Analysis of HPV Integration Sites in Oropharyngeal Squamous Cell Carcinomas
Ernst-Jan M Speel, Christian U Huebbers, Nadine C Olthof, Jutta Kolligs, Simon F Preuss, Uta Drebber, Bernd Kremer, Jens P Klussmann. Maastricht University Medical Center, Maastricht, Netherlands; University of Cologne, Cologne, Germany; University Hospital Giessen, Giessen, Germany
Background: Human papillomavirus (HPV) is an independent risk factor for the development of up to 50% of oropharyngeal squamous cell carcinomas (OSCC). They are mainly associated with HPV16. HPV-positive tumors show typical histopathological and molecular features, and patients show less alcohol and tobacco intake and a more favorable survival than the HPV-negative entity of tumors. Controversy exists on the physical status of the virus in OSCC and on HPV integration being an essential factor for tumor development. Whereas in cervical intraepithelial neoplasia lesions oncogenic HPV integrates into the cellular genome upon transition to carcinoma, for HPV-related OSCC this is unclear.
Design: Our research group has collected a series of 66 HPV-positive OSCC and 6 cell lines. The physical status of these samples was analysed with a set of independent techniques to detect viral integration, including APOT- and DIPS-PCR to detect virus-human fusion sites, the new MLPA-PCR technology to quantify viral load and ratios between HPV oncogenes E6/E7 and E2, and FISH.
Results: HPV16 integration in the cellular genome was identified in 42% of OSCC. HPV integration sites were distributed all over the genome and were preferably found in gene loci, often with reported involvement in tumorigenesis, including BCL2, FANCC, TRAF3 and TP63. In these cases both integration in exon and intron sequences was detected. In addition, half of the integration sites are in close proximity to fragile sites.
Conclusions: In conclusion, this is the first study providing evidence for and a detailed analysis of HPV 16 integration sites in approximately half of HPV-positive OSCC. We were unable to identify viral integration in the remaining tumours by means of APOT and DIPS PCR, indicating that these tumours harbor episomal HPV copies and/or integration of complete episomes. Studies are ongoing to further examine HPV-driven tumorigenesis in both subgroups.
Category: Head & Neck
Monday, March 19, 2012 1:00 PM
Platform Session: Section F, Monday Afternoon