Search Results (844)

The current study describes the synthesis and preliminary anticancer assessment of a novel series of C3/C28-bis-1,2,4-triazolyl-sulfanylacetate-betulin (AP1–5) derivatives to identify potent agents for clinical development. The cytotoxicity of AP1–5 was evaluated using the Alamar blue assay against MCF-7, A375, PANC-1 (cancer cells) and HaCat (human keratinocytes) cells. Moreover, the molecular mechanisms responsible for cytotoxicity were investigated through in vitro (DCFDA/H₂DCDFA assay, caspase-3/7 assay, and morphological analysis) and in silico assays (network pharmacology, molecular docking, molecular dynamics simulation, and ADMET predictions). The result highlighted AP5, containing unsubstituted 1,2,4-triazoles, as the lead derivative of the series with increased potency against MCF-7, with an IC₅₀ value of 7.41 μM compared to its phenyl-substituted analogs (AP1–4). The derivatives induced apoptosis, marked by fragmented nuclei, round cells, disorganized cytoskeletons, and activation of caspases-3/-7 through a ROS-decreasing mechanism. The network pharmacology assessment predicted AP5 may interact with key proteins in the PI3K/Akt pathway, such as MAP2K1, MDM2, IGF1, JAK2, IL2 and FGFR1, as well as ESR1, PGR and MMP2. Molecular docking suggested MMP-2 is the most favorable target for AP5 among the validated proteins, while molecular dynamics simulations supported the predicted AP5–MMP-2 interaction. Moreover, the ADMET profiling of AP5 showed acceptable intestinal absorption, non-glycoprotein-P substrate status, and reduced hepatic metabolism compared to betulin. However, the ADMET analysis also highlighted some potential toxicity risks such as DILI, genotoxicity, carcinogenicity and skin sensitization that need to be further investigated. Altogether, these promising findings support the further exploration of AP5 as a promising drug candidate for breast cancer in vivo to assess its potency and toxicity. Full article

Background: Primary ciliary dyskinesia (PCD) is a rare and genetically heterogeneous disorder that remains underdiagnosed in low- and middle-income countries, largely due to limited access to specialized diagnostic tests. Genetic analysis has become an essential component of PCD diagnosis, particularly where functional and ultrastructural evaluations are unavailable. Methods: We conducted an investigational study including children and adolescents with clinical suspicion of PCD followed at a Brazilian tertiary center. Clinical characterization included detailed phenotyping and calculation of the PICADAR score. Molecular investigation was performed using exome sequencing as a frontline diagnostic approach. Results: Among 27 individuals evaluated, 10 (37%) received a confirmed molecular diagnosis of PCD. An additional 6 (22%) individuals had inconclusive molecular findings, mainly due to variants of uncertain significance (VUS), and were classified as likely PCD based on combined clinical and molecular evidence. Higher PICADAR scores were more frequently observed among individuals with confirmed or likely molecular diagnosis, with 9 of 10 confirmed cases presenting a score above 5. Beyond PCD-associated findings, exome sequencing also enabled the identification of clinically relevant additional diagnoses, including cystic fibrosis, FGFR3-related hypochondroplasia, and ACMG-reportable secondary finding involving BRCA2. Some unresolved cases may also reflect inherent technical limitations of exome sequencing, including restricted sensitivity for copy-number variants, suboptimal coverage of highly homologous or GC-rich regions, and limited detection of deep intronic and other variants. Additional factors include challenges in variant interpretation and incomplete knowledge of disease-associated genes. Conclusions: Frontline exome sequencing is a valuable diagnostic tool for PCD, particularly when integrated with robust clinical phenotyping. Clinical scoring systems such as PICADAR may help prioritize individuals for genetic testing and optimize diagnostic yield in resource-limited settings. Full article

