Selectin GMP-140 (CD62; PADGEM) binds to sialosyl-Le(a) and sialosyl-Le(x), and sulfated glycans modulate this binding

Raft microdomain localized in the luminal leaflet of inner membrane complex of living Toxoplasma gondii

Membrane microdomains or rafts, sterol- and sphingolipid-rich microdomains in the plasma membrane have been studied extensively in mammalian cells. Recently, rafts were found to mediate virulence in a variety of parasites, including Toxoplasma gondii. However, it has been difficult to examine a two-dimensional distribution of lipid molecules at a nanometer scale. We tried to determine the distribution of glycosphingolipids GM1 and GM3, putative raft components in the T. gondii cell membrane in this study, using a rapid-frozen and freeze-fractured immuno-electron microscopy method. This method physically stabilized molecules in situ, to minimize the probability of artefactual disruption. Labeling of GM3, but not GM1, was observed in the exoplasmic (or luminal), but not the cytoplasmic, leaflet of the inner membrane complex (IMC) in T. gondii infected in human foreskin fibroblast-1 (HFF-1). No labeling was detected in any leaflet of the T. gondii plasma membrane. In contrast to HFF-1, T. gondii infected in mouse fibroblast (MF), labelings of both GM1 and GM3 were detected in the IMC luminal leaflet, although GM1's gold labeling density was very low. The same freeze-fracture EM method showed that both GM1 and GM3 were expressed in the exoplasmic leaflet of the MF plasma membrane. However, labeling of only GM3, but not GM1, was detected in the exoplasmic leaflet of the HFF-1 plasma membrane. These results suggest that GM1 or GM3, localized in the IMC, is obtained from the plasma membranes of infected host mammalian cells. Furthermore, the localization of microdomains or rafts in the luminal leaflets of the intracellular confined space IMC organelle of T. gondii suggests a novel characteristic of rafts.

A randomized clinical trial on the antitumoral effects of low molecular weight heparin in the treatment of esophageal cancer

The current treatment approaches for esophageal cancer are associated with poor survival, and there are ongoing efforts to find new and more effective therapeutic strategies. There are several reports on the antitumoral effects of low-molecular-weight heparins (LMWHs). We have assessed the possible survival benefit of LMWHs in esophageal malignancies. This was a randomized, single-blind, multicenter, Phase II clinical trial on nonmetastatic esophageal cancer candidate for neoadjuvant chemoradiotherapy. Patients were randomly assigned to the chemoradiotherapy-only arm or chemoradiotherapy plus enoxaparin arm using 1:1 allocation. Radiotherapy was delivered in 1.8-Gy daily fractions to a dose of 50.4 Gy in both groups. Paclitaxel 50 mg/m² and carboplatin (AUC 2) were administered weekly, concurrent with radiotherapy. In the intervention group, patients received enoxaparin (40 mg) and chemoradiation daily. 4-6 weeks after treatment, all patients underwent esophagectomy. After a median follow up of 7 months, estimated 1 year disease-free survival (DFS) in the intervention group was 78.9% and was 70% in the control groups ( p = 0.5). Toxicity from the experimental treatment was minimal, and there were no treatment-related deaths. A pathologically complete response in intervention and control group was 64.8% and 62.5%, respectively ( p = 0.9). There was a nonsignificant trend toward improved survival by the addition of enoxaparin to the concurrent chemoradiotherapy regimen. However, 1 y DFS of both groups were high as expected. A longer follow-up and a larger sample size are required.

Anti-tumoral effects of low molecular weight heparins: A focus on the treatment of esophageal cancer

Esophageal cancer is one of the most prevalent types of cancer globally. With current treatment options, the survival is poor, and there are ongoing efforts to find new and more efficient therapeutic approaches. There are several reports on the anti-tumoral effects of low-molecular-weight heparins (LMWH). We have assessed the possible survival benefits and underlying mechanisms of LMWHs in malignancies with a focus on esophageal cancer. We conclude that the effects of LMWHs on survival of cancer patients is probably due to a combination of direct anti-tumoral, anti-angiogenic, and immunomodulatory effects and indirect effects on the coagulation system.

Low molecular weight heparin and cancer survival: clinical trials and experimental mechanisms

INTRODUCTION

The relationship between cancer and thrombosis is complex, as the hemostatic system is inextricably linked to the mechanisms of cancer growth and metastasis. The coagulation system thus appears to be a site for oncogenic events and necessary for the survival and spread of malignant cells. Although several meta-analyses on the effectiveness of unfractionated heparin and low molecular weight heparin (LMWH) in the treatment of venous thromboembolism (VTE) have suggested a lower mortality risk in cancer patients receiving LMWH, this contention has not received general acceptance. In fact, there exist no sufficiently powered studies to date supporting the routine use of LMWH to improve cancer survival. Meanwhile, the molecular mechanism underlying the anti-neoplastic effect of LMWH which is independent of its anti-coagulant function is largely unexplored and is a topic of active investigation.

MATERIALS AND METHODS

In this communication, we aimed to review comprehensively evidences from clinical trials, meta-analysis as well as experimental molecular research and to identify future research areas of importance so as to stimulate future research on the potential anti-tumor action of LMWH.

CONCLUSION

Although benefit of LMWH on cancer patients' survival is controversial depending on the tumor type, cancer stage as well as LMWH type, it appears to be associated with a reduction in VTE and increased bleeding is minor and controllable; thus, randomized controlled trials targeting the survival benefit of certain specific LWMH are needed and justified, and more in-depth experimental researches are imperative to elucidate the anti-tumor effect of anticoagulants.

Self-recognition of high-mannose type glycans mediating adhesion of embryonal fibroblasts

High-mannose type N-linked glycan with 6 mannosyl residues, termed "M6Gn2", displayed clear binding to the same M6Gn2, conjugated with ceramide mimetic (cer-m) and incorporated in liposome, or coated on polystyrene plates. However, the conjugate of M6Gn2-cer-m did not interact with complex-type N-linked glycan with various structures having multiple GlcNAc termini, conjugated with cer-m. The following observations indicate that hamster embryonic fibroblast NIL-2 K cells display homotypic autoadhesion, mediated through the self-recognition capability of high-mannose type glycans expressed on these cells: (i) NIL-2 K cells display clear binding to lectins capable of binding to high-mannose type glycans (e.g., ConA), but not to other lectins capable of binding to other carbohydrates (e.g. GS-II). (ii) NIL-2 K cells adhere strongly to plates coated with M6Gn2-cer-m, but not to plates coated with complex-type N-linked glycans having multiple GlcNAc termini, conjugated with cer-m; (iii) degree of NIL-2 K cell adhesion to plates coated with M6Gn2-cer-m showed a clear dose-dependence on the amount of M6Gn2-cer-m; and (iv) the degree of NIL-2 K adhesion to plates coated with M6Gn2-cer-m was inhibited in a dose-dependent manner by α1,4-L-mannonolactone, the specific inhibitor in high-mannose type glycans addition. These data indicate that adhesion of NIL-2 K is mediated by self-aggregation of high mannose type glycan. Further studies are to be addressed on auto-adhesion of other types of cells based on self interaction of high mannose type glycans.

