OP006: HPV16-E2/E4, -E6 AND -E7 genes and HPV-disrupted human genes show large variation in expression levels in OSCC independent of the viral physical status

Abstract

Purpose Infection with high-risk human papillomavirus (HPV) type 16 is an independent risk factor for the development of oropharyngeal squamous cell carcinomas (OSCC). However, it is unclear whether viral integration is an essential hallmark in the carcinogenic process of OSCC and whether HPV integration correlates to the level of viral gene transcription and influences the expression of disrupted genes. Material and methods HPV16 integration sites were assessed in 75 patients with HPV16-DNA- and p16 INK 4 A -positive OSCC using Detection of Integrated Papillomavirus Sequences (DIPS)- as well as Amplification of Papillomavirus Oncogene Transcripts (APOT)-PCR. Quantitative RT-PCR assays were carried out to determine the viral E2/E4, E6 and E7 gene expression levels. Expression levels of 7 human genes disrupted by the virus were extracted from mRNA expression profiling data of 32 OSCC. Nuclear localization of HPV16 was visualized using Fluorescence In Situ Hybridization (FISH) in 59 OSCC, and corresponding viral copy numbers were assessed by quantitative RT-PCR in 61 tumors. Results We identified 37 HPV16-human fusion products indicating viral integration in 29 (39%) OSCC. In the remaining tumors (61%) only episome-derived PCR products were detected. When comparing OSCC with or without an integration-derived fusion product, we neither found significant differences in the mean expression of the viral genes E2/E4, E6 and E7, the nuclear FISH staining patters nor the viral copy numbers per cell. The expression of the HPV-invaded genes also did not significantly differ when comparing the expression in the affected tumor with the expression of that gene in either group of OSCC. Conclusions In conclusion, our data do not support the hypothesis that integration affects the levels of viral and/or HPV-disrupted human gene transcripts. Thus constitutive, rather than a high level, of expression of oncogene transcripts appears to be required in HPV-related OSCC.