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Biomedical subjects

A W Griffioen

Publications and source records attributed to A W Griffioen.

At least 37 records · Page 2Linked to original sources
PubMed1998

The angiogenic factor bFGF impairs leukocyte adhesion and rolling under flow conditions.

Recirculation of leukocytes is mediated by the intricately regulated expression of adhesion molecules on both the vessel wall and leukocyte membranes. In the present paper it is demonstrated that tumor angiogenesis factors impair leukocyte rolling and adhesion under flow conditions. Three lines of evidence presented in this paper support this finding; (i) treatment of cultured endothelial cells (EC) with the angiogenic factor basic fibroblast growth factor (bFGF) results in decreased ICAM-1 expression and decreased numbers of adhering leukocytes under flow conditions. (ii) flow induced upregulation of endothelial ICAM-1 in the presence of bFGF does not yield ICAM-1 levels higher than on resting EC. (iii) bFGF decreases the TNFalpha mediated induction of E-selectin and ICAM-1 expression, resulting in decreased rolling and firm adhesion of leukocytes on the endothelial surface. For ICAM-1 it is demonstrated that bFGF inhibits TNFalpha induced levels of mRNA, and that this effects is transcriptionally regulated. These findings support our earlier described hypothesis that angiogenic factors are involved in the tumor derived escape mechanism from immune surveillance, since we demonstrate here that these mechanisms are operative under physiologic flow conditions.

Journal Article↗
PubMed1998

Angiogenesis modulates the tumour immune response.

Outgrowth of solid tumors and metastases is dependent on the process of angiogenesis. Tumors escape from the formation of an effective infiltrate by downregulation of endothelial adhesion molecules. This downregulation of adhesion receptors is governed by the exposure to angiogenic factors. In recent years proof for this has been provided by demonstrating that freshly isolated tumor endothelial cells exhibit a decreased expression of ICAM-1 and -2 as compared to endothelial cells in normal tissue. In addition, adhesion molecules are downregulated on normal tissue endothelial cells when cultured with angiogenesis stimulators such as basic fibroblast growth factor and vascular endothelial cell growth factor, while under these conditions endothelial cells become less responsive to cytokines such as tumor necrosis factor-alpha with respect to the upregulation of endothelial adhesion molecules. Very recently it has been demonstrated that this harmful endothelial cell anergy can be counteracted by inhibitors of angiogenesis.

Animals↗
PubMed1997

Endothelial CD34 is suppressed in human malignancies: role of angiogenic factors.

We report the suppressed vascular CD34 expression in renal cell carcinoma. This was found by quantitatively analyzing CD34 expression on normal and tumor derived EC by flow cytometry. In vitro studies revealed that culture of umbilical cord or dermis derived microvascular EC with angiogenic factors such as basic fibroblast growth factor (bFGF) and vascular endothelial cell growth factor induced downregulation of CD34. This angiogenesis-induced downregulated expression of CD34 adhesion molecule may contribute to the tumor mediated escape mechanism from immune surveillance. It is concluded that there are quantitative differences in expression of endothelial CD34 in different compartments of the vasculature, that angiogenic factors affect this expression and that subpopulations of EC exist with differences in EAM expression.

Antibodies↗
PubMed1997

CD44 is involved in tumor angiogenesis; an activation antigen on human endothelial cells.

CD44 is described to be an activation molecule in a number of different cell types. We investigated the role of CD44 on human endothelial cells (EC) and in tumor angiogenesis. Using flow cytometry we showed that EC from the vasculature of human solid tumors display an enhanced expression of CD44 as compared to EC from normal tissue. This finding was confirmed by immunohistochemical studies on frozen tissue sections. Because tumors are dependent on angiogenesis, the role of angiogenic stimuli in the enhanced CD44 expression was investigated. We found that basic fibroblast growth factor (bFGF) and vascular endothelial growth factor were able to efficiently upregulate CD44 expression on cultured human EC. The upregulation reached maximal levels after treatment for 3 days with 10 ng/mL bFGF. The physiological impact of this upregulation was shown by the enhanced binding of EC to hyaluronate after pretreatment with bFGF. In a next set of studies that were designed to unravel the regulation of CD44 expression on EC we concluded that CD44 is an activation antigen on human EC since (1) human umbilical vein derived endothelial cells, which in vivo do not express CD44, begin to express CD44 when plated and cultured, (2) CD44 expression is enhanced after subculture of confluent cultures, (3) CD44 is predominantly expressed on the BrdU incorporating subset of cultured EC. The specific expression of CD44 on activated and tumor EC prompted us to study the usefulness of CD44 as an endothelial target for therapy with immunotoxins. In vitro experiments showed that EC are efficiently killed after targeting immunotoxin to CD44.

