cis-regulatory architecture of a short-range EGFR organizing center in the Drosophila melanogaster leg

We characterized the establishment of an Epidermal Growth Factor Receptor (EGFR) organizing center (EOC) during leg development in Drosophila melanogaster. Initial EGFR activation occurs in the center of leg discs by expression of the EGFR ligand Vn and the EGFR ligand-processing protease Rho, each through single enhancers, vnE and rhoE, that integrate inputs from Wg, Dpp, Dll and Sp1. Deletion of vnE and rhoE eliminates vn and rho expression in the center of the leg imaginal discs, respectively. Animals with deletions of both vnE and rhoE (but not individually) show distal but not medial leg truncations, suggesting that the distal source of EGFR ligands acts at short-range to only specify distal-most fates, and that multiple additional ‘ring’ enhancers are responsible for medial fates. Further, based on the cis-regulatory logic of vnE and rhoE we identified many additional leg enhancers, suggesting that this logic is broadly used by many genes during Drosophila limb development.

The EGFR signaling pathway plays a major role in innumerable developmental processes in all animals and its deregulation leads to different types of cancer, as well as many other developmental diseases in humans. Here we explored the integration of inputs from the Wnt- and TGF-beta signaling pathways and the leg-specifying transcription factors Distal-less and Sp1 at enhancer elements of EGFR ligands. These enhancers trigger a specific EGFR-dependent developmental output in the fly leg that is limited to specifying distal-most fates. Our findings suggest that activation of the EGFR pathway during fly leg development occurs through the activation of multiple EGFR ligand enhancers that are active at different positions along the proximo-distal axis. Similar enhancer elements are likely to control EGFR activation in humans as well. Such DNA elements might be ‘hot spots’ that cause formation of EGFR-dependent tumors if mutations in them occur. Thus, understanding the molecular characteristics of such DNA elements could facilitate the detection and treatment of cancer.

18β-glycyrrhetinic acid suppresses gastric cancer by activation of miR-149-3p-Wnt-1 signaling

18β-glycyrrhetinic acid (GRA) exerts anti-tumor effects on various types of cancer. In the present study, we found that GRA attenuated the severity of gastritis and suppressed gastric tumorigenesis in transgenic mice. We also discovered that miR-149-3p was downregulated in gastric cancer tissues and cell lines as compared to normal gastric tissues and epithelial cells, but was upregulated by GRA. miR-149-3p expression also correlated negatively with lymphnode metastasis. Our functional assays showed that miR-149-3p overexpression inhibited cell proliferation and cell cycle progression while inducing apoptosis, while inhibition of miR-149-3p had the opposite effects. In addition, we identified Wnt-1 as a direct target of miR-149-3p. These data suggest that GRA inhibits the initiation and progression of gastric tumors by ameliorating the inflammatory microenvironment through downregulation of COX-2 expression and by inhibiting Wnt-1 expression through the upregulation of tumor suppressor miR-149-3p. GRA may thus have the potential to serve as a useful therapeutic agent for the prevention and treatment of gastric cancer.

Wnt5a suppresses tumor formation and redirects tumor phenotype in MMTV-Wnt1 tumors

Wnt5a is a non-canonical signaling Wnt that has been implicated in tumor suppression. We previously showed that loss of Wnt5a in MMTV-PyVmT tumors resulted in a switch in tumor phenotype resulting in tumors with increased basal phenotype and high Wnt/β-catenin signaling. The object of this study was to test the hypothesis that Wnt5a can act to inhibit tumors formed by activation of Wnt/β-catenin signaling. To this end, we characterized tumor and non-tumor mammary tissue from MMTV-Wnt1 and double transgenic MMTV-Wnt1;MMTV-Wnt5a mice. Wnt5a containing mice demonstrated fewer tumors with increased latency when compared to MMTV-Wnt1 controls. Expression of markers for basal-like tumors was down-regulated in the tumors that formed in the presence of Wnt5a indicating a phenotypic switch. Reduced canonical Wnt signaling was detected in double transgenic tumors as a decrease in active β-catenin protein and a decrease in Axin2 mRNA transcript levels. In non-tumor tissues, over-expression of Wnt5a in MMTV-Wnt1 mammary glands resulted in attenuation of phenotypes normally observed in MMTV-Wnt1 glands including hyperbranching and increased progenitor and basal cell populations. Even though Wnt5a could antagonize Wnt/β-catenin signaling in primary mammary epithelial cells in culture, reduced Wnt/β-catenin signaling was not detected in non-tumor MMTV-Wnt1;Wnt5a tissue in vivo. The data demonstrate that Wnt5a suppresses tumor formation and promotes a phenotypic shift in MMTV-Wnt1 tumors.

