Simvastatin Inhibits Malignant Transformation Following Expression of the <i>Ha-ras</i> Oncogene in NIH 3T3 Fibroblasts

Abstract

In previous studies we have shown that the expression of the transformingHa-ras oncogene in NIH 3T3 fibroblasts stimulates cellular calcium entry, which triggers oscillatory calcium induced calcium release from internal stores. The intracellular calcium oscillations lead to cytoskeletal remodeling by actin stress fiber depolymerization and activation of the Na⁺/H⁺ exchanger thus mediating cell swelling and intracellular alkalosis, both important mitogenic signals. This is evidenced by abrogation of Ha-ras induced growth factor independent cell proliferation by interference with any of these events, i.e. by inhibition of cellular calcium entry or inhibition of the Na⁺/H⁺ exchanger.As shown in this study, simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the key enzyme for cholesterol biosynthesis, is able to prevent these events following the expression of the transforming Ha-ras oncogene. We show, that simvastatin inhibits farnesylation dependent membrane translocation of a CAAX motive bearing yellow fluorescent protein and suppresses Ha-ras stimulated cellular calcium influx, which can be identified as capacitative calcium entry. In addition simvastatin is able to block regulatory volume decrease channels and to suppress the cytoskeletal remodeling, intracellular alkalinization, increase in cell volume and growth factor independent cell proliferation induced by the oncogene.Thus simvastatin is able to prevent crucial cellular events following expression of the transforming Ha-ras oncogene.

Potent inhibition of small-cell lung cancer cell growth by simvastatin reveals selective functions of Ras isoforms in growth factor signalling

“…Intriguingly, H-Ras protein levels were markedly reduced by simvastatin treatment of H-69 SCLC and A549 cells, indicating that lipid modification of H-Ras controls its stability. Simvastatin has been reported to inhibit malignant transformation by the Ha-ras oncogene (Furst et al, 2002), which correlates with the findings presented here. It is conceivable that H-Ras downregulation reflects decreased mRNA translation or increased protein degradation, since there were no changes in H-Ras mRNA levels.…”

Cell Swelling Stimulates Cytosol to Membrane Transposition of ICln

“…6, incubation of NIH 3T3 fibroblasts with purified ICln protein enhances the MEQ quenching rate under isotonic conditions to a value comparable to the rate of hypotonicity-stimulated cells. To test whether an enhanced incorporation of ICln in the cell membrane from the intracellular side also results in an enhanced MEQ quenching, ICln was specifically targeted to the cell membrane by the overexpression of a farnesylated form of the protein (24,25). In these cells the MEQ quench under isotonic conditions is identical in control cells and in ICln-CAAX cells.…”

“…For cell membrane labeling with fluorescent proteins (CFP-Mem and YFP-Mem) the vectors pECFPMem and pEYFPMem (Clontech) were used. To enhance targeting of ICln to the cell membrane, cells were transfected with the pCDNA3YFPCaaX vector (24,25), in which YFP was replaced by ICln (ICln-CAAX). The same vector lacking the ICln and YFP insert was used as a control vector.…”

Inhibition of HMGcoA reductase by atorvastatin prevents and reverses MYC-induced lymphomagenesis

“…36 Statins have been reported to have potent antitumor properties both in vitro and in vivo. [37][38][39][40][41][42][43][44][45][46] Several reports document that statins may prevent different cancers. Most notably, 1 study documented a 50% decrease in the incidence of colon cancer.…”