A novel stimulus, oncogene, induces expression of CD80 (B7-1) gene

CD80, a cell surface molecule found on antigen-presenting cells which particpates in costimulatory signaling, is frequently detected on transformed and tumor cells. We examined the effect of transformation by v-myc, k-ras, and SV40 T antigen oncogenes on the expression of a CD80 promoter/luciferase gene as well as the endogenous CD80 promoter gene in murine fibroblast cell lines. All three transformed cell lines were tumorigenic in nude mice, however expression of the CD80/luciferase transgene or endogenous CD80 was detected only in the v-myc and k-ras transformed cell lines. In both cell lines, CD80 expression was first detected more than 30 passages after transformation. Therefore, induction of CD80 expression was a late event following transformation and was not essential for the establishment of the transformed phenotype.