Multifarious roles of sialic acids in immunity

Sialic acids are a diverse family of monosaccharides widely expressed on all cell surfaces of vertebrates and so-called "higher" invertebrates, and on certain bacteria that interact with vertebrates. This overview surveys examples of biological roles of sialic acids in immunity, with emphasis on an evolutionary perspective. Given the breadth of the subject, the treatment of individual topics is brief. Subjects discussed include biophysical effects regulation of factor H; modulation of leukocyte trafficking via selectins; Siglecs in immune cell activation; sialic acids as ligands for microbes; impact of microbial and endogenous sialidases on immune cell responses; pathogen molecular mimicry of host sialic acids; Siglec recognition of sialylated pathogens; bacteriophage recognition of microbial sialic acids; polysialic acid modulation of immune cells; sialic acids as pathogen decoys or biological masks; modulation of immunity by sialic acid O-acetylation; sialic acids as antigens and xeno-autoantigens; antisialoglycan antibodies in reproductive incompatibility; and sialic-acid-based blood groups.

Pharmacotherapy to improve outcomes in vascular access surgery: a review of current treatment strategies

BACKGROUND

Renal failure is a major cause of morbidity in western Europe, with rising prevalence. Vascular access complications are the leading cause of morbidity among patients on haemodialysis. Considering the health care burden of vascular access failure, there is limited research dedicated to the topic.

METHODS

Randomised control trials of medications aimed at improving vascular access patency were identified using a medline search between January 1950 and January 2011.

RESULTS

Thirteen randomised trials were identified, investigating antiplatelets, anticoagulants and fish oil in preserving vascular access patency. Outcomes are presented and reviewed in conjunction with the underlying pathophysiological mechanisms of failure of vascular access.

DISCUSSION

Vascular access failure is a complex process. Most clinical trials so far have involved medications primarily aimed at preventing thrombosis. Other contributing pathways such as neointimal hyperplasia have not been investigated clinically. Improved outcomes may be seen by linking future therapies to these pathways.

Directing stem cell trafficking via GPS

The success of stem-cell-based regenerative therapeutics critically hinges on delivering relevant stem/progenitor cells to sites of tissue injury. To achieve adequate parenchymal infiltration following intravascular administration, it is first necessary that circulating cells bind to target tissue endothelium with sufficient strength to overcome the prevailing forces of hemodynamic shear. The principal mediators of these shear-resistant binding interactions consist of a family of C-type lectins known as "selectins" that bind discrete sialofucosylated glycans on their respective ligands. One member of this family, E-selectin, is an endothelial molecule that is inducibly expressed on postcapillary venules at all sites of tissue injury, but is also constitutively expressed on the luminal surface of bone marrow and dermal microvascular endothelium. Most stem/progenitor cells express high levels of CD44, and, in particular, human hematopoietic stem cells express a specialized sialofucosylated glycoform of CD44 known as "hematopoietic cell E-/L-selectin ligand" (HCELL) that functions as a potent E-selectin ligand. This chapter describes a method called "glycosyltransferase-programmed stereosubstitution" (GPS) for custom-modifying CD44 glycans to create HCELL on the surface of living cells that natively lack HCELL. Ex vivo glycan engineering of HCELL via GPS licenses trafficking of infused cells to endothelial beds that express E-selectin, thereby enabling efficient vascular delivery of stem/progenitor cells to sites where they are needed.

Glycosyltransferase-programmed stereosubstitution (GPS) to create HCELL: engineering a roadmap for cell migration

During evolution of the vertebrate cardiovascular system, the vast endothelial surface area associated with branching vascular networks mandated the development of molecular processes to efficiently and specifically recruit circulating sentinel host defense cells and tissue repair cells at localized sites of inflammation/tissue injury. The forces engendered by high-velocity blood flow commensurately required the evolution of specialized cell surface molecules capable of mediating shear-resistant endothelial adhesive interactions, thus literally capturing relevant cells from the blood stream onto the target endothelial surface and permitting subsequent extravasation. The principal effectors of these shear-resistant binding interactions comprise a family of C-type lectins known as 'selectins' that bind discrete sialofucosylated glycans on their respective ligands. This review explains the 'intelligent design' of requisite reagents to convert native CD44 into the sialofucosylated glycoform known as hematopoietic cell E-/L-selectin ligand (HCELL), the most potent E-selectin counter-receptor expressed on human cells, and will describe how ex vivo glycan engineering of HCELL expression may open the 'avenues' for the efficient vascular delivery of cells for a variety of cell therapies.

Adenosine receptor-mediated adhesion of endothelial progenitors to cardiac microvascular endothelial cells

Intracoronary delivery of endothelial progenitor cells (EPCs) is an emerging concept for the treatment of cardiovascular disease. Enhancement of EPC adhesion to vascular endothelium could improve cell retention within targeted organs. Because extracellular adenosine is elevated at sites of ischemia and stimulates neovascularization, we examined the potential role of adenosine in augmenting EPC retention to cardiac microvascular endothelium. Stimulation of adenosine receptors in murine embryonic EPCs (eEPCs) and cardiac endothelial cells (cECs) rapidly, within minutes, increased eEPC adhesion to cECs under static and flow conditions. Similarly, adhesion of human adult culture-expanded EPCs to human cECs was increased by stimulation of adenosine receptors. Furthermore, adenosine increased eEPC retention in isolated mouse hearts perfused with eEPCs. We determined that eEPCs and cECs preferentially express functional A1 and A2B adenosine receptor subtypes, respectively, and that both subtypes are involved in the regulation of eEPC adhesion to cECs. We documented that the interaction between P-selectin and its ligand (P-selectin glycoprotein ligand-1) plays a role in adenosine-dependent eEPC adhesion to cECs and that stimulation of adenosine receptors in cECs induces rapid cell surface expression of P-selectin. Our results suggest a role for adenosine in vasculogenesis and its potential use to stimulate engraftment in cell-based therapies.

