WNT3

Gene Summary

Gene:WNT3; Wnt family member 3
Aliases: INT4, TETAMS
Location:17q21.31-q21.32
Summary:The WNT gene family consists of structurally related genes which encode secreted signaling proteins. These proteins have been implicated in oncogenesis and in several developmental processes, including regulation of cell fate and patterning during embryogenesis. This gene is a member of the WNT gene family. It encodes a protein which shows 98% amino acid identity to mouse Wnt3 protein, and 84% to human WNT3A protein, another WNT gene product. The mouse studies show the requirement of Wnt3 in primary axis formation in the mouse. Studies of the gene expression suggest that this gene may play a key role in some cases of human breast, rectal, lung, and gastric cancer through activation of the WNT-beta-catenin-TCF signaling pathway. This gene is clustered with WNT15, another family member, in the chromosome 17q21 region. [provided by RefSeq, Jul 2008]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:proto-oncogene Wnt-3
Source:NCBIAccessed: 11 March, 2017

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Messenger RNA
  • Signal Transduction
  • Transcription Factors
  • Up-Regulation
  • Oligonucleotide Array Sequence Analysis
  • Dishevelled Proteins
  • Proto-Oncogene Proteins
  • Wnt4 Protein
  • Gene Expression Profiling
  • Molecular Sequence Data
  • Cell Line
  • beta Catenin
  • Breast Cancer
  • Proteins
  • Wnt Proteins
  • Cancer Gene Expression Regulation
  • Base Sequence
  • Signal Transducing Adaptor Proteins
  • Transcriptional Activation
  • Phosphoproteins
  • Amino Acid Sequence
  • Mutation
  • Chromosome 17
  • Frizzled Receptors
  • Intercellular Signaling Peptides and Proteins
  • Neoplasm Proteins
  • Wnt-5a Protein
  • Membrane Proteins
  • RTPCR
  • DNA Primers
  • Mice, Transgenic
  • Liver Cancer
  • Chromosome Mapping
  • Western Blotting
  • Cell Proliferation
  • Neoplastic Cell Transformation
  • Tissue Distribution
  • Transcription
  • Gene Expression
Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: WNT3 (cancer-related)

DO Carmo NG, Sakamoto LH, Pogue R, et al.
Altered Expression of PRKX, WNT3 and WNT16 in Human Nodular Basal Cell Carcinoma.
Anticancer Res. 2016; 36(9):4545-51 [PubMed] Related Publications
BACKGROUND/AIM: Nodular and superficial are the most common subtypes of basal cell carcinoma (BCC). Signaling pathways such as Hedgehog (HH) and Wingless (WNT) signaling are associated with BCC phenotypic variation. The aim of the study was to evaluate of the expression profiles of 84 genes related to the WNT and HH signaling pathways in patients with nodular and superficial BCC.
MATERIALS AND METHODS: A total of 58 BCCs and 13 samples of normal skin were evaluated by quantitative real-time polymerase chain reaction (qPCR) to detect the gene-expression profile.
RESULTS: qPCR array showed segregation in BCC subtypes compared to healthy skin. PRKX, WNT3 and WNT16 were significantly (p<0.05) altered: PRKX was up-regulated, and WNT3 and WNT16 were down-regulated in nodular BCC.
CONCLUSION: PRKX, WNT3 and WNT16 genes, belonging to the WNT signaling pathway, are involved in the tumorigenic process of nodular BCC.

Verras M, Papandreou I, Denko NC
WNT16-expressing Acute Lymphoblastic Leukemia Cells are Sensitive to Autophagy Inhibitors after ER Stress Induction.
Anticancer Res. 2015; 35(9):4625-31 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Previous work from our group showed hypoxia can induce endoplasmic reticulum (ER) stress and block the processing of the WNT3 protein in cells engineered to express WNT3a. Acute lymphoblastic leukemia (ALL) cells with the t(1:19) translocation express the WNT16 gene, which is thought to contribute to transformation.
RESULTS: ER-stress blocks processing of endogenous WNT16 protein in RCH-ACV and 697 ALL cells. Biochemical analysis showed an aggregation of WNT16 proteins in the ER of stressed cells. These large protein masses cannot be completely cleared by ER-associated protein degradation, and require for additional autophagic responses. Pharmacological block of autophagy significantly increased cell death in ER-stressed ALL. Furthermore, murine cells engineered to express WNT16 are similarly sensitized.
CONCLUSION: ALL cells expressing WNT16 are sensitive to ER stress, and show enhanced killing after addition of chloroquine. These findings suggest a potential clinical application of inducers of ER stress with inhibitors of autophagy in patients with high-risk ALL.

