Repression of telomerase reverse transcriptase mRNA and hTERT promoter by gambogic acid in human gastric carcinoma cells.
OBJECTIVE
To investigate the effects and potential mechanisms of gambogic acid (GA), a naturally occurring anticancer agent, on the expression and regulation of telomerase in human gastric carcinoma cells.


METHODS
GA-induced inhibition of cell proliferation was evaluated by the commonly employed MTT assay on two human gastric carcinoma cell lines, MGC-803 and SGC-7901. Telomerase activity and hTERT mRNA expression were determined by telomeric repeat amplication protocol-polymerase chain reaction and reverse transcription-polymerase chain reaction, respectively. The hTERT promoter activity was measured by luciferase assay. The expression of c-MYC, an apoptotic gene that modulates the expression of hTERT promoter, was quantified by Western blotting.


RESULTS
The proliferation of human gastric carcinoma cell lines, MGC-803 and SGC-7901, was significantly inhibited with GA treatment. Both telomerase activity and hTERT mRNA expression were notably decreased in cells treated with GA. The activity of hTERT promoter and the expression of c-MYC were also remarkably decreased in GA-treated cells.


CONCLUSIONS
This study demonstrated that GA treatment of human gastric carcinoma cell lines, MGC-803 and SGC-7901, significantly reduced the expression of c-MYC in a time- and concentration-dependent manner accompanied with the down-regulation of the hTERT transcription and the ultimate reduction in telomerase activity. Our results indicate that the hTERT is a target of c-MYC activity and identify a feasible mechanism of GA's potent anticancer activity.
Department of Physiology, China Pharmaceutical University, 24 Tongjiaxian, 210009, Nanjing, China.
Jun
J
Yu
Qing-Long
QL
Guo
Qi-Dong
QD
You
Sen-Sen
SS
Lin
Zhao
Z
Li
Hong-Yan
HY
Gu
Hai-Wei
HW
Zhang
Zi
Z
Tan
Xiaotang
X
Wang
D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000187:drug effects* / Q000378:metabolism; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D010446:Peptide Fragments / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger; D013274:Stomach Neoplasms / Q000201:enzymology; D019098:Telomerase / Q000187:drug effects* / Q000378:metabolism; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism; D044004:Xanthones / Q000494:pharmacology*
D004268:DNA-Binding Proteins; C116115:MYCBP protein, human; D010446:Peptide Fragments; D012333:RNA, Messenger; D014157:Transcription Factors; D044004:Xanthones; C052659:gambogic acid; C437311:telomerase reverse transcriptase (540-548); D019098:Telomerase