KDR and hilar cholangiocarcinoma: Because VEGFR-2 is an upstream protein of Gab1 in endothelial cells [23,25,26] and VEGFR-2 and Gab1 were positively correlated in hilar cholangiocarcinoma, we examined the relationship between them in ICBD-1 cells and demonstrated that VEGFR-2 could regulate the activity of Gab1 in ICBD-1 cells (Figure 2A and B).