Fluvastatin and cisplatin demonstrate synergistic cytotoxicity in epithelial ovarian cancer cells

Abstract

Objective Statin therapy has been associated with prolonged survival in patients with ovarian cancer. We hypothesized that statins have a cytotoxic effect and that the combination of fluvastatin and cisplatin inhibits cellular proliferation in epithelial ovarian cancer cells. Methods Fluvastatin and cisplatin were examined in CAOV3 and SKOV3 human ovarian cancer cell lines. Cellular proliferation was assessed using MTT assays. Annexin V/propidium iodide (PI) staining was used to discriminate between early and late apoptosis, bromodeoxyuridine and PI staining for cell cycle profiling, and Western blotting for protein expression analysis. Synergy was determined using isobologram analysis. Results Treatment with combination fluvastatin and cisplatin at multiple doses resulted in significantly greater inhibition of proliferation compared to either drug alone. When examining equipotent combinations of fluvastatin and cisplatin to determine potential synergy, a combination index (CI) of 0.66 was identified for CAOV3 cells and a CI of 0.24 for SKOV3 cells indicating synergy. Combination fluvastatin and cisplatin resulted in G2/M arrest, and a significant increase in early apoptotic cells compared to fluvastatin or cisplatin alone. Moreover, supplementation of farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP) demonstrated that GGPP rather than FPP was able to overcome fluvastatin-induced cytotoxicity. Finally, the two-drug combination impaired the expression and modification status of proteins of the Ras pathway. Conclusions These data demonstrate the synergistic cytotoxicity of fluvastatin and cisplatin, through premature apoptosis and cell cycle arrest, with concomitant dysregulation of Ras pathway proteins. Our studies support a plausible therapeutic role for statins in the adjuvant treatment of ovarian cancer.