A new study recently presented at the annual American Association for Cancer Research (AACR) Meeting in Washington, D.C. has reported that fasting can enhance the effectiveness of chemotherapy by protecting normal cells from damage while sensitizing cancer cells chemotherapy's toxic effects. Chemotherapy's full potential is limited in practice by its toxic side-effects, such as declines in the production of blood cells, heart damage, gastrointestinal damage, and fatigue. Therefore, strategies or interventions that are effective in selectively protecting normal cells, but not cancer cells, could serve to increase the clinical effectiveness of chemotherapy.

The authors previously reported that fasting can selectively protect tumor-bearing mice (but not cancer cells grown in them) from chemotherapy-induced toxicity. In the present study, the authors used dietary and genetic interventions in mice, cell cultures, and yeast to demonstrate that fasting provides selective protection to normal cells and may also sensitize certain cancer cells to chemotherapy or to the severe dietary restriction itself.

Fasting for 48-hours was found to be sufficient to markedly suppress tumor progression in mice models of breast cancer. In one such experiment, fasting alone (without chemotherapy) caused more than a 50% reduction in tumor growth. When fasting was combined with chemotherapy, fasting was found to sensitize cancer cells to the drugs and was shown to further reduce tumor growth up to 90% compared to untreated controls. Laboratory studies using breast cancer cells found similar results: glucose restriction was sufficient to reduce proliferation and also sensitize the cells to both doxorubicin and cyclophosphamid, two different types of drugs commonly used to treat breast cancer. Comparable results were found using mouse models of glioma, neuroblastoma and melanoma. Furthermore, in a metastatic model of melanoma, fasting combined with chemotherapy was shown to increase survival time, and also resulted in fewer organs being affected by metastasis. Given that chemotherapy generally is administered as a combination of drugs, the authors also tested the effect of fasting in combination of several drugs in neuroblastoma-bearing mice. The combination significantly enhanced survival in the mice and was accompanied by reductions in both drug toxicity and metastasis. In further experimentation using yeast, the authors demonstrated that the protection against drug toxicity was due to reduced DNA damage to normal cells. The authors comment that protection of normal cells concurrently with selective sensitization of malignant cells to chemotherapy may prove to be beneficial in cancer treatment.