However, polyps from SIRT1−/− animals exhibited an increased number of cells expressing the apoptotic marker cleaved caspase-3 (Figure 1E), indicating that the observed reduction in tumor size is attributable to increased apoptosis of SIRT1−/− cells, which is consistent with previously published findings in colon cancer cell lines [15]. This evidence concerns the gene CASP3 and malignant colon neoplasm.