Inducible progenitor-derived Wingless regulates adult midgut regeneration in Drosophila

The ability to regenerate following stress is a hallmark of self-renewing tissues. However, little is known about how regeneration differs from homeostatic tissue maintenance. Here, we study the role and regulation of Wingless (Wg)/Wnt signalling during intestinal regeneration using the Drosophila adult midgut. We show that Wg is produced by the intestinal epithelial compartment upon damage or stress and it is exclusively required for intestinal stem cell (ISC) proliferation during tissue regeneration. Reducing Wg or downstream signalling components from the intestinal epithelium blocked tissue regeneration. Importantly, we demonstrate that Wg from the undifferentiated progenitor cell, the enteroblast, is required for Myc-dependent ISC proliferation during regeneration. Similar to young regenerating tissues, ageing intestines required Wg and Myc for ISC hyperproliferation. Unexpectedly, our results demonstrate that epithelial but not mesenchymal Wg is essential for ISC proliferation in response to damage, while neither source of the ligand is solely responsible for ISC maintenance and tissue self-renewal in unchallenged tissues. Therefore, fine-tuning Wnt results in optimal balance between the ability to respond to stress without negatively affecting organismal viability.

Wnt1 expression temporally allocates upper rhombic lip progenitors and defines their terminal cell fate in the cerebellum

The cerebellum (Cb) controls movement related physiology using a diverse array of morphologically and biochemically distinct neurons. During development, the Cb is derived from rhombomere 1 (r1), an embryonic compartment patterned by a signaling center referred to as the isthmus organizer. The secreted glycoprotein WNT1 is expressed in the midbrain primordia (mesencephalon, mes) and at the posterior limit of the mes. WNT1 plays a pivotal role in maintaining the isthmus organizer and mutations in Wnt1 produce severe Cb defects that are generally attributed to aberrant organizer activity. Interestingly, Wnt1 is also expressed at the most posterior limit of dorsal r1, in a region known as the upper rhombic lip (URL). However, the distribution and molecular identity of Wnt1 expressing progenitors have not been carefully described in r1. We used Wnt1-Venus transgenic mice to generate a molecular map of Wnt1 expressing progenitors in relation to other well characterized Cb biomarkers such as MATH1 (ATOH1), LMX1a and OTX2. Our analysis validated Wnt1 expression in the URL and revealed molecularly-defined developmental zones in r1. We then used genetic inducible fate mapping (GIFM) to link transient Wnt1 expression in r1 to terminal cell fates in the mature Cb. Wnt1 expressing progenitors primarily contributed to neurons in deep cerebellar nuclei, granule cells, and unipolar brush cells in distinct but overlapping temporal windows and sparsely contributed to inhibitory neurons and Bergmann glia. We further demonstrate that the Wnt1 lineage does not follow a competency model of progressive lineage restriction to generate the Cb or the functionally related precerebellar system. Instead, progenitors initiate Wnt1 expression de novo to give rise to each Cb cell type and precerebellar nuclei. We also used GIFM to determine how the temporal control of Wnt1 expression is related to molecular identity and cell migration in Cb development. Our findings provide new insight into how lineage and timing establish cell diversity within the Cb system.

