Carbon ions-induced apoptosis in hematopoietic tumor cell lines

Background: The purpose of this study was to assess apoptosis in hematopoietic tumor cells irradiated with carbon ions, in order to define its contribution to the cytotoxicity of these high-LET radiations. Materials and Methods: RDM4 (murine T lymphoma), MOLT-4, TK6 and WTK1 (human lymphoblastoid) cells were irradiated with C-12 or C-13. Apoptosis was assessed by flow cytometry. Cell growth and activities of caspases were determined during the same periods. Results: The ability of carbon ions to induce apoptosis markedly varied according to the cell line. MOLT-4 and TK6 cells underwent apoptosis at I Gy within 12 hours post-irradiation, whereas RDM4 and WTK1 showed little apoptosis under the same conditions. Conclusion: These results indicate that apoptosis contributes to the overall cytotoxicity of carbon ions towards hematopoietic tumor cells although other death mechanisms must also account for this cytotoxicity