In this study, SIRT1 knockdown by siSIRT1 or treatment of GC cells with the SIRT1 inhibitor, EX527, resulted in the upregulation of FOXO1 and pro-apoptotic Bax, and downregulation of cell cycle promoting factors, Ki67 and Cyclin D1, and anti-apoptotic Bcl-2. The gene discussed is CCND1; the disease is gastric cancer.