VEGF enhances the proliferation rate of HIMEC in vitro. VEGF-induced HIMEC proliferation was assessed by 3H thymidine uptake. 4 × 104 HIMEC/well were stimulated for 12 hr with increasing concentrations of VEGF (0, 1, 10, and 100 ng/ml) and pulsed for 6 hr with 1 μCi/ml 3H thymidine. 3H thymidine uptake in total cell lysates was measured in a β-counter. left; VEGF enhanced HIMEC proliferation at 50 ng/ml while low concentrations (i.e. 10 ng/ml VEGF) did not. right; The inhibitory effects of PD098059, CsA and NS398 but not SB203580 on VEGF (50 ng/ml) induced proliferation response in HIMEC. HIMEC pre-incubation with PD098059, CsA and NS398 significantly inhibited VEGF induced proliferation response in HIMEC. All conditions were assessed in triplicate, and data are expressed as percent of control 3H thymidine uptake (0 ng/ml VEGF) ± S.E. *, p < 0.05 versus control.