H.; Matsunaga, A.; Oshima, M.; Sasaki, N.; Taketo, M.M. Gastric and duodenal polyps in Smad4 (Dpc4) knockout mice. Cancer Res. 1999, 59, 6113–6117. [Google Scholar]
  197. Hahn, J.N.; Falck, V.G.; Jirik, F.R. Smad4 deficiency in T cells leads to the Th17-associated development of premalignant gastroduodenal lesions in mice. J. Clin. Invest. 2011, 121, 4030–4042. [Google Scholar] [CrossRef]
  198. Kim, B.G.; Li, C.; Qiao, W.; Mamura, M.; Kasprzak, B.; Kasperczak, B.; Anver, M.; Wolfraim, L.; Hong, S.; Mushinski, E.; et al. Smad4 signalling in T cells is required for suppression of gastrointestinal cancer. Nature 2006, 441, 1015–1019. [Google Scholar]
  199. Tsuzuki, T.; Egashira, A.; Igarashi, H.; Iwakuma, T.; Nakatsuru, Y.; Tominaga, Y.; Kawate, H.; Nakao, K.; Nakamura, K.; Ide, F.; et al. Spontaneous tumorigenesis in mice defective in the MTH1 gene encoding 8-oxo-dGTPase. Proc. Natl. Acad. Sci. USA 2001, 98, 11456–11461. [Google Scholar]
  200. Shimada, S.; Mimata, A.; Sekine, M.; Mogushi, K.; Akiyama, Y.; Fukamachi, H.; Jonkers, J.; Tanaka, H.; Eishi, Y.; Yuasa, Y. Synergistic tumour suppressor activity of E-cadherin and p53 in a conditional mouse model for metastatic diffuse-type gastric cancer. Gut 2012, 61, 344–353. [Google Scholar]
  201. Ito, K.; Chuang, L.S.; Ito, T.; Chang, T.L.; Fukamachi, H.; Salto-Tellez, M.; Ito, Y. Loss of Runx3 is a key event in inducing precancerous state of the stomach. Gastroenterology 2011, 140, 1536–1546.e8. [Google Scholar] [CrossRef]
  202. Ito, K.; Liu, Q.; Salto-Tellez, M.; Yano, T.; Tada, K.; Ida, H.; Huang, C.; Shah, N.; Inoue, M.; Rajnakova, A.; et al. RUNX3, a novel tumor suppressor, is frequently inactivated in gastric cancer by protein mislocalization. Cancer Res. 2005, 65, 7743–7750. [Google Scholar]
  203. Li, Q.L.; Ito, K.; Sakakura, C.; Fukamachi, H.; Inoue, K.; Chi, X.Z.; Lee, K.Y.; Nomura, S.; Lee, C.W.; Han, S.B.; et al. Causal relationship between the loss of RUNX3 expression and gastric cancer. Cell 2002, 109, 113–124. [Google Scholar] [CrossRef]
  204. Desai, T.K.; Barkel, D. Syndromic colon cancer: Lynch syndrome and familial adenomatous polyposis. Gastroenterol. Clin. North. Am. 2008, 37, 47–72. [Google Scholar] [CrossRef]
  205. Fox, J.G.; Li, X.; Cahill, R.J.; Andrutis, K.; Rustgi, A.K.; Odze, R.; Wang, T.C. Hypertrophic gastropathy in Helicobacter felis-infected wild-type C57BL/6 mice and p53 hemizygous transgenic mice. Gastroenterology 1996, 110, 155–166. [Google Scholar] [CrossRef]
  206. Jenks, P.J.; Jeremy, A.H.; Robinson, P.A.; Walker, M.M.; Crabtree, J.E. Long-term infection with Helicobacter felis and inactivation of the tumour suppressor gene p53 cumulatively enhance the gastric mutation frequency in Big Blue transgenic mice. J. Pathol. 2003, 201, 596–602. [Google Scholar] [CrossRef]
  207. Ohgaki, H.; Fukuda, M.; Tohma, Y.; Huang, H.; Stoica, G.; Tatematsu, M.; Donehower, L.A. Effect of intragastric application of N-methylnitrosourea in p53 knockout mice. Mol. Carcinog. 2000, 28, 97–101. [Google Scholar] [CrossRef]
  208. Suzuki, H.; Miyazawa, M.; Kai, A.; Suzuki, M.; Suematsu, M.; Miura, S.; Ishii, H. No difference in the level of gastric mucosal cell apoptosis and proliferation in Helicobacter pylori-colonized p53 heterozygous knockout mice. Aliment. Pharmacol. Ther. 2002, 16, 158–166. [Google Scholar] [CrossRef]