Glycan-based interactions involving vertebrate sialic-acid-recognizing proteins

All cells in nature are covered by a dense and complex array of carbohydrates. Given their prominence on cell surfaces, it is not surprising that these glycans mediate and/or modulate many cellular interactions. Proteins that bind sialic acid, a sugar that is found on the surface of the cell and on secreted proteins in vertebrates, are involved in a broad range of biological processes, including intercellular adhesion, signalling and microbial attachment. Studying the roles of such proteins in vertebrates has improved our understanding of normal physiology, disease and human evolution.

Comparison of changes in circulating platelet-derived microparticles and platelet surface P-selectin expression after coronary stent implantation

Platelet-derived microparticles (PDMPs) are released from activated platelets and may participate in the inflammatory process in response to vessel wall injury. This study was designed to compare the clinical significance of circulating PDMPs with that of P-selectin on the platelet membrane surface. In 20 patients with stable angina undergoing coronary stent implantation, circulating PDMPs were serially measured by enzyme-linked immunosorbent assay, and P-selectin expression on the surface of platelets was simultaneously analyzed by flow cytometry. PDMPs increased 24-48 h after coronary stenting in the coronary sinus (8.7 +/- 8.9 to 31.8 +/- 19.8 U/ml, P < 0.001) with a maximum at 48 h. In contrast, the mean channel fluorescence intensity for P-selectin increased 15 min after coronary stenting in the coronary sinus (19.5 +/- 5.6 to 25.2 +/- 7.5, P < 0.01) and remained elevated for 48 h; the changes were less striking in peripheral blood. The relative increase in PDMPs was not correlated with the increase in P-selectin expression at 15 min or 24 h after coronary stenting, but was correlated at 48 h (R = 0.48, P < 0.05). Both circulating PDMPs and P-selectin expression were enhanced in association with stent-induced platelet activation; however, the time course of changes in these two platelet activation markers was different. Therefore, the clinical relevance of circulating PDMPs may differ from that of P-selectin expression on the platelet membrane surface.

Role of P-Selectin in Platelet Sequestration in Pulmonary Capillaries during Endotoxemia

BACKGROUND

There is growing evidence that platelets accumulate in the lung and contribute to the pathogenesis of acute lung injury during endotoxemia. The aims of the present study were to localize platelet sequestration in the pulmonary microcirculation and to investigate the role of P-selectin as a molecular mechanism of platelet endothelial cell interaction.

METHODS

We used in vivo fluorescence microscopy to quantify the kinetics of fluorescently labeled erythrocytes and platelets in alveolar capillary networks in rabbit lungs.

RESULTS

Six hours after onset of endotoxin infusion we observed a massive rolling along and firm adherence of platelets to lung capillary endothelial cells whereas under control conditions no platelet sequestration was detected. P-selectin was expressed on the surface of separated platelets which were incubated with endotoxin and in lung tissue. Pretreatment of platelets with fucoidin, a P-selectin antagonist, significantly attenuated the endotoxin-induced platelet rolling and adherence. In contrast, intravenous infusion of fucoidin in endotoxin-treated rabbits did not inhibit platelet sequestration in pulmonary capillaries.

CONCLUSION

We conclude that platelets accumulate in alveolar capillaries following endotoxemia. P-selectin expressed on the surface of platelets seems to play an important role in mediating this platelet-endothelial cell interaction.

Cellular, molecular and immunological mechanisms in the pathophysiology of vein graft intimal hyperplasia

Coronary artery disease, leading to myocardial infarction and ischaemia, affects millions of persons and is one of the leading causes of morbidity and mortality worldwide. Invasive techniques such as coronary artery bypass grafting are used to alleviate the sequelae of arterial occlusion. Unfortunately, restenosis or occlusion of the grafted conduit occurs over a time frame of months to years with a gradual reduction in patency, especially in vein grafts. The events leading to intimal hyperplasia (IH) formation involve numerous cellular and molecular components. Various cellular elements of the vessel wall are involved as are leucocyte-endothelial interactions that trigger the coagulation cascade leading to localized thrombus formation. Subsequent phenotypic modification of the medial smooth muscle cells and their intimal migration is the basis of the lesion formation that is thought to be propagated by an immune-mediated reaction. Despite intense scrutiny, the pathophysiology of IH remains an enigma. Although several growth factors, cytokines and numerous other biomolecules have been implicated and their relationship to prohyperplasia pathways such as the phosphatidyl-inositol 3-kinase (PI3K)-Akt pathway has been established, many pieces of the puzzle are still missing. An in-depth understanding of early vein graft adaptation and progression is necessary to improve the long-term prognosis and develop more effective therapeutic measures. In this review, we have critically evaluated and summarized the literature to elucidate and interlink the numerous established and emerging factors that play a key role in the development of IH leading to vein graft restenosis.

Chemically modified heparin inhibits the in vitro adhesion of nonsmall cell lung cancer cells to P-selectin

PURPOSE

Several independent studies have indicated that tumor metastasis can be inhibited by chemically modified heparin with low anticoagulant activity in the different tumor models. The mechanism of inhibition by the heparin derivatives in part accounts for the interference of tumor cell-platelet interaction mediated by P-selectin.

METHODS

In the present study, we demonstrated that both heparin and chemically modified heparins inhibited the adhesion of nonsmall cell lung cancer (NSCLC) cells to P-selectin under static or flow conditions in vitro.

RESULTS

Flow cytometric analysis with the heparan sulfate-specific monoclonal antibody revealed that both NSCLC cells express heparan sulfate-like proteoglycans. Furthermore, heparinase treatment impaired P-selectin binding, indicating that heparan sulfate-like proteoglycans on the tumor cell surface are implicated in the adhesion of NSCLC cells to P-selectin.

CONCLUSIONS

These findings suggest that some chemically modified heparins with low anticoagulant activity may deserve further testing in the experimental NSCLC treatment protocols.

