in Vitro Transformation of Primary Cultures of Neonatal BALB/c Mouse Epidermal Cells with Ultraviolet-B Radiation1

Primary epidermal cultures from neonatal BALB/c mice were used to study the carcinogenic effects of ultraviolet radiation in vitro. These cultures were irradiated once through a Falcon plastic dish cover with an FS40 sunlamp [ultraviolet B, A ~290 to 400 nm] for various lengths of time and maintained for 8 to 12 weeks without subculturing. During this period, most of the cells in the untreated control cultures showed signs of morpho logical differentiation and eventually died. The cultures irradi ated with ultraviolet B radiation also behaved in the same manner except that, in some dishes, small populations of surviving cells began to proliferate and developed into morpho logically distinct foci. Seven long-term cell lines were derived from these ultraviolet-irradiated primary epidermal cell cultures. Six of these cell lines produced tumors when injected s.c. into normal and/or immunosuppressed syngeneic recipients. These tumorigenic cell lines lacked definitive characteristics of differentiated epidermal cells, but the cells possessed inter mediate junctions, suggesting that they were of epithelial origin. Some of these in w'fro-transformed cell lines appeared to be highly antigenic inasmuch as they grew preferentially in im munosuppressed BALB/c mice as compared to their growth in normal syngeneic recipients.