Wnt-5a inhibits the canonical Wnt pathway by promoting GSK-3-independent beta-catenin degradation

Hear the Wnt Ror: how melanoma cells adjust to changes in Wnt

The interplay between canonical and non-canonical Wnt pathways in development and tumorigenesis is tightly regulated. In this review we will describe the yin and the yang of canonical and non-canonical Wnt signaling pathways during melanocyte development, and melanoma genesis. Canonical Wnt signaling, represented by Wnts such as Wnt1 and Wnt3A, signals via beta-catenin to promote melanocyte differentiation and tumor development. Non-canonical Wnt signaling, specifically Wnt5A, regulates canonical pathways, and signals to induce melanoma metastasis. This review will focus on the role of Wnt5A during melanoma progression, and its relationship to canonical Wnt signaling.

Znrg, a novel gene expressed mainly in the developing notochord of zebrafish

The notochord, a defining characteristic of the chordate embryo is a critical midline structure required for axial skeletal formation in vertebrates, and acts as a signaling center throughout embryonic development. We utilized the digital differential display program of the National Center for Biotechnology Information, and identified a contig of expressed sequence tags (no. Dr. 83747) from the zebrafish ovary library in Genbank. Full-length cDNA of the identified gene was cloned by 5'- and 3'- RACE, and the resulting sequence was confirmed by polymerase chain reaction and sequencing. The cDNA clone contains 2,505 base pairs and encodes a novel protein of 707 amino acids that shares no significant homology with any known proteins. This gene was expressed in mature oocytes and at the one-cell stage, and persisted until the 5th day of development, as determined by RT-PCR. Transcripts were detected by whole-mount RNA in situ hybridization from the two-cell stage to 72 h of embryonic development. This gene was uniformly distributed from the cleavage stage up to the blastula stage. During early gastrulation, it was present in the dorsal region, and became restricted to the notochord and pectoral fin at 48 and 72 h of embryonic development. Based on its abundance in the notochord, we hypothesized that the novel gene may play an important role in notochord development in zebrafish; we named this gene, zebrafish notochord-related gene, or znrg.

The links between transcription, beta-catenin/JNK signaling, and carcinogenesis

Interactions between transcription and signaling are fundamentally important for understanding both the structure and function of genetic pathways and their role in diseases such as cancer. The finding that beta-catenin/TCF4 and JNK/c-Jun cooperate has important implications in carcinogenesis. Previously, we found that binding of c-Jun and beta-catenin/TCF4 to the c-jun promoter is dependent upon JNK activity, thus one role for this complex is to contribute to the repression and/or activation of genes that may mediate cell maintenance, proliferation, differentiation, and death, whereas deregulation of these signals may contribute to carcinogenesis. Here we address the functional links reported between activated beta-catenin/JNK signaling pathways, their component genes, and their common targets, and discuss how alterations in the properties of these genes lead to the development of cancer.

Investigating the role of the extracellular environment in modulating hepatic stellate cell biology with arrayed combinatorial microenvironments

Hepatic stellate cells (HSCs) are a major cell type of the liver that are involved in liver homeostasis. Upon liver damage, HSCs exit their normally quiescent state and become activated, leading to an increase of their proliferation, production of abnormal extracellular matrix proteins (ECMPs) and inflammatory mediators, and eventually liver fibrosis and cirrhosis. Current in vitro approaches to identify components that influence HSC biology typically investigate one factor at a time and generally ignore the complex crosstalk among the myriad of components that comprise the microenvironments of quiescent or activated HSCs. Here we describe a high throughput screening (HTS) approach to identify factors that affect HSC biology. Specifically, we integrated the use of ECMPs and signaling molecules into a combinatorial cellular microarray technology platform, thereby creating comprehensive "microenvironments". Using this technology, we performed real-time simultaneous screening of the effects of hundreds of unique microenvironments composed of ECMPs and signaling molecules on HSC proliferation and activation. From these screens, we identified combinations of microenvironment components that differentially modulate the HSC phenotype. Furthermore, analysis of HSC responses revealed that the influences of Wnt signaling molecules on HSC fate are dependent on the ECMP composition in which they are presented. Collectively, our results demonstrate the utility of high-content, array-based screens to provide a better understanding of HSC biology. Our results indicate that array-based screens may provide an efficient means for identifying candidate signaling pathways to be targeted for anti-fibrotic therapies.

Stabilized beta-catenin in lung epithelial cells changes cell fate and leads to tracheal and bronchial polyposis

The precise mechanisms by which beta-catenin controls morphogenesis and cell differentiation remain largely unknown. Using embryonic lung development as a model, we deleted exon 3 of beta-catenin via Nkx2.1-cre in the Catnb[+/lox(ex3)] mice and studied its impact on epithelial morphogenesis. Robust selective accumulation of truncated, stabilized beta-catenin was found in Nkx2.1-cre;Catnb[+/lox(ex3)] lungs that were associated with the formation of polyp-like structures in the trachea and main-stem bronchi. Characterization of polyps suggests that accumulated beta-catenin impacts epithelial morphogenesis in at least two ways. "Intracellular" accumulation of beta-catenin blocked differentiation of spatially-appropriate airway epithelial cell types, Clara cells, ciliated cells and basal cells, and activated UCHL1, a marker for pulmonary neuroendocrine cells. There was also evidence for a "paracrine" impact of beta-catenin accumulation, potentially mediated via activation of Bmp4 that inhibited Clara and ciliated, but not basal cell differentiation. Thus, excess beta-catenin can alter cell fate determination by both direct and paracrine mechanisms.

Isoreserpine promotes beta-catenin degradation via Siah-1 up-regulation in HCT116 colon cancer cells

Aberrant accumulation of intracellular beta-catenin in intestinal epithelial cells is a frequent early event during the development of colon cancer. To identify small molecules that decrease the level of intracellular beta-catenin, we performed cell-based chemical screening using genetically engineered HEK293 reporter cells to detect compounds that inhibit TOPFlash reporter activity, which was stimulated by Wnt3a-conditioned medium. We found that isoreserpine promoted the degradation of intracellular beta-catenin by up-regulation of Siah-1 in HEK293 and HCT116 colon cancer cells. Moreover, isoreserpine repressed the expression of beta-catenin/T-cell factor (TCF)-dependent genes, such as cyclin D1 and c-myc, resulting in the suppression of HCT116 cell proliferation. Our findings suggest that isoreserpine can potentially be used as a chemotherapeutic agent against colon cancer.

