TP53 and neoplasm: The regulation of autophagy by p53 has been shown to promote tumor cell survival under conditions of chronic nutrient deprivation (Scherz-Shouval et al., 2010), and p53 protects cancer cells against treatment with metformin, an inhibitor of mitochondrial respiratory chain complex I (Buzzai et al., 2007), although a recent study did not show enhanced sensitivity of p53−/− tumors to the mitochondrial inhibitor phenformin (Shackelford et al., 2013).