PTK7 expression and induction in vascular endothelial cells. (A) PTK7 expression was determined in HUVECs, a mouse endothelial cell line (MS1), and bovine arterial endothelial (BAE) cells by Western immunoblotting. (B) PTK7 expression was determined in the presence of 20 ng/mL VEGF-A or FGF-2, or 30 ng/mL IL-1β or TNF-α, added to cells in 6-well plates after 24 hours of serum starvation. Twenty-four hours later, MS1 cells were collected and immunoblotting performed (*P < .05, **P < .01, compared with control). (C) Induction of PTK7 was investigated 24 hours after treatment with VEGF-A (20 and 50 ng/mL) in MS1 cells using Western immunoblot.