Multinucleated Giant Cancer Cells Produced in Response to Ionizing Radiation Retain Viability and Replicate Their Genome

Int J Mol Sci. 2017 Feb 8;18(2):360. doi: 10.3390/ijms18020360.


Loss of wild-type p53 function is widely accepted to be permissive for the development of multinucleated giant cells. However, whether therapy-induced multinucleation is associated with cancer cell death or survival remains controversial. Herein, we demonstrate that exposure of p53-deficient or p21WAF1 (p21)-deficient solid tumor-derived cell lines to ionizing radiation (between 2 and 8 Gy) results in the development of multinucleated giant cells that remain adherent to the culture dish for long times post-irradiation. Somewhat surprisingly, single-cell observations revealed that virtually all multinucleated giant cells that remain adherent for the duration of the experiments (up to three weeks post-irradiation) retain viability and metabolize 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT), and the majority (>60%) exhibit DNA synthesis. We further report that treatment of multinucleated giant cells with pharmacological activators of apoptosis (e.g., sodium salicylate) triggers their demise. Our observations reinforce the notion that radiation-induced multinucleation may reflect a survival mechanism for p53/p21-deficient cancer cells. With respect to evaluating radiosensitivity, our observations underscore the importance of single-cell experimental approaches (e.g., single-cell MTT) as the creation of viable multinucleated giant cells complicates the interpretation of the experimental data obtained by commonly-used multi-well plate colorimetric assays.

Keywords: 96-well plate XTT; colony forming ability; ionizing radiation; multinucleated giant cells; p21WAF1; p53; premature senescence; proliferation; single-cell MTT; viability.

MeSH terms

  • Cell Cycle Checkpoints / genetics
  • Cell Cycle Checkpoints / radiation effects
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Survival / genetics*
  • Cell Survival / radiation effects*
  • Cyclin-Dependent Kinase Inhibitor p21 / deficiency
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics
  • DNA Replication / radiation effects*
  • Gene Knockdown Techniques
  • Genome, Human / radiation effects*
  • Giant Cells / metabolism*
  • Giant Cells / radiation effects*
  • HCT116 Cells
  • Humans
  • Mutation
  • Radiation Tolerance / genetics
  • Radiation, Ionizing*
  • Tumor Stem Cell Assay
  • Tumor Suppressor Protein p53 / deficiency
  • Tumor Suppressor Protein p53 / genetics


  • Cyclin-Dependent Kinase Inhibitor p21
  • Tumor Suppressor Protein p53