  209. Wei, D.; Gong, W.; Kanai, M.; Schlunk, C.; Wang, L.; Yao, J.C.; Wu, T.T.; Huang, S.; Xie, K. Drastic down-regulation of Krüppel-like factor 4 expression is critical in human gastric cancer development and progression. Cancer Res. 2005, 65, 2746–2754. [Google Scholar]
  210. Becker, K.F.; Atkinson, M.J.; Reich, U.; Becker, I.; Nekarda, H.; Siewert, J.R.; Höfler, H. E-cadherin gene mutations provide clues to diffuse type gastric carcinomas. Cancer Res. 1994, 54, 3845–3852. [Google Scholar]
  211. Tamura, G.; Yin, J.; Wang, S.; Fleisher, A.S.; Zou, T.; Abraham, J.M.; Kong, D.; Smolinski, K.N.; Wilson, K.T.; James, S.P.; et al. E-Cadherin gene promoter hypermethylation in primary human gastric carcinomas. J. Natl. Cancer Inst. 2000, 92, 569–573. [Google Scholar] [CrossRef]
  212. Guilford, P.; Hopkins, J.; Harraway, J.; McLeod, M.; McLeod, N.; Harawira, P.; Taite, H.; Scoular, R.; Miller, A.; Reeve, A.E. E-cadherin germline mutations in familial gastric cancer. Nature 1998, 392, 402–405. [Google Scholar] [CrossRef]
  213. Takagi, H.; Fukusato, T.; Kawaharada, U.; Kuboyama, S.; Merlino, G.; Tsutsumi, Y. Histochemical analysis of hyperplastic stomach of TGF-alpha transgenic mice. Dig. Dis. Sci. 1997, 42, 91–98. [Google Scholar] [CrossRef]
  214. Li, Q.; Karam, S.M.; Gordon, J.I. Diphtheria toxin-mediated ablation of parietal cells in the stomach of transgenic mice. J. Biol. Chem. 1996, 271, 3671–3676. [Google Scholar]
  215. Canfield, V.; West, A.B.; Goldenring, J.R.; Levenson, R. Genetic ablation of parietal cells in transgenic mice: A new model for analyzing cell lineage relationships in the gastric mucosa. Proc. Natl. Acad. Sci. USA 1996, 93, 2431–2435. [Google Scholar]
  216. Spicer, Z.; Miller, M.L.; Andringa, A.; Riddle, T.M.; Duffy, J.J.; Doetschman, T.; Shull, G.E. Stomachs of mice lacking the gastric H,K-ATPase alpha -subunit have achlorhydria, abnormal parietal cells, and ciliated metaplasia. J. Biol. Chem. 2000, 275, 21555–21565. [Google Scholar]
  217. Scarff, K.L.; Judd, L.M.; Toh, B.H.; Gleeson, P.A.; van Driel, I.R. Gastric H(+),K(+)-adenosine triphosphatase beta subunit is required for normal function, development, and membrane structure of mouse parietal cells. Gastroenterology 1999, 117, 605–618. [Google Scholar] [CrossRef]
  218. Franic, T.V.; Judd, L.M.; Robinson, D.; Barrett, S.P.; Scarff, K.L.; Gleeson, P.A.; Samuelson, L.C.; van Driel, I.R. Regulation of gastric epithelial cell development revealed in H(+)/K(+)-ATPase beta-subunit- and gastrin-deficient mice. Am. J. Physiol. Gastrointest. Liver Physiol. 2001, 281, G1502–G1511. [Google Scholar]
  219. Schultheis, P.J.; Clarke, L.L.; Meneton, P.; Harline, M.; Boivin, G.P.; Stemmermann, G.; Duffy, J.J.; Doetschman, T.; Miller, M.L.; Shull, G.E. Targeted disruption of the murine Na+/H+ exchanger isoform 2 gene causes reduced viability of gastric parietal cells and loss of net acid secretion. J. Clin. Invest. 1998, 101, 1243–1253. [Google Scholar] [CrossRef]
  220. Gut, M.O.; Parkkila, S.; Vernerová, Z.; Rohde, E.; Závada, J.; Höcker, M.; Pastorek, J.; Karttunen, T.; Gibadulinová, A.; Závadová, Z.; et al. Gastric hyperplasia in mice with targeted disruption of the carbonic anhydrase gene Car9. Gastroenterology 2002, 123, 1889–1903. [Google Scholar] [CrossRef]
  221. Nagata, A.; Ito, M.; Iwata, N.; Kuno, J.; Takano, H.; Minowa, O.; Chihara, K.; Matsui, T.; Noda, T. G protein-coupled cholecystokinin-B/gastrin receptors are responsible for physiological cell growth of the stomach mucosa in vivo. Proc. Natl. Acad. Sci. USA 1996, 93, 11825–11830. [Google Scholar]
