Cardiac glycosides in cancer therapy: from preclinical investigations towards clinical trials

Cardiac glycosides have a long history in the treatment of cardiac disease. However, several preclinical studies as well as two phase I studies have shown that cardenolides may also possess anticancer effects. The mechanisms of these anticancer effects may include intracellular decrease of K+ and increase of Na+ and Ca2+; intracellular acidification; inhibition of IL-8 production and of the TNF-alpha/NF-kappa B pathway; inhibition of DNA topoisomerase II and activation of the Src kinase pathway. To date three cardiac glycosides have been developed for treatment of cancer and were tested in a phase 1 clinical trial to determine dose limiting toxicities and maximum tolerated dose. Future studies of this novel class of anticancer drugs are warranted to determine their possible role in cancer treatment.