MUC1 expression is regulated by DNA methylation and histone H3 lysine 9 modification in cancer cells

MUC1 is a transmembrane mucin that is highly expressed in various cancers and correlates with malignant potential. Important cancer-related genes such as p16 and E-cadherin are controlled epigenetically; however, MUC1 has been overlooked in epigenetics. Herein, we provide the first report that MUC1 gene expression is regulated by DNA methylation and histone H3 lysine 9 (H3-K9) modification of the MUC1 promoter. The recently developed MassARRAY assay was performed to investigate the DNA methylation status of 184 CpG sites from -2,753 to +263. Near the transcriptional start site, the DNA methylation level of MUC1-negative cancer cell lines (e.g., MDA-MB-453) was high, whereas that of MUC1-positive cell lines (e.g., MCF-7) was low. Histone H3-K9 modification status was also closely related to MUC1 gene expression. Furthermore, MUC1 mRNA expression in MUC1-negative cells was restored by treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine. Our results indicate that DNA methylation and histone H3-K9 modification in the 5' flanking region play a critical role in MUC1 gene expression, and this study defines MUC1 as a new member of the class of epigenetically controlled genes. An understanding of the epigenetic changes of MUC1 may be of importance for cancer patients.