Carbon ions-induced apoptosis in hematopoietic tumor cell lines

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.

RDM4 (murine T lymphoma), MOLT-4, TK6 and WTK1 (human lymphoblastoid) cells were irradiated with 12C or 13C. Apoptosis was assessed by flow cytometry. Cell growth and activities of caspases were determined during the same periods.

The ability of carbon ions to induce apoptosis markedly varied according to the cell line. MOLT-4 and TK6 cells underwent apoptosis at 1 Gy within 12 hours post-irradiation, whereas RDM4 and WTK1 showed little apoptosis under the same conditions.

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.