Presence and distribution of human papillomavirus sense and antisense RNA transcripts in genital cancers

RNA transcription in eight human papillomavirus (HPV) type 16-positive genital carcinomas and in two cervical squamous cell carcinoma (SCC)-derived cell lines was analysed by in situ hybridization using 125I-labelled subgenomic riboprobes. Transcripts corresponding to the E6 and E7 open reading frames were always present, except within the keratinizing layers of differentiated SCCs. Intranuclear E1 gene transcripts were detectable in both cell lines and some tumours whereas E2/E4 transcripts were absent from five of seven assessable tumours, suggesting transcription from integrated viral DNA. When mRNA sense riboprobes were used as controls, no signal was seen in the two cell lines; however, three tumours contained a focal, intense nuclear RNase-sensitive signal using mRNA sense riboprobes. This antisense RNA signal mapped across the whole genome including the noncoding region. In one tumour, the presence of antisense RNA was independently confirmed by using E7 and E2/E4 RNA probes of both orientations in RNase protection assays. Transcription of antisense RNA may be a natural feature of some HPV-positive genital tumours and its possible role in modulating cell behaviour in vivo requires further investigation.