Sodium butyrate suppresses endometrial cancer cell growth by inhibiting thymidylate synthase and reprogramming pyrimidine metabolism

Endometrial cancer (EC) is the most common gynecologic malignancy, yet effective therapies for advanced and recurrent disease remain limited. Sodium butyrate (NaB), a gut microbiota-derived short-chain fatty acid (SCFA) with known anticancer activity, remains poorly understood in EC. In this study, we investigated the anticancer effects of NaB in two EC cell lines, HEC1A and AN3CA. NaB dose-dependently inhibited cell viability, colony formation, and migration in both cell lines, with HEC1A cells exhibiting greater sensitivity. NaB differentially modulated epithelial-mesenchymal transition (EMT)-related markers between the two cell lines. NaB markedly induced apoptosis in HEC1A cells, whereas AN3CA cells showed resistance to apoptotic cell death, despite mitochondrial membrane depolarization occurring in both cell lines. Cell cycle analysis revealed subG1-accumulation in HEC1A cells and G1 phase arrest in AN3CA cells. Notably, NaB potently suppressed thymidylate synthase (TS) at both mRNA and protein levels in both cell lines, representing the first demonstration of TS suppression by NaB in EC. NaB also broadly reprogrammed pyrimidine metabolism by downregulating de novo synthesis enzymes while upregulating salvage pathway components. Taken together, these findings suggest that TS suppression and pyrimidine metabolic reprogramming are important components of the in vitro response of EC cells to NaB. These results provide mechanistic insight into the metabolic effects of NaB in EC and support further investigation of this pathway in pharmacologically relevant and locally applicable therapeutic contexts.