Role Of Cell Adhesion Molecules Research Articles

Targeting Adhesion Molecules in Cardiovascular Disorders

Cell adhesion molecules are ubiquitously expressed proteins playing a central role in controlling cell migration, proliferation, survival, and apoptosis. Besides their key function in physiological maintenance of tissue integrity, adhesion molecules play an eminent role in various pathological processes. In cardiovascular disorders, cell adhesion molecules are particularly involved in atherogenesis and atherosclerotic plaque progression. They also play a critical role in myocardial infarction and reperfusion damage and a minor role in valvular stenosis and cardiomyopathy. Their common denominator: An increased expression of adhesion molecules involved in leukocyte extravasation and accumulation. Leukocyte extravasation is a multistep process, mediated by several cell adhesion molecules including selectins (P-, E- and L-), integrins and members of the Ig superfamily (ICAM-1, VCAM-1). These molecules can be targeted for imaging purposes (e.g. to identify atherosclerotic plaques) or can serve as biomarkers for plaque destabilization. Furthermore, cell adhesion molecules can serve as drugable targets to prevent leukocyte extravasation where warranted to decrease inflammatory tissue damage (e.g. reperfusion injury). Current techniques involve blocking of binding sites, targeted drug delivery using liposomes and polymeric particles as carriers or imaging of inflammation sites using labeled cells or antibodies. This review focuses on the role of cell adhesion molecules in cardiovascular disease and the use of targeting adhesion molecules for imaging purposes and local drug delivery in cardiovascular medicine.

Effects of Pan-Selectin Antagonist GMI-1070 on the Treatment of Vaso-Occlusion in Sickle Cell Mice

Acute vaso-occlusion (VOC) in patients with sickle cell disease (SCD) induces intense pain arising from organ damage and is the major cause of morbidity and mortality. Hypoxia and abnormal sickle red blood cells (RBC) induce inflammatory mediators and activation of the vascular endothelium leading to the recruitment of adherent leukocytes and sickle RBC followed by aggregates that eventually occlude blood flow. Previous studies have implicated the critical roles of cell adhesion molecules E- and P-selectins by using intravital microscopy in SCD mice (Berkeley strain) with altered genetic backgrounds (SCD transplanted in recipients lacking E-and P-selectins), or antibodies against endothelial selectins, or small molecules directed against the selectins. Here, we designed a treatment protocol for this SCD mouse model, in which a small molecule pan-selectin antagonist (GMI-1070) is administered to sickle cell mice late in the process of established vaso-occlusion in order to test the effects of GMI-1070 in a more clinically relevant model. GMI-1070 is a small molecule pan-selectin antagonist designed on the bioactive conformation of the carbohydrate ligand and inhibits leukocyte adhesion to activated endothelium in vitro with particularly strong activity against E-selectin (IC50 = 3.4 μM). Berkeley SCD mice were generated by bone marrow transplantation into lethally irradiated C57BL/6 male mice and the fully engrafted (100% donor RBC chimerism) mice were used for intravital microscopy experiments. VOC events were induced by injection with TNF-α at time 0 and the formation of occlusions were allowed to proceed as long as possible just prior to the death of the control mice. GMI-1070 (20 mg/kg) or vehicle (PBS pH 7.4) were administered at t = 110 min. Post-capillary and collecting venules in the cremaster muscle were analyzed for effects on an established VOC event. Under these conditions, GMI-1070 significantly increased the microcirculatory blood flow to levels observed in non-sickle cell mice (vehicle: 237 ± 15 nL/sec; GMI-1070: 533 ± 58 nL/sec; p<0.0001). The recruitment of adherent leukocytes to the vascular endothelium was also significantly reduced (vehicle: 2235 ± 156; GMI-1070: 1270 ± 203 cells/mm2; p=0.0013), and there were significant and dramatic reductions in the capture of sickle red blood cells to adherent leukocytes (vehicle: 0.68 ± 0.27; GMI-1070: 0.03 ± 0.01 interactions/WBC, min, 100ml; p=0.0003). Mice began to succumb to VOC within 2.5 hours after injection of TNF-α and surgical trauma which continued until all of the control SCD mice died. Administration of GMI-1070 prevented the death of half of the treated mice within the timeframe of the experiment and extended the median survival of mice from 5 hours (control, vehicle-treated) to greater than 9 hours for the GMI-1070- treated SCD mice (p = 0.0067). These studies show that GMI-1070 can significantly and dramatically improve the condition and survival of the animals with a severe VOC even when dosed well after the initiating challenge. Thus these data strongly support the use of GMI-1070 for the treatment of patients in acute vaso-occlusive crisis. GMI-1070 is currently in a Phase I clinical trial.

