Werner Syndrome Helicase Has a Critical Role in DNA Damage Responses in the Absence of a Functional Fanconi Anemia Pathway

• Published in: Cancer research (Chicago, Ill.) Ill.), 2013-09, Vol.73 (17), p.5497-5507
• Main Authors: AGGARWAL, Monika, BANERJEE, Taraswi, SOMMERS, Joshua A, LANNASCOLI, Chiara, PICHIERRI, Pietro, SHOEMAKER, Robert H, BROSH, Robert M
• Format: Article
• Language: English
• Subjects: Alkylating Agents - pharmacology; Anemias. Hemoglobinopathies; Antineoplastic agents; Apoptosis - drug effects; Ataxia Telangiectasia Mutated Proteins - metabolism; Biological and medical sciences; Blotting, Western; Cell Proliferation - drug effects; Chromatin - genetics; Chromosomal Instability; Diseases of red blood cells; DNA Breaks, Double-Stranded - drug effects; DNA Repair - drug effects; DNA Replication - drug effects; DNA-Activated Protein Kinase - metabolism; Drug Synergism; Drug Therapy, Combination; Enzyme Inhibitors - pharmacology; Exodeoxyribonucleases - antagonists & inhibitors; Exodeoxyribonucleases - genetics; Exodeoxyribonucleases - metabolism; Fanconi Anemia - drug therapy; Fanconi Anemia - genetics; Fanconi Anemia - pathology; HCT116 Cells; HeLa Cells; Hematologic and hematopoietic diseases; Humans; Maleimides - pharmacology; Medical sciences; Mitomycin - pharmacology; Nuclear Proteins - metabolism; Pharmacology. Drug treatments; Rad51 Recombinase - metabolism; RecQ Helicases - antagonists & inhibitors; RecQ Helicases - genetics; RecQ Helicases - metabolism; RNA, Small Interfering - genetics; Tumors; Werner Syndrome Helicase
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.can-12-2975

Werner syndrome is genetically linked to mutations in WRN that encodes a DNA helicase-nuclease believed to operate at stalled replication forks. Using a newly identified small-molecule inhibitor of WRN helicase (NSC 617145), we investigated the role of WRN in the interstrand cross-link (ICL) response in cells derived from patients with Fanconi anemia, a hereditary disorder characterized by bone marrow failure and cancer. In FA-D2(-/-) cells, NSC 617145 acted synergistically with very low concentrations of mitomycin C to inhibit proliferation in a WRN-dependent manner and induce double-strand breaks (DSB) and chromosomal abnormalities. Under these conditions, ataxia-telangiectasia mutated activation and accumulation of DNA-dependent protein kinase, catalytic subunit pS2056 foci suggested an increased number of DSBs processed by nonhomologous end-joining (NHEJ). Rad51 foci were also elevated in FA-D2(-/-) cells exposed to NSC 617145 and mitomycin C, suggesting that WRN helicase inhibition interferes with later steps of homologous recombination at ICL-induced DSBs. Thus, when the Fanconi anemia pathway is defective, WRN helicase inhibition perturbs the normal ICL response, leading to NHEJ activation. Potential implication for treatment of Fanconi anemia-deficient tumors by their sensitization to DNA cross-linking agents is discussed.