Search Results (426)

Background/Objectives: Fibroblast activation protein (FAP), which is abundantly expressed in cancer-associated fibroblasts (CAFs) across various epithelial malignancies, has emerged as a promising target for molecular imaging and radionuclide therapy. Although several reviews have addressed FAP-targeted diagnostics, a comprehensive synthesis integrating molecular biology, diagnostic performance, and early therapeutic development remains limited. This review summarises the current evidence on radionuclide-labelled FAP inhibitors (FAPIs), with particular emphasis on their diagnostic utility, emerging therapeutic applications, and the structural features that shape their biological behaviour. Methods: A structured literature search was conducted across PubMed, Scopus, and Web of Science, focusing on FAPI-based imaging and therapy. Results: Diagnostic studies consistently demonstrate high tumour-to-background contrast for [⁶⁸Ga]Ga and [¹⁸F]-labelled FAPI radiotracers, particularly in tumours with prominent stromal components such as pancreatic, colorectal, breast, and head and neck cancers. FAPI PET/CT often surpasses [¹⁸F]FDG in lesion conspicuity in the brain, liver, and peritoneum. Therapeutic evidence shows encouraging tumour retention and safety profiles for agents such as [¹⁷⁷Lu]Lu-FAP-2286 and [⁹⁰Y]Y-FAPI-46, while α-emitting radiotracers (e.g., [²²⁵Ac]Ac-FAPI-04) demonstrate potent antitumor effects in preclinical models. Conclusions: Radiolabelled FAPI radiotracers hold significant potential as dual diagnostic and therapeutic agents, particularly for desmoplastic tumours with high CAF content. Nonetheless, clinical evidence remains in its early stages, and substantial questions persist regarding dosimetry, intertumoral variability in FAP expression, and optimal ligand selection for therapy. Continued development of next-generation FAPI constructs, along with well-designed prospective trials, will be crucial in defining the future role of FAPI-based theranostics in oncology. Full article

Background/Objectives: Familial adenomatous polyposis (FAP) is an autosomal dominant disorder caused by pathogenic variants in the adenomatous polyposis coli (APC) gene. Its attenuated form (AFAP) is characterized by fewer colorectal polyps and later onset of colorectal cancer. We aimed to characterize the molecular effects of a novel APC gene variant (NM_000038.6: c.1620_1624delinsT) identified in a patient with AFAP. Methods: A 56-year-old man with the AFAP phenotype underwent germline testing via a multigene NGS panel, which identified a novel APC gene variant (NM_000038.6: c.1620_1624delinsT). In silico analyses predicted disruption of the canonical donor splice site and a frameshift followed by the introduction of a premature stop codon. The transcriptional impact of the identified APC gene variant was investigated by mRNA analysis. Results: mRNA analysis revealed two distinct APC transcripts: the first transcript led to a truncated protein (p.Leu540PhefsTer8), and the second transcript lacked exon 12, resulting in an in-frame 26 amino acid deletion of APC protein (p.Ala517_Gly542del). The transcript lacking exon 12 was more abundant than the transcript with a premature stop codon, likely due to degradation through nonsense-mediated decay. Conclusions: The APC gene variant (NM_000038.6: c.1620_1624delinsT) exhibits a dual transcriptional effect, revealing its pathogenic role in AFAP. This study highlights the diagnostic value of combined DNA–RNA germline testing for improving the clinical classification of novel APC gene variants and their genotype–phenotype correlations in FAP. Full article

