Fasting Cycles Retard Growth of Tumors and Sensitize a Range of Cancer Cell Types to Chemotherapy

Short-term starvation (STS or fasting) provides protection to normal cells, mice, and possibly patients from a variety of chemotherapy drugs, but the possibility that it may also protect tumor cells renders its translational potential uncertain. Here we show that fasting cycles can be as effective as toxic chemotherapy drugs, and increase chemotherapy efficacy in the treatment of melanoma, glioma, breast cancer, and neuroblastoma. In vitro, STS sensitizes to chemotherapy 15 of the 17 cancer cell lines tested. In combination with chemotherapy STS results in a synergistic 20-fold increase in DNA damage, increased phosphorylation of pro-aging genes AKT and S6 kinase, reduced expression of stress resistance transcription factors FOXO3a and NFkB, elevated superoxide, and activated caspase-3; all changes not observed in normal tissues. Several of these effects are linked to the activity of heme oxygenase 1 (HO-1), whose modulation was sufficient to regulate chemotherapy-dependent cell death in breast cancer cells. These studies suggest that multiple fasting cycles have the potential to replace certain toxic chemotherapy drugs and to sensitize a wide range of tumors to chemotherapy.