Intrinsic radiosensitivity and repair of sublethal radiation-induced damage in canine osteosarcoma cell lines

Objective—To characterize the radiosensitivity and capacity for sublethal damage repair (SLDR) of radiation-induced injury in 4 canine osteosarcoma cell lines. Sample Population—4 canine osteosarcoma cell lines (HMPOS, POS, COS 31, and D17). Procedures—A clonogenic colony-forming assay was used to evaluate the cell lines' intrinsic radiosensitivities and SLDR capacities. Dose-response curves for the cell lines were generated by fitting the surviving fractions after radiation doses of 0 (control cells), 1, 2, 3, 6, and 9 Gy to a linear quadratic model. To evaluate SLDR, cell lines were exposed to 2 doses of 3 Gy (split-dose experiments) at an interval of 0 (single 6-Gy dose), 2, 4, 6, or 24 hours, after which the surviving fractions were assessed. Results—Mean surviving fraction did not differ significantly among the 4 cell lines at the radiation doses tested. Mean surviving fraction at 2 Gy was high (0.62), and the α/β ratios (predictor of tissue sensitivity to radiation therapy) for the cell lines were l...