Endometriosis is a highly prevalent, chronic gynecological disorder characterized by the ectopic presence of endometrial-like tissue, driving significant morbidity and chronic pelvic pain. Pathologically, it is increasingly recognized as a fibro-inflammatory condition involving extensive tissue remodeling and fibrosis. Current conventional imaging modalities, including ultrasound and MRI, are primarily morphological, while standard molecular imaging using Positron Emission Tomography (PET) tracers has shown limited diagnostic utility. [¹⁸F]Fluorodeoxyglucose (FDG) suffers from high physiological uptake in pelvic organs and inconsistent detection of lesions. Receptor-based tracers like [⁶⁸Ga]Ga-DOTATATE have demonstrated uncertain efficacy. In contrast, radiopharmaceuticals targeting the Fibroblast Activation Protein (FAP) offer a promising molecular approach. FAP is specifically overexpressed by activated fibroblasts present in the stroma of endometriotic lesions, correlating significantly with tissue fibrosis (collagen content) and local immune infiltration (e.g., CD68 macrophages). This comprehensive review analyzes the landscape of radiopharmaceuticals for endometriosis imaging, contrasting the specific limitations of traditional metabolic and receptor agents with the molecular rationale and emerging evidence supporting the use of FAP Inhibitors (FAPI), positioning them as crucial, non-invasive tools for the future diagnosis and management of this challenging disease. Full article

Our Goal is to identify how colorectal cancer (CRC) arises in the single-layered cell epithelium (simple columnar epithelium) that lines the luminal surface of the large intestine. Background: We recently reported that the dynamic organization of cells in colonic epithelium is encoded by five biological rules and conjectured that colon tumorigenesis involves an autocatalytic tissue renewal reaction. Introduction Our objective was to define how altered crypt turnover explains tissue disorganization that leads to adenoma morphogenesis and CRC. Hypothesis: Changes in rate of tissue renewal-based cell polymerization leads to epithelial expansion and tissue disorganization during adenoma histogenesis. Methods: Accordingly, we created a computational model that considers the structure of colonic epithelium to be a polymer of cells and that tissue renewal is autocatalytic. Indeed, self-renewal of stem cells in colonic crypts continuously produces cells that act like monomers to form a polymer of cells (an interconnected, continuous cell sheet) in a polymerization-based process. Our model is a system of nonlinear differential equations that simulates changes in human crypt cell population dynamics. Results: We investigated how changes occur in the proportion of different cell types during adenoma development in FAP patients. The results show premalignant colonic crypts have a decreased rate of tissue renewal due to APC-mutation. Discussion: This slower rate of cell polymerization causes a rate-limiting step in the crypt renewal process that expands the proliferative cell population size. Conclusions: Our findings provide a mechanism that explains how a prolonged rate of crypt renewal leads to tissue disorganization with local epithelial expansion, infolding, and contortion during adenoma morphogenesis.: Full article

Background/Objectives: Radiolabeled fibroblast activation protein inhibitors (FAPIs) are emerging as promising imaging agents assessing fibrotic diseases. This study evaluates [⁶⁸Ga]Ga-DATA^5m.SA.FAPi for imaging pulmonary fibrosis in two mouse models, bleomycin-induced (BLM) and a transgenic (fra-2^tg) model, both displaying characteristics of human pulmonary fibrotic diseases. Methods: In the BLM model, C57BL/6 mice were treated with bleomycin or isotonic sodium chloride (controls) for 4, 5, and 6 weeks, followed by [⁶⁸Ga]Ga-DATA^5m.SA.FAPi PET/CT scans. Fra-2^tg mice and wildtype (WT) littermates underwent at 7, 11, and 18/19 weeks of age a PET/CT scan. The selected timepoints correspond to early, middle, and late disease stages for each model. Imaging was complemented by ex vivo quantification, histological, and immunohistochemical (IHC) analyses. Results: In BLM mice, pulmonary [⁶⁸Ga]Ga-DATA^5m.SA.FAPi uptake showed a trend toward increase as early as 5 weeks of treatment compared with the controls, which was confirmed by ex vivo analysis (BLM: 3.31 ± 0.29%ID/g, n = 5; control: 1.61 ± 0.29%ID/g, n = 4; p = 0.0035). In fra-2^tg mice, no significant differences could be detected. IHC revealed elevated pulmonary FAP expression specifically at early (BLM) and mild (fra-2^tg) disease stages, whereas for BLM, tracer uptake was more pronounced at later stages. Conclusions: Our findings complement and extend observations from previous studies and support the potential of FAPI tracers as molecular imaging agents for pulmonary fibrosis. Full article

