Open Access

Decay of γ-H2AX foci correlates with potentially lethal damage repair and P53 status in human colorectal carcinoma cells

  • Bregje Van Oorschot1,
  • Arlene L. Oei1,
  • Anna C. Nuijens1,
  • Hans Rodermond1,
  • Ron Hoeben2,
  • Jan Stap2,
  • Lukas J. Stalpers1 and
  • Nicolaas A. P. Franken1Email author
Cellular & Molecular Biology LettersAn International Journal201319:113

Received: 9 July 2013

Accepted: 18 December 2013

Published: 23 December 2013


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+βD2). 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 137Cs 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.

Key words

p53 Radiation sensitivity Potentially lethal damage repair (PLDR) Linear-quadratic model Clonogenic assay Colon cancer cells RKO cells, RC10.1 cells γ-H2AX foci Flow cytometry