OXYGEN DEPENDENCE OF HEMATOPORPHYRIN DERIVATIVE-INDUCED PHOTOINACTIVATION OF CHINESE-HAMSTER CELLS

Abstract

The O2 dependence of hematoporphyrin derivative (HPD)-induced photoinactivation of Chinese hamster V79 cells was examined. Cells were treated with HPD (25 .mu.g/ml) for 2 h and subsequently exposed to red light (> 590 nm) under either aerated or hypoxic (< 10 ppm O2) conditions. Hypoxic cells were found to be extremely resistant to the lethal effects of HPD and light. The electron-affinic X-ray hypoxic cell sensitizer, SR-2508 [N-(2-hydroxyethyl)-2-nitroimidazole-1-acetamide], did not sensitize hypoxic HPD-treated cells to light. The clinical implications of these findings were discussed, with consideration of the possibility that hypoxic areas in tumors may limit HPD phototherapy.