Proximal events in Wnt signal transduction

The Wnt family of secreted ligands act through many receptors to stimulate distinct intracellular signalling pathways in embryonic development, in adults and in disease processes. Binding of Wnt to the Frizzled family of receptors and to low density lipoprotein receptor-related protein 5 (LRP5) or LRP6 co-receptors stimulates the intracellular Wnt-beta-catenin signalling pathway, which regulates beta-cateninstability and context-dependent transcription. This signalling pathway controls many processes, such as cell fate determination, cell proliferation and self-renewal of stem and progenitor cells. Intriguingly, the transmembrane receptor Tyr kinases Ror2 and Ryk, as well as Frizzledreceptors that act independently of LRP5 or LRP6, function as receptors for Wnt and activate beta-catenin-independent pathways. This leads to changes in cell movement and polarity and to the antagonism of the beta-catenin pathway.

Wnt5b stimulates adipogenesis by activating PPARgamma, and inhibiting the beta-catenin dependent Wnt signaling pathway together with Wnt5a

Correct Wnt signaling is required for adipogenesis and alterations occur in Type 2 diabetes mellitus (T2DM). Gene expression studies showed that beta-catenin independent Wnt5b was down-regulated in T2DM preadipocytes, while its paralog Wnt5a was unchanged. Our study aimed at defining the expression profile and function of Wnt5a and Wnt5b during adipogenesis by determining their effect on aP2 and PPARgamma expression and assessing the level of beta-catenin translocation in mouse 3T3-L1 preadipocytes. Additionally, we explored the effect on adipogenic capacity by Wnt5b overexpression in combination with stimulation of the beta-catenin dependent or beta-catenin independent Wnt signaling. Expression of Wnt5b was, like Wnt5a, down-regulated upon induction of differentiation and both inhibit beta-catenin dependent Wnt signaling at the initiation of adipogenesis. Wnt5b additionally appears to be a potent enhancer of adipogenic capacity by stimulation of PPARgamma and aP2. Down-regulation of Wnt5b could therefore contribute to decreased adipogenesis observed in T2DM diabetic subjects.

Ror2 expression in squamous cell carcinoma and epithelial dysplasia of the oral cavity

In this study, the expressions of Ror2 in the normal mucosa, the epithelium dysplasia, and squamous cell carcinoma (SCC) of the oral cavity were investigated, and possible differences in the expression patterns of Ror2 and of p53, Ki67, or PCNA were examined. In Western blotting analyses, Ror2 expression in oral cancer was significantly higher than that in the normal oral mucosa. Immunohistochemically, Ror2 was localized on the plasmalemma and in the rough endoplasmic reticulum (rER). The tissue area with an Ror2-positive expression tended to differ from the area with a positive expression of p53, ki67, or PCNA, and the number of cells with an Ror2 expression tended to increase as the degree of malignancy rose in the epithelial tissues. These results suggest that Ror2 was not related to cell proliferation, but rather associated with cell polarity and cell motility, and that it was also closely associated with the degree of malignancy in oral epithelial tissue.

Notch and wingless signaling cooperate in regulation of dendritic cell differentiation

Dendritic cell (DC) differentiation is regulated by stroma via a network of soluble and cell-bound factors. Notch is one of the major elements of this network. Its role in DC differentiation, however, is controversial. Here, we demonstrate that activation of Notch signaling in hematopoietic progenitor cells (HPCs) promoted differentiation of conventional DCs via activation of the canonical Wingless (Wnt) pathway. Inhibition of the Wnt pathway abrogated the effect of Notch on DC differentiation. The fact that activation of the Wnt pathway in Notch-1-deficient embryonic stem cells restored DC differentiation indicates that Wnt signaling is downstream of the Notch pathway in regulating DC differentiation. Notch signaling activated the Wnt pathway in HPCs via expression of multiple members of the Frizzled family of Wnt receptors, which was directly regulated by the CSL (RPB-Jkappa) transcription factor. Thus, these data suggest a model of DC differentiation via cooperation between Wnt and Notch pathways.

Activation of Wnt5A signaling is required for CXC chemokine ligand 12-mediated T-cell migration

Chemokines mediate the signaling and migration of T cells, but little is known about the transcriptional events involved therein. Microarray analysis of CXC chemokine ligand (CXCL) 12-treated T cells revealed that Wnt ligands are significantly up-regulated during CXCL12 treatment. Real-time polymerase chain reaction and Western blot analysis confirmed that the expression of noncanonical Wnt pathway members (eg, Wnt5A) was specifically up-regulated during CXCL12 stimulation, whereas beta-catenin and canonical Wnt family members were selectively down-regulated. Wnt5A augmented signaling through the CXCL12-CXCR4 axis via the activation of protein kinase C. Moreover, Wnt5A expression was required for CXCL12-mediated T-cell migration, and rWnt5A sensitized human T cells to CXCL12-induced migration. Furthermore, Wnt5A expression was also required for the sustained expression of CXCR4. These results were further supported in vivo using EL4 thymoma metastasis as a model of T-cell migration. Together, these data demonstrate that Wnt5A is a critical mediator of CXCL12-CXCR4 signaling and migration in human and murine T cells.

Calcium-sensing receptor in cancer: good cop or bad cop?

The extracellular calcium-sensing receptor (CaR) is a versatile 'sensor' for di- and polycationic molecules in the body. CaR plays a key role in the defense against hypercalcemia by "sensing" extracellular calcium levels in the parathyroid and kidney, the key organs maintaining systemic calcium homeostasis. Although mutation of CaR gene has so far not been associated with any malignancy, aberrant functions of CaR have implications in malignant progression. One situation is loss of CaR expression, resulting in loss of growth suppressing effects of elevated extracellular Ca(2+) by CaR, reported in parathyroid adenoma and in colon carcinoma. Another situation is activation of CaR, resulting in increased production of parathyroid hormone-related peptide (PTHrP), a primary causal factor in hypercalcemia of malignancy and a contributor to metastatic processes involving bone. CaR signaling and effects have been studied in several cancers including ovarian cancers, gastrinomas, and gliomas in addition to comparatively detailed studies in breast, prostate, and colon cancers. Studies on H-500 rat Leydig cells, a xenotransplantable model of humoral hypercalcemia of malignancy has shed much light on the mechanisms of CaR-induced cancer cell growth and survival. Pharmacological agonists and antagonists of CaR hold therapeutic promise depending on whether activation of CaR is required such as in case of colon cancer or inactivating the receptor is required as in the case of breast- and prostate tumors.

