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Results for “Wnt Signaling Pathway”

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PubMed2003

Activation of Wnt signaling rescues neurodegeneration and behavioral impairments induced by beta-amyloid fibrils.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, which is probably caused by the cytotoxic effect of the amyloid beta-peptide (Abeta). We report here molecular changes induced by Abeta, both in neuronal cells in culture and in rats injected in the dorsal hippocampus with preformed Abeta fibrils, as an in vivo model of the disease. Results indicate that in both systems, Abeta neurotoxicity resulted in the destabilization of endogenous levels of beta-catenin, a key transducer of the Wnt signaling pathway. Lithium chloride, which mimics Wnt signaling by inhibiting glycogen synthase kinase-3beta promoted the survival of post-mitotic neurons against Abeta neurotoxicity and recovered cytosolic beta-catenin to control levels. Moreover, the neurotoxic effect of Abeta fibrils was also modulated with protein kinase C agonists/inhibitors and reversed with conditioned medium containing the Wnt-3a ligand. We also examined the spatial memory performance of rats injected with preformed Abeta fibrils in the Morris water maze paradigm, and found that chronic lithium treatment protected neurodegeneration by rescuing beta-catenin levels and improved the deficit in spatial learning induced by Abeta. Our results are consistent with the idea that Abeta-dependent neurotoxicity induces a loss of function of Wnt signaling components and indicate that lithium or compounds that mimic this signaling cascade may be putative candidates for therapeutic intervention in Alzheimer's patients.

Alzheimer Disease↗

PubMed2003

Glycogen synthase kinase-3 and Axin function in a beta-catenin-independent pathway that regulates neurite outgrowth in neuroblastoma cells.

We have sought to determine the roles of beta-catenin and the Wnt signaling pathway in neurite outgrowth using a model cell system, the Neuro-2a neuroblastoma cell line. Activation of the Wnt signaling pathway disrupts a multiprotein complex that includes beta-catenin, Axin, and glycogen synthase kinase-3 (GSK-3), which would otherwise promote the phosphorylation and degradation of beta-catenin. Stabilized beta-catenin accumulates in the cytosol and in the nucleus; in the nucleus it binds to TCF family transcription factors, forming a bipartite transcriptional activator of Wnt target genes. These events can be mimicked by lithium (Li(+)), which inhibits GSK-3 activity. Both Li(+) and the GSK-3 inhibitor SB415286 induced neurite outgrowth of Neuro-2a cells. Li(+)-induced neurite outgrowth did not require beta-catenin-/TCF-dependent transcription, and increasing levels of beta-catenin either by transfection or using Wnt-3A was not sufficient to induce neurite outgrowth. Interestingly, Axin, which is also a substrate for GSK-3, was destabilized by Li(+) and ectopic expression of Axin inhibited Li(+)-induced neurite outgrowth. Deletion analysis of Axin indicated that this inhibition required the GSK-3 binding site, but not the beta-catenin binding site. Our results suggest that a signaling pathway involving Axin and GSK-3, but not beta-catenin, regulates Li(+)-induced neurite outgrowth in Neuro-2a cells.

Animals↗

PubMed2001

Cytoplasmic/nuclear expression without mutation of exon 3 of the beta-catenin gene is frequent in the development of the neoplasm of the uterine cervix.

OBJECTIVE: The dual function of beta-catenin (e.g., as an intermediate protein between adherence junctions and the microfilaments, and as a mediator of the Wnt signaling pathway) is currently known. Stabilization of beta-catenin and subsequent activation of the Wnt signaling pathway are involved in the development of some malignancies. We analyzed the immunohistochemical localization of beta-catenin and the somatic mutation of exon 3 of the beta-catenin gene in the malignant phenotype of the uterine cervix. METHODS: Immunohistochemical localization of beta-catenin and mutation of exon 3 of the beta-catenin gene were analyzed in 38 precancerous lesions and 43 cancerous lesions. RESULTS: In normal cervix, beta-catenin was observed around the plasma membrane of the cells in the basal and parabasal layers of the epithelium. The frequency of cytoplasmic/nuclear beta-catenin expression correlated with a high histological grade of cervical intraepithelial neoplasia. Among invasive carcinomas, 11 (73%) of 15 samples showed cytoplasmic/nuclear localization to variable extents. A mutational analysis showed that mutation occurred in 7 of 68 specimens. Six cases with mutations revealed cytoplasmic/nuclear beta-catenin expression, though 32 (84%) of the 38 samples showing cytoplasmic/nuclear beta-catenin expression were not associated with the mutation. CONCLUSION: These results indicate that cytoplasmic/nuclear expression of beta-catenin is associated with the malignant phenotype of the cervix, but the contribution of mutation of the beta-catenin gene is limited.

