RESISTANCE OF HUMAN MELANOMA CELLS TO ULTRAVIOLET-RADIATION

Abstract

A series of 5 human melanoma cell lines was demonstrated to be highly resistant to UV radiation, with a D0 [initial dose] of 400 ergs/mm2. Melanotic melanoma cells increased their production of melanin following UV radiation, whereas some amelanotic cells did not. Melanotic and amelanotic melanoma cell lines exhibited the same UV resistance. Melanoma and nonmelanoma cells formed the same numbers of thymine dimers at a given UV dose. These data imply that melanin does not play a major role in protecting DNA of melanoma cells against UV damage in culture. The rates of removal of thymine dimers from DNA of melanoma cells were comparable to those in UV-sensitive, nonmelanoma cell lines, so that rapid excision repair does not explain UV resistance in the melanoma cells. No DNA strand breakage was detected in a melanoma cell line at moderate UV doses.