RADIATION-INDUCED APOPTOSIS - RELEVANCE TO RADIOTHERAPY

Radiation-induced apoptosis is reviewed in terms of: (a) the identific ation of apoptotic and necrotic cells, (b) observations in vitro and i n vivo of radiation-induced apoptosis, (c) genes controlling apoptosis , (d) evidence that the target may be the plasma membrane or nuclear D NA, (e) quantitative comparisons of apoptotic death and reproductive ( clonogenic) death, (f) the importance of radiation-induced apoptosis i n radiotherapy, and (g) studies of radiation-induced apoptosis that ar e needed, High priority should be placed on determining the molecular pathways that are important in the expression and modulation of radiat ion-induced apoptosis, Specifically, the events that modulate the apop tosis that occurs in interphase before the cell can divide should be d istinguished from the events before division that modulate the misrepa ir of DNA damage, that results in chromosomal aberrations observed in mitotic cells, which in turn cause the progeny of the dividing cell wi th aberrations to die by either apoptosis or necrosis, Then, molecular events that determine whether a cell that divides with or without a c hromosomal aberration will produce progeny that apoptose or necrose ne ed to be identified, These considerations are important for determinin g how medulation of radiation-induced apoptosis will affect the ultima te clonogenic survival, and possibly genomic instability in the surviv ing progeny.