Biomolecular characterization ofOvis ariesPapillomavirus 3 in ovine cutaneous squamous cell carcinoma

Papillomaviruses (PVs) are associated with benign and malignant tumors of the skin and mucous membranes in humans and animals. Cutaneous squamous cell carcinoma (SCC) is the most common form of skin cancer in sheep and several risk factors, such as PV infection, could increase the risk of tumor development.In this thesis, we aim to explore the possible involvement of ovine PVs in cutaneous SCC of the sheep, elucidating the pathways involved in viral neoplastic transformation. Forty SCCs were evaluated by polymerase chain reaction (PCR), in situ hybridization (ISH) and reverse transcription-polymerase chain reaction (RT-PCR) to assess the presence, cellular localization and viral transcriptional activity of ovine PVs. Shotgun proteomic analysis and immunohistochemistry (IHC) were performed to identify and validate infection related proteins. OaPV3 DNA was detected in 26/40 (65%) SCCs by PCR and in 18/40 (45%) SCCs by ISH. The OaPV3 transcriptional activity was shown in 24/40 (60%) SCCs by RT-PCR. The overexpression of proteins related to the apoptosis and cell death pathways was detected in OaPV3 positive SCCs by the shotgun proteomic analysis. Among the overexpressed proteins, the significant deregulation of the cytokeratin 13 detected in OaPV3 positive SCCs was confirmed by IHC.The detection of OaPV3 in a high number of SCCs and the identification of infection related proteins, suggest that the viral infection could represent a key factor in the onset of ovine cutaneous SCC.