Figure 3

(A) Effect of COX-2 inhibition on VEGF secretion by recombinant soluble ICAM-1-treated CT26 cells. In some experiments, CT26 cells received 1 μg/ml of celecoxib 30 min prior to treatment with sICAM-1. VEGF concentration was measured with ELISA in 18-hour supernatants obtained in serum-free culture conditions. Data represent the mean ± SD of three separate experiments, each in six replicates (n = 18). Differences in VEGF secretion with respect to untreated (*) and sICAM-1-treated (**) monolayer-cultured cells, and with respect to untreated (#) and sICAM-treated-(##) 3D-spheroid-cultured CT26-CC cells were statistically significant (p < 0.01) by ANOVA and Bonferroni's post-hoc test. (B) Interaction of tumor LFA-1-expressing CT26 cancer cells with hepatic sinusoidal endothelial cells, via membrane and soluble ICAM-1, induces tumor VEGF overproduction via COX-2 pathway. Next, VEGF induces endothelial cell migration towards a vascular micrometastasis promoting angiogenesis.