Wnt1 and BMP2: two factors recruiting multipotent neural crest progenitors isolated from adult bone marrow

Recent studies have shown that neural crest-derived progenitor cells can be found in diverse mammalian tissues including tissues that were not previously shown to contain neural crest derivatives, such as bone marrow. The identification of those "new" neural crest-derived progenitor cells opens new strategies for developing autologous cell replacement therapies in regenerative medicine. However, their potential use is still a challenge as only few neural crest-derived progenitor cells were found in those new accessible locations. In this study, we developed a protocol, based on wnt1 and BMP2 effects, to enrich neural crest-derived cells from adult bone marrow. Those two factors are known to maintain and stimulate the proliferation of embryonic neural crest stem cells, however, their effects have never been characterized on neural crest cells isolated from adult tissues. Using multiple strategies from microarray to 2D-DIGE proteomic analyses, we characterized those recruited neural crest-derived cells, defining their identity and their differentiating abilities.

Spatiotemporally modulated Vestigial gradient by Wingless signaling adaptively regulates cell division for precise wing size control

In animal development, the growth of a tissue or organ is timely arrested when it reaches the stereotyped correct size. How this is robustly controlled remains poorly understood. The prevalent viewpoint, which is that morphogen gradients, due to their organizing roles in development, are directly responsible for growth arrest, cannot explain a number of observations. Recent findings from studies of the Drosophila wing have revealed that the interpretation of the Wingless gradient requires signaling-induced self-inhibition and that cell proliferation is controlled by graded vestigial expression. These findings highlight a growth control mechanism that involves Wingless regulated vestigial expression, but a question is whether they can quantitatively explain the observed precision and robustness of wing size control. Quantitative and systematic investigation into Wingless signaling using a mathematical model has elucidated two points. First, negative regulation of the Vestigial gradient by Wingless signaling makes vestigial expression precise and robust. Second, weak Wingless signaling in a primarily small wing pouch causes a short and steep Vestigial gradient, which stimulates more cell divisions and leads to a significant expansion of the wing pouch; however, strong Wingless signaling in a primarily large wing pouch causes a long and smooth Vestigial gradient, which stimulates fewer cell divisions and results in a slight expansion of the wing pouch. These results substantially decipher an inherent mechanism of tissue and organ size control. Our model explains, and is supported by, a number of experimental observations.

Wnt1, FoxO3a, and NF-kappaB oversee microglial integrity and activation during oxidant stress

Elucidating the underlying mechanisms that govern microglial activation and survival is essential for the development of new treatment strategies for neurodegenerative disorders, since microglia serve not only as guardian sentries of the nervous system, but also play a significant role in determining neuronal and vascular cell fate. Here we show that endogenous and exogenous Wnt1 in inflammatory microglial cells is necessary for the prevention of apoptotic early membrane phosphatidylserine exposure and later DNA degradation, since blockade of Wnt1 signaling abrogates cell survival during oxidative stress. Wnt1 prevents apoptotic demise through the post-translational phosphorylation and maintenance of FoxO3a in the cytoplasm to inhibit an apoptotic cascade that relies upon the loss of mitochondrial membrane permeability, cytochrome c release, Bad phosphorylation, and activation of caspase 3 and caspase 1 as demonstrated by complimentary gene knockdown studies of FoxO3a. Furthermore, subcellular trafficking and gene knockdown studies of NF-kappaB p65 illustrate that microglial cell survival determined by Wnt1 during oxidative stress requires NF-kappaB p65. Our work highlights Wnt1 and the control of novel downstream transcriptional pathways as critical components for the oversight of nervous system microglial cells.

