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[Effect of telomerase on ginsenoside Rh2-induced differentiation of hepatocarcinoma cell line SMMC-7721].

BACKGROUND & OBJECTIVE
Recently we found that 20 microg/ml of ginsenoside Rh2 (G-Rh(2)) can inhibit growth, and induce differentiation of hepatocarcinoma cell line SMMC-7721. Re-activation of telomerase may play an important role in carcinogenesis, and cellular immortalization. This study was to explore the mechanism of G-Rh(2)-induced differentiation of SMMC-7721 cells by detecting telomerase activity.


METHODS
After treated with 20 mug/ml of G-Rh(2), telomerase activity in SMMC-7721 cells was detected by polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP) coupled with enzyme-linked immune sorbent assay(ELISA); mRNA levels of human telomerase reverse transcriptase (hTERT), and p21 were measured by reverse transcriptase-polymerase chain reaction (RT-PCR); changes of cell cycle, and expression of Cyclin D1, Cyclin E,P16 protein were detected by flow cytometry (FCM).


RESULTS
G-Rh(2) inhibited telomerase activity of SMMC-7721 in a time- dependent manner: the activity decreased from 1.105 to 0.765 (P< 0.01) after 1-day treatment, while from 1.152 to 0.326 (P< 0.01) after treated for 5-day treatment. The mRNA expression of hTERT was significantly reduced by 20 microg/ml of G-Rh(2). Cell cycle assay showed that 20 microg/ml of G-Rh(2) increased the proportion of SMMC-7721 cells in G1 phase, and decreased those in S, and G2/M phases, the increase of G1 phase after 1-day treatment was the most apparent (from 60.85% to 78.53%,P< 0.05). Furthermore,G-Rh(2) weakened the expressions of positive-regulating factors(Cyclin D1,Cyclin E),and increased the expressions of negative-regulating factors (P16 protein, p21 gene) in SMMC- 7721 cells.


CONCLUSIONS
G-Rh(2) may effectively reduce telomerase activity through affecting transcription level of hTERT,and arresting cell cycle progression. The down- regulation of telomerase activity in SMMC-7721 cells may be closely related to G-Rh(2)-induced differentiation.