Antibodies, Monoclonal↗
PubMed1996

Tumor angiogenesis is accompanied by a decreased inflammatory response of tumor-associated endothelium.

We previously showed that endothelial cells (EC) from the vasculature of human solid tumors have a decreased expression of intercellular adhesion molecule-1 (ICAM-1) and ICAM-2 as compared with normal tissue EC. This effect is explained by EC exposure to angiogenic factors. It is known that upregulation of endothelial adhesion molecules (EAM) is a sign of EC activation in inflammatory responses. We therefore tested the effect of angiogenic factors on upregulation of EAM on tumor EC and human umbilical vein EC (HUVEC) by proinflammatory cytokines. Incubation of tumor-derived EC in tumor necrosis factor alpha (TNF alpha) did result in expression levels of only 20% of the level of similarly treated normal tissue-derived EC. Pretreatment of HUVEC with 10 ng/ml basic fibroblast growth factor (bFGF) for 3 days, before TNF alpha- or interleukin-1 alpha (IL-1 alpha) stimulation, resulted in ICAM-1 levels of only 30% to 60% of cells without pretreatment. Also, the induction of vascular EC adhesion molecule-1 (VCAM-1) and E-selectin by TNF alpha was significantly inhibited by prior exposure to bFGF. Vascular endothelial growth factor had similar but less prominent effects. The effect of transforming growth factor-beta and IL-8 was studied as well. The functional relevance of the finding of a decreased EC inflammatory response was confirmed by adhesion assays. Our results show that tumor angiogenesis induces EC anergy. This may serve as a tumor-protecting mechanism by impairing the development of an efficient leukocyte infiltrate in tumors.

Cytokines↗
PubMed1996

Endothelial intercellular adhesion molecule-1 expression is suppressed in human malignancies: the role of angiogenic factors.

Intercellular adhesion molecule 1 (ICAM-1) is involved in the recirculation of blood leukocytes and, presumably, in the infiltration of cytolytic effector leukocytes into tumors. The present report describes a down-regulated expression of vascular ICAM-1 on tumor-infiltrating endothelial cells (EC) in renal cell carcinoma. This finding was obtained by flow cytometric analysis of tumor EC compared to EC obtained from healthy tissue. Since growth of solid tumors is dependent on the formation of new blood vessels (angiogenesis), we hypothesized that angiogenic factors are responsible for the down-regulation of ICAM-1. This hypothesis was investigated in vitro using human umbilical vein- and dermis-derived EC. Using flow cytometry, we found a biphasic regulation of ICAM-1 during stimulation of cultured EC with the angiogenic agent basic fibroblast growth factor (bFGF). Although 16-24 h after activation a marked up-regulation of ICAM-1 was observed, expression was significantly decreased after 48h. The longevity of this down-regulation was at least 7 days. Northern blot analysis revealed down-regulation of the steady-state mRNA level of the gene. ICAM-2 showed similar results of intial up- and later down-regulation. Functional relevance for the changes in ICAM-1 expression was demonstrated by a corresponding biphasic regulation of EC-leukocyte adhesion after EC activation by bFGF. The described effects are specific for bFGF since other angiogenic factors (such as vascular endothelial growth factor, transforming growth factor beta, and interleukin 8) did not affect adhesion molecule expression. Subsequent experiments showed that angiogenic factors decrease the sensitivity of EC to activation with tumor necrosis factor-alpha in regard to adhesion molecule expression. The present results reveal a tumor-derived escape mechanism from cytolytic effector leukocytes by down-regulation of vascular adhesion molecules in vivo and in vitro and decreased responsiveness to proinflammatory cytokines.

Carcinoma, Renal Cell↗
PubMed1996

Signaling through CD44 is mediated by tyrosine kinases. Association with p56lck in T lymphocytes.

Evidence from a large body of studies indicates that CD44 is involved in a number of important biological processes, including lymphocyte activation and homing, hematopoiesis, and tumor progression and metastasis. A proper understanding of the role of CD44 in these processes has been severely hampered by a lack of insight into the mode in which CD44 communicates with intracellular signal transduction pathways. In this report, we have addressed this aspect of CD44 functioning by studying CD44 signaling in T lymphocytes. We show that ligation of CD44 by monoclonal antibodies (mAbs) transduces signals to T cells which lead to tyrosine phosphorylation of ZAP-70 and other intracellular proteins. In vitro kinase assays demonstrate that cross-linking of CD44 induces an increase in the intrinsic activity of p56lck. Furthermore, immunoprecipitations show that CD44 is physically associated with p56lck. Our findings suggest that tyrosine kinases, particularly p56lck, play a central role in CD44 mediated signaling.

