title: A synthetic lethal screen identifies ATR-inhibition as a novel therapeutic approach for POLD1-deficient cancers.
abstract: The phosphoinositide 3-kinase-related kinase ATR represents a central checkpoint regulator and mediator of DNA-repair. Its inhibition selectively eliminates certain subsets of cancer cells in various tumor types, but the underlying genetic determinants remain enigmatic. Here, we applied a synthetic lethal screen directed against 288 DNA-repair genes using the well-defined ATR knock-in model of DLD1 colorectal cancer cells to identify potential DNA-repair defects mediating these effects. We identified a set of DNA-repair proteins, whose knockdown selectively killed ATR-deficient cancer cells. From this set, we further investigated the profound synthetic lethal interaction between ATR and POLD1. ATR-dependent POLD1 knockdown-induced cell killing was reproducible pharmacologically in POLD1-depleted DLD1 cells and a panel of other colorectal cancer cell lines by using chemical inhibitors of ATR or its major effector kinase CHK1. Mechanistically, POLD1 depletion in ATR-deficient cells caused caspase-dependent apoptosis without preceding cell cycle arrest and increased DNA-damage along with impaired DNA-repair. Our data could have clinical implications regarding tumor genotype-based cancer therapy, as inactivating POLD1 mutations have recently been identified in small subsets of colorectal and endometrial cancers. POLD1 deficiency might thus represent a predictive marker for treatment response towards ATR- or CHK1-inhibitors that are currently tested in clinical trials.
authors.affiliation: Department of Medicine II, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Hocke
authors.affiliation: Department of Medicine II, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Yang
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Gastroenterology, Endocrinology and Metabolism, University Hospital of Marburg, Philipps-University of Marburg, 35043 Marburg, Germany.
authors.forename: Albert
authors.initials: A
authors.lastname: Job
authors.affiliation: Department of Radiotherapy and Radiation Oncology, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Orth
authors.affiliation: Department of Medicine II, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ziesch
authors.affiliation: Department of Radiotherapy and Radiation Oncology, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Lauber
authors.affiliation: Department of Medicine II, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Enrico N
authors.initials: EN
authors.lastname: De Toni
authors.affiliation: Department of Gastroenterology, Endocrinology and Metabolism, University Hospital of Marburg, Philipps-University of Marburg, 35043 Marburg, Germany.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Gress
authors.affiliation: Department of Medicine II, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Herbst
authors.affiliation: Department of Medicine II, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Göke
authors.affiliation: Department of Medicine II, Ludwig-Maximilians-University of Munich, 81377 Munich, Germany.|Department of Gastroenterology, Endocrinology and Metabolism, University Hospital of Marburg, Philipps-University of Marburg, 35043 Marburg, Germany.
authors.forename: Eike
authors.initials: E
authors.lastname: Gallmeier
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology*; D004249:DNA Damage / Q000187:drug effects; D004258:DNA Polymerase III / Q000172:deficiency* / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects; D045643:DNA Repair Enzymes / Q000037:antagonists & inhibitors* / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005470:Fluorometry; D057166:High-Throughput Screening Assays; D006657:Histones / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000235:genetics; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D004791:Enzyme Inhibitors; C468783:H2AX protein, human; D006657:Histones; D034741:RNA, Small Interfering; D011494:Protein Kinases; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C434055:POLD1 protein, human; D004258:DNA Polymerase III; D045643:DNA Repair Enzymes
keywords: ATR; DNA repair; POLD1; synthetic lethality; targeted therapy