| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
1.p53-dependent and p53-independent apoptosis induced by radiation, and RBE of carbon ion beams :
The aim of this study is to evaluate the relationships between p53 status and radiation-induced apoptosis. Male mice (C57BL/6) and human tumors transplanted to nude mice were irradiated with 200 kV X-rays or carbon ion beams (290MeV/u, 6cm SOBP,NIRS). The incidence of apoptosis of radiosensitive normal tissues and tumor cells having wild-type p53 increased markedly following irradiation (p53-dependent apoptosis), although the incidence of apoptosis of radioresistant tumor cells having mutant-type p53 increased slightly (p53-ihdependent apoptosis). The RBE values of carbon ion beams evaluated by apoptotic cell death were suggested to be more than 4 for a radioresistant tumor having mutant-type p53, about 3 for radiosensitive tumors having wild-type p53, and 1.5-2.1 for radiosensitive normal tissues having wild-type p53 (spermoatogonia of the testis, crypt cells of the small intestine, and neuronal cells of the hippocampus). Furthermore, the RBE values evaluated by the chronic changes of the testis were 1.2-1.6. These results indicated that the heavy ion beams induce more p53-independet apoptosis than X-rays, and the differences in the RBE values between tumors and normal tissues might contribute to a favorable therapeutic ratio in radiotherapy.
2.Radiation therapy for radiosensitive human tumors :
Treatment results of radiation therapy for radiosensitive human tumors (malignant lymphoma, germinoma, etc.) were analyzed, and the efficacy of radiation was reevaluated.
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