Traditionally, scientists tend to approach cancer research in a reductionistic way: aiming at uncovering underlying, separate components in malignant processes. And indeed, great progress has been made by reducing the development of a tumor to single, specific genes and mutations. For instance, familial adenomatous polyposis (FAP) could be reduced to a germline mutation in the Adenomatous Polyposis Coli (APC) gene. The escape of tumor cells from immune surveillance could be reduced to the tumor expression of immune checkpoints, resulting in new approaches in tumor therapy by applying immune checkpoint inhibitors. However, a germline mutation in APC is not 1:1 related to colorectal cancer (CRC), and only some patients respond to immune checkpoint inhibitors. The point here is that biological systems, also comprising cancer, have properties that cannot be reduced to single components. The cooperation of the single components results in new, emergent properties. The outcome of an interaction in a complex network, like the immune system, depends on the many cell types involved and the numerous molecules that interact and activate or inhibit pathways. The way the composing elements are organized is a causal factor in itself for any emergent property. The rise of genomic analysis at the end of the previous century, enabling us to sequence a full genome at the DNA and RNA levels, has initiated an awareness of the need for ‘systems biology’: to consider a full system and how it is organized, in all of its aspects, to understand biological pathways and their outcomes. In this review, we outline the prospects and limitations of systems biology in cancer research and propose a causal framework that integrates upward and downward causation and multiple realizability to understand the emergent properties of tumors that determine the dynamics of tumor development. Full article

Background/Objectives: Pulmonary fibrosis is a progressive and fatal lung disease with limited diagnostic and therapeutic options. Fibroblast activation protein (FAP) has emerged as a promising molecular imaging target for the non-invasive assessment of fibrotic activity. This study aimed to evaluate the diagnostic feasibility of [⁶⁸Ga]Ga-FAP inhibitor (FAPI) and [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography (PET) for imaging pulmonary fibrosis in a mouse model. Methods: A pulmonary fibrosis model was established by intratracheal administration of polyhexamethylene guanidine-phosphate (PHMG-p) to C57BL/6 mice. Fibrosis severity was quantified by the Ashcroft scoring system using hematoxylin and eosin and Masson’s trichrome staining and evaluated by computed tomography (CT) imaging at 7, 14, and 21 days after PHMG-p exposure. PET imaging was performed, and ex vivo biodistribution was assessed after injection of [⁶⁸Ga]Ga-FAPI-04 and [¹⁸F]FDG. Results: Histological analysis and Ashcroft scoring revealed greater fibrosis severity in the PHMG-p-treated group. Western blot analysis demonstrated upregulation of FAP expression after PHMG-p exposure. CT showed increased mean lung density, while [⁶⁸Ga]Ga-FAPI-04 PET revealed significantly elevated pulmonary uptake of [⁶⁸Ga]Ga-FAPI-04 in the PHMG-p-treated group compared with the controls. [¹⁸F]FDG PET imaging also showed higher uptake of [¹⁸F]FDG in the PHMG-p-treated group than in the controls. Ex vivo biodistribution confirmed greater [⁶⁸Ga]Ga-FAPI-04 accumulation in the lungs of PHMG-p-treated mice. Conclusions: [⁶⁸Ga]Ga-FAPI-04 PET serves as a sensitive imaging biomarker for evaluation of fibrotic activity in PHMG-p-induced pulmonary fibrosis and complements [¹⁸F]FDG PET for assessing disease progression and therapeutic response. Full article

