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

Abstract

Abstract. 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, upregulated after LPS, TNF· and IL-1ß 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≤0.001). Comparative studies with endothelial cells isolated from human colorectal cancer and non-neoplastic colon will be useful for understanding the progressive behavior of colorectal cancer. The different secretion profiles of sVEGFR-1 and -2 between HCTEC and HCMEC underline the importance of using a functionally adequate and relevant tumor-derived microvasculature for in vitro studies of tumor progression. Since sVEGFR-1 can act as a natural endogenous VEGF-inhibitor, the homogeneously low sVEGFR-1 levels under normoxia and hypoxia in HCTEC could be a marker for a 'pro-angiogenetic disposition' of the tumorderived endothelium. The reduced sVEGFR-2 level profiles in hypoxic HCMEC and HCTEC provide evidence for a novel microvascular endothelium-specific biomarker in hypoxia-response processes.

Tumor Endothelial Cells (TECs) as Potential Immune Directors of the Tumor Microenvironment – New Findings and Future Perspectives

“…Importantly, a hypoxic TME also impacts the regulation of angiogenesis. In this regard it has been shown that angiogenetic feedback loops by soluble VEGFR are compromised in colon cancer-derived TECs, indicating a pro-angiogenetic disposition of TECs (Jayasinghe et al, 2009). Lastly, a hypoxic micro-milieu affects protein glycosylation and may therefore impact immune cell migration to the tumor and signaling cascades within the TME (Chandler et al, 2019).…”

Fetal death: A condition with a dissociation in the concentrations of soluble vascular endothelial growth factor receptor-2 between the maternal and fetal compartments

“…This mechanism of protein ectodomain shedding by transmembrane proteases has recently emerged as a key posttranslational regulator of several growth factor receptors involved in angiogenesis [69–71]. Although sVEGFR-2 concentrations in cell lysates of human colonic microvascular endothelial cells are reduced in response to hypoxia [72,73], it is unlikely that the decreased plasma sVEGFR-2 concentrations in women with fetal death results from a response of vascular endothelial cells against local hypoxic insults.…”

Intratumoral TLR-4 Agonist Injection Is Critical for Modulation of Tumor Microenvironment and Tumor Rejection

“…Although we know the tumor cells we used express TLR4, we believe that in our system LPS is probably acting on immune cells, particularly on the DCs that infiltrate the tumor site, rather than on the tumor cells, because when LPS was given along with tumor cells, even though the B16F10 cells were in direct contact with LPS, the tumor still grew, indicating absence of direct toxic effects of LPS over the melanoma cells. A study that observed toxic effects of LPS over tumor cells attributed such effects to indirect toxicity over endothelial cells [41,42] rather to direct effects over the tumor cells.…”