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Sequential In vivo Imaging of Osteogenic Stem/Progenitor Cells During Fracture Repair
Published on: May 23, 2014
Intrinsic radiosensitivity and repair of sublethal radiation-induced damage in canine osteosarcoma cell lines
Courtney L Fitzpatrick1, James P Farese, Rowan J Milner
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA.
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 alpha/beta ratios (predictor of tissue sensitivity to radiation therapy) for the cell lines were low (mean ratio, 3.47). The split-dose experiments revealed a 2.8- to 3.9-fold increase in cell survival when the radiation doses were applied at an interval of 24 hours, compared with cell survival after radiation doses were applied consecutively (0-hour interval).
Conclusions And Clinical Relevance:
Results indicated that these canine osteosarcoma cell lines are fairly radioresistant; alpha/beta ratios were similar to those of nonneoplastic, late-responding tissues. Future clinical investigations should involve increasing the fraction size in a manner that maximizes tumor killing without adverse effects on the nonneoplastic surrounding tissues.
Insights
Canine osteosarcoma cell lines show significant radioresistance and capacity for sublethal damage repair (SLDR), similar to normal tissues. Further research should explore optimized radiation fraction sizes for improved tumor treatment.
Area of Science:
- Veterinary Oncology
- Radiation Oncology
- Cell Biology
Background:
- Canine osteosarcoma is a common bone cancer in dogs.
- Understanding tumor cell radiosensitivity is crucial for effective radiation therapy.
- Sublethal damage repair (SLDR) influences treatment outcomes.
Purpose of the Study:
- To determine the radiosensitivity of four canine osteosarcoma cell lines.
- To assess the capacity for sublethal damage repair (SLDR) in these cell lines.
- To inform potential clinical radiation strategies for canine osteosarcoma.
Main Methods:
- Four canine osteosarcoma cell lines (HMPOS, POS, COS 31, D17) were used.
- Clonogenic assays evaluated intrinsic radiosensitivity and SLDR.
- Dose-response curves were generated using a linear quadratic model.
- Split-dose experiments assessed SLDR at varying time intervals.
Main Results:
- No significant differences in mean surviving fractions among the four cell lines.
- High mean surviving fraction at 2 Gy (0.62) and low alpha/beta ratios (mean 3.47) indicated radioresistance.
- A 2.8- to 3.9-fold increase in cell survival was observed with a 24-hour interval between radiation doses, demonstrating significant SLDR.
Conclusions:
- Canine osteosarcoma cell lines exhibit considerable radioresistance, comparable to late-responding normal tissues.
- Low alpha/beta ratios suggest potential for normal tissue complications with conventional fractionation.
- Clinical strategies may benefit from larger fraction sizes to enhance tumor cell kill while minimizing normal tissue damage.
