Differentiation Induced By Panaxydol In HepG2 And SMMC-7721 Hepatocarcinoma Cells

Objectives: To investigate the induced differentiative effects of panaxydol on HepG2 and SMMC-7721 hepatocarcinoma cells.Methods: Effects of panaxydol on cell viability was analyzed by MTT assay. Cell morphology and ultrastructure was examined by light and transmission electron microscope. Alpha-fetoprotein (AFP) in cell culture medium was determined qualitatively and quantitatively with ELISA. The specific activities ofγ-glutamyl transferase (γ-GT) were measured with diazo reaction colourimetry. The alkaline phosphatase (ALP) activities in culture medium were detected with ALP commercial kits. The secretory amount of albumin (Alb) was detected with bromocresol green method. The analysis of cell cycle distribution was performed by flow cytometry. Changes in gene expression of Id1, Id2 and p21 were determined by RT-PCR. Western blot was used to detect the change of p21 and Rb protein expression.Results: Panaxydol inhibited the proliferation of HepG2 and SMMC-7721 cells in dose- and time-dependent manners. After 4-day treatment with 6μmol/L of panaxydol, panaxydol induced the mature and normality of morphology and ultrastructure in HepG2 or SMMC-7721. After treated with 4μmol/L or 8μmol/L of panaxydol, the secretory amount of AFP was significantly reduced, and the specific activities ofγ-GT were remarkably declined; while the secretory amount of albumin and the specific activity of alkaline phosphatase were increased. The cell cycle analysis showed increase of G1 phase cells with the decrease in S phase cells. The expression of regulatory factors IdmRNA was down-regulated and that of negative regulator p21mRNA was up-regulated after exposure to panaxydol. Western blot analysis showed increased expression of p21 protein and tumor suppressor Rb protein.Conclusion: Low dose of panaxydol could efficiently induce the human hepatocarcinoma cells HepG2 and SMMC-7721 differentiation to normal, and its mechanisms may be related with arrest of cell cycle, up-regulation of tumor suppressor p21 and Rb protein expression and down-regulation of IdmRNA expression.