PECAM-1/CD31 trans-homophilic binding at the intercellular junctions is independent of its cytoplasmic domain; evidence for heterophilic interaction with integrin alphavbeta3 in Cis

PECAM-1/CD31 is a cell adhesion and signaling molecule that is enriched at the endothelial cell junctions. Alternative splicing generates multiple PECAM-1 splice variants, which differ in their cytoplasmic domains. It has been suggested that the extracellular ligand-binding property, homophilic versus heterophilic, of these isoforms is controlled by their cytoplasmic tails. To determine whether the cytoplasmic domains also regulate the cell surface distribution of PECAM-1 splice variants, we examined the distribution of CD31-EGFPs (PECAM-1 isoforms tagged with the enhanced green fluorescent protein) in living Chinese hamster ovary cells and in PECAM-1-deficient endothelial cells. Our results indicate that the extracellular, rather than the cytoplasmic domain, directs PECAM-1 to the cell-cell borders. Furthermore, coculturing PECAM-1 expressing and deficient cells along with transfection of CD31-EGFP cDNAs into PECAM-1 deficient cells reveal that this PECAM-1 localization is mediated by homophilic interactions. Although the integrin alphavbeta3 has been shown to interact with PECAM-1, this trans-heterophilic interaction was not detected at the borders of endothelial cells. However, based on cocapping experiments performed on proT cells, we provide evidence that the integrin alphavbeta3 associates with PECAM-1 on the same cell surface as in a cis manner.

Collagen, convulxin, and thrombin stimulate aggregation-independent tyrosine phosphorylation of CD31 in platelets. Evidence for the involvement of Src family kinases

Platelet endothelial cell adhesion molecule-1 (CD31) is a 130-kDa glycoprotein receptor present on the surface of platelets, neutrophils, monocytes, certain T-lymphocytes, and vascular endothelial cells. CD31 is involved in adhesion and signal transduction and is implicated in the regulation of a number of cellular processes. These include transendothelial migration of leukocytes, integrin regulation, and T-cell function, although its function in platelets remains unclear. In this study, we demonstrate the ability of the platelet agonists collagen, convulxin, and thrombin to induce tyrosine phosphorylation of CD31. Furthermore, we show that this event is independent of platelet aggregation and secretion and is accompanied by an increase in surface expression of CD31. A kinase capable of phosphorylating CD31 was detected in CD31 immunoprecipitates, and its activity was increased following activation of platelets. CD31 tyrosine phosphorylation was reduced or abolished by the Src family kinase inhibitor PP2, suggesting a role for these enzymes. In accordance with this, each of the Src family members expressed in platelets, namely Fyn, Lyn, Src, Yes, and Hck, was shown to co-immunoprecipitate with CD31. The involvement of Src family kinases in this process was confirmed through the study of mouse platelets deficient in Fyn.

Ultrastructural and morphometric studies related to expression of the cell adhesion molecule PECAM-1/CD31 in developing rat lung

It has recently been postulated that platelet/endothelial cell adhesion molecule-1 (PECAM-1/CD31) might play a role in vascular tube formation. To evaluate the role of PECAM-1/CD31 in the formation of the capillary network in vivo, we conducted an ultrastructural immunohistochemical evaluation of the localization of PECAM-1/CD31 and its developmentally regulated expression in the periphery of the lungs of fetal, newborn, and adult rats. PECAM-1/CD31 was present mainly on luminal surfaces and at the junctions between endothelial cells. Moreover, in fetal lung, products of the immunoreaction were also found on the abluminal surfaces of endothelial cells. To relate those findings to the developmental changes in the capillary area of the lung, we performed a morphometric study of electronmicrographs. The cross-sectional area of blood vessels at the periphery of the lungs was significantly greater in 15-19-day-old fetuses than in postpartum animals (p<0.0001). Disappearance of the expression of PECAM-1/CD31 on the abluminal endothelial surface paralleled the changes in the cross-sectional area of blood vessels that occurred during the perinatal period. (J Histochem Cytochem 48:1283-1289, 2000)

Increased expression of inflammatory cytokines and adhesion molecules by alveolar macrophages of human lung allograft recipients with acute rejection: decline with resolution of rejection

BACKGROUND

Alveolar macrophages (AM) are the major population in bronchoalveolar lavage (BAL) cells; we assessed their role in human lung allograft recipients by correlating the expression of adhesion molecules and inflammatory cytokines with clinical outcome of allograft.

METHODS

We obtained BAL samples from patients and enriched them for AM in plastic petri dish for 2 hours at 37 degrees C in 5% CO(2). Expression of intercellular adhesion molecule-1 (ICAM-1, CD54), platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31), and CD11c was assessed by flow cytometry using monoclonal antibodies. We assessed cytokine profile using Multi-Probe RNase protection assay.

RESULTS

Alveolar macrophages that express CD11c, CD31 and CD54 were increased in patients with either rejection or infection compared with those without rejection and infection. The difference in the percentage of AM expressing CD11c and CD31 between the rejection group and patients without rejection and infection group was statistically significant (CD11c, p < 0.01; CD31, p < 0.03). Interleukin (IL)-1 alpha, IL-1 beta, IL-1 receptor antagonist (IL-1Ra), and IL-6 expression was higher in the rejection group than in patients without rejection. Five out of 9 patients in the rejection group expressed high levels of IL-15 and tumor necrosis factor-alpha compared with patients without rejection and infection. The increased number of AM expressing adhesion molecules and elevated expression of cytokines observed during acute rejection declined to basal levels after successful treatment and resolution of rejection. This study demonstrates that lung allograft rejection is associated with increased expression of adhesion molecules and inflammatory cytokines by AM, which could facilitate mononuclear cell adhesion and extravasation contributing to the allograft injury in lung transplant recipients.

Co-expression of beta-endorphin with adhesion molecules in a model of inflammatory pain

Opioid-containing immunocytes migrate to inflamed sites where they release beta-endorphin which activates peripheral opioid receptors and produces analgesia. The immigration of immunocytes to sites of inflammation is mediated by adhesion molecules. In this study, the expression of L-, P-, E-selectin and platelet-endothelial adhesion molecule-1 (PECAM-1) in relation to beta-endorphin expression was analyzed by immunohistochemistry in inflamed tissues. The proportion of immunocytes expressing L-selectin was increased in inflamed lymph nodes and subcutaneous paw tissue. P-selectin and PECAM-1 were constitutively expressed on endothelia of noninflamed lymph nodes and subcutaneous tissue and were upregulated in inflammation. beta-endorphin positive cells expressed L-selectin in lymph nodes and subcutaneous tissue. Upregulation of P-selectin and PECAM-1 and the co-localization of L-selectin and beta-endorphin in immunocytes suggest an important role of these adhesion molecules for the recruitment of immunocytes containing beta-endorphin to sites of painful inflammation.

A role for hematopoietic stem cells in promoting angiogenesis

Angiogenesis is an important event for embryonic organogenesis as well as for tissue repair in the adult. Here, we show that hematopoietic stem cells (HSCs) play important roles for angiogenesis during embryogenesis. To investigate the role of HSCs in endothelial cell (EC) development, we analyzed AML1-deficient embryos, which lack definitive hematopoiesis. These embryos showed defective angiogenesis in the head and pericardium. Para-aortic splanchnopleural (P-Sp) explant cultures on stromal cells (P-Sp culture) did not generate definitive hematopoietic cells and showed defective angiogenesis in the AML1 null embryo. Disrupted angiogenesis in P-Sp cultures from AML1 null embryos was rescued by addition of HSCs or angiopoietin-1 (Ang1). HSCs, which express Ang1, directly promoted migration of ECs in vivo and in vitro. These results indicate that HSCs are critical for angiogenesis.

Complete lack of NF-kappaB activity in IKK1 and IKK2 double-deficient mice: additional defect in neurulation

NF-kappaB activity is induced by cytokines, stress, and pathogens. IKK1 and IKK2 are critical IkappaB kinases in NF-kappaB activation. In this study mice lacking IKK1 and IKK2 died at E12. Additional defect in neurulation associated with enhanced apoptosis in the neuroepithelium was also observed. MEF cells from IKK1(-/-)/IKK2(-/-) embryos did not respond to NF-kappaB inducers. Upon crossing with kappaB-lacZ transgenic mice, double-deficient embryos also lost lacZ transgene expression in vascular endothelial cells during development. Our data suggest that IKK1 and IKK2 are essential for NF-kappaB activation in vivo and have an important role in protecting neurons against excessive apoptosis during development.

