Telomerase activity in human hepatocellular carcinoma: parallel correlation with human telomerase reverse transcriptase (hTERT) mRNA isoform expression but not with cell cycle modulators or c-Myc expression

Abstract

Background: To explore the possible regulatory mechanisms of telomerase, we examined the telomerase activity (TA), expression of human telomerase RNA (hTR), human telomerase reverse transcriptase (hTERT) mRNA isoforms and cell cycle modulators in human hepatocellular carcinoma (HCC) cell lines (J5, J7) and a normal human immortalized hepatic epithelial cell line (Chang-liver). Methods: The cell lines were chemically synchronized in either G1, G1/S, G2/M or M phases. TA was measured by polymerase chain reaction (PCR)-based telomerase repeat amplification protocol assay. The hTR and hTERT mRNA levels were analyzed by reverse transcriptase–polymerase chain reaction. Western blotting and immunocytochemistry were used to assay the cell cycle modulators. Results: The TA of J5, J7 and Chang-liver cell lines tested was highest in M phase. The expression level of hTERT mRNA associated with the highest TA detected in the M phase of HCC cell lines. Chang-liver expressed markedly less TA and hTERT mRNA than J5 or J7. The elevated TA and expression of hTERT mRNA isoforms in M phase of HCC cell lines did not significantly correlate with that of the cell cycle modulators and c-Myc. Conclusions: The results implicate that regulation of TA is related to hTERT mRNA isoform expression, and that regulation is different between the cell immortalization and tumorigenesis.