Squamous cell lung cancer (SqCLC) accounts for 20–30% of non-small cell lung cancer (NSCLC) and remains associated with a poorer prognosis compared with adenocarcinoma. Despite advances in treatment, 5-year overall survival for advanced (stage IV) disease remains below 10–15%. Unlike non-squamous NSCLC, SqCLC is characterized by a high tumor mutational burden and complex genomic landscape dominated by alterations in tumor suppressor genes and lineage survival pathways including TP53, CDKN2A, PIK3CA, FGFR1, SOX2, and the NFE2L2/KEAP1 oxidative stress pathway, as well as dysregulation of the NOTCH signaling pathway, but it harbors relatively few actionable oncogenic drivers, resulting in limited treatments for targeted therapy. HER2 alterations can occur by multiple mechanisms, including activating mutations, gene amplifications, and protein overexpression. They comprise a very small percentage of NSCLC, with HER2 mutations reported in approximately 1–3% and HER2 amplifications observed roughly in 2–4%. While HER2 alterations are well characterized in lung adenocarcinoma, the prevalence, genomic context, and clinical significance of HER2 alterations in SqCLC remain incompletely defined. Advances in next-generation sequencing have led to improved ability to detect HER2 alterations and facilitated the development of HER2 targeted therapies. Available treatments for advanced/metastatic SqCLC have been historically limited to platinum-doublet chemotherapy, with immune checkpoint inhibitors such as anti-PD-1/PD-L1 newly emerging in the past decade. Selective HER2 tyrosine kinase inhibitors and HER2 antibody/drug conjugates have shown improved efficacy in HER2-altered NSCLC as shown in DESTINY-LUNG02 and BEAMION LUNG-1 trials; however, most of the enrolled patients had non-squamous histology, with minimal or no SqCLC-specific efficacy data reported. Future progress in HER2-altered SqCLC will require inclusion of SqCLC in HER2 basket trials, incorporation of comprehensive molecular profiling and standardized HER2 testing in squamous histology. This review summarizes the current state of knowledge of HER2 biology in SqCLC and highlights areas for future directions for precision oncology in SqCLC. Full article

Maternal exposure to airborne particulate matter smaller than $2.5$ μm (${\mathrm{PM}}_{2.5}$) has been associated with adverse fetal outcomes, although its effects on intramembranous ossification remain poorly understood. This study evaluated the impact of gestational and pregestational exposure to wood-smoke-derived ${\mathrm{PM}}_{2.5}$ on fetal neurocranial ossification in Sprague–Dawley rats. Females were allocated to four exposure conditions combining filtered air (FA) and non-filtered air (NFA): FA/FA, FA/NFA, NFA/FA, and NFA/NFA. Fetuses were collected at gestational day 21 and analyzed using fetal morphometry, radiography, micro-computed tomography, whole-mount alizarin red skeletal staining, histology, and immunohistochemistry for HIF-1$\alpha$, COL-1, BMP-2, FGF-R1, and TGF-$\beta$. Continuous exposure (NFA/NFA) was associated with reduced fetal weight, shorter crown–rump length, impaired craniofacial mineralization, widened cranial sutural regions, and reduced mineral density, particularly in the occipital and interparietal bones. Histologically, exposed fetuses exhibited abundant osteoid, reduced osteocyte incorporation, and diffuse osteoblastic distribution, consistent with delayed osteogenic maturation. Immunohistochemistry showed increased HIF-1$\alpha$ immunoreactivity, altered TGF-$\beta$ regulation, and reduced COL-1 expression in continuously exposed fetuses, whereas BMP-2 and FGF-R1 showed no significant changes. These findings suggest that maternal exposure to wood-smoke-derived PM_2.5 is associated with delayed fetal neurocranial intramembranous ossification, particularly under continuous exposure. The observed immunohistochemical profile, elevated HIF-1$\alpha$, reduced COL-I, and altered TGF-$\beta$, is consistent with a hypoxia-associated imbalance between extracellular matrix deposition and mineral maturation; however, the underlying mechanistic pathway was not directly functionally tested and should be regarded as a biologically plausible inferential model requiring further experimental validation. Full article