Koo BK, van Es JH, van den Born M, Clevers H
Porcupine inhibitor suppresses paracrine Wnt-driven growth of Rnf43;Znrf3-mutant neoplasia.
Proc Natl Acad Sci U S A. 2015; 112(24):7548-50 [PubMed] Free Access to Full Article Related Publications
Rnf43 (RING finger protein 43) and Znrf3 (zinc/RING finger protein 3) (RZ) are two closely related transmembrane E3 ligases, encoded by Wnt target genes, that remove surface Wnt (wingless-int) receptors. The two genes are mutated in various human cancers. Such tumors are predicted to be hypersensitive to, yet still depend on, secreted Wnts. We previously showed that mutation of RZ in the intestine yields rapidly growing adenomas containing LGR5(+) (leucine-rich repeat-containing G-protein coupled receptor 5) stem cells and Wnt3-producing Paneth cells. We now show that removal of Paneth cells by Math1 mutation inhibits RZ(-/-) tumor formation. Similarly, deletion of Wnt3 inhibits tumorigenesis. Treatment of mice carrying RZ(-/-) intestinal neoplasia with a small molecule Wnt secretion inhibitor (porcupine inhibitor C59) strongly inhibited growth, whereas adjacent normal crypts remained intact. These results establish that paracrine Wnt secretion is an essential driver of RZ(-/-) tumor growth and imply that a therapeutic window exists for the use of porcupine inhibitors for RZ-mutant cancers.

Gong C, Qu S, Lv XB, et al.
BRMS1L suppresses breast cancer metastasis by inducing epigenetic silence of FZD10.
Nat Commun. 2014; 5:5406 [PubMed] Related Publications
BRMS1L (breast cancer metastasis suppressor 1 like, BRMS1-like) is a component of Sin3A-histone deacetylase (HDAC) co-repressor complex that suppresses target gene transcription. Here we show that reduced BRMS1L in breast cancer tissues is associated with metastasis and poor patient survival. Functionally, BRMS1L inhibits breast cancer cells migration and invasion by inhibiting epithelial-mesenchymal transition. These effects are mediated by epigenetic silencing of FZD10, a receptor for Wnt signalling, through HDAC1 recruitment and histone H3K9 deacetylation at the promoter. Consequently, BRMS1L-induced FZD10 silencing inhibits aberrant activation of WNT3-FZD10-β-catenin signalling. Furthermore, BRMS1L is a target of miR-106b and miR-106b upregulation leads to BRMS1L reduction in breast cancer cells. RNA interference-mediated silencing of BRMS1L expression promotes metastasis of breast cancer xenografts in immunocompromised mice, whereas ectopic BRMS1L expression inhibits metastasis. Therefore, BRMS1L provides an epigenetic regulation of Wnt signalling in breast cancer cells and acts as a breast cancer metastasis suppressor.

Ibarrola-Villava M, Kumar R, Nagore E, et al.
Genes involved in the WNT and vesicular trafficking pathways are associated with melanoma predisposition.
Int J Cancer. 2015; 136(9):2109-19 [PubMed] Related Publications
Multifactorial predisposition to melanoma includes genes involved in pigmentation, immunity and DNA repair. Nonetheless, missing heritability in melanoma is still important. We studied the role of 335 candidate SNPs in melanoma susceptibility by using a dedicated chip and investigating 110 genes involved in different pathways. A discovery set was comprised of 1069 melanoma patients and 925 controls from France. Data were replicated using validation phases II (1085 cases and 801 controls from Spain) and III (1808 cases and 1894 controls from Germany and a second set of Spanish samples). In addition, an exome sequencing study was performed in three high-risk French melanoma families. Nineteen SNPs in 17 genes were initially associated with melanoma in the French population. Six SNPs were replicated in phase II, including two new SNPs in the WNT3 (rs199524) and VPS41 (rs11773094) genes. The role of VPS41 and WNT3 was confirmed in a meta-analysis (3940 melanoma cases and 3620 controls) with two-side p values of 0.002, (OR = 0.86) and 4.07 × 10(-10) (OR = 0.80), respectively. Exome sequencing revealed a non-synonymous VPS41 variant in one family that was shown to be strongly associated with familial melanoma (OR = 4.46, p = 0.001) in an independent sample of 178 melanoma families. WNT3 belongs to WNT pathway known to play a crucial role in melanoma, whereas VPS41 regulates vesicular trafficking and is thought to play a role in pigmentation. Our work identified two new pathways involved in melanoma predisposition. These results may be useful in the future for identifying individuals highly predisposed to melanoma.

