VEGF expression in cetuximab resistance development in patients with squamous cell carcinoma of the tongue and oral mucosa.

Abstract

e18072 Background: Clinical course and aggressiveness of a tumor, as well as the subtle mechanisms of its pathogenesis are related to vascularization, which in turn is determined by the ability of transformed cells to synthesize a wide range of biologically active substances. Among modern approaches to cancer treatment, special attention is paid to anti-EGFR agents reducing tumor vascularization. The purpose of this study was to analyze VEGF expression in tumor vessels in patients with squamous cell carcinoma of the tongue and oral mucosa developing cetuximab resistance. Methods: The study included 45 patients with squamous cell carcinoma of the tongue and oral mucosa T3-4N0-1M0. The patients were divided into 3 groups: group 1 – all patients before treatment; group 2 – patients after standard chemotherapy with cisplatin and fluorouracil; group 3 – patients after chemotherapy in combination with targeted therapy with cetuximab. Immunohistochemical study was performed on sections from paraffin blocks of tumors using monoclonal murine anti-VEGF antibodies (clone VG1, Thermo Scientific) diluted 1:150. The Reveal Polyvalent HRP-DAB Detection System was used. The significance of differences was assessed using the Mann Whitney and Wilcoxon tests calculated using the STATISTICA 10.0 program (StatSoftInc., USA). Results: Changes in the density of vessels stained with the VEGF marker were studied in tumor cells of patients in all groups. Patients in group 1 had from 3 to 10 vessels in one field of view; in group 2 – from 2 to 6 vessels in 70% of cases (21) and up to 15 vessels in 30% of cases (9); in group 3 – only solitary vessels. The average numbers of microvessels stained with the VEGF marker per field of view were 6.5±1.52; 4.5±1.71; 1.0±0.28, respectively. Quantification of intratumoral microvascular density showed that the minimum number of microvasculature vessels in the field of view was observed in patients who received chemotherapy and targeted therapy with cetuximab. The value was 5 times lower compared to initial values, and 4 times lower than in patients who received only standard chemotherapy (the Mann Whitney test, p < 0.05). The statistical analysis according to the Wilcoxon test on the effect of targeted therapy (comparison between groups 2 and 3) revealed a statistically significant effect of cetuximab for this marker (p = 0.028). Conclusions: Immunohistochemical analysis of the VEGF neoangiogenesis factor in squamous cell carcinoma of the tongue and oral mucosa confirmed the effectiveness of targeted therapy with cetuximab.