Radiation and drug response of the rat glioma RG2.

A clonogenic cell assay was developed for the chemically induced rat glioma RG2 that allows in vivo, in vitro, and in vivo to in vitro studies of cell survival after experimental therapy. RG2 monolayer cells were resistant to BCNU up to high concentrations. The radiation survival curves were characterized by a Do of 2.4 gray and n = 2.2 for monolayer cells, a Do of 3.5 gray and n = 1.3 for cells irradiated as brain tumors in air-breathing rats, and a Do of 5.9 gray and n = 1.2 for cells irradiated as brain tumors in nitrogen-asphyxiated rats. There was no evidence of a radiobiologically hypoxic fraction of cells in the brain tumors, but their radiosensitivity was definitely smaller than that of monolayer cells.