Annexin I is stored within gelatinase granules of human neutrophil and mobilized on the cell surface upon adhesion but not phagocytosis

Annexin I, a member of the calcium- and phospholipid-binding annexin superfamily of proteins, is largely present in human neutrophils. To determine its exact intracellular distribution a combination of flow cytometry, confocal microscopy and electron microscopy analyses were performed on resting human neutrophils as well as on cells which had been activated. In resting neutrophils, annexin I was found to be present in small amounts in the nucleus, in the cytoplasm and partially also associated with the plasma membrane. The cytoplasmic pool of annexin I was predominant, and the protein was co-localized with gelatinase (marker of gelatinase granules), but not with human serum albumin or CD35 (markers of secretory vesicles), or with lysosomes. Electron microscopy showed the presence of annexin I inside the gelatinase granules. Neutrophil adhesion to monolayers of endothelial cells, but not phagocytosis of particles of opsonized zymosan, provoked an intense mobilization of annexin I, with a marked externalization on the outer leaflet of the plasma membrane. Remaining intracellular annexin I was also found in proximity of the plasma membrane. These results provide a novel mechanism for annexin I secretion from human neutrophils, which is via a degranulation event involving gelatinase granules.

Vascular adhesion protein-1, intercellular adhesion molecule-1 and P-selectin mediate leukocyte binding to ischemic heart in humans

OBJECTIVES

The expression of endothelial adhesion molecules and their functional significance in leukocyte adhesion to human myocardial blood vessels in acute myocardial infarction (AMI) were studied.

BACKGROUND

Leukocyte extravasation, mediated by specific adhesion molecules, exacerbates tissue injury after restoration of blood supply to an ischemic tissue. Experimental myocardial reperfusion injury can be alleviated with antibodies that block the function of adhesion molecules involved in leukocyte emigration, but the relevant molecules remain poorly characterized in human AMI.

METHODS

Semiquantitative immunohistochemistry and in vitro adhesion assays were used to study the expression and granulocyte binding abilities of different endothelial adhesion molecules in human AMI. Changes in the molecular nature of vascular adhesion protein-1 (VAP-1) were evaluated using immunoblotting.

RESULTS

Certain endothelial adhesion molecules (intercellular adhesion molecule [ICAM-2], CD31 and CD73) were expressed in myocardial blood vessels homogeneously in normal and ischemic hearts, whereas others (E-selectin and peripheral lymph node addressin) were completely absent from all specimens. The synthesis of ICAM-1 was locally, and that of P-selectin regionally, upregulated in the infarcted hearts when compared with nonischemic controls. Vascular adhesion protein-1 showed ventricular preponderance in expression and alterations in posttranslational modifications during ischemia-reperfusion. Importantly, P-selectin, ICAM-1 and VAP-1 mediated granulocyte binding to blood vessels in the ischemic human heart.

CONCLUSIONS

Human P-selectin, ICAM-1 and VAP-1 appear to be the most promising targets when antiadhesive interventions preventing leukocyte-mediated tissue destruction after myocardial ischemia are planned.

Blockade of the epidermal growth factor receptor signaling by a novel tyrosine kinase inhibitor leads to apoptosis of endothelial cells and therapy of human pancreatic carcinoma

We determined whether down-regulation of the epidermal growth factor-receptor (EGF-R) signaling pathway by oral administration of a novel EGF-R tyrosine kinase inhibitor (PKI166) alone or in combination with gemcitabine (administered i.p.) can inhibit growth and metastasis of human pancreatic carcinoma cells implanted into the pancreas of nude mice. Therapy beginning 7 days after orthotopic injection of L3.6pl human pancreatic cancer cells reduced the volume of pancreatic tumors by 59% in mice treated with gemcitabine only, by 45% in those treated with PKI166 only, and by 85% in those given both drugs. The combination therapy also significantly inhibited lymph node and liver metastasis, which led to a significant increase in overall survival. EGF-R activation was significantly blocked by therapy with PKI166 and was associated with significant reduction in tumor cell production of VEGF and IL-8, which in turn correlated with a significant decrease in microvessel density and an increase in apoptotic endothelial cells. Collectively, our results demonstrate that oral administration of an EGF-R tyrosine kinase inhibitor decreased growth and metastasis of human pancreatic cancer growing orthotopically in nude mice and increased survival. The therapeutic effects were mediated in part by inhibition of tumor-induced angiogenesis attributable to a decrease in production of proangiogenic molecules by tumor cells and increased apoptosis of tumor-associated endothelial cells.

Nuclear factor-kappaB activity correlates with growth, angiogenesis, and metastasis of human melanoma cells in nude mice

The purpose of this study was to determine the role of nuclear factor (NF)-kappaB/relA activity in the induction of angiogenesis and production of metastasis by human melanoma cells. Highly metastatic melanoma variant cells expressed high levels of constitutive NF-kappaB activity. Transfection of highly metastatic human melanoma variant cells with a dominant-negative mutant inhibitor of nuclear factor-kappaB alpha (Ikappabeta alpha) expression vector (Ikappabeta alphaM) decreased the level of constitutive NF-kappaB activity, inhibited s.c. tumor growth, and prevented lung metastasis in nude mice. Furthermore, the slow-growing s.c. tumors formed by the IkappaB alphaM-transfected cells exhibited a decrease in microvessel density (angiogenesis), which correlated with a decrease in the level of interleukin-8 expression. Collectively, these results demonstrate that NF-kappaB/reLA activity significantly contributes to tumorigenicity, angiogenesis, and metastasis of human melanoma cells implanted in nude mice.

Platelet-endothelial cell adhesion molecule-1 gene expression in liver sinusoidal endothelial cells during liver injury and repair

BACKGROUND/AIMS

Platelet-endothelial cell adhesion molecule (PECAM)-1 is suggested to be critical for transmigration processes. It is a matter of debate whether PECAM-1 is expressed in liver sinusoids and whether it is involved in liver inflammation.

METHODS

Indirect immunostaining and in situ hybridization was used to analyze PECAM-1 gene expression in normal and diseased rat and human livers as well as in isolated rat sinusoidal endothelial cells (SECs), hepatic stellate cells and hepatocytes. At various time points after the administration of CCl4 (6 h, 24 h, 48 h, and 72 h), PECAM-1 gene expression was analyzed in livers and in SECs by immunostaining, and Northern blot analysis.

RESULTS

In normal rat or human livers PECAM-1 immunoreactivity was detected along the sinusoids in a pattern similar to ICAM-1 staining. PECAM-1 specific transcripts were detected in freshly isolated and cultured SECs. After a single CCl4-administration, PECAM-1 immunoreactivity did not increase along the sinusoids in contrast to the early increase of ICAM-1. Northern blot analysis indicated that PECAM-1 expression in liver tissue and in isolated SECs does not increase after a single administration of CCl4, whereas ICAM-1 steady-state level increased after 6 h. In diseased human livers PECAM-1 was detectable along the sinusoids, within inflammatory infiltrates and within fibrotic septa. Neither in acutely nor chronically diseased human livers was an obvious increase of PECAM-1 immunoreactivity detectable.

CONCLUSIONS

PECAM-1 is expressed by SECs. In contrast to ICAM-1, PECAM-1 transcript level is not enhanced during liver damage.

Expression of endothelial cell adhesion molecules on heart valves: up-regulation in degeneration as well as acute endocarditis

Inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha), as well as shear stress, cause endothelial cells (ECs), to undergo not only functional alterations but also structural reorganizations, which contribute to vascular leakage. Like ECs of the human aorta, ECs on heart valves are exposed to extreme shear stress. However, while ECs expression of cell adhesion molecules (CAMs) in large vessels has been widely studied, it seems that there are no such studies on ECs of heart valves, although this knowledge might be important for our understanding of the aetiological aspects of local inflammatory responses. Using immunohistochemistry, this study characterized the CAM expression of ECs on degenerative, mostly calcified heart valves and on heart valves with florid endocarditis. As expected, the constitutively expressed molecules (ICAM-1, CD34, CD31) were found both on degenerative and on inflamed valves. Furthermore, marked expression of E-selectin and VCAM-1 was found not only on inflamed valves, but also on larger portions of the degenerative valves with no morphological evidence of inflammation. This striking finding might help to explain why patients with fibrotic heart valves are susceptible to recurrent endocarditis. Why the endothelial activation markers E-selectin and VCAM-1 are expressed on degenerative heart valves requires further investigation.

