Effects of sensitizers on cell respiration: III. The effects of hypoxic cell radiosensitizers on oxidative metabolism and the radiation response of an in vitro tumour model.

Physiological factors are important when considering the effects of radiosensitizers on the radiation response of complex systems such as multicellular spheroids. In this system, under conditions of unlimited nutrient supply, cells are rendered hypoxic by metabolism. Thus, using the spheroid system as an in vitro model of the tumour-cell microenvironment, we have determined the relative contribution of radiosensitization and respiratory effects of a number of electron-affinic sensitizers having potential clinical use. These studies are indicative of physiological responses at the cellular level, and suggest optimal drug administration schemes for obtaining maximal radiation response in vivo hypoxic cell sensitizers.