Experimental investigation of the cytotoxicity of medium-borne signals in human prostate cancer cell line

INTRODUCTION: Evidence exists that exposure of non-irradiated cells to Irradiated Cell Conditioned Medium (ICCM) can cause effects similar to those resulting from direct radiation damage. This study attempts to validate the stochastic model, relating absorbed dose to the emission and processing of cell death signals by non-irradiated cells, in vitro in PC3 human prostate cancer cell line. METHODS: The recipient cell survival was measured after exposure of cells to ICMM derived from donor cells: a) exposed to radiation doses from 2 Gy to 8 Gy and b) of concentrations varying from 2 × 10(2) to 6 × 10(6) irradiated with 2 Gy. RESULTS: Exposure to ICCM, irradiated with doses between 2-8 Gy, resulted in a significant (p < 0.001) decrease in clonogenic survival of non-irradiated recipient cells compared to the control group. However, dose dependency above 2 Gy was not observed, indicating that any dose threshold was below 2 Gy. A significant (p < 0.001) decrease in survival was found in recipient cells exposed to the ICCM, derived from different concentrations of donor cells exposed to 2 Gy, compared to the control group. The recipient cell survival following exposure to ICCM derived from 2 × 10(2) cells was significantly higher (p < 0.5) compared to the rest of donor cell concentrations, indicating that the toxicity of ICCM depends on the cellular concentration of donor cells. Non-linear regression data fitting provided reasonable agreement with the microdosimetric model for the induction of cell killing through medium-borne signals. CONCLUSION: For the given cell line and given experimental conditions, significant decreases in cell survival were observed in non-irradiated cells exposed to ICCM derived from donor cells of various concentrations and irradiated with different doses.