ATG5 and cancer: Our group further clarified that, in cancer, A549 cells reduced tNOX-NAD+ generation and modulated NAD+-dependent SIRT1 deacetylase to increase p53 acetylation, which results in enhanced cytotoxic apoptosis whereas, in noncancerous MRC-5 cells, it increased the NAD+/NADH ratio and SIRT1 deacetylase activity toward Atg5.