Animals↗
PubMed1994

Expression of CD44 splice variants during lymphocyte activation and tumor progression.

Recently, splice variants of CD44 have been described that confer metastatic potential to non-metastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies against variant CD44 (CD44v) sequences, we have examined the expression of variant CD44 glycoproteins on human lymphoid cells and tissues and in colorectal neoplasia. Lymphohematopoietic cells express low levels of CD44v glycoproteins. During the process of lymphocyte activation in vitro and in vivo, expression of CD44v glycoproteins is transiently upregulated. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that confers metastatic capability. In human colorectal neoplasia we observed overexpression of CD44 splice variants in all invasive carcinomas. Already at early stages of colorectal tumor progression exon v5 epitopes were overexpressed. Tumor progression was strongly related to expression of CD44 isoforms containing exon v6 encoded domains. The findings establish CD44 variants as tumor progression markers in colorectal cancer.

Alternative Splicing↗
PubMed1993

Changes in free cytoplasmic magnesium following activation of human lymphocytes.

Activation of lymphocytes with 10 microM ionomycin leads to a rapid increase in the concentration of free cytoplasmic calcium ([Ca2+]i) and, at a slower rate, also to an increase in the cytoplasmic free magnesium concentration ([Mg2+]i). The ionomycin-induced Mg(2+)-mobilization response is dependent on the influx of extracellular Ca2+. After receptor-mediated lymphocyte activation, induced by mitogens or anti-receptor antibodies, a Mg(2+)-mobilization response does occur in a small fraction of the cells. Simultaneous measurement of [Ca2+]i and [Mg2+]i in individual cells showed that the receptor-triggered Mg(2+)-mobilization response is restricted to cells that have a high [Ca2+]i. It can therefore be concluded that a high [Ca2+]i induces the release into the cytoplasm of Mg2+ from intracellular stores.

Burkitt Lymphoma↗
PubMed1993

Expression and functional characteristics of the complement receptor type 2 on adult and neonatal B lymphocytes.

In vivo antibody synthesis against thymus-independent type 2 (TI-2) antigens such as type-specific polysaccharides of pneumococci is low or absent during the first 2 years of life. Recently, we described a role for CR2 in the in vitro antibody response of B cells of adults to the TI-2 antigen type 4 pneumococcal polysaccharide. In the present study a decreased expression of CR2 is described on cord blood B cells using HB5 and OKB7 anti-CR2 MAb. Crosslinking of HB5 anti-CR2 antibodies on the B cell membrane leads to increases in intracellular calcium ([Ca2+]i) in both adult and neonatal B cells. In adult B cells, a synergism between CR2 and sIgM could be demonstrated on the level of calcium mobilization by occupying CR2 and crosslinking of sIgM with substimulatory concentrations of anti-IgM antibodies. This synergistic action between CR2 and sIgM could not be demonstrated in neonatal B cells. In addition, it is demonstrated that HB5 MAb cannot induce B cell differentiation in neonatal B cells, while adult B cells can be induced to differentiate into Ig-producing cells by this MAb.

Adult↗
PubMed1993

Intracellular magnesium movements and lymphocyte activation.

Activation of lymphocytes through ligation of the antigen receptor complex initiates activation of phospholipase C-gamma (PLC). Activated PLC hydrolyses phosphatidylinositol-4,5-bisphosphate into diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (InsP3). InsP3 mediates the release of Ca2+ from intracellular stores into the cytoplasm, while InsP4 and InsP3 mobilize extracellular Ca2+. Both processes contribute to the temporary increase in [Ca2+]i that is observed after lymphocyte activation. Because of the availability of Mg(2+)-sensitive and specific fluorochromes like Mag-indo-1 it is now possible to monitor potential changes in [Mg2+]i. In lymphocytes that have responded to receptor activation with high [Ca2+]i, an increase in [Mg2+]i can be found. The [Mg2+]i is in the range that enables it to modulate the activity of a number of cellular enzymes, including key enzymes in the PLC transmembrane signalling pathway. It can be speculated that a differential Mg2+ mobilization response will have consequences for the ultimate cellular response to receptor activation.

