DEPENDENCE ON CLONING METHOD OF SURVIVAL OF HUMAN MELANOMA CELLS AFTER ULTRAVIOLET AND IONIZING-RADIATION

Abstract

The resistance of a human melanoma cell line (MM96) to UV and ionizing irradiation was compared by 2 different methods of cloning, on plates and in agar. A high level of resistance to UV (Do [mean lethal dose] = 320 ergs/mm2) and ionizing irradiation (Do = 4300 rads) was observed when viability of cells was determined by cloning in agar. Melanoma cells were as sensitive as were other cells when viability after irradiation was determined by cloning on plastic plates. The difference in sensitivity to radiation between the 2 methods of cloning can be explained in a model involving damage to membranes as well as to DNA. At least for ionizing radiation, this effect is not restricted to melanoma cells since a [human cervical carcinoma] HeLa subline, HeLa-QB1, showed a similar response. A human lymphoblastoid line (JHP) cloned in agar was sensitive under these conditions (Do = 120 rads).