Chronic liver disease (CLD) constitutes a major global health burden, with high morbidity and mortality, limited treatment options for several etiologies, and an urgent need for novel therapeutic targets. Fibroblast growth factor 1 (FGF1) is a unique member of the FGF family capable of binding all four FGFR subtypes, thereby regulating multiple signaling pathways including PI3K/AKT, Ras/MAPK, and PLCγ, which are involved in metabolism, cell survival, proliferation, and tissue repair. Emerging evidence highlights the multifaceted and context-dependent roles of FGF1 in CLD. In drug-induced liver injury (DILI) caused by anti-tuberculosis drugs, acetaminophen, or doxorubicin, FGF1 confers protection by restoring bile acid homeostasis, reducing oxidative stress, inflammation, and apoptosis. In Metabolic dysfunction-associated steatotic liver disease (MASLD), FGF1 ameliorates hepatic steatosis, oxidative injury, and insulin resistance through downregulation of SREBP1, upregulation of PPARα, and activation of Nrf2-mediated antioxidant responses. Conversely, in primary sclerosing cholangitis (PSC), FGF1 aggravates ductular reaction, biliary senescence, and liver fibrosis via upregulation of SASP and TGF-β1, suggesting that inhibition of the FGF1/FGFR axis may be therapeutic. For alcohol-related liver disease (ALD), although direct experimental evidence is lacking, FGF1 is hypothesized to confer protection given its known activities against oxidative stress, lipid dysregulation, and cell death. Despite its promise, the mitogenic potential of FGF1 raises safety concerns; however, N-terminally modified FGF1 analogs (e.g., FGF1Δ) retain metabolic benefits with reduced proliferative activity. Collectively, FGF1 represents a versatile and disease-dependent regulator in CLD, warranting further mechanistic studies, safety evaluations, and development of targeted analogs as a novel therapeutic strategy for difficult-to-treat liver diseases. Full article

Sea cucumbers (Apostichopus japonicus) show fleeing, adhesion, and thanatosis patterns upon exposure to various stressors. However, the molecular mechanisms underlying these contrasting stress response patterns remain largely unknown. In the present study, we performed a transcriptomic analysis of coelomocytes on stressed sea cucumbers to elucidate the potential molecular mechanisms. The RNA-seq results revealed that several matrix metalloproteinase (MMP) family genes, along with HTR4, HRH2, and ADRA1D (which are involved in neuroactive ligand–receptor interactions), were significantly upregulated in the fleeing pattern. These genes may facilitate rapid movement. In the adhesion pattern, PHKA and PGK were significantly downregulated, and the differentially expressed genes (DEGs) were significantly enriched in the longevity regulating pathway, accompanied by downregulation of KRAS and HSPA1. These genes and the pathway may be involved in the reallocation of energy resources during the adhesion pattern. In the thanatosis pattern, DEGs were significantly enriched in the MAPK signaling pathway (including upregulation of ANGPT1 and FGFR1) and in the Rap1 and Ras signaling pathways (with downregulation of key genes: RAPGEF4, RRAS2, and RaLA). These genes potentially contribute to sustaining the thanatosis pattern. These transcriptomic profiles provide novel insights into the distinct molecular signatures underlying each stress response pattern in A. japonicus. Full article

