Affiliations: Department of Pathology, Unit of Molecular Pathology, VU University Medical Center, Amsterdam, The Netherlands | Angewandte Tumorvirologie, Deutsches Krebsforschungszentrum, Heidelberg, Germany
Note: [] Corresponding author: R.D.M. Steenbergen, Department of Pathology, Unit of Molecular Pathology, VU University Medical Center, CCA 1.18, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands. Tel.: +31 20 4442331; Fax: +31 20 4442964; E-mail: r.steenbergen@vumc.nl.
Note: [] R.D.M. Steenbergen was supported by a fellowship of the Royal Netherlands Academy of Arts and Sciences.
Abstract: Background: Previous studies demonstrated a functional involvement of the AP-1 transcription factor in HPV-induced cervical carcinogenesis. Here, we aimed to obtain further insight in expression alterations of AP-1 family members during HPV-mediated transformation and their relationship to potential regulatory (Notch1, Net) and target (CADM1) genes. Methods: mRNA expression levels of c-Jun, JunB, junD, c-Fos, FosB, Fra-1, Fra-2, Notch1, Net and CADM1 were determined by quantitative RT-PCR in primary keratinocytes (n=5), early (n=4) and late (n=4) passages of non-tumorigenic HPV-immortalized keratinocytes and in tumorigenic cervical cancer cell lines (n=7). In a subset of cell lines protein expression and AP-1 complex composition was determined. Results: Starting in immortal stages c-Fos, Fra-2 and JunB expression became up regulated towards tumorigenicity, whereas Fra-1, c-Jun, Notch1, Net and CADM1 became down regulated. The onset of deregulated expression varied amongst the AP-1 members and was not directly related to altered Notch1, Net or CADM1 expression. Nevertheless, a shift in AP-1 complex composition from Fra-1/c-Jun to c-Fos/c-Jun heterodimers was only observed in tumorigenic cells. Conclusion: HPV-mediated transformation is associated with altered AP-1, Notch1, Net and CADM1 transcription. Whereas the onset of deregulated expression of various AP-1 family members became already manifest during the immortal state, a shift in AP-1 complex composition appeared a rather late event associated with tumorigenicity.
