Background & objective: Approximately 90% of tumors have telomerase activity, whereas most normal cells do not express telomerase. Telomerase catalytic subunit or human telomerase reverse transcriptase (hTERT) is the main component of telomerase. Telomerase expression is predominantly regulated at the transcriptional level of hTERT. Telomerase, hTERT, and hTERT promoter are closely related. The aim of this study was to investigate the relationship among human telomerase reverse transcriptase (hTERT) promoter activity, hTERT mRNA expression, and telomerase activity in three ovarian cancer cell lines.
Methods: hTERT promoter activity was determined by luciferase assay after the plasmids of pBTdel-279 containing hTERT core promoter were transfected into three ovarian carcinoma-derived cell lines of OVCAR3, SKOV3, 3AO and normal human ovarian epithelial cells. hTERT mRNA expression levels of these cells were determined by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). Telomerase activity was determined by PCR-ELISA (enzyme-linked immunosorbent assay) in above four cells. Immortalized human embryonic kidney cell line HEK293 and the human embryonic lung fibroblasts HELF were used as positive control and negative control, respectively.
Results: The relative luciferase activities of OVCAR3, SKOV3, 3AO and normal ovarian epithelial cells by the hTERT promoter were 31.4%, 20.3%, 17.7%, and 0.3%, respectively, as the luciferase activity of pGL3-control plasmid in each cell line was considered as 100%. The hTERT mRNA relative expression levels of above four cells were 1.30, 1.00, 0.63, and 0, respectively, as SKOV3 expression level was considered as 1. The telomerase activities were 0.580, 0.414, 0.386, and 0.103, respectively, as >0.2 was considered as positive. The hTERT promoter activity, hTERT mRNA expression level, and telomerase activity were specially raised in three ovarian cancer cell lines. The highest levels of hTERT promoter activity, hTERT mRNA expression, and telomerase activity were observed in OVCAR3 cell line, whereas negative in normal ovarian epithelial cells. hTERT promoter activity was closely associated with hTERT mRNA expression level and telomerase activity (P< 0.01,P< 0.02).
Conclusion: hTERT promoter is specially activated in ovarian cancer cells which expresses telomerase. hTERT promoter activity is positively correlated with telomerase activity. Acting as a targeting promoter, hTERT promoter may be applied in gene therapy of ovarian cancer.