Cholangiocarcinoma (CCA) is an aggressive and molecularly heterogeneous malignancy characterized by a profoundly immunosuppressive tumor microenvironment (TME) and historically limited therapeutic options. Recent advances have redefined the treatment paradigm, with phase III trials establishing chemoimmunotherapy as a standard of care and multi-omic profiling elucidating the interplay between tumor genomics, stromal architecture, and immune regulation. Despite these gains, durable clinical benefit remains confined to a minority of patients, reflecting convergent mechanisms of primary and acquired resistance—including immune exclusion, myeloid-dominant suppression, and genotype-driven “cold” tumor states. In this review, we synthesize emerging insights into the immune landscape of CCA, integrating data from single-cell, spatial, and translational studies to define the cellular and molecular circuits governing immune evasion. Beyond canonical biomarkers such as mismatch repair and microsatellite status, we highlight how spatial organization of immunity—in particular, tertiary lymphoid structures, dynamic myeloid and stromal interactions, and pathway-level features—shape immunotherapy responsiveness. We also examine how tumor-intrinsic alterations, including IDH1 mutation, FGFR2 fusions, KRAS activation, and MTAP loss, define distinct immunologic phenotypes with direct implications for immunotherapeutic response and biomarker-driven patient selection. We evaluate the expanding clinical trial landscape of immunotherapy in CCA and more broadly in BTC, including adoptive cell therapies and cancer vaccines. Together, these advances position CCA as a paradigm of how tumor genotype and microenvironment co-evolve to define immunotherapy sensitivity and resistance. Full article

Gastrointestinal symptoms (GI) (abdominal pain, vomiting, and diarrhea) during the febrile phase of dengue (less than 5 days from fever onset) might indicate prominent innate immune responses. Serum and feces samples from cases with GI symptoms versus those without GI symptoms (n = 20 per group) were analyzed. From these, only the neutrophil extracellular traps (NETs), serum fibroblast growth factor (FGF) 21, and fecal microbiome analyses, but not the routine parameters, endotoxemia, or serum cytokines, were higher in the GI cases than in the non-GI cases. From the in vitro experiments, both lipopolysaccharide (LPS) and the dengue virus (DENV) upregulated the FGF receptor 1 (FGFR1) and cytokines in hepatocytes (HepG2) and THP-1-differentiated macrophages. Meanwhile, LPS and DENV induced NETs in isolated neutrophils from healthy volunteers. Only the starvation protocol, but not LPS or DENV, enhanced supernatant FGF-21 from hepatocytes. Incubation of recombinant FGF-21 in LPS + DENV-activated cells (hepatocytes, macrophages, and neutrophils) attenuated inflammation, as determined by supernatant cytokines and NETs. Hence, abdominal symptoms in dengue during the febrile phase indicate prominent innate immune responses, as detected by NETs and FGF-21 (an acute-phase protein), implying significant hepatic stress with a possible counteracting anti-inflammation. Full article

Multidrug resistance (MDR) is defined as resistance to apparently unrelated drugs with different mechanisms of action, a phenomenon that seriously decreases the efficacy of many anticancer therapeutic regimens. MDR is mainly associated with a high expression of ATP-binding cassette (ABC) transporters, including ABCB1, ABCG2, and members of the ABCC subfamily, which actively extrude many anticancer drugs of various classes out of the cells. Protein kinase inhibitors (PKIs) were developed as therapies targeting oncogenic kinases but later appeared to be both substrates and inhibitors of ABC transporters and thus can potentially reverse MDR. This comprehensive review evaluates how PKIs regulate ABC transporters through three key mechanisms: altering expression, modifying subcellular localization, and inhibiting the efflux function. We evaluated the effect of PKIs that target tyrosine and serine/threonine kinases, such as EGFR/ErbB, JAK, VEGFR, BCR-Abl, ALK, FGFR, MEK1/2, B-RAF, BTK, CDK4/6, MET, RET, PDGFR and SYK. We have collected both computational studies and experimental reports, including functional assays, mechanistic studies of inhibition, and structural approaches that have evaluated PKIs’ effects on ABC transporters. We conclude that although PKIs can be ABC substrates, they mainly inhibit drug efflux, with minimal and context-dependent effects on transporter expression or localization. Full article

