Myc-mediated inhibition of HIF1a degradation promotes M2 macrophage polarization and impairs CD8 T cell function through lactic acid secretion in ovarian cancer.

Ovarian cancer, the eleventh most prevalent cancer among women and a significant cause of cancer-related mortality, poses considerable challenges. While the Myc oncogene is implicated in diverse cancers, its impact on tumours expressing Myc during immune therapy processes remains enigmatic. Our study investigated Myc overexpression in a murine ovarian cancer cell line, focusing on alterations in HIF1a function. Seahorse experiments were utilized to validate metabolic shifts post-Myc overexpression. Moreover, we explored macrophage polarization and immunosuppressive potential following coculture with Myc-overexpressing tumour cells by employing Gpr132 mice to obtain mechanistic insights. In vivo experiments established an immune-competent tumour-bearing mouse model, and CD8 T cell, Treg, and macrophage infiltration post-Myc overexpression were evaluated via flow cytometry. Additionally, adoptive transfer of OTI CD8 T cells was conducted to investigate antigen-specific immune response variations after Myc overexpression. The findings revealed a noteworthy delay in HIF1a degradation, enhancing its functionality and promoting the classical Warburg effect upon Myc overexpression. Lactic acid secretion by Myc-overexpressing tumour cells promoted Gpr132-dependent M2 macrophage polarization, leading to the induction of macrophages capable of significantly suppressing CD8 T cell function. Remarkably, heightened macrophage infiltration in tumour microenvironments post-Myc overexpression was observed alongside impaired CD8 T cell infiltration and function. Interestingly, CD4 T-cell infiltration remained unaltered, and immune-suppressive effects were alleviated when Myc-overexpressing tumour cells were administered to Gpr132 mice, shedding light on potential therapeutic avenues for ovarian cancer management.