Effect of Shengmai Yin on the DNA methylation status of nasopharyngeal carcinoma cell and its radioresistant strains

Shengmai Yin (SMY) is a Chinese herbal decoction that effectively alleviates the side effects of radiotherapy in various cancers and helps achieve radiotherapy's clinical efficacy. In this study, we explored the interaction mechanism among SMY, DNA methylation, and nasopharyngeal carcinoma (NPC). We identified differences in DNA methylation levels in NPC CNE-2 cells and its radioresistant cells (CNE-2R) using the methylated DNA immunoprecipitation array and found that CNE-2R cells showed genome-wide changes in methylation status towards a state of hypomethylation. SMY may restore its original DNA methylation status, and thus, enhance radiosensitivity. Furthermore, we confirmed that the differential gene Tenascin-C (TNC) was overexpressed in CNE-2R cells and that SMY downregulated TNC expression. This downregulation of TNC inhibited NPC cell radiation resistance, migration, and invasion. Furthermore, we found that TNC was hypomethylated in CNE-2R cells and partially restored to a hypermethylated state after SMY intervention. DNA methyltransferases 3a may be the key protein in DNA methylation of TNC.