We studied the potential role of p21 and of p53 in the response to serum-nutrient starvation using the wild type human colorectal cancer cells (HCT116 wt) and its isogenic counterparts deficient for either p21 (HCT116 p21−/−) or p53 (HCT116 p53−/−). The gene discussed is TP53; the disease is colorectal cancer.