C-RAF-1 PROTOONCOGENE EXPRESSION RELATES TO RADIOSENSITIVITY RATHER THAN RADIORESISTANCE

The transfection of several oncogenes, particularly c-raf-1, into mamm alian in vitro cell lines has been reported to be associated with incr eased radioresistance. We have thus investigated (by scanning photoden sitometry of western blots) the phenotypic expression of the c-raf-1, c-myc and c-ras protein products in 19 human in vitro cell lines, whos e intrinsic cellular sensitivity to 4 MeV photon irradiation has also been determined. High levels of c-raf-1 proto-oncogene product express ion did not correlate with increased cellular radioresistance, but rat her showed a significant correlation with intrinsic cellular radiosens itivity to photon irradiation for alpha (r = 0.664, P = 0.002), and SF 2 (r = -0.655, P = 0.002). There was no significant correlation for th e ras family, c-myc or actin. These results conflict with those of pre vious studies in which transfection of the activated forms of the c-ra f-1 oncogene were associated with increased radioresistance, and sugge st the possibility that the full length proto-oncogene may influence c ellular radiosensitivity in a different manner from that of the activa ted oncogene.