OBJECTIVESTo investigate the mechanisms for human telomerase reverse transcriptase (hTERT) RNA interference (RNAi) in increasing hepatocellular carcinoma cell apoptosis induced by TNF-related apoptosis-inducing ligand (TRAIL).

METHODSCell apoptosis was identified by flow cytometry analysis after annexin V/PI double staining. Expression of apoptosis-related proteins, procaspase-8, -9, -3, Bax, Bcl-2 and hTERT, were identified by Western blotting analysis; telomerase activity and telomere length were detected by telomeric repeat amplification protocol (TRAP) and telomere amount and length assay (TALA) methods.

RESULTSHepatocellular carcinoma cell apoptosis induced by TRAIL were all significantly increased by hTERT RNAi (P less than 0.05). For example, apoptosis rates were enhanced from 5.53% (untransformed) to 10.35% (transformed) in HepG 2 cells and from 14.73% to 77.24% in SMMC 7721 cells after being treated by 100 ng/ml TRAIL for 24 h. Moreover, activation of procaspase-8, -9 and -3 in transformed cells after being treated by TRAIL were all significantly raised (P less than 0.05) in a dose-dependent manner. The expression of procaspase-8, -9 and Bcl-2 were effectively augmented (P less than 0.05), but expressions of Bax and hTERT were strikingly decreased (P less than 0.05). Meanwhile, telomerase activity was apparently suppressed and telomere length was markedly shortened (P less than 0.05). There were no remarkable differences in these effects between control cells and the untransformed cells (P more than 0.05).

CONCLUSIONEnhanced cell apoptosis induced by TRAIL through hTERT RNAi may be related to up-regulation of procaspase-8 and -9 expressions. However the down-regulation of hTERT expression, reduced telomerase activity and shortened telomere length may not be related to expressions of Bcl-2 and Bax.