C-raf-1 proto-oncogene expression relates to radiosensitivity rather than radioresistance

Abstract The transfection of several oncogenes, particularly c- raf -1, into mammalian in vitro cell lines has been reported to be associated with increased radioresistance. We have thus investigated (by scanning photodensitometry 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, whose intrinsic cellular sensitivity to 4 MeV photon irradiation has also been determined. High levels of c- raf -1 proto-oncogene product expression did not correlate with increased cellular radioresistance, but rather showed a significant correlation with intrinsic cellular radiosensitivity to photon irradiation for α ( r = 0.664, P = 0.002), and SF 2 ( r = −0.655, P = 0.002). There was no significant correlation for the ras family, c- myc or actin. These results conflict with those of previous studies in which transfection of the activated forms of the c- raf -1 oncogene were associated with increased radioresistance, and suggest the possibility that the full length proto-oncogene may influence cellular radiosensitivity in a different manner from that of the activated oncogene.