  222. Langhans, N.; Rindi, G.; Chiu, M.; Rehfeld, J.F.; Ardman, B.; Beinborn, M.; Kopin, A.S. Abnormal gastric histology and decreased acid production in cholecystokinin-B/gastrin receptor-deficient mice. Gastroenterology 1997, 112, 280–286. [Google Scholar] [CrossRef]
  223. Xiao, C.; Ogle, S.A.; Schumacher, M.A.; Orr-Asman, M.A.; Miller, M.L.; Lertkowit, N.; Varro, A.; Hollande, F.; Zavros, Y. Loss of parietal cell expression of Sonic hedgehog induces hypergastrinemia and hyperproliferation of surface mucous cells. Gastroenterology 2010, 138, 550–561.e8. [Google Scholar]
  224. Goldenring, J.R.; Ray, G.S.; Coffey, R.J.; Meunier, P.C.; Haley, P.J.; Barnes, T.B.; Car, B.D. Reversible drug-induced oxyntic atrophy in rats. Gastroenterology 2000, 118, 1080–1093. [Google Scholar]
  225. Nomura, S.; Settle, S.H.; Leys, C.M.; Means, A.L.; Peek, R.M.; Leach, S.D.; Wright, C.V.; Coffey, R.J.; Goldenring, J.R. Evidence for repatterning of the gastric fundic epithelium associated with Ménétrier's disease and TGFalpha overexpression. Gastroenterology 2005, 128, 1292–1305. [Google Scholar] [CrossRef]
  226. Nam, K.T.; Lee, H.J.; Sousa, J.F.; Weis, V.G.; O'Neal, R.L.; Finke, P.E.; Romero-Gallo, J.; Shi, G.; Mills, J.C.; Peek, R.M.; et al. Mature chief cells are cryptic progenitors for metaplasia in the stomach. Gastroenterology 2010, 139, 2028–2037.e9. [Google Scholar] [CrossRef]
  227. Silberg, D.G.; Sullivan, J.; Kang, E.; Swain, G.P.; Moffett, J.; Sund, N.J.; Sackett, S.D.; Kaestner, K.H. Cdx2 ectopic expression induces gastric intestinal metaplasia in transgenic mice. Gastroenterology 2002, 122, 689–696. [Google Scholar] [CrossRef]
  228. Mutoh, H.; Hakamata, Y.; Sato, K.; Eda, A.; Yanaka, I.; Honda, S.; Osawa, H.; Kaneko, Y.; Sugano, K. Conversion of gastric mucosa to intestinal metaplasia in Cdx2-expressing transgenic mice. Biochem. Biophys. Res. Commun. 2002, 294, 470–479. [Google Scholar] [CrossRef]
  229. Mutoh, H.; Sakurai, S.; Satoh, K.; Osawa, H.; Hakamata, Y.; Takeuchi, T.; Sugano, K. Cdx1 induced intestinal metaplasia in the transgenic mouse stomach: Comparative study with Cdx2 transgenic mice. Gut 2004, 53, 1416–1423. [Google Scholar] [CrossRef]
  230. Friis-Hansen, L.; Sundler, F.; Li, Y.; Gillespie, P.J.; Saunders, T.L.; Greenson, J.K.; Owyang, C.; Rehfeld, J.F.; Samuelson, L.C. Impaired gastric acid secretion in gastrin-deficient mice. Am. J. Physiol. 1998, 274, G561–G568. [Google Scholar]
  231. Goldenring, J.R.; Nomura, S. Differentiation of the gastric mucosa III. Animal models of oxyntic atrophy and metaplasia. Am. J. Physiol. Gastrointest. Liver Physiol. 2006, 291, G999–G1004. [Google Scholar] [CrossRef]
  232. Hattori, T. Development of adenocarcinomas in the stomach. Cancer 1986, 57, 1528–1534. [Google Scholar] [CrossRef]
  233. Goldenring, J.R.; Wang, T.C.; Mills, J.C.; Wright, N.A. Spasmolytic polypeptide-expressing metaplasia: Time for reevaluation of metaplasias and the origins of gastric cancer. Gastroenterology 2010, 138, 2207–2210. [Google Scholar]
  234. Barker, N.; van Es, J.H.; Kuipers, J.; Kujala, P.; van den Born, M.; Cozijnsen, M.; Haegebarth, A.; Korving, J.; Begthel, H.; Peters, P.J.; et al. Identification of stem cells in small intestine and colon by marker gene Lgr5. Nature 2007, 449, 1003–1007. [Google Scholar] [CrossRef]
