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AIM:Most cancer cells acquire immortal capability bytelomerase activation.The human telomerase reversetranscriptase gene (hTERT) is considered to be the majordeterminant of the enzymatic activity of human telomerase,and the hTERT promoter contains several c-Myc binding sitesthat mediate hTERT transcriptional activation.Few studieshave examined the role of hTERT in hepatocarcinogenesis,and the relationship between c-Myc and telomerase in humanhepatocellular carcinoma tissue is unknown.METHODS:We measured hTERT mRNA levels and c-Myconcoprotein expression in 57 patients with hepatocellularcarcinoma using in situ hybridization and immunohistochemistry,respectively.The transcription regulation of hTERT wasevaluated by transient transfection of pGL3-1375 into thehuman hepatocellular carcinoma cell line J5.To determinethe relationship between c-Myc and the hTERT promoter,a1375-bp DNA fragment encompassing the promoter wasplaced upstream of the luciferase reporter gene andtransiently transfected into the cell line.Two additional hTERTpromoter constructs (-776 and -100 bp region) and an hTERTpromoter-LUC construct containing 2 c-Myc mutations (pGL3-181 MycMT) were also used for luciferase assays.RESULTS:In 30 of 57 cases (52%),hTERT mRNA expressionwas associated with c-Myc protein expression.However,16 of 57 cases (28%) showed strong hTERT mRNA detectionwithout c-Myc protein expression,and 11 cases (19%) showedweak hTERT mRNA expression and strong c-Myc expression.Although luciferase activity was decreased between upstream1 375 bp and 776 bp,there was no significant differencebetween upstream 776 bp and 100 bp.Finally,there wasno significant decrease in activity after transfection of thehTERT promoter-LUC construct.CONCLUSION:The results indicate that c-Myc does notplay a major role in gene regulation of the catalytic subunitof telomerase (hTERT) in human hepatocellular carcinoma. Other regulatory elements or epigenetic phenomena shouldbe further investigated to understand hTERT gene regulationin human hepatocellular carcinoma.
AIM: Most cancer cells acquire immortal capability bytelomerase activation. The human telomerase reversetranscriptase gene (hTERT) was considered to be the major determinant of the enzymatic activity of human telomerase, and the hTERT promoter contains several c-Myc binding site events mediate hTERT transcriptional activation. Few studieshave examined the role of hTERT in hepatocarcinogenesis, and the relationship between c-Myc and telomerase in humanhepatocellular carcinoma tissue is unknown. METHODS: We measured hTERT mRNA levels and c-Myconcoprotein expression in 57 patients with hepatocellular carcinoma using in situ hybridization and immunohistochemistry, respectively The transcription regulation of hTERT wasevaluated by transient transfection of pGL3-1375 into the human hepatocellular carcinoma cell line J5.To determine the relationship between c-Myc and the hTERT promoter, a1375-bp DNA fragment encompassing the promoter wasplaced upstream of the luciferase reporter gene and transient transfect In into the cell line. Two additional hTERT promoter constructs (-776 and -100 bp region) and an hTERT promoter-LUC construct containing 2 c-Myc mutations (pGL3-181 MycMT) were also used for luciferase assays .RESULTS: In 30 of 57 hTERT mRNA expression was associated with c-Myc protein expression. However, 16 of 57 cases (28%) showed hTERT mRNA detection with c-Myc protein expression, and 11 cases (19%) showed weak hTERT mRNA expression and strong c-Myc expression. Yet luciferase activity was decreased between upstream1 375 bp and 776 bp, there was no significant difference between upstream 776 bp and 100 bp. Finaally, there was a significant decrease in activity after transfection of the hTERT promoter-LUC construct. CONCLUSION: The results indicate that c-Myc does notplay a major role in gene regulation of the catalytic subunit of telomerase (hTERT) in human hepatocellular carcinoma. Other regulatory elements or epigenetic phenomena shouldbe further investigated to understandhTERT gene regulation in human hepatocellular carcinoma.