Enhancement of adenovirus transformation by treatment of hamster cells with ultraviolet irradiation, DNA base analogs, and dibenz(a,h)anthracene.

Abstract

Treatment of hamster embryo cells with ultraviolet irradiation, 5-bromodeoxyuridine, 5-iododeoxyuridine, 5-bromodeoxycytidine, or dibenz(a,h)anthracene prior to the addition of an oncogenic adenovirus, SA7, enhanced the frequency of viral transformation among surviving cells. An increase of over 100-fold was demonstrated with 5-bromodeoxyuridine, 12.5 µg/ml, and over 80-fold with 5-bromodeoxycytidine, 100 µg/ml. Increases in the viral transformation frequency were directly related to dose; however, excessive treatment often resulted in a marked decrease in enhancement. The stimulation of SA7 transformation could not be related to the selection of transformation-sensitive cells, since the absolute number of SA7 foci per plate increased up to 8-fold under conditions where over 90% of the cells were unable to form colonies. These data suggest that the enhancement results from a direct effect upon the cells, thereby increasing their susceptibility to viral transformation.