Abstract
We previously reported a vascular endothelial growth factor (VEGF) autocrine loop in head and neck squamous cell carcinoma (HNSCC) cell lines, supporting a role for VEGF in HNSCC tumorigenesis. Using a phosphotyrosine proteomics approach, we screened the HNSCC cell line, squamous cell carcinoma-9 for effectors of VEGFR2 signaling. A cluster of proteins involved in cell migration and invasion, including the p130Cas paralog, human enhancer of filamentation 1 (HEF1/Cas-L/Nedd9) was identified. HEF1 silencing and overexpression studies revealed a role for VEGF in regulating cell migration, invasion and matrix metalloproteinase (MMP) expression in a HEF1-dependent manner. Moreover, cells plated on extracellular matrix-coated coverslips showed enhanced invadopodia formation in response to VEGF that was HEF1-dependent. Immunolocalization revealed that HEF1 colocalized to invadopodia with MT1-MMP. Analysis of HNSCC tissue microarrays for HEF1 immunoreactivity revealed a 6.5-fold increase in the odds of having a metastasis with a high HEF1 score compared with a low HEF1 score. These findings suggest that HEF1 may be prognostic for advanced stage HNSCC. They also show for the first time that HEF1 is required for VEGF-mediated HNSCC cell migration and invasion, consistent with HEF1's recent identification as a metastatic regulator. These results support a strategy targeting VEGF:VEGFR2 in HNSCC therapeutics.