title: Hyperthermia activates a subset of ataxia-telangiectasia mutated effectors independent of DNA strand breaks and heat shock protein 70 status.
abstract: All cells have intricately coupled sensing and signaling mechanisms that regulate the cellular outcome following exposure to genotoxic agents such as ionizing radiation (IR). In the IR-induced signaling pathway, specific protein events, such as ataxia-telangiectasia mutated protein (ATM) activation and histone H2AX phosphorylation (gamma-H2AX), are mechanistically well characterized. How these mechanisms can be altered, especially by clinically relevant agents, is not clear. Here we show that hyperthermia, an effective radiosensitizer, can induce several steps associated with IR signaling in cells. Hyperthermia induces gamma-H2AX foci formation similar to foci formed in response to IR exposure, and heat-induced gamma-H2AX foci formation is dependent on ATM but independent of heat shock protein 70 expression. Hyperthermia also enhanced ATM kinase activity and increased cellular ATM autophosphorylation. The hyperthermia-induced increase in ATM phosphorylation was independent of Mre11 function. Similar to IR, hyperthermia also induced MDC1 foci formation; however, it did not induce all of the characteristic signals associated with irradiation because formation of 53BP1 and SMC1 foci was not observed in heated cells but occurred in irradiated cells. Additionally, induction of chromosomal DNA strand breaks was observed in IR-exposed but not in heated cells. These results indicate that hyperthermia activates signaling pathways that overlap with those activated by IR-induced DNA damage. Moreover, prior activation of ATM or other components of the IR-induced signaling pathway by heat may interfere with the normal IR-induced signaling required for chromosomal DNA double-strand break repair, thus resulting in increased cellular radiosensitivity.
authors.affiliation: Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri, USA.
authors.forename: Clayton R
authors.initials: CR
authors.lastname: Hunt
authors.forename: Raj K
authors.initials: RK
authors.lastname: Pandita
authors.forename: Andrei
authors.initials: A
authors.lastname: Laszlo
authors.forename: Ryuji
authors.initials: R
authors.lastname: Higashikubo
authors.forename: Manjula
authors.initials: M
authors.lastname: Agarwal
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Kitamura
authors.forename: Arun
authors.initials: A
authors.lastname: Gupta
authors.forename: Nicole
authors.initials: N
authors.lastname: Rief
authors.forename: Nobuo
authors.initials: N
authors.lastname: Horikoshi
authors.forename: Rajeskaran
authors.initials: R
authors.lastname: Baskaran
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Lee
authors.forename: Markus
authors.initials: M
authors.lastname: Löbrich
authors.forename: Tanya T
authors.initials: TT
authors.lastname: Paull
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Roti Roti
authors.forename: Tej K
authors.initials: TK
authors.lastname: Pandita
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D002460:Cell Line; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000378:metabolism / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000378:metabolism*; D018869:Heat-Shock Response / Q000235:genetics; D006657:Histones / Q000096:biosynthesis; D006801:Humans; D006979:Hyperthermia, Induced; D051379:Mice; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000378:metabolism*; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D018840:HSP70 Heat-Shock Proteins; D006657:Histones; D025521:Tumor Suppressor Proteins; C475961:gamma-H2AX protein, mouse; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases