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 (XRCC3-), 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.
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 (XRCC3-), 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.
Authors: Sophia B Chernikova; Rochelle B Nguyen; Jessica T Truong; Stephano S Mello; Jason H Stafford; Michael P Hay; Andrew Olson; David E Solow-Cordero; Douglas J Wood; Solomon Henry; Rie von Eyben; Lei Deng; Melanie Hayden Gephart; Asaithamby Aroumougame; Claudia Wiese; John C Game; Balázs Győrffy; J Martin Brown Journal: J Clin Invest Date: 2018-10-29 Impact factor: 14.808
Authors: Iris Eke; Dali Zong; Molykutty J Aryankalayil; Veit Sandfort; Michelle A Bylicky; Barbara H Rath; Edward E Graves; André Nussenzweig; C Norman Coleman Journal: Nucleic Acids Res Date: 2020-02-20 Impact factor: 16.971
Authors: Sushma Yadav; Claudia M Kowolik; Min Lin; Darren Zuro; Susanta K Hui; Arthur D Riggs; David A Horne Journal: Mol Carcinog Date: 2018-10-05 Impact factor: 4.784
Authors: Suzanne A Eccles; Eric O Aboagye; Simak Ali; Annie S Anderson; Jo Armes; Fedor Berditchevski; Jeremy P Blaydes; Keith Brennan; Nicola J Brown; Helen E Bryant; Nigel J Bundred; Joy M Burchell; Anna M Campbell; Jason S Carroll; Robert B Clarke; Charlotte E Coles; Gary J R Cook; Angela Cox; Nicola J Curtin; Lodewijk V Dekker; Isabel dos Santos Silva; Stephen W Duffy; Douglas F Easton; Diana M Eccles; Dylan R Edwards; Joanne Edwards; D Evans; Deborah F Fenlon; James M Flanagan; Claire Foster; William M Gallagher; Montserrat Garcia-Closas; Julia M W Gee; Andy J Gescher; Vicky Goh; Ashley M Groves; Amanda J Harvey; Michelle Harvie; Bryan T Hennessy; Stephen Hiscox; Ingunn Holen; Sacha J Howell; Anthony Howell; Gill Hubbard; Nick Hulbert-Williams; Myra S Hunter; Bharat Jasani; Louise J Jones; Timothy J Key; Cliona C Kirwan; Anthony Kong; Ian H Kunkler; Simon P Langdon; Martin O Leach; David J Mann; John F Marshall; Lesley Martin; Stewart G Martin; Jennifer E Macdougall; David W Miles; William R Miller; Joanna R Morris; Sue M Moss; Paul Mullan; Rachel Natrajan; James P B O'Connor; Rosemary O'Connor; Carlo Palmieri; Paul D P Pharoah; Emad A Rakha; Elizabeth Reed; Simon P Robinson; Erik Sahai; John M Saxton; Peter Schmid; Matthew J Smalley; Valerie Speirs; Robert Stein; John Stingl; Charles H Streuli; Andrew N J Tutt; Galina Velikova; Rosemary A Walker; Christine J Watson; Kaye J Williams; Leonie S Young; Alastair M Thompson Journal: Breast Cancer Res Date: 2013-10-01 Impact factor: 6.466