The inhibition of the nutrient-sensing pathway (IGF1-PI3K-mTOR), the activation of the antistress response pathway, and the upregulation of genes involved in DNA repair induced by caloric restriction/fasting prompt normal but not cancer cells to slow down their proliferation and enter a quiescent state, an effect called “differential stress resistance” which protects normal but not malignant cells from the cytotoxicity of anti-tumor drugs. The gene discussed is IGF1; the disease is neoplasm.