Targeted Drug Regulation on Methylation of p53—BAX Mitochondrial Apoptosis Pathway Affects the Growth of Cholangiocarcinoma Cells

OBJECTIVE: To study the mechanism of 5-aza-2-deoxycytidine (DAC; a methylation inhibitor) on growth of the human cholangiocarcinoma QBC939 cell line. METHODS: A colourimetric assay was used to detect growth of QBC939 cells treated with DAC (0.1 – 100 μmol/l) over 24 h, 48 h and 72 h. Cell morphology was observed by transmission electron microscopy (TEM). The cell cycle and apoptosis were analysed by flow cytometry. Hypermethylation of the promoters of the p53–BAX mitochondrial apoptosis genes cyclin-dependent kinase inhibitor 2A (CDKN2A), death-associated protein kinase 1 (DAPK1) and PYD and CARD domain containing (PYCARD) was detected by methylation-specific polymerase chain reaction, with and without DAC treatment. RESULTS: DAC inhibited QBC939 cell growth with a half maximal inhibitory concentration of 5 μmol/l at 72 h. After DAC treatment, apoptosis was observed by TEM. Flow cytometric analysis of propidium iodide-positive cells demonstrated increased apoptosis of DAC-treated QBC939 cells (43.04%) compared with untreated cells (4.31%). DAC treatment resulted in demethylation of the gene promoters of CDKN2A and DAPK1 in QBC939 cells. CONCLUSIONS: DAC induces apoptosis of QBC939 cells by reactivation of hypermethylated p53–BAX mitchondrial apoptosis genes in cholangiocarcinoma cells.