Enhancement of SV40 transformation by treatment of C3H2K cells with UV light and caffeine: I. Combined effect of UV light and caffeine

Abstract

Treatment of cultured mouse cells, C3H2K, with UV light and/or caffeine enhanced the frequency of SV40-induced transformation. This enhancement depends upon the doses of UV and caffeine and the mode of combination of these agents. Irradiation of cells with increasing doses of UV just before infection resulted in approximately 2-fold enhancement of the transformation frequency up to a dose of 90 ergs/mm 2 and 3.3-fold at 150 ergs/mm 2. Addition of 1 m M caffeine to the medium for 4 days subsequent to infection brought about a 2-fold enhancement. When cells were irradiated and treated with 1 m M caffeine, the enhancement was approximately 4-fold up to a UV dose of 90 ergs/mm 2 and 5.9-fold at 150 ergs/mm 2. When 0.1–4 m M caffeine was added for 4 days postinfection, the absolute number of transformations increased, and an enhancement ratio of 1.3–6.8 resulted. After the addition of the same increasing doses of caffeine to UV-irradiated cells (75 ergs/mm 2), the enhancement of transformation frequency was even higher ranging 2.0 to 13.3. The transformation frequencies thus obtained by the double treatment were always higher than those predicted if UV and caffeine acted additively. The transformation frequency was little affected by the addition of dibutyrylcyclic AMP and theophylline.