PARP1 and hepatocellular carcinoma: Many DNA repair proteins, such as sphingolipid signaling, TP53, hOGG1, XRCC1, PARP-1, MRE11-Rad50NBS1 (MRN) complex, and ataxia-telangiectasia mutant (ATM) kinase, are frequently mutated in HCC (21).