Serum F11R/JAM-a levels in women with symptomatic endometriosis

OBJECTIVE: While most cycling women experience retrograde menstruation, only a few develop endometriosis. Endometriosis is an inflammatory process with altered function of immune-related cells and increased number of activated macrophages in the peritoneal environment that secrete various local products, such as growth factors and cytokines. The role of cell adhesion molecules (CAM) in inflammation is well documented. FII receptor/Junctional Adhesion Molecule (F11R/JAM) is a novel cell adhesion molecule and is a member of the immunoglobulin superfamily.

Modulation of synaptic transmission and plasticity by cell adhesion and repulsion molecules

Adhesive and repellent molecular cues guide migrating cells and growing neurites during development. They also contribute to synaptic function, learning and memory in adulthood. Here, we review the roles of cell adhesion molecules of the immunoglobulin superfamily (Ig-CAMs) and semaphorins (some of which also contain Ig-like domains) in regulation of synaptic transmission and plasticity. Interestingly, among the seven studied Ig-CAMs, the neuronal cell adhesion molecule proved to be important for all tested forms of hippocampal plasticity, while its associated unusual glycan polysialic acid is necessary and sufficient part for synaptic plasticity only at CA3-CA1 synapses. In contrast, Thy-1 and L1 specifically regulate long-term potentiation (LTP) at synapses formed by entorhinal axons in the dentate gyrus and cornu ammonis, respectively. Contactin-1 is important for long-term depression but not for LTP at CA3-CA1 synapses. Analysis of CHL1-deficient mice illustrates that at intermediate stages of development a deficit in a cell adhesion molecule is compensated but appears as impaired LTP during early and late postnatal development. The emerging mechanisms by which adhesive Ig-CAMs contribute to synaptic plasticity involve regulation of activities of NMDA receptors and L-type Ca2+ channels, signaling via mitogen-activated protein kinase p38, changes in GABAergic inhibition and motility of synaptic elements. Regarding repellent molecules, available data for semaphorins demonstrate their activity-dependent regulation in normal and pathological conditions, synaptic localization of their receptors and their potential to elevate or inhibit synaptic transmission either directly or indirectly.

Recent Developments in Targeting Eosinophil Accumulation as a Novel Therapeutic Approach for Asthma

Current therapies for asthma are aimed at controlling disease symptoms and for the majority of patients inhaled glucocorticoid anti-inflammatory therapy is both effective and well-tolerated. However, concerns remain about the adverse effects of glucocorticoids while a subset of asthmatic patients remains symptomatic despite optimal treatment thereby creating a clear unmet medical need. There is considerable evidence that implicates eosinophils as important effector cells and immunomodulators in the inflammation characteristic of asthma. Numerous in vitro and animal studies have demonstrated essential roles for cell adhesion molecules in eosinophil adhesion and transendothelial migration including the selectins, ICAM-1, VCAM-1 together with many of the μ1 and μ2 integrins. A large body of evidence has also implicated several cytokines and chemokines in the selective recruitment of eosinophils to sites of asthmatic inflammation. Biopharmaceutical approaches have been used to identify inhibitory molecules that target key elements in the processes controlling eosinophil accumulation in asthma. This review will summarise the problems and successes regarding recent developments in therapeutic strategies aimed at reducing eosinophil-mediated inflammation in the asthmatic lung.

