[Mechanisms of human telomerase reverse transcriptase RNAi which increases hepatocellular carcinoma cell apoptosis induced by TRAIL].
OBJECTIVE
To 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).


METHODS
Cell 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.


RESULTS
Hepatocellular 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).


CONCLUSIONS
Enhanced 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.
Zhang
Ru-Gang
RG
Department of Gastroenterology, Southwest Hospital, Third Military Medical University, Chongqing 400038, China.
Fang
Dian-Chun
DC
Ning
Xiao-Yan
XY
Wang
Guo-An
GA
D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology*; D034622:RNA Interference; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*
D053221:TNF-Related Apoptosis-Inducing Ligand; C509186:TERT protein, human; D019098:Telomerase; D053181:Caspase 8; D053453:Caspase 9