Inhibition of syntaxin 6 blocks VEGF-induced cell proliferation, migration and, morphogenesis in Matrigel. (A,E) Serum-starved HUVECs were left uninfected (Control) or were infected with syntaxin 6-cyto or syntaxin 16-cyto. (A) Cell proliferation assays were carried out using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. Values are expressed as fold change relative to that in controls. (B) Wound healing in the presence or absence (data not shown) of VEGF as monitored by time-lapse imaging for a period of 24 hours. The wound edges are marked by a solid black line. (C) Quantification of the number of cells migrating into the wound. (D) Directional migration of HUVECs toward VEGF (100 ng/mL) by Boyden chamber assay, with VEGF present in the lower well. The number of migrating cells was normalized to that in unstimulated control cells. (E-F) Matrigel-based tube-formation assay was carried out with HUVECs in the presence of VEGF (100 ng/mL). The number of tubes per field was quantified. Data in panels A, C, D, and F are mean (± SD) from 4 independent experiments. P ≤ .001 in panel A, P ≤ .005 in panel C, and P ≤ .05 in panels D and F.