Noncanonical Wnt signaling orchestrates early developmental events toward hematopoietic cell fate from human embryonic stem cells

During human development, signals that govern lineage specification versus expansion of cells committed to a cell fate are poorly understood. We demonstrate that activation of canonical Wnt signaling by Wnt3a promotes proliferation of human embryonic stem cells (hESCs)--precursors already committed to the hematopoietic lineage. In contrast, noncanonical Wnt signals, activated by Wnt11, control exit from the pluripotent state and entry toward mesoderm specification. Unique to embryoid body (EB) formation of hESCs, Wnt11 induces development and arrangement of cells expressing Brachyury that coexpress E-cadherin and Frizzled-7 (Fzd7). Knockdown of Fzd7 expression blocks Wnt11-dependent specification. Our study reveals an unappreciated role for noncanonical Wnt signaling in hESC specification that involves development of unique mesoderm precursors via morphogenic organization within human EBs.

Loss of TGF-beta or Wnt5a results in an increase in Wnt/beta-catenin activity and redirects mammary tumour phenotype

Introduction

The tumour-suppressive effects of transforming growth factor-beta (TGF-β) are well documented; however, the mechanistic basis of these effects is not fully understood. Previously, we showed that a non-canonical member of the Wingless-related protein family, Wnt5a, is required for TGF-β-mediated effects on mammary development. Several lines of evidence support the hypothesis that Wnt5a acts as a tumour suppressor. In addition, it has been shown that Wnt5a can antagonise canonical Wnt/β-catenin signalling in various cell types. Here we test the hypothesis that TGF-β and Wnt5a can antagonise Wnt/β-catenin signalling and redirect mammary tumour phenotype. The results provide a new mechanism for the tumour-suppressive effects of TGF-β.

Methods

Wnt/β-catenin signalling was measured in tumours with altered TGF-β (dominant-negative TGF-β type II receptor, DNIIR) or Wnt5a (Wnt5a^-/-) signalling as the accumulation of nuclear β-catenin using both confocal microscopy and cell fractionation. RT-PCR was used to measure the expression of Wnt/β-catenin target genes. Sca1 expression was determined by western blot and keratin (K) 6- and K14-positive populations were determined by immunohistochemistry.

Results

Loss of TGF-β or Wnt5a signalling resulted in stabilisation of nuclear β-catenin and expression of Wnt/β-catenin target genes suggesting that TGF-β and Wnt5a act to inhibit Wnt/β-catenin signalling in mammary epithelium. Increased expression of Sca-1 was observed in developing DNIIR and Wnt5a-/- mammary glands. DNIIR and Wnt5a-/- tumours demonstrated an expanded population of K6- and K14-expressing cells typically seen in Wnt/β-catenin-induced tumours.

Conclusions

The key findings here are that: TGF-β and Wnt5a regulate Wnt/β-catenin activity; and loss of TGF-β and Wnt5a redirect the phenotype of tumours so that they resemble tumours induced by activation of Wnt/β-catenin. The findings suggest a new mechanism for the tumour-suppressive effects of TGF-β.

Wnt signaling in Alzheimer's disease: up or down, that is the question

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, neuropathologically characterized by amyloid-beta (Abeta) plaques and hyperphosphorylated tau accumulation. AD occurs sporadically (SAD), or is caused by hereditary missense mutations in the amyloid precursor protein (APP) or presenilin-1 and -2 (PSEN1 and PSEN2) genes, leading to early-onset familial AD (FAD). Accumulating evidence points towards a role for altered Wnt/beta-catenin-dependent signaling in the etiology of both forms of AD. Presenilins are involved in modulating beta-catenin stability; therefore FAD-linked PSEN-mediated effects can deregulate the Wnt pathway. Genetic variations in the low-density lipoprotein receptor-related protein 6 and apolipoprotein E in AD have been associated with reduced Wnt signaling. In addition, tau phosphorylation is mediated by glycogen synthase kinase-3 (GSK-3), a key antagonist of the Wnt pathway. In this review, we discuss Wnt/beta-catenin signaling in both SAD and FAD, and recapitulate which of its aberrant functions may be critical for (F)AD pathogenesis. We discuss the intriguing possibility that Abeta toxicity may downregulate the Wnt/beta-catenin pathway, thereby upregulating GSK-3 and consequent tau hyperphosphorylation, linking Abeta and tangle pathology. The currently available evidence implies that disruption of tightly regulated Wnt signaling may constitute a key pathological event in AD. In this context, drug targets aimed at rescuing Wnt signaling may prove to be a constructive therapeutic strategy for AD.

Wnt signaling and osteoarthritis

Osteoarthritis is a common disease, clinically manifested by joint pain, swelling and progressive loss of function. The severity of disease manifestations can vary but most of the patients only need intermittent symptom relief without major interventions. However, there is a group of patients that shows fast progression of the disease process leading to disability and ultimately joint replacement. Apart from symptom relief, no treatments have been identified that arrest or reverse the disease process. Therefore, there has been increasing attention devoted to the understanding of the mechanisms that are driving the disease process. Among these mechanisms, the biology of the cartilage-subchondral bone unit has been highlighted as key in osteoarthritis, and pathways that involve both cartilage and bone formation and turnover have become prime targets for modulation, and thus therapeutic intervention. Studies in developmental, genetic and joint disease models indicate that Wnt signaling is critically involved in these processes. Consequently, targeting Wnt signaling in a selective and tissue specific manner is an exciting opportunity for the development of disease modifying drugs for osteoarthritis.

Wnt pathway, an essential role in bone regeneration

Fracture repair is a complex regenerative process initiated in response to injury, resulting in optimal restoration of skeletal function. Although histology characteristics at various phases of fracture repair are clear and well established, much remains to be understood about the process of bone healing, particularly at the molecular signaling level. During the past decade, secreted signaling molecules of the Wnt family have been widely investigated and found to play a central role in controlling embryonic development processes. Wnt signaling pathway also plays a pivotal role in the regulation of bone mass. Recent published data reveal that Wnt signaling pathway is activated during postnatal bone regenerative events, such as ectopic endochondral bone formation and fracture repair. Dysregulation of this pathway greatly inhibits bone formation and healing process. Interestingly, activation of Wnt pathway has potential to improve bone healing, but only utilized after mesenchymal cells have become committed to the osteoblast lineage. These advances suggest an essential role of Wnt pathway in bone regeneration.