Expression of intercellular adhesion molecules in human saphenous veins: effects of inflammatory cytokines and neointima formation in culture

Atherosclerosis causes occlusions in as many as 50% of human saphenous vein coronary artery bypass grafts. Monocyte infiltration is an early step in saphenous vein-graft atherosclerosis, however, comparatively little is known of its underlying mechanisms. As a first approach, we sought to define the occurrence, location and regulation of leukocyte adhesion molecules in human saphenous vein before and after surgical preparation for grafting, during neointima formation in culture and on stimulation with inflammatory cytokines. We compared the distribution of intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM-1) and platelet endothelial cell adhesion molecule (PECAM-1 or CD-31) in endothelial cells and smooth muscle cells (SMCs), using immunocytochemistry. ICAM-1 was expressed on endothelial cells before culture and on both endothelial cells and medial or neointimal SMCs after culturing vein for 14 days in 30% foetal bovine serum or after culturing for 24 h with TNF-alpha. Relative tissue levels of ICAM-1 measured by Western blotting were significantly elevated by culturing freshly-isolated (0.02+/-0.01 to 0.18+/-0.03) and surgically-prepared (0.02+/-0.01 to 0.14+/-0.03; n=6) veins or following TNF-alpha treatment of surgically-prepared veins (0.04+/-0.01 to 0.32+/-0.11, n=7). VCAM-1 was undetectable before or after culturing but was strongly upregulated on endothelial cells by incubation with the cytokines TNF-alpha, IL-1alpha or interferon-gamma. PECAM-1 was expressed constitutively on endothelial cells. We conclude that human saphenous vein expresses several adhesion molecules capable of mediating monocyte migration. The increased expression of ICAM-1 in SMC after culturing or cytokine treatment and of VCAM-1 in endothelial cells suggests that interactions with beta1 and beta2 integrins are important pathways for stimulated monocyte ingress into human saphenous vein grafts.

CD40L activation in circulating platelets in patients with acute coronary syndrome

The CD40-CD40L interaction, which was initially shown to have important roles in the T cell-mediated activation of B cells during humoral immune responses, is now known to have roles in activation of endothelial cells, smooth muscle cells, and macrophages within atherosclerotic plaques. Recently, CD40L expression was found in activated platelets in the thrombus in vivo and CD40L was reported to be responsible for the platelet-mediated activation of endothelial cells in vitro. To investigate the activation status of platelets in coronary artery disease patients, we tested expression levels of CD40L, and platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31) in platelets isolated from peripheral blood, using flow cytometric analysis. Twenty-nine patients with acute coronary syndrome (10 acute myocardial infarction and 19 unstable angina patients) were compared with 14 normal subjects or 14 stable angina patients. In platelets isolated from normal subjects, the expression of CD40L was not detected in all subjects. In the patients with acute coronary syndrome, the average level of CD40L showed a significant increase (p = 0.0028), while stable angina patients did not have any increase when compared to normal subjects. Patients with more complex lesions or vessel occlusion tended to have a high platelet CD40L level compared to patients who do not. The expression levels of CD31 were increased in a small portion of the ACS patients. These data indicate that the rupture of plaque and subsequent formation of thrombus may lead to the activation of CD40L expression in circulating platelets of ACS patients.

Effects of hyperthermia and tumour necrosis factor on inflammatory cytokine secretion and procoagulant activity in endothelial cells

The application of hyperthermia (HT) and tumour necrosis factor alpha (TNF) in isolation perfusion of the limb or liver results in regression of advanced cancers confined to these regions of the body in most patients and are thought to exert anti-tumour effects primarily on tumour neovasculature. However, the individual contribution of either treatment factor on endothelial cells (EC) are not known. In this study, we investigated the in vitro effects of moderate and severe HT on human umbilical vein EC (HUVEC) with and without TNF in clinically relevant doses. HUVEC were exposed to normothermia (37 degrees C) or moderate (39 degrees C) and severe (41 degrees C) HT for 90 or 180 min with or without TNF (1 microg/ml). Cell viability, cytokine secretion (IL-6, IL-8, VEGF, ICAM-1, VCAM-1, RANTES, E-selectin, P-selectin, L-selectin, and PECAM-1), and induction of procoagulant activity as reflected in tissue factor (TF) production were assessed at the end of the treatment period and at several time points thereafter. Neither HT nor TNF exerted significant cytotoxic effects on EC at the doses and temperatures used. HT resulted in increased production of PECAM-1 with little or no additional effect when combined with TNF. TNF caused increased secretion of IL-6, IL-8, ICAM-1, and VCAM-1 with little or no additional effect from HT. Increased E-selectin and RANTES levels were observed with TNF and HT only at 24 h after treatment. HT and TNF had mainly antagonistic effects on VEGF secretion with HT causing primarily decreased production and TNF causing increased VEGF secretion under all temperatures. Most notably, there was a rapid, prolonged and synergistic peak increase in procoagulant activity when TNF and HT were used in combination compared to TNF or HT treatment alone. These results indicate that TNF and HT exert primarily independent effects on inflammatory cytokine production in EC but synergistically increase procoagulant activity as reflected in TF production. These data provide a possible mechanism for the thrombotic effects in tumour neovasculature seen following isolation perfusion with these agents and provide a rationale for their combined use in this treatment setting.

Natural history of choroidal neovascularization induced by vascular endothelial growth factor in the primate

BACKGROUND

A new model of choroidal neovascularization (CNV) has been developed in the primate by implanting vascular endothelial growth factor (VEGF)-impregnated microspheres in the subretinal space.

METHODS

CNV was induced in Macaca mulatta monkeys by implanting VEGF-impregnated gelatin microspheres in the subretinal space. Progression of CNV was followed for 24 weeks after surgery using fluorescein angiography. Eyes were enucleated at various time points, and lesions were evaluated for evidence of CNV by light microscopy and by immunohistochemical staining.

RESULTS

CNV developed in 12 (92%) of 13 eyes. Fluorescein leakage was first observed in the 2nd postoperative week and was apparent for the following 12 weeks. CD31 staining for endothelial cells was first observed at day 7 and was evident for the following 8 weeks. Glial fibrillary acidic protein staining revealed a glial adhesion between the proliferative membrane and the retina at 6 weeks after implantation. Smooth muscle actin-positive cells were found a +2 weeks and remained prominent for at least the next 6 weeks. Cytokeratin-positive retinal pigment epithelial (RPE) cells, first identified in the proliferative membrane at day 3, predominated throughout the growth of the membrane. Macrophages (RAM-II positive) were present at day 3 but were no longer observed after day 7.

CONCLUSION

In monkeys, subretinal implantation of VEGF-impregnated gelatin microspheres leads to the development of CNV. Early, disciform and reparative stages of CNV were observed, similar to those seen in humans. This model will be useful for studying the pathogenesis of CNV and for evaluating potential treatment strategies.

Hot spot microvessel density and the mitotic activity index are strong additional prognostic indicators in invasive breast cancer

AIMS

Recent studies have drawn attention to intratumoral microvessel density (MVD) as a prognostic factor in invasive breast cancer. Various methods have been applied to assess MVD and the prognostic value of MVD in different studies varies considerably. Counting of microvessels in the most highly vascularized area (hot spot) of a tumour is the method most widely used. In this study we compared three counting methods.

METHODS AND RESULTS

To assess MVD in 112 cases of invasive breast cancer with long-term follow-up we performed microvessel counting in the hot spot of the tumour in four and 10 fields of vision (HS-MVD4 and HS-MVD10) and microvessel counting in 10 fields of vision distributed systematically over the whole tumour area (global MVD). The HS-MVD4, HS-MVD10 and global MVD showed good correlations with each other. HS-MVD4 provided the highest number of microvessels (median value 71) followed by HS-MVD10 and global MVD, with median values of 58 and 39, respectively. HS-MVD4 showed the best prognostic value for overall survival (P = 0.0001) whereas HS-MVD10 showed less (P = 0.01) and the global MVD showed no (P = 0.75) prognostic value. In univariate analysis, the HS-MVD4 was the second strongest prognostic factor after tumour size. In multivariate survival analysis, the HS-MVD4, mitotic activity index (MAI), lymph node status and tumour size were found to be independent prognostic factors. When combining MVD4 and MAI in lymph node negative patients, none of the patients with low MVD (< 71/mm2) and a low MAI (< 10 per 10 HPF) died, in contrast to patients with a high MVD or high MAI who have a 10-year survival of 57%.

CONCLUSIONS

These data suggest that the hot spot MVD in four fields of vision is a major independent prognostic factor for overall survival in invasive breast cancer. For the first time, it is shown that hot spot MVD provides additional prognostic information to well established factors like lymph node status and the MAI, and may therefore be useful for designing treatment strategies in invasive breast cancer.

Cellular localisation of HHV-8 in Castleman's disease: is there a link with lymph node vascularity?

