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Int. J. Mol. Sci. 2013, 14(5), 9487-9496; doi:10.3390/ijms14059487
Abstract: Helicobacter pylori (H. pylori) infection is the main cause of gastritis, gastro-duodenal ulcer, and gastric cancer. MicroRNAs (miRNAs) are small noncoding RNAs that function as endogenous silencers of numerous target genes. Many miRNA genes are expressed in a tissue-specific manner and play important roles in cell proliferation, apoptosis, and differentiation. Recent discoveries have shed new light on the involvement of miRNAs in gastric malignancy. However, at the same time, several miRNAs have been associated with opposing events, leading to reduced inflammation, inhibition of malignancy, and increased apoptosis of transformed cells. The regulation of miRNA expression could be a novel strategy in the chemoprevention of human gastric malignancy. In this article, the biological importance of miRNAs in gastric malignancy is summarized.
Helicobacter pylori (H. pylori) infection is one of the most prevalent infectious diseases worldwide, and is estimated to affect 40%–50% of the world population . H. pylori has been identified as a group 1 carcinogen by the World Health Organization and is associated with the development of gastric cancer . H. pylori eradication has been shown to have a prophylactic effect on gastric cancer [3,4].
MicroRNAs (miRNAs) are noncoding RNAs comprising 18–24 nucleotides that can post-transcriptionally downregulate various target genes . It is estimated that the human genome encodes more than one thousand miRNAs, targeting 30%–60% of all protein-coding genes . They are expressed in a tissue-specific manner, and play important roles in cell proliferation, apoptosis, and differentiation [5,7]. Moreover, recent studies have shown a connection between aberrant expression of miRNAs and the development of cancer. In this article, the biological importance of miRNAs in gastric malignancy is summarized.
2. Helicobacter pylori and miRNA
CagA of H. pylori is a bacterium-derived oncogenic protein closely associated with the development of gastric cancers . After injection into host cells using a type IV secretion system, CagA is phosphorylated at tyrosine residues by the c-Src and Lyn kinases. Phosphorylated CagA then activates the Src homology-2 domain-containing phosphatase 2 (SHP2), which activates the Erk1/2 pathway. CagA translocated into CD44v9-positive gastric cancer stem-like cells is thought to escape from reactive oxygen species-dependent autophagy, resulting in gastric carcinogenesis .
miRNA changes in response to H. pylori infection are summarized in Table 1. miR-584 and miR-1290 expression are upregulated in CagA-transformed cells. The miR-584 and miR-1290 target is Foxa1, and knockdown of Foxa1 promotes the epithelial-mesenchymal transition (EMT). Overexpression of miR-584 and miR-1290 induces intestinal metaplasia of gastric epithelial cells. These results indicate that miR-584 and miR-1290 interfere with cell differentiation and lead to remodeling of the gastric mucosal tissues .
CagA enhances c-myc and DNA methyltransferase 3B, and attenuates miR-6a and miR-101 expression, which results in the attenuation of let-7 expression by histone and DNA methylation. CagA induces aberrant epigenetic silencing of let-7 expression, leading to Ras pathway activation. Thus, the miRNA pathway is a new pathogenic mechanism for CagA.
Shiotani et al.  reported that the expression of oncogenic miRNAs (miR-17/92 and the miR-106b-93-25 cluster, miR-21, miR-194, and miR-196) is significantly higher in the intestinal metaplasia than in the non-intestinal metaplasia. H. pylori eradication improves miRNA deregulation, but not in the intestinal metaplasia. Long-term colonization of H. pylori might induce an epigenetic modification of gastric mucosal genes, including the promoter of tumor suppressor miRNAs, but this is not completely reversible by bacterial eradication alone. Epigenetic therapy in severe atrophic or metaplastic gastric mucosa after H. pylori eradication might be a possible option for gastric cancer prevention.
3. Cell Cycle Progression and miRNA
The dysregulation of cell cycle progression is a hallmark of malignancy. Cyclin-CDK (cyclin-dependent kinase) complexes regulate this progression through the cell cycle. miRNA dysregulation promotes cell cycle progression by upregulating cyclin expression or downregulating expression of CDK inhibitors (p57, p21, etc.) in numerous malignancies (Figure 1). miR-449 is downregulated in H. pylori-infected gastric mucosa and in gastric cancer and targets cyclin E2 and geminin. Both cyclin E2 and geminin are overexpressed in various malignancies and promote G1/S and M/G1 cell cycle progression . Consequently, downregulation of miR-449, as occurs following H. pylori infection, promotes cell cycle progression and proliferation through the upregulation of cyclin E2 and geminin.
