Antitumor efficacy of human telomerase reverse transcriptase gene antisense oligonucleotide in pancreatic cancer cells.

Human telomerase reverse transcriptase (hTERT) is the key component of telomerase catalytic activity, and is associated with tumorigenesis. Recent evidence suggests that the down-regulation of hTERT could rapidly induce an antiproliferative effect in tumor cells, independent of the telomere-elongating function of the enzyme. To test the immediate antitumor efficacy of this down-regulation, antisense oligodeoxynucleotides (AS-ODN) targeting hTERT mRNA were transfected into two human pancreatic cancer cell lines in vitro. In both cell lines, single transfection with AS-ODN decreased the level of hTERT mRNA expression in a dose-dependent manner (from 0.05 to 0.2 µM), while transfection with 0.2 µM hTERT AS-ODN for 24 h achieved the maximum down-regulation of hTERT mRNA. Additionally, 0.2 µM AS-ODN significantly reduced telomerase activity in the cell lines. However, after the first transfection with 0.2 µM AS-ODN, almost no inhibition of cell proliferation was observed in either of the lines, while multiple consecutive transfections with the same concentration of AS-ODN resulted in a continuous reduction in cell viability, the significant inhibition of colony formation ability and increased cell apoptotic rates. Cell cycle analysis indicated that hTERT AS-ODN mainly arrested the cell cycle at the G0/G1 phase in the cells. The data validate an antisense oligonucleotide approach to hTERT inhibition therapy in pancreatic cancer cells.