Poly (ADP) Ribose Glycohydrolase Can Be Effectively Targeted in Pancreatic Cancer.

Patients with metastatic pancreatic ductal adenocarcinoma (PDAC) have an average survival of less than 1 year, underscoring the importance of evaluating novel targets with matched targeted agents. We recently identified that poly (ADP) ribose glycohydrolase (PARG) is a strong candidate target due to its dependence on the pro-oncogenic mRNA stability factor HuR (ELAVL1). Here, we evaluated PARG as a target in PDAC models using both genetic silencing of PARG and established small-molecule PARG inhibitors (PARGi), PDDX-01/04. Homologous repair-deficient cells compared with homologous repair-proficient cells were more sensitive to PARGi in vitro. In vivo, silencing of PARG significantly decreased tumor growth. PARGi synergized with DNA-damaging agents (i.e., oxaliplatin and 5-fluorouracil), but not with PARPi therapy. Mechanistically, combined PARGi and oxaliplatin treatment led to persistence of detrimental PARylation, increased expression of cleaved caspase-3, and increased γH2AX foci. In summary, these data validate PARG as a relevant target in PDAC and establish current therapies that synergize with PARGi. SIGNIFICANCE: PARG is a potential target in pancreatic cancer as a single-agent anticancer therapy or in combination with current standard of care. ©2019 American Association for Cancer Research.