ABCB1 and neoplasm: The tissue levels of vascular endothelial growth factor, a key stimulator of angiogenesis, were markedly reduced in xenograft tumor of SIRT1-overexpressing human sarcoma cells.45 SIRT1 negatively regulated matrix metalloproteinase-9, an enzyme responsible for cancer cell invasion and migration.46 Brouguignon et al. have shown that reveratrol acts as a chemosensitizer by repressing multidrug resistance protein 1 (MDR1) in a SIRT1-dependent manner.47