Abstract

Ovarian cancer is the leading cause of death among gynecological malignancies in the US and the poor outcome of current treatments necessitates the development of novel therapeutic strategies to fight against it. Epidemiological data indicate a positive association between higher latitude and ovarian cancer incidence and mortality rates, suggesting that vitamin D insufficiency may contribute to ovarian cancer development. Recent studies in the authors laboratory showed that multiple ovarian cancer cell lines respond to the active form of vitamin D, 1α,25-dihydroxyvitamin D3, for growth suppression. Mechanistic studies identified vitamin D-regulated genes with established functions in ovarian tumorigenesis as mediators for the growth suppression. While increased p27 protein stability and transcriptional up-regulation of GADD45 are responsible for 1α,25-dihydroxyvitamin D3-induced cell cycle arrest at G1/S and G2/M checkpoints, respectively, the hormone-induced apoptosis in ovarian cancer cells involves the down regulation of the mRNA stability of telomerase catalytic subunit. More importantly, preclinical studies showed that the synthetic vitamin D analog EB1089 effectively suppressed the growth of human ovarian tumor xenografts in mice. The tumor suppression is associated with an increase in apoptotic rate and a decrease in cell proliferation, suggesting that the molecular information can be translated into ovarian tumor suppression in animals. Based on these studies, we conclude that the vitamin D receptor that mediates these anti-tumor effects represents a novel molecular target for the development of new drugs for ovarian cancer. We predict that receptor-based drug discovery will lead to the successful development of more potent and safer vitamin D analogs for the treatment of this deadly disease.

Keywords: Vitamin D, VDR, ovarian cancer, p27, GADD45, telomerase, prevention, therapy