Low-molecular-weight fucoidan enhances the proangiogenic phenotype of endothelial progenitor cells

Endothelial progenitor cell (EPC) transplantation is a potential means of inducing neovascularization in vivo. However, the number of circulating EPC is relatively small, it may thus be necessary to enhance their proangiogenic properties ex vivo prior to injection in vivo. Fucoidan has previously been shown to potentiate in vitro tube formation by mature endothelial cells in the presence of basic fibroblast growth factor (FGF-2). We therefore examined whether fucoidan, alone or combined with FGF-2, could increase EPC proangiogenic potency in vitro. EPC exposure to 10 microg/ml fucoidan induced a proangiogenic phenotype, including cell proliferation (p < 0.01) and migration (p < 0.01); moreover, differentiation into vascular cords occurred in the presence of FGF-2 (p < 0.01). This latter effect correlated with upregulation of the cell-surface #alpha6 integrin subunit of the laminin receptor (p < 0.05). Compared to untreated HUVEC, untreated EPC #alpha6 expression and adhesion to laminin were enhanced two-fold. Fucoidan treatment further enhanced HUVEC but not EPC adhesion to laminin. These results show that fucoidan enhances the proangiogenic properties of EPC and suggest that ex vivo fucoidan preconditioning of EPC might lead to increased neovascularization when injected into ischemic tissues.

L-selectin: adhesion, signalling and its importance in pathologic posttraumatic endotoxemia and non-septic inflammation

The leucocyte expressed surface-bound L-selectin belongs to the selectin family of adhesion molecules. It exhibits adhesive as well as signalling functions. Mainly, it is of importance in lymphocyte homing and in the extravasation of leucocytes into the surrounding tissue during inflammation. Acting in the initial step of the cell adhesion cascade, L-selectin is responsible for the rolling of leucocytes on endothelial layers. Therefore, L-selectin is thought to be an adequate target for pharmacological interventions. Beneath the discussion of the molecules' general features like molecule structure and its regulation, the review focuses firstly on L-selectin in the context of posttraumatic inflammatory disorders, and secondly on the importance of L-selectin specific signalling events.

Molecular and cellular basis of restenosis after percutaneous coronary intervention: the intertwining roles of platelets, leukocytes, and the coagulation-fibrinolysis system

The major limitation of percutaneous coronary intervention (PCI) is restenosis. Restenosis is considered to be an overreaction of the natural healing process after traumatic balloon dilatation. An elaborate web of cellular and molecular responses, including the interaction of platelets, leukocytes, and the coagulation-fibrinolysis system, as well as the secretion of various growth factors and pro-inflammatory cytokines, contributes to neointimal hyperplasia and the development of restenosis. Moreover, platelet and neutrophil activation after stenting appears to be different from that after balloon angioplasty alone. Pharmacotherapy targeting the cell-to-cell interaction between platelets and neutrophils may potentially offer an effective treatment strategy against restenosis after PCI.

Inhibition of P-selectin-mediated cell adhesion by a sulfated derivative of sialic acid

P-selectin, a carbohydrate-binding cell adhesion molecule expressed on activated endothelial cells and platelets, plays a key role in the recruitment of leukocytes to inflammatory and hemorrhagic sites. It simultaneously recognizes a sialic acid-containing carbohydrate chain and the sulfated tyrosine residues of a specific counter-receptor expressed on the leukocyte surface. We examined the inhibitory effects of a synthetic sulfated derivative of sialic acid (NMSO3) on P-selectin-mediated cell adhesion and found the following: (1) P-selectin/IgG chimera bound to immobilized NMSO3. (2) The binding of P-selectin/IgG chimera to purified P-selectin glycoprotein ligand-1 was inhibited by soluble NMSO3. (3) The adhesion of HL60 cells to P-selectin-expressing CHO cells was inhibited by NMSO3. (4) NMSO3 inhibited P-selectin-induced tumor necrosis factor-alpha production in monocytes and activated platelet-induced generation of reactive oxygen species in neutrophils. In conclusion, NMSO3 acts as a specific inhibitor for P-selectin-mediated cell adhesion and for adhesion-dependent leukocyte activation.

The effect of adhesion molecule blockade on pulmonary reperfusion injury

BACKGROUND

Selectins are the molecules involved in the initial adhesion of the activated neutrophil on pulmonary endothelium. We investigated the efficacy of selectin blockade in a selective (monoclonal antibody RMP-1) and nonselective (Fucoidin) manner in pulmonary reperfusion injury.

METHODS

Groups of six rat lungs were flushed with University of Wisconsin solution then stored at 4 degrees C for 4 hours. They then underwent sanguinous reperfusion for 30 minutes during which functional measures (gas exchange, pulmonary artery pressure, and airway pressure) of lung performance were made. After reperfusion we estimated their capillary filtration coefficient (Kfc units g/cm water/minute/g wet lung tissue) using a gravimetric technique. Four groups were studied: group I had no reperfusion, group II had 30 minutes of reperfusion, group III had infusion of 20 mg/kg Fucoidin before reperfusion, and group IV had infusion of 20 microg/mL RMP-1 before reperfusion.

RESULTS

Reperfusion injury was found between groups I and II by an increase in capillary filtration coefficient (1.048 +/- 0.316 to 3.063 +/- 0.466, p < 0.01). Groups III and IV had a significantly lower Kfc than group II (0.967 +/- 0.134 and 1.205 +/- 0.164, respectively, p < 0.01). There was no significant functional difference between groups II, III, and IV.

CONCLUSIONS

Reperfusion-induced hyperpermeability was ameliorated by selective (RMP-1) and nonselective (Fucoidin) selectin blockade.

Synthesis of a set of di- and tri-sulfated galabioses

Among cell-adhesion molecules, L-selectin recognizes sulfated sLe(x) with relatively low affinity. Here, we aimed at artificial mimics by synthesizing a set of di- and tri-sulfated galabioses, which may surpass the affinity of sulfated sLe(x). As a strategy to obtain 3',6',6-tri-O-sulfogalabioses, regioselective reductive cleavage of 4,6- and 4',6'-di-O-benzylidenegalabioses was employed. Two suitably protected galactose precursors were conjugated to yield alpha and beta anomers (48 and 18%, respectively) by using a pentenyl galactoside donor and iodinium di-sym-collidine perchlorate as the catalyst. For synthesizing the 3',6-di-O-sulfogalabiose, however, a trichloroacetimidate donor was superior (52%) to the pentenyl one (30%).

