Conventional radiotherapy with X- and gamma-rays is one of the common and effective treatments of cancer. High energy hadrons, i.e., charged particles like protons and (12)C ions, due to their specific physics and radiobiological advantages are increasingly used. In this study, effectiveness of different radiation types is evaluated on the radio-resistant human HTB140 melanoma cells. The cells were irradiated with gamma-rays, the 62 MeV protons at the Bragg peak and in the middle of the spread-out Bragg peak (SOBP), as well as with the 62 MeV/u (12)C ions. The doses ranged from 2 to 24 Gy. Cell survival and proliferation were assessed 7 days after irradiation, whereas apoptosis was evaluated after 48 h. The acquired results confirmed the high radio-resistance of cells, showing better effectiveness of protons than gamma-rays. The best efficiency was obtained with (12)C ions due to higher linear energy transfer. All analyzed radiation qualities reduced cell proliferation. The highest proliferation was detected for (12)C ions because of their large killing capacity followed by small induction of reparable lesions. This enabled unharmed cells to preserve proliferative activity. Irradiations with protons and (12)C ions revealed similar moderate pro-apoptotic ability that is in agreement with the level of cellular radio-resistance.

Vinča Institute of Nuclear Sciences University of Belgrade Belgrade Serbia

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