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Homologous recombination mediates cellular resistance and fraction size sensitivity to radiation therapy
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
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2013 (English)In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 108, no 1, 155-161 p.Article in journal (Refereed) Published
Abstract [en]

Purpose: Cellular sensitivity to radiotherapy total dose and fraction size is strongly influenced by DNA double strand break (DSB) repair. Here, we investigate response to radiotherapy fraction size using CHO cell lines deficient in specific DNA repair pathways in response to radiation induced DNA double strand breaks (DSB). Experimental design: We irradiated CHO cell lines, AA8 (WT), irs1SF (XRCO-), V3-3 (DNA-PKcs-) and EM9 (XRCC1-) with 16 Gy in 1 Gy daily fractions over 3 weeks or 16 Gy in 4 Gy daily fractions over 4 days, and studied clonogenic survival, DNA DSB repair kinetics (RAD51 and 53BP1 foci staining) and cell cycle profiles (flow cytometry). Results: In response to fractionated radiotherapy, wild-type and DNA repair defective cells accumulated in late S/G2 phase. In cells proficient in homologous recombination (HR), accumulation in S/G2 resulted in reduced sensitivity to fraction size and increased cellular resistance (clonogenic survival). Sensitivity to fraction size was also lost in NHEJ-defective V3-3 cells, which likely rely on functional HR. By contrast, HR-defective irs1SF cells, with functional NHEJ, remained equally sensitive to fractionation throughout the 3-week treatment. Conclusions: The high fidelity of HR, which is independent of induced DNA damage level, is postulated to explain the low fractionation sensitivity and cellular resistance of cells in S/G2 phase. In conclusion, our results suggest that HR mediates resistance to fractionated radiotherapy, an observation that may help future efforts to improve radiotherapy outcome.

Place, publisher, year, edition, pages
2013. Vol. 108, no 1, 155-161 p.
Keyword [en]
Homologous recombination, Fractionated radiotherapy, Fraction size sensitivity, DNA double-strand break repair, Cell cycle
National Category
Radiology, Nuclear Medicine and Medical Imaging
URN: urn:nbn:se:su:diva-94866DOI: 10.1016/j.radonc.2013.05.012ISI: 000324155900025OAI: diva2:656617


Available from: 2013-10-16 Created: 2013-10-16 Last updated: 2013-10-16Bibliographically approved

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