Radiation-induced apoptosis

This review concerns the apoptosis which is a kind of cell death defined in 1972 and differs from the necrosis in the morphology and function. Apoptosis occurs in the order of pycnosis, cell atrophy, blebbing and cell fragmentation into apoptotic bodies and is an active process while necrosis is a passive one. The molecular mechanism involves the signal reception for apoptosis; its transduction and gene expression; protein degradation by caspases and DNA fragmentation by endonucleases; and removal of apoptotic bodies. Radiation-induced cell death involves the interphase and reproductive (or mitotic) death, the former of which, the authors found, was a typical apoptosis in thymocytes and is important in radiation therapy. A part of the latter death is also considered to be apoptosis. In the radiation-induced apoptosis, there are processes through p53 and interferon regulatory factor-1, and through membrane ceramide formation. Radiation-induced apoptosis has such means as the cause of radiation damage, the mechanism for the damage removal and the therapy of cancer. Research of the radiation-induced apoptosis was concluded important in the future. (K.H.)