Aberrant methylation frequency of TNFRSF10C promoter in pancreatic cancer cell lines

BACKGROUND:A growing body of evidence suggests that many tumors are initiated by both epigenetic abnormalities and gene mutations,which promote tumor progression. Epigenetic abnormalities include changes in DNA methylation and in the modification of histones.This study aimed to assess the status of methylation in the CpG island(CGI)of the tumor necrosis factor receptor superfamily member 10c(TNFRSF10C) with combined bisulfite restriction analysis(COBRA)and to evaluate its role in the progression of pancreatic cancer(PC). METHODS:The methylation status of four PC cell lines was assessed using COBRA and/or bisulfite genomic sequencing (BGS).Changes in methylation and TNFRSF10C expression in PC cell lines before and after treatment with 5-aza-2’-deoxycytidine(5-aza-dC)and/or trichostatin A(TSA)were assessed by BGS and real-time RT-PCR.Apoptosis in the four cell lines was tested by flow cytometry(FCM)and TUNEL assay. RESULTS:The methylation status of the TNFRSF10C promoter was assessed in PC cells(BxPC-3:68.84±8.71%;CFPAC-1:0; PANC-1:96.77±4.57%;SW1990:54.97±7.33%)with the COBRA assay,which was confirmed by the results of BGS.After treatment with 5-aza-dC and/or TSA,apoptosis was induced in PC cells to different degrees,and the levels of TNFRSF10C transcriptional expression in the PC cell lines(except CFPAC-1) increased markedly after 5-aza-dC treatment. CONCLUSIONS:A high frequency of CGI methylation in the TNFRSF10C promoter results in inactivation of the gene and enhancement of tumor growth in most PC cell lines(except CFPAC-1).Inactivation of TNFRSF10C by CGI hypermethylation can play an important role in PC progression and be potentially useful as a diagnostic marker and a new therapeutic approach for PC.