The role of apoptosis in radiation oncology.

Purpose: Apoptosis, as a mode of cell death in irradiated cell populations, has been the subject of literarily hundreds if not thousands of published reports over the past few years. However, in spite of the large body of knowledge related to this subject, the role of apoptosis in determining tumor response to radiotherapy has been and remains poorly understood and controversial. Indeed, some previous reviews have suggested that apoptosis may not be important in this context. The purpose of the present review is to provide some examples of recently reported laboratory investigations that indicate that there is a reasonable expectation that the radiation-induced apoptosis observed has contributed to the tumor response.

Conclusions: We review reports in four areas of research: Molecularly targeted agents, in vivo imaging, Bcl-2 and cancer stem cells. Examples are provided in each of these areas that we believe justify a reassessment of the role that apoptosis plays in radiation oncology.