Tanshinone I suppresses growth and invasion of human breast cancer cells, MDA-MB-231, through regulation of adhesion molecules

The role of cell adhesion molecules has been studied extensively in the process of inflammation, and these molecules are critical components of carcinogenesis and cancer metastasis. This study investigated the effect of tanshinone I derived from the traditional herbal medicine, Salvia miltiorrhiza Bunge, on the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in tumor necrosis factor-alpha (TNF-alpha)-stimulated endothelial cells. Furthermore, this study investigated the effect of tanshinone I on cancer growth, invasion and angiogenesis on human breast cancer cells MDA-MB-231, both in vitro and in vivo. Tanshinone I dose dependently inhibited ICAM-1 and VCAM-1 expressions in human umbilical vein endothelial cells (HUVECs) that were stimulated with TNF-alpha for 6 h. Pretreatment with tanshinone I significantly reduced adhesion of either monocyte U937 or MDA-MB-231 cells to HUVECs. Interestingly, the inhibitory effect of tanshinone I on monocyte and cancer cell adhesion to HUVECs was mimicked by transfection with ICAM-1 and VCAM-1 small interfering RNA. In addition, tanshinone I effectively inhibited TNF-alpha-induced production of vascular endothelial growth factor (VEGF) and VEGF-mediated tube formation in HUVECs. Tanshinone I also inhibited TNF-alpha-induced VEGF production in MDA-MB-231 cells and migration of MDA-MB-231 cells through extracellular matrix. Additionally, reduction of tumor mass volume and decrease of metastasis incidents by tanshinone I were observed in vivo. In conclusion, this study provides a potential mechanism for the anticancer effect of tanshinone I on breast cancer cells, suggesting that tanshinone I may serve as an effective drug for the treatment of breast cancer.

Cell Adhesion Molecules: Potential Therapeutic &amp; Diagnostic Implications

The role of cell adhesion molecules (CAM) and extracellular matrix proteins (ECM) in various pathological processes including angiogenesis, thrombosis, apoptosis, cell migration & proliferation are well documented. These processes can lead to both acute and chronic disease states such as ocular diseases, metastasis, unstable angina, myocardial infarction, stroke, osteoporosis, a wide range of inflammatory diseases, vascular remodeling, and neurodegenerative disorders. A key success in this field is evident from the potential role of the platelet GPIIb/IIIa integrin in the prevention and diagnosis of various thromboembolic disorders. Additionally, the use of soluble adhesion molecules as potential diagnostic markers for acute and chronic leukocyte, platelet, and endothelial cellular insult are increasingly utilized. The development of various therapeutic and diagnostic candidates based on the key role of CAM, with special emphasis on integrins in various diseases as well as the structure-function aspects of cell adhesion and signaling of the different CAM and ECM are highlighted.

Neurofascin regulates the formation of gephyrin clusters and their subsequent translocation to the axon hillock of hippocampal neurons

Little is known about the role of cell adhesion molecules (CAMs) in inhibitory synapse development. In particular, a functional link between CAMs and the clustering of postsynaptic scaffold component gephyrin, which is a critical determinant of γ-aminobutyric acid A (GABA) receptor clustering, still needs to be elaborated. At early stages of inhibitory synapse formation, gephyrin and CAM neurofascin are diffusely expressed in the soma of hippocampal neurons. Subsequently, gephyrin clusters become localized to the axon hillock and neurofascin is observed all over the soma including the axon hillock suggesting a function for neurofascin in gephyrin clustering. Transfection of expression vectors for different isoforms and mutants of neurofascin revealed that neurofascin is required for the formation of gephyrin clusters presumably dependent on extracellular interactions. Furthermore, expression of neurofascin is necessary for the translocation of gephyrin clusters to the axon hillock of hippocampal neurons as shown by shRNA-mediated knockdown. In addition, overexpression of an embryonic neurofascin isoform is sufficient for functional rescue after knockdown of endogenous neurofascin.