Adult↗

PubMed2005

beta-catenin expression, DNA ploidy and clinicopathological features in ovarian cancer: a study in 253 patients.

The CTNNB1 gene and its product beta-catenin, a regulator of the Wnt signalling pathway, is often mutated and deregulated in human malignancies. Down stream targets of the Wnt signalling pathway are linked to genomic instability. In this study, the impact of beta-catenin expression on genomic instability in ovarian carcinoma, as determined by DNA ploidy, was investigated. Expression of beta-catenin was examined by immunohistochemistry in 253 ovarian carcinomas. The results were related to genomic instability and clinicopathological features of the patients. Membrane associated staining of beta-catenin was detected in nearly all cases with no correlation to clinical parameters. Most of the samples also had cytoplasmic (84%), while only 13% had nuclear beta-catenin localisation. A significant association between beta-catenin expression (cytoplasmic and nuclear) and histological subtype and degree of differentiation was observed. Nuclear beta-catenin was almost exclusively present in endometroid carcinomas. 53% of all endometroid tumours were positive for nuclear beta-catenin expression (P<0.0001). Mucinous carcinomas had the highest degree of cytoplasmic beta-catenin expression (92%), followed by endometroid (92%), mixed (90%), serous (82%), unclassified adenocarcinomas (81%), carcinomas clear cell and (70%), (P=0.01). Tumours with differentiation grade 1 (16%) and 2 (24%) had higher nuclear beta-catenin expression than grade 3 and clear cell carcinomas (6%) (P=0.012). Better prognostic outcome was found for patients with nuclear beta-catenin localisation as compared to the cases without (P=0.027). In conclusion, the study showed no correlation between beta-catenin expression in ovarian carcinoma and FIGO stage and genomic instability as determined by DNA ploidy status. However, nuclear beta-catenin expression was strongly associated with endometroid histological subtype. Finally, in ovarian cancer, although beta-catenin staining seems to be of prognostic importance with respect to nuclear staining in univariate analysis, only DNA ploidy status, histological grade and FIGO staging were of independent prognostic significance in multivariate analysis.

Cytoskeletal Proteins↗

PubMed2004

Casein kinase Iepsilon modulates the signaling specificities of dishevelled.

Wnt signaling is critical to many aspects of development, and aberrant activation of the Wnt signaling pathway can cause cancer. Dishevelled (Dvl) protein plays a central role in this pathway by transducing the signal from the Wnt receptor complex to the beta-catenin destruction complex. Dvl also plays a pivotal role in the planar cell polarity pathway that involves the c-Jun N-terminal kinase (JNK). How functions of Dvl are regulated in these two distinct pathways is not clear. We show that deleting the C-terminal two-thirds of Dvl, which includes the PDZ and DEP domains and is essential for Dvl-induced JNK activation, rendered the molecule a much more potent activator of the beta-catenin pathway. We also found that casein kinase Iepsilon (CKIepsilon), a previously identified positive regulator of Wnt signaling, stimulated Dvl activity in the Wnt pathway, but dramatically inhibited Dvl activity in the JNK pathway. Consistent with this, overexpression of CKIepsilon in Drosophila melanogaster stimulated Wnt signaling and disrupted planar cell polarity. We also observed a correlation between the localization and the signaling activity of Dvl in the beta-catenin pathway and the JNK pathway. Furthermore, by using RNA interference, we demonstrate that the Drosophila CKIepsilon homologue Double time positively regulates the beta-catenin pathway through Dvl and negatively regulates the Dvl-induced JNK pathway. We suggest that CKIepsilon functions as a molecular switch to direct Dvl from the JNK pathway to the beta-catenin pathway, possibly by altering the conformation of the C terminus of Dvl.

Adaptor Proteins, Signal Transducing↗

PubMed1999

The TAK1-NLK-MAPK-related pathway antagonizes signalling between beta-catenin and transcription factor TCF.

