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[The effect of p21 on transcription of survivin in hepatocellular carcinoma HepG2 cells and its regulation mechanism].

OBJECTIVE
To observe the inhibitory effect of cyclin-dependent kinase inhibitor p21 on regulation of survivin transcription in human liver cancer HepG cells, and explore the related mechanisms.


METHODS
Doxorubicin (DOX) was used to treat HepG cells. Eukaryotic vector pEGFP-C2-p21 was transfected into HepG cells by lipofectamine and positive clones were screened out by G418. The mRNA expression of p21, p53 and survivin were detected by real-time fluorescent quantitative polymerase chain reaction (RQ-PCR). Flow cytometry was used to determine the cell cycle phases, and reverse transcription polymerase chain reaction (RT-PCR) was used to measure the levels of E2F-1 or p300.


RESULTS
After treatment with DOX, the expression of p53 and p21 was increased, whereas that of survivin was reduced during 24 hours of the treatment. After transfection the p21 level was 2100.1-fold or 980.9-fold enhanced in comparison with that in HepG2 cells or HepG2-pEGFP cells. Survivin level was markedly down-regulated to 0.5% or 0.6% relative to that in the other two groups, nevertheless, significant p53 changes were not observed. Overexpression of p21 resulted in G1/G0 phase arrest (F = 31.59, P < 0.01), meanwhile, E2F-1 mRNA or p300 mRNA were less expressed compared with that in the other controls (F(E2F-1) = 125.28, P < 0.05; Fp300 = 46.01, P < 0.01).


CONCLUSION
p21 could be a potential mediator of survivin suppression at transcription level in HepG2 cells, which might be through the block at G1/G0 phase and down-regulation of transcription factors E2F-1 and p300.