Endothelial Cell Adhesion Molecules and Cancer Progression

The role of cell adhesion molecules (CAMs), such as intercellular cell adhesion molecule-1 (ICAM-1), vascular endothelial cell adhesion molecule-1 (VCAM-1), E-selectin, and P-selectin, has been studied extensively in the process of inflammation. These molecules are responsible for recruiting leukocytes onto the vascular endothelium before extravasation to the injured tissues. Some circulating cancer cells have been shown to extravasate to a secondary site using a process similar to inflammatory cells. The most studied ligands for CAMs expressed on cancer cells, sialyl Lewis (a/x) antigens, are shown to be involved in adhesion to endothelial cells by binding to E-selectin. This process, shared by inflammatory cells and cancer cells, may partially explain the link between inflammation and tumorigenesis. Furthermore, this process may elucidate the therapeutic benefit of anti-inflammatory drugs in cancer treatment. The complexity of the tumor microenvironment has been revealed in the past decade. Currently, intense investigation is aimed at various aspects of the tumor microenvironment in addition to the tumor cells themselves. Here, we review the role of CAMs in extravasation of circulating cancer cells, a key step in metastasis.

The Neural Cell Adhesion Molecule Antibody Blocks Cold Water Swim Stress-Induced Analgesia and Cell Adhesion Between Lymphocytes and Cultured Dorsal Root Ganglion Neurons

Opioid-containing immune cells migrate in a site-directed manner into inflamed tissue and adhere to sensory nerve fibers. These cells release opioid peptides in close proximity to these fibers, thereby avoiding localized degradation by peptidases, and delivering opioid peptides proximal to opioid receptors to provide antinociception. The effects of the anti-neural-cell-adhesion molecule (anti-NCAM) were assessed on cold water swim stress-induced antinociception in Wistar rats with Freund's adjuvant-induced inflammation of one hindpaw. Algesiometry was assessed for both thermal and mechanical stimuli. Cell adhesion experiments examining the effects of beta-endorphin and antibodies to NCAM and intercellular cell adhesion molecule-1 and were performed on cultured dorsal root ganglion neurons and isolated lymphocytes. Lymphocyte binding was determined by fluorescence using calcein AM loaded into freshly isolated lymphocytes. The direct adhesion between lymphocytes and cultured sensory neurons was inhibited by anti-NCAM. This adhesion was also demonstrated to be opioid dependent, with lymphocyte adhesion to cultured sensory neurons reduced in the presence of 1 microM beta-endorphin, which was reversed by 100 microM naloxone. Moreover, anti-NCAM blocked cold-water-swim-induced analgesia in inflamed paws both to thermal and mechanical stimuli. However, anti-NCAM did not affect fentanyl-induced antinociception. This study provides insight into the role of cell adhesion molecules in lymphocyte adhesion to sensory neurons and a link to immune-derived antinociception.

Role of cell adhesion molecule nectin‐3 in spermatid development

Seminiferous epithelia of the testes contain two types of intercellular junctions: Sertoli-Sertoli junctions and Sertoli-spermatid junctions. The former junctions are equipped with tight and adherens junctions while the latter junctions are not. Ca2+ -independent immunoglobulin-like cell-cell adhesion molecules, nectin-2 and nectin-3, asymmetrically localize at the Sertoli cell side and at the spermatid side of Sertoli-spermatid junctions, respectively. They heterophilically trans-interact to make contact between the two cells. Nectin-2(-/-) mice have shown male-specific infertility, disrupted Sertoli-spermatid junctions and morphologically impaired spermatid development. Here we report testicular phenotypes of nectin-3(-/-) mice exhibiting male-specific infertility. Nectin-3(-/-) mice had defects in the later steps of sperm morphogenesis including distorted nuclei and abnormal distribution of mitochondria, as well as in localization of nectin-2 at the Sertoli-spermatid junctions. Transplantation of wild-type spermatogenic stem cells into the nectin-3(-/-) testes partially rescued these defects in sperm morphogenesis. These results indicate that the heterophilic trans-interaction between nectin-2 and nectin-3 is essential for the formation and maintenance of Sertoli-spermatid junctions that plays a critical role in spermatid development.

