title: DNA damage response (DDR) pathway engagement in cisplatin radiosensitization of non-small cell lung cancer.
abstract: Non-small cell lung cancers (NSCLC) are commonly treated with a platinum-based chemotherapy such as cisplatin (CDDP) in combination with ionizing radiation (IR). Although clinical trials have demonstrated that the combination of CDDP and IR appear to be synergistic in terms of therapeutic efficacy, the mechanism of synergism remains largely uncharacterized. We investigated the role of the DNA damage response (DDR) in CDDP radiosensitization using two NSCLC cell lines. Using clonogenic survival assays, we determined that the cooperative cytotoxicity of CDDP and IR treatment is sequence dependent, requiring administration of CDDP prior to IR (CDDP-IR). We identified and interrogated the unique time and agent-dependent activation of the DDR in NSCLC cells treated with cisplatin-IR combination therapy. Compared to treatment with CDDP or IR alone, CDDP-IR combination treatment led to persistence of γH2Ax foci, a marker of DNA double-strand breaks (DSB), for up to 24h after treatment. Interestingly, pharmacologic inhibition of DDR sensor kinases revealed the persistence of γ-H2Ax foci in CDDP-IR treated cells is independent of kinase activation. Taken together, our data suggest that delayed repair of DSBs in NSCLC cells treated with CDDP-IR contributes to CDDP radiosensitization and that alterations of the DDR pathways by inhibition of specific DDR kinases can augment CDDP-IR cytotoxicity by a complementary mechanism.
authors.affiliation: Departments of Medicine, Indiana University School of Medicine, United States. Electronic address: crufatto@iu.edu.
authors.forename: Catherine R
authors.initials: CR
authors.lastname: Sears
authors.affiliation: School of Health and Rehabilitation Sciences, Indiana University-Purdue University, Indianapolis, Indiana, United States.
authors.forename: Sean A
authors.initials: SA
authors.lastname: Cooney
authors.affiliation: Radiation Oncology, Indiana University School of Medicine, United States.
authors.forename: Helen
authors.initials: H
authors.lastname: Chin-Sinex
authors.affiliation: Radiation Oncology, Indiana University School of Medicine, United States; Medical and Molecular Genetics, Indiana University School of Medicine, United States.
authors.forename: Marc S
authors.initials: MS
authors.lastname: Mendonca
authors.affiliation: Departments of Medicine, Indiana University School of Medicine, United States; Biochemistry and Molecular Biology, Indiana University School of Medicine, United States.
authors.forename: John J
authors.initials: JJ
authors.lastname: Turchi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D053903:DNA Breaks, Double-Stranded; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D059565:G2 Phase Cell Cycle Checkpoints; D006801:Humans; D011836:Radiation Tolerance / Q000187:drug effects* / Q000235:genetics; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D059767:Recombinational DNA Repair; D014965:X-Rays
chemical_list: D000970:Antineoplastic Agents; D011838:Radiation-Sensitizing Agents; D045643:DNA Repair Enzymes; D002945:Cisplatin
keywords: ATM; ATR; Cisplatin; Damage response; Lung cancer; Radiation