Long isoform of VEGF stimulates cell migration of breast cancer by filopodia formation via NRP1/ARHGAP17/Cdc42 regulatory network

VEGF stimulates endothelial cells as a key molecule in angiogenesis. VEGF also works as a multifunction molecule, which targets a variety of cell members in the tumor microenvironment. We aimed to reveal VEGF‐related molecular mechanisms on breast cancer cells. VEGF‐knocked‐out MDA‐MB‐231 cells (231(VEGFKOex3)) showed rounded morphology and shorter perimeter (1.6‐fold, p < 0.0001). The 231(VEGFKOex3) cells also showed impaired cell migration (2.6‐fold, p = 0.002). Bevacizumab treatment did not induce any change in morphology and mobility. Soluble neuropilin‐1 overexpressing MDA‐MB‐231 cells (231(sNRP1)) exhibited rounded morphology and shorter perimeter (1.3‐fold, p < 0.0001). The 231(sNRP1) cells also showed impaired cell migration (1.7‐fold, p = 0.003). These changes were similar to that of 231(VEGFKOex3) cells. As MDA‐MB‐231 cells express almost no VEGFR, these results indicate that the interaction between NRP1 and long isoform of VEGF containing a NRP‐binding domain regulates the morphology and migration ability of MDA‐MB‐231 cells. Genome‐wide gene expression profiling identified ARHGAP17 as one of the target genes in the downstream of the VEGF/NRP1 signal. We also show that VEGF/NRP1 signal controls filopodia formation of the cells by modulating Cdc42 activity via ARHGAP17. Among 1,980 breast cancer cases from a public database, the ratio of VEGF and SEMA3A in primary tumors (n = 450) of hormone‐receptor‐negative breast cancer is associated with ARHGAP17 expression inversely, and with disease free survival. Altogether, the bevacizumab‐independent VEGF/NRP1/ARHGAP17/Cdc42 regulatory network plays important roles in malignant behavior of breast cancer.