Fibroblast growth factor receptor 2 (FGFR2) inhibitors such as pemigatinib are targeted therapies for cholangiocarcinoma with FGFR2 alterations. While generally well tolerated, they are associated with unique adverse events. Calciphylaxis, a potentially fatal vascular calcification disorder, is a rare complication. We present a 43-year-old woman with metastatic intrahepatic cholangiocarcinoma harboring an FGFR2 fusion who developed calciphylaxis after seven months of pemigatinib therapy. Despite drug discontinuation, antibiotics, and multidisciplinary supportive care, she deteriorated rapidly and died from sepsis and advanced disease. Histopathological analysis confirmed dermal and vascular calcifications consistent with calciphylaxis. This case highlights the importance of early recognition of cutaneous lesions in patients on FGFR inhibitors. Prompt cessation of therapy, management of metabolic derangements, and consideration of sodium thiosulfate may be lifesaving. Full article

Umbilical cord mesenchymal stromal cells (UC-MSCs) are a key element of regenerative medicine due to their ability to secrete growth factors that stimulate proliferation and angiogenesis, and modulate the inflammatory response. Despite their widespread use, the influence of the perinatal microenvironment on their biological properties remains poorly understood. The aim of this study was to assess the influence of pH and blood gas parameters in umbilical cord blood on the global transcriptomic profile of UC-MSCs and to analyze the correlation between the metabolic status of the newborn and the expression of key trophic factors: EGF, FGF2, FGFR1, FGFR3, GDNF, HGF, IGF1, NES, NGF, and PGF. Methods: The study was conducted in two stages. In the first phase, transcriptomic screening was performed using Affymetrix HuGene 2.0 ST microarray on cells isolated from three environmental groups defined by cord blood pH: acidic (pH < 7.35), physiological (7.35–7.39), and alkaline (pH ≥ 7.4). In the second phase, the results were validated using qPCR on an expanded study group (N = 50). Gene expression levels (RQ) were related to blood gas parameters (pH, pCO₂, pO₂, cHCO₃) and the presence of clinical features of threatened neonatal asphyxia. Results: Microarray analysis revealed that environmental pH acts as a molecular phenotypic switch. Under low pH conditions (<7.35), a shift in cell profile from proliferative to structural–migratory was observed. Significant overexpression of genes responsible for extracellular matrix (ECM) organization and adhesion (e.g., COMP, DCN, LUM, FMOD) was observed, while pathways related to cell cycle and cell division (↓CDK1, AURKA, TOP2A) were downregulated. qPCR validation confirmed these observations, demonstrating a strong positive correlation between blood pH and the expression of regenerative mediators: FGFR1 (r = 0.28), EGF (r = 0.30), NGF (r = 0.39), and IGF1 (r = 0.30). A negative correlation was also found between carbon dioxide pressure (pCO₂) and the expression of NGF, FGFR1, and EGF. A significant clinical finding was that in newborns diagnosed with threatened asphyxia, EGF, FGFR1, and NGF gene expression was significantly reduced, indicating impaired trophic potential of the cells in response to metabolic stress. Conclusions: These results indicate that cord blood gas parameters are critical regulators of the genetic activity of UC-MSCs. Metabolic and respiratory acidosis not only inhibit the cells’ proliferative potential but also force them into a matrix remodeling mode, permanently modifying their transcriptomic profile. This suggests that the neonatal acid–base status may serve as an objective indicator of the “biological quality” of isolated stromal cells, which has significant implications for their future applications in cell therapies. Full article

