title: Xrcc3 induces cisplatin resistance by stimulation of Rad51-related recombinational repair, S-phase checkpoint activation, and reduced apoptosis.
abstract: Eukaryotic cells respond to DNA damage by activation of DNA repair, cell cycle arrest, and apoptosis. Several reports suggest that such responses may be coordinated by communication between damage repair proteins and proteins signaling other cellular responses. The Rad51-guided homologous recombination repair system plays an important role in the recognition and repair of DNA interstrand crosslinks (ICLs), and cells deficient in this repair pathway become hypersensitive to ICL-inducing agents such as cisplatin and melphalan. We investigated the possible role of the Rad51-paralog protein Xrcc3 in drug resistance. Xrcc3 overexpression in MCF-7 cells resulted in 1) a 2- to 6-fold resistance to cisplatin/melphalan, 2) a 2-fold increase in drug-induced Rad51 foci, 3) an increased cisplatin-induced S-phase arrest, 4) decreased cisplatin-induced apoptosis, and 5) increased cisplatin-induced DNA synthesis arrest. Interestingly, Xrcc3 overexpression did not alter the doubling time or cell cycle progression in the absence of DNA damage. Furthermore, Xrcc3 overexpression is associated with increased Rad51C protein levels consistent with the known interaction of these two proteins. Our results demonstrate that Xrcc3 is an important factor in DNA cross-linking drug resistance in human tumor cells and suggest that the response of the homologous recombinational repair machinery and cell cycle checkpoints to DNA cross-linking agents is intertwined.
authors.affiliation: Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, 3755 Côte Ste. Catherine Road, Montreal, QC, Canada H3T 1E2.
authors.forename: Zhi-Yuan
authors.initials: ZY
authors.lastname: Xu
authors.forename: Martin
authors.initials: M
authors.lastname: Loignon
authors.forename: Fei-Yu
authors.initials: FY
authors.lastname: Han
authors.forename: Lawrence
authors.initials: L
authors.lastname: Panasci
authors.forename: Raquel
authors.initials: R
authors.lastname: Aloyz
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics; D045744:Cell Line, Tumor; D002470:Cell Survival; D002945:Cisplatin / Q000494:pharmacology*; D004260:DNA Repair / Q000502:physiology*; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D019008:Drug Resistance, Neoplasm; D005260:Female; D005434:Flow Cytometry; D016158:Genes, p53; D006801:Humans; D008558:Melphalan / Q000494:pharmacology; D051135:Rad51 Recombinase; D020239:Receptor Cross-Talk / Q000187:drug effects; D011994:Recombinant Proteins / Q000378:metabolism; D016196:S Phase / Q000502:physiology; D012854:Sister Chromatid Exchange
chemical_list: D017304:Annexin A5; D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; C110901:X-ray repair cross complementing protein 3; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D002945:Cisplatin; D008558:Melphalan