AIMS

Human herpesvirus 8 (HHV-8) has been identified in multicentric Castleman's disease and in angioimmunoblastic lymphadenopathies. However, the presence of the virus does not necessarily indicate an aetiological role in these conditions. This study investigates the cell types infected by HHV-8 in Castleman's disease and examines the correlation between HHV-8 and Castleman's disease lymph node angiogenesis.

METHODS

Sixteen formalin fixed, paraffin wax embedded samples from patients with Castleman's disease (six multicentric, 10 solitary) were examined for the presence of HHV-8 using the polymerase chain reaction (PCR), non-isotopic in situ hybridisation, PCR in situ hybridisation (PCR-ISH), and real time quantitative TaqMan PCR to HHV-8 open reading frame 26 (ORF-26), and viral (v)-cyclin encoding regions. Vascularity was assessed using CD34, CD31, and factor VIII immunocytochemistry, and lymph nodes were scored as "low" or "high".

RESULTS

Five multicentric Castleman's disease and two solitary Castleman's disease biopsies were positive for HHV-8. HHV-8 was identified in approximately 10% of intranodal B lymphocytes, in endothelial cells, and in subcapsular spindle cell proliferations. The copy number of HHV-8 was low at 10-50 copies/1000 cells. The highest copy number was in subcapsular spindle cells. There was no correlation between vascularity score and HHV-8 status.

CONCLUSION

The preferential localisation of HHV-8 in subcapsular spindle cell proliferations (where early intranodal Kaposi's sarcoma initiates) and endothelial cells in Castleman's disease might finally explain the link between intranodal Kaposi's sarcoma and Castleman's disease.

Identification of natural ligands for SH2 domains from a phage display cDNA library

The cytoplasmic domain of the Fc gamma receptor IIB (FcgammaRIIB) can be successfully displayed on the surface of filamentous phage, and after phosphorylation in vitro, can interact specifically with the SH2 domains of SHP-2, a cytoplasmic tyrosine phosphatase. When full-length FcgammaRIIB is expressed on phage, however, this interaction is greatly compromised, illustrating that characteristics of the full-length sequence are not well tolerated by the phage display system. Many associations in cell physiology are driven by similar interactions involving small modular binding domains or ligands, and so a fragmented cDNA library will facilitate display of such domains free of sequences which compromise their expression. A fragmented leukocyte cDNA display library of 10(8) clones was constructed. This library was phosphorylated in vitro with fyn kinase and was selected against the tandem SH2 domains of SHP-2 in the search for additional ligands. A depletion strategy to remove non-specific clones was employed, using SHP-2 Sepharose, prior to in vitro phosphorylation and selection. This permitted the emergence of clones encoding the cytoplasmic domain of PECAM-1, another natural ligand for SHP-2. The importance of dual phosphorylation of tyrosine residues at positions 663 and 686 was confirmed in competition ELISA experiments using phosphorylated phage and synthetic peptides. Thus, phage display of fragmented cDNA libraries permits the identification and characterisation of phosphorylated ligands of modular binding domains based on their functional interaction.

Characterization of the vasculogenic block in the absence of vascular endothelial growth factor-A

Vascular endothelial growth factor (VEGF) signaling is required for both differentiation and proliferation of vascular endothelium. Analysis of differentiated embryonic stem cells with one or both VEGF-A alleles deleted showed that both the differentiation and the expansion of endothelial cells are blocked during vasculogenesis. Blood island formation was reduced by half in hemizygous mutant VEGF cultures and by 10-fold in homozygous mutant VEGF cultures. Homozygous mutant cultures could be partially rescued by the addition of exogenous VEGF. RNA levels for the endothelial adhesion receptors ICAM-2 and PECAM were reduced in homozygous mutant cultures, but ICAM-2 RNA levels decreased substantially, whereas PECAM RNA levels remained at hemizygous levels. The quantitative data correlated with the antibody staining patterns because cells that were not organized into vessels expressed PECAM but not ICAM-2. These PECAM+ cell clumps accumulated in mutant cultures as vessel density decreased, suggesting that they were endothelial cell precursors blocked from maturation. A subset of PECAM+ cells in clumps expressed stage-specific embryonic antigen-1 (SSEA-1), and all were ICAM-2(-) and CD34(-), whereas vascular endothelial cells incorporated into vessels were PECAM(+), ICAM-2(+), CD34(+), and SSEA-1(-). Analysis of flk-1 expression indicated that a subset of vascular precursor cells coexpressed PECAM and flk-1. These data suggest that VEGF signaling acts in a dose-dependent manner to affect both a specific differentiation step and the subsequent expansion of endothelial cells. (Blood. 2000;95:1979-1987)

CD31 immunoreactivity in small round cell tumors

CD31 has been shown to be a sensitive and specific marker for endothelial differentiation among epithelioid and spindled-pleomorphic human neoplasms. However, the role of this marker in the evaluation of small round cell tumors has not been evaluated. Formalin-fixed, paraffin-embedded tissue sections from 276 small round cell tumors, including 85 Ewing's sarcoma/primitive neuroectodermal tumors (ES/PNET), 52 rhabdomyosarcomas, 10 extraabdominal polyphenotypic small cell tumors, six desmoplastic small cell tumors, 11 neuroblastomas, 23 Wilms' tumors, 20 retinoblastomas, 13 esthesioneuroblastomas, and 56 small cell malignant lymphomas were stained with CD31 (JC/70A, 1:40), using a modified avidinbiotin-peroxidase complex technique, after citrate buffer microwave epitope retrieval. Among nonlymphoid small round cell tumors, four of 85 ES/PNET were at least focally reactive. No other lesion in this group was positive. In contrast, the majority of well-differentiated (11 of 17), intermediately differentiated (two of three), and lymphoblastic lymphomas (three of three) were positive. Small cleaved lymphomas (three of 13 follicular, one of 13 diffuse) were less often reactive, whereas small noncleaved lesions were negative. Although reactivity for CD31 in ES/PNET is uncommon, the presence of platelet/endothelial cell adhesion molecule in a small cell neoplasm should not in isolation be taken as evidence of hematopoietic origin. These results further define the utility of CD31 in the evaluation of human neoplasms.

Endoglin expression is reduced in normal vessels but still detectable in arteriovenous malformations of patients with hereditary hemorrhagic telangiectasia type 1

Endoglin is predominantly expressed on endothelium and is mutated in hereditary hemorrhagic telangiectasia (HHT) type 1 (HHT1). We report the analysis of endoglin in tissues of a newborn (family 2), who died of a cerebral arteriovenous malformation (CAVM), and in a lung specimen surgically resected from a 78-year-old patient (family 5), with a pulmonary AVM (PAVM). The clinically affected father of the newborn revealed a novel mutation that was absent in his parents and was identified as a duplication of exons 3 to 8, by quantitative multiplex polymerase chain reaction. The corresponding mutant protein (116-kd monomer) and the missense mutant protein (80-kd monomer) present in family 5 were detected only as transient intracellular species and were unreactive by Western blot analysis and immunostaining. Normal endoglin (90-kd monomer) was reduced by 50% on peripheral blood-activated monocytes of the HHT1 patients. When analyzed by immunostaining and densitometry, presumed normal blood vessels of the newborn lung and brain and vessels adjacent to the adult PAVM showed a 50% reduction in the endoglin/PECAM-1 ratio. A similar ratio was observed in the CAVM and PAVM, suggesting that all blood vessels of HHT1 patients express reduced endoglin in situ and that AVMs are not attributed to a focal loss of endoglin.

Vascular adrenal pseudocyst: cytologic and immunohistochemical study

Adrenal vascular cysts are rare lesions that might be considered in the differential diagnosis of adrenal tumors. Their origin is not clear. We report the clinicopathological findings of a large adrenal hemorrhagic pseudocyst (AHP) in a 73-yr-old man who complained of abdominal pain. An abdominal CT showed a 9 cm tumor in the left adrenal. A fine-needle aspiration biopsy (FNAB) was hemorrhagic and inconclusive. The tumor was excised and touch imprints were taken showing groups of spindled and fusiform cells with elongated nuclei, without atypia. Histologically, the tumor was well delimited by a fibrous capsule and contained numerous cystic spaces lined by endothelial cells and filled with erythrocytes, fibrin thrombus, and necrotic debris. Immunohistochemical study showed strong positivity for factor VIII-RA, CD31, and CD34. Also, the remaining adrenal showed a prominent frame of thin and medium caliber vessels, supporting a vascular origin for this entity. This case illustrates the difficulty in making a diagnosis by FNA and to keep in mind AHP when hematic aspirates are obtained from an adrenal tumor mass.

