This surprisingly robust finding shows that SIRT1 inactivation, regardless of differences in genetic background (C57BL/6 with some contribution of 129X1/SvJ vs. mixed C57BL/6/129X1/SvJ/CD1) and age of sacrifice (4 months vs. 12 months) in these two studies, leads to marked changes in tumor growth rate. This evidence concerns the gene SIRT1 and neoplasm.