Copper-linked metabolic stress as a potential contributor to gastric epithelial transformation and metastasis.

Gastric cancer remains a major health burden, and the molecular events that accompany the transition from normal gastric epithelium to malignancy (and the factors that facilitate dissemination) are incompletely defined. In particular, the cellular phenotypes that precede overt transformation and the role of copper-linked metabolic stress in this process are not well understood. We integrated 2 public single-cell RNA-seq datasets of gastric tissues (gene expression omnibus) using canonical correlation analysis-based batch correction and performed quality control and pre/post-integration assessments. Epithelial subclusters were annotated and analyzed by dimensionality reduction, pseudotime inference (monocle; natural-spline model ~sm.ns[Pseudotime]), gene ontology/Kyoto encyclopedia of genes and genomes enrichment, and pathway activity scoring (gene set variation analysis/gene set enrichment analysis). Immune dysfunction/exclusion was evaluated (e.g., tumor immune dysfunction and exclusion). To evaluate genetic evidence, we conducted two-sample Mendelian randomization (MR) using circulating copper as the exposure and benign gastric tumors (FinnGen) and gastric cancer (Genome-Wide Association Study Catalog) as outcomes; standard diagnostics (e.g., F-statistics, I²_GX, pleiotropy/heterogeneity tests, MR-PRESSO) were applied. We identified a putative transitional epithelial phenotype between normal and malignant states, characterized by attenuation of lineage functions (e.g., gastric-acid-related signatures) and enrichment of stress-adaptation programs. Along pseudotime, module scores for stress response to copper ion increased from normal to transition cells and decreased along the tumor branch; metastatic epithelial cells showed attenuated copper-stress signatures together with enhanced motility/tumor programs, consistent with phenotypic convergence across metastatic sites. Primary tumor epithelium exhibited reinforced cell-cycle activity and immune-response attenuation, with immune dysfunction exceeding that of normal epithelium. In MR analyses, genetically proxied variation in circulating copper was positively associated with risk of both benign and malignant gastric tumors, with directions concordant across estimators and diagnostics not indicating major violations (findings consistent with a deleterious causal contribution under standard MR assumptions). Single-cell and genetic evidence prioritize copper-linked metabolic stress and epithelial remodeling (together with immune dysfunction) as testable axes in early gastric epithelial transformation and dissemination. While the patterns are consistent with a causal contribution of higher systemic copper, they do not constitute proof; orthogonal tissue validation and functional perturbation of copper-handling/cuproptosis pathways, alongside expanded genetic analyses (e.g., multivariable/colocalization), are warranted. These insights suggest potential avenues for prevention and targeted intervention.