Homologous recombination-deficient tumors are hyper-dependent on POLQ-mediated repair

Large-scale genomic studies have shown that half of epithelial ovarian cancers (EOCs) have alterations in genes regulating homologous recombination (HR) repair. Loss of HR accounts for the genomic instability of EOCs and for their cellular hyper-dependence on alternative poly-ADP ribose polymerase (PARP)-mediated DNA repair mechanisms. Previous studies have implicated the DNA polymerase θ (Polθ also known as POLQ, encoded by POLQ) in a pathway required for the repair of DNA double-strand breaks, referred to as the error-prone microhomology-mediated end-joining (MMEJ) pathway. Whether Polθ interacts with canonical DNA repair pathways to prevent genomic instability remains unknown. Here we report an inverse correlation between HR activity and Polθ expression in EOCs. Knockdown of Polθ in HR-proficient cells upregulates HR activity and RAD51 nucleofilament assembly, while knockdown of Polθ in HR-deficient EOCs enhances cell death. Consistent with these results, genetic inactivation of an HR gene (Fancd2) and Polq in mice results in embryonic lethality. Moreover, Polθ contains RAD51 binding motifs and it blocks RAD51-mediated recombination. Our results reveal a synthetic lethal relationship between the HR pathway and Polθ-mediated repair in EOCs, and identify Polθ as a novel druggable target for cancer therapy.

[1]  Elgene Lim,et al.  PARP1-driven poly-ADP-ribosylation regulates BRCA1 function in homologous recombination-mediated DNA repair. , 2014, Cancer discovery.

[2]  R. Wood,et al.  DNA polymerase θ (POLQ) can extend from mismatches and from bases opposite a (6-4) photoproduct , 2008 .

[3]  Monika Aggarwal,et al.  Inhibition of helicase activity by a small molecule impairs Werner syndrome helicase (WRN) function in the cellular response to DNA damage or replication stress , 2011, Proceedings of the National Academy of Sciences.

[4]  Anna Malkova,et al.  Srs2 and Sgs1–Top3 Suppress Crossovers during Double-Strand Break Repair in Yeast , 2003, Cell.

[5]  M. McVey,et al.  Synthesis-dependent microhomology-mediated end joining accounts for multiple types of repair junctions , 2010, Nucleic acids research.

[6]  P. Plevani,et al.  Caenorhabditis elegans POLQ-1 and HEL-308 function in two distinct DNA interstrand cross-link repair pathways. , 2008, DNA repair.

[7]  A. Shinohara,et al.  The controlling role of ATM in homologous recombinational repair of DNA damage , 2000, The EMBO journal.

[8]  Robert C. Bast,et al.  The biology of ovarian cancer: new opportunities for translation , 2009, Nature Reviews Cancer.

[9]  K. Hofmann,et al.  Inhibition of homologous recombination by the PCNA-interacting protein PARI. , 2012, Molecular cell.

[10]  Wouter Koole,et al.  A Polymerase Theta-dependent repair pathway suppresses extensive genomic instability at endogenous G4 DNA sites , 2014, Nature Communications.

[11]  Yu Zhang,et al.  An essential role for CtIP in chromosomal translocation formation through an alternative end-joining pathway , 2011, Nature Structural &Molecular Biology.

[12]  P. Plevani,et al.  Overlapping mechanisms promote postsynaptic RAD-51 filament disassembly during meiotic double-strand break repair. , 2010, Molecular cell.

[13]  Ana Pombo,et al.  Replicon Clusters Are Stable Units of Chromosome Structure: Evidence That Nuclear Organization Contributes to the Efficient Activation and Propagation of S Phase in Human Cells , 1998, The Journal of cell biology.

[14]  Jeremy M. Stark,et al.  Alternative-NHEJ Is a Mechanistically Distinct Pathway of Mammalian Chromosome Break Repair , 2008, PLoS genetics.

[15]  Steven J. M. Jones,et al.  Integrated genomic characterization of endometrial carcinoma , 2013, Nature.

[16]  A. D’Andrea,et al.  A DNA Repair Pathway–Focused Score for Prediction of Outcomes in Ovarian Cancer Treated With Platinum-Based Chemotherapy , 2012, Journal of the National Cancer Institute.