Fibroblast activation protein (FAP)-binding radiopharmaceuticals have emerged as promising candidates for both diagnostic and therapeutic applications in oncology due to their selective targeting of cancer-associated fibroblasts (CAFs). This review evaluates the current literature on the therapeutic use of FAP-targeted radiopharmaceuticals in human studies, with a focus on their safety, efficacy, and clinical applicability. Data on radionuclide type, clinical outcome, radiological and metabolic response and adverse events were extracted and summarized. The included studies demonstrated that lutetium-177,yttrium-90 and actinium-225 (in combination therapy) labeled FAP inhibitors exhibit high tumor uptake, with varying but mostly sufficient retention and a favorable safety profile. While mild adverse events such as fatigue, nausea and grade 1 or 2 hematotoxicity were observed, severe toxicities were rare. FAPI-based radionuclide therapies generally show high disease control rates, with promising results from tandem and combination strategies. The heterogeneity of tumor types and small sample sizes limited the generalizability of findings. FAP-targeted radioligand therapy appears to be a promising treatment option for patients with advanced cancer who have exhausted standard therapies. However, further large-scale, prospective clinical trials are necessary to determine optimal dosing strategies, long-term safety and efficacy across different tumor types. Emerging approaches, such as covalently binding FAP-targeted radiopharmaceuticals and the use of alpha-emitters such as actinium-225, lead-212 and bismuth-213, may further enhance treatment outcomes and warrant future investigation. Full article

Cancer-associated fibroblasts (CAFs) are an abundant and diverse cell population within tumor microenvironments of solid tumors. Multiple subtypes of CAFs, defined by molecular and functional markers, have been described in the literature. CAFs contribute to tumor progression by remodeling the extracellular matrix, promoting immune evasion, and supporting angiogenesis and metastasis. Fibroblast activation protein (FAP) is a transmembrane serine protease minimally expressed in normal adult tissues but significantly upregulated in certain subtypes of CAFs across many solid tumors. High levels of FAP have been associated with poor prognosis in various cancers. FAP has increasingly emerged as a promising target for both imaging and therapy. Multiple FAP-targeting strategies, such as small molecules, monoclonal antibodies, drug conjugates, and radiolabeled ligands, are currently being investigated in preclinical and early clinical settings. This review provides a clinically focused overview of CAFs in the tumor microenvironment, highlighting key fibroblast markers, their associations with prognosis across various tumor types, and their utility in radiologic imaging and targeted therapy. We also discuss the potential of non-FAP fibroblast targeting molecules and the clinical rationale for more selective, subtype-specific strategies. By examining fibroblast biology through a radiologist’s lens, we aim to explore the evolving role of stromal targeting in imaging and the treatment of solid tumors. Full article

Bacterial biofilms are critical contributors to chronic infections and antimicrobial resistance. Among the diverse extracellular matrix components, extracellular DNA (eDNA) and amyloid proteins have recently emerged as pivotal structural and functional molecules. Both individually contribute to biofilm stability and antibiotic tolerance, yet their cooperative roles remain underappreciated. This review aims to summarize current knowledge on the origins and functions of eDNA and amyloid proteins in biofilms, to highlight their molecular interactions, and to discuss how their synergistic effects promote biofilm-mediated resistance to antimicrobial agents. A comprehensive literature search was conducted using PubMed, Scopus, and Web of Science databases up to September 2025. Keywords included “biofilm”, “extracellular DNA”, “amyloid proteins”, “matrix”, and “antimicrobial resistance”. Relevant original research and review articles were systematically screened and critically analyzed to integrate emerging evidence on eDNA–amyloid interactions in bacterial biofilms. Current studies demonstrate that eDNA originates primarily from autolysis, active secretion, and host-derived DNA, while amyloid proteins are produced by multiple bacterial species, including Escherichia coli (curli), Pseudomonas aeruginosa (Fap), Bacillus subtilis (TasA), and Staphylococcus aureus (phenol-soluble modulins). Both molecules independently strengthen biofilm integrity and provide protective functions against antimicrobial agents. Importantly, recent evidence shows that eDNA can act as a nucleation template for amyloid fibrillation, while amyloid fibers stabilize and protect eDNA from degradation, creating a dense extracellular network. This synergistic eDNA–amyloid assembly enhances biofilm robustness, impedes antibiotic penetration, sequesters antimicrobial peptides, protects persister cells, and facilitates horizontal gene transfer of resistance determinants. The interplay between eDNA and amyloid proteins represents a central but underexplored mechanism driving biofilm-mediated antimicrobial resistance. Understanding this cooperative network not only deepens our mechanistic insights into bacterial pathogenesis but also highlights novel therapeutic targets. Strategies that disrupt eDNA–amyloid interactions may offer promising avenues for combating persistent biofilm-associated infections. Full article

