title: Multinucleated Giant Cancer Cells Produced in Response to Ionizing Radiation Retain Viability and Replicate Their Genome.
abstract: 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.
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada. razmik.mirzayans@ahs.ca.
authors.forename: Razmik
authors.initials: R
authors.lastname: Mirzayans
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada. bonnie.andrais@ahs.ca.
authors.forename: Bonnie
authors.initials: B
authors.lastname: Andrais
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada. april.scott@ahs.ca.
authors.forename: April
authors.initials: A
authors.lastname: Scott
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada. ywwang@ualberta.ca.
authors.forename: Ying W
authors.initials: YW
authors.lastname: Wang
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada. pkumar@ualberta.ca.
authors.forename: Piyush
authors.initials: P
authors.lastname: Kumar
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada. david.murray5@ahs.ca.
authors.forename: David
authors.initials: D
authors.lastname: Murray
mesh_terms: D059447:Cell Cycle Checkpoints / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival / Q000235:genetics* / Q000528:radiation effects*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000172:deficiency / Q000235:genetics; D004261:DNA Replication / Q000528:radiation effects*; D055785:Gene Knockdown Techniques; D015894:Genome, Human / Q000528:radiation effects*; D015726:Giant Cells / Q000378:metabolism* / Q000528:radiation effects*; D045325:HCT116 Cells; D006801:Humans; D009154:Mutation; D011836:Radiation Tolerance / Q000235:genetics; D011839:Radiation, Ionizing; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53
keywords: 96-well plate XTT; colony forming ability; ionizing radiation; multinucleated giant cells; p21WAF1; p53; premature senescence; proliferation; single-cell MTT; viability