抄録
We reported that carbon-ion beams induce efficient cellular sensitivity and apoptosis as compared with X-rays in a p53-independent manner. Here, we have studied the radiation sensitivity and apoptosis of a human cultured gingival cancer cell line (Ca9-22) having mutated p53gene after exposure to Fe-ion beams or X-rays. Fe-ion beams were accelerated to 500 MeV/u by a heavy-ion medical accelerator in Chiba (HIMAC) at the National Institute of Radiological Science (NIRS). For X-ray irradiation, a 200 kVp X-ray generator (PANTAK-320S, Shimadzu) was used. The cellular sensitivity was determined by colony-forming assay. The induction of apoptosis was measured by Hoechst 33342 staining of apoptotic bodies.
As a result, 10% survival dose (D10) was about 2 Gy and 7 Gy to Fe-beams and X-rays, respectively. The relative biological effectiveness (RBE) of the Fe-ion beam to X-ray was 3.5, calculated at D10. Little difference was found in kinetic patterns (time course) of apoptosis induction at D10 dose. The percentage of apoptosis after irradiation at D10 with Fe-beams was 1.2 times higher than X-rays. Furthermore, the induced frequency of apoptosis with Fe-beams was 4 times higher than X-rays after 2Gy irradiation.
These findings suggest that heavy-ion beams induced more efficiently cell lethal and apoptosis than X-rays, and are useful even to p53-mutated patients in cancer therapy.