G2/M cell cycle progression and proliferation in gastric cancer cells are regulated by p42.3 ; miR-29a is significantly downregulated in gastric cancer and targets p42.3  (Figure 1). Thus, the downregulation of miR-29a results in a reciprocal increase in p42.3 expression, promoting increased cell cycle progression and proliferation.
Both miR-93 and miR-106b directly target p21, resulting in its transcriptional silencing and impairment of its tumor-suppressing activity . In addition, miR-25 targets p57, while miR-221 and miR-222 target p27 and p57  (Figure 1). These oncogenic miRNA clusters are also significantly upregulated in gastric cancer . Overexpression of most of these miRNAs results in activation of CDK2, thereby promoting G1/S phase progression.
4. Inhibition of Apoptosis and miRNA
Evasion of apoptosis is a common feature of malignancy. Apoptosis is classifiable as either intrinsic or extrinsic pathway-dependent. The extrinsic apoptosis pathway is initiated on the cell surface through the activation of specific pro-apoptotic death receptors. Tumor necrosis factors are cytokines produced mainly by activated macrophages that bind the death receptors as their ligands. Ligand binding induces receptor clustering and the recruitment of the adaptor protein Fas-associated death domain (FADD), leading to induction of caspases and ultimately cell death. miR-155 targets FADD, leading to decreased expression of this key adaptor molecule (Figure 2) . Therefore, the upregulation of miR-155 by H. pylori and during carcinogenesis results in the downregulation of FADD and the inhibition of apoptosis.
The intrinsic pathway is initiated within cells and hinges on the balance of activity between pro-apoptotic (e.g., Bax, Bak, Bim, BNIP3L, and Bid) and anti-apoptotic (e.g., Bcl-2, Bcl-xL, and Mcl-1) proteins from the Bcl-2 (B cell lymphoma 2) superfamily. Some miRNAs overexpressed in gastric cancer function as oncogenic miRNAs by targeting members of the pro-apoptotic proteins. miR-25, miR-93, miR-106b, and miR-130 inhibit apoptosis by preventing the expression of the pro-apoptotic protein, Bim (Figure 2) .
Tumor suppressor miRNAs (miR-15b, miR-16, miR-34, miR-181b, miR-181c, and miR-497) target anti-apoptotic Bcl-2. These miRNA clusters are downregulated in gastric cancer cells, leading to increased expression of Bcl-2 and inhibition of apoptosis. The miR-200bc/429 cluster is downregulated in H. pylori-infected gastric mucosa, and these miRNAs directly target Bcl-2 and XIAP (x-linked inhibitor of apoptosis) . miR-101 and miR-515-5p target Mcl-1, which are downregulated in gastric cancer, lead to increased levels of Mcl-1 and an anti-apoptotic phenotype (Figure 2).
In addition to targeting proteins directly involved in the intrinsic and extrinsic cell death pathways, miRNAs target other factors that ultimately lead to apoptosis inhibition and increased proliferation. miR-21 targets PTEN (phosphatase and tensin homolog), a tumor suppressor and negative regulator of the PI3K/Akt signaling pathway. miR-21 is upregulated in gastric cancer, and its overexpression shifts the balance between proliferation and apoptosis, by increasing cellular proliferation and inhibiting apoptosis.
miR-375 targets 3-phophoinositide dependent protein kinase (PDK1), a kinase that directly phosphorylates Akt, thereby regulating the PI3K/Akt signaling pathway. Overexpression of miR-375 reduces cell viability and miR-375 is downregulated in gastric cancer (Figure 2) .
5. Metastasis and miRNA
Some miRNAs that are known to regulate cell cycle progression and apoptosis pathways are also involved in invasion and metastasis. miR-181b is aberrantly overexpressed in H. pylori infection and gastric cancer tissues . Cell proliferation, migration, and invasion in the gastric cancer cells were significantly increased after miR-181b transfection, and the number of apoptotic cells was also increased. Furthermore, overexpression of miR-181b downregulated the protein levels of tissue inhibitor of metalloproteinase 3 (TIMP). The upregulation of miR-181b may play an important role in the progression of gastric cancer and miR-181b may be a potential molecular target for gastric cancer therapies.
