Expression of VEGF-A/VEGFR-2 pathway in feline oral squamous cell carcinoma in vitro and anti-tumour effect of Bevacizumab in a xenograft model

Vascular endothelial growth factor A (VEGF-A) plays a key role in tumour angiogenesis, proliferation, and metastasis, contributing to malignant transformation. Bevacizumab is a monoclonal antibody (mAb) which binds to VEGF-A, preventing it from binding to and activating VEGF receptor 2 (VEGFR-2) on endothelial and cancer cells, thereby resulting in anti-tumour effects. Bevacizumab is employed in treatment of numerous human malignancies and showed promising results also against head and neck squamous cell carcinoma (HNSCC). Feline oral SCC (FOSCC), the counterpart of HNSCC in cat, is characterized by aggressive behaviour, local invasion and metastasis, and is unresponsive to standard treatments, thus displaying poor prognosis. In this study, we characterized expression of VEGF-A/VEGFR-2 pathway in FOSCC cell lines SCCF1, SCCF2 and SCCF3, and tested the response to Bevacizumab both in vitro and in a xenograft mouse model of SCCF3 expressing luciferase. RT-PCR and Western blotting (WB) analysis showed expression and activation of VEGF-A/VEGFR-2 axis at steady-state and serum-starved conditions in the three cell lines, suggesting the presence of a functional autocrine signalling loop. Treatment of cells with Bevacizumab at 50 or 100 µg/mL for 6 h inhibited activation of VEGFR-2 and its downstream mediator AKT, as shown by WB and densitometric analysis. Most importantly, volumetric and bioluminescence analysis demonstrated that Bevacizumab (5 mg/kg, twice a week) suppressed tumour growth in the xenograft model. Our data suggest that Bevacizumab displays anti-cancer activity against FOSCC in vitro and in vivo, paving the way for translational studies aimed at introducing molecular targeted therapy with mAbs in veterinary oncology.