title: Decay of γ-H2AX foci correlates with potentially lethal damage repair and P53 status in human colorectal carcinoma cells.
abstract: The influence of p53 status on potentially lethal damage repair (PLDR) and DNA double-strand break (DSB) repair was studied in two isogenic human colorectal carcinoma cell lines: RKO (p53 wild-type) and RC10.1 (p53 null). They were treated with different doses of ionizing radiation, and survival and the induction of DNA-DSB were studied. PLDR was determined by using clonogenic assays and then comparing the survival of cells plated immediately with the survival of cells plated 24 h after irradiation. Doses varied from 0 to 8 Gy. Survival curves were analyzed using the linear-quadratic formula: S(D)/S(0) = exp-(αD+βD(2)). The γ-H2AX foci assay was used to study DNA DSB kinetics. Cells were irradiated with single doses of 0, 0.5, 1 and 2 Gy. Foci levels were studied in non-irradiated control cells and 30 min and 24 h after irradiation. Irradiation was performed with gamma rays from a (137)Cs source, with a dose rate of 0.5 Gy/min. The RKO cells show higher survival rates after delayed plating than after immediate plating, while no such difference was found for the RC10.1 cells. Functional p53 seems to be a relevant characteristic regarding PLDR for cell survival. Decay of γ-H2AX foci after exposure to ionizing radiation is associated with DSB repair. More residual foci are observed in RC10.1 than in RKO, indicating that decay of γ-H2AX foci correlates with p53 functionality and PLDR in RKO cells.
authors.affiliation: Laboratory for Experimental Oncology and Radiobiology (LEXOR), Center for Experimental Molecular Medicine, Department of Radiation Oncology, University of Amsterdam, P.O. Box 22700, 1100 DE, Amsterdam, The Netherlands.
authors.forename: Bregje
authors.initials: B
authors.lastname: Van Oorschot
authors.forename: Arlene L
authors.initials: AL
authors.lastname: Oei
authors.forename: Anna C
authors.initials: AC
authors.lastname: Nuijens
authors.forename: Hans
authors.initials: H
authors.lastname: Rodermond
authors.forename: Ron
authors.initials: R
authors.lastname: Hoeben
authors.forename: Jan
authors.initials: J
authors.lastname: Stap
authors.forename: Lukas J
authors.initials: LJ
authors.lastname: Stalpers
authors.forename: Nicolaas A P
authors.initials: NA
authors.lastname: Franken
mesh_terms: D002470:Cell Survival / Q000235:genetics* / Q000528:radiation effects; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair / Q000235:genetics / Q000528:radiation effects; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D011839:Radiation, Ionizing; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: C468783:H2AX protein, human; D006657:Histones; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53