title: Use of the γ-H2AX assay to investigate DNA repair dynamics following multiple radiation exposures.
abstract: Radiation therapy is one of the most common and effective strategies used to treat cancer. The irradiation is usually performed with a fractionated scheme, where the dose required to kill tumour cells is given in several sessions, spaced by specific time intervals, to allow healthy tissue recovery. In this work, we examined the DNA repair dynamics of cells exposed to radiation delivered in fractions, by assessing the response of histone-2AX (H2AX) phosphorylation (γ-H2AX), a marker of DNA double strand breaks. γ-H2AX foci induction and disappearance were monitored following split dose irradiation experiments in which time interval between exposure and dose were varied. Experimental data have been coupled to an analytical theoretical model, in order to quantify key parameters involved in the foci induction process. Induction of γ-H2AX foci was found to be affected by the initial radiation exposure with a smaller number of foci induced by subsequent exposures. This was compared to chromatin relaxation and cell survival. The time needed for full recovery of γ-H2AX foci induction was quantified (12 hours) and the 1:1 relationship between radiation induced DNA double strand breaks and foci numbers was critically assessed in the multiple irradiation scenarios.
authors: Dipartimento di Fisica, Università degli studi di Pavia, Pavia, Italy ; Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia, Italy.
authors: Luca G
authors: LG
authors: Mariotti
authors: Giacomo
authors: G
authors: Pirovano
authors: Kienan I
authors: KI
authors: Savage
authors: Mihaela
authors: M
authors: Ghita
authors: Andrea
authors: A
authors: Ottolenghi
authors: Kevin M
authors: KM
authors: Prise
authors: Giuseppe
authors: G
authors: Schettino
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D002843:Chromatin / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects; D006657:Histones / Q000378:metabolism*; D006801:Humans; D010766:Phosphorylation; D011829:Radiation Dosage; D011878:Radiotherapy / Q000009:adverse effects; D014965:X-Rays / Q000009:adverse effects*
chemical_list: D002843:Chromatin; C468783:H2AX protein, human; D006657:Histones