Voloshanenko O, Erdmann G, Dubash TD, et al.
Wnt secretion is required to maintain high levels of Wnt activity in colon cancer cells.
Nat Commun. 2013; 4:2610 [PubMed] Free Access to Full Article Related Publications
Aberrant regulation of the Wnt/β-catenin pathway has an important role during the onset and progression of colorectal cancer, with over 90% of cases of sporadic colon cancer featuring mutations in APC or β-catenin. However, it has remained a point of controversy whether these mutations are sufficient to activate the pathway or require additional upstream signals. Here we show that colorectal tumours express elevated levels of Wnt3 and Evi/Wls/GPR177. We found that in colon cancer cells, even in the presence of mutations in APC or β-catenin, downstream signalling remains responsive to Wnt ligands and receptor proximal signalling. Furthermore, we demonstrate that truncated APC proteins bind β-catenin and key components of the destruction complex. These results indicate that cells with mutations in APC or β-catenin depend on Wnt ligands and their secretion for a sufficient level of β-catenin signalling, which potentially opens new avenues for therapeutic interventions by targeting Wnt secretion via Evi/Wls.

Fox SA, Richards AK, Kusumah I, et al.
Expression profile and function of Wnt signaling mechanisms in malignant mesothelioma cells.
Biochem Biophys Res Commun. 2013; 440(1):82-7 [PubMed] Related Publications
Malignant mesothelioma (MM) is an uncommon and particularly aggressive cancer associated with asbestos exposure, which currently presents an intractable clinical challenge. Wnt signaling has been reported to play a role in the neoplastic properties of mesothelioma cells but has not been investigated in detail in this cancer. We surveyed expression of Wnts, their receptors, and other key molecules in this pathway in well established in vitro mesothelioma models in comparison with primary mesothelial cultures. We also tested the biological response of MM cell lines to exogenous Wnt and secreted regulators, as well as targeting β-catenin. We detected frequent expression of Wnt3 and Wnt5a, as well as Fzd 2, 4 and 6. The mRNA of Wnt4, Fzd3, sFRP4, APC and axin2 were downregulated in MM relative to mesothelial cells while LEF1 was overexpressed in MM. Functionally, we observed that Wnt3a stimulated MM proliferation while sFRP4 was inhibitory. Furthermore, directly targeting β-catenin expression could sensitise MM cells to cytotoxic drugs. These results provide evidence for altered expression of a number of Wnt/Fzd signaling molecules in MM. Modulation of Wnt signaling in MM may prove a means of targeting proliferation and drug resistance in this cancer.

Zhang KS, Zhou Q, Wang YF, Liang LJ
Inhibition of Wnt signaling induces cell apoptosis and suppresses cell proliferation in cholangiocarcinoma cells.
Oncol Rep. 2013; 30(3):1430-8 [PubMed] Related Publications
The aim of the present study was to explore possible gene therapy for hilar cholangiocarcinoma by detecting the activation of the Wnt signaling pathway in 4 cholangiocarcinoma cell lines and inhibiting its expression by RNA interference (RNAi) targeting key factors of this pathway. The expression levels of the Wnt pathway-related factors, Wnt2, Wnt3, β-catenin and transcription factor 4, and its target genes, c-myc and cyclin D1, in 4 cholangiocarcinoma cell lines were detected by RT-PCR, western blotting and immunofluorescence microscopy. After transfection of siRNAs targeting Wnt2 and β-catenin into FRH0201 cells, the expression of the Wnt pathway-related factors and its target genes was again detected, and the cell cycle distribution, apoptosis and proliferation were analyzed by flow cytometry and MTT assay. Activation of the Wnt pathway and the expression of its target genes were detected in all 4 cell lines at various levels. After siRNA transfection, the expression of the target genes in the FRH0201 cells was significantly downregulated. In addition, the Wnt pathway was blocked, cell apoptosis was enhanced and cell proliferation was suppressed. In conclusion, the Wnt signaling pathway is activated in cholangiocarcinoma cells. RNAi technology targeting Wnt2 and β-catenin may be a possible gene therapy for hilar cholangiocarcinoma.

Kimura Y, Arakawa F, Kiyasu J, et al.
The Wnt signaling pathway and mitotic regulators in the initiation and evolution of mantle cell lymphoma: Gene expression analysis.
Int J Oncol. 2013; 43(2):457-68 [PubMed] Related Publications
For an accurate understanding of mantle cell lymphoma (MCL), molecular behavior could be staged into two major events: lymphomagenesis with the t(11;14) translocation (initiation), and evolution into a more aggressive form (transformation). Unfortunately, it is still unknown which genes contribute to each event. In this study, we performed cDNA microarray experiments designed based on the concept that morphologically heterogeneous MCL samples would provide insights into the role of aberrant gene expression for both events. A total of 15 MCLs were collected from the files, which include a total of 237 MCL patients confirmed by histology as CCND1-positive. We posited four stepwise morphological grades for MCL: MCL in situ, MCL with classical form (cMCL), MCL with aggressive form (aMCL), and MCL with intermediate morphology between classical and aggressive forms at the same site (iMCL). To identify genes involved in initiation, we compared the tumor cells of MCL in situ (n=4) with normal mantle zone B lymphocytes (n=4), which were selected by laser microdissection (LMD). To identify genes contributing to transformation, we selected the overlapping genes differentially expressed between both cMCL (n=4) vs. aMCL (n=5) and classical vs. aggressive areas in iMCL (n=2) obtained by LMD. A significant number of genes (n=23, p=0.016) belonging to the Wnt signaling pathway were differentially expressed in initiation. This specific activation was confirmed by immuno-histochemistry, as MCL in situ had nuclear localization of phosphorylated-β-catenin with high levels of cytoplasmic Wnt3 staining. For transformation, identified 60 overlapping genes included a number of members of the p53 interaction network (CDC2, BIRC5 and FOXM1), which is known to mediate cell cycle progression during the G2/M transition. Thus, we observe that the Wnt signaling pathway may play an important role in initial lymphomagenesis in addition to t(11;14) translocations, and that specific mitotic regulators facilitate transformation into more aggressive forms.

