SIRT1 and neoplasm: In contrast to the marginal effects of SIRT1 knockdown, the proliferation of MYC-OFF cells relates to the very low proliferative potential of MYC-OFF cells as shown in Figure 1 F. Furthermore, in the Tet-O-MYC tumor model, it has been reported that cessation of c-Myc expression is sufficient to induce regression of established tumors in vivo[3].