Reuptake of Extracellular Amelogenin by Dental Epithelial Cells Results in Increased Levels of Amelogenin mRNA through Enhanced mRNA Stabilization

Amelogenin is an extracellular matrix protein secreted by ameloblasts and is a major component of enamel matrix. Recently, in addition to their role in enamel formation, the biological activity of enamel proteins in the process of cell differentiation has recently become widely appreciated. In this study, we examined the biological activity of amelogenin on ameloblast differentiation. Recombinant mouse amelogenin (rm-amelogenin) enhanced the expression of endogenous amelogenin mRNA in a cultured dental epithelial cell line (HAT-7), despite a lack of increased amelogenin promoter activity. To solve this discrepancy, we analyzed the effects of rm-amelogenin on the stability of amelogenin mRNA. The half-life of amelogenin mRNA is extremely short, but in the presence of rm-amelogenin its half-life was extended three times longer than the control. Furthermore, we showed the entry of exogenous fluorescein isothiocyanate-conjugated rm-amelogenin into the cytoplasm of HAT-7 cells. It follows from our results that exogenous amelogenin increases amelogenin mRNA levels through stabilization of mRNA in the cytoplasm of HAT-7 cells. Here we speculated that during differentiation, dental epithelial cells utilize a unique mechanism for increasing the production of amelogenin, the reuptake of secreted amelogenin.

Local Delivery of Ibuprofen via Controlled-release Polymers Prevents Angiographic Vasospasm in a Monkey Model of Subarachnoid Hemorrhage

Adhesion and migration of leukocytes into the periadventitial space play a role in the pathophysiology of vasospasm after subarachnoid hemorrhage (SAH). Intercellular adhesion molecule-1 is a determinant cell adhesion molecule involved in this process. Ibuprofen has been shown to inhibit intercellular adhesion molecule-1 upregulation and prevent vasospasm in animal models of SAH. In this study, we report the toxicity and efficacy of locally delivered ibuprofen incorporated into controlled-release polymers to prevent vasospasm in a monkey model of SAH. Ibuprofen was incorporated into ethylene-vinyl acetate (EVAc) polymers at 45% loading (wt:wt). For the toxicity study, cynomolgus monkeys (n = 5) underwent surgical implantation of either blank/EVAc polymers (n = 3) or 45% ibuprofen/EVAc polymers (n = 2) in the subarachnoid space, were followed up for 13 weeks, and were killed for histopathological analysis. For the efficacy study, cynomolgus monkeys (n = 14) underwent cerebral angiography 7 days before and 7 days after surgery and SAH and were randomized to receive either a 45% ibuprofen/EVAc polymer (n = 7; mean dose of ibuprofen, 6 mg/kg) or blank EVAc polymers (n = 7) in the subarachnoid space. Angiographic vasospasm was determined by digital image analysis. Student's t test was used for analysis. Animals implanted with ibuprofen polymers showed no signs of local or systemic toxicity. Animals treated with ibuprofen polymers had 91 +/- 9% lumen patency of the middle cerebral artery, compared with 53 +/- 11% of animals treated with blank/EVAc polymers (P < 0.001). Ibuprofen polymers are safe and prevent angiographic vasospasm after SAH in the monkey model. These findings support the role of cell adhesion molecules and inflammation in the pathophysiology of vasospasm.

Akt-dependent cell size regulation by the adhesion molecule on glia occurs independently of phosphatidylinositol 3-kinase and Rheb signaling.

The role of cell adhesion molecules in mediating interactions with neighboring cells and the extracellular matrix has long been appreciated. More recently, these molecules have been shown to modulate intracellular signal transduction cascades critical for cell growth and proliferation. Expression of adhesion molecule on glia (AMOG) is downregulated in human and mouse gliomas, suggesting that AMOG may be important for growth regulation in the brain. In this report, we examined the role of AMOG expression on cell growth and intracellular signal transduction. We show that AMOG does not negatively regulate cell growth in vitro or in vivo. Instead, expression of AMOG in AMOG-deficient cells results in a dramatic increase in cell size associated with protein kinase B/Akt hyperactivation, which occurs independent of phosphatidylinositol 3-kinase activation. AMOG-mediated Akt phosphorylation specifically activates the mTOR/p70S6 kinase pathway previously implicated in cell size regulation, but it does not depend on tuberous sclerosis complex/Ras homolog enriched in brain (Rheb) signaling. These data support a novel role for a glial adhesion molecule in cell size regulation through selective activation of the Akt/mTOR/S6K signal transduction pathway.

