Interleukin-16 Establishes a Th1-dominant Tumor Immune Microenvironment And Potentiates Immune Checkpoint Therapies [scRNA-Seq]

Overcoming immunosuppression in tumor microenvironment (TME) is crucial for the development of novel cancer immunotherapies. In this study, we revealed a previously unrecognized role of IL-16 in shaping anti-tumor immunity. Compared to healthy individuals, cancer patients exhibited impaired production of IL-16, which was associated with inferior patient prognosis. In multiple murine cancer models, IL-16 administration augmented the anti-tumor immune responses and thus restrained tumor growth. Further investigation uncovered that IL-16 potentiated the polarization of T helper 1 (Th1) cells and the production of their effector cytokine IFN-?. Mechanistically, IL-16 inhibited glutamine catabolism by downregulating the expression of glutaminase (GLS) in CD4+ T cells. The establishment of IL-16-dependent Th1 tumor microenvironment further increased the expression of CXCR3 ligands in tumor-associated macrophages (TAMs), thereby improving the therapeutic effectiveness of immune checkpoint blockade (ICB). In cancer patients who received anti-PD1 therapy, higher levels of IL-16 were correlated with better responsiveness. Finally, we found that the impaired production of histamine by mast cells was a contributing factor to the downregulation of IL-16 in TME. Therefore, IL-16 could potentially be utilized as a therapeutic approach to augment anti-tumor immunity, and improve the outcome of ICB therapy in cancer patients. Collectively, our research provided new insights into the biological function of IL-16, emphasizing its potential clinical significance in cancer immunotherapy. Overall design: Fresh breast cancer tissues and the corresponding normal tissues were harvested, cell-specific gene expression was analyzed by scRNA-Seq.