WNT5A is a regulator of fibroblast proliferation and resistance to apoptosis

Usual interstitial pneumonia (UIP) is a specific histopathologic pattern of interstitial lung fibrosis that may be idiopathic or secondary to autoimmune diseases and environmental exposures. In this study, we compared gene expression patterns in primary fibroblasts isolated from lung tissues with UIP histology and fibroblasts isolated from lung tissues with normal histology using expression microarrays. We found that WNT5A was significantly increased in fibroblasts obtained from UIP lung tissues compared with normal lung fibroblasts, an observation verified by quantitative real-time RT-PCR and Western blot. Because the role of WNT5A in UIP is unknown, we treated normal lung fibroblasts or UIP lung fibroblasts with WNT5A, and found that WNT5A increased proliferation as well as relative resistance to H2O2-induced apoptosis. This effect was not mediated through the canonical WNT/beta-catenin pathway, as WNT5A induced a decrease in beta-catenin levels in the same cells. In addition, WNT5A induced increases in fibronectin and alpha(5)-integrin in normal lung fibroblasts. Collectively, our data suggest that WNT5A may play a role in fibroblast expansion and survival characteristics of idiopathic pulmonary fibrosis and other fibrotic interstitial lung diseases that exhibit UIP histological patterns.

Sfrp5 coordinates foregut specification and morphogenesis by antagonizing both canonical and noncanonical Wnt11 signaling

Cell identity and tissue morphogenesis are tightly orchestrated during organogenesis, but the mechanisms regulating this are poorly understood. We show that interactions between Wnt11 and the secreted Wnt antagonist secreted frizzled-related protein 5 (Sfrp5) coordinate cell fate and morphogenesis during Xenopus foregut development. sfrp5 is expressed in the surface cells of the foregut epithelium, whereas wnt11 is expressed in the underlying deep endoderm. Depletion of Sfrp5 results in reduced foregut gene expression and hypoplastic liver and ventral pancreatic buds. In addition, the ventral foregut cells lose adhesion and fail to form a polarized epithelium. We show that the cell fate and epithelial defects are due to inappropriate Wnt/beta-catenin and Wnt/PCP signaling, respectively, both mediated by Wnt11. We provide evidence that Sfrp5 locally inhibits Wnt11 to maintain early foregut identity and to allow an epithelium to form over a mass of tissue undergoing Wnt-mediated cell movements. This novel mechanism coordinating canonical and noncanonical Wnt signaling may have broad implications for organogenesis and cancer.

Wnt-5a-CKI{alpha} signaling promotes {beta}-catenin/E-cadherin complex formation and intercellular adhesion in human breast epithelial cells

Wnt-5a is a non-transforming Wnt protein that is implicated in cell polarity, adhesion, and motility. We have previously shown that low expression of Wnt-5a is a predictor of shorter disease-free survival in human breast cancer. Here, we investigated whether beta-catenin/E-cadherin-mediated cell-cell adhesion was affected by loss of Wnt-5a in breast carcinomas, thereby promoting a metastatic behavior of the tumor. We show that Wnt-5a stimulation of human breast epithelial cells leads to an increased Ca(2+)-dependent cell-cell adhesion. Furthermore, Wnt-5a/casein kinase Ialpha (CKIalpha)-specific Ser-45 phosphorylation of beta-catenin is associated with an increased complex formation of beta-catenin/E-cadherin. Mutation of Ser-45 decreases the beta-catenin/E-cadherin association. Also, the inhibitory effect of Wnt-5a on breast epithelial cell invasion is reduced upon mutation of beta-catenin-Ser-45. The Wnt-5a-CKIalpha-induced Ser-45 phosphorylation does not lead to degradation of beta-catenin. Finally we show that human breast cancers lacking Wnt-5a protein have a significantly lower level of membrane-associated beta-catenin. Down-regulation of Wnt-5a expression and subsequent reduction of membrane-associated beta-catenin in invasive breast cancer, can therefore contribute to a decreased cell-cell adhesion and increased motility resulting in a higher probability for metastatic disease.

Wnt-related molecules and signaling pathway equilibrium in hematopoiesis

There is near consensus that Wnt family molecules establish important gradients within niches where hematopoietic stem cells (HSC) reside. We review recent papers suggesting that a delicate balance is required between competing Wnt ligands and corresponding signaling pathways to maintain HSC integrity. Some steps in the transitions from HSC to lymphoid progenitor seem to be partially reversible and under the influence of Wnts. In addition, it has been recently suggested that HSC can oscillate between dormant versus active or lineage-biased states. We speculate that Wnts control a reflux process that may sustain stem cell self-renewal and differentiation potential.

A Wnt survival guide: from flies to human disease

It has been two decades since investigators discovered the link between the Drosophila wingless (Wg) gene and the vertebrate oncogene int-1, thus establishing the family of signaling proteins known as Wnts. Since the inception of the Wnt signaling field, there have been 19 Wnt isoforms identified in humans. These secreted glycoproteins can activate at least two distinct signaling pathways in vertebrate cells, leading to cellular changes that regulate a vast array of biological processes, including embryonic development, cell fate, cell proliferation, cell migration, stem cell maintenance, tumor suppression, and oncogenesis. In certain contexts, one subset of Wnt isoforms activates the canonical Wnt/beta-catenin pathway that is characterized by the activation of certain beta-catenin-responsive target genes in response to the binding of Wnt ligand to its cognate receptors. Similarly, a second subset of Wnt isoforms activates beta-catenin-independent pathways, including the Wnt/calcium (Wnt/Ca) pathway and the Wnt/planar cell polarity (Wnt/PCP) pathway, in certain cellular contexts. In addition, research has identified several secreted proteins known to regulate Wnt signaling, including the Dickkopf (DKK) family, secreted Frizzled-related proteins (sFRPs), and Wnt inhibitory factor-1 (WIF-1). The advent of technologies that can provide genome-wide expression data continues to implicate Wnts and proteins that regulate Wnt signaling pathways in a growing number of disease processes. The aim of this review is to provide a context on the Wnt field that will facilitate the interpretation and study of Wnt signaling in the context of human disease.

Soluble frizzled-related protein 1 is estrogen inducible in bone marrow stromal cells and suppresses the earliest events in lymphopoiesis

It has long been known that lymphopoiesis is transiently suppressed during pregnancy, which can be experimentally simulated by estrogen treatment. We now confirm with Rag1/GFP reporter mice that early lymphoid progenitors in the lineage marker(-) c-kit(high) ScaI(+), hematopoietic stem cell-enriched fraction of bone marrow are particularly depressed in these circumstances. Hematopoietic and environmental cells are both potential hormone targets and, because of this complexity, very little is known regarding mechanisms. We have now identified soluble Frizzled-related protein (sFRP)1 as an estrogen-inducible gene in stromal cells, whose expression corresponded to inability to support lymphopoiesis. Bone-lining stromal cells express sFRP1, and the transcripts were elevated by pregnancy or estrogen injection. Estrogen receptor-alpha was essential for both lymphoid suppression and induction of the sFRP family. SFRP1 has been mainly described as an antagonist for complex Wnt signals. However, we found that sFRP1, like Wnt3a, stabilized beta-catenin and blocked early lymphoid progression. Myeloerythroid progenitors were less affected by sFRP1 in culture, which was similar to estrogen with respect to lineage specificity. Hematopoietic stem cells expressed various Frizzled receptors, which markedly declined as they differentiated to lymphoid lineage. Thus, hormonal control of early lymphopoiesis in adults might partly relate to sFRP1 levels.

