Recently , monoclonal antibodies against the human vascular endothelial growth factor receptor VEGFR-3 were shown to provide a specific antigenic marker for lymphatic endothelium in various normal tissues. In this study we have investigated the expression of VEGFR-3 and its ligand VEGF-C in normal breast tissue and in breast tumors by immunohistochemistry. VEGFR-3 was weakly expressed in capillaries of normal breast tissue and in fibroadenomas. In intraductal breast carcinomas , VEGFR-3 was prominent in the "necklace" vessels adjacent to the basal lamina of the tumor-filled ducts. VEGF receptor 1 and 2 as well as blood vessel endothelial and basal lamina markers were colocalized with VEGFR-3 in many of these vessels. Antibodies against smooth muscle ␣-actin gave a weak staining of the necklace vessels , suggesting that they were incompletely covered by pericytes/smooth muscle cells. A highly elevated number of VEGFR-3 positive vessels was found in invasive breast cancer in comparison with histologically normal breast tissue (P < 0.0001 , the Mann-Whitney test). VEGF-C was located in the cytoplasm of intraductal and invasive cancer cells. The results demonstrate that the expression of VEGFR-3 becomes up-regulated in the endothelium of angiogenic blood vessels in breast cancer. The results also suggest that VEGF-C secreted by the intraductal carcinoma cells acts predominantly as an angiogenic growth factor for blood vessels , although this paracrine signaling network between the cancer cells and the endothelium may also be involved in modifying the permeabilities of both blood and lymphatic vessels and metastasis formation. (Am J Pathol 1999, 154:1381-1390)

Susceptibility to asthma depends on variation at an unknown number of genetic loci. To identify susceptibility genes on chromosome 7p, we adopted a hierarchical genotyping design, leading to the identification of a 133-kilobase risk-conferring segment containing two genes. One of these coded for an orphan G protein-coupled receptor named GPRA (G protein-coupled receptor for asthma susceptibility), which showed distinct distribution of protein isoforms between bronchial biopsies from healthy and asthmatic individuals. In three cohorts from Finland and Canada, single nucleotide polymorphism-tagged haplotypes associated with high serum immunoglobulin E or asthma. The murine ortholog of GPRA was up-regulated in a mouse model of ovalbumin-induced inflammation. Together, these data implicate GPRA in the pathogenesis of atopy and asthma.

Two N-terminal ends of human type XVIII collagen chains have recently been identified. The two chains have different signal peptides and variant N-terminal noncollagenous NC1 domains of 493 (NC1-493) and 303 (NC1-303) amino acid residues , respectively, but share 301 residues of their NC1 domains as well as the collagenous and C-terminal noncollagenous portions of the molecule. Antibodies were produced against the NC1 region common to both human ␣1(XVIII) chain variants and against NC1 sequences specific to the long variant and were used in combination with in situ hybridization to localize this collagen in a number of human tissues. They were also used for Western blotting , which resulted in detection of overlapping high-molecular weight bands above the 200-kd standard in a kidney extract. Heparin lyase II and heparin lyase III digestions of kidney and placenta extracts indicated that at least in these tissues, type XVIII collagen contains heparin sulfate glycosaminoglycan side chains. Type XVIII collagen was found to be a ubiquitous basement membrane component , occurring prominently at vascular and epithelial basement membranes throughout the body. Comparison of the expression of the NC1-493 and NC1-303 variants revealed marked differences. The short variant was found in most conventional basement membranes , including blood vessels and the various epithelial structures , and around muscular structures. The long variant was expressed very strongly in liver , where it was virtually the only variant in the liver sinusoids , and it occurred only in minor amounts elsewhere. Thus , the 192 N-terminal residues specific to the long variant apparently confer some functional property needed above all in the liver sinusoids , but also at certain other locations. (Am J Pathol 1998, 153:611-626) Type XVIII collagen is an extracellular matrix protein recently identified by cDNA cloning.1-4 Elucidation of the complete mouse chain revealed it to be homologous with the previously identified type XV collagen, 5-7 and it has been suggested that type XV and XVIII collagens together form a subgroup of MULTIPLEXINs (multiple triple-helix domains with interruptions) within the collagen family.2 The mouse type XVIII collagen differs strikingly from type XV by the presence of variant polypeptide forms characterized by three N-terminal noncollagenous domains of differing lengths. 8,9 Interestingly, the longest ␣1(XVIII) chain form has a motif of 10 cysteine residues homologous to the extracellular part of the frizzled receptors involved in the Wingless signaling pathway in Drosophila. 10We have recently reported also the full-length human type XVIII collagen cDNAs that encode 1516-or 1336-amino acid residue ␣1(XVIII) chains. 11 The two chains have different signal peptides and variant N-terminal noncollagenous NC1 domains of 493 (NC1-493) and 303 (NC1-303) amino acid residues, respectively, but share the last 301 residues of their NC1 domains, a 688-residue collagenous sequence (COL1 to COL10) with nine interruptions (NC2 to NC10), ...

Endostatin, a fragment of collagen XVIII, is a potent antagonist of angiogenesis and inhibitor of tumor growth in mouse models. At present, the mechanism of action of endostatin is unknown. We show here that recombinantly produced human endostatin interacts with ␣5and ␣v-integrins on the surface of human endothelial cells. We further demonstrate that the endostatin-integrin interaction is of functional significance in vitro, as we found that immobilized endostatin supports endothelial cell survival and migration in an integrin-dependent manner. Soluble endostatin in turn inhibits integrin-dependent endothelial cell functions, such as cell migration. Taken together, these results implicate integrins as potential targets for endostatin function and support the importance of integrins in endothelial cell biology and angiogenesis.