The radiation response of human malignant melanoma cells in vitro and in vivo.

The three malignant melanoma cell lines used are characterized by having high, intermediate, and low quantities of pigment production. The response of these malignant melanoma cells to X-ray in vitro does not correlate with a model of the classically radioresistant tumor cell that clinical experience might predict. The in vitro melanoma cells were only slightly more resistant to X-rays than the nontumor in vitro Chinese hamster ovary cell line tested. The responses to X-rays of all three melanoma lines were the same (11= 40, †̃Do = 100 rads). The response to ultraviolet light varied with the amount of pigment present in each cell line. The strain producing a high quantity of pigment was the most UV resistant (ii 3, b@, 57 ergs/sq mm). The strain producing alow pigment quantity was the most UV sensitive (ii 3, D0 31 ergs/sq mm). All melanoma strains were more resistant to UV than the Chinese hamster ovary cell line (Ii = 10, D0 = 20 ergs/sq mm). Survival determinations made as a function of time between two fractionated UV doses of 100 + 100 ergs/sq mm indicated that these melanoma cells possessed ability to recover from sublethal UV damage.