Filopodia formation mediated by receptor tyrosine kinase Ror2 is required for Wnt5a-induced cell migration

Aberrant regulation of Wnt signaling in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies in the world. Several signaling pathways, including the wingless/int-1 (Wnt) signaling pathway, have been shown to be commonly activated in HCC. The Wnt signaling pathway can be triggered via both catenin β1 (CTNNB1)-dependent (also known as “canonical”) and CTNNB1-independent (often referred to as “non-canonical”) pathways. Specifically, the canonical Wnt pathway is one of those most frequently reported in HCC. Aberrant regulation from three complexes (the cell-surface receptor complex, the cytoplasmic destruction complex and the nuclear CTNNB1/T-cell-specific transcription factor/lymphoid enhancer binding factor transcriptional complex) are all involved in HCC. Although the non-canonical Wnt pathway is rarely reported, two main non-canonical pathways, Wnt/planar cell polarity pathway and Wnt/Ca²⁺ pathway, participate in the regulation of hepatocarcinogenesis. Interestingly, the canonical Wnt pathway is antagonized by non-canonical Wnt signaling in HCC. Moreover, other signaling cascades have also been demonstrated to regulate the Wnt pathway through crosstalk in HCC pathogenesis. This review provides a perspective on the emerging evidence that the aberrant regulation of Wnt signaling is a critical mechanism for the development of HCC. Furthermore, crosstalk between different signaling pathways might be conducive to the development of novel molecular targets of HCC.

Ror2 signaling is required for local upregulation of GDF6 and activation of BMP signaling at the neural plate border

The receptor tyrosine kinase Ror2 is a major Wnt receptor that activates β-catenin-independent signaling and plays a conserved role in the regulation of convergent extension movements and planar cell polarity in vertebrates. Mutations in the ROR2 gene cause recessive Robinow syndrome in humans, a short-limbed dwarfism associated with craniofacial malformations. Here, we show that Ror2 is required for local upregulation of gdf6 at the neural plate border in Xenopus embryos. Ror2 morphant embryos fail to upregulate neural plate border genes and show defects in the induction of neural crest cell fate. These embryos lack the spatially restricted activation of BMP signaling at the neural plate border at early neurula stages, which is required for neural crest induction. Ror2-dependent planar cell polarity signaling is required in the dorsolateral marginal zone during gastrulation indirectly to upregulate the BMP ligand Gdf6 at the neural plate border and Gdf6 is sufficient to rescue neural plate border specification in Ror2 morphant embryos. Thereby, Ror2 links Wnt/planar cell polarity signaling to BMP signaling in neural plate border specification and neural crest induction.

Wnt5a Signaling in Cancer

Wnt5a is involved in activating several non-canonical WNT signaling pathways, through binding to different members of the Frizzled- and Ror-family receptors. Wnt5a signaling is critical for regulating normal developmental processes, including proliferation, differentiation, migration, adhesion and polarity. However, the aberrant activation or inhibition of Wnt5a signaling is emerging as an important event in cancer progression, exerting both oncogenic and tumor suppressive effects. Recent studies show the involvement of Wnt5a in regulating cancer cell invasion, metastasis, metabolism and inflammation. In this article, we review findings regarding the molecular mechanisms and roles of Wnt5a signaling in various cancer types, and highlight Wnt5a in ovarian cancer.

WNT5A-ROR2 is induced by inflammatory mediators and is involved in the migration of human ovarian cancer cell line SKOV-3

Background

Wnt5A, which is a member of the non-transforming Wnt protein family, is implicated in inflammatory processes. It is also highly expressed by ovarian cancer cells. ROR2, which is a member of the Ror-family of receptor tyrosine kinases, acts as a receptor or co-receptor for Wnt5A. The Wnt5A–ROR2 signaling pathway plays essential roles in the migration and invasion of several types of tumor cell and influences their cell polarity. We investigated the modulation of Wnt5A–ROR2 by inflammatory mediators and its involvement in the migration of the human ovarian cancer cell line SKOV-3.

Methods

SKOV-3 cells were treated with LPS (lipopolysaccharide), LTA (lipoteichoic acid) and recombinant human IL-6 alone or in combination with STAT3 inhibitor (S1155S31-201) or NF-kB inhibitor (BAY11-7082) for 4, 8, 12, 24 and 48 h. The Wnt5A and ROR2 expression levels were determined at the gene and protein levels. Cells were transfected with specific siRNA against Wnt5A in the absence or presence of human anti-ROR2 antibody and cell migration was assessed using transwells.

Results

There was a strong downregulation of Wnt5A expression in the presence of STAT3 or NF-kB inhibitors. Cell stimulation with LTA or IL-6 for 8 h led to significantly increased levels of Wnt5A (5- and 3-fold higher, respectively). LPS, LTA or IL-6 treatment significantly increased ROR2 expression (2-fold after 48 h). LPS- or LTA-induced Wnt5A or ROR2 expression was abrogated in the presence of STAT3 inhibitor (p < 0.001). IL-6-induced Wnt5A expression was abrogated by both STAT3 and NF-kB inhibitors (p < 0.001). Although not significant, IL-6-induced ROR2 expression showed a modest decrease when STAT3 inhibitor was used. Moreover, cell migration was decreased by 80 % in siRNA Wnt5A-transfected cells in the presence of anti-human ROR2 antibody (p < 0.001).

Conclusions

This study revealed for the first time that inflammatory mediators modulate Wnt5A and ROR2 through NF-kB and STAT3 transcription factors and this may play a role in ovarian cancer cell migration. The results described here provide new insight into the role of the Wnt5A–ROR2 complex in ovarian cancer progression in relation to inflammation.

Dysregulation of WNT5A/ROR2 Signaling Characterizes the Progression of Barrett-Associated Esophageal Adenocarcinoma

The mechanism underlying the progression of normal esophageal mucosa to esophageal adenocarcinoma remains elusive. WNT5A is a noncanonical WNT, which mainly functions via the receptor tyrosine kinase-like orphan receptor 2 (ROR2), and has an unclear role in carcinogenesis. In this study, we aimed to determine the role of WNT5A/ROR2 signaling in esophageal adenocarcinoma. Analysis of WNT5A and ROR2 expression patterns in healthy controls, Barrett and esophageal adenocarcinoma patients' esophageal clinical specimens as well as in various esophageal cell lines demonstrated a ROR2 overexpression in esophageal adenocarcinoma tissues compared with Barrett and healthy mucosa, whereas WNT5A expression was found significantly downregulated toward esophageal adenocarcinoma formation. Treatment of esophageal adenocarcinoma OE33 cells with human recombinant WNT5A (rhWNT5A) significantly suppressed proliferation, survival, and migration in a dose-dependent fashion. rhWNT5A was found to inhibit TOPflash activity in ROR2 wild-type cells, whereas increased TOPflash activity in ROR2-knockdown OE33 cells. In addition, ROR2 knockdown alone abolished cell proliferation and weakened the migration properties of OE33 cells. These findings support an early dysregulation of the noncanonical WNT5A/ROR2 pathway in the pathogenesis of esophageal adenocarcinoma, with the loss of WNT5A expression together with the ROR2 overexpression to be consistent with tumor promotion.

IMPLICATIONS

The dysregulation of WNT5A/ROR2 noncanonical WNT signaling in Barrett-associated esophageal adenocarcinoma introduces possible prognostic markers and novel targets for tailored therapy of this malignancy. Mol Cancer Res; 14(7); 647-59. ©2016 AACR.

Wnt Signaling in Cardiac Disease

Wnt signaling encompasses multiple and complex signaling cascades and is involved in many developmental processes such as tissue patterning, cell fate specification, and control of cell division. Consequently, accurate regulation of signaling activities is essential for proper embryonic development. Wnt signaling is mostly silent in the healthy adult organs but a reactivation of Wnt signaling is generally observed under pathological conditions. This has generated increasing interest in this pathway from a therapeutic point of view. In this review article, the involvement of Wnt signaling in cardiovascular development will be outlined, followed by its implication in myocardial infarct healing, cardiac hypertrophy, heart failure, arrhythmias, and atherosclerosis. The initial experiments not always offer consensus on the effects of activation or inactivation of the pathway, which may be attributed to (i) the type of cardiac disease, (ii) timing of the intervention, and (iii) type of cells that are targeted. Therefore, more research is needed to determine the exact implication of Wnt signaling in the conditions mentioned above to exploit it as a powerful therapeutic target.

Wnt5a-Ror2 signaling in mesenchymal stem cells promotes proliferation of gastric cancer cells by activating CXCL16-CXCR6 axis

Wnt5a‐Ror2 signaling has been shown to play important roles in promoting aggressiveness of various cancer cells in a cell‐autonomous manner. However, little is known about its function in cancer‐associated stromal cells, including mesenchymal stem cells (MSCs). Thus, we examined the role of Wnt5a‐Ror2 signaling in bone marrow‐derived MSCs in regulating proliferation of undifferentiated gastric cancer cells. Coculture of a gastric cancer cell line, MKN45, with MSCs either directly or indirectly promotes proliferation of MKN45 cells, and suppressed expression of Ror2 in MSCs prior to coculture inhibits enhanced proliferation of MKN45 cells. In addition, conditioned media from MSCs, treated with control siRNA, but not siRNAs against Ror2, can enhance proliferation of MKN45 cells. Interestingly, it was found that expression of CXCL16 in MSCs is augmented by Wnt5a‐Ror2 signaling, and that recombinant chemokine (C‐X‐C motif) ligand (CXCL)16 protein can enhance proliferation of MKN45 cells in the absence of MSCs. In fact, suppressed expression of CXCL16 in MSCs or an addition of a neutralizing antibody against CXCL16 fails to promote proliferation of MKN45 cells in either direct or indirect coculture with MSCs. Importantly, we show that MKN45 cells express chemokine (C‐X‐C motif) receptor (CXCR)6, a receptor for CXCL16, and that suppressed expression of CXCR6 in MKN45 cells results in a failure of its enhanced proliferation in either direct or indirect coculture with MSCs. These findings indicate that Wnt5a‐Ror2 signaling enhances expression of CXCL16 in MSCs and, as a result, enhanced secretion of CXCL16 from MSCs might act on CXCR6 expressed on MKN45, leading to the promotion of its proliferation.

Essential role of Wnt5a-Ror1/Ror2 signaling in metanephric mesenchyme and ureteric bud formation

Spatiotemporally regulated interaction between the metanephric mesenchyme (MM) and Wolffian duct (WD) is essential for the induction of a single ureteric bud (UB). The MM then interacts with the tip of the UB to induce outgrowth and branching of the UB, which in turn promotes growth of the adjacent MM. The Ror family receptor tyrosine kinases, Ror1 and Ror2, have been shown to act as receptors for Wnt5a to mediate noncanonical Wnt signaling. Previous studies have shown that Ror2-mutant mice exhibit ectopic formation of the UB, due to abnormal juxtaposition of the MM to the WD. We show here that both Ror1 and Ror2 are expressed in the mesenchyme between the MM and WD during UB formation. Although Ror1-mutant mice show no apparent defects in UB formation, Ror1;Ror2-double-mutant mice exhibit either defects in UB outgrowth and branching morphogenesis, associated with the loss of the MM from the UB domain, or ectopic formation of the UB. We also show genetic interactions between Ror1 and Wnt5a during UB formation. These findings suggest that Wnt5a-Ror1/Ror2 signaling regulates cooperatively the formation of the MM at the proper position to ensure normal development of the UB.

WNT-5A: signaling and functions in health and disease

WNT-5A plays critical roles in a myriad of processes from embryonic morphogenesis to the maintenance of post-natal homeostasis. WNT-5A knock-out mice fail to survive and present extensive structural malformations. WNT-5A predominantly activates β-catenin-independent WNT signaling cascade but can also activate β-catenin signaling to relay its diverse cellular effects such as cell polarity, migration, proliferation, cell survival, and immunomodulation. Moreover, aberrant WNT-5A signaling is associated with several human pathologies such as cancer, fibrosis, and inflammation. Thus, owing to its diverse functions, WNT-5A is a crucial signaling molecule currently under intense investigation with efforts to not only delineate its signaling mechanisms and functions in physiological and pathological conditions, but also to develop strategies for its therapeutic targeting.

Kif26b controls endothelial cell polarity through the Dishevelled/Daam1-dependent planar cell polarity-signaling pathway

Angiogenesis involves the coordinated growth and migration of endothelial cells (ECs) toward a proangiogenic signal. The Wnt planar cell polarity (PCP) pathway, through the recruitment of Dishevelled (Dvl) and Dvl-associated activator of morphogenesis (Daam1), has been proposed to regulate cell actin cytoskeleton and microtubule (MT) reorganization for oriented cell migration. Here we report that Kif26b--a kinesin--and Daam1 cooperatively regulate initiation of EC sprouting and directional migration via MT reorganization. First, we find that Kif26b is recruited within the Dvl3/Daam1 complex. Using a three-dimensional in vitro angiogenesis assay, we show that Kif26b and Daam1 depletion impairs tip cell polarization and destabilizes extended vascular processes. Kif26b depletion specifically alters EC directional migration and mislocalized MT organizing center (MTOC)/Golgi and myosin IIB cell rear enrichment. Therefore the cell fails to establish a proper front-rear polarity. Of interest, Kif26b ectopic expression rescues the siDaam1 polarization defect phenotype. Finally, we show that Kif26b functions in MT stabilization, which is indispensable for asymmetrical cell structure reorganization. These data demonstrate that Kif26b, together with Dvl3/Daam1, initiates cell polarity through the control of PCP signaling pathway-dependent activation.