Role of Cell Adhesion in the Maintenance of Hematopoietic Stem Cells in the Bone Marrow Niche.

Interaction of HSCs with their particular microenvironments, known as the stem cell niches, is critical for adult hematopoiesis in the bone marrow (BM). HSCs are keeping the balance of the quiescence and the self-renewal in the stem cell niche, and are maintaining long-term hematopoiesis. We have demonstrated that HSCs expressing the receptor tyrosine kinase Tie2 are quiescent and anti-apoptotic, transplantable and comprise a side-population (SP) of HSCs, which contact closely to angiopoietin-1, a ligand for Tie2, expressing osteoblasts (OBs) in the BM niche. Tie2 and Ang-1 are part of a key signaling interaction between HSCs and niche cells. This signaling pathway regulates the feature of HSCs in the BM niche. The interaction of Tie2 with Ang-1 in vitro is sufficient to maintain the long-term blood-repopulating (LTR) activity of HSCs in vivo by preventing cell division. In addition, Ang-1 enhanced the ability of HSCs to become quiescent and also induced their adhesion to bone surface, resulting protection of HSC compartment from stresses which suppress hematopoiesis (Arai et al., Cell, 2004). In this study, we focused on the role of cell adhesion molecule on the maintenance of HSCs in BM niche. A previous paper reported that both quiescent HSCs and some of osteoblasts express N-cadherin. We found that Tie2+ HSC expressed N- and VE-cadherin, and OBs expressed N-, P-, and OB-cadherin. This suggests that an adherens junction between HSCs and OBs created via N-cadherin may contribute to HSC maintenance. Furthermore, N-cadherin overexpressing OP9 stromal cells (OP9/N-cadherin) maintained LTC-IC more than control OP9 cells did. Overexpression of N-cadherin in HSCs also maintained colony formation. In addition, in the presence of Ang-1 in coculture of OP9/N-cadherin and HSCs facilitated the maintenance of CFU-C and HPP-CFC formation after long-term culture. Furthermore, Ang-1 treatment upregulated the expression of N-cadherin in Tie2+ HSCs as well as β1-integrin. It suggests that Tie2/Ang-1 signaling enhanced cell-cell adhesion between HSCs and OBs.Altogether, these observations led us to the novel model that the localization of HSCs on bone surface is regulated by stem cell specific adhesion molecules such as N-cadherin. Once the HSCs adjacently localize to OBs, Ang-1 produced by OBs may activate Tie2 on the HSCs and promote tight adhesion of HSCs in the niche, resulting in quiescence and enhanced survival of HSCs.

Regulation of cell–cell adhesion during Dictyostelium development

During development of Dictyostelium, four adhesion systems have been identified and adherens junction-like structures have been discovered in the fruiting body. The temporal and spatial expression of cell adhesion molecules (CAMs) is under stringent developmental control, corresponding to major shifts in morphological complexity. Genetic manipulations, including over-expression and knockout mutations, of the adhesion genes, cadA (encoding DdCAD-1), csaA (gp80) and lagC (gp150), have shed light on new roles for cell adhesion molecules in aggregate size regulation, cell-type proportioning, cell differentiation and cell sorting. As cell-cell interactions remain highly dynamic within cell streams and aggregates, mechanisms must exist to facilitate the rapid assembly and disassembly of adhesion complexes. Studies on gp80 have led to a model for the rapid assembly of adhesion complexes via lipid rafts.

The role of cell adhesion molecule in cancer progression and its application in cancer therapy.