Liu Y, Cai H, Liu J, et al.
A miR-151 binding site polymorphism in the 3'-untranslated region of the cyclin E1 gene associated with nasopharyngeal carcinoma.
Biochem Biophys Res Commun. 2013; 432(4):660-5 [PubMed] Related Publications
Genetic alterations in nasopharyngeal carcinoma (NPC) have been reported in previous works. However, it remains unclear whether polymorphisms within the miRNA-target binding sites are associated with individual NPC risk. In this study, new experimental and computational approaches were developed to assess the polymorphism frequency distribution within the miRNA sites in NPC patients, and to explore its association with NPC risk. We focused on 220 single-nucleotide polymorphisms (SNPs) in the 3'-untranslated regions (3'UTRs) of 32 genes carrying putative miRNA-binding sites by specialized algorithms. A total of 9 candidate genes were selected for further investigation, which were reportedly overexpressed in NPC, including EGFR, COX2, CCNE1, hTERT, MMP2, MMP9, NF-κB VEGF, and WNT3. SNPs in 3'UTRs were genotyped by direct polymerase chain reaction sequencing of the genomic DNA of 24 cases and 24 controls. Then, EGFR rs884225, CCNE1 rs3218073, and MMP2 rs7201 were screened with large samples. Based on the analysis of a series of 167 NPC cases and 171 controls from Guangdong Province, statistically significant associations were found between NPC risk and variant genotypes of CCNE1 rs3218073 for TC+TT (OR=1.585; 95% CI=1.023-2.458; P=0.046) and for T-allele (OR=1.464; 95% CI=1.012-2.118; P=0.042). In addition, a significant association among rs3218073 genotype TC (OR=1.959, P=0.043), T-allele (OR=2.123, P=0.006), and primary tumor (T3-T4) was retrieved. Genotype TC (OR=1.959, P=0.043) and T-allele (OR=2.123, P=0.006) of rs3218073 were correlated with increased risk of higher NPC stage (III to IV). In support of the postulation that the 3'UTR SNP directly affected miRNA-binding site, luciferase reporter assay indicated that CCNE1 was a direct target of miR-151, and the rs3218073 T>C change resulted in altered regulation of CCNE1 expression. By contrast, no statistically significant association with NPC risk was found for MMP2 rs7201 and EGFR rs884225 polymorphisms (P>0.05). In conclusion, our data demonstrate that CCNE1 rs3218073 polymorphism located at miRNA-151 binding site is associated with NPC susceptibility and is correlated with NPC stage. These results suggest that CCNE1 rs3218073 polymorphism can be exploited as a novel biomarker for future NPC diagnosis and prognosis.

Cha YH, Kim NH, Park C, et al.
MiRNA-34 intrinsically links p53 tumor suppressor and Wnt signaling.
Cell Cycle. 2012; 11(7):1273-81 [PubMed] Related Publications
Though tumor suppressor p53 and the canonical Wnt cascade have been extensively studied for the last 30 years, due to their important physiological roles, the two signaling pathways have been largely considered independent. Recently, the miR-34 family was found to directly link p53 and Wnt, revealing the tight connection between loss of tumor suppressor function and activation of oncogenic signaling. These observations demonstrate that miR-34, known to be directly downstream of p53, targets a set of highly conserved sites in the UTR of Wnt and EMT genes, specifically WNT1, WNT3, LRP6, AXIN2, β-catenin, LEF1 and Snail, resulting in suppression of TCF/LEF transcriptional activity and the EMT program. The loss of p53 function increases Wnt activities and promotes the Snail-dependent EMT program at multiple levels in a miR-34/UTR-specific manner. The TCF/LEF transcriptional signature was closely associated with functionality of p53 and miR-34 in clinical samples, suggesting the pervasive impact of miR-34 loss on the oncogenic pathway in human cancer. Here, we review recent findings on ceRNA in light of novel data to elucidate the physiological relevance of the p53-miR-34-Wnt network, which encompasses sets of genes and directions of signaling. As loss of wt-p53 or hyperactivation of Wnt is critical in maintaining cancer stem cell properties and in establishing the metastatic program, these observations indicate a mechanism of miR-mediated quasi-sufficiency which connects tumor suppressor and oncogenic signaling pathways, supporting a continuum model of human cancer.