Angiogenic switch occurs late in squamous cell carcinomas of human skin

Angiogenesis is a crucial event in carcinogenesis and its onset has been associated with premalignant tumour stages. In order to elucidate the significance of angiogenesis in different stages of epithelial skin tumours, we analysed the vessel density in ten normal skin samples, 14 actinic keratosis (AK), 12 hypertrophic AKs, and in nine early- and 16 late-stage squamous cell carcinomas (SCCs). Mean vascular density was quantitated by counting the number of CD 31-immunostained blood vessels and by morphometric assessment of stained vessel area by computer-assisted image analysis. The results from both methods were well correlated. Mean vascular density was similar in normal dermis and in AK, and only slightly elevated in hypertrophic AKs and early SCC stages (tumour thickness < 2 mm). Only late-stage SCCs infiltrating the subcutis exhibited a significant increase in vascularization. Vessel density was independent of tumour localization, degree of proliferation and inflammatory cell infiltration. Furthermore, tumour vascularization was not correlated with the expression of vascular endothelial growth factor, a major angiogenic factor, as revealed by in situ hybridization and immunohistochemistry. The restriction of enhanced vascularization to increased tumour thickness may be a major reason for the rather low metastatic spread of cutaneous SCCs.

Increased in situ expression of nitric oxide synthase in human colorectal cancer

There is growing evidence that nitric oxide (NO) has an important role in tumor growth. However, information on the expression of NO synthase (NOS) in colorectal cancers is scanty. We therefore investigated the distribution and expression of NOS in human colorectal cancers. The expression of three types of NOS, inducible (iNOS), endothelial (eNOS) and neuronal (nNOS), was examined by immunohistochemistry in 25 cases of colorectal cancer. The expression of iNOS was also investigated at the mRNA level using the reverse transcriptase polymerase chain reaction (RT-PCR) in 6 cases. Correlations were made between iNOS expression and the histopathological findings. Immunoreactive iNOS was detected in the tumor cells in 22 cases (88%) with diffuse cytoplasmic reactions. Expression of iNOS-mRNA detected by RT-PCR in three tumor tissues was over five-fold that in normal mucosa. Intensified immunoreactivity of iNOS was associated with vascular invasion. iNOS expression did not correlate with pathological staging, tumor size, lymph node metastasis, p53 expression or tumor vessel density. Immunoreactive eNOS stained more strongly in the endothelial cells of microvessels within and around the tumor than in the areas remote from the tumor. There is enhanced expression of iNOS and eNOS in human colorectal cancers, which may correlate with tumor growth and vascular invasion.

Identification of a functional NF-kappa B site in the platelet endothelial cell adhesion molecule-1 promoter

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a type I transmembrane adhesion protein of 130 kDa that belongs to a subgroup of the Ig gene superfamily, characterized by the presence of immunoreceptor tyrosine-based inhibitory motifs. PECAM-1 is expressed in circulating platelets, monocytes, neutrophils, a selective subgroup of T cells, and in endothelial cells, where it is preferentially located at intercellular junctions and participates in leukocyte transmigratory processes. The identification of two consensus NF-kappa B sites within the PECAM-1 promoter led us to analyze their possible involvement in the PECAM-1 expression regulated by inflammatory stimuli. We found that surface expression and promoter activity of PECAM-1 in myeloid cells are regulated by modulators of NF-kappa B, including TNF-alpha, PMA, and pyrrolidine dithiocarbamate. Mobility shifts assays identified a specific NF-kappa B-binding element at +110/+120, whose mutation abolished the basal promoter activity of PECAM-1 and decreased NF-kappa B-dependent responses of the PECAM-1 gene promoter. Furthermore, cotransfection experiments with an expression vector encoding the p65 subunit of NF-kappa B showed transactivation of the PECAM-1 promoter. These results demonstrate that NF-kappa B can regulate the transcriptional activity of PECAM-1.

Prognosis of breast-carcinoma lymphagenesis evaluated by immunohistochemical investigation of vascular-endothelial-growth-factor receptor 3

Very few studies have yet addressed the question of the existence and role of lymphagenesis in tumor growth; it is generally overshadowed by the greater emphasis placed on the blood vascular system. Monoclonal antibodies against vascular endothelial-growth-factor receptor 3 (VEGFR3) have been shown to provide a specific antigenic marker for lymphatic endothelium. By comparison with the microvascular count (MVC), we investigated the prognostic value of the microlymphatic count (MLC) in a series of 60 cases of 2-cm-diameter breast carcinomas. The mean value of MVC was 72.5 and of MLC, 40.5. There was no quantitative correlation between these 2 parameters. The MVC but not the MLC had a prognostic value in overall survival. Neither the MLC nor the MVC had any correlation with axillary-lymph-node invasion.

The CXC chemokine, monokine induced by interferon-gamma, inhibits non-small cell lung carcinoma tumor growth and metastasis

Angiogenesis is an absolute requirement for tumor growth beyond 2 mm3 in size. The balance in expression between opposing angiogenic and angiostatic factors controls the angiogenic process. The CXC chemokines are a group of chemotactic cytokines that possess disparate activity in the regulation of angiogenesis. Non-small cell lung carcinoma (NSCLC) has an imbalance in expression of ELR+ (angiogenic) compared with ELR- (angiostatic) CXC chemokines that favors angiogenesis and progressive tumor growth. We found that the level of the ELR- CXC chemokine MIG (monokine induced by interferon gamma) in human specimens of NSCLC was not significantly different from that found in normal lung tissue. These results suggested that the increased expression of ELR+ CXC chemokines found in these tumor samples is not counterregulated by a concomitant increase in the expression of the angiostatic ELR-CXC chemokine MIG. This would result in an even more profound imbalance in the expression of regulatory factors of angiogenesis that would favor neovascularization. We hypothesized that MIG might be an endogenous inhibitor of NSCLC tumor growth in vivo and that reconstituion of MIG in the tumor microenvironment would result in the inhibition of tumor growth and metastasis. In support of this hypothesis, we demonstrate here that overexpression of the ELR-CXC chemokine MIG, by three different strategies including gene transfer, results in the inhibition of NSCLC tumor growth and metastasis via a decrease in tumor-derived vessel density. These findings support the importance of the ELR- CXC chemokine MIG in inhibiting NSCLC tumor growth by attenuation of tumor-derived angiogenesis. Furthermore, these findings demonstrate the potential of gene therapy as an alternative means to deliver and overexpress a potent angiostatic CXC chemokine.

Monocytes induce reversible focal changes in vascular endothelial cadherin complex during transendothelial migration under flow

The vascular endothelial cell cadherin complex (VE-cadherin, alpha-, beta-, and gamma-catenin, and p120/p100) localizes to adherens junctions surrounding vascular endothelial cells and may play a critical role in the transendothelial migration of circulating blood leukocytes. Previously, we have reported that neutrophil adhesion to human umbilical vein endothelial cell (HUVEC) monolayers, under static conditions, results in a dramatic loss of the VE-cadherin complex. Subsequent studies by us and others (Moll, T., E. Dejana, and D. Vestweber. 1998. J. Cell Biol. 140:403-407) suggested that this phenomenon might reflect degradation by neutrophil proteases released during specimen preparation. We postulated that some form of disruption of the VE-cadherin complex might, nonetheless, be a physiological process during leukocyte transmigration. In the present study, the findings demonstrate a specific, localized effect of migrating leukocytes on the VE-cadherin complex in cytokine-activated HUVEC monolayers. Monocytes and in vitro differentiated U937 cells induce focal loss in the staining of VE-cadherin, alpha-catenin, beta-catenin, and plakoglobin during transendothelial migration under physiological flow conditions. These events are inhibited by antibodies that prevent transendothelial migration and are reversed following transmigration. Together, these data suggest that an endothelial-dependent step of transient and focal disruption of the VE-cadherin complex occurs during leukocyte transmigration.

Neuronal VEGF expression correlates with angiogenesis in postnatal developing rat brain

When exposed to chronic sublethal hypoxia the developing brain responds with increases in permeability and angiogenesis. Vascular endothelial growth factor (VEGF) may mediate this response. Here, we present data on the localization of VEGF in the rat brain cortex during postnatal development and its correlation to vascularization. We reared newborn rats under normoxic conditions and in hypoxic chambers (FiO(2) 9.5%), removed them at postnatal days (P) 3, 8, 13, 24, and 33 and prepared the cortical brain tissue for immunohistochemistry, in situ hybridization (ISH), Western blot analyses and vessel density counting. When compared to age-matched controls, hypoxic-reared animals displayed a significant increase in platelet endothelial cell adhesion molecule 1 (PECAM-1) protein levels, cerebral microvascular lumen diameter and number and density of vessels (number of capillaries per area). In control animals, ISH and immunohistochemistry revealed that localization of VEGF is restricted almost exclusively to cortical neurons at early stages of development. As the vascular bed begins to stabilize, predominant VEGF expression switches to maturing glial cells which invest vessels while neuronal expression is reduced to a basal level. In hypoxic animals, early localization of VEGF is also restricted to cortical neurons, however, during later developmental stages, glial cells express elevated levels of VEGF protein and high neuronal expression also persists. Thus chronic sublethal hypoxia disrupts the temporal-spatial expression of VEGF, which correlates with continuing hypoxia-driven angiogenesis.

