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Effect of Telomerase on Ginsenoside Rh_2-Induced Differentiation of Hepatocarcin oma Cell Line SMMC-7721

ZENG Xiao-Li1, TU Zhi-Guang2 1.Clinical Laboratory, An-Zhen Hospital, Capital University of Medical Sciences, Beijing,100029, P.R.China 2.Department of Clinical Biochemistry, Chongqing University of Medical Sciences, Chongqing,400016, P.R.China  
BACKGROUND OBJECTIVE: Recently we found that 20 μg/ml of ginse no side Rh2 (G-Rh2) can inhibit growth,and induce differentiation of hepatocarcino ma cell line SMMC-7721. Re-activation of telomerase may play an important role in carcinogenesis,and cellular immortalization. This study was to explore the m echanism of G-Rh2-induced differentiation of SMMC-7721 cells by detecting tel omerase activity. METHODS: After treated with 20 μg/ml of G-Rh2,telomerase act ivity in SMMC-7721 cells was detected by polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP) coupled with enzyme-linked immu ne sorbent assay(ELISA);mRNA levels of human telomerase reverse transcriptase (h TERT),and p21 were measured by reverse transcriptase-polymerase chain reaction (RT-PCR); changes of cell cycle,and expression of Cyclin D1,Cyclin E,P16 protei n were detected by flow cytometry (FCM). RESULTS: G-Rh2 inhibited telomerase ac tivity 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 significa ntly reduced by 20 μg/ml of G-Rh2. Cell cycle assay showed that 20 μg/ml of G -Rh2 increased the proportion of SMMC-7721 cells in G1 phase,and decreased tho se 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-Rh2 weakened the expressions of positive-regulating factors(Cyclin D1,Cyclin E),and increased th e expressions of negative-regulating factors (P16 protein,p21 gene) in SMMC-77 21 cells. CONCLUSIONS: G-Rh2 may effectively reduce telomerase activity through affecting transcription level of hTERT,and arresting cell cycle progression. Th e down-regulation of telomerase activity in SMMC-7721 cells may be closely rel ated to G-Rh2-induced differentiation.
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