title: Specific killing of DNA damage-response deficient cells with inhibitors of poly(ADP-ribose) glycohydrolase.
abstract: Poly(ADP-ribosylation) of proteins following DNA damage is well studied and the use of poly(ADP-ribose) polymerase (PARP) inhibitors as therapeutic agents is an exciting prospect for the treatment of many cancers. Poly(ADP-ribose) glycohydrolase (PARG) has endo- and exoglycosidase activities which can cleave glycosidic bonds, rapidly reversing the action of PARP enzymes. Like addition of poly(ADP-ribose) (PAR) by PARP, removal of PAR by PARG is also thought to be required for repair of DNA strand breaks and for continued replication at perturbed forks. Here we use siRNA to show a synthetic lethal relationship between PARG and BRCA1, BRCA2, PALB2, FAM175A (ABRAXAS) and BARD1. In addition, we demonstrate that MCF7 cells depleted of these proteins are sensitive to Gallotannin and a novel and specific PARG inhibitor PDD00017273. We confirm that PARG inhibition increases endogenous DNA damage, stalls replication forks and increases homologous recombination, and propose that it is the lack of homologous recombination (HR) proteins at PARG inhibitor-induced stalled replication forks that induces cell death. Interestingly not all genes that are synthetically lethal with PARP result in sensitivity to PARG inhibitors, suggesting that although there is overlap, the functions of PARP and PARG may not be completely identical. These data together add further evidence to the possibility that single treatment therapy with PARG inhibitors could be used for treatment of certain HR deficient tumours and provide insight into the relationship between PARP, PARG and the processes of DNA repair.
authors.affiliation: Academic Unit of Molecular Oncology, Sheffield Institute for Nucleic Acids (SInFoNiA), Department of Oncology and Metabolism, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX, United Kingdom.
authors.forename: Polly
authors.initials: P
authors.lastname: Gravells
authors.affiliation: Academic Unit of Molecular Oncology, Sheffield Institute for Nucleic Acids (SInFoNiA), Department of Oncology and Metabolism, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX, United Kingdom.
authors.forename: Emma
authors.initials: E
authors.lastname: Grant
authors.affiliation: Drug Discovery Unit, Cancer Research UK Manchester Institute, The University of Manchester, Wilmslow Road, Manchester, M20 4BX, United Kingdom.
authors.forename: Kate M
authors.initials: KM
authors.lastname: Smith
authors.affiliation: Drug Discovery Unit, Cancer Research UK Manchester Institute, The University of Manchester, Wilmslow Road, Manchester, M20 4BX, United Kingdom.
authors.forename: Dominic I
authors.initials: DI
authors.lastname: James
authors.affiliation: Academic Unit of Molecular Oncology, Sheffield Institute for Nucleic Acids (SInFoNiA), Department of Oncology and Metabolism, University of Sheffield, Beech Hill Road, Sheffield, S10 2RX, United Kingdom. Electronic address: h.bryant@sheffield.ac.uk.
authors.forename: Helen E
authors.initials: HE
authors.lastname: Bryant
mesh_terms: D019313:BRCA1 Protein / Q000378:metabolism; D024682:BRCA2 Protein / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication / Q000187:drug effects*; D000076164:Fanconi Anemia Complementation Group N Protein; D005260:Female; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D059765:Homologous Recombination; D006801:Humans; D047348:Hydrolyzable Tannins / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: C520310:ABRAXAS1 protein, human; D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D024682:BRCA2 Protein; C551750:BRCA2 protein, human; D002352:Carrier Proteins; D000076164:Fanconi Anemia Complementation Group N Protein; D047348:Hydrolyzable Tannins; D009687:Nuclear Proteins; C512790:PALB2 protein, human; D025521:Tumor Suppressor Proteins; D004247:DNA; C102449:BARD1 protein, human; D044767:Ubiquitin-Protein Ligases; D006026:Glycoside Hydrolases; C022407:poly ADP-ribose glycohydrolase
keywords: BARD1; BRCA1; Breast cancer; FAM175A (ABRAXAS); PALB2; PARG inhibition; Synthetic lethality