Landscape of genetic alterations in oropharyngeal squamous cell carcinoma (OPSCC) based on RNA-seq and WES analysis of FFPE samples and correlation with data from TCGA.

Abstract

e17527 Background: Whole human exome sequencing (WES) has identified well characterized somatic mutations (such as TP53, CDKN2A, PIK3CA and HRAS) in patients with squamous cell carcinoma of the head and neck (SCCHN). We sought to optimize a combined RNA-seq and WES approach for identifying actionable mutations and gene expression signatures in p16 + versus - OPSCC. Methods: Relying on formalin fixed and paraffin embedded (FFPE) samples we applied a minimal mutation and copy number content (151 genes) on DNA and an extensive RNA panel on a total of 27 OPSCC (22 p16 +, and 5 p16 -). SAMSeq was used to identify the differentially expressed genes. Unsupervised hierarchical clustering of the TCGA OPSCC samples with available p16 status (n = 31) was performed for external validation of the results. Statistical significance was further tested by Fisher’s exact test. Results: We identified a gene signature differentially expressed in p16+ and p16- OPSCC. External validation showed a significant association between gene expression and p16 status (P = 0.00033). We did not however find an association with mutation burden and smoking history. A number of pathways associated with this gene signature such as NCAM1 may have relevant biologic implications in OPSCC. Conclusions: Our results underscore the reliability of integrating data from FFPE samples in distinguishing gene signatures characteristic of p16 + versus p16- OPSCC; these signatures need to be further explored for their biologic relevance in OPSCC (This research was supported by a grant NCI R21 CA182661-01A1to NFS and GZC).