A PTK7/Ror2 Co-Receptor Complex Affects Xenopus Neural Crest Migration

Neural crest cells are a highly migratory pluripotent cell population that generates a wide array of different cell types and failure in their migration can result in severe birth defects and malformation syndromes. Neural crest migration is controlled by various means including chemotaxis, repellent guidance cues and cell-cell interaction. Non-canonical Wnt PCP (planar cell polarity) signaling has previously been shown to control cell-contact mediated neural crest cell guidance. PTK7 (protein tyrosine kinase 7) is a transmembrane pseudokinase and a known regulator of Wnt/PCP signaling, which is expressed in Xenopus neural crest cells and required for their migration. PTK7 functions as a Wnt co-receptor; however, it remains unclear by which means PTK7 affects neural crest migration. Expressing fluorescently labeled proteins in Xenopus neural crest cells we find that PTK7 co-localizes with the Ror2 Wnt-receptor. Further, co-immunoprecipitation experiments demonstrate that PTK7 interacts with Ror2. The PTK7/Ror2 interaction is likely relevant for neural crest migration, because Ror2 expression can rescue the PTK7 loss of function migration defect. Live cell imaging of explanted neural crest cells shows that PTK7 loss of function affects the formation of cell protrusions as well as cell motility. Co-expression of Ror2 can rescue these defects. In vivo analysis demonstrates that a kinase dead Ror2 mutant cannot rescue PTK7 loss of function. Thus, our data suggest that Ror2 can substitute for PTK7 and that the signaling function of its kinase domain is required for this effect.

Upregulation of the expression of Wnt5a promotes the proliferation of pancreatic cancer cells in vitro and in a nude mouse model

Wnt proteins are a group of secreted signaling proteins, which function to regulate cell fate and pattern formation during embryogenesis. Altered expression of Wnt5a has been implicated in human carcinogenesis and tumor progression. A previous study identified that Wnt5a is overexpressed in human pancreatic cancer tissues, and that upregulated expression of Wnt5a promotes tumor cell migration and invasion. The present study investigated the role of Wnt5a in pancreatic cancer cell proliferation in vitro and in an orthotopic nude mouse model. Wnt5a cDNA or small interfering RNA were stably transfected into pancreatic cancer cells to assess cell proliferation-associated behaviors, including cell viability, colony formation and apoptosis in vitro, as well as tumor cell growth in an orthotopic nude mouse model. Western blot analysis was used to analyze the expression of Wnt signaling molecules. The data showed that upregulation of the expression of Wnt5a significantly promoted proliferation of the human pancreatic cells, but inhibited tumor cell apoptosis in vitro and promoted tumor growth in an orthotopic nude mouse model. By contrast, knockdown of the expression of Wnt5a inhibited cell growth and promoted apoptosis of the pancreatic cancer cells. The data also revealed that β-catenin mediated the effects of Wnt5a on the regulation of pancreatic cancer cell apoptosis in vitro. These results suggested that Wnt5a is involved in the modulation of pancreatic cancer cell proliferation, and that Wnt5a may be a potential target for pancreatic cancer therapy.

Multifaceted signaling regulators of chondrogenesis: Implications in cartilage regeneration and tissue engineering

Defects of articular cartilage present a unique clinical challenge due to its poor self-healing capacity and avascular nature. Current surgical treatment options do not ensure consistent regeneration of hyaline cartilage in favor of fibrous tissue. Here, we review the current understanding of the most important biological regulators of chondrogenesis and their interactions, to provide insight into potential applications for cartilage tissue engineering. These include various signaling pathways, including: fibroblast growth factors (FGFs), transforming growth factor β (TGF-β)/bone morphogenic proteins (BMPs), Wnt/β-catenin, Hedgehog, Notch, hypoxia, and angiogenic signaling pathways. Transcriptional and epigenetic regulation of chondrogenesis will also be discussed. Advances in our understanding of these signaling pathways have led to promising advances in cartilage regeneration and tissue engineering.

Wnt5a and Ror2 expression associate with the disease progress of primary thyroid lymphoma

Primary thyroid lymphoma (PTL) is a rare malignant thyroid tumor; its pathogenesis is closely related to chronic lymphocytic thyroiditis. The different pathological subtypes and stages of PTL have distinct clinical characteristics and prognosis, but the specific reasons are not clear. Wnt5a is a representative protein of non-canonical Wnt signaling. It plays an important role in many different types of tumors. This study is to explore the changes of Wnt5a and its receptor Ror2 in PTL development process and the clinical significance of their represent. We collected 22 PTL patient tumor specimens and clinical data. We observed the expression of Wnt5a and Ror2 in PTL tumor tissues by immunohistochemistry. Wnt5a was expressed positively in 12 (54.5 %) cases, and Ror2 was expressed positively in 18 (81.8 %) cases. The expression of Wnt5a had a significant difference in different pathological subtypes of PTL (P < 0.05). Wnt5a and Ror2 expression were associated with local invasion and clinical stage, respectively (P < 0.05), and had no significant correlation with age, gender, and tumor size. Although, no significant difference in overall survival was found between positive and negative groups of Wnt5a (P = 0.416) or Ror2 (P = 0.256), respectively. We still consider that Wnt5a and Ror2 play a complex and subtle role in the pathogenesis and progression of PTL and may become potential biomarkers and therapeutic targets of PTL.

The Orphan Receptor Tyrosine Kinase ROR2 Facilitates MSCs to Repair Lung Injury in ARDS Animal Model

There are some limitations to the therapeutic effects of mesenchymal stem cells (MSCs) on acute respiratory distress syndrome (ARDS) due to their low engraftment and differentiation rates in lungs. We found previously that noncanonical Wnt5a signaling promoted the differentiation of mouse MSCs (mMSCs) into type II alveolar epithelial cells (AT II cells), conferred resistance to oxidative stress, and promoted migration of MSCs in vitro. As receptor tyrosine kinase-like orphan receptor 2 (ROR2) is an essential receptor for Wnt5a, it was reasonable to deduce that ROR2 might be one of the key molecules for the therapeutic effect of MSCs in ARDS. The mMSCs that stably overexpressed ROR2 or the green fluorescent protein (GFP) control were transplanted intratracheally into the ARDS mice [induced by intratracheal injection of lipopolysaccharide (LPS)]. The results showed that ROR2-overexpressing mMSCs led to more significant effects than the GFP controls, including the retention of the mMSCs in the lung, differentiation into AT II cells, improvement of alveolar epithelial permeability, improvement of acute LPS-induced pulmonary inflammation, and, finally, reduction of the pathological impairment of the lung tissue. In conclusion, MSCs that overexpress ROR2 could further improve MSC-mediated protection against epithelial impairment in ARDS.