Almeida MQ, Azevedo MF, Xekouki P, et al.
Activation of cyclic AMP signaling leads to different pathway alterations in lesions of the adrenal cortex caused by germline PRKAR1A defects versus those due to somatic GNAS mutations.
J Clin Endocrinol Metab. 2012; 97(4):E687-93 [PubMed] Free Access to Full Article Related Publications
CONTEXT: The overwhelming majority of benign lesions of the adrenal cortex leading to Cushing syndrome are linked to one or another abnormality of the cAMP or protein kinase pathway. PRKAR1A-inactivating mutations are responsible for primary pigmented nodular adrenocortical disease, whereas somatic GNAS activating mutations cause macronodular disease in the context of McCune-Albright syndrome, ACTH-independent macronodular hyperplasia, and, rarely, cortisol-producing adenomas.
OBJECTIVE AND DESIGN: The whole-genome expression profile (WGEP) of normal (pooled) adrenals, PRKAR1A- (3) and GNAS-mutant (3) was studied. Quantitative RT-PCR and Western blot were used to validate WGEP findings.
RESULTS: MAPK and p53 signaling pathways were highly overexpressed in all lesions against normal tissue. GNAS-mutant tissues were significantly enriched for extracellular matrix receptor interaction and focal adhesion pathways when compared with PRKAR1A-mutant (fold enrichment 3.5, P < 0.0001 and 2.1, P < 0.002, respectively). NFKB, NFKBIA, and TNFRSF1A were higher in GNAS-mutant tumors (P < 0.05). Genes related to the Wnt signaling pathway (CCND1, CTNNB1, LEF1, LRP5, WISP1, and WNT3) were overexpressed in PRKAR1A-mutant lesions.
CONCLUSION: WGEP analysis revealed that not all cAMP activation is the same: adrenal lesions harboring PRKAR1A or GNAS mutations share the downstream activation of certain oncogenic signals (such as MAPK and some cell cycle genes) but differ substantially in their effects on others.

Nishioka M, Ueno K, Hazama S, et al.
Possible involvement of Wnt11 in colorectal cancer progression.
Mol Carcinog. 2013; 52(3):207-17 [PubMed] Related Publications
Our previous report revealed that the expression of Frizzled-7 (FZD7) in colorectal cancer (CRC) and its possible role in CRC progression. In this study we measured the expression levels of candidate FZD7 ligands, Wnt3 and Wnt11 in colon cancer cell lines (n = 7) and primary CRC tissues (n = 133) by quantitative RT-PCR. We also examined the functional effects of Wnt11 with the use of Wnt11 transfectants of colon cancer HCT-116 cells. Wnt11 transfectants showed the increased proliferation and migration/invasion activities compared to mock cells. Western blot analysis of transfectants revealed that phosphorylation of JNK and c-jun was increased after Wnt11 transfection. Wnt11 mRNA expression was significantly higher in the stage I, II, III, or IV tumor tissues than in non-tumor tissues (overall P < 0.003), while there was no significant difference in Wnt3 mRNA expression between tumor and non-tumor tissues. In addition, Wnt11 mRNA expression was significantly higher in patients with recurrence or death after surgery than in those with no recurrence (disease free) after surgery (P = 0.018). We also compared the expression levels of Wnt11 mRNA with those of FZD7 mRNA in the same CRC samples. Wnt11 mRNA expression was significantly higher in patients with higher FZD7 mRNA levels than in those with lower FZD7 mRNA levels (P = 0.0005). The expression levels of Wnt11 mRNA were correlated with those of FZD7 mRNA (P < 0.0001). These data suggest that Wnt11 may play an important role in CRC progression.

