Anti-tumor effect of 5-aza-2'-deoxycytidine by inhibiting telomerase activity in hepatocellular carcinoma cells.
OBJECTIVE
To investigate the effect of the demethylating reagent 5-aza-2'-deoxycitidine (DAC) on telomerase activity in hepatocellular carcinoma (HCC) cell lines, SMMC-7721 and HepG2.


METHODS
The related gene expression in cell lines was examined by real-time reverse transcription-polymerase chain reaction and Western blotting analysis. The telomerase activity was examined by telomeric repeat amplification protocol-enzyme-linked immunosorbent assay and DNA methylation was determined by methylation-specific polymerase chain reaction.


RESULTS
The telomerase activity was significantly reduced in both cell lines treated with DAC, accompanied by downregulation of telomerase reverse transcriptase (hTERT). We also observed the effect of DAC on the methylation status of hTERT promoter and the expression of regulatory genes, such as c-myc, p15, p16, p21, E2F1, and WT1. The methylation status of hTERT promoter could be reversed in SMMC-7721 by DAC, but not in HepG2 cells. However, p16 expression could be reactivated by demethylation of its promoter, and c-Myc expression was repressed in both cell lines. Moreover, DAC could enhance the sensitivity to the chemotherapeutic agents, such as cisplatin, by induction of apoptosis of HCC cells.


CONCLUSIONS
The DAC exerts its anti-tumor effects in HCC cells by inhibiting the telomerase activity.
Tumor Immunology and Gene Therapy Center, Eastern Hepatobiliary Surgery Hospital, The Second Military Medical University, Shanghai 200438, China.
Shuang-Fen
SF
Tao
Chang-Song
CS
Zhang
Xian-Ling
XL
Guo
Yun
Y
Xu
Shan-Shan
SS
Zhang
Jian-Rui
JR
Song
Rong
R
Li
Meng-Chao
MC
Wu
Li-Xin
LX
Wei
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy*; D045744:Cell Line, Tumor / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000037:antagonists & inhibitors*
D000964:Antimetabolites, Antineoplastic; D012333:RNA, Messenger; D000077209:Decitabine; D019098:Telomerase; D001374:Azacitidine