The PTK7 and ROR2 Protein Receptors Interact in the Vertebrate WNT/Planar Cell Polarity (PCP) Pathway

The non-canonical WNT/planar cell polarity (WNT/PCP) pathway plays important roles in morphogenetic processes in vertebrates. Among WNT/PCP components, protein tyrosine kinase 7 (PTK7) is a tyrosine kinase receptor with poorly defined functions lacking catalytic activity. Here we show that PTK7 associates with receptor tyrosine kinase-like orphan receptor 2 (ROR2) to form a heterodimeric complex in mammalian cells. We demonstrate that PTK7 and ROR2 physically and functionally interact with the non-canonical WNT5A ligand, leading to JNK activation and cell movements. In the Xenopus embryo, Ptk7 functionally interacts with Ror2 to regulate protocadherin papc expression and morphogenesis. Furthermore, we show that Ptk7 is required for papc activation induced by Wnt5a. Interestingly, we find that Wnt5a stimulates the release of the tagged Ptk7 intracellular domain, which can translocate into the nucleus and activate papc expression. This study reveals novel molecular mechanisms of action of PTK7 in non-canonical WNT/PCP signaling that may promote cell and tissue movements.

Functional Crosstalk Between WNT Signaling and Tyrosine Kinase Signaling in Cancer

Extensive molecular characterization of tumors has revealed that the activity of multiple signaling pathways is often simultaneously dampened or enhanced in cancer cells. Aberrant WNT signaling and tyrosine kinase signaling are two pathways that are frequently up- or downregulated in cancer. Although signaling pathways regulated by WNTs, tyrosine kinases, and other factors are often conceptualized as independent entities, the biological reality is likely much more complex. Understanding the mechanisms of crosstalk between multiple signal transduction networks is a key challenge for cancer researchers. The overall goals of this review are to describe mechanisms of crosstalk between WNT and tyrosine kinase pathways in cancer and to discuss how understanding intersections between WNT and tyrosine kinase signaling networks might be exploited to improve current therapies.

High ROR2 expression in tumor cells and stroma is correlated with poor prognosis in pancreatic ductal adenocarcinoma

RTK-like orphan receptor 2 (ROR2) is overexpressed in several cancers and has tumorigenic activity. However, the expression of ROR2 and its functional and prognostic significance have yet to be evaluated in pancreatic ductal adenocarcinoma (PDAC). Quantitative real-time polymerase chain reaction was used to characterize the expression of ROR2 mRNA in PDAC, corresponding peritumoral tissues, and PDAC cell lines. Immunohistochemical analysis with tissue microarrays was used to evaluate ROR2 expression in PDAC and to investigate the relationship of this expression to clinicopathological factors and prognosis. The expression of ROR2 mRNA and protein was significantly higher in PDAC than in normal pancreatic tissues. High cytoplasmic ROR2 expression in cancer cells was significantly associated with a primary tumor, distant metastasis, and TNM stage, and high stromal ROR2 expression was significantly associated with regional lymph node metastasis and TNM stage. The Kaplan–Meier method and Cox regression analyses showed that high ROR2 expression in tumor cytoplasm or stromal cells was significantly associated with malignant attributes and reduced survival in PDAC. We present strong evidence that ROR2 could be used as an indicator of poor prognosis and could represent a novel therapeutic target for PDAC.

Non-canonical WNT signalling in the lung

The role of WNT signalling in metazoan organogenesis has been a topic of widespread interest. In the lung, while the role of canonical WNT signalling has been examined in some detail by multiple studies, the non-canonical WNT signalling has received limited attention. Reliable evidence shows that this important signalling mechanism constitutes a major regulatory pathway in lung development. In addition, accumulating evidence has also shown that the non-canonical WNT pathway is critical for maintaining lung homeostasis and that aberrant activation of this pathway may underlie several debilitating lung diseases. Functional analyses have further revealed that the non-canonical WNT pathway regulates multiple cellular activities in the lung that are dependent on the specific cellular context. In most cell types, non-canonical WNT signalling regulates canonical WNT activity, which is also critical for many aspects of lung biology. This review will summarize what is currently known about the role of non-canonical WNT signalling in lung development, homeostasis and pathogenesis of disease.

Spatial and temporal aspects of Wnt signaling and planar cell polarity during vertebrate embryonic development

Wnt signaling pathways act at multiple locations and developmental stages to specify cell fate and polarity in vertebrate embryos. A long-standing question is how the same molecular machinery can be reused to produce different outcomes. The canonical Wnt/β-catenin branch modulates target gene transcription to specify cell fates along the dorsoventral and anteroposterior embryonic axes. By contrast, the Wnt/planar cell polarity (PCP) branch is responsible for cell polarization along main body axes, which coordinates morphogenetic cell behaviors during gastrulation and neurulation. Whereas both cell fate and cell polarity are modulated by spatially- and temporally-restricted Wnt activity, the downstream signaling mechanisms are very diverse. This review highlights recent progress in the understanding of Wnt-dependent molecular events leading to the establishment of PCP and linking it to early morphogenetic processes.

Autonomous and nonautonomous regulation of Wnt-mediated neuronal polarity by the C. elegans Ror kinase CAM-1

Wnts are a conserved family of secreted glycoproteins that regulate various developmental processes in metazoans. Three of the five Caenorhabditis elegans Wnts, CWN-1, CWN-2 and EGL-20, and the sole Wnt receptor of the Ror kinase family, CAM-1, are known to regulate the anterior polarization of the mechanosensory neuron ALM. Here we show that CAM-1 and the Frizzled receptor MOM-5 act in parallel pathways to control ALM polarity. We also show that CAM-1 has two functions in this process: an autonomous signaling function that promotes anterior polarization and a nonautonomous Wnt-antagonistic function that inhibits anterior polarization. These antagonistic activities can account for the weak ALM phenotypes displayed by cam-1 mutants. Our observations suggest that CAM-1 could function as a Wnt receptor in many developmental processes, but the analysis of cam-1 mutants may fail to reveal CAM-1's role as a receptor in these processes because of its Wnt-antagonistic activity. In this model, loss of CAM-1 results in increased levels of Wnts that act through other Wnt receptors, masking CAM-1's autonomous role as a Wnt receptor.

WIF1 re-expression in glioblastoma inhibits migration through attenuation of non-canonical WNT signaling by downregulating the lncRNA MALAT1

Glioblastoma is the most aggressive primary brain tumor in adults and due to the invasive nature cannot be completely removed. The WNT inhibitory factor 1 (WIF1), a secreted inhibitor of WNTs, is systematically downregulated in glioblastoma and acts as strong tumor suppressor. The aim of this study was the dissection of WIF1-associated tumor-suppressing effects mediated by canonical and non-canonical WNT signaling. We found that WIF1 besides inhibiting the canonical WNT pathway selectively downregulates the WNT/calcium pathway associated with significant reduction of p38-MAPK (p38-mitogen-activated protein kinase) phosphorylation. Knockdown of WNT5A, the only WNT ligand overexpressed in glioblastoma, phenocopied this inhibitory effect. WIF1 expression inhibited cell migration in vitro and in an orthotopic brain tumor model, in accordance with the known regulatory function of the WNT/Ca(2+) pathway on migration and invasion. In search of a mediator for this function differential gene expression profiles of WIF1-expressing cells were performed. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), a long non-coding RNA and key positive regulator of invasion, emerged as the top downregulated gene. Indeed, knockdown of MALAT1 reduced migration in glioblastoma cells, without effect on proliferation. Hence, loss of WIF1 enhances the migratory potential of glioblastoma through WNT5A that activates the WNT/Ca(2+) pathway and MALAT1. These data suggest the involvement of canonical and non-canonical WNT pathways in glioblastoma promoting key features associated with this deadly disease, proliferation on one hand and invasion on the other. Successful targeting will require a dual strategy affecting both canonical and non-canonical WNT pathways.

