Outcome and molecular features of head and neck squamous cell carcinomas (HNSCC) bearing a p16 high phenotype

6031 Background: We have previously demonstrated that p16 expression defines a biologically distinct subgroup of oropharyngeal squamous cell cancers (OSCC). Thus, OSCC can be Class I: human papillomavirus (HPV)-, Class II: HPV16+/p16-, or Class III: HPV16+/p16+. Tumors bearing a high p16 phenotype were associated with superior outcome. Using in situ automated quantitative protein expression analysis (AQUA) to explore the biomarker signatures of these 3 classes we found that beta-catenin, epidermal growth factor receptor (EGFR) and Met were upregulated in class III tumors. Our aim was to validate these findings using an independent cohort. Methods: A tissue microarray composed of 122 specimens from primary HNSCC cases treated with either external beam radiotherapy (EBRT) or gross total surgical resection and EBRT was constructed. Protein expression levels for a panel of 13 markers (EGFR, MET, STAT 3, ERK 1/2, pAkt, PI3Kp85, PI3Kp110, PTEN, p53, Bcl-2, E-cadherin, β-catenin, NFκB) were analyzed using AQUA. P16 protein levels were correlated with progression-free (PFS) and overall survival (OS). Survival analysis was performed by Kaplan-Meier method with log-rank test for assessing statistical significance.Comparison of expression between the p16 positive and p16 negative groups was done using unpaired t-tests. Results: Mean follow-up time for the cohort was 40 months. AQUA scores were divided into quartiles. Survival analysis showed that patients in the top quartile had a significantly better DFS (p = 0.01) and OS (p = 0.002). In multivariable analysis, adjusting for well-characterized prognostic variables, p16 expression retained its prognostic significance. Expression of E-cadherin and β-catenin was significantly higher in the p16 positive versus the p16 negative group (p = 0.014 and p = 0.006, respectively). p16 positive tumors also expressed higher levels of PTEN (p = 0.0009), PI3Kp110 (p = 0.03), NFκB (p = 0.007), and Bcl-2 (p = 0.005). Conclusions: These results validate p16 as a favorable prognostic marker in HNSCC. They also validate beta-catenin as a distinct biomarker in HNSCC bearing high p16 phenotype. Given that HPV+ tumors are p16+, beta-catenin is a candidate biomarker that distinguishes HPV+ versus HPV- HNSCC. No significant financial relationships to disclose.