Female-Biased Activation of the Interferon-γ–Cytotoxic Immune Axis in Epstein–Barr Virus–Positive Gastric Cancer

Objectives: Epstein-Barr virus (EBV)-associated gastric cancer represents a distinct molecular subtype characterized by prominent immune activation.Although sex differences in immune responses have been reported across cancers, their role in shaping the tumor immune microenvironment in EBV-associated gastric cancer remains unclear.This study investigated sex-associated immune gene expression patterns according to EBV status in gastric cancer.Methods: RNA sequencing data from The Cancer Genome Atlas stomach adenocarcinoma cohort were analyzed.Samples were stratified by EBV status and sex.Genome-wide differential expression analysis was performed to identify sex-associated gene expression patterns.Immune-related genes, including interferon (IFN)-γ signaling, cytotoxic immune response, and immune checkpoint-related genes, were further examined, and pathway enrichment analyses were conducted.Findings: Genome-wide analysis revealed distinct sex-associated immune patterns according to EBV status.In EBV-negative tumors, sex-associated differences were modest and broadly distributed.In contrast, EBV-positive tumors exhibited a femalebiased immune expression pattern, with higher expression of cytotoxic effector genes, including GZMB and PRF1, as well as IFN signaling-related genes such as IFNGR2.Pathway enrichment analyses demonstrated enrichment of immune-related processes associated with IFN-γ signaling and cytotoxic activity.CD274 (PD-L1) expression was higher in EBV-positive tumors and showed a female-biased increase, suggesting concurrent activation of immune checkpoint pathways.Conclusions: Sex-associated differences in gastric cancer are strongly influenced by EBV status and are primarily reflected in the host immune landscape.EBV-positive female tumors exhibit coordinated activation of cytotoxic immune responses and immune checkpoint signaling, suggesting a tightly regulated immune environment.These findings highlight the importance of considering both sex and viral status in understanding tumor immunity and may have implications for immunotherapeutic strategies in EBVassociated gastric cancer.