The Wnt signalling pathway regulates many developmental processes through a complex of beta-catenin and the T-cell factor/lymphoid enhancer factor (TCF/LEF) family of high-mobility-group transcription factors. Wnt stabilizes cytosolic beta-catenin, which then binds to TCF and activates gene transcription. This signalling cascade is conserved in vertebrates, Drosophila and Caenorhabditis elegans. In C. elegans, the proteins MOM-4 and LIT-1 regulate Wnt signalling to polarize responding cells during embryogenesis. MOM-4 and LIT-1 are homologous to TAK1 (a kinase activated by transforming growth factor-beta) mitogen-activated protein-kinase-kinase kinase (MAP3K) and MAP kinase (MAPK)-related NEMO-like kinase (NLK), respectively, in mammalian cells. These results raise the possibility that TAK1 and NLK are also involved in Wnt signalling in mammalian cells. Here we show that TAK1 activation stimulates NLK activity and downregulates transcriptional activation mediated by beta-catenin and TCF. Injection of NLK suppresses the induction of axis duplication by microinjected beta-catenin in Xenopus embryos. NLK phosphorylates TCF/LEF factors and inhibits the interaction of the beta-catenin-TCF complex with DNA. Thus, the TAK1-NLK-MAPK-like pathway negatively regulates the Wnt signalling pathway.

Animals↗

PubMed2003

Nuclear accumulation of beta-catenin protein in Wilms' tumours.

The wnt-signalling pathway plays an important role during both normal kidney development and Wilms' tumourigenesis. Activation of this pathway involves stabilization, intracellular accumulation, and nuclear translocation of the beta-catenin protein and may be caused by specific mutations in the beta-catenin gene itself. Such mutations have been found in about 15% of Wilms' tumours. This study has analysed the intracellular levels and subcellular distribution of beta-catenin protein in 36 primary Wilms' tumour specimens and has correlated these results with the mutational status of the beta-catenin gene. Immunohistochemistry detected faint cytoplasmic and strong membranous expression of beta-catenin protein in the epithelial compartment of all tumours examined. In contrast, nuclear immunoreactivity for beta-catenin was detected in 9 of 9 Wilms' tumours containing a mutation of the beta-catenin gene and in 15 of 27 Wilms' tumours without detectable beta-catenin mutation. Nuclear positivity, in each case, was found to be very strong, but was usually present only in a fraction of cells ranging from 5% to 10%. Among the different histological subcompartments, blastemal and mesenchymal cell nuclei preferentially stained positive, whereas cells of epithelial differentiation displayed nuclear localization of beta-catenin protein in only a single case. Furthermore, nuclear positive cells were found in Wilms' tumours of all stages and in tumours of both favourable and unfavourable histology. These data support the idea that activation of the wnt-signalling pathway is a key oncogenic step in Wilms' tumourigenesis and that it probably involves transcriptional activation of critical target genes, carried out by beta-catenin protein in the nucleus. The fact that nuclear immunoreactivity specific for beta-catenin was detected in a significant number of Wilms' tumours in the absence of beta-catenin mutations suggests that genetic defects affecting other members of the wnt-signalling pathway may contribute to the development of Wilms' tumours in those cases.

Adolescent↗

PubMed2006

A critical role for endocytosis in Wnt signaling.

BACKGROUND: The Wnt signaling pathway regulates many processes during embryonic development, including axis specification, organogenesis, angiogenesis, and stem cell proliferation. Wnt signaling has also been implicated in a number of cancers, bone density maintenance, and neurological conditions during adulthood. While numerous Wnts, their cognate receptors of the Frizzled and Arrow/LRP5/6 families and downstream pathway components have been identified, little is known about the initial events occurring directly after receptor activation. RESULTS: We show here that Wnt proteins are rapidly endocytosed by a clathrin- and dynamin-mediated process. While endocytosis has traditionally been considered a principal mechanism for receptor down-regulation and termination of signaling pathways, we demonstrate that interfering with clathrin-mediated endocytosis actually blocks Wnt signaling at the level of beta-catenin accumulation and target gene expression. CONCLUSION: A necessary component of Wnt signaling occurs in a subcellular compartment distinct from the plasma membrane. Moreover, as internalized Wnts transit partially through the transferrin recycling pathway, it is possible that a "signaling endosome" serves as a nexus for activated Wnt pathway components.

