Comparative study of human colonic tumor-derived endothelial cells (HCTEC) and normal colonic microvascular endothelial cells (HCMEC): Hypoxia-induced sVEGFR-1 and sVEGFR-2 levels.

Colorectal carcinoma growth and progression is dependent on the vasculature of the tumor microenvironment. Tumor-derived endothelial cells differ functionally from their normal counterpart. For this reason we isolated microvascular endothelial cells from human colon cancer tissue (HCTEC) and compared them with endothelial cells from normal colonic tissue (HCMEC) of the same donor. Since hypoxia is a universal hallmark of carcinomas, we examined its effects on HCTEC of five patients in comparison with the corresponding HCMEC, with respect to the secretion of the soluble form of the two important vascular endothelial growth factor (VEGF) receptors, VEGFR-1 and -2. After dissociation by dispase/collagenase of central non-necrotic tumor areas obtained from colon carcinomas, HCTEC were isolated using CD31-coated magnetic beads and cultivated as monolayers. Subsequent characterization studies demonstrated the endothelial phenotype, including VEGFR-1 and -2 mRNA and protein expression as well as E-selectin expression, up-regulated after LPS, TNFalpha and IL-1beta stimulation. sVEGFR expression analyses were performed using ELISA. In comparison with HCMEC markedly lower sVEGFR-1 protein concentrations were found in HCTEC. These low sVEGFR-1 levels remain unchanged under hypoxia. In contrast, sVEGFR-2 was significantly decreased in both HCMEC and HCTEC under hypoxic conditions (p