Enhancement of Cellular Tumorigenic Potential by Human Papilloma Virus and Epstein-Barr Virus Co-Infection
Mingxia Shi, Ru Jiang, Olesander Ekshyyan, Cherie-Ann O Nathan, Lindsey Fletcher, Rona S Scott. Louisiana State University Health Science Center, Shreveport, LA
Background: Human Papilloma Virus (HPV) associated head and neck squamous cell carcinoma (SCC) are noted mostly in tonsil and base of tongue (BOT) and rarely in the rest of the oral cavity. The tonsil and BOT are histologically composed of lymphoid rich tissues that differentiate these two sites from all the other tissues in the oral cavity. The only other site in the head and neck with predominant lymphoid tissue is the nasopharynx, and carcinomas at this site are associated with Epstein-Barr virus (EBV). Examination of tonsillar and BOT SCC showed the presence of EBV/HPV co-infection in 25% and 50% of tumors, respectively.
Design: To determine the potential of EBV and HPV to synergize in the development of head and neck tumors, we developed an in vitro model to measure the tumorigenic potential of cell lines expressing various combinations of EBV and/or HPV. Normal oral keratinocytes were stably transfected with a plasmid carrying HPV16 E6 and E7 oncoproteins to mimic HPV infection followed by infection with a recombinant EBV strain. As control for selection, cognate vector lacking E6E7 or lacking EBV genes was transfected. EBV positivity and expression of E6 and E7 were confirmed by using reverse-transcription PCR with gene specific primers and western blotting. The expression of viral transcripts representative of the three EBV latency states was detected by RT-PCR, and the cell proliferation assay and cell invasion assay were conducted in these EBV/HPV cell lines.
Results: EBV-infected NOK displayed a type II latency profile that switched to a type III latency pattern with E6E7 expression. Cell proliferation was not significantly enhanced in NOK co-expressing E6E7 and EBV. However, co-expression of E6E7 and EBV cells significantly increased cellular invasiveness relative to parental, or E6E7 and EBV alone.
Conclusions: Our data indicated that co-infection of HPV and EBV not only influenced the EBV latency profile, but also enhanced cellular invasiveness, consistent with the metastatic nature of HNSCC tumors. Further studies are planned to evaluate the molecular basis for the enhanced tumorigenic potential by HPV/EBV co-infection using this in vitro model.
Monday, March 4, 2013 1:00 PM
Poster Session II # 276, Monday Afternoon