Mesenchymal progenitor cells (MPCs) play a significant role in articular cartilage homeostasis and regeneration. Yet, the functional dynamics and molecular characteristics of MPCs may differ significantly across various pathological conditions. Hence, this study comprehensively investigates the biological and molecular characteristics of MPCs isolated from articular cartilage of patients with osteoarthritis (OA) and rheumatoid arthritis (RA), aiming to uncover disease-specific differences that could offer insights into targeted regenerative therapies. Using flow cytometry, gene expression analysis, and in vitro differentiation assays, we assessed the phenotype, growth potential, senescence, cytogenetic instability, and chondrogenic potential to delineate molecular pathways uniquely active in each disease context. Phenotypically, both OA and RA-MPCs retained markers of mesenchymal stem cells (MSCs), but OA-derived MPCs exhibited higher fold expression of progenitor markers (OCT-4, NANOG, SOX-2, and SSEA-4), suggesting a more activated state. Functionally, OA-MPCs demonstrated increased growth kinetics (higher proliferation rate and decreased population doubling time) with a significant shift towards adipogenic lineages (increased fold expression of LPL, AP2, and PPAR-γ). However, there were no differences in the osteogenic and chondrogenic potential. Gene expression analysis revealed upregulation of genes involved in extracellular matrix production and cartilage development (COL2-α1, ACAN, FGFR3, TGF-β3, ANXA6, CNTN1, MATN1, TGF-β1, VIM, and SOX9) in 3D cultures compared with 2D or monolayer cultures. Collectively, these findings demonstrate that, while multipotent MPCs are present in both OA and RA articular cartilage, they can exhibit fundamentally altered biological behaviors and molecular signatures reflective of the local disease microenvironment. Understanding these differences is critical for optimizing cell-based therapeutic strategies tailored to each condition and may facilitate the development of novel interventions targeting endogenous progenitor cells for cartilage repair. Full article

Background: Therapeutic resistance following cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) plus endocrine therapy (ET) represents a key unmet need in hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2−) metastatic breast cancer (mBC). Treatment paradigms have advanced from non-targeted options, such as fulvestrant monotherapy or everolimus-based combinations, to precision medicine strategies, including inhibitors of the PI3K/AKT pathway, oral selective estrogen receptor degraders (SERDs), and novel ER-modulating agents, often guided by biomarkers and molecular surveillance. Methods: This narrative review synthesizes evidence from randomized clinical trials, real-world studies, and biomarker-driven analyses published from 2010 to 2026, with emphasis on next-generation sequencing (NGS)-guided genomic profiling, targeted pathway therapies, and circulating tumor DNA (ctDNA)-based proactive interventions in the post-CDK4/6i setting. This review was conducted and reported in accordance with the SANRA recommendations for narrative reviews. Results: Early second-line standards, including fulvestrant and alpelisib for PIK3CA-mutated tumors, established the basis for biomarker-guided treatment in hormone receptor–positive, HER2-negative metastatic breast cancer. With the widespread use of CDK4/6 inhibitors in the first-line setting, the optimal post-progression strategy has shifted toward molecularly selected combination approaches rather than single-agent endocrine therapy, as endocrine monotherapy has shown limited efficacy in acquired resistance. Multiple randomized studies have demonstrated that adding targeted agents to endocrine therapy improves progression-free survival compared with hormonal therapy alone, supporting combination regimens as the preferred strategy after CDK4/6 inhibitor progression, except in carefully selected patients with low disease burden, indolent biology, or frailty where tolerability is a major concern. Precision-based trials have further refined this approach. Elacestrant improved progression-free survival in ESR1-mutated disease in the EMERALD trial, capivasertib plus fulvestrant demonstrated significant benefit in tumors harboring AKT/PIK3CA/PTEN pathway alterations in CAPItello-291, and inavolisib plus palbociclib and fulvestrant achieved both progression-free and overall survival improvement in PIK3CA-mutated patients with early relapse in INAVO120. Real-world analyses further support the effectiveness of these biomarker-directed strategies across diverse clinical subgroups. Comprehensive genomic profiling has identified multiple resistance mechanisms, including ESR1 mutations, PI3K/AKT/mTOR pathway activation, RB1 loss, and FGFR alterations, which may co-occur and reduce sensitivity to endocrine monotherapy. While ESR1 and PI3K pathway alterations now guide approved therapies, FGFR alterations remain investigational targets, with ongoing trials evaluating selective FGFR inhibitors. Proactive switching approaches evaluated in SERENA-6 and PADA-1 demonstrate that serial circulating tumor DNA (ctDNA) monitoring can detect emergent ESR1 mutations before radiographic progression, providing a clinically actionable lead time for early therapeutic modification and extending endocrine-based disease control by approximately 5 to 7 months. Conclusions: Post-CDK4/6i management increasingly relies on NGS-guided precision approaches, integrating pathway-specific therapies and ctDNA surveillance to tailor sequencing based on resistance profiles, prior ET response, and tumor heterogeneity. Future investigations into novel ER degraders and multi-targeted combinations hold potential to further optimize algorithms, extend non-chemotherapy options, and enhance survival in HR+/HER2− mBC. Full article

