HIF-1α and calcium signaling as targets for treatment of prostate cancer by cardiac glycosides

Prostate cancer possesses its unique feature of low proliferation rate and slow growth. Ca²⁺-induced apoptosis is not dependent on cell cycle progression and targeting this pathway could circumvent the problems encountered using current cytotoxic chemotherapies for prostate cancer. Hypoxia-inducible factor 1α (HIF-1α) is another novel cancer drug target and inhibitors of hypoxia-response pathway are being developed. Digoxin and other cardiac glycosides, known inhibitors of the alpha-subunit of sarcolemmal Na ⁺K⁺-ATPase, were recently found to block tumor growth via the inhibition of HIF-1α synthesis. Thus, cardiac glycosides disrupt two important cellular pathways and, therefore, may be useful as an anticancer therapy. This review will focus on HIF-1α and calcium signaling as novel cancer drug targets in prostate cancer. The possible application of digoxin and other cardiac glycosides in cancer therapeutics especially in prostate cancer is discussed.