Transformation of rat-embryo immortalized fibroblasts by the E6-E7 region of human papillomavirus type 18.

Plasmids containing the E6 and E7 open reading frames of human papillomavirus type 18 transformed rat-embryo fibroblasts when expressed under the cytomegalovirus promoter. The fibroblasts had been previously immortalized with the large T-antigen gene of the polyomavirus to produce rat embryo fibroblast (large T-antigen) [REF(LT)] cells. REF(LT) cells were transformed by the E6 and E7 sequences to anchorage independence and tumourigenicity, but there were no significant morphological alterations. Transformation by these sequences of REF(LT) cells differed from that achieved by pEJras, in which case significant morphological changes and tumourigenicity in nude mice did occur.