miR-218 is reduced significantly in gastric cancer tissues, H. pylori-infected gastric mucosa, and H. pylori-infected AGS cells . miR-218, a tumor suppressor miRNA, is downregulated in gastric cancer, which correlates with increased metastasis and cancer invasion . This downregulation is thought to occur through the direct targeting of roundabout homolog (ROBO1), which leads to enhanced signaling through the ROBO1 receptor. The SLIT/ROBO signaling pathway is implicated in many biological responses through regulating cell migration. Thus, disruption of this signaling cascade can result in increased invasion and metastasis. miR-21 also targets RECK (reversion-inducing-cysteine-rich protein with kazal motifs), a tumor and metastasis suppressor that inhibits tumor metastasis and angiogenesis through modulation of matrix metalloproteinases. Recently, Li et al. indicated that miR-21, miR-218, and miR-223 may be potential biomarkers for gastric cancer detection .
miR-148a is downregulated in gastric cancer. The protein interaction network regulated by miR-148a is associated with metastasis-related function, such as integrin-mediated signaling, cell-matrix adhesion, and blood coagulation . A single miRNA can provoke a chain reaction and further affect the protein interaction network. This interactive network-based approach could provide insight into carcinogenesis.
6. miRNA and Anticancer Therapy
miRNAs are promising molecular targets for anticancer therapeutics in gastric cancer. Kim et al. reported that miR-10b was silenced in gastric cancer cells by promoter methylation. miR-10b targets the oncogene that encodes microtubule-associated protein, RP/EB family member 1. After 5-aza-2′-deoxycytidine treatment of gastric cancer cells, miR-10b methylation is significantly decreased, and the expression of miR-10b is restored. The modulation of miR-10b may represent a therapeutic approach for treating gastric cancer .
Runx3 is an important tumor suppressor that is inactivated in gastric cancer, and promoter hypermethylation of Runx3 is frequent . 5-aza-2′-deoxycytidine treatment reactivates the expression of Runx3. Lai et al. reported that miR-130b expression is upregulated in gastric cancer, and this is inversely associated with Runx3 hypermethylation. miR-130b overexpression increases cell viability, reduces cell death, and decreases the expression of Bim in TGF-beta mediated apoptosis, subsequent to the downregulation of Runx3 protein expression. The attenuation of Runx3 protein levels by miRNA may reduce the growth suppressive potential of Runx3 and contribute to tumorigenesis . Wang et al. reported that miR-301a is upregulated in gastric cancer, and directly downregulates Runx3 expression .
The selective cyclooxygenase-2 (COX-2) inhibitor celecoxib is a potential drug for the treatment of gastrointestinal tumors. We investigated the role of miRNAs in gastric carcinogenesis and the feasibility of a new therapeutic approach for gastric cancer . miRNA microarray analysis revealed that miR-29c is significantly downregulated in gastric cancer tissues relative to non-tumor gastric mucosa . miR-29c is significantly activated by celecoxib in gastric cancer cells (AGS) . Celecoxib activation of miR-29c induces suppression of the oncogene Mcl-1, a target of miR-29c and apoptosis in gastric cancer cells. These results suggest that the downregulation of the miR-29c tumor suppressor plays a critical role in the progression of gastric cancer. As such, selective COX-2 inhibitors may be a clinical option for the treatment of gastric cancer via restoration of miR-29c.
7. MALT Lymphoma and miRNA
Gastric B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma) develops in the chronically inflamed mucosa of patients infected with the bacterial pathogen. In 60%–80% of these cases, the H. pylori-positive gastric MALT lymphoma regresses after H. pylori eradication. The t(11;18) (q21;q21) translocation is associated with API2-MALT1 fusion, and this translocation responds only rarely or not at all to H. pylori eradication.
We previously reported that a hematopoietic-specific miRNA, miR-142, and an oncogenic miRNA, miR-155, are overexpressed in MALT lymphoma lesions . miR-142-5p and miR-155 suppress the proapoptotic gene TP53INP1 as their target . The expression levels of miR-142-5p and miR-155 are significantly increased in MALT lymphomas that do not respond to H. pylori eradication . The expression levels of miR-142-5p and miR-155 are associated with the clinical courses of gastric MALT lymphoma cases and these miRNAs may have a potential application as novel biomarkers for gastric MALT lymphoma.
