Analysis of DNA Methylation Status of the Promoter of Human Telomerase Reverse Transcriptase in Gastric Carcinogenesis
Received 2 August 2009; accepted 12 October 2009. published online 29 January 2010.
Background and Aims
Telomerase is expressed in normal somatic cells and reactivated in majority of tumor cells. Human telomerase reverse transcriptase (hTERT), a catalytic subunit of telomerase, is a rate-limiting factor of telomerase activity. Evidence has shown that gastric cancer is the result of genetics and epignomics. DNA methylation is one of the most important research fields in epigenomics. It is one of the mechanisms resulting in gene silencing in carcinogenesis.
Methods
Genomic DNAs were extracted from normal gastric mucosa, precancerous lesions and gastric cancer samples and were modified by sodium bisulfite. The modified genomic DNAs were amplified by PCR with primers that did not contain CpG sites. Each PCR product was sequenced. By matching the sequencing results and the original sequence, the status of each sample was obtained. PCR was carried out to identify hTERT expression.
Results
The promoter of hTERT in gastric cancer was more methylated than in the precancerous lesions and normal gastric mucosa (p<0.05). hTERT was absent in normal gastric mucosa and its positive rate was higher in gastric cancer than in precancerous lesions (p<0.05).
Conclusions
hTERT promoter in gastric cancer was more methylated than in the precancerous lesions and normal gastric mucosa. This may suggest that the degree of methylation of the hTERT promoter was increased during gastric carcinogenesis and may be a potential biological maker in early diagnosis of gastric cancer. During gastric carcinogenesis, expression of hTERT was increased. This may suggest that methylation of hTERT may influence expression of hTERT.
aDepartment of Biochemistry, Tianjin Medical University, Tianjin, China
bTangshan Gongren Hospital of HeBei Meidical University, Tangshan, China
Address reprint requests to: Xin Geng and Weiming Zhang, Department of Biochemistry, Tianjin Medical University, Tianjin, 300070 China; Phone: 0086-22-23542776 Fax: 0086-22-23542776
ABSTRACT