Pea3 transcription factors and wnt1-induced mouse mammary neoplasia

The role of the PEA3 subfamily of Ets transcription factors in breast neoplasia is controversial. Although overexpression of PEA3 (E1AF/ETV4), and of the related factors ERM (ETV5) and ER81 (ETV1), have been observed in human and mouse breast tumors, PEA3 factors have also been ascribed a tumor suppressor function. Here, we utilized the MMTV/Wnt1 mouse strain to further interrogate the role of PEA3 transcription factors in mammary tumorigenesis based on our previous observation that Pea3 is highly expressed in MMTV/Wnt1 mammary tumors. Pea3 expression in mouse mammary tissues was visualized using a Pea3^NLSlacZ reporter strain. In normal mammary glands, Pea3 expression is predominantly confined to myoepithelial cells. Wnt1 transgene expression induced marked amplification of this cell compartment in nontumorous mammary glands, accompanied by an apparent increase in Pea3 expression. The pattern of Pea3 expression in MMTV/Wnt1 mammary glands recapitulated the cellular profile of activated β-catenin/TCF signaling, which was visualized using both β-catenin immunohistochemistry and the β-catenin/TCF-responsive reporter Axin2^NLSlacZ. To test the requirement for PEA3 factors in Wnt1-induced tumorigenesis, we employed a mammary-targeted dominant negative PEA3 transgene, ΔNPEA3En. Expression of ΔNPEA3En delayed early-onset tumor formation in MMTV/Wnt1 virgin females (P = 0.03), suggesting a requirement for PEA3 factor function for Wnt1-driven tumor formation. Consistent with this observation, expression of the ΔNPEA3En transgene was profoundly reduced in mammary tumors compared to nontumorous mammary glands from bigenic MMTV/Wnt1, MMTV/ΔNPEA3En mice (P = 0.01). Our data provide the first description of Wnt1-mediated expansion of the Pea3-expressing myoepithelial compartment in nontumorous mammary glands. Consistent with this observation, mammary myoepithelium was selectively responsive to Wnt1. Together these data suggest the MMTV/Wnt1 strain as a potential model of basal breast cancer. Furthermore, this study provides evidence for a protumorigenic role of PEA3 factors in breast neoplasia, and supports targeting the PEA3 transcription factor family in breast cancer.

Stromal cell-derived factor-1/CXCL12 contributes to MMTV-Wnt1 tumor growth involving Gr1+CD11b+ cells

Background

Histological examinations of MMTV-Wnt1 tumors reveal drastic differences in the tumor vasculature when compared to MMTV-Her2 tumors. However, these differences have not been formally described, nor have any angiogenic factors been implicated to be involved in the Wnt1 tumors.

Methodology/Principal Findings

Here, we show that MMTV-Wnt1 tumors were more vascularized than MMTV-Her2 tumors, and this correlated with significantly higher expression of a CXC chemokine, stromal cell-derived factor-1 (SDF1/CXCL12) but not with VEGFA. Isolation of various cell types from Wnt1 tumors revealed that SDF1 was produced by both tumor myoepithelial cells and stromal cells, whereas Her2 tumors lacked myoepithelial cells and contained significantly less stroma. The growth of Wnt1 tumors, but not Her2 tumors, was inhibited by a neutralizing antibody to SDF1, but not by neutralization of VEGFA. Anti-SDF1 treatment decreased the proportion of infiltrating Gr1⁺ myeloid cells in the Wnt1 tumors, which correlated with a decrease in the percentage of endothelial cells. The involvement of Gr1⁺ cells was evident from the retardation of Wnt1 tumor growth following in vivo depletion of these cells with an anti-Gr1-specific antibody. This degree of inhibition on Wnt1 tumor growth was comparable, but not additive, to the effect observed with anti-SDF1, indicative of overlapping mechanisms of inhibition. In contrast, Her2 tumors were not affected by the depletion of Gr1⁺ cells.

Conclusions/Significance

We demonstrated that SDF1 is important for Wnt1, but not for HER2, in inducing murine mammary tumor and the role of SDF1 in tumorigenesis involves Gr1⁺ myeloid cells to facilitate growth and/or angiogenesis.

Heparan sulfate deficiency leads to Peters anomaly in mice by disturbing neural crest TGF-beta2 signaling

During human embryogenesis, neural crest cells migrate to the anterior chamber of the eye and then differentiate into the inner layers of the cornea, the iridocorneal angle, and the anterior portion of the iris. When proper development does not occur, this causes iridocorneal angle dysgenesis and intraocular pressure (IOP) elevation, which ultimately results in developmental glaucoma. Here, we show that heparan sulfate (HS) deficiency in mouse neural crest cells causes anterior chamber dysgenesis, including corneal endothelium defects, corneal stroma hypoplasia, and iridocorneal angle dysgenesis. These dysfunctions are phenotypes of the human developmental glaucoma, Peters anomaly. In the neural crest cells of mice embryos, disruption of the gene encoding exostosin 1 (Ext1), which is an indispensable enzyme for HS synthesis, resulted in disturbed TGF-beta2 signaling. This led to reduced phosphorylation of Smad2 and downregulated expression of forkhead box C1 (Foxc1) and paired-like homeodomain transcription factor 2 (Pitx2), transcription factors that have been identified as the causative genes for developmental glaucoma. Furthermore, impaired interactions between HS and TGF-beta2 induced developmental glaucoma, which was manifested as an IOP elevation caused by iridocorneal angle dysgenesis. These findings suggest that HS is necessary for neural crest cells to form the anterior chamber via TGF-beta2 signaling. Disturbances of HS synthesis might therefore contribute to the pathology of developmental glaucoma.

