Effect of simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on alpha-fetoprotein gene expression through interaction with theras-mediated pathway

Background/Aims: The ras proto-oncogene encodes a small GTP-binding protein (Ras) which regulates cell growth and differentiation by relaying signals from the cell surface to the nucleus. In the present study, the role of Ras signal transduction pathway in alpha-fetoprotein (AFP) gene expression was evaluated in HuH-7 human hepatoma cells using simvastatin, a 3-hydroxy-3-m ethylglutaryl coenzyme A reductase inhibitor, which blocks Ras function thr ough inhibition of farnesylation, and the ras(val-12) expression vector. Methods: The HuH-7 cells were treated with simvastatin (10 mu umol/l), or b oth simvastatin and mevalonate (300 mu mol/l), and numbers of viable cells were counted after treatment. To elucidate the effects of simvastatin on AF P gene expression and the interactive effect of simvastatin on Ras signal t ransduction pathway, Northern blotting and transient chloramphenicol acetyl transferase plasmid transfection assays were performed. Results: Cell growth was inhibited by simvastatin, and this growth inhibiti on was restored by addition of mevalonate, Levels of AFP mRNA but not album in mRNA were elevated by simvastatin in a dose-dependent manner (1-10 mu mo l/l). AFP promoter and enhancer activities were stimulated by simvastatin, In contrast, both activities were repressed by transfection with the ras(va l-12)expression vector. The ras(val-12)-mediated repression was restored by simvastatin and returned to the repressed level by simvastatin plus mevalo nate. Conclusions: These results indicate that the Ras signal transduction pathwa y functions to down-regulate the AFP gene transcription in human hepatoma c ells.