Understanding the Molecular Basis of HPV-16 Neoplastic Progression Using an Organotypic Raft Model

Isaacson, Erin (2009). Understanding the Molecular Basis of HPV-16 Neoplastic Progression Using an Organotypic Raft Model. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f20f


High-risk Human Papillomavirus (HPV) types such as HPV-16 cause a spectrum of pre-cancerous neoplastic changes in epithelial sites including that of the cervix. HPV-induced cervical lesions that display low to moderate neoplastic changes are graded as low-grade squamous intraepithelial neoplasia (LSIL). HPV-induced lesions that display high levels of neoplasia are graded as high-grade squamous intraepithelial neoplasia (HSIL).

The previous analyses of cervical lesions of LSIL and HSIL grades have shown that the timing of early and late viral gene expression changes, as the lesion becomes more neoplastic. In HSIL lesions, the HPV-16 E7 surrogate marker MCM-7 persists throughout the epithelium, which coincides with a delay in late gene expression including L1 capsid expression. HSIL lesions often do not support a complete virus life cycle.

The work in this thesis has shown that the Normal Immortalized Human Keratinocyte (NIKS) organotypic raft culture system, which is commonly used to study the HPV-16 life cycle, surprisingly recapitulates the spectrum of gene expression patterns identified in both LSIL and HSIL lesions. In addition, this model also demonstrates pathological changes, which correlate with both LSIL and HSIL phenotypes. This has rendered this system a potential model of episomal HPV-16 induced neoplasia. This auspicious finding led us to make use of this system to explore viral characteristics that potentially underlie HSIL-like gene expression patterns and neoplastic changes. Monolayer LSIL-like and HSIL-like HPV-16 cell lines were subsequently used to evaluate viral copy number, early oncogene expression and growth potential.

In these experiments we have found that episomal HSIL-like HPV-16 cell lines bypass density-dependent growth arrest, which coincides with a rise in E6 and E7 oncogene levels. Finally, we have found that high E6 and E7 expression levels and growth potential at cell-cell contact correlate with MCM-7 persistence in the HPV-16 raft epithelium.

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