Epithelial YPEL3 Modulates CD8 + T‐Cell Infiltration and Tumor Progression Through CREB1–CXCL16 Signaling in HNSCC

ABSTRACT Yippee‐like 3 (YPEL3) has been implicated in the regulation of apoptosis, proliferation, and invasion in various cancers, but its role in head and neck squamous cell carcinoma (HNSCC) remains unclear. Here, we integrated pan‐cancer data, TCGA/GEO transcriptomes, DNA methylation profiles, and single‐cell RNA sequencing to explore YPEL3's expression, prognosis, and immune relevance in HNSCC. YPEL3 was downregulated in tumor tissues and correlated with better overall survival, particularly in advanced‐stage patients. Functional assays confirmed that YPEL3 suppressed proliferation, migration, and invasion while promoting apoptosis in vitro; its knockdown accelerated tumor growth in vivo. Bulk transcriptomics and TIMER analysis revealed that high YPEL3 expression was associated with increased stromal and immune infiltration, including CD8 + T cells. Single‐cell analysis identified an epithelial subcluster (Epi.C3) enriched for YPEL3, expanded in tumors, and linked to poor prognosis. Mechanistically, YPEL3‐high epithelial cells secreted CXCL16, interacting with CXCR6 on CD8 + T cells to promote immune engagement. YPEL3 regulated CXCL16 via CREB1 but not TFAP2C. Co‐culture assays showed that epithelial YPEL3 modulated the CXCL16–CXCR6 axis in T cells. In vivo, YPEL3 loss was associated with reduced CD8 + T‐cell infiltration and impaired CD8 + T‐cell effector function, as indicated by decreased Granzyme B, Perforin, IFN‐γ, and TNF‐α. Together, these findings identify YPEL3 as a tumor suppressor and an important mediator of epithelial–immune crosstalk in HNSCC, linking epithelial differentiation‐associated states to antitumor immunity through the CREB1/CXCL16/CXCR6 axis.