Expression of vascular endothelial growth factor and angiogenesis in cardiac myxoma: a study of fifteen patients

OBJECTIVE

To clarify the association between angiogenesis and the clinicopathologic features in cardiac myxoma, vascular endothelial growth factor expression in the myxoma was examined by using reverse transcriptase polymerase chain reaction and immunohistochemistry, and the microvessel density was determined by counting microvessels in the myxoma by using immunostaining for platelet endothelial cell adhesion molecule 1.

METHODS

Seven fresh-frozen and 15 formalin-embedded tissues were analyzed by means of reverse transcriptase polymerase chain reaction and immunostaining for vascular endothelial growth factor, respectively. The microvessel density was measured in the 15 formalin-embedded tissues. Furthermore, immunostaining for proliferating cell nuclear antigen was performed, and the proliferating cell nuclear antigen-labeling index was calculated.

RESULTS

All of the 7 analyzed myxomas were positive for vascular endothelial growth factor messenger RNA, as determined by means of reverse transcriptase polymerase chain reaction, whereas atrial septum and atrium tissues were negative. Positive immunohistochemical reaction for vascular endothelial growth factor was observed in the cells of all 15 myxomas. The size of myxomas with high vascular endothelial growth factor expression was smaller than that of myxomas with low vascular endothelial growth factor expression. The microvessel density in myxomas with high vascular endothelial growth factor expression was higher than that in myxomas with low vascular endothelial growth factor expression. There was an inverse correlation between the tumor size and the ratio of the microvessel density in the central part to the microvessel density in the peripheral part of myxomas. Furthermore, there was an inverse correlation between the proliferating cell nuclear antigen-labeling index and the tumor size, and the prolferating cell nuclear antigen-labeling index in myxomas with high vascular endothelial growth factor expression was higher than that in myxomas with low vascular endothelial growth factor expression.

CONCLUSIONS

Cardiac myxomas produce vascular endothelial growth factor, which probably induces angiogenesis for tumor growth.

Malignant epithelioid vascular tumors of the pleura: report of a series and literature review

Primary malignant vascular tumors of the pleura are rare. The significance and difficulty of distinction between pleural epithelioid hemangioendothelioma (EHE) and angiosarcoma have not yet been addressed. A new series of pleural angiosarcoma is reported, and the relevant literature is reviewed. Five cases were identified from files of the authors' institutions and personal consultation cases (J.J.B.). Twenty-six cases of primary malignant vascular tumors of the pleura were identified in the literature. In a total of 31 cases, 22 were from the West and 9 from Japan. Patients were 22 to 79 years old (average, 57), and the male/female ratio was 9:1. Prior chronic pyothorax was identified only in cases reported from Japan. History of exposure to radiation or asbestos was noted in a few Western cases. The most common presentation was pleural thickening and effusion. Almost all of the patients died of disease shortly after diagnosis. A spectrum of histology ranging from characteristic high-grade epithelioid to relatively low-grade EHE-like features was observed in our cases and can be found in previous reports. Most cases showed variable spotty cytokeratin immunoreactivity. Endothelial markers (factor 8, CD34, or CD31) were invariably positive. Pleural angiosarcomas are often epithelioid and can be easily mistaken for mesothelioma or carcinoma clinically and histologically. Awareness of this rare tumor should prompt the use of endothelial markers when faced with a questionable mesothelioma. When cytokeratin is negative, or focal with strong vimentin reactivity, a vascular tumor should be suspected and confirmed with vascular markers. Because of their invariably aggressive behavior, all epithelioid vascular tumors of the pleura should be considered highly malignant regardless of the presence of EHE-like histological features.

Antibodies against the first Ig-like domain of human platelet endothelial cell adhesion molecule-1 (PECAM-1) that inhibit PECAM-1-dependent homophilic adhesion block in vivo neutrophil recruitment

Platelet endothelial cell adhesion molecule (PECAM-1), a member of the Ig superfamily, is found on endothelial cells and neutrophils and has been shown to be involved in the migration of leukocytes across the endothelium. Adhesion is mediated, at least in part, through binding interactions involving its first N-terminal Ig-like domain, but it is still unclear which sequences in this domain are required for in vivo function. Therefore, to identify functionally important regions of the first Ig-like domain of PECAM-1 that are required for the participation of PECAM-1 in in vivo neutrophil recruitment, a panel of mAbs against this region of PECAM-1 was generated and characterized in in vitro adhesion assays and in an in vivo model of cutaneous inflammation. It was observed that mAbs that disrupted PECAM-1-dependent homophilic adhesion in an L cell aggregation assay also blocked TNF-alpha-induced intradermal accumulation of neutrophils in a transmigration model using human skin transplanted onto SCID mice. Localization of the epitopes of these Abs indicated that these function-blocking Abs mapped to specific regions on either face of domain 1. This suggests that these regions of the first Ig-like domain may contain or be close to binding sites involved in PECAM-1-dependent homophilic adhesion, and thus may represent potential targets for the development of antiinflammatory reagents.

Role of nitric oxide in the regulation of acute and chronic inflammation

Recent studies by a number of different laboratories have implicated nitric oxide (NO) as an important modulator of a variety of acute and chronic inflammatory disorders. A hallmark of inflammation is the adhesion of leukocytes to post-capillary venular endothelium and the infiltration of leukocytes into the tissue interstitium. Leukocyte adhesion and infiltration is known to be dependent on interaction of the leukocytes with the endothelial cell surface via a class of glycoproteins collectively known as endothelial cell adhesion molecules (ECAMs). Several recent studies suggest that NO may modulate cytokine-induced ECAM expression in cultured endothelial cells in vitro by regulating the activation of nuclear transcription factor kappa B (NF-kappaB). This discussion reviews some of the more recent studies that assess the role of the different NOS isoforms on the inflammatory response in vivo.

Adhesion and migration of avian neural crest cells on fibronectin require the cooperating activities of multiple integrins of the (beta)1 and (beta)3 families

Based on genetic, functional and histological studies, the extracellular matrix molecule fibronectin has been proposed to play a key role in the migration of neural crest cells in the vertebrate embryo. In the present study, we have analyzed in vitro the repertoire and function of integrin receptors involved in the adhesive and locomotory responses of avian truncal neural crest cells to fibronectin. Immunoprecipitation experiments showed that neural crest cells express multiple integrins, namely (alpha)3(beta)1, (alpha)4(beta)1, (alpha)5(beta)1, (alpha)8(beta)1, (alpha)v(beta)1, (alpha)v(beta)3 and a (beta)8 integrin, as potential fibronectin receptors, and flow cytometry analyses revealed no major heterogeneity among the cell population for expression of integrin subunits. In addition, the integrin repertoire expressed by neural crest cells was found not to change dramatically during migration. At the cellular level, only (alpha)v(beta)1 and (alpha)v(beta)3 were concentrated in focal adhesion sites in connection with the actin microfilaments, whereas the other integrins were predominantly diffuse over the cell surface. In inhibition assays with function-perturbing antibodies, it appeared that complete abolition of cell spreading and migration could be achieved only by blocking multiple integrins of the (beta)1 and (beta)3 families, suggesting possible functional compensations between different integrins. In addition, these studies provided evidence for functional partitioning of integrins in cell adhesion and migration. While spreading was essentially mediated by (alpha)v(beta)1 and (alpha)8(beta)1, migration involved primarily (alpha)4(beta)1, (alpha)v(beta)3 and (alpha)8(beta)1 and, more indirectly, (alpha)3(beta)1. (alpha)5(beta)1 and the (beta)8 integrin were not found to play any major role in either adhesion or migration. Finally, consistent with the results of inhibition experiments, recruitment of (alpha)4(beta)1 and (alpha)v(beta)3, individually or in combination using antibodies or recombinant VCAM-1 and PECAM-1 molecules as a substratum, was required for migration but was not sufficient to produce migration of the cell population as efficiently as with fibronectin. In conclusion, our study indicates that neural crest cells express a multiplicity of fibronectin-binding integrins and suggests that dispersion of the cell population requires cooperation between distinct integrins regulating different events of cell adhesion, locomotion and, possibly, proliferation and survival.