Background/Objectives: Indeterminate colitis (IC) is an erroneous diagnosis for predominantly colonic inflammatory bowel disease (IBD) when there is a non-definitive foundation of the benchmark for ulcerative colitis (UC) and Crohn’s colitis (CC) after a combined state-of-the-art classification system of clinical, endoscopic, radiologic, and histologic tools are used. This confounds an effective surgical regimen; specifically pouch surgery, “the restorative proctocolectomy with ileal pouch–anal anastomosis (PRC-IPAA)”. Transforming the distinction between UC and CC in otherwise IC into authentic UC and CC requires priority attention when considering a patient’s candidacy for RPC-IPAA. RPC-IPAA is the accepted standard curative surgical procedure in the treatment for UC (and Familial Adenomatous Polyposis (FAP)). Further, inapproximate/incorrect diagnosis and treatment can sustain potential long-term morbidity from inaccurate and unnecessary surgery and cost. Methods: In trying to resolve these diagnostic ambiguities, the current study advances our understanding by showing the expression of human alpha defensin 5 (DEFA5 alias HD5) restricted in the colon crypt mucosal lining areas, and by identifying the cells of the small intestine (ileum) “colonic ileal metaplasia” in CC that may serve as a biomarker to portray/ascertain authentic CC and UC among IC cohorts, with a positive predictive value (PPV) of 96 percent. Results: Hence, the imprecise diagnosis of IC largely would be circumvented. This new diagnostic tool offers instant tangible benefits over existing diagnostic pathways. The journey toward its widespread clinical use is now subject to logistical and regulatory defiance, which all emerging molecular diagnostic technologies inevitably encounter. Conclusions: The aim of this communication is to provide a summary of the currently available diagnostic advances relating to surgical management for IC in clinical settings, and the related challenges. Further, I briefly discuss aspects of its pathophysiology, surveillance, and diagnostic assay development. Full article

Objectives: Early and noninvasive detection of fibrotic interstitial lung disease (fILD) is a critical but unmet clinical necessity. This study aimed to evaluate the feasibility of using ^99mTc-HYNIC-Glu(PEG₄-oncoFAPi)₂ (denoted as ^99mTc-H-PoFP₂), a novel ^99mTc-labeled radiopharmaceutical that targets fibroblast activation protein (FAP), for single-photon emission computed tomography (SPECT) imaging of pulmonary fibrosis in a mouse model and preliminary clinical studies. Methods: ^99mTc-H-PoFP₂ could be conveniently afforded using a kit formula with high radiochemical purity and stability. The binding specificity and affinity of ^99mTc-H-PoFP₂ for FAP were validated by an in vitro binding assay. The in vivo characteristics of ^99mTc-H-PoFP₂ were also determined. Results: ^99mTc-H-PoFP₂ was eliminated quickly via the urinary system, leading to low normal tissue uptake and a high target/background ratio. SPECT imaging demonstrated significantly enhanced uptake of the ^99mTc-H-PoFP₂ in bleomycin-induced fibrotic lung tissues, with visual effects superior to those of normal mice. Thus, a pilot clinical study of ^99mTc-H-PoFP₂ SPECT/CT imaging was conducted in 12 patients diagnosed with fILD. The physiological biodistribution of ^99mTc-H-PoFP₂ in patients was predominantly observed in the kidneys, bladder, liver, and pancreas, with relatively minor accumulation in the thyroid, salivary glands, and spleen. fILD patients exhibited elevated pulmonary ^99mTc-H-PoFP₂ uptake in the affected lung regions. Furthermore, the uptake of ^99mTc-HPoFP₂ demonstrated moderate correlations with the results of pulmonary function tests (PFTs). A higher gender–age–physiology (GAP) index was associated with elevated standardized uptake value maximum (SUVmax) and target-to-background ratio (TBR) values. Conclusions: Collectively, this study demonstrates the potential of ^99mTc-HPoFP₂ for SPECT imaging and assessing fILD by targeting FAP overexpressed in fibrotic lung tissues. This strategy offers new possibilities for noninvasive and precise assessment of pulmonary fibrosis. Full article

