Rearrangements of the upstream regulatory region of human papillomavirus type 6 can be found in both Buschke-Löwenstein tumours and in condylomata acuminata.

Clinically malignant Buschke-Löwenstein tumours and benign condylomata acuminata are caused by human papillomaviruses (HPVs), predominantly HPV-6 and -11. In some cases, the HPV-6 genomes found in Buschke-Löwenstein tumours and in verrucous carcinomas differ from HPV-6b isolated from a benign genital wart, by rearrangements of the upstream regulatory region (URR). To evaluate the frequency and role of mutations of the URR of HPV-6 we analysed 42 condylomata acuminata and four Buschke-Löwenstein tumours by the polymerase chain reaction and restriction enzyme cleavage. Using only four different restriction enzymes we could demonstrate four distinct restriction patterns, indicating that naturally occurring HPV-6 isolates display a high degree of DNA polymorphism within the URR. One Buschke-Löwenstein tumour and two condylomata acuminata yielded rearranged URRs with DNA duplications. All three lesions harboured multiple HPV-6 variants, suggesting that cellular or environmental factors facilitate the development of rearrangements. Therefore, rearrangements of the URR may represent only secondary events in condylomata acuminata and Buschke-Löwenstein tumours which do not necessarily confer a higher malignant potential to the infected cell.