Apoptosis of HTBL40 melanoma cells induced by carbon ions of different let

Exposure to irradiation can trigger the p53 tumor suppressor to induce cell growth arrest or apoptosis. This study was conducted in order to evaluate the ability of carbon ions to induce apoptosis. The HTB140 melanoma cells were irradiated at three positions along the Bragg curve of the 62 MeV/u 12C ion beams. In this way the cells were exposed to different high linear energy transfer (LET) values. The percentage of apoptotic cells was evaluated by flow-cytometry and the corresponding apoptotic indexes were calculated. The expression of apoptosis-associated proteins, p53 and Bax was estimated by Western blot analyses. A dose dependent increase of apoptosis was noticed in all irradiation positions. When moving along the Bragg curve, i.e., with the raise of LET, the level of apoptosis increased, but was somewhat attenuated for the highest LET value. The corresponding apoptotic indexes ranged from 2.45 to 7.71. Moreover, the induction of apoptosis was associated with p53 and Bax up regulation