Expression and clinical significance of Wnt-1 and beta-catenin in nasopharyngeal carcinoma

BACKGROUND AND OBJECTIVE

As signaling molecule and key component of Wnt/beta-catenin signaling pathway respectively, Wnt-1 and beta-catenin are abnormally expressed in several malignancies and correlate with poor prognosis. This study was to investigate the expression and clinical significance of Wnt-1 and beta-catenin in nasopharyngeal carcinoma (NPC).

METHODS

The expression of Wnt-1 and beta-catenin in 111 specimens of NPC was detected by SP immunohistochemistry. Their correlations to relapse-free survival (RFS), metastasis-free survival (MFS) and progression-free survival (PFS) were analyzed.

RESULTS

The high expression of beta-catenin was observed in 64 (57.7%) of the 111 cases. Its high expression rate was significantly higher in advanced NPC than in early stage NPC (63.1% vs. 40.7%, p = 0.041). The RFS, MFS and PFS were lower in high beta-catenin expression group than in low beta-catenin expression group (p < 0.05). Cox regression analysis demonstrated that beta-catenin was related to poor prognosis of NPC patients. The high expression of Wnt-1 was observed in 68 (61.3%) of the 111 cases, but its expression had no effect on RFS, MFS and PFS (p > 0.05).

CONCLUSIONS

Wnt/beta-catenin signaling pathway may be activated abnormally in some NPC patients. beta-catenin may be a prognostic factor of NPC.

A synthetic peptide corresponding to residues 301-320 of human Wnt-1 promotes PC12 cell adhesion and hippocampal neural stem cell differentiation

Wnt signaling cascades play a crucial role in the maintenance of stem cell niches in many tissues as well as in embryonic patterning and cell-fate determination. Wnt signaling pathways have been well studied; however, the precise binding mechanism of Wnt protein to its receptor has not yet been clarified. Here we show the design and synthesis of seven novel peptide candidates for a receptor-binding site of human Wnt-1 based on its hydrophilicity and beta-turn profiles. Among these Wnt-derived peptides, only WP7, which corresponds to residues 301-320 of human Wnt-1, bound to the soluble receptor for Wnt-1, mouse Frizzled-1/Fc chimera, promoted PC12 cell adherence, increased level of cytosolic beta-catenin in PC12 cells, and induced adhesion and neuronal differentiation of hippocampal neural precursor cells. These results suggest that residues 301-320 of human Wnt-1 is one of the receptor-binding sites and that WP7 may activate the canonical Wnt pathway. When combined with an appropriate matrix, the action of this Wnt-derived peptide, WP7, can be limited to within a location, and therefore could be useful in the regeneration of many tissues, without fear of tumor generation.

Wingless signalling alters the levels, subcellular distribution and dynamics of Armadillo and E-cadherin in third instar larval wing imaginal discs

Background

Armadillo, the Drosophila orthologue of vertebrate ß-catenin, plays a dual role as the key effector of Wingless/Wnt1 signalling, and as a bridge between E-Cadherin and the actin cytoskeleton. In the absence of ligand, Armadillo is phosphorylated and targeted to the proteasome. Upon binding of Wg to its receptors, the “degradation complex” is inhibited; Armadillo is stabilised and enters the nucleus to transcribe targets.