Calcium↗
PubMed1992

Heterodimeric complex formation with CD8 and TCR by bispecific antibody sustains paracrine IL-2-dependent growth of CD3+ CD8+ T cells.

During physiologic activation of mature CD8+ T cells, TCR and CD8 bind to the same Ag-complexed MHC class I molecule. Thereby, close proximity is induced between CD8 and the TCR/CD3 complex. During this engagement, CD8 may deliver TCR-independent signals via its associated protein tyrosine kinase, p56lck. We studied the potential biologic effects of close association between CD8 and TCR/CD3 complexes by using a bispecific antibody (bsAb) directed against both TCR and CD8 molecules. This hybrid hybridoma (quadroma)-produced bsAb binds as a monomeric molecule to CD3+ CD8+ but not CD3+ CD4+ T cells. The bsAb proved capable of inducing the cytotoxic effector function of cloned CD3+ CD8+ T cells but not of CD3+ CD4+ T cells. When the bsAb was presented to resting T cells by monocytes, proliferation of the CD3+ CD4+ but not the CD3+ CD8+ subset of T lymphocytes was induced. Parental anti-TCR antibody induced vigorous growth of cells of both subsets. Essentially identical results were obtained when bsAb was presented in an immobilized fashion. The unresponsiveness of the CD3+ CD8+ T cells with respect to mitogenesis could be restored by exogenous rIL-2. The data suggest that bsAb-induced activation differs from activation by monospecific anti-TCR antibody. The former appears to more closely mimic physiologic Ag-induced signaling, because it leads to a similar paracrine IL-2-dependent growth pattern. The bsAb may, therefore, be instrumental in studying T cell signaling pathways, in particular the role of CD8-associated p56lck therein.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Role of CR2 in the human adult and neonatal in vitro antibody response to type 4 pneumococcal polysaccharide.

A number of studies have indicated that the complement receptor type 2 (CR2), which is the receptor for C3d, a degradation fragment of the complement component C3, regulates B lymphocyte activation and growth. Early reports have described that C3 regulates T cell-dependent (TD) antibody responses. The involvement of CR2 in the antibody response to T cell-independent type 2(TI-2) antigens was investigated because neonatal B cells, which are unresponsive to TI-2 antigens both in vivo and in vitro, express a significantly decreased level of CR2 as compared to B cells of adult donors. We utilized type 4 pneumococcal polysaccharide (PS4) as a model TI-2 antigen. In order to study the relationship between CR2 and the response to PS4, B cells were costimulated with PS4 and monoclonal antibodies (MAb) to CR2. HB5 and OKB7 anti-CR2 monoclonal antibodies enhanced the in vitro response of adult B cells to PS4, as measured in a PS4-specific spot-forming cell assay. Neonatal B cells could only be induced to respond to PS4 using high concentrations of OKB7 anti-CR2 MAb. The 8-mercaptoguanosine (8MGuo), an agent that can overcome the in vitro unresponsiveness to PS4 of neonatal B cells, increased CR2 expression on adult and neonatal B cells. Furthermore, 8MGuo synergizes strongly with anti-CR2 antibodies in augmenting the anti-PS4 antibody response. Data presented in this report provide evidence of CR2 involvement in the antibody response to PS4 and that the neonatal B cell unresponsiveness to TI-2 antigens may be due to the decreased expression of CR2.

Adult↗
PubMed1992

The amplifier role of T cells in the human in vitro B cell response to type 4 pneumococcal polysaccharide.

The human B cell response to T cell independent type 2 antigens is regulated by thymus-derived lymphocytes. We analyzed the role of T cells in the in vitro antibody response to type 4 pneumococcal polysaccharide (PS4). We here show that the amplifying effect of T cells, which has previously been shown to be radioresistant and confined to T cell preparations enriched for CD4+ cells, is MHC non-restricted as demonstrated in cultures carried out in the presence of allogeneic T cells. Also, T cell clones derived from non-related donors are able to enhance the B cell response to PS4. All TCR alpha beta +, CD 4+ T cell clones, but none of the TCR alpha beta +, CD 8+ T cell clones tested, enhanced the B cell response to PS4. Furthermore, 3 out of 6 TCR gamma delta+ T cell clones were capable of enhancing the anti-PS4 B cell response. Experiments using recombinant lymphokines and glutaraldehyde-fixed T cells indicated that both lymphokines and T-B cell interactions are required for an optimal antibody response to PS4.

Antibodies↗