Downregulation of MGMT promotes proliferation of intrahepatic cholangiocarcinoma by regulating p21.

Abstract

Intrahepatic cholangiocarcinoma (ICC) is one of the most devastating cancers of the gastrointestinal tract. It is crucial to determine the accurate prognostic factors and find new therapeutic strategies. Meanwhile, O6-methylguanine-DNA methyltransferase (MGMT) is associated with malignant tumor progression. Thus, further studies are needed to investigate whether MGMT plays a similar role in ICC. Quantitative real-time PCR, western blot, and immunohistochemistry staining were used to detect the expression of MGMT in ICC tissues. The correlations between MGMT expression and clinicopathologic features were analyzed. The cell-proliferation assay and colony-formation assay were applied to evaluate proliferation ability, while methylation-specific PCR were used to detect the methylation status of the MGMT promoter CpG island in ICC tissues and cells. Our study found that the expression of MGMT was decreased in ICC tissues when compared with paired normal tissues. In addition, we demonstrated that MGMT expression was positively correlated with overall survival rates and tumor histological grade. Silencing of MGMT significantly promoted cell proliferation in ICC. Further research showed that silencing of MGMT induced cells to enter S phase by inhibiting p21, p27, and Cyclin E expression, ultimately promoting ICC proliferation. We also demonstrated that the MGMT promoter was highly methylated in ICC, and the levels of MGMT and p21 mRNA increased after DNA demethylation. In addition, the levels of MGMT and p21 protein were positively correlated in ICC tissues. MGMT may play a critical role in carcinogenesis and the development of ICC, and provides a new marker of clinical prognosis and target for ICC treatment.