Etoposide enhances the lethal effect of radiation on breast cancer cells with less damage to mammary gland cells

Purpose: In the present study, the cytotoxic effects of anticancer drug treatment plus radiation on breast cancer and normal mammary gland cells were investigated in vitro. Methods: Breast cancer and adjacent mammary gland tissue was obtained from surgically resected specimens from 13 premenopausal female patients, and was cultured. Cultured cells were treated with radiation and etoposide, and sensitivities were evaluated using an MTT assay. Results, In breast cancer cells, radiation alone had a cytotoxic effect. When etoposide was added, synergistic effects were achieved which were independent of the radiation dose. The cytotoxicity of etoposide against normal gland cells, however, was much the same as that against cancer cells, and no synergistic effects were observed in normal cells even when radiation was added. Conclusions: Radiation combined with etoposide showed lethal effects against breast cancer cells with less damage to normal mammary gland cells.