Comparison of apoptotic, necrotic and clonogenic cell death and inhibition of cell growth following camptothecin and X-radiation treatment in a human melanoma and a human fibroblast cell line

Purpose: We evaluated apoptotic. necrotic and clonogenic cell death and inhibition of cell growth in a human melanoma cell line (Sk-Mel-3) and a normal human fibroblast cell line (AG1522) following treatment with camptothecin (CPT) or with concurrent CPT and X-radiation. Materials and methods: Apoptotic and necrotic cell death was determined morphologically by dual-staining (propidium iodide, acridine orange). Inhibition of cell growth was determined from the number of cells remaining in the culture dish following treatment. Results: In Sk-Mel-3 cells: (a) after treatment with CPT alone, both apoptotic and necrotic cell death increased significantly (P < 0.05) relative to untreated controls; (b) after concurrent CPT and radiation treatment, however, only the increase in necrotic cell death was significant (P < 0.05) relative to cells receiving radiation alone; and (c) all assays of cellular effects/cytotoxicities were consistent in showing that CPT, given alone or with radiation, led to a substantial increase in cell kill. In contrast, in AG1522 cells: (a) there were no significant increases in apoptotic or necrotic cell death following either CPT alone or concurrent CPT and radiation; and (b) the clonogenic assay measured substantially higher cytotoxicities than the other assays. Conclusions: Necrotic cell death was more important than apoptotic cell death during concurrent CPT and radiation treatment in Sk-Mel-3 cells, but not in AG1522 cells.