Wnt5A regulates expression of tumor-associated antigens in melanoma via changes in signal transducers and activators of transcription 3 phosphorylation

There are currently no effective therapies for metastatic melanoma and targeted immunotherapy results in the remission of only a very small percentage of tumors. In this study, we show that the noncanonical Wnt ligand, Wnt5A, can increase melanoma metastasis in vivo while down-regulating the expression of tumor-associated antigens important in eliciting CTL responses (e.g., MART-1, GP100, and tyrosinase). Melanosomal antigen expression is governed by MITF, PAX3, and SOX10 and is inhibited upon signal transducers and activators of transcription 3 (STAT3) activation, via decreases in PAX3 and subsequently MITF expression. Increasing Wnt5A in Wnt5A-low cells activated STAT3, and STAT3 was decreased upon Wnt5A knockdown. Downstream targets such as PAX3, MITF, and MART-1 were also affected by Wnt5A treatment or knockdown. Staining of a melanoma tissue array also highlighted the inverse relationship between MART-1 and Wnt5A expression. PKC activation by phorbol ester mimicked Wnt5A effects, and Wnt5A treatment in the presence of STAT3 or PKC inhibitors did not lower MART-1 levels. CTL activation studies showed that increases in Wnt5A correspond to decreased CTL activation and vice versa, suggesting that targeting Wnt5A before immunotherapy may lead to the enhancement of current targeted immunotherapy for patients with metastatic melanoma.

Mechanoactive tenogenic differentiation of human mesenchymal stem cells

A mesenchymal stem cell (MSC)-seeded collagen gel under static or dynamic tension is a well-established model to study the potential of MSCs in regenerating a tendon- or ligament-like tissue. Using this model, upregulation of fibrillar collagen mRNA expression and protein production has been demonstrated in response to cyclic tensile mechanical stimulation. However, the mechanisms driving MSC tenogenesis (differentiation into tendon or ligament fibroblasts) have not been elucidated. This study investigated the mechanisms of tenogenesis of human bone marrow-derived MSCs in a dynamic, three-dimensional (3D) tissue-engineering model by investigating the effects of cyclic stretching on matrix production and gene expression of candidate tendon and ligament markers. The 3D MSC tenogenesis culture system upregulated scleraxis, but cyclic stretching was required to maintain expression of this putative tendon marker over time. Enhanced tendinous neo-tissue development demonstrated with extracellular matrix staining was largely due to changes in matrix deposition and remodeling activity under dynamic loading conditions, as evidenced by differential regulation of matrix metalloproteinases at a transcriptional level with minimal changes in collagen mRNA levels. Regulation of Wnt gene expression with cyclic stimulation suggested a similar role for Wnt4 versus Wnt5a in tenogenesis as in cartilage development. This first report of the potential involvement of matrix remodeling and Wnt signaling during tenogenesis of human MSCs in a dynamic, 3D tissue-engineering model provides insights into the mechanisms of tenogenesis in a mechanoactive environment and supports the therapeutic potential of adult stem cells.

Transcriptional Profiling of Mammary Gland Side Population Cells

Similar to the bone marrow, the mammary gland contains a distinct population of Hoechst-effluxing side population cells, mammary gland side population cells (MG-SPs). To better characterize MG-SPs, their microarray gene profiles were compared to the remaining cells, which retain Hoechst dye (mammary gland non-side population cells [MG-NSPs]). For analysis, Gene Ontology (GO) that describes genes in terms of biological processes and Ontology Traverser (OT) that performs enrichment analysis were used. OT showed that MG-SP-specific genes were enriched in the GO categories of cell cycle regulation and checkpoints, multidrug-resistant transporters, organogenesis, and vasculogenesis. The MG-NSP-upregulated genes were enriched in the GO category of cellular organization and biogenesis, which includes basal epithelial markers, p63, smooth muscle actin, myosin, alpha6 integrin, cytokeratin (CK) 14, and luminal markers CK8 and CD24. Additional studies showed that a higher percentage of MG-SPs exist in the G1 phase of the cell cycle compared with the MG-NSPs. G1 cell cycle block of MG-SPs may be explained by higher expression of cell cycle-negative regulatory genes such as transforming growth factor-beta2, insulin-like growth factor binding protein-5, P18(INK4C), and wingless-5a (Wnt-5a). Accordingly, a smaller percentage of MG-SPs expressed nuclear beta-catenin, possibly as a consequence of the higher expression of Wnt-5a. In conclusion, microarray gene profiling suggests that MG-SPs are a lineage-deficient mammary gland subpopulation expressing key genes involved in cell cycle regulation, development, and angiogenesis.

Adipogenesis and WNT signalling

An inability of adipose tissue to expand consequent to exhausted capacity to recruit new adipocytes might underlie the association between obesity and insulin resistance. Adipocytes arise from mesenchymal precursors whose commitment and differentiation along the adipocytic lineage is tightly regulated. These regulatory factors mediate cross-talk between adipose cells, ensuring that adipocyte growth and differentiation are coupled to energy storage demands. The WNT family of autocrine and paracrine growth factors regulates adult tissue maintenance and remodelling and, consequently, is well suited to mediate adipose cell communication. Indeed, several recent reports, summarized in this review, implicate WNT signalling in regulating adipogenesis. Manipulating the WNT pathway to alter adipose cellular makeup, therefore, constitutes an attractive drug-development target to combat obesity-associated metabolic complications.

