ABSTRACT
Objective To study the methylation status of the promoter region of several tumor suppressor genes in p53-Bax mitochondrial apoptosis pathway and its role in cholangiocarcinoma. Methods The hypermethylation of the promoter region of tumor suppressors death-associated protein kinase (DAPK), p14, and target of methylation-associoted silencing-1 (TMS1/ASC) were detected by methylation-specific PCR. P53 gene status (exon 5-8 ) were examined by automated sequencing. The relationship between gene mutations and the biological behaviors of cholangiocarcinoma was analyzed. Results Methylation existed in at least one promoter region of tumor suppressor gene in the tumor tissues of 24 patients (66. 7% ). The frequencies of tumor suppressor gene methylation in cholangiocarcinoma were: p14 24%, DAPK 30. 6%, and TMS1/ASC 36. 1%. The frequencies of tumor suppressor gene methylation in the adjacent tissues were: TMS1/ASC 8.3% and DAPK 5.6%. DNA sequencing showed p53 gene mutation was found in 22 of 36 patients (61.1% ), and p53 gene mutation combined with the methylation of tumor suppressor was found in 14 (38.9%) patients, which was significantly correlated with pathologic biology, invasion, and differentiation ( P ＜ 0.05 ). The 1-year, 2-year, and 3-year survival rates were significantly higher in tumor-suppressing genes methylation group ( n = 4) (70%, 43 %, and 28%, respectively)than those in p53 gene mutation group (n = 14) (28%, 5%, and 0%, respectively) (χ2 =9. 060, P =0.03).Conclusions Promoter hypermethylation of p53-Bax mitochondrial apoptosis pathway is a common epigenetic event in cholangiocarcinoma. Although the methylations of TMS1/ASC and DAPK genes in the adjacent tissues are relatively low, they may be informative for the early detection of cholangiocarcinoma. P53 gene mutation combined with the methylation of tumor suppressor may be related with the pathologic biology of cholangiocarcinoma, making the latter trend to be with high malignancy and poor prognosis.