Siar CH, Nagatsuka H, Han PP, et al.
Differential expression of canonical and non-canonical Wnt ligands in ameloblastoma.
J Oral Pathol Med. 2012; 41(4):332-9 [PubMed] Related Publications
BACKGROUND: Canonical and non-canonical Wnt signaling pathways modulate diverse cellular processes during embryogenesis and post-natally. Their deregulations have been implicated in cancer development and progression. Wnt signaling is essential for odontogenesis. The ameloblastoma is an odontogenic epithelial neoplasm of enamel organ origin. Altered expressions of Wnts-1, -2, -5a, and -10a are detected in this tumor. The activity of other Wnt members remains unclarified.
MATERIALS AND METHODS: Canonical (Wnts-1, -2, -3, -8a, -8b, -10a, and -10b), non-canonical (Wnts-4, -5a, -5b, -6, 7a, -7b, and -11), and indeterminate groups (Wnts-2b and -9b) were examined immunohistochemically in 72 cases of ameloblastoma (19 unicystic [UA], 35 solid/multicystic [SMA], eight desmoplastic [DA], and 10 recurrent [RA]).
RESULTS: Canonical Wnt proteins (except Wnt-10b) were heterogeneously expressed in ameloblastoma. Their distribution patterns were distinctive with some overlap. Protein localization was mainly membranous and/or cytoplasmic. Overexpression of Wnt-1 in most subsets (UA = 19/19; SMA = 35/35; DA = 5/8; RA = 7/10) (P < 0.05), Wnt-3 in granular cell variant (n = 3/3), and Wnt-8b in DA (n = 8/8) was key observations. Wnts-8a and -10a demonstrated enhanced expression in tumoral buddings and acanthomatous areas. Non-canonical and indeterminate Wnts were absent except for limited Wnt-7b immunoreactivity in UA (n = 1/19) and SMA (n = 1/35). Stromal components expressed variable Wnt positivity.
CONCLUSION: Differential expression of Wnt ligands in different ameloblastoma subtypes suggests that the canonical and non-canonical Wnt pathways are selectively activated or repressed depending on the tumor cell differentiation status. Canonical Wnt pathway is most likely the main transduction pathway while Wnt-1 might be the key signaling molecule involved in ameloblastoma tumorigenesis.

Nakashima N, Liu D, Huang CL, et al.
Wnt3 gene expression promotes tumor progression in non-small cell lung cancer.
Lung Cancer. 2012; 76(2):228-34 [PubMed] Related Publications
The Wnt gene family encodes the multi-functional signaling glycoproteins regulating various normal and pathological processes including tumorigenesis. We investigated the clinical significance of the Wnt3 gene expression in relation to its target genes, c-Myc and survivin, in patients with non-small cell lung cancer (NSCLC). One hundred and twenty-eight patients who underwent resection of NSCLC were analyzed. Quantitative reverse transcription polymerase chain reaction (RT-PCR) was performed to evaluate the gene expression of Wnt3, c-Myc, and survivin. Immunohistochemistry was performed to investigate the protein expression of Wnt3, c-Myc, and survivin. The Ki-67 proliferation index and the apoptotic index using the TUNEL method were also evaluated. Twenty-four carcinomas (18.8%) were found to be high-Wnt3 tumors. The high-Wnt3 tumors were significantly more in squamous cell carcinomas than that in adenocarcinomas (P=0.0022). The Wnt3 gene expression was significantly associated with gene expressions of c-Myc (P=0.0103) and survivin (P=0.0009). As a result, the Ki-67 proliferation index was significantly higher in high-Wnt3 tumors than in low-Wnt3 tumors (P=0.0056). The apoptotic index was significantly lower in high-Wnt3 tumors than in low-Wnt3 tumors (P=0.0245). The overall survival rate was significantly lower in patients with high-Wnt3 tumors than in those with low-Wnt3 tumors (P=0.0020). A Cox regression analysis demonstrated that the Wnt3 status was a significant prognostic factor for NSCLC patients (hazard ratio 2.226, P=0.0296). The present study revealed that Wnt3 gene expression was significantly associated with c-Myc and survivin gene expressions, tumor proliferation, and tumor apoptosis. During the progression of NSCLC, Wnt3 overexpression could be associated with the development of more aggressive tumors.

Fonar Y, Gutkovich YE, Root H, et al.
Focal adhesion kinase protein regulates Wnt3a gene expression to control cell fate specification in the developing neural plate.
Mol Biol Cell. 2011; 22(13):2409-21 [PubMed] Free Access to Full Article Related Publications
Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase protein localized to regions called focal adhesions, which are contact points between cells and the extracellular matrix. FAK protein acts as a scaffold to transfer adhesion-dependent and growth factor signals into the cell. Increased FAK expression is linked to aggressive metastatic and invasive tumors. However, little is known about its normal embryonic function. FAK protein knockdown during early Xenopus laevis development anteriorizes the embryo. Morphant embryos express increased levels of anterior neural markers, with reciprocally reduced posterior neural marker expression. Posterior neural plate folding and convergence-extension is also inhibited. This anteriorized phenotype resembles that of embryos knocked down zygotically for canonical Wnt signaling. FAK and Wnt3a genes are both expressed in the neural plate, and Wnt3a expression is FAK dependent. Ectopic Wnt expression rescues this FAK morphant anteriorized phenotype. Wnt3a thus acts downstream of FAK to balance anterior-posterior cell fate specification in the developing neural plate. Wnt3a gene expression is also FAK dependent in human breast cancer cells, suggesting that this FAK-Wnt linkage is highly conserved. This unique observation connects the FAK- and Wnt-signaling pathways, both of which act to promote cancer when aberrantly activated in mammalian cells.

