Figure 6

Exogenous mevalonate suppressed the inhibitory effects of simvastatin on cell growth by reversing the simvastatin-induced AMPK activation and STAT3 inhibition in HepG2 cells. (a) Mevalonate inhibited simvastatin-induced AMPK activation and p21 enhancement. HepG2 cells were pre-treated with or without mevalonate (3 mM) for 1 h and then treated with 20 μg/ml simvastatin for 12 h. The cells were collected to detect p-AMPK, AMPK, p21 and β-actin protein levels by immunoblotting. (b) Mevalonate blocked simvastatin-induced STAT3 inhibition and Skp2 depletion. HepG2 cells were pre-treated with or without mevalonate (3 mM) for 1 h and then treated with 20 μg/ml simvastatin for 24 h. The cell lysates were harvested to analyze protein levels by immunoblotting using p-STAT3, STAT3, Skp2, p27 and β-actin antibodies. (c) Mevalonate inhibited simvastatin-induced G0/G1 cell cycle arrest. HepG2 cells were pre-treated with or without mevalonate (3 mM) for 1 h, followed by treatment with 20 μg/ml simvastatin for 48 h. The cells were collected for analysis of DNA content by flow cytometry using PI staining. Results are shown as the mean±S.E.M. of three independent experiments. ***P<0.001