Exploration of histone protein γ‐<scp>H2AX</scp> as a prognostic factor in soft tissue sarcomas and its association with biological behavior, immune cell environment and survival in leiomyosarcoma

This study evaluates the H2AX/γ-H2AX expression in soft tissue sarcomas (STS), its implications for biological behavior and immune environment, and its potential as a prognostic biomarker. RNA-Seq data from 237 STS were obtained from The Cancer Genome Atlas project. Patients were stratified by H2AX mRNA expression using a survival-associated cutoff. Differentially expressed genes and pathways as well as immune signatures between H2AX^high- and H2AX^low tumors were identified with DESeq2 analysis, gene set enrichment analyses (GSEA), Enrichr pathway analysis and CIBERSORTx. Tissue microarrays of a different cohort of 291 STS were generated for immunohistochemical staining to assess γ-H2AX protein expression, followed by statistical evaluation. High H2AX mRNA expression was associated with shorter overall survival (OS) in STS (p = 0.02), particularly in leiomyosarcomas (LMS) (p < 0.001), and was a negative prognostic factor in LMS (HR 11.15, p < 0.001). H2AX^high LMS tumors showed upregulation of cell cycle-related pathways, while H2AX^low LMS exhibited increased inflammatory activity, including elevated M1 macrophage signatures and resting mast cell signatures (both p < 0.001). High γ-H2AX protein levels were an independent negative prognostic factor in the total LMS cohort (HR 12.12, p = 0.025) and in the subgroup of non-uterine LMS (HR 153.80, p = 0.013). Consistent with CIBERSORTx analysis, γ-H2AX^low LMS showed higher mast cell infiltration than γ-H2AX^high LMS (p = 0.038). In conclusion, H2AX mRNA and γ-H2AX protein expression are associated with distinct biological behavior, differences in the immune cell environment, and might serve as useful prognostic biomarkers in LMS.