title: Demethylation of the hTERT promoter in normal human gastric mucosal epithelial cells followingN-methyl-N'-nitro-N-nitrosoguanidine exposure.
abstract: N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is an alkylating agent that can induce gastric carcinoma. As a well-known human carcinogen, MNNG has been universally recognized as a methylating agent and is believed to act through methylation mechanism. In the present study, the epigenetic status of the human telomerase reverse transcriptase (hTERT) promoter was investigated in MNNG-treated normal human gastric mucosal epithelial cells. After 4 h exposure to MNNG at different concentrations, 6.8 and 68 µM, bisulfite sequencing polymerase chain reaction showed that five methylated cytosines outside the CpG dinucleotides in the 290-bp fragment from the hTERT promoter were demethylated and all the methylated cytosines in CpG dinucleotides remained intact. Furthermore, the epigenetic status of the target region following MNNG exposure was extremely similar to those of the BGC-823, SGC-7901 and MKN-28 lines; the three cell lines from human gastric adenocarcinoma. The result indicates that MNNG-induced demethylation in cytosines outside the CpG dinucleotides may be an early molecular lesion with the potential for impacting malignant transformation and a possible underlying carcinogenic mechanism of MNNG. Thus, it may provide another insight into the mechanisms of MNNG carcinogenesis.
authors: Department of Gastroenterology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang 830054, P.R. China.
authors: Yong-Bo
authors: YB
authors: Cheng
authors: Department of Gastroenterology, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China.
authors: Dian-Chun
authors: DC
authors: Fang
authors: Department of Gastroenterology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang 830054, P.R. China.
authors: Ping
authors: P
authors: Yao
authors: Department of Gastroenterology, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China.
authors: Li-Ping
authors: LP
authors: Guo
authors: Department of Gastroenterology, Southwest Hospital, Third Military Medical University, Chongqing 400038, P.R. China.
authors: Xiao-Yan
authors: XY
authors: Ning
authors: Department of Gastroenterology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi, Xinjiang 830054, P.R. China.
authors: Lei
authors: L
authors: Wang
keywords: N-methyl-N'-nitro-N-nitrosoguanidine; carcinogenesis; demethylation; human gastric mucosal epithelial cell; human telomerase reverse transcriptase