Pilocarpine, a salivary gland radioprotectant, does not inhibit cytotoxic effect of γ-radiation on squamous cell carcinoma in vitro

Purpose: Pilocarpine, a salivary stimulant, has been shown to protect salivary glands from γ-radiation-induced damage during the radiotherapy of head and neck tumors. This study was performed to determine whether pilocarpine affects the survival of squamous carcinoma cells, line SCC-25, following γ-radiation treatment. Methods and Materials: The survival of squamous carcinoma tumor cells, line SCC-25, following the exposure of cells to pilocarpine at concentration of 0-100 ng/ml given for 0-1 h prior to radiation at dose of 0-20 Gy was determined by an in vitro colony-formation assay. Results: The survival fractions of SCC-25 cells were identical for the control and pilocarpine-treated samples at all tested conditions. Calculated Do and Dq values did not depend on the presence of pilocarpine and were not affected by the time of incubation prior to irradiation. Conclusion: Pilocarpine, at clinically relevant concentrations, given to the SCC-25 cells 1 h prior to or at the time of irradiation did not affect survival of SCC-25 cells in vitro. Pilocarpine does not sensitize or protect these tumor cells from the effects of γ-radiation, suggesting that this agent should not compromise the tumoricidal effects of radiotherapy