Tyrosine sulfation enhances but is not required for PSGL-1 rolling adhesion on P-selectin

P-selectin glycoprotein ligand-1 (PSGL-1) is a large (240 kDa) glycoprotein found on the surface of nearly all leukocytes. The mature molecule is decorated with multiple N- and O-linked glycans and displays copies of the tetrasaccharide sialyl-Lewis(x) (sLe(X)), as well as a cluster of three tyrosine sulfate (tyr-SO(3)) groups near the N-terminus of the processed protein. Previous studies have suggested that PSGL-1 needs to be tyrosine-sulfated, in addition to glycosylated with sLe(X), to successfully interact with P-selectin. To better understand how biochemical features of the PSGL-1 ligand are related to its adhesion phenotype, we have measured the dynamics of adhesion under flow of a series of well-defined PSGL-1 variants that differ in their biochemical modification, to both P- and E-selectin-coated substrates. These variants are distinct PSGL-1 peptides: one that possesses sLe(X) in conjunction with three N-terminal tyr-SO(3) groups (SGP3), one that possesses sLe(X) without tyrosine sulfation (GP1), and one that lacks sLe(X) but has three N-terminal tyr-SO(3) groups (SP3). Although all peptides expressing sLe(X), tyr-SO(3), or both supported some form of rolling adhesion on P-selectin, only peptides expressing sLe(X) groups showed rolling adhesion on E-selectin. On P-selectin, the PSGL-1 peptides demonstrated a decreasing strength of adhesion in the following order: SGP3 > GP1 > SP3. Robust, rolling adhesion on P-selectin was mediated by the GP1 peptide, despite its lack of tyrosine sulfation. However, the addition of tyrosine sulfation to glycosylated peptides (SGP3) creates a super ligand for P-selectin that supports slower rolling adhesion at all shear rates and supports rolling adhesion at much higher shear rates. Tyrosine sulfation has no similar effect on PSGL-1 rolling on E-selectin. Such functional distinctions in rolling dynamics are uniquely realized with a cell-free system, which permits precise, unambiguous identification of the functional activity of adhesive ligands. These findings are consistent with structural and functional characterizations of the interactions between these peptides and E- and P-selectin published recently.

Comparison of activation process of platelets and neutrophils after coronary stent implantation versus balloon angioplasty for stable angina pectoris

The pathophysiologic features of stent-induced cellular responses of platelets and leukocytes have not been established. This study was designed to clinically investigate the activation of platelets and neutrophils after coronary stenting and to identify its effects on the long-term results of coronary stents. Forty-eight consecutive patients with left anterior descending coronary artery disease indicating coronary intervention were randomly assigned to either a balloon angioplasty group or a coronary stent group. Flow cytometric analysis demonstrated that the transcardiac gradient (the value of coronary sinus blood minus the value of peripheral blood) of platelet surface expression of CD62P (p < 0.001) and CD63 (p < 0.01) increased immediately after coronary stenting, but increased less significantly immediately after balloon angioplasty (CD62P, p < 0.01; CD63, p < 0.05). These increases were persistently observed after coronary stenting but transiently after balloon angioplasty alone during a 48-hour observation period after the procedures. The gradient for neutrophil surface expression of CD11b increased, and that of CD62 L decreased 48 hours after coronary stenting (CD11b, p < 0.001; CD62 L, p < 0.05), but these changes showed less significance 48 hours after balloon angioplasty alone (CD11b, p < 0.05; CD62 L, p = NS). The gradients 48 hours after the procedures for both CD62P (r = 0.39, p < 0.05) and CD11b (r = 0.44, p < 0.01) were independently correlated with the late loss in the stent group, whereas the correlation was seen only for CD11b (r = 0.38, p < 0.05) in the balloon angioplasty group. Both platelet and neutrophil activation was greater after coronary stenting than after balloon angioplasty. Cellular interactions between platelets and neutrophils may be related to the progression of neointimal proliferation leading to restenosis after coronary stent implantation.

Sialyl Lewis(x)-mediated, PSGL-1-independent rolling adhesion on P-selectin

Selectin-mediated cell adhesion is an essential component of the inflammatory response. In an attempt to unambiguously identify molecular features of ligands that are necessary to support rolling adhesion on P-selectin, we have used a reconstituted ("cell-free") system in which ligand-coated beads are perfused over soluble P-selectin surfaces. We find that beads coated with the saccharides sialyl Lewis(x) (sLe(x)), sialyl Lewis(a) (sLe(a)), and sulfated Lewis(x) (HSO(3)Le(x) support rolling adhesion on P-selectin surfaces. Although it has been suggested that glycosylation and sulfation of P-selectin glycoprotein ligand-1 (PSGL-1) is required for high-affinity binding and rolling on P-selectin, our findings indicate that sulfation of N-terminal tyrosine residues is not required for binding or rolling. However, beads coated with a tyrosine-sulfated, sLe(x)-modified, PSGL-1-Fc chimera support slower rolling on P-selectin than beads coated with sLe(x) alone, suggesting that sulfation improves rolling adhesion by modulating binding to P-selectin. In addition, we find it is not necessary that P-selectin carbohydrate ligands be multivalent for robust rolling to occur. Our results demonstrate that beads coated with monovalent sLe(x), exhibiting a more sparse distribution of carbohydrate than a similar amount of the multivalent form, are sufficient to yield rolling adhesion. The relative abilities of various ligands to support rolling on P-selectin are quantitatively examined among themselves and in comparison to human neutrophils. Using stop-time distributions, rolling dynamics at video frame rate resolution, and the average and variance of the rolling velocity, we find that P-selectin ligands display the following quantitative trend, in order of decreasing ability to support rolling adhesion on P-selectin: PSGL-1-Fc > sLe(a) approximately sLe(x) > HSO(3)Le(x).

Enhanced expression of P-selectin (CD62P) by endothelial cells seeded onto synthetic arterial prostheses (PET, Dacron) is correlated with leukocyte interactions

This study evaluated the expression by seeded endothelial cells (S-EC) of P-selectin (CD62P/GMP-140/PADGEM), an adhesion molecule implicated in endothelial-leukocyte interactions. Endothelial cells were seeded onto knitted polyethylene terephthalate (PET, Dacron(R)) prostheses and compared with control endothelial cells (C-EC) cultured in flasks to the same stage. Using flow cytometry techniques, we observed that CD62P expression by PET S-EC was significantly increased (p<0.05) compared to C-EC. Moreover, RT PCR techniques showed that the CD62P RNA level was higher on S-ECs compared to C-ECs. Following adhesion assays, increased polymorphonuclear neutrophil (PMN) attachment to the PET-seeded prostheses as compared to control cultures (p<0.001) was observed. PMN adherence was enhanced by TNFalpha activation. PMN adhesion was decreased significantly (p<0.001) after the incubation of resting EC or TNFalpha-activated EC-seeded prostheses with a blocking monoclonal antibody (LYP20) directed against the P-selectin. Such results suggest that: (1) PET prosthetic material may induce the expression of P-selectin by S-EC; (2) seeding conditions provoke an increase in PMN adhesion; (3) increased PMN interactions with seeded PET material is partially dependent upon P-selectin expression by the S-EC.