Animals↗

PubMed2007

VDR-mediated inhibition of DKK1 and SFRP2 suppresses adipogenic differentiation of murine bone marrow stromal cells.

Osteoblasts and adipocytes are thought to derive from a common bone marrow stromal cell (BMSC) precursor. Activation of the canonical Wnt signaling pathway plays a pivotal role in the differentiation of BMSCs along either of these two lineages, promoting osteogenesis and inhibiting adipogenesis. Liganded nuclear receptors, including the vitamin D receptor (VDR) and peroxisomal proliferator-activated receptor gamma (PPARgamma), can also affect BMSCs differentiation. To address whether VDR ablation modulates the differentiation of BMSCs into the osteoblast or adipogenic lineages, BMSCs were isolated from VDR null mice and from their wild-type littermates. VDR ablation did not alter osteoblastic differentiation. However, when cultured under adipogenic conditions, BMSCs from the VDR null mice expressed higher mRNA levels of PPARgamma and of markers of adipogenic differentiation. An increase in the size and number of mature adipocyte foci was also observed in cultures isolated from VDR null mice relative to those isolated from wild-type mice. To address whether the increased adipogenesis observed in the VDR null cultures was associated with inhibition of the canonical Wnt signaling pathway, mRNA levels for DKK1 and SFRP2 were examined. Cultures from the VDR null mice expressed higher levels of mRNA encoding DKK1 and SFRP2 than did the wild-type cultures. This difference is, at least in part, due to ligand-dependent actions of the VDR, since 1,25-dihydroxyvitamin D3 suppressed DKK1 and SFRP2 expression in wild-type cultures. Thus, the VDR inhibits adipogenesis of BMSCs at least in part by suppressing the expression of inhibitors of the canonical Wnt signaling pathway.

Adipocytes↗

PubMed2000

Xwnt11 is a target of Xenopus Brachyury: regulation of gastrulation movements via Dishevelled, but not through the canonical Wnt pathway.

Gastrulation in the amphibian embryo is driven by cells of the mesoderm. One of the genes that confers mesodermal identity in Xenopus is Brachyury (Xbra), which is required for normal gastrulation movements and ultimately for posterior mesoderm and notochord differentiation in the development of all vertebrates. Xbra is a transcription activator, and interference with transcription activation leads to an inhibition of morphogenetic movements during gastrulation. To understand this process, we have screened for downstream target genes of Brachyury (Tada, M., Casey, E., Fairclough, L. and Smith, J. C. (1998) Development 125, 3997-4006). This approach has now allowed us to isolate Xwnt11, whose expression pattern is almost identical to that of Xbra at gastrula and early neurula stages. Activation of Xwnt11 is induced in an immediate-early fashion by Xbra and its expression in vivo is abolished by a dominant-interfering form of Xbra, Xbra-En(R). Overexpression of a dominant-negative form of Xwnt11, like overexpression of Xbra-En(R), inhibits convergent extension movements. This inhibition can be rescued by Dsh, a component of the Wnt signalling pathway and also by a truncated form of Dsh which cannot signal through the canonical Wnt pathway involving GSK-3 and (beta)-catenin. Together, our results suggest that the regulation of morphogenetic movements by Xwnt11 occurs through a pathway similar to that involved in planar polarity signalling in Drosophila.

Activins↗

PubMed2006

Wdr5, a WD-40 protein, regulates osteoblast differentiation during embryonic bone development.

Wdr5 accelerates osteoblast and chondrocyte differentiation in vitro, and is developmentally expressed in osteoblasts as well as in proliferating and hypertrophic chondrocytes. To investigate the role of Wdr5 during endochondral bone development, transgenic mice overexpressing Wdr5 under the control of the 2.3-kb fragment of the mouse alpha(1) I collagen promoter were generated. The transgene was specifically expressed in the osteoblasts of transgene positive mice and was absent in the growth plate. Histological analyses at embryonic day 14.5 demonstrated that the humeri of transgene positive embryos were longer than those isolated from wild-type littermates largely due to an expansion of the hypertrophic chondrocyte layer. Acceleration of osteoblast differentiation was observed with greater and more extensive expression of type I collagen and more extensive mineral deposition in the bone collar of transgene positive embryos. Acceleration of vascular invasion was also observed in transgene positive mice. Postnatal analyses of transgenic mice confirmed persistent acceleration of osteoblast differentiation. Targeted expression of Wdr5 to osteoblasts resulted in earlier activation of the canonical Wnt signaling pathway in the bone collar as well as in primary calvarial osteoblast cultures. In addition, overexpression of Wdr5 increased the expression of OPG, a target of the canonical Wnt signaling pathway. Overall, our findings suggest that Wdr5 accelerates osteoblast differentiation in association with activation of the canonical Wnt pathway.