Recurrent genetic and chromosomal aberrations drive multiple myeloma (MM) pathogenesis. Among these, the t(4;14) translocation leads to overexpression of fibroblast growth factor receptor 3 (FGFR3) and is associated with poor prognosis. However, therapeutic approaches directly targeting FGFR3-driven myeloma progression remain limited. Here, we investigated the single-agent activity of ponatinib, a multikinase inhibitor, in MM. KMS18 and U266 myeloma cell lines were treated with ponatinib, and apoptosis induction, as well as VEGF and IL-6 secretion, was assessed. RNA sequencing of MM cells revealed pathway alterations induced by ponatinib treatment, which were subsequently validated by Western blot analysis. In vivo, mice inoculated with 5T33 myeloma cells received ponatinib, and survival was monitored. Notably, ponatinib exerted potent single-agent antimyeloma activity in an FGFR3-dependent manner by inducing apoptosis and suppressing VEGF and IL-6 secretion through inhibition of JAK/STAT, PI3K/AKT, and MAPK signaling. In vivo administration prolonged survival in myeloma-bearing mice. Collectively, our findings demonstrate the therapeutic efficacy of ponatinib in FGFR3-expressing MM beyond selective FGFR3 inhibition, suggesting that concurrent suppression of multiple signaling pathways is a critical mechanism of action. These results highlight the therapeutic potential of combined FGFR3-targeted strategies in multiple myeloma and provide a rationale for further clinical investigation. Full article

Fibroblast growth factor receptor 2b (FGFR2b) has become an increasingly important therapeutic target in gastric and gastroesophageal junction cancer, particularly with the clinical development of FGFR2b-directed antibody therapy. However, its translation into routine treatment selection is not straightforward. FGFR2b is usually assessed as a protein biomarker by immunohistochemistry, and a positive result may reflect different biological situations depending on staining intensity, percentage of positive tumor cells, sample type and spatial distribution. In addition, FGFR2b protein expression, FGFR2 amplification, transcript-level activity and true pathway dependency are related but not interchangeable. This review examines FGFR2b-positive gastric cancer from the perspective of biomarker reliability rather than target presence alone. We discuss the biological basis of FGFR2b targeting, the reasons for variability in reported positivity rates, the implications of intratumoral and inter-lesion heterogeneity, the current clinical evidence for FGFR2b-directed and broader FGFR-targeted approaches, and the emerging challenges of safety, resistance and treatment sequencing. Particular attention is given to the gap between detecting FGFR2b and identifying tumors in which this target is sufficiently expressed, representative and biologically relevant to guide therapy. We also consider how FGFR2b should be interpreted alongside HER2, CLDN18.2, immune biomarkers and other receptor tyrosine kinase alterations. As FGFR2b-directed strategies move forward, their success will depend not only on drug efficacy, but also on standardized testing, careful reporting, and selective reassessment when disease biology changes. FGFR2b therefore offers a useful model for how protein biomarkers can be developed in gastric cancer: not as isolated positive-or-negative labels, but as clinically interpreted variables within a changing therapeutic landscape. Full article