Human papillomavirus (HPV) type 16 and 33 E6/E7 region transcripts in tonsillar carcinomas can originate from integrated and episomal HPV DNA

Abstract

This study was undertaken to determine whether human papillomavirus (HPV) E6/E7 gene transcription in tonsillar carcinomas is correlated with viral DNA integration. Therefore, tonsillar carcinomas containing HPV-16 (n = 2) and HPV-33 (n = 2) DNA were analysed for the viral physical state and transcription of the E6/E7 region. Southern blot analysis, DNA polymerase chain reaction (PCR) and, eventually, two-dimensional gel electrophoresis revealed indications for the presence of only episomal DNA in the HPV-16-containing biopsies and only integrated DNA in one HPV-33-containing biopsy. The second HPV-33-containing carcinoma, from which one biopsy and two resected tumour specimens were analysed, showed a rather complex physical state profile. The biopsy of this tumour contained only episomal DNA, one resected tumour part contained only integrated DNA and the remaining tumour part contained both integrated and episomal HPV-33 DNA. Independent of the viral physical state, all biopsies and resected tumour parts tested showed the presence of E6/E7 transcripts as determined by RNA PCR. The results indicate that E6/E7 transcripts in tonsillar carcinomas can originate from integrated as well as episomal HPV DNA.