Animals↗

PubMed2005

Gene array analysis of Wnt-regulated genes in C3H10T1/2 cells.

Wnt/beta-catenin signaling is involved in a large variety of modeling and remodeling processes including cell polarity, cell differentiation, and cell migration. Recently, a role of the Wnt pathway in bone biology has been demonstrated. However, the precise mechanism by which Wnt proteins regulate bone formation still remains to be elucidated. We have previously shown that the Wnt pathway mediates induction of alkaline phosphatase, an osteoblast differentiation marker, in the pluripotent mesenchymal cells C3H10T1/2. In the present study, we performed a genome-wide expression analysis using Affymetrix oligonucleotide chips to determine the Wnt3a-induced gene expression profile in C3H10T1/2 cells. The expression profiles of 447 Wnt3a-regulated genes, classified into distinct functional families, are presented here. Our data reveal that Wnt3a regulates several genes that are involved in osteoblast and adipocyte differentiation. Importantly, Wnt3a induces the expression of osteoprotegerin by a beta-catenin dependent mechanism indicating that the Wnt pathway may also affect osteoclastogenesis. Through the analysis of our expression profiling data, we have established a TaqMan panel as a tool to rapidly compare the expression profiles of a specific set of genes induced by distinct stimuli acting in the Wnt/beta-catenin pathway. Using the TaqMan panel, we have compared the gene expression profiles induced by Wnt1, Wnt2, and Wnt3a in C3H10T1/2 cells, and also by two different GSK-3beta inhibitors: LiCl and SB216773. Our data show that Wnt1 and Wnt3a act in a similar manner, distinct from Wnt2. Finally, we found that LiCl and SB216773 displayed different profiles in the TaqMan panel evidencing their distinct inhibitory action toward GSK-3beta. Overall, data presented herein will aid further understanding of the involvement of the Wnt signaling pathway in its regulation of osteoblast and adipocyte differentiation and function and, in addition, will enhance current knowledge of the Wnt signaling pathway itself.

Animals↗

PubMed1999

Signaling through beta-catenin and Lef/Tcf.

Beta-catenin plays a structural role in cell adhesion by binding to cadherins at the intracellular surface of the plasma membrane and a signaling role in the cytoplasm as the penultimate downstream mediator of the wnt signaling pathway. The ultimate mediator of this pathway is a nuclear complex of beta-catenin acting as a coactivtor with lymphoid enhancer factor/T cell factor (Lef/Tcf) transcription factors to stimulate transcription of a variety of target genes. Signaling through beta-catenin is regulated by modulating its degradation and nuclear translocation. In the absence of an activating signal, phosphorylation of beta-catenin by glycogen synthase kinase 3 (GSK3) acting in conjunction with adenomatous polyposis coli and axin/conductin causes beta-catenin to interact with the beta-transducin repeat-containing protein which results in its ubiquitination and degradation. Signaling from the wnt pathway activates dishevelled which, in an as yet undefined manner, inhibits the activity of GSK3 resulting in an increase in the cytoplasmic free pool of beta-catenin, and translocation into the nucleus. The integrin-linked kinase (ILK) pathway also activates beta-catenin-Lef/Tcf signaling. ILK phosphorylates GSK3 to inhibit its activity and translocates beta-catenin into the nucleus. In addition, ILK downregulates the expression of E-cadherin and upregulates Lef-1 expression. In the final step of the beta-catenin-Lef/Tcf signaling pathway, nuclear beta-catenin binds pontin52-TATA binding protein and displaces Groucho-related gene or CREB-binding protein corepressors from Lef/Tcf resulting in stimulation of transcription. During development, beta-catenin-Lef/Tcf signaling is involved in the formation of dorsal mesoderm and dorsal axis. Furthermore, defects in the beta-catenin-Lef/Tcf pathway are involved in the development of several types of cancers.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Association of Smads with lymphoid enhancer binding factor 1/T cell-specific factor mediates cooperative signaling by the transforming growth factor-beta and wnt pathways.

