To date, PARP inhibitors, including niraparib, rucaparib and olaparib have been approved by US-FDA to treat cancers, including prostate cancer, breast cancer and ovarian cancer, through disrupting DNA repair and replication pathways.627–629 PARPs-mediated ADP-ribosylation accounts for up to 90% of the cellular intracellular NAD+ consumption, leading to reduced NAD+ availability for sirtuins. This evidence concerns the gene PARP1 and cancer.