Fibroblast activation protein (FAP), a transmembrane serine protease expressed primarily in pathological conditions, plays a pivotal role in tumor progression. Despite extensive studies on FAP in solid tumors, its role in hematologic cancers, particularly lymphoid malignancies, remains underexplored. This study aimed to investigate the level and activity of soluble FAP (sFAP) in pre-therapeutic serum samples from 120 lymphoma patients. We measured sFAP serum levels using time-resolved immunofluorometric assay and sFAP activity with Förster resonance energy transfer assay. In addition, immunohistochemistry was used to analyze intratumoral FAP expression in tissue biopsies from a subset of B-cell lymphoma patients (n = 34). Notably, the results revealed significantly reduced circulating sFAP levels (p = 0.002) and activity (p < 0.001) in aggressive disease subtypes compared with indolent subtypes and healthy individuals. At the time of diagnosis, low sFAP activity correlated with inferior overall survival (both p < 0.001) in patients with the aggressive entities, suggesting altered FAP functionality in these tumors. Interestingly, measuring intratumoral FAP levels revealed an inverse pattern, with diffuse large B-cell lymphoma showing higher tissue FAP localization compared with follicular lymphoma (p < 0.001). These findings provide new insights into the biological and clinical significance of FAP in lymphoid malignancies, particularly highlighting the importance of sFAP activity as a potential prognostic marker in aggressive lymphoid malignancies. Full article

Despite advances in the management of advanced clear cell renal cell carcinoma (ccRCC), robust biomarkers for prognosis and therapeutic response prediction remain elusive. Fibroblast activation protein-α (FAP), a marker of activated cancer-associated fibroblasts (CAFs), has emerged as a potential indicator of tumor aggressiveness and resistance to systemic therapies in various solid tumors. This study evaluated the clinical relevance of stromal FAP expression in a cohort of 137 patients with advanced ccRCC and long-term follow-up. FAP immunohistochemistry (IHC) was performed on primary tumor specimens and correlated with key clinicopathological features, disease-free survival (DFS), overall survival (OS), and radiological response to first-line tyrosine kinase inhibitors (TKIs). A significantly higher percentage of FAP-positive CAFs was observed in primary tumors with high histological grade, extensive local invasion (pT3–4), and advanced clinical stage (NCCN stage III–IV). Stromal FAP expression was associated with shorter DFS and OS. Moreover, tumors lacking FAP expression were more likely to achieve complete response to TKI therapy as defined by RECIST criteria. These findings highlight the potential of FAP IHC as a prognostic and predictive tool in advanced ccRCC and support further clinical validation. Full article

Colorectal cancer (CRC) classification has progressed from consensus molecular subtypes (CMS) to epithelial–intrinsic consensus molecular subtypes (iCMS) and the layered intrinsic subtype-MSI-fibrosis (IMF) system that combines intrinsic state, MSI status, and fibrosis. This article reviews biological underpinnings of iCMS/IMF, their relationships to tumor-microenvironment crosstalk, and how single-cell and spatial transcriptomics refine therapeutic stratification by resolving tumor microenvironment heterogeneity and its impact on fibrosis. Prognostic and therapeutic implications are covered, including PD-1 blockade in MSI-high (MSI-H), MAPK-directed therapy in BRAF-mutant disease, and EGFR targeting in selected RAS wild-type (WT) left-sided tumors, and we suggest decision points specifically informed by the activity of the fibrosis axis. A step-by-step procedure is presented for the analysis of bulk and single-cell RNA and formalin-fixed, paraffin-embedded (FFPE) resources, along with open-source tools and reporting standards to make iCMS/IMF calling reproducible in clinics and trials. Future outlooks are outlined with near-term biomarker–drug hypotheses for microsatellite-stable (MSS)-iCMS3 and high fibrosis tumors and key gaps to close for clinical translation. This review outlines a roadmap for precision medicine in colorectal cancer by leveraging the iCMS/IMF framework to integrate pathology and digital pathology, molecular diagnostics, and therapy mapping with FAP-targeted imaging and therapy. Full article