Methodology/Principal Findings

Although the relationship between signalling and adhesion has been extensively studied, few in vivo data exist concerning how the “transcriptional” and “adhesive” pools of Armadillo are regulated to orchestrate development. We have therefore addressed how the subcellular distribution of Armadillo and its association with E-Cadherin change in larval wing imaginal discs, under wild type conditions and upon signalling. Using confocal microscopy, we show that Armadillo and E-Cadherin are spatio-temporally regulated during development, and that a punctate species becomes concentrated in a subapical compartment in response to Wingless. In order to further dissect this phenomenon, we overexpressed Armadillo mutants exhibiting different levels of activity and stability, but retaining E-Cadherin binding. Arm^S10 displaces endogenous Armadillo from the AJ and the basolateral membrane, while leaving E-Cadherin relatively undisturbed. Surprisingly, ΔNArm^1–155 caused displacement of both Armadillo and E-Cadherin, results supported by our novel method of quantification. However, only membrane-targeted Myr-ΔNArm^1–155 produced comparable nuclear accumulation of Armadillo and signalling to Arm^S10. These experiments also highlighted a row of cells at the A/P boundary depleted of E-Cadherin at the AJ, but containing actin.

Conclusions/Significance

Taken together, our results provide in vivo evidence for a complex non-linear relationship between Armadillo levels, subcellular distribution and Wingless signalling. Moreover, this study highlights the importance of Armadillo in regulating the subcellular distribution of E-Cadherin

Wnt/beta-catenin inhibits dental pulp stem cell differentiation

Dental pulp stem cells (DPSCs) are a unique precursor population isolated from postnatal human dental pulp and have the ability to regenerate a reparative dentin-like complex. Canonical Wnt signaling plays a critical role in tooth development and stem cell self-renewal through beta-catenin. In this study, the regulation of odontoblast-like differentiation of DPSCs by canonical Wnt signaling was examined. DPSCs were stably transduced with canonical Wnt-1 or the active form of beta-catenin, with retrovirus-mediated infection. Northern blot analysis found that Wnt-1 strongly induced the expression of matricellular protein osteopontin, and modestly enhanced the expression of type I collagen in DPSCs. Unexpectedly, Wnt-1 inhibited alkaline phosphatase (ALP) activity and the formation of mineralized nodules in DPSCs. Moreover, over-expression of beta-catenin was also sufficient to suppress the differentiation and mineralization of DPSCs. In conclusion, our results suggest that canonical Wnt signaling negatively regulates the odontoblast-like differentiation of DPSCs.

PKD1 inhibits cancer cells migration and invasion via Wnt signaling pathway in vitro

The approximately 14 kb mRNA of the polycystic kidney disease gene PKD1 encodes a large ( approximately 460 kDa) protein, termed polycystin-1 (PC-1), that is responsible for autosomal dominant polycystic kidney disease (ADPKD). The unique organization of its multiple adhesive domains (16 Ig-like domains/PKD domains) suggests that it may play an important role in cell-cell/cell-matrix interactions. Here we demonstrated that PKD1 promoted cell-cell and cell-matrix interactions in cancer cells, indicating that PC-1 is involved in the cell adhesion process. Furthermore in this study, we showed that PKD1 inhibited cancer cells migration and invasion. And we also showed that PC-1 regulated these processes in a process that may be at least partially through the Wnt pathway. Collectively, our data suggest that PKD1 may act as a novel member of the tumor suppressor family of genes.

FGFs, Wnts and BMPs mediate induction of VEGFR-2 (Quek-1) expression during avian somite development

Regulation of VEGFR-2 (Quek1) is an important mechanism during blood vessel formation. In the paraxial mesoderm, Quek1 expression is restricted to the lateral portion of the somite and later to sclerotomal cells surrounding the neural tube. By implanting FGF 8b/8c or SU 5402 beads into the paraxial mesoderm, we show that FGF8 in addition to BMP4 from the intermediate mesoderm (IM) is a positive regulator of VEGFR-2 (Quek1) expression in the quail embryo. The expression of Quek1 in the medial somite half is normally repressed by the notochord and Sfrps-expression in the neural tube. Over-expression of Wnt 1/3a also results in an up-regulation of Quek1 expression in the somites. We also show that up-regulation of FGF8/Wnt 1/3a leads to an increase in the number of endothelial cells, whereas inhibition of FGF and Wnt signaling by SU 5402 and Sfrp-2 results in a loss of endothelial cells. Our results demonstrate that the regulation of Quek1 expression in the somites is mediated by the cooperative actions of BMP4, FGF8 and Wnt-signaling pathways.

