Immortalization and altered differentiation of human keratinocytes in vitro by the E6 and E7 open reading frames of human papillomavirus type 18

Abstract

The E6-E7 region of human papillomavirus types 16 and 18 is selectively retained and expressed in cervical carcinoma cells. In cultured human keratinocytes, expression of the E6 and E7 open reading frames of human papillomavirus type 18, under the control of its homologous promoter, resulted in high-frequency immortalization. Furthermore, by using a system that allows for stratification of keratinocytes in vitro (raft system), we observed that the morphological differentiation of these E6-E7 immortalized cells was altered such that parabasal cells extended throughout most of the epithelium, with abnormal nuclei present in the upper regions. Examination of E6-E7-expressing cell lines in the raft system at a later passage revealed that complete loss of morphological differentiation had occurred. E7 alone was a much less effective immortalizing agent than E6 and E7 together and acted only minimally to alter morphological differentiation in vitro. No such activities were found for E6 alone. High-frequency transformation of human epithelial cells thus appears to require expression of both E6 and E7 gene products.

Impact of modulation of telomerase and cancer stem‐cell marker OCT4 axis in cervical cancer pathogenesis with underlying HPV16 infection

“…The finding was in concordance with the earlier published scientific studies. 10,33 The HPV16 E6 oncoprotein was significantly associated with increased viral load (E6-viral load: Pearson correlation = 0.864, P = .012; and Spearman's rho = 0.671, P = .092) similar to published reports 34 who underlined that via high level of viral load the episomal HPV16 over expresses the E6 mRNA in invasive cervical cancer.…”

Human papillomavirus testing and molecular markers of cervical dysplasia and carcinoma

“…95 Expression of E6/E7 oncogenes is required for continued degradation of p53 and Rb and the resulting malignant transformation of cells. 96 The PreTect HPV-Proofer assay (NorChip AS, Klokkarstua Norway) is a commercially available assay (in Europe only) to detect E6/E7 mRNA by real-time multiplex nucleic acid sequence-based amplification and detection of molecular beacon probes. 97 An internal control (human U1 small nuclear ribonucleoprotein-specific A protein mRNA) is used to guard against false-negative results due to degradation of RNA.…”

Selective suppression of monocyte chemoattractant protein‐1 expression by human papillomavirus E6 and E7 oncoproteins in human cervical epithelial and epidermal cells

“…Regardless of mechanism, our data indicate that expression of E6 and E7 did not immediately result in MCP-1 suppression (Figs. 3,4). While it is possible that this is a consequence of the persistence of E6/E7-negative cells in culture, cells had been transduced 3 weeks prior to the analysis at 45 PD.…”

“…The products of the viral oncogenes E6 and E7 from high-risk viruses have been implicated in carcinogenesis because their expression is sufficient for the immortalization of primary human keratinocytes in vitro. [2][3][4] E6 targets p53 for ubiquitin-mediated degradation, while E7 binds and inactivates the product of the tumor-suppressor gene Rb. 5,6 Despite this efficient program for inactivating tumor-suppressor proteins, development of cervical carcinoma is a multistep process for which E6 and E7 are necessary but not sufficient.…”