Andrade Filho PA, Letra A, Cramer A, et al.
Insights from studies with oral cleft genes suggest associations between WNT-pathway genes and risk of oral cancer.
J Dent Res. 2011; 90(6):740-6 [PubMed] Free Access to Full Article Related Publications
Oral squamous cell carcinoma (OSCC) accounts for more than 90% of the malignant neoplasms that arise in the mucosa of the upper aerodigestive tract. Recent studies of cleft lip/palate have shown the association of genes involved in cancer. WNT pathway genes have been associated with several types of cancer and recently with cleft lip/palate. To investigate if genes associated with cleft lip/palate were also associated with oral cancer, we genotyped 188 individuals with OSCC and 225 control individuals for markers in AXIN2, AXIN1, GSK3β, WNT3A, WNT5A, WNT8A, WNT11, WNT3, and WNT9B. Statistical analysis was performed with PLINK 1.06 software to test for differences in allele frequencies of each polymorphism between cases and controls. We found association of SNPs in GSK3B (p = 0.0008) and WNT11 (p = 0.03) with OSCC. We also found overtransmission of GSK3B haplotypes in OSCC cases. Expression analyses showed up-regulation of WNT3A, GSK3B, and AXIN1 and down-regulation of WNT11 in OSCC in comparison with control tissues (P < 0.001). Additional studies should focus on the identification of potentially functional variants in these genes as contributors to human clefting and oral cancer.

Mödder UI, Oursler MJ, Khosla S, Monroe DG
Wnt10b activates the Wnt, notch, and NFκB pathways in U2OS osteosarcoma cells.
J Cell Biochem. 2011; 112(5):1392-402 [PubMed] Free Access to Full Article Related Publications
Although osteosarcoma represents the most common bone malignancy, the molecular and cellular mechanisms influencing its pathogenesis have remained elusive. Recent evidence has suggested that the Wnt signaling pathway may play a crucial role in osteosarcoma. This study employed a microarray approach to discover novel genes and pathways involved in Wnt signaling in osteosarcoma. We developed a Wnt10b-expressing cell line using the human U2OS osteosarcoma model (U2OS-Wnt10b) and performed microarray and pathway analyses using parental U2OS cells as control. Differential expression of 1,003 genes encompassing 28 pathways was noted. The Wnt, NFκB, and Notch pathways were chosen for further study based on their known importance in bone biology. Known Wnt-responsive genes Axin-2 (4.9-fold), CD44 (2.1-fold), endothelin-1 (4.2-fold) and sclerostin domain containing-1 (43-fold) were regulated by Wnt10b. The proinflammatory cytokines interleukin-1α and tumor necrosis factor-α, known inducers of NFκB, were upregulated both at the transcript and protein level, and NFκB reporter activity was stimulated 3.8-fold, confirming NFκB activation. Interestingly, genes involved in Notch signaling [Notch-1 (2.4-fold) and Jagged-1 (3.1-fold)] were upregulated, whereas the Notch inhibitor, lunatic fringe, was downregulated (8.2-fold). This resulted in the activation of the classic Notch-responsive genes, hairy and enhancer of split-1 (Hes-1; 2.2-fold) and hairy/enhancer-of-split related with YRPW motif-1 (Hey-1; 2.5-fold). A Hey-1 reporter construct was regulated 9.1-fold in U2OS-Wnt10b cells, confirming Notch activation. Interestingly, Wnt3a failed to induce the Notch and NFκB pathways, demonstrating Wnt-specificity. In conclusion, our data demonstrate that Wnt10b, but not Wnt3a, stimulates the NFκB and Notch pathways in U2OS osteosarcoma cells.

Yan L, Della Coletta L, Powell KL, et al.
Activation of the canonical Wnt/β-catenin pathway in ATF3-induced mammary tumors.
PLoS One. 2011; 6(1):e16515 [PubMed] Free Access to Full Article Related Publications
Female transgenic mice that constitutively overexpress the transcription factor ATF3 in the basal epithelium of the mammary gland develop mammary carcinomas with high frequency, but only if allowed to mate and raise pups early in life. This transgenic mouse model system reproduces some features of human breast cancer in that about 20% of human breast tumor specimens exhibit overexpression of ATF3 in the tumor cells. The ATF3-induced mouse tumors are phenotypically similar to mammary tumors induced by overexpression of activating Wnt/β-catenin pathway genes. We now show that the Wnt/β-catenin pathway is indeed activated in ATF3-induced tumors. β-catenin is transcriptionally up-regulated in the tumors, and high levels of nuclear β-catenin are seen in tumor cells. A reporter gene for Wnt/β-catenin pathway activity, TOPGAL, is up-regulated in the tumors and several downstream targets of Wnt signaling, including Ccnd1, Jun, Axin2 and Dkk4, are also expressed at higher levels in ATF3-induced tumors compared to mammary glands of transgenic females. Several positive-acting ligands for this pathway, including Wnt3, Wnt3a, Wnt7b, and Wnt5a, are significantly overexpressed in tumor tissue, and mRNA for Wnt3 is about 5-fold more abundant in transgenic mammary tissue than in non-transgenic mammary tissue. Two known transcriptional targets of ATF3, Snai1 and Snai2, are also overexpressed in the tumors, and Snail and Slug proteins are found to be located primarily in the nuclei of tumor cells. In vitro knockdown of Atf3 expression results in significant decreases in expression of Wnt7b, Tcf7, Snai2 and Jun, suggesting that these genes may be direct transcriptional targets of ATF3 protein. By chromatin immunoprecipitation analysis, both ATF3 and JUN proteins appear to bind to a particular subclass of AP-1 sites upstream of the transcriptional start sites of each of these genes.