[17]  K. Hess,et al.  Association of BRCA1 and BRCA2 mutations with survival, chemotherapy sensitivity, and gene mutator phenotype in patients with ovarian cancer. , 2011, JAMA.

[18]  J. Soulier,et al.  Bone marrow failure in Fanconi anemia is triggered by an exacerbated p53/p21 DNA damage response that impairs hematopoietic stem and progenitor cells. , 2012, Cell stem cell.

[19]  M. McVey,et al.  Dual Roles for DNA Polymerase Theta in Alternative End-Joining Repair of Double-Strand Breaks in Drosophila , 2010, PLoS genetics.

[20]  M. McVey,et al.  MMEJ repair of double-strand breaks (director's cut): deleted sequences and alternative endings. , 2008, Trends in genetics : TIG.

[21]  Samuel H. Wilson,et al.  Vertebrate POLQ and POLbeta cooperate in base excision repair of oxidative DNA damage. , 2006, Molecular cell.

[22]  Zhao-Qi Wang,et al.  Human Fanconi anemia monoubiquitination pathway promotes homologous DNA repair. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[23]  Ralph R. Weichselbaum,et al.  DNA Repair Pathway Gene Expression Score Correlates with Repair Proficiency and Tumor Sensitivity to Chemotherapy , 2014, Science Translational Medicine.

[24]  Alan Ashworth,et al.  Targeting the DNA repair defect in BRCA mutant cells as a therapeutic strategy , 2005, Nature.

[25]  I. Bahar,et al.  High‐efficiency bypass of DNA damage by human DNA polymerase Q , 2004, The EMBO journal.

[26]  J. Kutok,et al.  Hematopoietic Stem Cell Defects in Mice with Deficiency of Fancd2 or Usp1 , 2010, Stem cells.

[27]  R. Wood,et al.  DNA polymerase POLQ and cellular defense against DNA damage. , 2013, DNA repair.

[28]  R. Wood,et al.  DNA polymerase theta (POLQ) can extend from mismatches and from bases opposite a (6-4) photoproduct. , 2008, DNA repair.

[29]  A. D’Andrea,et al.  DNA repair pathways in clinical practice: lessons from pediatric cancer susceptibility syndromes. , 2006, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[30]  Danny Kopec,et al.  Additional References , 2003 .

[31]  R. Fishel,et al.  The HsRAD51B-HsRAD51C stabilizes the HsRAD51 nucleoprotein filament. , 2013, DNA repair.

[32]  J. T. Kadonaga,et al.  HARP Is an ATP-Driven Annealing Helicase , 2008, Science.

[33]  David T. W. Jones,et al.  Signatures of mutational processes in human cancer , 2013, Nature.

[34]  A. Thompson,et al.  DNA polymerase θ up-regulation is associated with poor survival in breast cancer, perturbs DNA replication, and promotes genetic instability , 2010, Proceedings of the National Academy of Sciences.

[35]  Steven J. M. Jones,et al.  Comprehensive molecular portraits of human breast tumours , 2013 .

[36]  R. Wood,et al.  POLQ (Pol theta), a DNA polymerase and DNA-dependent ATPase in human cells. , 2003, Nucleic acids research.

[37]  J. Schimenti,et al.  The Mouse Genomic Instability Mutation chaos1 Is an Allele of Polq That Exhibits Genetic Interaction with Atm , 2004, Molecular and Cellular Biology.

[38]  R. Wood,et al.  POLQ (Pol θ), a DNA polymerase and DNA‐dependent ATPase in human cells , 2003 .

[39]  Stephen C. West,et al.  RTEL1 Maintains Genomic Stability by Suppressing Homologous Recombination , 2008, Cell.

[40]  Benjamin J. Raphael,et al.  Integrated Genomic Analyses of Ovarian Carcinoma , 2011, Nature.

[41]  Steven J. M. Jones,et al.  Comprehensive molecular portraits of human breast tumors , 2012, Nature.

[42]  Thomas Helleday,et al.  Specific killing of BRCA2-deficient tumours with inhibitors of poly(ADP-ribose) polymerase , 2005, Nature.

[43]  T. E. Wilson,et al.  Repair of double-strand breaks by end joining. , 2013, Cold Spring Harbor perspectives in biology.