The transforming growth factor-beta (TGFbeta) and Wnt/wingless pathways play pivotal roles in tissue specification during development. Activation of Smads, the effectors of TGFbeta superfamily signals, results in Smad translocation from the cytoplasm into the nucleus where they act as transcriptional comodulators to regulate target gene expression. Wnt/wingless signals are mediated by the DNA-binding HMG box transcription factors lymphoid enhancer binding factor 1/T cell-specific factor (LEF1/TCF) and their coactivator beta-catenin. Herein, we show that Smad3 physically interacts with the HMG box domain of LEF1 and that TGFbeta and Wnt pathways synergize to activate transcription of the Xenopus homeobox gene twin (Xtwn). Disruption of specific Smad and LEF1/TCF DNA-binding sites in the promoter abrogates synergistic activation of the promoter. Consistent with this observation, introduction of Smad sites into a TGFbeta-insensitive LEF1/TCF target gene confers cooperative TGFbeta and Wnt responsiveness to the promoter. Furthermore, we demonstrate that TGFbeta-dependent activation of LEF1/TCF target genes can occur in the absence of beta-catenin binding to LEF1/TCF and requires both Smad and LEF1/TCF DNA-binding sites in the Xtwn promoter. Thus, our results show that TGFbeta and Wnt signaling pathways can independently or cooperatively regulate LEF1/TCF target genes and suggest a model for how these pathways can synergistically activate target genes.

Animals↗

PubMed2005

An overview of apoptosis and the prevention of colorectal cancer.

Colorectal cancer arises as a result of the accumulation of genetic errors many of which affect the control of apoptosis. Effective chemoprevention strategies for colorectal cancer must rectify these genetic defects. Mutation of apc is often the initiating genetic lesion in colorectal cancers that develop along the chromosomal instability pathway. Depending on the cellular context, loss of apc activates the Wnt signalling pathway causing immediate widespread apoptosis of colorectal epithelial cells and defects in differentiation and cell migration. Only cells that are inherently resistant to apoptosis survive this initial wave of apoptosis. These surviving cells constitute the epithelial population that develop into adenomas. Two gene targets of the Wnt signalling pathway are of particular relevance to apoptosis. Although controversial, survivin may function to inhibit apoptosis. MYC has two outputs in normal cells, the induction of apoptosis and proliferation. These opposing functions work so that MYC can only induce cell proliferation in cells if apoptosis is disabled. p53 couples apoptosis to mitogenic signals and survival pathways. Under some circumstances, NF-kappaB can act as an inhibitor of apoptosis possibly through increased expression of bcl-x(L). Tumours that evolve by the microsatellite instability pathway often have mutations in the proapoptotic gene bax. Colonic adenomas express cyclo-oxygenase-2 (COX-2) and may be targets of chemoprevention before the development of malignancy. However, the recent discovery that coxibs increase the risk of serious cardiovascular events limits their use as chemopreventive agents. Nevertheless, aspirin remains a drug of great interest as it is already known to reduce the risk of colorectal cancer by up to 50%. The balance of evidence shows that high vegetable fibre diets can prevent colorectal cancer, probably via the fermentation of butyrate enhancing the apoptotic response to DNA damage.

Animals↗

PubMed2004

Wnt inhibitory factor-1 is silenced by promoter hypermethylation in human lung cancer.

Aberrant activation of the Wingless-type (Wnt) signaling pathway is associated with a variety of human cancers, and we recently reported the importance of aberrant Wnt signaling in lung cancer. On the other hand, inhibition of Wnt signaling suppresses growth in numerous cell types. Wnt inhibitory factor-1 (WIF-1) is a secreted antagonist that can bind Wnt in the extracellular space and inhibit Wnt signaling. Recently, down-regulation of WIF-1 has been reported in several human cancers. To discover the mechanism of WIF-1 silencing in lung cancer, we first identified the human WIF-1 promoter and subsequently examined the methylation status in the CpG islands. By using methylation-specific PCR and sequence analysis after bisulfite treatment, we demonstrate here frequent CpG island hypermethylation in the functional WIF-1 promoter region. This hypermethylation correlates with its transcriptional silencing in human lung cancer cell lines. Moreover, treatment with 5-aza-2'-deoxycytidine restores WIF-1 expression. We then studied WIF-1 expression in 18 freshly resected lung cancers, and we show a down-regulation in 15 of them (83%). This silencing also correlates with WIF-1 promoter methylation. Our results suggest that methylation silencing of WIF-1 is a common and likely important mechanism of aberrant activation of the Wnt signaling pathway in lung cancer pathogenesis, raising its therapeutic interest.

