Fig. 2. TCPTP activity controls VEGF-dependent responses in endothelial cells. (A) Silencing of TCPTP enhances the proliferation of HUVECs. HUVECs were transfected with no oligo (`–' on the blot), siRNA against TCPTP or a control siRNA (Scr), and TCPTP expression was measured using immunoblotting (inset). Cells were treated with 80 ng/ml VEGF and proliferation of sparse cells that were plated on gelatin was assayed after 16 hours using a BrdU-based assay (mean ± s.d.; n=4-6; ^*P<0.05). (B) Activation of TCPTP decreases chemotaxis of HUVECs. Subconfluent HUVECs were transfected with the constitutively active TCPTP (TC37) or vector control (pCG) and chemotaxis towards VEGF was measured using a Transwell assay for 4 hours. Cells adhering to the bottom of the filter were fixed and stained with crystal violet (micrographs). The number of migrated cells was counted from four randomly selected fields of view in three parallel wells (mean ± s.e.m.; n=3; ^**P<0.01). The western blot shows expression of TC37 in the transfected cells (also detected is the 45-kDa endogenous TCPTP).