MOLECULAR ANALYSIS OF EPISOMAL HUMAN-PAPILLOMAVIRUS TYPE-16 DNA IN A CERVICAL-CARCINOMA CELL-LINE

Integration of human papillomavirus type 16 DNA sequences into host DN A is a frequent event in cervical carcinogenesis. However, recent stud ies showing that HPV16 is present exclusively in an episomal form in m any primary cervical cancers suggest that HPV16 can transform target c ells by mechanisms that do not require viral integration. We have esta blished a cervical carcinoma cell line that harbors episomal copies of HPV16 DNA of approximately 10 kb. Restriction enzyme and two-dimensio nal gel analysis confirmed that HPV16 DNA was extrachromosomal with bo th monomeric and multimeric forms present. HPV16 was maintained as epi somes with passage both in culture and after subcutaneous growth in nu de mice. The 10 kb viral genome, consisting of a full-length copy of H PV16 and a partial duplication of the long control region and the L1 o pen reading frame, exhibited transforming activity comparable to proto type HPV16. This cell line should provide a useful model system for st udying the biological significance of the physical state of the HPV16 genome in cervical carcinoma cells. (C) 1997 Elsevier Science B.V.