Differences in transformation activity between HPV-18 and HPV-16 map to the viral LCR-E6-E7 region

Homologous, subgenomic fragments of the viral LCR and E6/E7 transforming genes of HPV-18 and HPV-16 were amplified from several primary cervical, penile, and vulvar tumors and cloned into a pUC-18-derived vector. When assayed by a quantitative transformation assay using primary human keratinocytes, the subgenomic regions of HPV-16 and HPV-18 exhibited transforming activities similar to that of the full-length, prototype HPV genomes. More importantly, the HPV-18 LCR-E6-E7 region was approximately 10- to 50-fold more active than that of HPV-16. These studies demonstrate (1) that the transforming activity differences previously observed between prototype HPV-16 and HPV-18 map to the LCR-E6-E7 region, and (2) that individual and independent isolates of HPV-16 and HPV-18 exhibit consistent differences in transforming potential, even when isolated from different anatomic sites.