v- myb Transformation of Xeroderma pigmentosum human fibroblasts: Overexpression of the c- Ha- ras oncogene in the transformed cells

Human Xeroderma pigmentosum “normal” fibroblasts AS16 (XP4 VI) were transformed after transfection with a recombinant v- myb clone. In this clone (pKXA 3457) derived from avian myeloblastosis virus (AMV), the expression of the oncogene sequences is driven by the AMV U-5 LTR promoter. The transformed cells (ASKXA), which have integrated a rearranged v- myb oncogene, grow in agar, are not tumorigenic in nude mice, and express a 45-kDa v- myb protein. The HMW DNA of these cells transform chicken embryo fibroblasts. The c- Ha- ras oncogene is overexpressed in the ASKXA cells but not in the parental “normal” AS16 cells and a revertant clone (ASKXA Cl 1.1 G). Our results lead to the conclusion that the XP fibroblasts are phenotipically transformed by the presence of the transfected v- myb oncogene, which is able to induce an overexpression of the c- Ha- ras gene.