Systematic inhibitor selectivity between PARP1 and PARP2 enzymes: Molecular implications for ovarian cancer personalized therapy

Human poly(ADP-ribose) polymerases (PARPs) are a class of nuclear enzymes involved in the pathogenesis of diverse gynecologic tumors. The PARP1 and PARP2 are the two most documented members in PARP family, which have been approved as the druggable targets of ovarian and cervical cancers. Selective targeting of the two enzymes with small-molecule inhibitors is a great challenge due to the high conservation in catalytic domain and active site. Here, we investigate the systematic selectivity profile of sophisticated PARP inhibitors between the two enzymes. Computational methods are used to model/optimize the complex structures of inhibitor ligands with PARP1/2 catalytic domains and then to estimate the theoretical Fenzymatic assays exhibit a good consistence with theoretical selectivity over six tested inhibitor samples (r(c)(2) = 0.857). It is revealed that the inhibitor selectivity is conferred from the exquisite difference in the residue composition and structural architecture of both the local activity sites and the whole catalytic domains of the two enzymes. In particular, the TMZ50 and ME0328 show strong selectivity between PARP1 and PARP2, but only the former has a potent activity on the two enzymes, whereas the latter can only inhibit the enzymes moderately. These compounds can be considered as potential lead molecular entities to develop new specific PARP-selective inhibitor drugs for personalized therapy combating gynecologic cancers.