Cilostazol inhibits the expression of activation-dependent membrane surface glycoprotein on the surface of platelets stimulated in vitro

Cilostazol is a newly developed antiplatelet drug that has been widely applied for clinical use. Its antiplatelet action appears to be mainly related to inhibition of intracellular phosphodiesterase activity. Our study was designed to investigate inhibitory effects of cilostazol on the expression of activation-dependent platelet membrane surface glycoproteins. We performed flow cytometric analysis using monoclonal antibodies, PAC-1 (antibody against activation dependent epitope of GPIIb/IIIa), anti-CD62P (P-selectin), and anti-CD63. In vitro ADP stimulation of platelets taken from seven healthy volunteers produced significant increases in the mean channel fluorescence intensities (MFI) for PAC-1 (148% increase) and CD62P (43% increase) but did not increase in that for CD63. The enhanced MFI for CD62P was suppressed to the control level by pretreatment with 1 microM (88% suppression), 3 microM (94% suppression), and 10 microM (95% suppression) of cilostazol. However, that of PAC-1 was suppressed to a lesser degree (12, 16, and 21% suppressions, respectively). Cilostazol may inhibit P-selectin release from alpha-granule, rather than activation-dependent conformational change of GPIIb/IIIa in platelets. Cilostazol inhibits cellular interaction among platelets, leukocytes, and vascular endothelial cells mediated by P-selectin.

Actions of heparin that may affect the malignant process

BACKGROUND

Heparin has many actions that may affect the malignant process, especially metastasis.

METHODS

The author conducted an extensive review of the available medical literature about heparin activity that may apply to important factors involved in the malignant process.

RESULTS

Thrombin is generated by tumors, and the resultant fibrin formation impedes natural killer cell activity. Microthrombi arrest tumor cells in capillaries. Heparin prevents the formation of thrombin and neutralizes its activity. Angiogenesis has an important role in metastasis; heparin minimizes angiogenesis via the inhibition of vascular endothelial growth factor, tissue factor, and platelet activating factor. It decreases tumor cell adhesion to vascular endothelium as it inhibits selectin and chemokine actions, and it also decreases the replication and activity of some oncogenic viruses. Matrix metalloproteinases, serine proteases, and heparanases have an important role in metastasis. Heparin decreases their activation and limits their effects. It competitively inhibits tumor cell attachment to heparan sulfate proteoglycans. It blocks the oncogenic action of ornithine decarboxylase and enhances the antineoplastic effect of transforming growth factor-beta. Heparin inhibits activator protein-1, which is the nuclear target of many oncogenic signal transduction pathways, and it potently inhibits casein kinase II, which has carcinogenic activity. Platelet-derived growth factor, which has oncogenic effects, is also inhibited by heparin, as are reverse transcriptase, telomerase, and topoisomerase prooncogenic actions.

CONCLUSIONS

These various heparin actions justify clinical investigation of its possible beneficial effect on malignant disease.

Quantitative analysis of mRNA encoding MUC1, MUC2, and MUC5AC genes: a correlation between specific mucin gene expression and sialomucin expression in non-small cell lung cancer

The expression of mucins is important for tumor invasiveness and metastasis. In our previous report (Am. J. Respir. Crit. Care Med. 1997; 155:1419-1427), non-small cell lung cancers bearing sialomucin expression tended to relapse earlier than those without sialomucin. However, it remained unclear whether the expression of sialomucin in lung cancer is caused by an abnormal glycosylation process or by the expression of a specific mucin gene product. To address this problem, we established a modified quantitative competitive polymerase chain reaction (QC-PCR) analysis. RNA internal standards of MUC1, MUC2, and MUC5AC non-tandem repeat sequences were constructed, and known copy numbers of mucin RNA internal standards were introduced into reverse transcription-polymerase chain reactions (RT-PCR) for each mucin gene in order to compete with native mucin gene RNA during the reaction. The RNA of Gbeta-like gene (a housekeeping gene) was used as internal control for the RNA analysis. Twenty-five lung cancer tissues (13 adenocarcinomas and 12 squamous cell carcinomas) were used for analysis. Mann-Whitney rank sum test was applied to compare the expression amounts of different mucin genes in tissues. The results revealed that adenocarcinoma expressed higher amounts of MUC5AC gene than did squamous cell carcinoma (P = 0.03). The expression amount of MUC5AC correlated positively with the expression status of sialomucin (P = 0.012). Further studies are anticipated to elucidate the underlying mechanism contributing to this phenomenon.

GM3-enriched microdomain involved in cell adhesion and signal transduction through carbohydrate-carbohydrate interaction in mouse melanoma B16 cells

Mouse melanoma B16 cells are characterized by the predominant presence of ganglioside GM3 and adhere to lactosylceramide- or Gg3-coated plates through interaction of GM3 with lactosylceramide or Gg3, whereby not only adhesion but also spreading and enhancement of cell motility occur (Kojima, N., Hakomori, S. (1991) J. Biol. Chem. 266, 17552-17558). We now report that the adhesion process is based essentially on a glycosphingolipid-enriched microdomain (GEM) at the B16 cell surface, since >90% of GM3 present in the original cells is found in GEM, and GEM is also enriched in several signal transducer molecules, e.g. c-Src, Ras, Rho, and focal adhesion kinase (FAK). GEM was isolated as a low density membranous fraction by homogenization of B16 cells in lysis buffer under two different conditions (i.e. buffer containing 1% Triton X-100, or hypertonic sodium carbonate without detergent), followed by sucrose density gradient centrifugation. A close association of GM3 with c-Src, Rho, and FAK was indicated by co-immunoprecipitation of GM3 present in GEM by anti-GM3 monoclonal antibody DH2, followed by Western blotting with antibodies directed to these transducer molecules. The following data indicate that GEM is a structural and functional unit for initiation of GM3-dependent cell adhesion coupled with signal transduction. 1) Tyrosine phosphorylation in FAK was greatly enhanced in B16 cells adhered to Gg3-coated plates but was minimal in cells adhered to GM3-coated, GlcCer-coated, or noncoated plates. 2) GTP loading on Ras and Rho increased significantly when cells were adhered to Gg3-coated plates, compared with GM3-coated, GlcCer-coated, or noncoated plates. Since Ras and Rho are closely associated with GM3 in GEM, cell adhesion/stimulation through GM3 in GEM may induce activation of Ras and Rho through enhanced GTP binding.

