title: Ovarian Cancers Harbor Defects in Nonhomologous End Joining Resulting in Resistance to Rucaparib.
abstract: Purpose:DNA damage defects are common in ovarian cancer and can be used to stratify treatment. Although most work has focused on homologous recombination (HR), DNA double-strand breaks are repaired primarily by nonhomologous end joining (NHEJ). Defects in NHEJ have been shown to contribute to genomic instability and have been associated with the development of chemoresistance.Experimental Design:NHEJ was assessed in a panel of ovarian cancer cell lines and 47 primary ascetic-derived ovarian cancer cultures, by measuring the ability of cell extracts to end-join linearized plasmid monomers into multimers. mRNA and protein expression of components of NHEJ was determined using RT-qPCR and Western blotting. Cytotoxicities of cisplatin and the PARP inhibitor rucaparib were assessed using sulforhodamine B (SRB) assays. HR function was assessed using γH2AX/RAD51 foci assay.Results:NHEJ was defective (D) in four of six cell lines and 20 of 47 primary cultures. NHEJ function was independent of HR competence (C). NHEJD cultures were resistant to rucaparib (P= 0.0022). When HR and NHEJ functions were taken into account, only NHEJC/HRD cultures were sensitive to rucaparib (compared with NHEJC/HRCP= 0.034, NHEJD/HRCP= 0.0002, and NHEJD/HRDP= 0.0045). The DNA-PK inhibitor, NU7441, induced resistance to rucaparib (P= 0.014) and HR function recovery in a BRCA1-defective cell line.Conclusions:This study has shown that NHEJ is defective in 40% of ovarian cancers, which is independent of HR function and associated with resistance to PARP inhibitors inex vivoprimary cultures.Clin Cancer Res; 23(8); 2050-60. ©2016 AACR.
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.
authors.forename: Aiste
authors.initials: A
authors.lastname: McCormick
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Donoghue
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.
authors.forename: Michelle
authors.initials: M
authors.lastname: Dixon
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: O'Sullivan
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.|Northern Gynaecological Oncology Centre, Queen Elizabeth Hospital, Gateshead, United Kingdom.
authors.forename: Rachel L
authors.initials: RL
authors.lastname: O'Donnell
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.
authors.forename: James
authors.initials: J
authors.lastname: Murray
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom.|Northern Gynaecological Oncology Centre, Queen Elizabeth Hospital, Gateshead, United Kingdom.
authors.forename: Angelika
authors.initials: A
authors.lastname: Kaufmann
authors.affiliation: Northern Institute for Cancer Research, Newcastle University, Framlington Place, Newcastle upon Tyne, United Kingdom. richard.edmondson@manchester.ac.uk n.j.curtin@ncl.ac.uk.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Curtin
authors.affiliation: Faculty Institute for Cancer Studies, University of Manchester, St Mary's Hospital, Oxford Road, Manchester, United Kingdom. richard.edmondson@manchester.ac.uk n.j.curtin@ncl.ac.uk.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Edmondson
mesh_terms: D000970:Antineoplastic Agents; D015153:Blotting, Western; D045744:Cell Line, Tumor; D059766:DNA End-Joining Repair / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007211:Indoles; D010051:Ovarian Neoplasms / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000970:Antineoplastic Agents; D007211:Indoles; C531549:rucaparib