  235. Powell, A.E.; Wang, Y.; Li, Y.; Poulin, E.J.; Means, A.L.; Washington, M.K.; Higginbotham, J.N.; Juchheim, A.; Prasad, N.; Levy, S.E.; et al. The pan-ErbB negative regulator Lrig1 is an intestinal stem cell marker that functions as a tumor suppressor. Cell 2012, 149, 146–158. [Google Scholar] [CrossRef]
  236. Arnold, K.; Sarkar, A.; Yram, M.A.; Polo, J.M.; Bronson, R.; Sengupta, S.; Seandel, M.; Geijsen, N.; Hochedlinger, K. Sox2(+) adult stem and progenitor cells are important for tissue regeneration and survival of mice. Cell Stem Cell 2011, 9, 317–329. [Google Scholar] [CrossRef]
  237. Furuyama, K.; Kawaguchi, Y.; Akiyama, H.; Horiguchi, M.; Kodama, S.; Kuhara, T.; Hosokawa, S.; Elbahrawy, A.; Soeda, T.; Koizumi, M.; et al. Continuous cell supply from a Sox9-expressing progenitor zone in adult liver, exocrine pancreas and intestine. Nat. Genet. 2011, 43, 34–41. [Google Scholar] [CrossRef]
  238. Sangiorgi, E.; Capecchi, M.R. Bmi1 is expressed in vivo in intestinal stem cells. Nat. Genet. 2008, 40, 915–920. [Google Scholar] [CrossRef]
  239. Takeda, N.; Jain, R.; LeBoeuf, M.R.; Wang, Q.; Lu, M.M.; Epstein, J.A. Interconversion between intestinal stem cell populations in distinct niches. Science 2011, 334, 1420–1424. [Google Scholar] [CrossRef]
  240. Barker, N.; Huch, M.; Kujala, P.; van de Wetering, M.; Snippert, H.J.; van Es, J.H.; Sato, T.; Stange, D.E.; Begthel, H.; van den Born, M.; et al. Lgr5(+ve) stem cells drive self-renewal in the stomach and build long-lived gastric units in vitro. Cell Stem Cell 2010, 6, 25–36. [Google Scholar] [CrossRef]
  241. Qiao, X.T.; Ziel, J.W.; McKimpson, W.; Madison, B.B.; Todisco, A.; Merchant, J.L.; Samuelson, L.C.; Gumucio, D.L. Prospective identification of a multilineage progenitor in murine stomach epithelium. Gastroenterology 2007, 133, 1989–1998. [Google Scholar] [CrossRef]
  242. Quante, M.; Marrache, F.; Goldenring, J.R.; Wang, T.C. TFF2 mRNA transcript expression marks a gland progenitor cell of the gastric oxyntic mucosa. Gastroenterology 2010, 139, 2018–2027.e2. [Google Scholar] [CrossRef]
  243. Kim, T.H.; Shivdasani, R.A. Notch signaling in stomach epithelial stem cell homeostasis. J. Exp. Med. 2011, 208, 677–688. [Google Scholar] [CrossRef]
  244. Zang, Z.J.; Cutcutache, I.; Poon, S.L.; Zhang, S.L.; McPherson, J.R.; Tao, J.; Rajasegaran, V.; Heng, H.L.; Deng, N.; Gan, A.; et al. Exome sequencing of gastric adenocarcinoma identifies recurrent somatic mutations in cell adhesion and chromatin remodeling genes. Nat. Genet. 2012, 44, 570–574. [Google Scholar] [CrossRef]
  245. Sakamoto, H.; Yoshimura, K.; Saeki, N.; Katai, H.; Shimoda, T.; Matsuno, Y.; Saito, D.; Sugimura, H.; Tanioka, F.; Kato, S.; et al. Genetic variation in PSCA is associated with susceptibility to diffuse-type gastric cancer. Nat. Genet. 2008, 40, 730–740. [Google Scholar] [CrossRef]
  246. Shi, Y.; Hu, Z.; Wu, C.; Dai, J.; Li, H.; Dong, J.; Wang, M.; Miao, X.; Zhou, Y.; Lu, F.; et al. A genome-wide association study identifies new susceptibility loci for non-cardia gastric cancer at 3q13.3.31 and 5p13.1. Nat. Genet. 2011, 43, 1215–1218. [Google Scholar] [CrossRef]
  247. Abnet, C.C.; Freedman, N.D.; Hu, N.; Wang, Z.; Yu, K.; Shu, X.O.; Yuan, J.M.; Zheng, W.; Dawsey, S.M.; Dong, L.M.; et al. A shared susceptibility locus in PLCE1 at 10q23 for gastric adenocarcinoma and esophageal squamous cell carcinoma. Nat. Genet. 2010, 42, 764–767. [Google Scholar] [CrossRef]
Cancers EISSN 2072-6694 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert