Intrinsic radiation sensitivity is conserved during immortalization and malignant transformation steps in carcinogenesis

The authors examined the effect of malignant transformation on the intrinsic radiation sensitivity of epithelial cells. Normal human epidermal keratinocytes (HEK), keratinocytes immortalized by hybrid virus (Ad12-SV-40) and malignant keratinocytes transformed by chemical carcinogens or the Ki-MSV were tested with graded doses of ionizing radiation. Normal HEK cells (D/sub 0/ = 2.24 Gy) proved to be more resistant to radiation than normal human fibroblasts (D/sub 0/=1.45 Gy). Mean inactivation doses D bar ranged from 3.47 to 4.27 Gy confirming a radiation resistant phenotype. This resistance was conserved in immortalized HEK cells and in malignant HEK cells. These experiments suggest that radiation sensitivity is an intrinsic property inherited from the parent cell that may be independent of the steps associated with carcinogenesis