Craig et al. reported the strong downregulation of the putative tumor suppressor miRNA, miR-203, in human MALT lymphoma samples, which results from extensive promoter hypermethylation of the miR-203 locus and coincides with the deregulation of its target, ABL1. Treatment of lymphoma B cells with demethylating agents leads to increased miR-203 expression and concomitant downregulation of ABL1, confirming the effectiveness of epigenetic regulation of this miRNA. These results show that the transformation from gastritis to MALT lymphoma is epigenetically regulated by miR-203 promoter methylation and identifies ABL1 as a novel target for treatment .
Although generally considered an indolent disease, MALT lymphoma may have the ability to transform into gastric diffuse large B-cell lymphoma (gDLBCL). Craig et al. reported that Myc overexpression is detected in 80% of gDLBCLs, but only 20% of MALT lymphomas are spotted on a tissue microarray. FoxP1 overexpression is detectible in gDLBCL, but not in gastric MALT lymphoma. miR-34a is downregulated in malignant lymphoma, as are the targets of miR-34a, Myc and FoxP1 and miR-34a shows strong antiproliferative properties when overexpressed in DLBCL cells. miR-34a replacement therapy is therefore a promising strategy in lymphoma treatment .
As we are just beginning to understand the relationship between miRNAs and gastric malignancies and the number of identified miRNA genes is increasing, there is a potential for a large number of therapeutic targets and biomarkers in this area. Further studies are necessary to investigate whether miRNA-oriented therapy is an effective strategy for the chemoprevention of gastric malignancies.
Conflict of Interest
The authors declare no conflict of interest.
- Suzuki, H.; Iwasaki, E.; Hibi, T. Helicobacter pylori and gastric cancer. Gastric Cancer 2009, 12, 79–87. [Google Scholar]
- Suzuki, H.; Nishizawa, T.; Hibi, T. Helicobacter pylori eradication therapy. Future Microbiol 2010, 5, 639–648. [Google Scholar]
- Nishizawa, T.; Suzuki, H.; Nakagawa, I.; Minegishi, Y.; Masaoka, T.; Iwasaki, E.; Hibi, T. Early Helicobacter pylori eradication restores sonic hedgehog expression in the gastric mucosa of Mongolian gerbils. Digestion 2009, 79, 99–108. [Google Scholar]
- Fukase, K.; Kato, M.; Kikuchi, S.; Inoue, K.; Uemura, N.; Okamoto, S.; Terao, S.; Amagai, K.; Hayashi, S.; Asaka, M. Effect of eradication of Helicobacter pylori on incidence of metachronous gastric carcinoma after endoscopic resection of early gastric cancer: An open-label, randomised controlled trial. Lancet 2008, 372, 392–397. [Google Scholar]
- Saito, Y.; Suzuki, H.; Hibi, T. The role of microRNAs in gastrointestinal cancers. J. Gastroenterol 2009, 44, 18–22. [Google Scholar]
- Noto, J.M.; Peek, R.M. The role of microRNAs in Helicobacter pylori pathogenesis and gastric carcinogenesis. Front Cell Infect Microbiol 2011, 1, 21. [Google Scholar]
- Saito, Y.; Suzuki, H.; Tsugawa, H.; Suzuki, S.; Matsuzaki, J.; Hirata, K.; Hibi, T. Dysfunctional gastric emptying with down-regulation of muscle-specific microRNAs in Helicobacter pylori-infected mice. Gastroenterology 2011, 140, 189–198. [Google Scholar]
- Suzuki, H.; Nishizawa, T.; Tsugawa, H.; Mogami, S.; Hibi, T. Roles of oxidative stress in stomach disorders. J. Clin. Biochem. Nutr 2012, 50, 35–39. [Google Scholar]
