Cardiac Glycosides Show Potential for Treating Colorectal Cancer

Cardiac glycosides, a class of drugs used primarily to treat congestive heart failure and abnormal heart rhythms have been evaluated for their potential as anticancer agents.

Investigators at Uppsala University (Sweden) employed a screening procedure aimed at identifying natural products with activity against colon cancer. Among the compounds tested, several cardiac glycosides were shown to be of interest, and five of these were further evaluated in different colorectal cancer cell lines and primary cells from patients.

Results published in the November 6, 2009, online edition of the Journal of Natural Products revealed that the most potent compounds were convallatoxin, oleandrin, and proscillaridin A, while digitoxin and digoxin, which are used in the treatment of cardiac disease, exhibited somewhat lower activity.

Selected cardiac glycosides were tested in combination with four clinically relevant cytotoxic drugs (5-fluorouracil, oxaliplatin, cisplatin, and irinotecan). The combination of digitoxin and oxaliplatin was particularly active, including against the otherwise highly drug-resistant HT29 cell line.

The authors concluded that, "These findings demonstrate that such substances may exhibit significant activity against colorectal cancer cell lines, by mechanisms disparate from currently used anticancer drugs, but at concentrations generally considered not achievable in patient plasma."

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