The E7 Protein of Cutaneous Human Papillomavirus Type 8 Causes Invasion of Human Keratinocytes into the Dermis in Organotypic Cultures of Skin

Abstract

Human papillomaviruses (HPV) have been implicated in the development of nonmelanoma skin cancer (NMSC). The molecular mechanisms by which these viruses contribute towards NMSC are poorly understood. We have used an in vitro skin-equivalent model generated by transducing primary adult human epidermal keratinocytes with retroviruses expressing HPV genes to investigate the mechanisms of viral transformation. In this model, keratinocytes expressing HPV genes are seeded onto a mesenchyme composed of deepidermalized human dermis that had been repopulated with primary dermal fibroblasts. Expression of the HPV8 E7 gene caused both an enhancement of terminal differentiation and hyperproliferation, but most strikingly, the acquisition of the ability to migrate and invade through the underlying dermis. The basement membrane integrity was disrupted in a timedependent manner in areas of invading keratinocytes, as evidenced by immunostaining of its protein components collagen types VII, IV, and laminin 5. This was accompanied by the overexpression of extracellular matrix metalloproteinases MMP-1, MMP-8, and MT-1-MMP. These results suggest that the cutaneous HPV type 8 that is frequently found in NMSC of epidermodysplasia verruciformis patients may actively promote an invasive keratinocyte phenotype. These findings also highlight the importance of epithelial-extracellular matrixmesenchymal interactions that are required to support cell invasion. (Cancer Res 2005; 65(6): 2216-23)

Role of HPV E6 proteins in preventing UVB-induced release of pro-apoptotic factors from the mitochondria

“…• C. Organotypic cultures were essentially prepared on de-epidermalized dermis as previously described [46]. Briefly, the reticular dermal surface was repopulated with human fibroblasts and keratinocytes were seeded on the papillary dermal surface and allowed to form a confluent monolayer.…”

Loss of p53 or p73 in human papillomavirus type 38 E6 and E7 transgenic mice partially restores the UV-activated cell cycle checkpoints

“…The beta HPV types were first isolated in skin cancer-prone patients suffering from a rare autosomal recessive genetic disorder called epidermodysplasia verruciformis, but it is now clear that they are commonly found in the skin of healthy individuals (Pfister, 2003). Characterization of the biological properties of the products of the early genes E6 and E7 from different beta HPV types in in vitro and in vivo model has highlighted the potential carcinogenicity of these viruses (Jackson et al, 2000;Caldeira et al, 2003;Akgul et al, 2005;Dong et al, 2005;Schaper et al, 2005;Accardi et al, 2006;Michel et al, 2006). We showed that expression of E6 and E7 from the beta HPV38 in primary human keratinocytes results in inactivation of the tumour suppressor p53 and pRb and immortalization (Caldeira et al, 2003;Accardi et al, 2006).…”

Distinct Functions of Epidermal and Myeloid-Derived VEGF-A in Skin Tumorigenesis Mediated by HPV8

“…Independent oncogenic effects may be expected from E6-MAML1 interactions, which repress the Notch signaling pathway, which has tumor suppressor function in the skin (12). HPV8 E7-induced upregulation of the MT1 matrix metalloproteinase may explain invasion of E7-positive keratinocytes into the dermis of organotypic keratinocyte cultures (13).…”