Differential OAT methylation correlates with cell infiltration in tumor microenvironment and overall survival postradiotherapy in oral squamous cell carcinoma patient

Background Given that DNA methylation and tumor microenvironment (TME) are susceptible to radiotherapy, we aimed to figure out specific differential DNA methylation to reflect oral squamous cell carcinoma (OSCC) prognosis and associated effect on TME changes postradiotherapy, performing as an efficient biomarker. Materials and Methods Differentially methylation analysis was performed using data from The Cancer Genome Atlas. Curves of Kaplan-Meier (K-M) survival, cumulative hazard and events, Cox proportional hazards, and linear regression model were conducted to screen and validate differential methylation genes, while multiple regression equation to analyze if ornithine aminotransferase (OAT) methylation correlates with radiotherapy. For correlation between OAT methylation and immune infiltrates, CIBERSORT and ESTIMATE algorithms were performed, following gene set enrichment analysis (GSEA) and ssGSEA analysis to evaluate biological process. Results Compared to normal tissues, only OAT in OSCC was differential significantly by K-M analysis (p = 0.0364). OAT hypermethylation was associated with increased overall survival (hazard ratio: 0.65, p = 0.0358). Radiotherapy correlated with OAT methylation (beta = -0.01, p = 0.0061); most patients with OAT hypermethylation were radiation-sensitive. Hypomethylated OAT correlated with higher cell infiltrations in TME. Neuroactive ligand-receptor interaction was most significantly related to OAT methylation (p = 9.2e-10). Sulfur metabolism was the most significantly in OAT hypermethylation group (p = 0.0041) and RIG-I-like receptor in OAT hypomethylation group (p = 0.0094). Conclusion OAT methylation can serve as a predictor of OSCC prognosis postradiotherapy with potential mechanism by changing cell infiltrations in TME, but further experimental study deserves to carry out confirming the role and mechanism of OAT methylation in OSCC.