Claudin (CLDN) 18.2 is a tight-junction protein predominantly expressed in normal gastric epithelium. Malignant transformation can disrupt epithelial cell polarity, resulting in the exposure and overexpression of CLDN18.2 on tumor cell surfaces. This characteristic makes CLDN18.2 a promising therapeutic target in subsets of patients with gastric and gastroesophageal junction (G/GEJ), and pancreatobiliary cancers. The recent approval by the US Food and Drug Administration (FDA) of the anti-CLDN18.2 monoclonal antibody zolbetuximab marks a significant advancement in the management of locally advanced, unresectable, or metastatic HER2-negative, CLDN18.2-positive G/GEJ adenocarcinoma. The increasing adoption and ongoing clinical trials of CLDN18.2-targeted therapies in G/GEJ and pancreatobiliary cancers have intensified the demand for reliable diagnostic testing. These developments underscore the need for accurate, standardized assessment of CLDN18.2 expression to inform patient selection and treatment planning. This review examines the current status, clinical implications, and challenges of CLDN18.2 testing in G/GEJ, as well as its expanding application in pancreatobiliary cancers. Multiple CLDN18.2 antibody clones and immunohistochemical staining platforms are currently utilized across clinical laboratories, each demonstrating variable accuracy, sensitivity, and specificity in detecting CLDN18.2 expression. Furthermore, CLDN18.2 expression is frequently heterogeneous within these cancers. Optimizing the clinical utility of CLDN18.2 testing requires rigorous attention to pre-analytic factors, such as tissue handling, fixation, and selection of representative tumor samples; analytic factors, including assay validation, antibody selection, and consistency in staining procedures; and post-analytic factors, such as scoring methods and clear cutoff criteria for interpretation. Each of these elements critically influences assay performance and reliability. Careful selection and evaluation of tumor samples, particularly in small biopsies or cytology specimens, are essential to ensure accurate assessment. Standardization of all aspects of CLDN18.2 immunohistochemistry, from specimen preparation to interpretation, is necessary to achieve accurate, reproducible, and clinically meaningful results that guide therapeutic decisions for patients with G/GEJ and pancreatobiliary cancers.

BACKGROUND & AIMS:Biliary tract cancers (BTCs) are a group of rare but highly lethal malignancies that include intrahepatic cholangiocarcinoma (iCCA), extrahepatic cholangiocarcinoma (eCCA), and gallbladder carcinoma (GBC). A major challenge in modeling and treating these cancers is their highly heterogeneous mutational landscapes, both within and across subtypes, as well as across geographic and etiological contexts. This heterogeneity necessitates large cohorts to enable robust statistical analyses. Here, we collate and analyze data from more than 30 next-generation sequencing studies to provide a comprehensive overview of BTC mutational patterns and their potential clinical implications. METHODS:Mutation data from 5,123 BTC samples from 13 countries were standardized, focusing on a set of 29 bona fide oncogenes and tumor suppressor genes. We performed statistical analyses to evaluate hypotheses related to mutation prevalence, etiology, co-mutation patterns, and recurrent mutations. RESULTS:This analysis provides robust estimates of mutation prevalence across geographic regions, BTC subtypes, and hepatitis status, highlighting genes whose alteration frequencies vary by anatomical location and etiology. or example, iCCA in Eastern vs. Western hemispheres showed large differences in alteration prevalence for FGFR2, IDH1, KRAS, TP53, CDKN2A, and BAP1, whereas eCCA and GBC exhibited only modest hemispheric differences. We further show that these differences, as well as those observed between iCCA and eCCA, are partly explained by variation in the mutation profiles and prevalences of small- vs. large-duct subtypes. The large sample size also enabled systematic characterization of gene-gene co-occurrence and mutual exclusivity across BTC subtypes, along with a clinically oriented catalogue of recurrent mutations in oncogenes and tumor suppressor genes. CONCLUSION:This integrative cross-study analysis provides a global view of BTC genomics, clarifying how geography, etiology, and anatomical subtype collectively shape driver mutation landscapes. IMPACT AND IMPLICATIONS:Our results provide statistical depth, uncover new mutational relationships, and suggest high-priority avenues for basic and translational research in biliary tract cancer. By integrating data across diverse geographic and etiological contexts, this study highlights how mutation prevalence and co-mutation patterns vary systematically with anatomical subtype, hepatitis status, and region. These findings offer a more nuanced framework for interpreting BTC genomics and underscore the importance of stratified approaches to research and treatment. Collectively, this work establishes a robust foundation for future biological studies, biomarker development, and the design of clinical trials that are tailored to geographic origin, underlying etiology, and specific mutational and co-mutation landscapes, ultimately supporting more precise and effective therapeutic strategies in BTC.

Related to Figure 4: KDM4C depletion increases immune surveillance in vivo.

WDR5-dependent H3K4me3 deposition at regulatory regions proximal to gene transcriptional start sites (TSS).

Related to Figure 5: Effect of TACH107 on KDM4A and KDM4C levels, and on HPNE viability.

DPY30 loss induces long-term anti-tumor immunity.