Alterations and correlations of the components in the Wnt signaling pathway and its target genes in breast cancer

Both cyclin D1 and c-myc are key molecules in breast cancer carcinogenesis, and their transcriptional level and stability are regulated through several signaling pathways, including the Wnt signaling pathway. We performed immunohistochemical and mutational analyses of Wnt signaling components to investigate the association of Wnt signaling alterations with breast cancer carcinogenesis using 49 surgically resected primary breast cancer samples. Positive staining of cyclin D1 and c-myc was observed in 55.1% and 30.6% of the 49 breast cancer samples, respectively. Aberrant cytoplasmic expression of beta-catenin, which indicates the existence of alterations in the Wnt signaling pathway, was observed in 38.8% of breast cancer samples, though no mutation was found in the beta-catenin and Axin 1 genes. Reduced expression of APC was observed in 34.7% of samples. Statistical analysis revealed strong correlations between overexpression of beta-catenin and that of cyclin D1 and c-myc (p=0.0001 and 0.0117, respectively). Furthermore, overexpression of beta-catenin was significantly correlated with reduced expression of APC (p=0.0127). Wnt signaling alterations were frequently observed in breast cancer from the results of beta-catenin immunohistochemistry, although no mutation in the components of the Wnt signaling pathway was found in the present study. Based on the statistical analyses, we speculated that reduced expression of APC leads to overexpression of beta-catenin, and aberrant expression of cyclin D1 and c-myc mainly depends on alterations in the Wnt signaling pathway in breast cancer.

WNT/PCP signaling pathway and human cancer (review)

WNT/planar cell polarity (PCP) signaling pathway controls tissue polarity and cell movement through the activation of RHOA, c-Jun N-terminal kinase (JNK), and nemo-like kinase (NLK) signaling cascades. PCP is induced in Drosophila by the asymmetrical localization of Frizzled-Dishevelled-Diego-Starry night (Flamingo) complex and Van Gogh (Strabismus)-Prickle complex. Here, WNT/PCP signaling pathway implicated in human carcinogenesis is reviewed. Human WNT5A, WNT5B, and WNT11 are representative non-canonical WNTs transducing PCP signals through FZD3 or FZD6 receptors, and ROR1, ROR2 or PTK7 co-receptors. Human VANGL1, VANGL2 (Van Gogh homologs), CELSR1, CELSR2, CELSR3 (Starry night homologs), DVL1, DVL2, DVL3 (Dishevelled homologs), PRICKLE1, PRICKLE2 (Prickle homologs), and ANKRD6 (Diego homolog) are core PCP signaling molecules. MAGI3 assembles FZD, VANGL, PTEN, and adhesion molecules. Dishevelled-dependent WNT/PCP signals are transduced to the RHOA signaling cascade through Formin homology proteins DAAM1 and DAAM2, and to the JNK signaling cascade through MAPKKKs and MAPKK4/7. Dishevelled-independent WNT/ PCP signals are transduced to the NLK signaling cascade through MAP3K7 (TAK1). ANKRD6, NKD1 and NKD2 induce class switch from the WNT/GSK3beta signaling pathway to the WNT/PCP signaling pathway. WNT5A is up-regulated in various types of human cancer, such as gastric cancer, lung cancer, and melanoma. FZD3/FZD6 receptor and ROR2 co-receptor transduce WNT5A signal in gastric cancer. Aberrant activation of WNT/PCP signaling pathway in human cancer leads to more malignant phenotypes, such as abnormal tissue polarity, invasion, and metastasis. cDNA-PCR, microarray or ELISA reflecting aberrant activation of WNT/PCP signaling pathway could be developed as novel cancer prognostics. Single nucleotide polymorphism (SNP) and copy number polymorphism (CNP) of WNT/PCP signaling molecules mentioned above are suitable for use in screening of cancer predisposition, especially for gastric cancer. Antibody, RNAi, or small molecule compounds to regulate the function of WNT/PCP signaling molecules mentioned above are good candidates for development as novel cancer therapeutics.