- Tsugawa, H.; Suzuki, H.; Saya, H.; Hatakeyama, M.; Hirayama, T.; Hirata, K.; Nagano, O.; Matsuzaki, J.; Hibi, T. Reactive oxygen species-induced autophagic degradation of Helicobacter pylori caga is specifically suppressed in cancer stem-like cells. Cell Host Microbe 2012, 12, 764–777. [Google Scholar]
- Zhu, Y.; Jiang, Q.; Lou, X.; Ji, X.; Wen, Z.; Wu, J.; Tao, H.; Jiang, T.; He, W.; Wang, C.; et al. MicroRNAs up-regulated by CagA of Helicobacter pylori induce intestinal metaplasia of gastric epithelial cells. PLoS One 2012, 7, e35147. [Google Scholar]
- Shiotani, A.; Uedo, N.; Iishi, H.; Murao, T.; Kanzaki, T.; Kimura, Y.; Kamada, T.; Kusunoki, H.; Inoue, K.; Haruma, K. H. pylori eradication did not improve dysregulation of specific oncogenic miRNAs in intestinal metaplastic glands. J. Gastroenterol 2012, 47, 988–998. [Google Scholar]
- Xu, X.; Li, W.; Fan, X.; Liang, Y.; Zhao, M.; Zhang, J.; Tong, W.; Wang, J.; Yang, W.; Lu, Y. Identification and characterization of a novel p42.3 gene as tumor-specific and mitosis phase-dependent expression in gastric cancer. Oncogene 2007, 26, 7371–7379. [Google Scholar]
- Cui, Y.; Su, W.Y.; Xing, J.; Wang, Y.C.; Wang, P.; Chen, X.Y.; Shen, Z.Y.; Cao, H.; Lu, Y.Y.; Fang, J.Y. MiR-29a inhibits cell proliferation and induces cell cycle arrest through the downregulation of p42.3 in human gastric cancer. PLoS One 2011, 6, e25872. [Google Scholar]
- Kan, T.; Sato, F.; Ito, T.; Matsumura, N.; David, S.; Cheng, Y.; Agarwal, R.; Paun, B.C.; Jin, Z.; Olaru, A.V.; et al. The miR-106b-25 polycistron, activated by genomic amplification, functions as an oncogene by suppressing p21 and Bim. Gastroenterology 2009, 136, 1689–1700. [Google Scholar]
- Kim, Y.K.; Yu, J.; Han, T.S.; Park, S.Y.; Namkoong, B.; Kim, D.H.; Hur, K.; Yoo, M.W.; Lee, H.J.; Yang, H.K.; et al. Functional links between clustered microRNAs: Suppression of cell-cycle inhibitors by microRNA clusters in gastric cancer. Nucleic Acids Res 2009, 37, 1672–1681. [Google Scholar]
- Volinia, S.; Calin, G.A.; Liu, C.G.; Ambs, S.; Cimmino, A.; Petrocca, F.; Visone, R.; Iorio, M.; Roldo, C.; Ferracin, M.; et al. A microRNA expression signature of human solid tumors defines cancer gene targets. Proc. Natl. Acad. Sci. USA 2006, 103, 2257–2261. [Google Scholar]
- Xiao, B.; Liu, Z.; Li, B.S.; Tang, B.; Li, W.; Guo, G.; Shi, Y.; Wang, F.; Wu, Y.; Tong, W.D.; et al. Induction of microRNA-155 during Helicobacter pylori infection and its negative regulatory role in the inflammatory response. J. Infect Dis 2009, 200, 916–925. [Google Scholar]
- Zhu, W.; Xu, H.; Zhu, D.; Zhi, H.; Wang, T.; Wang, J.; Jiang, B.; Shu, Y.; Liu, P. miR-200bc/429 cluster modulates multidrug resistance of human cancer cell lines by targeting BCL2 and XIAP. Cancer Chemother. Pharmacol 2012, 69, 723–731. [Google Scholar]
- Tsukamoto, Y.; Nakada, C.; Noguchi, T.; Tanigawa, M.; Nguyen, L.T.; Uchida, T.; Hijiya, N.; Matsuura, K.; Fujioka, T.; Seto, M.; et al. MicroRNA-375 is downregulated in gastric carcinomas and regulates cell survival by targeting PDK1 and 14-3-3zeta. Cancer Res 2010, 70, 2339–2349. [Google Scholar]
- Guo, J.X.; Tao, Q.S.; Lou, P.R.; Chen, X.C.; Chen, J.; Yuan, G.B. miR-181b as a potential molecular target for anticancer therapy of gastric neoplasms. Asian Pac. J. Cancer Prev 2012, 13, 2263–2267. [Google Scholar]
- Gao, C.; Zhang, Z.; Liu, W.; Xiao, S.; Gu, W.; Lu, H. Reduced microRNA-218 expression is associated with high nuclear factor kappa B activation in gastric cancer. Cancer 2010, 116, 41–49. [Google Scholar]
