title: Inhibition of homologous recombination by hyperthermia shunts early double strand break repair to non-homologous end-joining.
abstract: In S and G2 phase mammalian cells DNA double strand breaks (DSBs) can potentially be repaired by homologous recombination (HR) or non-homologous end-joining (NHEJ). Results of several studies suggest that these two mechanistically distinct repair pathways can compete for DNA ends. Because HR and NHEJ differ with respect to error susceptibility, generation of chromosome rearrangements, which are potentially carcinogenic products of DSB repair, may depend on the pathway choice. To investigate this hypothesis, the influence of HR and NHEJ inhibition on the frequencies of chromosome aberrations in G2 phase cells was investigated. SW-1573 and RKO cells were treated with mild (41 °C) hyperthermia in order to disable HR and/or NU7441/cisplatin to inactivate NHEJ and frequencies of chromosomal fragments (resulting from unrepaired DSBs) and translocations (products of erroneous DSB rejoining) were studied using premature chromosome condensation (PCC) combined with fluorescence in situ hybridization (FISH). It is shown here that temporary inhibition of HR by hyperthermia results in increased frequency of ionizing-radiation (IR)-induced chromosomal translocations and that this effect is abrogated by NU7441- or cisplatin-mediated inhibition of NHEJ. The results suggest that in the absence of HR, DSB repair is shifted to the error-prone NHEJ pathway resulting in increased frequencies of chromosomal rearrangements. These results might be of consequence for clinical cancer treatment approaches that aim at inhibition of one or more DSB repair pathways.
authors.affiliation: Laboratory for Experimental Oncology and Radiobiology (LEXOR), Center for Experimental Molecular Medicine, Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands.
authors.forename: Judith W J
authors.initials: JW
authors.lastname: Bergs
authors.forename: Przemek M
authors.initials: PM
authors.lastname: Krawczyk
authors.forename: Tijana
authors.initials: T
authors.lastname: Borovski
authors.forename: Rosemarie
authors.initials: R
authors.lastname: ten Cate
authors.forename: Hans M
authors.initials: HM
authors.lastname: Rodermond
authors.forename: Jan
authors.initials: J
authors.lastname: Stap
authors.forename: Jan Paul
authors.initials: JP
authors.lastname: Medema
authors.forename: Jaap
authors.initials: J
authors.lastname: Haveman
authors.forename: Jeroen
authors.initials: J
authors.lastname: Essers
authors.forename: Chris
authors.initials: C
authors.lastname: van Bree
authors.forename: Lukas J A
authors.initials: LJ
authors.lastname: Stalpers
authors.forename: Roland
authors.initials: R
authors.lastname: Kanaar
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Aten
authors.forename: Nicolaas A P
authors.initials: NA
authors.lastname: Franken
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002867:Chromones; D002945:Cisplatin / Q000633:toxicity; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D016195:G2 Phase; D005720:Gamma Rays; D059765:Homologous Recombination; D006358:Hot Temperature; D006801:Humans; D051379:Mice; D009025:Morpholines; D011836:Radiation Tolerance; D059767:Recombinational DNA Repair; D014178:Translocation, Genetic / Q000187:drug effects / Q000528:radiation effects
chemical_list: C499693:8-dibenzothiophen-4-yl-2-morpholin-4-yl-chromen-4-one; D002867:Chromones; D009025:Morpholines; D002945:Cisplatin