SIRT1 and neoplasm: To determine whether SIRT1 is involved in tumor cell proliferation and tumorigenicity in HCC, we established two stable cell lines (denoted HepG2-SIRT1 and MHCC97H-sh-SIRT1) by transfecting cells with the LV-SIRT1 and LV-sh-SIRT1 lentiviruses, respectively (Figure 2A1).