Receptor tyrosine kinase signaling: regulating neural crest development one phosphate at a time

Receptor tyrosine kinases (RTKs) bind to a subset of growth factors on the surface of cells and elicit responses with broad roles in developmental and postnatal cellular processes. Receptors in this subclass consist of an extracellular ligand-binding domain, a single transmembrane domain, and an intracellular domain harboring a catalytic tyrosine kinase and regulatory sequences that are phosphorylated either by the receptor itself or by various interacting proteins. Once activated, RTKs bind signaling molecules and recruit effector proteins to mediate downstream cellular responses through various intracellular signaling pathways. In this chapter, we highlight the role of a subset of RTK families in regulating the activity of neural crest cells (NCCs) and the development of their derivatives in mammalian systems. NCCs are migratory, multipotent cells that can be subdivided into four axial populations, cranial, cardiac, vagal, and trunk. These cells migrate throughout the vertebrate embryo along defined pathways and give rise to unique cell types and structures. Interestingly, individual RTK families often have specific functions in a subpopulation of NCCs that contribute to the diversity of these cells and their derivatives in the mammalian embryo. We additionally discuss current methods used to investigate RTK signaling, including genetic, biochemical, large-scale proteomic, and biosensor approaches, which can be applied to study intracellular signaling pathways active downstream of this receptor subclass during NCC development.

Ror2 as a therapeutic target in cancer

Ror2 is a signaling receptor for Wnt ligands that is known to play important roles in limb development, but having no essential roles known in adult tissues. Recent evidence has implicated Ror2 in mediating both canonical and non-canonical signaling pathways. Ror2 was initially found to be highly expressed in osteosarcoma and renal cell carcinomas, and has recently been found in an increasingly long list of cancers currently including melanoma, colon cancer, melanoma, squamous cell carcinoma of the head and neck, and breast cancer. In the majority of these cancer types, Ror2 expression is associated with more aggressive disease states, consistent with a role mediating Wnt signaling regardless of the canonical or noncanonical signal. Because of the pattern of tissue distribution, the association with high-risk diseases, and the cell surface localization of this receptor, Ror2 has been identified as a potential high value target for therapeutic development. However, the recent discovery that Ror2 may function through non-kinase activities challenges this strategy and opens up opportunities to target this important molecule through alternative means.

Insight into the role of Wnt5a-induced signaling in normal and cancer cells

Wnt5a is involved in the activation of noncanonical Wnt signaling, including planar cell polarity (PCP) and Wnt-Ca(2+) pathways. The Ror-family of receptor tyrosine kinases is composed of Ror1 and Ror2 in mammals. Ror2 acts as a receptor or coreceptor for Wnt5a and regulates Wnt5a-induced activation of PCP pathway, and Wnt5a-Ror2 axis indeed plays critical roles in the developmental morphogenesis by regulating cell polarity and migration. Furthermore, Wnt5a-Ror2 axis is constitutively activated in cancer cells and confers highly motile and invasive properties on cancer cells through the expression of matrix metalloproteinase genes and enhanced formation of invadopodia. Meanwhile, Wnt5a also exhibits a tumor-suppressive function in certain cancers, including breast and colorectal carcinomas. Thus, it is of great importance to understand the respective molecular mechanisms governing Wnt5a-mediated tumor-progressive and tumor-suppressive functions, in order to develop novel and proper diagnostic and therapeutic strategies targeting Wnt5a signaling for human cancers.

Monocyte-derived dendritic cells from HLA-B27+ axial spondyloarthritis (SpA) patients display altered functional capacity and deregulated gene expression

Introduction

This study aimed to compare the functional capacity and gene expression profile of monocyte-derived dendritic cells (MD-DCs) in HLA-B27⁺ axial spondyloarthritis (SpA) patients and healthy controls.

Methods

MD-DCs were differentiated with interleukin 4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF) for seven days, starting from purified CD14⁺ monocytes and stimulated with lipopolysaccharide (LPS) for six and twenty four hours. Their capacity to stimulate allogeneic CD4⁺ T cells from unrelated healthy donor was tested. Transcriptomic study was performed with Affymetrix HuGene 1.0 ST microarrays. Gene expression levels were compared between patients and controls using a multivariate design under a linear model (LIMMA). Real-time quantitative PCR (qRT-PCR) was performed for validation of the most striking gene expression differences.

Results

The stimulatory capacity of allogeneic CD4⁺ T cells by MD-DCs from SpA patients was decreased. Transcriptomic analysis revealed 81 genes differentially expressed in MD-DCs between SpA patients and controls (P <0.01 and fold-change <0.66 or >1.5). Four selected genes were validated by qRT-PCR: ADAMTS15, CITED2, F13A1 and SELL. Expression levels of ADAMTS15 and CITED2, encoding a metallopeptidase and a transcription factor, respectively, were inversely correlated with each other (R = 0.75, P = 0.0003). Furthermore, in silico analysis identified several genes of the Wnt signaling pathway having expression co-regulated with CITED2.

Conclusion

This study revealed altered function and gene expression pattern in MD-DCs from HLA-B27⁺ axial SpA. Co-expression study showed an inverse correlation between ADAMTS15 and CITED2. Moreover, the Wnt signaling pathway appeared as deregulated in SpA MD-DCs, a finding which may be connected to Th17-driven inflammatory responses.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0417-0) contains supplementary material, which is available to authorized users.

The receptor tyrosine kinase ROR1--an oncofetal antigen for targeted cancer therapy

Targeted cancer therapies have emerged as new treatment options for various cancer types. Among targets, receptor tyrosine kinases (RTKs) are among the most promising. ROR1 is a transmembrane RTK of importance during the normal embryogenesis for the central nervous system, heart, lung and skeletal systems, but is not expressed in normal adult tissues. However, ROR1 is overexpressed in several human malignancies and may act as a survival factor for tumor cells. Its unique expression by malignant cells may provide a target for novel therapeutics including monoclonal antibodies (mAbs) and small molecule inhibitors of tyrosine kinases (TKI) for the treatment of cancer. Promising preclinical results have been reported in e.g. chronic lymphocytic leukemia, pancreatic carcinoma, lung and breast cancer. ROR1 might also be an interesting oncofetal antigen for active immunotherapy. In this review, we provide an overview of the ROR1 structure and functions in cancer and highlight emerging therapeutic options of interest for targeting ROR1 in tumor therapy.