Differential interactions of heparin and heparan sulfate glycosaminoglycans with the selectins. Implications for the use of unfractionated and low molecular weight heparins as therapeutic agents

The selectins are calcium-dependent C-type lectins that bind certain sialylated, fucosylated, sulfated glycoprotein ligands. L-selectin also recognizes endothelial proteoglycans in a calcium-dependent manner, via heparan sulfate (HS) glycosaminoglycan chains enriched in unsubstituted glucosamine units. We now show that these HS chains can also bind P-selectin, but not E-selectin. However, while L-selectin binding requires micromolar levels of free calcium, P-selectin recognition is largely divalent cation-independent. Despite this, HS chains bound to P-selectin are eluted by ethylenediamine tetraacetic acid (EDTA), but only at high concentrations. Porcine intestinal mucosal (mast cell-derived) heparin (PIM-heparin) shows similar properties, with no binding to E-selectin, calcium-dependent binding of a subfraction to L-selectin and to P-selectin, and calcium-independent binding of a larger fraction to P-selectin, the latter being disrupted by high EDTA concentrations. Analysis of defined heparin fragment pools shows a size dependence for interaction, with tetradecasaccharides showing easily detectable binding to L- and P-selectin affinity columns. L-selectin binding fragments include more heavily sulfated and epimerized regions and, as with the endothelial HS chains, they are enriched in free amino groups. The P-selectin binding component includes this fraction as well as some less highly modified regions. Thus, endothelium-derived HS chains and mast cell-derived heparins could play a role in modulating the biology of selectins in vivo. Notably, P- and L-selectin binding to sialyl-Lewisx and to HL-60 cells (which are known to carry the native ligand PSGL-1) is inhibited by unfractionated pharmaceutical heparin preparations at concentrations 12-50-fold lower than those recommended for effective anticoagulation in vivo. In contrast, two low molecular weight heparins currently considered as clinical replacements for unfractionated heparin are much poorer inhibitors. Thus, patients undergoing heparin therapy for other reasons may be experiencing clinically significant inhibition of L- and P-selectin function, and the current switchover to low-molecular weight heparins may come at some loss of this effect. Low-dose unfractionated heparin should be investigated as a treatment option for acute and chronic diseases in which P- and L-selectin play pathological roles.

Synthesis of a set of highly clustered monosulfated galactopyranosides

There are several biological events that are known to involve certain sulfated saccharides. In many such cases, however, clustered ligands have been shown to be more effective than monovalent saccharides. A set of 6-aminohexyl glycosides of 2,3,4 or 6-monosulfated galactose have been synthesized and linked to polyglutamic acid. Because of the bulky aglycon employed, the 2-OH group of the key compound, 6-benzyloxycarbonylaminohexyl 4,6-O-benzylidene-beta-D-galactopyranoside was markedly less reactive than 3-OH. Thus, site-specific acetylation of 3-OH was readily carried out to obtain 2-O-sulfated galactosides, and even the direct sulfation of 3-OH afforded the 3-sulfate in a reasonable yield. On the other hand, the key compound was unexpectedly resistant to 2,3-O-dibenzylation or 2,3-O-dibenzoylation, both of which were meant for regioselective cleavage of 4,6-benzylidene to obtain the 4-sulfate.

Selection of tumor antigens as targets for immune attack using immunohistochemistry: II. Blood group-related antigens

Blood group-related antigens have been attractive targets for immunotherapy of cancer since their initial identification as cancer-related antigens. However, available information on the relative expression of most of these antigens on human malignant and normal tissues has been insufficient for selecting optimal antigens and tumors for immune attack. In this study, the distribution of the blood group-related antigens TF, Tn, sTn, Le(a), sialyl Le(a), Le(b), Le(x), sialyl Le(x), polyfucosyl Le(x) and Le(y) on 13 types of cancer and 16 normal tissues was compared. Our results show that sTn is strongly expressed on cancers of breast, colon, stomach, ovary, prostate and uterus; Tn on prostate cancer; TF on cancers of breast, colon, ovary, prostate and uterus; Le(y) on the cancers of colon, lung, pancreas and ovary; Le(a) and Le(x) on gastric cancer; and sialyl Le(a) and sialyl Le(x) on colon cancer. The complete absence of these antigens on cancers of neuroectodermal or mesodermal origin including melanoma, sarcoma, neuroblastoma and B cell lymphoma is as striking as their widespread presence on tumors of epithelial origin. Normal tissues were also tested. Tn and Le(b) were only detected on gastric and ovarian epithelia; sTn on Leydig cells of testis in addition to gastric and ovarian epithelia; Le(x) and sialyl Le(x) on polymorphonuclear leukocytes; and TF, Le(a), sialyl Le(a), Le(x), sialyl Le(x), polyfucosyl Le(x) and Le(y) on epithelia from a variety of tissues.

High expression of uridine diphosphate-galactose: Lc3Cer beta 1-3 galactosyltransferase in human uterine endometrial cancer-derived cells as measured by enzyme-linked immunosorbent assay and thin-layer chromatography-immunostaining

We have developed a new procedure for the selective determination of beta 1-3 and beta 1-4 galactosyltransferases with Lc3Cer as the substrate and the microsomes of fetal and adult porcine livers as the enzyme sources. This method was based on the detection of such products as Lc4Cer for beta 1-3 galactosyltransferase (beta 1-3GT) and nLc4Cer for beta 1-4 galactosyltransferase (beta 1-4GT), with monoclonal anti-Lc4Cer and anti-nLc4Cer antibodies, respectively. This method thus enabled us to differentiate the activity of beta 1-3GT from that of beta 1-4GT with a high degree of sensitivity. The method was then used to determine the activities of both enzymes in human gynecological carcinoma-derived cells. Four of the five cell lines derived from uterine endometrial cancer expressed significantly high levels of specific activity of beta 1-3GT among the cell lines examined, while their beta 1-4GT activities were less than 20% of that for beta 1-3GT in the endometrial carcinoma-derived cells. On the other hand, a higher specific activity of beta 1-4GT than that of beta 1-3GT was detected in the cell lines derived from uterine cervical and ovarian cancers. These findings were thus found to correlate closely with the rate of expression of Lc4Cer- and nLc4Cer-based carbohydrate chains in the cell lines based on the results of immunohistochemical staining.

