Taken together, our results show that enterocyte-specific inactivation of SIRT1 reduces tumor load in the intestines of APC+/min mice by decreasing both overall tumor size and the number of larger tumors, and they suggest that SIRT1 acts as a tumor promoter by suppressing apoptosis of tumor cells in this mouse model, through mechanisms that include both activation of Wnt signaling pathway and inhibition of p53 activity. The gene discussed is TP53; the disease is neoplasm.