Methylseleninic Acid Regulates Epigenetic Changes In Human Esophageal Squamous Cell Carcinoma Cells

Esophageal squamous cell carcinoma (ESCC) occurs at a very high frequency in certain areas of China. Supplementation with selenium-containing compounds was associated with a significantly lower cancer mortality rate in a study conducted in Linxian, China. Thus, selenium could be a potential anti-esophageal cancer agent. In this study, methylseleninic acid (MSA) could inhibit cell growth of ESCC cells in vitro and in vivo. Upon treated with MSA, the activity of histone deacetylases (HDACs) was decreased and general control nonrepressed protein5(GCN5) was upregulated in ESCC cells. Meanwhile, a significant increase of H3K9acetylation (H3K9ac) was detected. Upregulation of KLF4was also observed after MSA treatment. Additionally, chromatin immunoprecipitation assay showed the acetylated histone H3located more at KLF4promoter region after MSA treatment. Moreover, knockdown of GCN5decreased the protein level of both H3K9ac and KLF4, along with less cell growth inhibition.As we known, NF-E2-related factor2(Nrf2) is an important transcription factor that activates the expression of cellular detoxifyingenzymes. The downstream targets of Nrf2are involved in the detoxication and elimination of reactive oxidants and electrophilic agents by conjugative reactions and enhancing cellular antioxidant capacity. Nrf2expression is largely regulated through the association of Nrf2with Kelch-like ECH-associated protein1(Keap1), which results in cytoplasmic Nrf2degradation. By using microRNA array-based screening, we observed that MSA induced miR-200a expression in ESCC cell lines. We also demonstrated that miR-200a targeted Keapl3’-untranslatedregion (3’-UTR). The reduction of Keap1protein leaded to Nrf2nuclear translocation and activation of Nrf2-dependent ERBB2gene transcription.In conclusion, our results indicated that MSA could inhibit ESCC cell growth, at least in part, by MSA-HDAC/GCN5-H3K9ac-KLF4axis. To our best knowledge, this is the first report that MSA induced acetylation of histone H3at Lys9, which might depend on the activities and the balance between HDACs and HATs. Our study also demonstrated that MSA could activate the Keapl/Nrf2pathway by miR-200a regulation of Keapl in ESCC cells.