Expression of vascular endothelial growth factor (VEGF) and its receptors in thyroid carcinomas of follicular origin: A potential autocrine loop

Objective: The aim of this study was to clarify the role of vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) pathways in thyroid tumourigenesis. Methods: We examined VEGF, VEGFR-1 and VEGFR-2 expression on 34 papillary thyroid carcinomas (PTCs), 18 follicular thyroid carcinomas (FTCs), eight poorly differentiated thyroid carcinomas (PDTCs) and on a thyroid tumour-derived cell line (NPA'87) by immunohistochemistry, reverse transcriptase PCR, immunofluorescence and Western blotting. Results: We have demonstrated that VEGF expression was significantly (P < 0.05) more prevalent in PTCs (79%) than in FTCs (50%) or PDTCs (37%). Similarly, 76% of PTCs, 83% of FTCs and 25% of PDTCs expressed VEGFR-1, whereas 68% of PTCs, 56% of FTCs and 37% of PDTCs expressed VEGFR-2. Coexpression of VEGF and its receptors was observed in 50% of PTCs, 39% of FTCs and 12% of PDTCs, raising the possibility that VEGF may signal in an autocrine loop in these neoplasias, as observed previously for other types of cancer. In agreement with the idea that autocrine VEGF signalling plays an important role in thyroid carcinogenesis, the blockade of either VEGF or its receptors with neutralizing antibodies significantly reduced cell viability and increased apoptosis levels of the VEGFR-positive thyroid tumour cell line NPA'87. Conclusions: Our results highlight a previously undefined VEGF autocrine action in thyroid carcinomas which could play a crucial role in tumour cell survival and could represent a useful therapeutic target for thyroid tumours.