Evolutionary divergence in the catalytic activity of the CAM-1, ROR1 and ROR2 kinase domains

Receptor tyrosine kinase-like orphan receptors (ROR) 1 and 2 are atypical members of the receptor tyrosine kinase (RTK) family and have been associated with several human diseases. The vertebrate RORs contain an ATP binding domain that deviates from the consensus amino acid sequence, although the impact of this deviation on catalytic activity is not known and the kinase function of these receptors remains controversial. Recently, ROR2 was shown to signal through a Wnt responsive, β-catenin independent pathway and suppress a canonical Wnt/β-catenin signal. In this work we demonstrate that both ROR1 and ROR2 kinase domains are catalytically deficient while CAM-1, the C. elegans homolog of ROR, has an active tyrosine kinase domain, suggesting a divergence in the signaling processes of the ROR family during evolution. In addition, we show that substitution of the non-consensus residues from ROR1 or ROR2 into CAM-1 and MuSK markedly reduce kinase activity, while restoration of the consensus residues in ROR does not restore robust kinase function. We further demonstrate that the membrane-bound extracellular domain alone of either ROR1 or ROR2 is sufficient for suppression of canonical Wnt3a signaling, and that this domain can also enhance Wnt5a suppression of Wnt3a signaling. Based on these data, we conclude that human ROR1 and ROR2 are RTK-like pseudokinases.

Interleukin-1β-induced Wnt5a enhances human corneal endothelial cell migration through regulation of Cdc42 and RhoA

Wnt5a can activate β-catenin-independent pathways for regulation of various cellular functions, such as migration, that play critical roles in wound repair. Investigation of Wnt5a signaling may help identify therapeutic targets for enhancing corneal endothelial wound healing that could provide an alternative to corneal transplantation in patients with blindness from endothelial dysfunction. However, Wnt5a signaling in corneal endothelial cells (CECs) has not been well characterized. In this study, we show transient induction of Wnt5a by interleukin-1β (IL-1β) stimulation proceeds through NF-κB in human CECs. This leads to binding of Fzd5 to Ror2, resulting in activation of disheveled protein (Dvl) and subsequently disheveled-associated activator of morphogenesis 1 (DAAM1). This leads to activation of Cdc42 and subsequent inhibition of RhoA. Inhibition of RhoA leads to parallel dephosphorylation and inactivation of LIM domain kinase 2 along with dephosphorylation and activation of slingshot 1, resulting in dephosphorylation and activation of cofilin and leading to enhanced cell migration. These findings suggest that Wnt5a enhances cell migration through activation of Cdc42 and inactivation of RhoA in human CECs.

Signaling components of the 1α,25(OH)2D3-dependent Pdia3 receptor complex are required for Wnt5a calcium-dependent signaling

Wnt5a and 1α,25(OH)2D3 are important regulators of endochondral ossification. In osteoblasts and growth plate chondrocytes, 1α,25(OH)2D3 initiates rapid effects via its membrane-associated receptor protein disulfide isomerase A3 (Pdia3) in caveolae, activating phospholipase A2 (PLA2)-activating protein (PLAA), calcium/calmodulin-dependent protein kinase II (CaMKII), and PLA2, resulting in protein kinase C (PKC) activation. Wnt5a initiates its calcium-dependent effects via intracellular calcium release, activating PKC and CaMKII. We investigated the requirement for components of the Pdia3 receptor complex in Wnt5a calcium-dependent signaling. We determined that Wnt5a signals through a CaMKII/PLA2/PGE2/PKC cascade. Silencing or blocking Pdia3, PLAA, or vitamin D receptor (VDR), and inhibition of calmodulin (CaM), CaMKII, or PLA2 inhibited Wnt5a-induced PKC activity. Wnt5a activated PKC in caveolin-1-silenced cells, but methyl-beta-cyclodextrin reduced its stimulatory effect. 1α,25(OH)2D3 reduced stimulatory effects of Wnt5a on PKC in a dose-dependent manner. In contrast, Wnt5a had a biphasic effect on 1α,25(OH)2D3-stimulated PKC activation; 50ng/ml Wnt5a caused a 2-fold increase in 1α,25(OH)2D3-stimulated PKC but higher Wnt5a concentrations reduced 1α,25(OH)2D3-stimulated PKC activation. Western blots showed that Wnt receptors Frizzled2 (FZD2) and Frizzled5 (FZD5), and receptor tyrosine kinase-like orphan receptor 2 (ROR2) were localized to caveolae. Blocking ROR2, but not FZD2 or FZD5, abolished the stimulatory effects of 1α,25(OH)2D3 on PKC and CaMKII. 1α,25(OH)2D3 membrane receptor complex components (Pdia3, PLAA, caveolin-1, CaM) interacted with Wnt5a receptors/co-receptors (ROR2, FZD2, FZD5) in immunoprecipitation studies, interactions that changed with either 1α,25(OH)2D3 or Wnt5a treatment. This study demonstrates that 1α,25(OH)2D3 and Wnt5a mediate their effects via similar receptor components and suggests that these pathways may interact.

Role of Wnt5a-Ror2 signaling in morphogenesis of the metanephric mesenchyme during ureteric budding

Development of the metanephric kidney begins with the induction of a single ureteric bud (UB) on the caudal Wolffian duct (WD) in response to GDNF (glial cell line-derived neurotrophic factor) produced by the adjacent metanephric mesenchyme (MM). Mutual interaction between the UB and MM maintains expression of GDNF in the MM, thereby supporting further outgrowth and branching morphogenesis of the UB, while the MM also grows and aggregates around the branched tips of the UB. Ror2, a member of the Ror family of receptor tyrosine kinases, has been shown to act as a receptor for Wnt5a to mediate noncanonical Wnt signaling. We show that Ror2 is predominantly expressed in the MM during UB induction and that Ror2- and Wnt5a-deficient mice exhibit duplicated ureters and kidneys due to ectopic UB induction. During initial UB formation, these mutant embryos show dysregulated positioning of the MM, resulting in spatiotemporally aberrant interaction between the MM and WD, which provides the WD with inappropriate GDNF signaling. Furthermore, the numbers of proliferating cells in the mutant MM are markedly reduced compared to the wild-type MM. These results indicate an important role of Wnt5a-Ror2 signaling in morphogenesis of the MM to ensure proper epithelial tubular formation of the UB required for kidney development.

The role of Ryk and Ror receptor tyrosine kinases in Wnt signal transduction

Receptor tyrosine kinases of the Ryk and Ror families were initially classified as orphan receptors because their ligands were unknown. They are now known to contain functional extracellular Wnt-binding domains and are implicated in Wnt-signal transduction in multiple species. Although their signaling mechanisms still remain to be resolved in detail, both Ryk and Ror control important developmental processes in different tissues. However, whereas many other Wnt-signaling responses affect cell proliferation and differentiation, Ryk and Ror are mostly associated with controlling processes that rely on the polarized migration of cells. Here we discuss what is currently known about the involvement of this exciting class of receptors in development and disease.