Nrarp functions to modulate neural-crest-cell differentiation by regulating LEF1 protein stability

Nrarp (Notch-regulated ankyrin repeat protein) is a small protein that has two ankyrin repeats. Although Nrarp is known to be an inhibitory component of the Notch signalling pathway that operates in different developmental processes, the in vivo roles of Nrarp have not been fully characterized. Here, we show that Nrarp is a positive regulator in the Wnt signalling pathway. In zebrafish, knockdown of Nrarp-a expression by an antisense morpholino oligonucleotide (MO) results in altered Wnt-signalling-dependent neural-crest-cell development. Nrarp stabilizes LEF1 protein, a pivotal transcription factor in the Wnt signalling cascade, by blocking LEF1 ubiquitination. In accordance with this, the knockdown phenotype of lef1 is similar to that of nrarp-a, at least in part, in its effect on the development of multiple tissues in zebrafish. Furthermore, activation of LEF1 does not affect Notch activity or vice versa. These findings reveal that Nrarp independently regulates canonical Wnt and Notch signalling by modulating LEF1 and Notch protein turnover, respectively.

Evidence for active Wnt signaling during postresection intestinal adaptation

BACKGROUND

In the intestine, Wnt proteins are powerful regulators of cell proliferation, differentiation, and adhesion. Mutations of the adenomatous polyposis coli (APC) gene elevate nuclear beta-catenin and provoke intestinal tumor formation. We sought to determine whether Wnt signaling is involved in adaptive response to massive small bowel resection (SBR).

METHODS

Male Min mice with a mutation of the APC gene and wild-type controls underwent a 50% proximal SBR or sham operation. After 3 days, villus height, crypt depth, and rates of proliferation and apoptosis were recorded in the remnant ileum.

RESULTS

After SBR, villus height and enterocyte proliferation were significantly greater in the Min mice. Western blotting demonstrated resection-induced increases in beta-catenin, c-Myc, and E-cadherin after SBR, which was more pronounced in Min mice.

CONCLUSIONS

Mutation of the APC gene and augmented Wnt signaling in the intestine results in an enhanced adaptive response to massive SBR. These data, for the first time, implicate an important role for Wnt signaling during the pathogenesis of resection-induced intestinal adaptation.

Efficacy of Wnt-1 monoclonal antibody in sarcoma cells

BACKGROUND

Sarcomas are one of the most refractory diseases among malignant tumors. More effective therapies based on an increased understanding of the molecular biology of sarcomas are needed as current forms of therapy remain inadequate. Recently, it has been reported that Wnt-1/beta-catenin signaling inhibits apoptosis in several cancers. In this study, we investigated the efficacy of a monoclonal anti-Wnt-1 antibody in sarcoma cells.

METHODS

We treated cell lines A-204, SJSA-1, and fresh primary cultures of lung metastasis of sarcoma with a monoclonal anti-Wnt-1 antibody. Wnt-1 siRNA treatment was carried out in A-204. We assessed cell death using Crystal Violet staining. Apoptosis induction was estimated by flow cytometry analysis (Annexin V and PI staining). Cell signaling changes were determined by western blotting analysis.

RESULTS

We detected Wnt-1 expression in all tissue samples and cell lines. Significant apoptosis induction was found in monoclonal anti-Wnt-1 antibody treated cells compared to control monoclonal antibody treated cells (p < 0.02). Similarly, we observed increased apoptosis in Wnt-1 siRNA treated cells. Blockade of Wnt-1 signaling in both experiments was confirmed by analyzing intracellular levels of Dishevelled-3 and of cytosolic beta-catenin. Furthermore, the monoclonal anti-Wnt-1 antibody also induced cell death in fresh primary cultures of metastatic sarcoma in which Wnt-1 signaling was active.

CONCLUSION

Our results indicate that Wnt-1 blockade by either monoclonal antibody or siRNA induces cell death in sarcoma cells. These data suggest that Wnt-1 may be a novel therapeutic target for the treatment of a subset of sarcoma cells in which Wnt-1/beta-catenin signaling is active.