Transendothelial migration of monocytes in rat aorta: distribution of F-actin, alpha-catnin, LFA-1, and PECAM-1

To determine changes in the distribution of cell adhesion molecules during diapedesis of monocytes in situ, we labeled aortic whole mounts from hypercholesterolemic rats with Texas red-phalloidin and antibodies to LFA-1, PECAM-1, or alpha-catenin, and analyzed them by laser scanning confocal microscopy. Monocytes transmigrated through circular openings (transmigration passages) formed by pseudopodia that penetrated between adjacent endothelial cells. Transmigrating monocytes remained spherical above the endothelium, while spreading beneath it. The transmigration passage was lined by F-actin and partially by alpha-catenin, suggesting cadherin-mediated heterotypic interactions. LFA-1 was present in clusters at the monocyte cell surface throughout diapedesis, but was concentrated at the margin of the transmigration passage. PECAM-1 was enriched in the endothelial contact regions where the monocytes transmigrated. PECAM-1 was barely detectable in monocytes before and after diapedesis, but appeared during diapedesis at the cell surface in the parts of the monocyte located above the endothelium. PECAM-1 was enriched near the endothelial cell-cell junctions, but was not detected in parts that spread beneath the endothelium. Our results suggest a major role for LFA-1 during diapedesis and reveal dynamic changes in the distribution of PECAM-1, the actin cytoskeleton, and alpha-catenin during monocyte diapedesis in situ.

Identification and characterization of three cDNAs that encode putative novel hyaluronan-binding proteins, including an endothelial cell-specific hyaluronan receptor

The glycosaminoglycan hyaluronan (HA) and HA-binding proteins (HABPs) serve important structural and regulatory functions during development and in maintaining adult tissue homeostasis. Here we have identified and partially characterized the sequence and expression pattern of three putative novel HABPs. DNA sequence analysis revealed that two of the novel HABPs, WF-HABP and BM-HABP, form a unique HA-binding subfamily, whereas the third protein, OE-HABP, is more closely related to the LINK subfamily of HABPs. Northern blotting experiments revealed that the expression of BM-HABP was highly restricted, with substantial expression detected only in human fetal liver. In contrast, WF-HABP and OE-HABP mRNAs were detected in a number of tissues, with particularly prominent expression in highly vascularized tissues such as the heart, placenta, and lung. Additional studies showed that OE-HABP was expressed by cultured human endothelial cells, smooth muscle cells, and differentiated monocytes. However, only endothelial cells expressed WF-HABP mRNA, and its expression was regulated by growth state, being most prominent in quiescent endothelial cells. We further characterized the expression of WF-HABP in vivo and found that its expression colocalized with CD31-positive cells and was prominently expressed in microvessels in the human aorta and in atherectomy samples. Our data suggest that WF-HABP is an endothelial cell-specific HA receptor and that it may serve a unique function in these cells. The WF-HABP gene was localized to chromosome 3p21.31 and the OE-HABP gene to 15q25.2-25.3.

Vascular-endothelial cadherin (CD144)- but not PECAM-1 (CD31)-based cell-to-cell contacts convey the maintenance of a quiescent endothelial monolayer

BACKGROUND

In vivo, all blood vessels are lined by a single layer of flattened noncycling endothelial cells. We tested the hypothesis that the maintenance of such a quiescent endothelial monolayer depends on homotypic contacts between not yet defined growth-inhibitory molecules located at interendothelial junctions.

METHODS

ECV304 cells, which lack endogenous vascular endothelial cadherin (VE cadherin) or CD31 expression, were transfected with cDNA encoding for the respective proteins or with the empty vector.

RESULTS

In VE cadherin transfectants, beta-catenin was targeted to junctional regions and the F-actin-based cytoskeleton formed parallel bundles reaching from one cell border to the other. In contrast, in CD31 transfectants and in empty vector cells, beta-catenin was dispersed throughout the cytoplasm, and F-actin formed short, plump and criss-cross bundles. On a two-dimensional plastic matrix, both, VE cadherin and CD31 transfectants formed clusters of polygonal cells, whereas in three-dimensional gels, only VE cadherin cells were able to form tubes. Empty vector cells grew in a fibroblast-like pattern and neither formed clusters nor tubes. Most importantly, whereas CD31 and empty vector cells grew on top of each other, formed polylayers and maintained cycling even after reaching confluence, VE cadherin cells strictly maintained a single layer of flattened cells and the numbers of cycling cells dramatically dropped after reaching a continuous monolayer.

CONCLUSION

The insertion of VE cadherin into ECV304 cells produces a cell type which mimics endothelial growth characteristics seen in vivo.

Vascular pathology in galactosialidosis

This article immunohistochemically and ultrastructurally examines a brain with galactosialidosis, focusing on the structure of blood vessel endothelium. Lysosomes were observed in the expanded cytoplasm of the endothelial cells, which were vacuolated by light microscopy. Immunoreactivity for CD31, one of the vascular cell adhesion molecules, was minimal to faint in endothelial cells with vacuolations. The loss of CD31 immunoreactivity and breakdown of vascular cell adhesion molecules in vacuolated endothelial cells seem to promote the development of brain infarctions. Moreover, diffuse and various degrees of axonal damage, most likely caused by vascular disorder in cerebral or cerebellar white matter, was reported using the amyloid precursor protein (APP) immunohistochemical method.

Nitric oxide synthase inhibition by N(G)-nitro-L-arginine methyl ester inhibits tumor-induced angiogenesis in mammary tumors

Using a murine breast cancer model, we earlier found a positive correlation between the expression of nitric oxide synthase (NOS) and tumor progression; treatment with inhibitors of NOS, N(G)-methyl-L-arginine (NMMA) and N(G)-nitro-L-arginine methyl ester (L-NAME), had antitumor and antimetastatic effects that were partly attributed to reduced tumor cell invasiveness. In the present study, we used a novel in vivo model of tumor angiogenesis using subcutaneous implants of tumor cells suspended in growth factor-reduced Matrigel to examine the angiogenic role of NO in a highly metastatic murine mammary adenocarcinoma cell line. This cell line, C3L5, expresses endothelial (e) NOS in vitro and in vivo, and inducible (i) NOS in vitro on stimulation with lipopolysaccharide and interferon-gamma. Female C3H/HeJ mice received subcutaneous implants of growth factor-reduced Matrigel inclusive of C3L5 cells on one side, and on the contralateral side, Matrigel alone; L-NAME and D-NAME (inactive enantiomer) were subsequently administered for 14 days using osmotic minipumps. Immediately after sacrifice, implants were removed and processed for immunolocalization of eNOS and iNOS proteins, and measurement of angiogenesis. Neovascularization was quantified in sections stained with Masson's trichrome or immunostained for the endothelial cell specific CD31 antigen. While most tumor cells and endothelial cells expressed immunoreactive eNOS protein, iNOS was localized in endothelial cells and some macrophages within the tumor-inclusive implants. Measurable angiogenesis occurred only in implants containing tumor cells. Irrespective of the method of quantification used, tumor-induced neovascularization was significantly reduced in L-NAME-treated mice relative to those treated with D-NAME. The quantity of stromal tissue was lower, but the quantity of necrotic tissue higher in L-NAME relative to D-NAME-treated animals. The total mass of viable tissue (ie, stroma and tumor cells) was lower in L-NAME relative to D-NAME-treated animals. These data suggest that NO is a key mediator of C3L5 tumor-induced angiogenesis, and that the antitumor effects of L-NAME are partly mediated by reduced tumor angiogenesis.

Thrombin-induced association of SHP-2 with multiple tyrosine-phosphorylated proteins in human platelets

SH2 domain containing phosphatase-2 (SHP-2) has an important regulatory role in a variety of cell types. However, little is known concerning its function in platelets. We show here that, in thrombin-stimulated human platelets, SHP-2 undergoes a time-dependent association with platelet endothelial cell adhesion molecule-1 (PECAM-1) and four low molecular weight phosphoproteins which are attenuated by the Src kinase inhibitor PP1. The low molecular weight proteins, which may be transmembrane proteins, are shown to bind exclusively to the N-terminal SH2 domain of SHP-2 and are therefore possible activators of the phosphatase. In addition, SHP-2 phosphatase activity is shown to be increased following thrombin stimulation or cross-linking of PECAM.