Spatial biology technologies offer a unique opportunity to link tissue composition with function. However, analytical methods for quantifying and interpreting highly complex spatial data remain limited. We present CROCHET (ChaRacterization Of Cellular HEterogeneity in Tissues), an end-to-end analysis pipeline for construction of spatially resolved cell atlases from raw data covering millions of cells across large sample cohorts. Its modular architecture supports the integration of diverse data modalities and novel analytical methods for image processing and segmentation, spatialomics quantification and downstream analyses. With comprehensive, open-source, user-friendly, interactive, and visual analysis modules, CROCHET aims to democratize spatial omics for a broad community of users.

Irreversible electroporation (IRE) has shown promise for treating pancreatic ductal adenocarcinoma (PDAC), but whether IRE can induce an abscopal effect is not established. We demonstrated that the combination of IRE and anti-PD-1 antibody could trigger robust abscopal effects in preclinical models of metastatic PDAC. Data from multiple in vivo models, RNA-seq, scRNA-seq, and spatial immunofluorescence provide compelling evidence that IRE induced mitochondrial dysfunction and cellular stress, which triggered activation of the cGAS-STING pathway and subsequent systemic antitumor effects. IRE also led to inflammatory response characterized by tumor infiltration of myeloid cells and their polarization toward M1 state, turning immunologically "cold" tumors into "hot" tumors. Moreover, the presence of T cell/B cell clusters in tumors from mice treated with IRE plus αPD-1 and the lack of antitumor efficacy in B cell knockout mice bearing orthotopic murine PDAC tumors indicate that B cells play an important role in IRE-mediated systemic antitumor immunity.

Context.—:Claudin 18.2 (CLDN18.2) is a clinically actionable target in gastric and gastroesophageal junction adenocarcinomas, with patient selection guided by CLDN18.2 immunohistochemistry assay. While surgical specimens are standard for testing, the reliability of cytology specimens for CLDN18.2 assessment remains unclear. Objective.—:To assess the concordance of CLDN18.2 expression between cytology and surgical specimens and to explore the possible causes of discrepancy. Design.—:CLDN18.2 immunohistochemistry was performed on paired cytology and surgical specimens. The diagnostic performance at the cutoff of 75% or greater was evaluated across clinicopathologic variables. Results.—:Positive CLDN18.2 expression was seen in 35% (13 of 37) of surgical and 32% (12 of 37) of cytology cases. Overall, 86% (32 of 37) of pairs were concordant (either positive or negative). At the cutoff of 75% or greater, cytology achieved 77% sensitivity, 92% specificity, 83% positive predictive value, and 88% negative predictive value. Subgroup analysis showed that specimen origin was the strongest determinant of accuracy: concordance was greatest when both cytology and surgical specimens were obtained from gastric primary tumor, with perfect agreement (prevalence-adjusted, bias-adjusted κ [PABAK] = 1.00). In contrast, cases where one or both specimens were derived from metastatic sites showed lower agreement (PABAK = 0.68; bootstrap P < .01). Conclusions.—:Cytology specimens could serve as a reliable source for CLDN18.2 biomarker testing when interpreted at the threshold of 75% or above. Although discrepancies occur in some cases, the findings support the incorporation of cytology into biomarker testing workflows to expand access to CLDN18.2-targeted therapies for patients lacking surgical specimens.

DPY30 interactors across different PDAC cell lines.

DPY30 loss does not alter H3K4me3 deposition.

Related to Figure 6: KDM4C-miniTurboID validation, Heatmaps for H3K36me3 and H3K27Ac ChIPseq in KDM4C KO vs WT AsPC1, and DUSP2 knockdown western panel.

The WRAD core interacts with the replisome machinery.

GFER was identified via pooled CRISPR-Cas9 screening of nuclear-encoded mitochondrial genes library (MITO)

Analysis pipeline of mitochondrial-targeted CRISPR screening reveals GFER as a top candidate gene.

CD8+ T cell activity is essential for GFER depletion-mediated tumor suppression, as demonstrated in CD8-deficient mouse models.

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest malignancies, with a 5-year survival rate of just 13%. While the development and early clinical use of small molecules targeting oncogenic KRAS mutations, key drivers of PDAC, have shown promise, resistance to these targeted therapies remains a significant challenge. We recently identified Syndecan-1 (SDC1), a highly expressed heparan sulfate proteoglycan, as a critical KRAS effector protein that promotes nutrient salvage and tumor growth. Here, we report the development of a human-specific monoclonal antibody (anti-SDC1 mAb) that inhibits PDAC cell proliferation in vitro and suppresses PDAC tumor growth in vivo. Mechanistically, the anti-SDC1 mAb blocks macropinocytosis and induces antibody-dependent cellular cytotoxicity (ADCC). In vivo, anti-SDC1 mAb synergizes with standard chemotherapy, KRAS∗ inhibitors, and immunotherapies, resulting in tumor regression and near-complete response. These findings highlight the anti-SDC1 mAb as a promising therapeutic strategy for PDAC and potentially other KRAS∗ and SDC1-driven tumors.