The EGFR-mTOR pathway and laryngeal cancer angiogenesis

Abstract

Epidermal growth factor receptor (EGFR) is a trans-membrane tyrosine kinase taking part in cell transformation and tumor progression. One of the downstream pathways controlled by EGFR involves the mammalian target of rapamycin (mTOR), a proto-oncogene activated in several cell functions. Recent evidence seems to confirm that both EGFR and mTOR regulate angiogenesis. The aim of this study was to investigate the expression of EGFR and mTOR in laryngeal squamous cell carcinoma (LSCC) cells in a retrospective clinical setting and their correlation with tumor neo-angiogenesis, judged on the grounds of CD105-assessed microvascular density (MVD), and prognosis. We considered 76 consecutive patients with LSCC treated with surgery alone. Immunohistochemical expressions of EGFR, mTOR, and CD105 were measured using image analysis and findings underwent statistical analysis using univariate and multivariate models. We found that nodal status correlated significantly with patient prognosis in terms of disease-free survival (DFS) (p = 0.01). There was a strong direct correlation between mTOR and EGFR expression (p = 0.0003), and between mTOR and CD105-assessed MVD (p = 0.0025). Patients with a CD105-assessed MVD >5.28 % had a significantly higher recurrence rate (RR) (p = 0.026), and a significantly shorter DFS (p = 0.025). On multivariate analysis, only N stage [hazard ratio (HR) 3.54, p = 0.009] and CD105-assessed MVD (HR 2.87, p = 0.027) maintained their independent prognostic significance in terms of DFS. Judging from our promising findings, the EGFR-mTOR pathway should be investigated further to understand its role in LSCC neo-angiogenesis.