Impact of EGFR immunoexpression on STAT3 activation and association with proinflammatory/regulatory cytokine pattern in laryngeal squamous cell carcinoma

Stimulation of epidermal growth factor receptor (EGFR) results in the activation of signal transducer and activator of transcription-3 (STAT3), a transcriptional factor associated with carcinogenesis. Proinflammatory cytokines are capable of activating a tumor cell death program by reducing EGFR tyrosine phosphorylation. This study aimed to identify EGFR expression in laryngeal carcinoma and determine the relationship with STAT3 and proinflammatory/regulatory cytokine secretion. An analysis of EGFR expression (membranous EGFR-m and cytoplasmic EGFR-c) was performed in tumor tissues by immunohistochemical (IHC) staining in 45 medical cases of laryngeal carcinoma. STAT3 expression in freshly isolated tumor and non-cancerous normal epithelial cells by RT-PCR was analyzed in 24 patients after total larynx resection. The concentrations of TNFα, IL-2, IL-6, IL-8 and IFNγ secreted by purified peripheral blood mononuclear cells (PBMCs) or contained in whole blood samples were measured by ELISA. The relationship between EGFR and mRNA STAT3 expression as well as the level of secreted cytokines was investigated. In our study, 93.3% tumors expressed EGFR-m and 37.8% EGFR-c. It also revealed a statistically significant dependence of the EGFR status on STAT3 expression in neoplastic tissues. Tumors with IHC EGFR-m positive staining >50% of the total number of cells, as well as with EGFR-c positive staining, were characterized by the most frequent presence of STAT3 expression. Our data demonstrate a significant negative relationship between EGFR-m expression and TNFα concentration, and a positive connection between membranous EGFR and IL-8 or IFNγ levels recorded in isolated PBMCs. Furthermore, this study revealed a significant relationship between EGFR-c immunoexpression and IL-8 or IFNγ concentration. Our findings have confirmed a key role of EGFR in determining the proliferative and malignant potential of laryngeal carcinoma.