WNT5A encodes two isoforms with distinct functions in cancers

WNT5A, a member of the WNT family of secreted lipid-modified glycoproteins, is a critical regulator of a host of developmental processes, including limb formation, lung morphogenesis, intestinal elongation and mammary gland development. Altered WNT5A expression has been associated with a number of cancers. Interestingly, in certain types of cancers, such as hematological malignancies and colorectal carcinoma, WNT5A is inactivated and exerts a tumor suppressive function, while in other cancers, such as melanoma and gastric carcinoma, WNT5A is overexpressed and promotes tumor progression. The mechanism by which WNT5A achieves these distinct activities in cancers is poorly understood. Here, we provide evidence that the WNT5A gene produces two protein isoforms, WNT5A-long (WNT5A-L) and WNT5A-short (WNT5A-S). Amino-terminal sequencing and a WNT5A-L specific antibody demonstrate that the mature and secreted isoforms are distinct, with WNT5A-L carrying an additional 18 N-terminal amino acids. Biochemical analysis indicates that both purified proteins are similar with respect to their stability, hydrophobicity and WNT/β-catenin signaling activity. Nonetheless, modulation of these two WNT5A isoforms, either through ectopic expression or knockdown, demonstrates that they exert distinct activities in cancer cell lines: while WNT5A-L inhibits proliferation of tumor cell lines, WNT5A-S promotes their growth. Finally, we show that expression of these two WNT5A isoforms is altered in breast and cervix carcinomas, as well as in the most aggressive neuroblastoma tumors. In these cancers, WNT5A-L is frequently down-regulated, whereas WNT5A-S is found overexpressed in a significant fraction of tumors. Altogether, our study provides evidence that the distinct activities of WNT5A in cancer can be attributed to the production of two WNT5A isoforms.

Repression of cathepsin E expression increases the risk of mammary carcinogenesis and links to poor prognosis in breast cancer

Despite advances in detection and treatment for breast cancer (BC), recurrence and death rates remain unacceptably high. Therefore, more convenient diagnostic and prognostic methods still required to optimize treatments among the patients. Here, we report the clinical significance of the serum cathepsin E (CatE) activity as a novel prognostic marker for BC. Correlation analysis between the serum levels of CatE expression and clinicopathological parameters revealed that the activity levels, but not the protein levels, were negatively associated with the stages and progression of BC. Univariate and multivariate analyses demonstrated that the serum CatE activity was significantly correlated with favorable prognostic outcomes of the patients. The functional link of CatE expression to BC progression was further corroborated by in vivo and in vitro studies with mice exhibiting different levels of CatE expression. Multiparous CatE (-) (/) (-) mice spontaneously developed mammary tumors concomitant with morphological transformation and altered growth characteristics of the mammary glands. These alterations were associated in part with the induction of epithelial-mesenchymal transition and the activation of β-catenin-dependent pathway in mammary cells. Loss of CatE strongly induced the translocation and accumulation of Wnt5a in the nuclei, thereby leading to the aberrant trafficking, maturation and secretion of Wnt5a and the impaired signaling. The interaction of CatE and Wnt5a was verified by proximity ligation assay and by knockdown or restoration of CatE expression in the mammary cells. Consequently, our data demonstrate that CatE contributes to normal growth and development of mammary glands through proper trafficking and secretion of Wnt5a.

WNT5A is a key regulator of the epithelial-mesenchymal transition and cancer stem cell properties in human gastric carcinoma cells

OBJECTIVE

Direct interaction with cancer-associated fibroblasts triggers WNT5A expression in human gastric carcinoma (GC) cells. In this study, we performed gene transduction experiments to investigate the significance of WNT5A in the GC tumor microenvironment.

METHODS

Gene transduction (pWNT5A and shWNT5A) was performed in human GC-derived MKN-7 cells. Altered gene expression was examined by RT-PCR and cDNA microarray analysis. Immunohistochemical examination was carried out in human GC tissues.

RESULTS

Transduction of exogenous WNT5A expression into MKN-7 cells upregulated genes related to the epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs), and the pWNT5A transfectant showed high tumorigenicity in vivo. These results were confirmed by knockdown experiments using a lentivirus expressing shWNT5A. A cDNA microarray analysis suggested that depletion of endogenous WNT5A downregulated genes involved in intracellular signaling, chemokine-cytokine interaction and focal adhesion. High levels of WNT5A expression were observed in 66% of GC cases, with significant correlation with histological type. Interestingly, in intestinal-type GCs, WNT5A expression was detected in the periphery of tumor nests.

CONCLUSIONS

WNT5A regulates the induction of EMT and the maintenance of CSC properties in MKN-7 cells. WNT5A may play an important role in constructing an advantageous tumor microenvironment for the progression and development of human GC.

Targeted overexpression of TGF-α in the corneal epithelium of adult transgenic mice induces changes in anterior segment morphology and activates noncanonical Wnt signaling

PURPOSE

Transforming growth factor-alpha (TGF-α) transduces its signal through the epidermal growth factor receptor and is essential for corneal epithelial homeostasis. Previous studies have demonstrated that overexpression of TGF-α in the developing eye leads to anterior segment dysgenesis. However, the underlying mechanisms remain unclear. Here we examined the effects of TGF-α overexpression on adult ocular surface homeostasis.

METHODS

Binary Tet-On transgenic Krt12(rtTA)/tet-O-TGF-α mice were subjected to doxycycline (Dox) induction to overexpress TGF-α in the corneal epithelium. Intraocular pressure (IOP) was measured by noninvasive tonometry. The enucleated eyes of the experimental mice were subjected to histopathology, immunohistochemistry, and biochemistry examination.

RESULTS

Histologic and immunofluorescent examination showed that double-transgenic mice overexpressing TGF-α manifested peripheral anterior synechiae. Elevation of IOP, activation of glial cells, and loss of retinal ganglion cells were also observed. Quantitative real-time PCR revealed that the expressions of genes (RXRα, PITX2, and FOXC1) related to anterior segment dysgenesis were downregulated. Canonical Wnt signaling was suppressed, whereas noncanonical Wnt ligands (Wnt4 and Wnt5a) were upregulated. Increased myosin light chain phosphorylation suggested that noncanonical Wnt signaling is activated in affected eyes.

CONCLUSIONS

Overexpression of TGF-α in the corneal epithelium induces changes in anterior segment morphology. Corneal endothelial abnormalities are associated with the activation of the noncanonical Wnt and RhoA/ROCK signaling axis, indicating a potential application of RhoA/ROCK inhibitors as a therapeutic strategy for certain types of secondary angle-closure glaucoma.

The dual role of the novel Wnt receptor tyrosine kinase, ROR2, in human carcinogenesis

The Wnt signaling pathway is involved in the development and progression of many human cancers, yet attempts to target the pathway therapeutically have been disappointing to date. The recent discovery that the ROR2 receptor tyrosine kinase (RTK) is a novel Wnt receptor provides the potential to target the non-canonical Wnt pathway for cancer treatments. As a member of the RTK superfamily of surface receptors ROR2 appears to possess dual roles as a tumor suppressor or activator depending on tumor type. This review will explore the dual role of ROR2 in tumorigenesis and provide an up to date analysis of current literature in this rapidly expanding field.

