Id1 suppresses anti-tumour immune responses and promotes tumour progression by impairing myeloid cell maturation.

A central mechanism of tumour progression and metastasis involves the generation of an immunosuppressive 'macroenvironment' mediated in part through tumour-secreted factors. Here we demonstrate that upregulation of the Inhibitor of Differentiation 1 (Id1), in response to tumour-derived factors, such as TGFß, is responsible for the switch from dendritic cell (DC) differentiation to myeloid-derived suppressor cell expansion during tumour progression. Genetic inactivation of Id1 largely corrects the myeloid imbalance, whereas Id1 overexpression in the absence of tumour-derived factors re-creates it. Id1 overexpression leads to systemic immunosuppression by downregulation of key molecules involved in DC differentiation and suppression of CD8 T-cell proliferation, thus promoting primary tumour growth and metastatic progression. Furthermore, advanced melanoma patients have increased plasma TGFß levels and express higher levels of ID1 in myeloid peripheral blood cells. This study reveals a critical role for Id1 in suppressing the anti-tumour immune response during tumour progression and metastasis.

Chapter 11. The role of bone marrow-derived cells in tumor angiogenesis and metastatic progression.

Tumor angiogenesis is orchestrated by a complex set of secreted factors and collaboration between many different cell types. This chapter discusses the role of tumor-secreted angiogenic factors that are responsible for the recruitment of bone marrow-derived cells (BMDCs) at tumor sites and their role in tumor angiogenesis and progression.

CCR2-mediated antiinflammatory effects of endothelial tetrahydrobiopterin inhibit vascular injury-induced accelerated atherosclerosis.

BACKGROUND: Vascular injury results in loss of endothelial nitric oxide (NO), production of reactive oxygen species (ROS), and the initiation of an inflammatory response. Both NO and ROS modulate inflammation through redox-sensitive pathways. Tetrahydrobiopterin (BH4) is an essential cofactor for endothelial nitric oxide synthase (eNOS) that regulates enzymatic synthesis of either nitric oxide or ROS. We hypothesized that endothelial BH4 is an important regulator of inflammation and vascular remodeling. METHODS AND RESULTS: Endothelium-targeted overexpression of GTP cyclohydrolase 1 (GCH), the rate limiting enzyme in BH4 synthesis, increased levels of tetrahydrobiopterin (BH4), reduced endothelial superoxide, improved eNOS coupling, and reduced vein graft atherosclerosis in transgenic GCH/ApoE-KO mice compared to ApoE-KO controls. Immunohistochemistry using anti-MAC-3 and MAC-1 antibody staining revealed a marked reduction in vein graft macrophage content, as did RT-PCR expression of macrophage marker CD68 mRNA levels in GCH/ApoE-KO mice. When we investigated the potential mediators of this reduction, we discovered that mRNA and protein levels of MCP-1 (CCL2) but not RANTES (CCL5) were significantly reduced in GCH/ApoE-KO aortic tissue. Consistent with this finding we found a decrease in CCR2-mediated, but not CCR5-mediated, chemotaxis in vascular tissue and plasma samples from GCH/ApoE-KO animals. CONCLUSIONS: Increased endothelial BH4 reduces vein graft neointimal hyperplasia and atherosclerosis through a reduction in vascular inflammation. These findings highlight the importance of MCP-1/CCR2 signaling in the response to vascular injury and identify novel pathways linking endothelial BH4 to inflammation and vascular remodeling.

Galectin-3 is an amplifier of inflammation in atherosclerotic plaque progression through macrophage activation and monocyte chemoattraction.

OBJECTIVE: Galectin-3 (Gal-3) is a 26-kDa lectin known to regulate many aspects of inflammatory cell behavior. We assessed the hypothesis that increased levels of Gal-3 contribute to atherosclerotic plaque progression by enhancing monocyte chemoattraction through macrophage activation. METHODS AND RESULTS: Gal-3 was found to be upregulated in unstable plaque regions of carotid endarterectomy (CEA) specimens compared with stable regions from the same patient (3.2-fold, P<0.05) at the mRNA (n=12) and (2.3-fold, P<0.01) at the protein level (n=9). Analysis of aortic tissue from ApoE-/- mice on a high fat diet (n=14) and wild-type controls (n=9) showed that Gal-3 mRNA and protein levels are elevated by 16.3-fold (P<0.001) and 12.2-fold (P<0.01) and that Gal-3 staining colocalizes with macrophages. In vitro, conditioned media from Gal-3-treated human macrophages induced an up to 6-fold increase in human monocyte chemotaxis (P<0.01, ANOVA), an effect that was reduced by 66 and 60% by Pertussis Toxin (PTX) and the Vaccinia virus protein 35K, respectively. Microarray analysis of human macrophages and subsequent qPCR validation confirmed the upregulation of CC chemokines in response to Gal-3 treatment. CONCLUSIONS: Our data suggest that Gal-3 is both a marker of atherosclerotic plaque progression and a central contributor to the pathology by amplification of key proinflammatory molecules.

Novel candidate genes in unstable areas of human atherosclerotic plaques.

OBJECTIVE: Comparison of gene expression in stable versus unstable atherosclerotic plaque may be confounded by interpatient variability. The aim of this study was to identify differences in gene expression between stable and unstable segments of plaque obtained from the same patient. METHODS AND RESULTS: Human carotid endarterectomy specimens were segmented and macroscopically classified using a morphological classification system. Two analytical methods, an intraplaque and an interplaque analysis, revealed 170 and 1916 differentially expressed genes, respectively using Affymetrix gene chip analysis. A total of 115 genes were identified from both analyses. The differential expression of 27 genes was also confirmed using quantitative-polymerase chain reaction on a larger panel of samples. Eighteen of these genes have not been associated previously with plaque instability, including the metalloproteinase, ADAMDEC1 (approximately 37-fold), retinoic acid receptor responder-1 (approximately 5-fold), and cysteine protease legumain (approximately 3-fold). Matrix metalloproteinase-9 (MMP-9), cathepsin B, and a novel gene, legumain, a potential activator of MMPs and cathepsins, were also confirmed at the protein level. CONCLUSIONS: The differential expression of 18 genes not previously associated with plaque rupture has been confirmed in stable and unstable regions of the same atherosclerotic plaque. These genes may represent novel targets for the treatment of unstable plaque or useful diagnostic markers of plaque instability.

A first-generation linkage disequilibrium map of human chromosome 22.

DNA sequence variants in specific genes or regions of the human genome are responsible for a variety of phenotypes such as disease risk or variable drug response. These variants can be investigated directly, or through their non-random associations with neighbouring markers (called linkage disequilibrium (LD)). Here we report measurement of LD along the complete sequence of human chromosome 22. Duplicate genotyping and analysis of 1,504 markers in Centre d'Etude du Polymorphisme Humain (CEPH) reference families at a median spacing of 15 kilobases (kb) reveals a highly variable pattern of LD along the chromosome, in which extensive regions of nearly complete LD up to 804 kb in length are interspersed with regions of little or no detectable LD. The LD patterns are replicated in a panel of unrelated UK Caucasians. There is a strong correlation between high LD and low recombination frequency in the extant genetic map, suggesting that historical and contemporary recombination rates are similar. This study demonstrates the feasibility of developing genome-wide maps of LD.