ABSTRACT
Vascular endothelial cells contain unique storage organelles, designated Weibel-Palade bodies (WPBs), that deliver inflammatory and hemostatic mediators to the vascular lumen in response to agonists like thrombin and vasopressin. The main component of WPBs is von Willebrand factor (VWF), a multimeric glycoprotein crucial for platelet plug formation. In addition to VWF, several other components are known to be stored in WPBs, like osteoprotegerin, monocyte chemoattractant protein-1 and angiopoetin-2 (Ang-2). Here, we used an unbiased proteomics approach to identify additional residents of WPBs. Mass spectrometry analysis of purified WPBs revealed the presence of several known components such as VWF, Ang-2, and P-selectin. Thirty-five novel candidate WPB residents were identified that included insulin-like growth factor binding protein-7 (IGFBP7), which has been proposed to regulate angiogenesis. Immunocytochemistry revealed that IGFBP7 is a bona fide WPB component. Cotransfection studies showed that IGFBP7 trafficked to pseudo-WPB in HEK293 cells. Using a series of deletion variants of VWF, we showed that targeting of IGFBP7 to pseudo-WPBs was dependent on the carboxy-terminal D4-C1-C2-C3-CK domains of VWF. IGFBP7 remained attached to ultralarge VWF strings released upon exocytosis of WPBs under flow. The presence of IGFBP7 in WPBs highlights the role of this subcellular compartment in regulation of angiogenesis.
Subject(s)
Endothelial Cells/chemistry , Insulin-Like Growth Factor Binding Proteins/chemistry , Proteomics/methods , Weibel-Palade Bodies/chemistry , Endothelial Cells/physiology , Exocytosis , Genetic Vectors , HEK293 Cells , Human Umbilical Vein Endothelial Cells , Humans , Immunohistochemistry , Mass Spectrometry , Neovascularization, Physiologic , P-Selectin/chemistry , Protein Structure, Tertiary , Protein Transport , Transfection , Weibel-Palade Bodies/physiology , von Willebrand Factor/chemistryABSTRACT
PURPOSE: Chimeric antibody MOv18 (c-MOv18) mediates antibody-dependent cellular cytotoxicity (ADCC) in vitro. To study the toxicity of c-MOv18 and its immunological effects, five ovarian cancer patients received intravenous injections for 4 weeks. METHODS: ADCC activity of c-MOv18 was tested in a (51)Cr-release assay using IGROV1 and KB cells. Patients' peripheral blood mononuclear cells (PBMC) were phenotyped for CD3, CD4, CD8, and CD25 by FACS analysis and tested for T-cell proliferation in vitro in the presence of c-MOv18 with and without IL-2. RESULTS: Toxicity was mild and transient. No human anti-chimeric antibodies were found. Increased ADCC levels corresponding with a slight increase in CD4+ and CD8+ fractions were observed after the first injection, while the CD4/CD8 ratio and the levels of CD25 remained unchanged. c-MOv18 did not have a mitogenic effect on patients' PBMC and adding IL-2 did not change the degree of proliferation. In three patients stable disease was achieved for up to 4 months, 9 months and 14 months, respectively. CONCLUSION: Immunotherapy aiming at the patient's immunological capacity has minor effects in ovarian cancer patients that have been heavily pretreated with chemotherapy. Such strategies should be evaluated in patients who are more immunocompetent, i.e., before excessive chemotherapy and after achieving microscopic or small volume disease.