Wnt signaling in vertebrate axis specification

The Wnt pathway is a major embryonic signaling pathway that controls cell proliferation, cell fate, and body-axis determination in vertebrate embryos. Soon after egg fertilization, Wnt pathway components play a role in microtubule-dependent dorsoventral axis specification. Later in embryogenesis, another conserved function of the pathway is to specify the anteroposterior axis. The dual role of Wnt signaling in Xenopus and zebrafish embryos is regulated at different developmental stages by distinct sets of Wnt target genes. This review highlights recent progress in the discrimination of different signaling branches and the identification of specific pathway targets during vertebrate axial development.

IL-1β stimulation of CCD-18co myofibroblasts enhances repair of epithelial monolayers through Wnt-5a

Subepithelial myofibroblasts are involved in the initiation and coordination of intestinal epithelial repair, but the molecular signaling pathways are largely unknown. The cellular adaptations that occur during repair range from dedifferentiation and migration to proliferation and redifferentiation, in a way that is strongly reminiscent of normal crypt-to-villus epithelial maturation. We therefore hypothesized that Wnt/β-catenin signaling may have a pivotal role in intestinal epithelial wound repair. We used the established scratch wound method in Caco-2 cells and in nontransformed NCM460 cells to monitor the effects of IL-1β-stimulated colonic myofibroblasts (CCD-18co) on intestinal epithelial repair, with immunoblotting and immunodepletion to examine the conditioned media. Conditioned media from IL-1β-stimulated, but not -untreated, myofibroblasts increased Caco-2 wound closure twofold over 24 h. IL-1β-stimulated myofibroblasts downregulated the differentiation marker sucrase-isomaltase in the Caco-2 cells, whereas the proliferation marker c-myc was upregulated. Array expression profiling identified Wnt-5a as the Wnt-related gene that was most upregulated (28-fold) by IL-1β stimulation of CCDs. Recombinant Wnt-5a enhanced proliferation of Caco-2 and NCM460 cells. In scratch assays, it increased migration of the leading edge in both cell lines. Wnt-5a immunodepletion of the IL-1β-CCD conditioned media abrogated the ability to enhance the repair. Wnt-5a often acts through a noncanonical signal transduction pathway. Further experiments supported this pathway in epithelial wound healing: IL-1β-CCD-mediated repair was not affected by the addition of the canonical Wnt antagonist Dickkopf-1. Furthermore, media from stimulated myofibroblasts (but not Wnt-5a-depleted media) increased c-jun in Caco-2 cell nuclear extracts. Myofibroblast-mediated noncanonical Wnt-5a signaling is therefore important in the dedifferentiation and migration stages of epithelial wound repair.

Ror2-Src signaling in metastasis of mouse melanoma cells is inhibited by NRAGE

The receptor tyrosine kinase (RTK) Ror2 plays important roles in developmental morphogenesis and mediates the filopodia formation in Wnt5a-induced cell migration. However, the function of Ror2 in noncanonical Wnt signaling resulting in cancer metastasis is largely unknown. Here, we show that Ror2 expression is higher in the highly metastatic murine B16-BL6 melanoma cells than in the low metastatic variant B16 cells. Overexpression of Ror2 increases the metastasis ability of B16 cells, and knockdown of Ror2 reduces the migration ability of B16-BL6 cells. Furthermore, the inhibition of Src kinase activity is critical for the Ror2-mediated cell migration upon Wnt5a treatment. The C-terminus of Ror2, which is deleted in brachydactyly type B (BDB), is essential for the mutual interaction with the SH1 domain of Src. Intriguingly, the Neurotrophin receptor-interacting MAGE homologue (NRAGE), which, as we previously reported, can remodel the cellular skeleton and inhibit cell-cell adhesion and metastasis of melanoma and pancreatic cancer, sharply blocks the interaction between Src and Ror2 and inhibits Ror2-mediated B16 cell migration by decreasing the activity of Src and focal adhesion kinase (FAK). Our data show that Ror2 is a potential factor in the tumorigenesis and metastasis in a Src-dependent manner that is negatively regulated by NRAGE.

Wnt signal transduction pathways

The Wnt signaling pathway is an ancient and evolutionarily conserved pathway that regulates crucial aspects of cell fate determination, cell migration, cell polarity, neural patterning and organogenesis during embryonic development. The Wnts are secreted glycoproteins and comprise a large family of nineteen proteins in humans hinting to a daunting complexity of signaling regulation, function and biological output. To date major signaling branches downstream of the Fz receptor have been identified including a canonical or Wnt/beta-catenin dependent pathway and the non-canonical or beta-catenin-independent pathway which can be further divided into the Planar Cell Polarity and the Wnt/Ca(2+) pathways, and these branches are being actively dissected at the molecular and biochemical levels. In this review, we will summarize the most recent advances in our understanding of these Wnt signaling pathways and the role of these pathways in regulating key events during embryonic patterning and morphogenesis.

The Wnt pathway and the roles for its antagonists, DKKS, in angiogenesis

The Wnt signaling pathway is involved in a wide range of developmental and physiological processes, such as cell fate specification, tissue morphogenesis, and homeostasis. Thus, its dysregulation has been found in multiple diseases, including some cardiovascular disorders. The loss or gain of function of Wnt pathway components results in abnormal vascular development and angiogenesis. Further study has revealed that Wnt signaling in endothelial cells appears to contribute to vascular morphogenesis and endothelial cell specification. Owing to the significance of Wnt signaling in angiogenesis, Wnt antagonists have been considered potential treatments for neovascular disorders. In line with this, members of the Dkk protein family (Dkks), well-known Wnt antagonists, have been recently found to regulate angiogenesis. This review summarizes our present knowledge of the roles of Wnt signaling and Wnt antagonists, particularly Dkks, in angiogenic regulation and explores the therapeutic potential of Wnt antagonists.

The tangled web of non-canonical Wnt signalling in neural migration

In all multicellular animals, successful embryogenesis is dependent on the ability of cells to detect the status of the local environment and respond appropriately. The nature of the extracellular environment is communicated to the intracellular compartment by ligand/receptor interactions at the cell surface. The Wnt canonical and non-canonical signalling pathways are found in the most primitive metazoans, and they play an essential role in the most fundamental developmental processes in all multicellular organisms. Vertebrates have expanded the number of Wnts and Frizzled receptors and have additionally evolved novel Wnt receptor families (Ryk, Ror). The multiplicity of potential interactions between Wnts, their receptors and downstream effectors has exponentially increased the complexity of the signal transduction network. Signalling through each of the Wnt pathways, as well as crosstalk between them, plays a critical role in the establishment of the complex architecture of the vertebrate central nervous system. In this review, we explore the signalling networks triggered by non-canonical Wnt/receptor interactions, focussing on the emerging roles of the non-conventional Wnt receptors Ryk and Ror. We describe the role of these pathways in neural tube formation and axon guidance where Wnt signalling controls tissue polarity, coordinated cell migration and axon guidance via remodelling of the cytoskeleton.