Viral Integration Analysis Reveals Likely Common Clonal Origin of Bilateral HPV16-Positive, p16-Positive Tonsil Tumors.

Infections with high-risk human papilloma viruses (HPV) are responsible for a significant number of oropharyngeal squamous cell carcinoma (OPSCC), with infection rates currently rising at epidemic rates in the western world. Synchronous bilateral HPV+ tumors of both tonsils are a very rare event whose understanding, however, could provide important insights into virus-driven tumor development and progression and whether such integration events are of clonal origin. In this study we analyzed a single case of a bilateral tonsillar p16+ HPV+OPSCC. The viral integration status of the various tumor samples was determined by integration-specific PCR methods and sequencing, which identified viral insertion sites and affected host genes. Integration events were further confirmed by transcript analysis. Analysis of the tumors revealed common viral integration events involving the gene, as well as a unique event in the gene which resulted in loss of exon one in both tissues that had lost the complex viral integration event. In addition, there were several integration events into intergenic regions. This suggests a common origin but individual evolution of the tumors, supporting the single-clone hypothesis of bilateral tumor development. This hypothesis is further supported by the fact that the two cellular genes and as targets of viral integration are involved in cell migration and ECM-receptor interactions, which provides a possible mechanism for clonal migration from one tonsil to another.