Ubiquitous presence of E6 and E7 transcripts in human papillomavirus?Positive cervical carcinomas regardless of its type

The presence of human papillomavirus (HPV) DNA in almost all of the cervical carcinomas is one of the most compelling evidence for the viral carcinogenesis. HPVs are thought to induce cervical carcinoma most likely through the expression of E6 and E7 genes presumably by inactivating the tumor suppressor proteins, p53 and pRb, respectively. Thus far, the presence of HPV E6 and E7 transcripts have been identified only in cervical carcinoma-derived cell lines harboring type 16 or 18, and in a limited number of cervical neoplasia specimens positive for type 16, 18, 33 or 51. To see whether the expression of E6 and E7 genes is an essential finding in HPV-positive cervical carcinoma and cervical intraepithelial neoplasia (CIN), we constructed a reverse transcription-polymerase chain reaction (RT-PCR) assay using a pair of consensus primers in the E6 and E7 regions. Using the assay, E6 transcripts (full-length E6/E7 transcripts) and E7 transcripts (spliced E6/E7 transcripts, E6* mRNA) were identified in 97% (30/31) and 100% (all 31) of cervical carcinomas and in 100% (all 23) and 74% (17/23) of CINs, respectively. This assay also revealed unknown splice donor and acceptor sites of E6* mRNA of less frequent HPV types 31, 35, 52, 56, 58 and 59 based on sequence analyses of the PCR products. Thus, the present study demonstrates that E6 and E7 transcripts of HPV exist in virtually all HPV-positive cervical neoplasia specimens except for the absence of E7 transcripts in some of CINs.