Knockdown of ECSCR in HUVECs results in reduced migration, apoptosis, and proliferation. (A) HUVECs and HPAECs were transfected with ECSCR siRNA or control lacZ siRNA and assayed for transmigration activity in Boyden chambers. ECSCR knockdown cells showed reduced transmigration activity relative to controls in response to 10% fetal bovine serum (HUVECs: 38% of control; HPAECs: 57% of control; P < .05 for both, Student paired t test). (B) ECSCR siRNA or control lacZ siRNA-transfected HUVEC transmigration activity in response to purified VEGF (25 ng/mL). (ECSCR knockdown, 117% of unstimulated vs 157% of unstimulated for control knockdown; P < .05.) (C) Knockdown cells were contact inhibited then analyzed for annexin translocation by flow cytometry. ECSCR knockdown resulted in strongly reduced apoptosis compared with lacZ controls (11% annexin positive vs 36% in controls; P < .01). (D) HUVECs were transfected with siRNA constructs, contact inhibited, serum starved, and then released from inhibition in the presence or absence of VEGF. Proliferation was assayed by incorporation of [³H]thymidine. ECSCR knockdown resulted in greatly decreased VEGF-stimulated thymidine incorporation (104% of unstimulated vs 281% in control cells; P < .001). Results are representative of 3 independent experiments.