In Vitro Characterization of Docetaxel as a Radiosensitizer in Canine and Feline Cancer Cell Lines

An in vitro study was conducted to investigate docetaxel as a radiation sensitizer in four canine (mammary carcinoma— CMT12 and CMT25, osteosarcoma—OS2.4, and transitional cell carcinoma—PTCC), and one feline cancer cell line (oral squamous cell carcinoma—SCCF1) to provide a basis for combination therapy in clinical patients. Cells were exposed to docetaxel followed by a single dose of radiation. The percent surviving fraction was determined by MTT assay. The combination index (CI) method determined synergistic cytotoxicity for the CMT12, CMT25 and OS2.4 cell lines with median CI values of 0.35, 0.47, 0.63 respectively. The SCCF1 cell line had moderate synergistic cytotoxicity with a median CI of 0.76, while the PTCC cell line resulted in antagonistic cytoxicity with a median CI of 2.75. The results indicated that docetaxel was a radiation sensitizer in 4 out of the 5 cancer cell lines tested.