Multiple and diverse cell adhesion molecules take part in intercellular and cell-extracellular matrix interactions of cancer. Cancer progression is a multi-step process in which some adhesion molecules play a pivotal role in the development of recurrent, invasive, and distant metastasis. A growing body of evidence indicates that alterations in the adhesion properties of neoplastic cells play a pivotal role in the development and progression of cancer. Loss of intercellular adhesion and the desquamation of cells from the underlying lamina propria allows malignant cells to escape from their site of origin, degrade the extracellular matrix, acquire a more motile and invasion phenotype, and finally, invade and metastasize. In addition to participating in tumor invasiveness and metastasis, adhesion molecules regulate or significantly contribute to a variety of functions including signal transduction, cell growth, differentiation, site-specific gene expression, morphogenesis, immunologic function, cell motility, wound healing, and inflammation. Cell adhesion molecule (CAM), a diverse system of transmembrane glycoproteins has been identified that mediates the cell-cell and cell-extracellular matrix adhesion and also serves as the receptor for different kinds of virus. We summarize recent progress regarding the role of CAM, particularly, immunoglobulin-CAMs and cadherins in the progression of cancer and discuss the potential application of CAMs in the development of cancer therapy mainly on urogenital cancer.

Regulators of neurite outgrowth: role of cell adhesion molecules.

Neuronal differentiation is a fundamental event in the development of the nervous system as well as in the regeneration of damaged nervous tissue. The initiation and guidance of a neurite are accomplished by positive (permissive or attractive), negative (inhibitory or repulsive), or guiding (affecting the advance of the growth cone) signals from the extracellular space. The signals may arise from either the extracellular matrix (ECM) or the surface of other cells, or be diffusible secreted factors. Based on this classification, we briefly describe selected positive, negative, and guiding signaling cues focusing on the role of cell adhesion molecules (CAMs). CAMs not only regulate cell-cell and cell-ECM adhesion "mechanically," they also trigger intracellular signaling cascades launching neurite outgrowth. Here, we describe the structure, function, and signaling of three key CAMs found in the nervous system: N-cadherin and two Ig-CAMs, L1 and the neural cell adhesion molecule NCAM.

Recent advances in melanoma biology.

The incidence and mortality rates of melanoma have increased at annual rates of 2%-3% for the last 30 years. Disseminated disease is largely refractory to cytotoxic chemotherapy and is almost universally fatal. Several recent advances in melanoma biology offer new strategies for potentially treating this aggressive malignancy. This review focuses on three significant advances involving tumor initiation, etiology, and progression. New experimental models reveal a direct role for UV-B light in initiating melanomas in human skin. Studies on E- and N-cadherin elucidate the importance of local homeostatic mechanisms in regulating tumor progression. Finally, several discoveries concerning apoptotic mechanisms in melanoma suggest strategies for future treatments.

Abstracts of Recent Cochrane Wounds Group Reviews

There is abundant evidence of altered immune function in endometriosis. The task that remains is to attempt a synthesis from the accumulated data, to try to make some sense of the observed phenomena and to fit them into a conceptual framework; this might permit the formulation and testing of hypotheses. Evidently, eutopic endometrium does not engender an immune response in normal subjects, otherwise the endometrium would be subject to autoimmune destruction. It has also been established that the overwhelming majority of women regurgitate menstrual debris into the peritoneal cavity. Why does this lead to endometriosis in some, but not in others? There are several possible explanations. The uterus might act as a privileged site, i.e. be exempt from immune effector mechanisms. This would certainly be conducive to the reproductive goal, the survival of the fetal allograft. Endometrium would then not enjoy the immunologic tolerance of most other tissues, and upon leaving the uterus and entering an immunocompetent environment would be subject to immune attack. In normal subjects, this could consist of elimination of menstrual debris without further sequelae. An altered response, characterized by the production of antibody that could mask receptors for cytotoxic or phagocytic effector cells, would permit persistence of ectopic endometrium.The alternative to this hypothesis is that the uterus is not a privileged site, and that the organism is normally tolerant to endometrial antigens. Menstrual debris would be eliminated intraperitoneally without loss of tolerance due to the presence of homeostatic mechanisms including suppressor T cells and suppressive cytokines. In endometriosis, this tolerance breaks down, as is the case in several autoimmune disorders, causing a chronic inflammatory response with the release of toxic factors and, eventually, peritoneal scarring.Finally, the role of cell adhesion molecules, including the integrins, is only just being explored. The behaviour of these molecules in ectopic endometrium differs from that in eutopic endometrium, and it remains to be seen whether regurgitated endometrial debris from normal subjects is different from that of endometriosis sufferers. It seems that this will be an area of intense investigation in the immediate future.