Contribution of selectins to leucocyte sequestration in pulmonary microvessels by intravital microscopy in rabbits

1. Sequestration of leucocytes in the lung is the net result of leucocyte rolling and sticking in pulmonary arterioles and venules and their retention in alveolar capillaries. 2. In order to investigate whether adhesion molecules of the selectin family contribute to these phenomena the effects of fucoidin (an inhibitor of L- and P-selectin) on microhaemodynamics and leucocyte kinetic were studied in pulmonary arterioles, capillaries and venules by means of intravital fluorescence microscopy in a rabbit model. 3. Fucoidin reduced leucocyte rolling in pulmonary arterioles and venules by 75 and 83%, respectively, without affecting leucocyte sticking. In alveolar capillaries, fucoidin reduced leucocyte retention and accelerated leucocyte passage, thus reducing the alveolar transit time of leucocytes by 62%. 4. It is concluded that rolling of leucocytes in pulmonary microvessels is mediated by selectins, whereas sticking relies on selectin-independent mechanisms. 5. Leucocyte retention in alveolar capillaries is not due solely to mechanical hindrance of leucocyte passage through narrow vessel segments, as previously hypothesized, but also depends on interaction of leucocytes with the capillary endothelium.

Isolated P-selectin glycoprotein ligand-1 dynamic adhesion to P- and E-selectin

Leukocyte adhesion to vascular endothelium under flow involves an adhesion cascade consisting of multiple receptor pairs that may function in an overlapping fashion. P-selectin glycoprotein ligand-1 (PSGL-1) and L-selectin have been implicated in neutrophil adhesion to P- and E-selectin under flow conditions. To study, in isolation, the interaction of PSGL-1 with P- and E-selectin under flow, we developed an in vitro model in which various recombinant regions of extracellular PSGL-1 were coupled to 10-microm-diameter microspheres. In a parallel plate chamber with well defined flow conditions, live time video microscopy analyses revealed that microspheres coated with PSGL-1 attached and rolled on 4-h tumor necrosis factor-alpha-activated endothelial cell monolayers, which express high levels of E-selectin, and CHO monolayers stably expressing E- or P-selectin. Further studies using CHO-E and -P monolayers demonstrate that the first 19 amino acids of PSGL-1 are sufficient for attachment and rolling on both E- and P-selectin and suggest that a sialyl Lewis x-containing glycan at Threonine-16 is critical for this sequence of amino acids to mediate attachment to E- and P-selectin. The data also demonstrate that a sulfated, anionic polypeptide segment within the amino terminus of PSGL-1 is necessary for PSGL-1-mediated attachment to P- but not to E-selectin. In addition, the results suggest that PSGL-1 has more than one binding site for E-selectin: one site located within the first 19 amino acids of PSGL-1 and one or more sites located between amino acids 19 through 148.

Anticoagulant fucoidan fractions from Fucus vesiculosus induce platelet activation in vitro

Anticoagulant fucoidan fractions of different molecular weight and sulfate content were prepared and investigated for their effects on platelet function in vitro. The fucoidan fractions were incubated with human platelet rich plasma (PRP) at concentrations of 5, 10 and 50 micrograms/ml. Platelet activation was subsequently studied by a standard aggregation assay and flow cytometric determination of the activation dependent platelet-surface markers CD62p (P-selectin, GMP-140) and CD63 (GP53). All fucoidan fractions induced irreversible platelet aggregation in a dose-dependent manner. Comparing fractions of identical molecular weight (100 kDa) the low sulfate content fucoidan FF5 (S = 7.6%) exerted a significantly greater effect than the highly sulfated fucoidan FF7 (S = 10.2%) over the whole concentration range (n = 5, P < 0.05). Among fractions of identical sulfate content fucoidan-induced platelet aggregation was also found to depend on the molecular weight of the fucoidan. At concentrations of 10 and 50 micrograms/ml the high molecular weight fraction FF7/1 (150 kDa) showed a significantly greater effect than the 50 kDa fraction FF7/3 (24.8 +/- 6.7 vs. 7.0 +/- 3.5 and 54.6 +/- 13.5 vs. 15.0 +/- 9.0%, respectively; mean +/- SD, n = 5, P < 0.05). The molecular weight dependence of the fucoidan effect was also reflected by the flow cytometric data. Coincubation of FF7/1 and FF7/3 (10 micrograms/ml) with PRP increased the number of CD62p and CD63 positive platelets by 9.0 +/- 3.3 vs. 2 +/- 1.9 and 7.1 +/- 2.4 vs. 3.2 +/- 2.6% over control values, respectively (n = 5, P < 0.05). In conclusion, our results show that the low molecular weight fucoidan FF7/3 combines potent anticoagulant and fibrinolytic properties with only minor platelet activating effects and is therefore a suitable substance for further pharmacological studies.

Glycosphingolipid antigens and cancer therapy

Specific types of glycosphingolipid (GSL), which are chemically detectable in normal cells, are more highly expressed in tumors. The high level of expression on the surfaces of tumor cells causes an antibody response to these GSLs, which can therefore be described as tumor-associated antigens. Some of these GSLs have been shown to be adhesion molecules involved in tumor cell metastasis, and to be modulators of signal transduction controlling tumor cell growth and motility. Tumor-associated GSL antigens have been used in the development of antitumor vaccines. GSLs and sphingolipids involved in adhesion and signaling are therefore targets for cancer therapy.

A new procedure for establishing functional monoclonal antibodies capable of inhibiting E- or P-selectin-dependent cell adhesion

Employing a new procedure, we established many monoclonal antibodies (mAbs) which inhibit E- or P-selectin-dependent cell adhesion. One of these mAbs is capable of staining selectin in paraffin-embedded histological sections. The procedure is based on immunization of BALB/c mice with irradiated mouse myeloma NS-1 cells (syngeneic HAT-sensitive fusion partner cells) transfected with cDNA encoding human E- or P-selectin. Resulting NS-1 transfectant cells permanently express human E- or P-selectin as immunogen. The mAbs are useful for detecting selectins by flow cytometric and immunohistological methods, and for inhibiting selectin-dependent adhesion in experimental models. In contrast, the majority of anti-selectin mAbs previously established do not have these capabilities.