The radiosensitizing and toxic effects of RSU-1069 on hypoxic cells in a murine tumor.

RSU-1069 is one of a group of compounds of particular interest in radiobiology, since it combines the nitroimidazole ring with a side chain bearing a monofunctional alkylating agent. This compound has been shown to be a potent radiosensitizer both in vitro and in vivo. Furthermore, it has recently been shown to be an effective hypoxic cell cytotoxin in vitro. Our studies have been carried out using the SCCVII squamous carcinoma implanted subcutaneously in C3H mice, using a technique we recently developed which facilitates isolation of tumor cell subpopulations from known locations relative to the tumor blood supply. The response of the separated tumor subpopulations was assessed using a soft agar clonogenic assay. For radiosensitization studies, RSU-1069 was administered i.p. at 0.5 mumol/g 20 min before irradiation and the tumors excised 20 min after irradiation. For toxicity studies, tumors were excised 16-18 hr after RSU-1069 administration. The results obtained to date clearly demonstrate that RSU-1069 is an efficient hypoxic cell radiosensitizer and cytotoxin in this murine tumor and has little effect on well perfused (i.e., oxic) cells.