Irradiation induces Up‐regulation of E9 protein (CD105) in human vascular endothelial cells

Abstract

The use of MAb E-9 raised against tissue-cultured endothelial cells (EC) has shown marked heterogeneity in vascular EC lining the blood vessels of normal and tumour tissues. MAb E-9 is human EC-specific and the protein recognized by it is a homodimer with a molecular mass of 97 kDa. The E-9 protein is resistant to treatment by 3 mM sodium periodate, but is sensitive to 10% trichloroacetic acid and 70% ethanol. E-9 protein has been assigned to a new cluster, CD105, and mapped to human chromosome 9q3. It has approximately 70% homology with type-III cell-surface receptor for transforming growth factor beta (TGF-beta). Recently CD105 has been reported to be the gene in patients with hereditary haemorrhagic telangiectasia. We have examined the effects of radiation on its expression in normal human umbilical-vein endothelial cells (HUVEC) and brain-tumour-derived endothelial cells (BTEC). Irradiation induced dose- and time-dependent up-regulation in the expression of the E-9 protein on the plasma membranes of EC, and also resulted in greater increase in the expression of the E-9 protein in semi-confluent (proliferating) as compared with confluent (non-proliferating) EC. It may well be that, following radiotherapy in cancer patients, E-9 protein is also up-regulated. The presence of increased amounts of E-9 protein in EC makes it an attractive target in the control of angiogenesis, especially after radiotherapy in cancer patients. The time scale involved in the up-regulation of E-9 protein following irradiation has led us to suggest that it may be a secondary event, the primary being the production and release of mitogenic factors (such as basic fibroblast growth factor) from irradiated EC.

In vitro assessment of bone marrow endothelial colonies (CFU-En) in non-Hodgkin's lymphoma patients undergoing peripheral blood stem cell transplantation

“…29,30 Furthermore, it must be said that some of these patients received radiotherapy, which can induce an upregulation of the E-9 protein (CD105) in human vascular endothelial cells. 31 Human bone marrow endothelial cells present in remission phase may also have the effect of protecting and maintaining the hematopoietic stem cell compartment from extensive differentiation through the production of differentiation inhibitors such as thymosin b4 and AcSDKP 32,33 that has been shown to induce angiogenesis in vitro and in vivo. 34 On the other hand, other reports have shown that the existence of circulating BM endothelial progenitor cells can restore blood flow to ischemic animals leading to the concept of 'therapeutic adult vasculogenesis' that may explain the recruitment of ECs to various target organs such as BM, where they might contribute to the in situ neo-vascularization.…”

Irradiation Induces Upregulation of CD31 in Human Endothelial Cells

“…33,38 Differences in the level of cell proliferation demonstrated by control cultures at the different seeding densities presumably reflected differences in contact inhibition. The reduced rate of cell depletion at the lower plating density could be due to increased proliferation at this level of confluence.…”

“…One of the morphologic changes that endothelial cells are reported to undergo in vivo, after irradiation, is swelling. 3,33 It is conceivable that the upregulated levels of CD31 on irradiated HUVECs may have been due to an increase in cell surface area. However, the data from the flow cytometric analysis of forward scatter, which is proportional to cell size, showed that the increase in CD31 far exceeded any alterations in size.…”

“…33 HUVECs from 3 to 4 cords were pooled and used at passage 4 when Ͼ99% of cells were positive for the endothelial-specific marker, von Willebrand factor, as determined by an indirect immunofluorescence staining procedure.…”

CD105 prevents apoptosis in hypoxic endothelial cells

“…As an internal loading control, the blot was stripped and reprobed using a goat anti-α-actin (Sigma) or mouse anti-CD31 antibody (DAKO) and detected by HRP-conjugated secondary antibodies. CD105 shed into the medium was detected by a chemiluminescent ELISA system as described previously (Wang et al, 1995;Li et al, 2000c).…”