Wnt signaling controls the fate of mesenchymal stem cells

Multipotential mesenchymal stem cells (MSCs) are able to differentiate along several known lineages and have been shown to be efficacious for in vivo wound repair. The growth and differentiation of MSCs are known to be tightly regulated via interactions with specific extracellular mediators. Recent studies have shown that Wnts and their downstream signaling pathways play an important role in the self-renewal and differentiation of MSCs. Indeed altered bone-mass is known to result from mutations in LRP5, a Wnt co-receptor, that suggests Wnt plays an important signaling role during bone formation, possibly involving MSCs. This review outlines the current understanding of the distinct Wnt intracellular pathways including both canonical beta-catenin/TCF(LEF1) signaling and non-canonical cascades mediated by JNK, PKC, Ca(2+) or Rho, and how they are involved in the regulation of MSC proliferation and differentiation. We also discuss the coordination between different Wnt signaling cascades to precisely control MSC cell fate decisions, and we dissect the functional cross-talk of Wnt signaling that is known to occur with other growth factor signaling pathways.

Hexachlorophene suppresses beta-catenin expression by up-regulation of Siah-1 in EBV-infected B lymphoma cells

Many studies have shown that the activation of β-catenin signaling can promote oncogenesis, and it is therefore of interest to find agents that modulate this pathway. Recent work has shown using B lymphoma cells that infection by Epstein–Barr virus (EBV) and expression of its latent membrane protein (LMP)-1, cause increases in the expression of β-catenin and cellular transformation. Conversely, results from cell-based small molecule screening studies have shown that the antibiotic hexachlorophene can down-regulate β-catenin in colon cancer cells. Here we report that hexachlorophene also counteracts the elevated β-catenin levels in EBV-infected B lymphomas. This is associated with restoration in levels of Siah-1 (an E3 ubiquitin ligase that is active in β-catenin regulation) which had been diminished by LMP-1. Our results suggest that Siah-1 is targeted by both LMP-1 and hexachlorophene with opposite effects. The hexachlorophene modulation of Siah-1 and β-catenin is independent of p53 and results in reduced expression of cyclin-D1 and c-Myc (target genes of β-catenin), leading to the growth arrest of B lymphoma cells. From these results we propose that hexachlorophene may provide a novel therapeutic strategy for EBV-infected B lymphoma cells by reducing β-catenin levels via the restoration of Siah-1.

Wnt5a is essential for intestinal elongation in mice

Morphogenesis of the mammalian small intestine entails extensive elongation and folding of the primitive gut into a tightly coiled digestive tube. Surprisingly, little is known about the cellular and molecular mechanisms that mediate the morphological aspects of small intestine formation. Here, we demonstrate that Wnt5a, a member of the Wnt family of secreted proteins, is essential for the development and elongation of the small intestine from the midgut region. We found that the small intestine in mice lacking Wnt5a was dramatically shortened and duplicated, forming a bifurcated lumen instead of a single tube. In addition, cell proliferation was reduced and re-intercalation of post-mitotic cells into the elongating gut tube epithelium was disrupted. Thus, our study demonstrates that Wnt5a functions as a critical regulator of midgut formation and morphogenesis in mammals.

Amino acid limitation induces down-regulation of WNT5a at transcriptional level

An aberrant WNT signaling contributes to the development and progression of multiple cancers. WNT5a is one of the WNT signaling molecules. This study was designed to test the hypothesis that amino acid deprivation induces changes in the WNT signaling pathway in colon cancer cells. Results showed that targets of the amino acid response pathway, ATF3 and p21, were induced in the human colon cancer cell line SW480 during amino acid limitation. There was a significant decrease in the WNT5a mRNA level following amino acid deprivation. The down-regulation of WNT5a mRNA by amino acid deprivation is not due to mRNA destabilization. There is a reduction of nuclear beta-catenin protein level by amino acid limitation. Under amino acid limitation, phosphorylation of ERK1/2 was increased and the blockage of ERK1/2 by the inhibitor U0126 partially restored WNT5a mRNA level. In conclusion, amino acid limitation in colon cancer cells induces phosphorylation of ERK1/2, which then down-regulates WNT5a expression.

Contrasting responses of lymphoid progenitors to canonical and noncanonical Wnt signals

The Wnt family of secreted glycoproteins has been implicated in many aspects of development, but its contribution to blood cell formation is controversial. We overexpressed Wnt3a, Wnt5a, and Dickkopf 1 in stromal cells from osteopetrotic mice and used them in coculture experiments with highly enriched stem and progenitor cells. The objective was to learn whether and how particular stages of B lymphopoiesis are responsive to these Wnt family ligands. We found that canonical Wnt signaling, through Wnt3a, inhibited B and plasmacytoid dendritic cell, but not conventional dendritic cell development. Wnt5a, which can oppose canonical signaling or act through a different pathway, increased B lymphopoiesis. Responsiveness to both Wnt ligands diminished with time in culture and stage of development. That is, only hematopoietic stem cells and very primitive progenitors were affected. Although Wnt3a promoted retention of hematopoietic stem cell markers, cell yields and dye dilution experiments indicated it was not a growth stimulus. Other results suggest that lineage instability results from canonical Wnt signaling. Lymphoid progenitors rapidly down-regulated RAG-1, and some acquired stem cell-staining characteristics as well as myeloid and erythroid potential when exposed to Wnt3a-producing stromal cells. We conclude that at least two Wnt ligands can differentially regulate early events in B lymphopoiesis, affecting entry and progression in distinct differentiation lineages.

Wnts acting through canonical and noncanonical signaling pathways exert opposite effects on hippocampal synapse formation

Background

Wnt proteins comprise a large class of signaling molecules that regulate a variety of developmental processes, including synapse formation. Previous studies have shown Wnts to be involved in both the induction and prevention of synapses in a number of different organisms. However, it is not clear whether the influence of Wnts on synapses is a result of Wnts' behavior in different organisms or differences in the activity of different Wnt ligands.

Results

We used in situ hybridization to show that several Wnt ligands (Wnt3, Wnt5a, Wnt7a, and Wnt7b) and their receptors, Frizzled, are expressed in the developing hippocampus during the period of synapse formation in rodents. We used recombinant Wnt protein or Wnt conditioned media to explore the effects of Wnts on synapses in hippocampal cultures. We found that Wnt7a and Wnt7b activate canonical signaling, whereas Wnt5a activates a noncanonical pathway. The activation of the canonical pathway, either through pathway manipulations or through Wnt stimulation, increases presynaptic inputs. In contrast, exposure to Wnt5a, which activates a noncanonical signaling pathway, decreases the number of presynaptic terminals.

Conclusion

Our observations suggest that the pro- and antisynaptogenic effects of Wnt proteins are associated with the activation of the canonical and noncanonical Wnt signaling pathways.

