Dual regulation of CXCR6+CD8+ T cells drives immune exhaustion in the progression of prostate cancer [PB-Cre; Pten knockout and WT]

Prostate cancer (PCa) is widely recognized as an immunologically "cold" malignancy, characterized by limited responsiveness to immune checkpoint blockade. To disclose the mechanisms underlying immune exclusion, we performed single-cell RNA sequencing (scRNA-seq) of tumor-infiltrating immune cells from patients with PCa and identified a previously unappreciated subset of CXCR6+CD8+ cytotoxic T lymphocytes (CXCR6+ CTLs). Notably, the abundance of these cells was inversely correlated with Gleason Score (GS), indicating progressive depletion in advanced stages of PCa. Mechanistically, this depletion is modulated by dual converging pathways. On the one hand, reduced infiltration of M1-like macrophages in higher-grade tumors leads to diminished production of CXCL16, thereby impairing the recruitment of CXCR6⁺ CTLs; On the other hand, IL-10 derived from the tumor microenvironment, partly from M2-like macrophages, downregulates CXCR6 expression via the IL10–FOXO1–KLF2 transcriptional axis. SCENIC analysis and further identified KLF2 as a central transcriptional regulator governing CD8⁺ T cell fate, reinforcing its role in T cell dysfunction. Collectively, our findings delineate a multifaceted mechanism of T cell exclusion in advanced PCa and suggest that targeting the transcriptional axis to restore CXCR6⁺ CTL infiltration or sustain CXCR6 expression in CD8+ T cell, when combined with anti-PD1 therapy, may potentiate anti-tumor immunity and surmount resistance to immunotherapy in this disease.