- Tie, J.; Pan, Y.; Zhao, L.; Wu, K.; Liu, J.; Sun, S.; Guo, X.; Wang, B.; Gang, Y.; Zhang, Y.; et al. MiR-218 inhibits invasion and metastasis of gastric cancer by targeting the Robo1 receptor. PLoS Genet 2010, 6, e1000879. [Google Scholar]
- Li, B.S.; Zhao, Y.L.; Guo, G.; Zhu, E.D.; Luo, X.; Mao, X.H.; Zou, Q.M.; Yu, P.W.; Zuo, Q.F.; Li, N.; et al. Plasma microRNAs, miR-223, miR-21 and miR-218, as novel potential biomarkers for gastric cancer detection. PLoS One 2012, 7, e41629. [Google Scholar]
- Tseng, C.; Lin, C.C.; Chen, C.N.; Huang, H.C.; Juan, H.F. Integrative network analysis reveals active microRNA and their functions in gastric cancer. BioMed. Central Syst. Biol 2011, 5, 1–11. [Google Scholar]
- Kim, K.; Lee, H.C.; Park, J.L.; Kim, M.; Kim, S.Y.; Noh, S.M.; Song, K.S.; Kim, J.C.; Kim, Y.S. Epigenetic regulation of microRNA-10b and targeting of oncogenic MAPRE1 in gastric cancer. Epigenetics 2011, 6, 740–751. [Google Scholar]
- Suzuki, M.; Suzuki, H.; Minegishi, Y.; Ito, K.; Nishizawa, T.; Hibi, T. H. pylori-eradication therapy increases runx3 expression in the glandular epithelial cells in enlarged-fold gastritis. J. Clin. Biochem. Nutr 2010, 46, 259–264. [Google Scholar]
- Lai, K.W.; Koh, K.X.; Loh, M.; Tada, K.; Subramaniam, M.M.; Lim, X.Y.; Vaithilingam, A.; Salto-Tellez, M.; Iacopetta, B.; Ito, Y.; et al. MicroRNA-130b regulates the tumour suppressor RUNX3 in gastric cancer. Eur. J. Cancer 2010, 46, 1456–1463. [Google Scholar]
- Wang, M.; Li, C.; Yu, B.; Su, L.; Li, J.; Ju, J.; Yu, Y.; Gu, Q.; Zhu, Z.; Liu, B. Overexpressed miR-301a promotes cell proliferation and invasion by targeting RUNX3 in gastric cancer. J. Gastroenterol. 2013. in press. [Google Scholar]
- Saito, Y.; Suzuki, H.; Imaeda, H.; Matsuzaki, J.; Hirata, K.; Tsugawa, H.; Hibino, S.; Kanai, Y.; Saito, H.; Hibi, T. The tumor suppressor microRNA-29c is downregulated and restored by celecoxib in human gastric cancer cells. Int. J. Cancer 2013, 132, 1751–1760. [Google Scholar]
- Saito, Y.; Suzuki, H.; Tsugawa, H.; Imaeda, H.; Matsuzaki, J.; Hirata, K.; Hosoe, N.; Nakamura, M.; Mukai, M.; Saito, H.; et al. Overexpression of miR-142-5p and miR-155 in Gastric Mucosa-Associated Lymphoid Tissue (MALT) lymphoma resistant to Helicobacter pylori eradication. PLoS One 2012, 7, e47396. [Google Scholar]
- Craig, V.J.; Cogliatti, S.B.; Rehrauer, H.; Wundisch, T.; Muller, A. Epigenetic silencing of microRNA-203 dysregulates ABL1 expression and drives Helicobacter-associated gastric lymphomagenesis. Cancer Res 2011, 71, 3616–3624. [Google Scholar]
- Craig, V.J.; Cogliatti, S.B.; Imig, J.; Renner, C.; Neuenschwander, S.; Rehrauer, H.; Schlapbach, R.; Dirnhofer, S.; Tzankov, A.; Muller, A. Myc-mediated repression of microRNA-34a promotes high-grade transformation of B-cell lymphoma by dysregulation of FoxP1. Blood 2011, 117, 6227–6236. [Google Scholar]
|miRNAs||Change||Target mRNAs||Biological process targeted|
|let-7a||↓||RAB40C||Cell cycle progression|
|miR-106b||↓||p21||Cell cycle progression|
|miR-200a||↓||ZEB1, ZEB2||Epithelial to mesenchymal transition|
|miR-17||↑||p21||Cell cycle progression|
|miR-20a||↑||p21||Cell cycle progression|
|miR-146a||↑||IRAK1, TRAF6||Proliferation, Immune response|
|miR-155||↑||IKK-ɛ, SMAD4||Immune response|
↓: miRNA is downregulated in response to H. pylori; ↑: miRNA is upregulated in response to H. pylori; Bold indicates miRNA changes in the same way in gastric cancer.
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