Dissection of sets of genes that control the character of wnt5a-deficient mouse calvarial cells

Wnts (wingless and int-related proteins) are a family of secreted cysteine-rich glycoproteins, expressed in a variety of tissues in developing embryos, thought to be involved in cell fate specification and stem cell commitment. To identify the specific Wnts involved in osteoblastic differentiation of human mesenchymal stem cells (hMSCs), we performed degenerative RT-PCR cloning method to amplify Wnt-encoding cDNAs expressed during osteoblastic differentiation of hMSCs in vitro and during hMSC-directed ectopic osteogenesis in the severe combined immunodeficient (SCID) mouse host. WNT5A was found to be the dominant Wnt expressed during osteoblastic differentiation of hMSCs both in vitro and in vivo. RT-PCR further revealed that hWNT5A and its receptor Frizzled family member 5 (hFZD5) was up-regulated during osteoblastic differentiation compared to uncommitted hMSCs. To evaluate the function of Wnt5a, calvarial cells were obtained from Wnt5a(-/-), Wnt5a(+/-), and wild type mice. Wnt5a(-/-) cells showed significantly slower growth when compared to Wnt5a(+/-) and wild type cells. Gene expression profiles of the Wnt5a(-/-) calvarial cells as compared to wild type cells were evaluated using microarray analysis. 255 genes exhibited at least 2-fold changes in expression. Clusters of genes regulating cell cycle, cell proliferation and cell growth, and gene transcription were altered with absence of Wnt5a expression. In addition, genes regulating osteoblastic differentiation including Runx2, osterix, and alkaline phosphatase (ALP) were shown to be down-regulated in Wnt5a(-/-) cells. In conclusion, Wnt5a is highly expressed during osteoblastic differentiation. Its function during mesenchymal stem cell differentiation as well as cell growth was suggested by comparing the gene expression profile of calvarial cells from the Wnt5a(-/-) and wild type mice.

Wnt5a regulates directional cell migration and cell proliferation via Ror2-mediated noncanonical pathway in mammalian palate development

Tissue and molecular heterogeneities are present in the developing secondary palate along the anteroposterior (AP) axis in mice. Here, we show that Wnt5a and its receptor Ror2 are expressed in a graded manner along the AP axis of the palate. Wnt5a deficiency leads to a complete cleft of the secondary palate, which exhibits distinct phenotypic alterations at histological, cellular and molecular levels in the anterior and posterior regions of the palate. We demonstrate that there is directional cell migration within the developing palate. In the absence of Wnt5a, this directional cell migration does not occur. Genetic studies and in vitro organ culture assays further demonstrate a role for Ror2 in mediating Wnt5a signaling in the regulation of cell proliferation and migration during palate development. Our results reveal distinct regulatory roles for Wnt5a in gene expression and cell proliferation along the AP axis of the developing palate, and an essential role for Wnt5a in the regulation of directional cell migration.

WNT5A expression increases during melanoma progression and correlates with outcome

PURPOSE

Wnt ligands play a major role in development and are important in cancer. Expression microarray analysis correlates one member of this family, WNT5A, to a subclass of melanomas with increased motility and invasion. There are no large studies of clinical samples primarily addressing the importance of WNT5A in melanoma progression or outcome. Therefore, this study aimed to assess the protein expression of WNT5A during melanoma progression and its effect on outcome.

EXPERIMENTAL DESIGN

Expression of WNT5A was determined in a series of 59 primary melanomas with matched metastases. To provide a benchmark of progression against which to assess WNT5A, expression of p16(ink4a) was analyzed, as this has been previously well documented in melanoma. The effect of WNT5A protein expression on outcome was assessed in 102 melanomas.

RESULTS

Cytoplasmic WNT5A showed a trend of increasing expression with melanoma progression (P = 0.013), whereas there was diminishing p16(ink4a) expression (P = 0.006). Nevi showed relatively strong WNT5A expression. Strong cytoplasmic WNT5A was an independent risk factor for reduced metastasis-free and overall survival in multivariate analysis (P = 0.001 and 0.003, respectively).

CONCLUSION

Cytoplasmic WNT5A increases with melanoma progression and strong expression is associated with poor outcome.

CaSR stimulates secretion of Wnt5a from colonic myofibroblasts to stimulate CDX2 and sucrase-isomaltase using Ror2 on intestinal epithelia

To understand whether extracellular calcium-sensing receptor (CaSR) expression on colonic myofibroblast cells (18Co) contributed to epithelial homeostasis, we activated the CaSR with 5 mM Ca(2+), screened by RT-PCR Wnt family members, and measured their secretion. Transcripts for Wnt 1, 2, 2b, 3a, 4, and 7a were either absent or unchanged whereas Wnt3 decreased and Wnt5a increased. We assessed Wnt5a secretion by Western blot. High Ca(2+) (5 mM) substantially increased Wnt5a secretion; small interfering RNA (siRNA) against the CaSR reduced this to constitutive amounts. Expression of Wnt5a plasmid but not Wnt1 or Wnt3a increased caudal homeodomain factor CDX2 transcripts and protein in HT-29 adenocarcinoma cells. Wnt5a increased activity of a sucrase-isomaltase (SI) promoter in Caco-2BBE cells. Wnt5a protein stimulation of CDX2 transcripts and protein and SI reporter were increased by overexpression of wild-type Ror2, a Wnt5a receptor, and reduced with siRNA against Ror2. CaSR activation of HT-29 cells increased Ror2 protein expression. Ror2 protein was expressed in mouse jejunum from crypt base to villus tip and in the colon on surface epithelia. Our results show that activation of a G protein-coupled receptor, the CaSR, stimulates secretion of Wnt5a from myofibroblasts. Stimulation of epithelia by the CaSR increased the expression of a receptor for Wnt5a, the tyrosine kinase Ror2, suggesting existence of a unique paracrine relationship for CDX2 homoeostasis in the intestine and revealing new contributions of CaSR-activated myofibroblasts to intestinal stem cell niche microenvironments.

Mesodermal fate decisions of a stem cell: the Wnt switch

Stem cells are a powerful resource for cell-based transplantation therapies in osteodegenerative disorders, but before some kinds of stem cells can be applied clinically, several aspects of their expansion and differentiation need to be better controlled. Wnt molecules and members of the Wnt signaling cascade have been ascribed a role in both these processes in vitro as well as normal development in vivo. However some results are controversial. In this review we will present the hypothesis that both canonical and non-canonical signaling are involved in mesenchymal cell fate regulation, such as adipogenesis, chondrogenesis and osteogenesis, and that in vitro it is a timely switch between the two that specifies the identity of the differentiating cell. We will specifically focus on the in vitro differentiation of adipocytes, chondrocytes and osteoblasts contrasting embryonic and mesenchymal stem cells as well as the role of Wnts in mesenchymal fate specification during embryogenesis.