Enhanced eradication of local and distant tumors by genetically produced interleukin-12 and radiation

Ionizing radiation (IR) is frequently unsuccessful in the treatment of cancer because of local failure or distant metastases. The efficacy of systemically administered cytokines for cancer therapy is often limited by toxicity. We report that intratumoral injection of an adenoviral vector with interleukin-12 (IL-12) enhances local anti-tumor effects of irradiation (IR). We demonstrate that microscopic tumor growth at a distant site is suppressed following treatment of the primary tumor with adeno-murine IL-12 (Adm.IL-12). The results support a model in which the anti-angiogenic effects of IL-12 contribute to the local anti-tumor effects of radiation, while IL-12 induced immunity suppresses growth of microscopic tumors distant from the primary irradiated site. These data suggest that combining radiotherapy with IL-12 improves both local and distant tumor control compared to either treatment alone. Immunoradiotherapy may be employed in addition to or in place of current conventional therapies to increase local control and decrease distant tumor growth.

PECAM-1 (CD31) functions as a reservoir for and a modulator of tyrosine-phosphorylated beta-catenin

Catenins function as regulators of cellular signaling events in addition to their previously documented roles in adherens junction formation and function. Evidence to date suggests that beta and gamma catenins can act as signaling molecules, bind transcriptional factors and translocate to the nucleus. Beta- and gamma-catenin are also major substrates for protein tyrosine kinases, and tyrosine phosphorylation of junctional proteins is correlated with decreased adhesiveness. One way in which catenin functions are modulated is by dynamic incorporation into junctional complexes which controls, in part, the cytoplasmic levels of catenins. Here we show that: (1) vascular endothelial growth factor (VEGF) induces beta-catenin tyrosine phosphorylation in a time-, and dose-dependent manner and that VEGF receptors co-localize to areas of endothelial cell-cell contact in vitro and in vivo. (2) Platelet-endothelial cell adhesion molecule (PECAM)-1 can function as a reservoir for, and modulator of, tyrosine phosphorylated beta-catenin. (3) PECAM-1 can prevent beta-catenin nuclear translocation in transfected SW480 colon carcinoma cells. We suggest that PECAM-1 may play a role in modulating beta-catenin tyrosine phosphorylation levels, localization and signaling and by doing so, functions as an important modulator of the endothelium.

Thymidine phosphorylase activity and angiogenesis in gastric cancer

Angiogenesis has an important role in the growth and metastasis of solid tumors. Several angiogenic factors have been identified, one being platelet-derived endothelial cell growth factor (PD-ECGF), which is identical to thymidine phosphorylase (dThdPase). We investigated the activity of dThdPase in 84 samples of 42 human gastric cancers, by liquid chromatography. The dThdPase activity significantly correlated to the microvessel density assessed by immunostaining to CD-31 antigen (P<0.05). Expression of dThdPase has an important role in the promotion of angiogenesis in human gastric cancer.

An immunohistochemical analysis of angiogenesis in invasive breast cancer with correlations to clinicopathologic predictors

BACKGROUND

There is evidence that angiogenesis plays an important role in the biologic aggressiveness of breast carcinomas and might be used as a prognostic marker.

MATERIALS AND METHODS

In a series of 140 invasive mammary carcinomas, microvessels were highlighted immunohistochemically using two endothelial markers, factor VIII-related antigen (FVIIIRA) and CD31. Cases were divided into high and low microvessel density groups according to the highest number of microvessels found in each tumour's most vessel-dense part. The data was statistically analysed with regard to classic clinicopathologic prognosticators (i.e., histologic type and grade, nuclear grade, tumour size, stage, lymph node status and steroid receptor immunoexpression) by univariate and multivariate analysis.

RESULTS

Both markers' counts displayed just a weak skewness. Interestingly, CD31 angiogenesis grade was not influenced by any of the prognostic indicators assessed. FVIIIRA immunoreactivity was significantly affected only by nuclear grade (p = 0.041) in logistic regression analysis. Infiltrating lobular carcinomas frequently demonstrated higher FVIIIRA-positive microvessel densities than ductal invasive carcinomas, at least in the subgroup of patients with absence of nodal metastases and in those patients with highly oestrogen-dependent tumours.

CONCLUSIONS

The lack of relation between angiogenesis and either disease stage or lymph node metastasis indicates that this process may be necessary, but not sufficient alone for breast cancer spread.

Pathophysiologic basis of contrast enhancement in breast tumors

While the diagnostic benefits of gadolinium (Gd)-chelate contrast agents are firmly established in magnetic resonance imaging (MRI) of tumors, the pathophysiologic basis of the enhancement observed and its histopathologic correlate remained vague. Tumor angiogenesis is fundamental for growth and metastasis and also of interest in new therapeutic concepts. By correlative analysis of a) histology; b) vascular density (CD31); and c) vascular permeability (vascular permeability factor/vascular endothelial growth factor [VPF/VEGF]), we found a) significantly (P < 0.001) faster exchange rates in malignant compared with benign breast lesions; b) distinct differences in enhancement characteristics between the histologic types (invasive ductal carcinoma, invasive lobular carcinoma, and ductal carcinoma in situ); and c) dependence of enhancement kinetics on the VPF/VEGF expression. The pathophysiologic basis for the differences in contrast enhancement patterns of tumors detectable by MRI is mainly due to vascular permeability, which leads to more characteristic differences than vascular density. MRI is able to subclassify malignant breast tumors due to their different angiogenetic properties.

Three-dimensional structure of the micro-blood vessels in thyroid tumors analyzed by immunohistochemistry coupled with image analysis

The structure of micro-blood vessels, one of the most important factors influencing the tumor growth and tumor metastasis among histological types of thyroid malignancy, was analyzed immunochemically by staining tissues for platelet endothelial cell adhesion molecule-1 (PECAM-1). Human thyroid tumor tissue obtained at surgery, consisting of 18 cases of papillary carcinoma, 9 cases of follicular carcinoma, and 9 cases of anaplastic carcinoma were fixed in formalin solution, and paraffin sections were made. They were stained for PECAM-1 using the avidin-biotin complex (ABC) technique. The volume of the blood vessels and their three-dimensional (3D) structure were analyzed using an image analyzer. The volume ratios of blood vessels in thyroid tissues were: normal tissues, 1.10%; papillary carcinoma, 3.01%; follicular carcinoma, 8.13%; and anaplastic carcinoma, 0.91%. Ratios in malignant tumors were larger than in normal tissues, except for anaplastic carcinoma. The typical 3D structure of micro-blood vessels was histopathologically varied: branching tree-like blood vessels in papillary carcinomas; vessels of varied diameter surrounding follicle structure in follicular carcinomas; and simple and immature vessels in anaplastic carcinomas. The volume and 3D structure of micro-blood vessels in thyroid malignant tumors differed from those in normal tissues, and varied according to histological classification.

Evaluation of laser doppler flowmetry for the study of benign and malignant gastric blood flow in vivo

BACKGROUND

Tumour vascularisation is a determinant of the development of metastases.

AIMS

To measure blood flow in normal stomach and gastric adenocarcinomas by laser Doppler flowmetry and correlate blood flow with vascularisation after immunohistochemical staining of resected specimens for CD31 and von Willebrand factor.

PATIENTS

Twenty two undergoing resection for gastric adenocarcinoma and 10 undergoing cholecystectomy.

RESULTS

Mean (SD) gastric blood flow was 208 (35) perfusion units (PU) in patients undergoing cholecystectomy and 190 (75) PU in the undiseased part of the stomach in patients with gastric adenocarcinoma. Gastric blood flow was higher in the border of gastric adenocarcinomas (322 (120) PU, p<0.01 v normal stomach) but lower in the centre (74 (27) PU, p<0.01 v normal stomach and tumour border). Blood flow was higher in tumours staged T>/=3 than in those staged T<3. Blood vessel density in normal stomach was 41 (8) stained cells/field viewed and was 1. 9-3.4 times higher in gastric adenocarcinomas.

CONCLUSION

Laser Doppler flowmetry is a valuable tool for studying the pathophysiological alterations of malignant blood flow in the human stomach in vivo.

CD31 (PECAM-1) exists as a dimer and is heavily N-glycosylated

CD31 (PECAM-1) is a highly abundant cell surface glycoprotein expressed on hemopoietic and endothelial cells where it functions as a homophilic adhesion and signaling receptor. Since dimerization and appropriate glycosylation are important features in the regulation of cell surface interactions and signal transduction, we studied the pattern of glycosylation as well as the ability of CD31 to undergo dimerization, both in solution and when expressed on cell membranes. CD31 is heavily glycosylated, with an approximate carbohydrate content of 21%. Nineteen neutral and thirteen sialylated glycans were identified. Ultracentrifugation analysis showed that soluble recombinant CD31 exists in equilibrium between a monomer and a dimer with an approximate dissociation constant of 12.5 microM. Chemical cross-linking studies of both soluble and membrane-expressed CD31 confirmed that CD31 exists as a dimer. These studies suggest that, like E-cadherin, PECAM-dimerization is likely to play a role in CD31 adhesion and signaling.