Abstract
Canine cancer cell lines have progressively been developed, but are still underused resources for radiation biology research. Measurement of the cellular intrinsic radiosensitivity is important because understanding the difference may provide a framework for further elucidating profiles for prediction of radiation therapy response. Our studies have focused on characterizing diverse canine cancer cell lines in vitro and understanding parameters that might contribute to intrinsic radiosensitivity. First, intrinsic radiosensitivity of 27 canine cancer cell lines derived from ten tumor types was determined using a clonogenic assay. The 27 cell lines had varying radiosensitivities regardless tumor type (survival fraction at 2 Gy, SF2 = 0.19–0.93). In order to understand parameters that might contribute to intrinsic radiosensitivity, we evaluated the relationships of cellular radiosensitivity with basic cellular characteristics of the cell lines. There was no significant correlation of SF2 with S-phase fraction, doubling time, chromosome number, ploidy, or number of metacentric chromosomes, while there was a statistically significant correlation between SF2 and plating efficiency. Next, we selected the five most radiosensitive cell lines as the radiosensitive group and the five most radioresistant cell lines as the radioresistant group. Then, we evaluated known parameters for cell killing by ionizing radiation, including radiation-induced DNA double strand break (DSB) repair and apoptosis, in the radiosensitive group as compared to the radioresistant group. High levels of residual γ-H2AX foci at the sites of DSBs were present in the four out of the five radiosensitive canine cancer cell lines. Our studies suggested that substantial differences in intrinsic radiosensitivity exist in canine cancer cell lines, and radiation-induced DSB repair was related to radiosensitivity, which is consistent with previous human studies. These data may assist further investigations focusing on the detection of DSB for predicting individual response to radiation therapy for dogs, regardless of tumor type.
Highlights
Cancer is a major cause of death in dogs as well as in humans
We examined the intrinsic radiosensitivity of 27 canine cancer cell lines derived from ten tumor types
For example, had a smaller number of chromosome per cell with 64.4, but the ploidy pattern was between diploidy and triploidy
Summary
Cancer is a major cause of death in dogs as well as in humans. Canine cancer models have emerged as valuable resources in the study of human cancer [2]. Numerous well characterized human cancer cell lines are available for cancer research. Cancer cell lines have been widely used as in vitro experimental model systems and have proved to be useful for exploring the underlying biology of cancer [3]. Canine cancer cell lines have progressively been developed and utilized, but are not as fully characterized as human cell lines. Investigation of the cellular biology through characterizations of canine cancer cell lines may provide additional information about cancer biology, some specific to dogs, and some potentially supplementing those reported for human cancer
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