RAD001 inhibits human ovarian cancer cell proliferation, enhances cisplatin-induced apoptosis, and prolongs survival in an ovarian cancer model

Abstract

Purpose: mTOR (mammalian target of rapamycin) plays a central role in regulating cell growth and cell cycle progression and is regarded as a promising therapeutic target. We examined whether mTOR inhibition by RAD001 (everolimus) is therapeutically efficacious in the treatment of ovarian cancer as a single agent and in combination with cisplatin.

Experimental design: Using four human ovarian cancer cell lines, we determined the effect of RAD001 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Western blot, and apoptosis assays. We evaluated the association between phospho-AKT/mTOR activity and RAD001 sensitivity. We also determined the effect of RAD001 on tumor growth and malignancy using mice inoculated with human ovarian cancer cells.

Results: RAD001 markedly inhibited cell proliferation of human ovarian carcinoma cells with high AKT activity (OVCAR10 and SKOV-3), but the effect was minimal in cells with low AKT activity (OVCAR4 and OVCAR5). Sensitivity to RAD001 was independent of p53 expression. RAD001 inhibited the phosphorylation of downstream 4E-BP1 and p70S6 kinase and attenuated the expression of Myc. RAD001 also attenuated the expression of HIF-1 alpha and vascular endothelial growth factor, important factors in angiogenesis and tumor invasiveness. RAD001 enhanced cisplatin-induced apoptosis in cells with high AKT/mTOR activity, with minimal effect in cells with low AKT-mTOR activity. Mouse xenografts of SKOV-3 cells revealed that RAD001 inhibits tumor growth, angiogenesis, and i.p. dissemination and ascites production and prolongs survival. Moreover, treatment with RAD001 significantly enhanced the therapeutic efficacy of cisplatin in vivo.

Conclusion: These results indicate that RAD001 could have therapeutic efficacy in human ovarian cancers with hyperactivated AKT/mTOR signaling.