Plant-based drugs primarily used in the treatment of heart failure and arrhythmias have now been found to exert anticancer effects by helping to destroy tumor cells and converting them into a vaccine against remaining cancer cells.

The agents, cardiac glycosides, appear to be exceptionally efficient at inducing “pre-mortem” stress responses in cancer cells, making the cells more vulnerable to the effects of chemotherapy. Moreover, once those cells succumb to treatment, they become vaccines that keep residual tumor cells under control.

As investigators Laurie Menger of Institut Gustave Roussy in Villejuif, France, and colleagues explained in their report in Science Translational Medicine (2012;4[143]:143ra99), some successful chemotherapeutics, particularly anthracyclines and oxaliplatin, induce a type of cell stress and cell death that is immunogenic. The process involved converts the dying cancer cells into a vaccine that stimulates antitumor immune responses.

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Menger’s group noted that retrospective clinical analysis revealed the heart drug digoxin, a cardiac glycoside, to have a positive impact on overall survival in persons with breast, colorectal, head and neck, or liver cancer when administered during chemotherapy. In the current study, the investigators used fluorescence microscopy to identify cardiac glycosides as effective triggers of immunogenic cell death, and to demonstrate how a combination of chemotherapy plus cardiac glycosides could vaccinate mice against living cancer cells.

The researchers plan to test cardiac glycosides in patients with head and neck cancer.