Adaptor Proteins, Signal Transducing↗

PubMed2026

Non-structural maintenance of chromosome condensin I complex subunit H knockdown suppresses malignant progression of esophageal squamous cell carcinoma via the Wnt/β-catenin signaling pathway.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) remains a major cause of cancer-related mortality, and effective therapeutic targets are still limited. Non-structural maintenance of chromosome condensin I complex subunit H (NCAPH) has been implicated in tumorigenesis; however, its clinical relevance, functional roles, and underlying mechanisms in ESCC are not fully defined. We aimed to characterize the expression pattern, prognostic value, biological functions, and mechanistic basis of NCAPH in ESCC. METHODS: Public datasets from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) were analyzed to evaluate NCAPH expression and clinical associations. Single-cell RNA sequencing (scRNA-seq) data were used to map cell-type-specific distribution of NCAPH in tumor and adjacent tissues. NCAPH was silenced in KYSE150 and KYSE510 cells using lentiviral short hairpin RNAs (shRNAs), followed by Cell Counting Kit-8 (CCK-8), colony formation, wound-healing, and Transwell migration/invasion assays. A nude mouse xenograft model was established to assess the effect of NCAPH knockdown in vivo. RNA sequencing (RNA-seq), quantitative polymerase chain reaction (qPCR), western blotting, and enzyme-linked immunosorbent assay (ELISA) were performed to explore potential mechanisms. RESULTS: NCAPH was consistently upregulated in ESCC across multiple cohorts and was associated with unfavorable clinicopathological features and poorer survival. Functional assays demonstrated that NCAPH knockdown significantly inhibited ESCC cell proliferation, migration, invasion, and clonogenic growth. In vivo, NCAPH silencing suppressed xenograft tumor growth. Mechanistically, transcriptomic profiling and molecular validation indicated attenuation of Wnt/β-catenin signaling following NCAPH depletion, accompanied by reduced β-catenin and downstream targets. CONCLUSIONS: NCAPH promotes malignant progression of ESCC, at least in part through activation of the Wnt/β-catenin pathway, and may serve as a potential biomarker and therapeutic target.

Esophageal squamous cell carcinoma (ESCC)↗

PubMed1997

Linking Frizzled and Wnt signaling in Drosophila development.

Drosophila Frizzled-2 (Dfz2) has been identified as a putative fly Wingless (Wg) receptor. Although Dfz2 shows significant homology with Fz, a protein that operates in the mechanisms that establish planar polarity in Drosophila epithelia, any clear evidence for an involvement by Fz in a Wnt signaling pathway has hitherto been absent. Here we describe the planar polarity phenotypes of loss-of-function and overexpression of Fz in the developing Drosophila eye and find it almost identical to the loss-of-function or overexpression of Dishevelled (Dsh - a protein operating in Wnt second messenger systems). In addition, we show that overexpression of Shaggy (Sgg - another component of the Wnt pathway) in the eye also causes a phenotype similar to Fz and Dsh. To test further the link between planar polarity and Wnt signaling we misexpressed Wg in the developing eye and found it had a potent polarizing effect in the retinal epithelium. Since the overexpression of Fz in the developing eye gave a phenotype consistent with activating the Wnt pathway, we tested overexpression of Fz in the developing embryonic ectoderm and found that it phenocopied overexpression of Wg. To check that Fz was indeed able to activate a Wnt pathway we overexpressed it in Drosophila tissue culture cells and observed the characteristic phosphorylation of Dsh that occurs in response to Wnt signaling. Taken together our results significantly strengthen the case for Fz acting in a Wnt signaling pathway in Drosophila.

Adaptor Proteins, Signal Transducing↗