Tumorigenic Transformation of Primary Rat Embryonal Fibroblasts by Human Papillomavirus Type 8 E7 Gene in Collaboration with the Activated H‐ras Gene

Particular types of human papillomavirus (HPV) are associated with skin cancer of epidermo‐dysplasia verruciformis (EV) patients. Here, we show, for the first time, that the E7 gene of EV‐associated HPV8 possesses a potential oncogenic transforming ability. The HPV8 E7 open reading frame (ORF) and the HPV16 E7 ORF were cloned under the SV40 promoter/enhancer to construct recombinant plasmids pcD2‐8E7 and pcD2‐16E7, respectively. Transfection of primary rat embryonal flbroblasts having an activated H‐ras gene revealed that pcD2‐8E7 as well as pcD2‐16E7 induced transformation of cells In G418‐resistant colonies at an efficiency of 12.3% and 42.9%, respectively. The resulting transformed cell lines induced by pcD2‐8E7 and activated H‐ras were tumorigenic when injected into syngeneic immunocompetent rats. The potential tumorigenicity of HPV8 E7 seemed to be higher than that of HPV16 E7.