Visible-light and X irradiations of Chinese hamster lung cells treated with hematoporphyrin derivative

Single cell suspensions of Chinese hamster lung cells were treated with hematoporphyrin derivative (HPD) and were exposed under aerobic conditions to visible light alone, X rays alone or light and X rays concurrently. Cytotoxicity was assayed using the colony formation ability of cells as the end point. The drug toxicity, phototoxicity, radiosensitization and photoradiosensitization of HPD were examined for a drug concentration of 1 microgram/ml and incubation time of 24 h. In these experiments, the X-ray dose was 3 Gy and the energy fluence of visible light was 0.35 kJ/m2, and both irradiations lasted for 10 min. A significant enhancement in cytotoxicity was observed when the HPD-treated cells were irradiated concurrently with light and X rays. However, no significant enhancement was observed when visible-light and X irradiations were performed sequentially with a 15-min waiting time between the two irradiations.