Assessment of phosphatidylinositol-3 kinase (PI3K) as a prognostic marker in head and neck squamous cell carcinoma (HNSCC)

Abstract

e17028 Background: Deregulated signaling through phosphatidylinositol 3’-kinase (PI3K) pathway is common in several cancers, including HNSCC. In the present study we investigated the relationship between PI3K protein expression and outcome in patients with HNSCC. 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 PI3K were analyzed using an immunofluorescence-based assay that provides an automated, quantitative analysis of expression within subcellular compartments (AQUA). Primary endpoints were progression-free survival (PFS) and overall survival (OS). Survival analysis was performed by Kaplan-Meier method with log-rank test for assessing statistical significance. Results: Mean follow-up time for the cohort was 40 months. Ninety-seven of 122 cases had sufficient tissue for analysis and continuous AQUA scores were divided into quartiles. Survival analysis showed that patients in the top and bottom quartile had a significantly shorter OS (p = 0.015). In multivariable analysis, adjusting for well-characterized prognostic variables, PI3K expression retained its prognostic significance. Conclusions: Our study suggests that in situ quantitative measurement of PI3K stratifies HNSCC into four expression levels where both low and high levels are associated with a worse outcome. We speculate that transmission of growth factor receptor signals that promote tumor aggression in these low expressers may occur via PI3K/Akt independent mechanisms. It is possible that activation of such alternate pathways in some tumors results in the down-regulation of PI3K expression via a feedback mechanism, producing aggressive tumors bearing a PI3K-low phenotype. No significant financial relationships to disclose.