The pro-inflammatory chemokine, monocyte chemoattractant protein-1 (MCP-1), plays a fundamental role in monocyte recruitment and has been implicated as a contributing factor to atherosclerosis. The predominant cell types within the vessel wall-endothelial cells, smooth muscle cells, and macrophages-all contribute to overexpression of MCP-1 in atherosclerotic tissue. In this report we assess the role of MCP-1 expression by leukocytes on lesion progression in a murine model susceptible to atherosclerosis. Bone marrow cells from mice overexpressing a murine MCP-1 transgene on a background of apoE-deficiency or from control mice were transplanted into irradiated apoE-knockout mice. After repopulation of apoE-knockout mice with bone marrow containing the MCP-1 transgene, macrophages expressing the MCP-1 transgene were found in several tissues, including the aorta. Qualitative assessment of atherosclerosis in these mice revealed increased lipid staining, a 3-fold (P0.001) increase in the amount of oxidized lipid, and increased immunostaining for macrophage cell surface markers with anti-F4/80 and anti-CD11b antibodies. There were no differences in plasma lipids, plasma lipoprotein profiles, or body weight between the 2 groups. These results provide the first direct evidence that MCP-1 expression by leukocytes, predominately macrophages, increases the progression of atherosclerosis by increasing both macrophage numbers and oxidized lipid accumulation. (Arterioscler Thromb Vasc Biol. 1999;19:1518-1525.) Key Words: bone marrow CD11b F4/80 oxidized lipid chemokines M onocyte/macrophage cells have an essential role in orchestrating the complex sequence of events involved in the initiation and progression of atherosclerosis. 1 Cells of monocytic origin are present in the developing foam cell lesion, where they engulf lipid and form most of the volume of the fatty streak. 2,3 This early stage of atherosclerosis is characterized by the focal attachment of monocytes to the endothelium and their subsequent transendothelial migration into the vessel wall. 1,4 Once in the tissue, macrophages potentiate the inflammatory response by producing various inflammatory mediators, such as reactive oxygen species and growth factors, including basic fibroblast growth factor, platelet-derived growth factor, transforming growth factor-beta, and other proinflammatory cytokines and chemo-kines. 2,5 Monocytes themselves promote additional monocyte adherence and emigration from the vascular space into sites of inflammation. 6,7 The generation of a murine model in which the apoE gene has been disrupted has provided an important small animal model for the study of atherosclerosis. 8,9 ApoE-deficient mice (apoE-KO) exhibit hypercholesterolemia and develop complex atheromatous lesions similar to those seen in humans. 10,11 These mice develop a full range of lesions, from fatty streaks to raised fibrous plaques, making this model suitable for investigating the pathogenesis of atherosclerosis. To demonstrate the involvement of the macrophage in this pr...

GM2, GD2, and GD3 gangliosides are expressed on the surface of human melanoma cells and represent potential targets for immunological control of melanoma growth by monoclonal antibodies and active immunization. The immunogenicity of GM2 was investigated by analyzing the humoral immune response of melanoma patients to vaccination with cell lines selected for high GM2 expression and with vaccines containing purified GM2. The whole-cell vaccine and vaccines containing purified GM2 and bacillus CalmetteGuerin (BCG) elicited GM2 antibody in a high proportion of patients, particularly in GM2/BCG-vaccinated patients pretreated with cyclophosphamide and given a GM2/BCG booster immunization. Vaccines containing purified GM2 and Salmonella minnesota R595 as the adjuvant were also effective, but only in patients pretreated with cyclophosphamide. GM2 antibodies in vaccinated patients were of the IgM class and were cytotoxic for GM2-positive targets in the presence of human complement.Gangliosides are prominent cell-surface constituents of melanoma and other tumors of neuroectodermal origin. Three gangliosides, the monosialoganglioside GM2 and the disialogangliosides GD2 and GD3, are of particular interest to tumor immunologists because of their potential as targets for passive immunization with monoclonal antibodies (mAbs) and for active immunization with cancer vaccines. Despite the presence of GM2, GD2, and GD3 in normal brain and other tissues (1), these gangliosides are immunogenic in mice and humans; mouse mAbs have been generated against GM2 (2), GD2 (3, 4), and GD3 (5-8), and human sera and human mAbs with reactivity for GM2 (9-12), GD2 (11,13,14), and GD3 (15) have been identified.Over the past decade we have immunized sequential groups of melanoma patients with a variety of melanoma cell vaccines (16)(17)(18)(19)(20). These vaccine trials were based on our seriological analysis of the humoral immune response of melanoma patients to cell-surface antigens of autologous and allogeneic melanomas (21), and each vaccine was constructed to contain melanoma surface antigens known to be immunogenic in humans. Although vaccinated patients readily produced antibody to HLA-related alloantigens and heterologous serum components in the vaccine, only rarely was antibody elicited to more restricted melanoma antigens, such as class 1 (unique), or GD2 or other class 2 (shared) melanoma antigens. In parallel vaccine studies in the mouse, we have identified immunizing procedures that facilitate the serological response to tumor antigens (22-24). In the case of GM2, immunization with GM2-expressing tumor cells or purified GM2 only infrequently induced GM2 antibody in mice, whereas vaccines containing GM2 with adjuvants such as bacillus Calmette-Gudrin (BCG) or Salmonella minnesota R595 were far more effective (24).In the present study, we have examined the immunogenicity of GM2-containing vaccines in stage III melanoma patients. Two types of vaccines were used: a whole-cell vaccine containing high levels of GM2 and vaccines con...

Anaplastic lymphoma kinase (ALK) is one of the few remaining "orphan" receptor tyrosine kinases (RTKs) in which the ligands are unknown. Ligand-mediated activation of RTKs is important throughout development. ALK is particularly relevant to the development of the nervous system. Increased activation of RTKs by mutation, genetic amplification, or signals from the stroma contributes to disease progression and acquired drug resistance in cancer. Aberrant activation of ALK occurs in subsets of lung adenocarcinoma, neuroblastoma, and other cancers. We found that heparin is a ligand that binds specifically to the ALK extracellular domain. Whereas heparins with short chain lengths bound to ALK in a monovalent manner and did not activate the receptor, longer heparin chains induced ALK dimerization and activation in cultured neuroblastoma cells. Heparin lacking N- and O-linked sulfate groups or other glycosaminoglycans with sulfation patterns different than heparin failed to activate ALK. Moreover, antibodies that bound to the extracellular domain of ALK interfered with heparin binding and prevented heparin-mediated activation of ALK. Thus, heparin and perhaps related glycosaminoglycans function as ligands for ALK, revealing a potential mechanism for the regulation of ALK activity in vivo and suggesting an approach for developing ALK-targeted therapies for cancer.