The Inhibitory Effects of HYDAMTIQ, a Novel PARP Inhibitor, on Growth in Human Tumor Cell Lines With Defective DNA Damage Response Pathways.

The poly(ADP-ribose) polymerase (PARP) enzymes play key roles in the regulation of cellular processes (e.g. DNA damagerepair, genomic stability). It has been shown that PARP inhibitors (PARPIs) are selectively cytotoxic against cells with dysfunctions in genes involved in DNA repair mechanisms (synthetic lethality). Drug induced PARP inhibition potentiates the activity of anticancer drugs such as 5-fluorouracil in enhancing DNA damage, whose repair involves PARP1 activity.The aim of this study was to evaluate the growth inhibitory effects of a novel PARPI, HYDAMTIQ, on human tumor cell lines characterized by different features with regard to DNA damage response pathways (BRCA mutational status, microsatellite status and ATM expression level) and degree of sensitivity/resistance to 5-fluorouracil.HYDAMTIQ showed more potent cell growth inhibitory activity in a BRCA2 mutant cell line (CAPAN-1) compared with wild-type cells (C2-6, C2-12, C2-14 CAPAN-1 clones and MCF-7). No statistically significant difference was observed after HYDAMTIQ exposure between cells with different MS status or different MRE11 mutational statusHYDAMTIQ induced greater antiproliferative effects in SW620 cells expressing low level of ATM than in H630 cells expressing high level of ATM. Finally, the combination of HYDAMTIQ and 5-fluorouracil exerted a synergistic effect on the inhibition of SW620 cell growth and an antagonistic effect on that of H630 cell growth. Our results show that the novel PARP inhibitor HYDAMTIQ potently inhibits the growth of human tumor cells with defective DNA damage response pathways and exerts synergistic cytotoxicity in combination with 5-fluorouracil. These data provide relevant examples of synthetic lethality and evidence for further development of this novel PARPI.