Rogue proliferation versus restorative protection: where do we draw the line for Wnt and forkhead signaling?

BACKGROUND

Disease entities such as diabetes, neurodegeneration and cardiovascular disorders affect a significant portion of the world's population.

OBJECTIVE

Given that cellular survival and longevity in multiple disorders are tied to oxidative stress, apoptotic cell injury and immune system deregulation, the development of robust therapeutic strategies rests heavily upon the ability to balance each of these parameters.

METHODS

Here we discuss two exciting signaling pathways, namely Wnt and mammalian forkhead transcription factors predominantly of the O class superfamily, which can share integrated cytoprotective pathways during oxidative stress but may also adversely influence cellular survival and promote cancer cell proliferation.

CONCLUSION

Future investigations must elucidate the cellular determinants that govern the ability of Wnt and forkhead proteins to promote cellular longevity and possible disease remission but also allow for detrimental biological consequences and clinical compromise.

WNT signaling affects gene expression in the ventral diencephalon and pituitary gland growth

We examined the role of WNT signaling in pituitary development by characterizing the pituitary phenotype of three WNT knockout mice and assessing the expression of WNT pathway components. Wnt5a mutants have expanded domains of Fgf10 and bone morphogenetic protein expression in the ventral diencephalon and a reduced domain of LHX3 expression in Rathke's pouch. Wnt4 mutants have mildly reduced cell differentiation, reduced POU1F1 expression, and mild anterior lobe hypoplasia. Wnt4, Wnt5a double mutants exhibit an additive pituitary phenotype of dysmorphology and mild hypoplasia. Wnt6 mutants have no obvious pituitary phenotype. We surveyed WNT expression and identified transcripts for numerous Wnts, Frizzleds, and downstream pathway members in the pituitary and ventral diencephalon. These findings support the emerging model that WNT signaling affects the pituitary gland via effects on ventral diencephalon signaling, and suggest additional Wnt genes that are worthy of functional studies.

Brachy-syndactyly caused by loss of Sfrp2 function

Wnt signaling pathways are regulated both at the intracellular and extracellular levels. During embryogenesis, the in vivo effects of the secreted frizzled-related protein (Sfrp) family of Wnt inhibitors are poorly understood. Here, we show that inactivation of Sfrp2 results in subtle limb defects in mice with mesomelic shortening and consistent shortening of all autopodal elements that is clinically manifested as brachydactyly. In addition, there is soft-tissue syndactyly of the hindlimb. The brachydactyly is caused by decreased chondrocyte proliferation and delayed differentiation in distal limb chondrogenic elements. These data suggest that Sfrp2 can regulate both chondrogenesis and regression of interdigital mesenchyme in distal limb. Sfrp2 can also repress canonical Wnt signaling by Wnt1, Wnt9a, and Wnt4 in vitro. Sfrp2-/- and TOPGAL/Sfrp2-/- mice have a mild increase in beta-catenin and beta-galactosidase staining, respectively, in some phalangeal elements. This however does not exclude a potential concurrent effect on non-canonical Wnt signaling in the growth plate. In combination with what is known about BMP and Wnt signaling in human brachydactylies, our data establish a critical role for Sfrp2 in proper distal limb formation and suggest SFPR2 could be a novel candidate gene for human brachy-syndactyly defects.

Variable DNA methylation patterns associated with progression of disease in hepatocellular carcinomas

Hepatocellular carcinoma (HCC) most commonly arises from chronic inflammation due to viral infection, as a result of genetic and epigenetic abnormalities. A global picture of epigenetic changes in HCC is lacking. We used methylated CpG island amplification microarrays (MCAMs) to study 6458 CpG islands in HCC and adjacent preneoplastic tissues [chronic hepatitis (CH) or liver cirrhosis (LC)] in comparison with normal liver tissues where neither viral infection nor hepatitis has existed. MCAM identified 719 (11%) prominent genes of hypermethylation in HCCs. HCCs arising from LC had significantly more methylation than those arising from CH (1249 genes or 19% versus 444 genes or 7%, P < 0.05). There were four patterns of aberrant methylation: Type I (4%, e.g. matrix metalloproteinase 14) shows a substantially high methylation level in adjacent tissue and does not increase further in cancer. Type II (55%, e.g. RASSF1A) shows progressively increasing methylation from adjacent tissue to HCC. Type III (4%, e.g. GNA14) shows decreased methylation in adjacent tissue but either similar or increased methylation in HCC. Type IV (37%, e.g. CDKN2A) shows low levels of methylation in normal tissue and adjacent tissue but high levels in HCC. These DNA methylation changes were confirmed by quantitative pyrosequencing methylation analysis in representative 24 genes and were analyzed for correlation with clinicopathological parameters in 38 patients. Intriguingly, methylation in the Type IV genes is characteristic of moderately/poorly differentiated cancer. Our global epigenome analysis reveals distinct patterns of methylation that are probably to represent different pathophysiologic processes in HCCs.

Expression of Wnt-5a and its clinicopathological significance in hepatocellular carcinoma

BACKGROUND

The functions of Wnt-5a in human cancers are controversial and unclear.

AIM

To investigate the clinical significance of Wnt-5a expression in hepatocellular carcinoma.

PATIENTS AND METHODS

Real-time quantitative Reverse transcriptase Polymerase Chain Reaction was done to evaluate Wnt-5a gene expression. Wnt-5a, beta-catenin, E-cadherin and Ki-67 were examined immunohistochemically in 114 hepatocellular carcinoma cases.

RESULTS

Compared to normal tissue, Wnt-5a mRNA expression was clearly increased in hepatocellular carcinoma, chronic hepatitis and cirrhosis. On immunohistochemistry, immunostaining of Wnt-5a showed a bell-shaped pattern: low to undetectable levels were present in normal tissue and in tumour samples, whereas strong immunostaining was seen in chronic hepatitis, cirrhosis and dysplastic liver cells. Reduction or loss of Wnt-5a protein expression was found in 80.7% of hepatocellular carcinoma cases (n=92) and was significantly associated with higher tumour stage (p<0.001), serum AFP level (p=0.025), low membranous expression of E-cadherin (p<0.0001) and beta-catenin (p=0.036) and high Ki-67 labelling indices (LIs, p=0.001).

CONCLUSION

Wnt-5a mRNA and protein levels are higher than normal in hepatitis and cirrhosis and appear to be related to the presence of hepatitis B virus infection. However, Wnt-5a protein expression is frequently lost in hepatocellular carcinoma; this supports the notion that this protein has a tumour suppressor function in hepatocellular carcinoma.