Single-cell atlas and the role of sex hormones and chromosomes in sex-divergent reprogramming of the tumor microenvironment.

174

Background: Sex bias is pervasive in tumors; however, the contributions of sex chromosomes and hormones to reprogramming the tumor microenvironment (TME) remain insufficiently characterized. Considering the critical impact of the TME on tumor progression and response to immunotherapy, a systematic investigation of its sex-specific features is warranted. Methods: Based on stringent inclusion criteria, we constructed a high-resolution pan-cancer single-cell sequencing atlas comprising a total of 1,831,436 cells by integrating 468 samples from eight types of non-sex-specific solid tumors (282 males and 186 females). After correcting for batch effects, we identified major and minor cellular subsets. Multiple computational approaches were applied to investigate sex-associated differences in cellular composition, gene expression, and signaling pathways. Results: We systematically compared sex-specific TME features across eight common solid malignancies. In male-associated tumors, CD8 ⁺ T cells consistently exhibited markers of functional exhaustion, a bias potentially driven by androgen signaling and loss of the Y chromosome (LOY). In female tumors, skewed X chromosome inactivation (XCI) and estrogenic signaling correlated with enrichment of M2 polarized macrophages; stromal components, including fibroblasts and endothelial cells, modulated immune responses to further reinforce this phenotype. Tumor cells of male origin displayed higher genomic instability and more aggressive phenotypes, with androgen signaling and LOY contributing to the development of a male biased malignant state. Furthermore, LOY in malignant cells may exacerbate CD8 ⁺ T cell exhaustion. Conclusions: Our study uncovers extensive sex specific differences in the TME across multiple cancer types, with the magnitude of bias varying among malignancies. We describe a regulatory axis that links sex chromosomes, hormonal signals and TME interactions to drive CD8 ⁺ T cell exhaustion in males and M2 macrophage polarization in females. These findings underscore the need to include sex chromosome and hormone status as essential biological variables in studies of the tumor microenvironment and the design of immunotherapies.