Bjorklund CC, Ma W, Wang ZQ, et al.
Evidence of a role for activation of Wnt/beta-catenin signaling in the resistance of plasma cells to lenalidomide.
J Biol Chem. 2011; 286(13):11009-20 [PubMed] Free Access to Full Article Related Publications
Lenalidomide plays an important role in our chemotherapeutic armamentarium against multiple myeloma, in part by exerting direct anti-proliferative and pro-apoptotic effects. Unfortunately, long-term exposure leads to the development of drug resistance through unknown mechanisms, and we therefore sought to identify pathways that could be responsible for this phenotype. Chronic drug exposure produced myeloma cell lines that were tolerant of the direct effects of lenalidomide, with a degree of resistance of up to 2,500-fold. Gene expression profiling and pathway analysis identified dysregulation of the Wnt/β-catenin pathway as a consistent change across four independent cell isolates, and a pair of primary plasma cell samples. Acute drug treatment also increased β-catenin transcription by 3-fold or more, and both acute and chronic exposure resulted in enhanced accumulation of β-catenin protein by up to 20-fold or more. This produced Wnt/β-catenin pathway activation, as judged by increased activity of a lymphoid enhancer factor/T-cell factor promoter reporter, and enhanced accumulation of the downstream targets cyclin D1 and c-Myc. Components of the β-catenin destruction complex were also impacted by lenalidomide, which suppressed casein kinase 1α expression while augmenting glycogen synthase kinase 3α/β phosphorylation. Stimulation of Wnt/β-catenin signaling with recombinant Wnt-3a, or by overexpression of β-catenin, reduced the anti-proliferative activity of lenalidomide. Conversely, suppression of β-catenin with small hairpin RNAs restored plasma cell sensitivity to lenalidomide. Together, these findings support the hypothesis that lenalidomide mediates activation of Wnt/β-catenin signaling in plasma cells as a mechanism of inducible chemoresistance through effects at the transcriptional and post-translational levels.

Tuna M, Smid M, Zhu D, et al.
Association between acquired uniparental disomy and homozygous mutations and HER2/ER/PR status in breast cancer.
PLoS One. 2010; 5(11):e15094 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Genetic alterations in cellular signaling networks are a hallmark of cancer, however, effective methods to discover them are lacking. A novel form of abnormality called acquired uniparental disomy (aUPD) was recently found to pinpoint the region of mutated genes in various cancers, thereby identifying the region for next-generation sequencing.
METHODS/PRINCIPAL FINDINGS: We retrieved large genomic data sets from the Gene Expression Omnibus database to perform genome-wide analysis of aUPD in breast tumor samples and cell lines using approaches that can reliably detect aUPD. aUPD was identified in 52.29% of the tumor samples. The most frequent aUPD regions were located at chromosomes 2q, 3p, 5q, 9p, 9q, 10q, 11q, 13q, 14q and 17q. We evaluated the data for any correlation between the most frequent aUPD regions and HER2/neu, ER, and PR status, and found a statistically significant correlation between the recurrent regions of aUPD and triple negative (TN) breast cancers. aUPD at chromosome 17q (VEZF1, WNT3), 3p (SUMF1, GRM7), 9p (MTAP, NFIB) and 11q (CASP1, CASP4, CASP5) are predictors for TN. The frequency of aUPD was found to be significantly higher in TN breast cancer cases compared to HER2/neu-positive and/or ER or PR-positive cases. Furthermore, using previously published mutation data, we found TP53 homozygously mutated in cell lines having aUPD in that locus.
CONCLUSIONS/SIGNIFICANCE: We conclude that aUPD is a common and non-random molecular feature of breast cancer that is most prominent in triple negative cases. As aUPD regions are different among the main pathological subtypes, specific aUPD regions may aid the sub-classification of breast cancer. In addition, we provide statistical support using TP53 as an example that identifying aUPD regions can be an effective approach in finding aberrant genes. We thus conclude that a genome-wide scale analysis of aUPD regions for homozygous sequence alterations can provide valuable insights into breast tumorigenesis.

Tsuji T, Ohta Y, Kanno Y, et al.
Involvement of p114-RhoGEF and Lfc in Wnt-3a- and dishevelled-induced RhoA activation and neurite retraction in N1E-115 mouse neuroblastoma cells.
Mol Biol Cell. 2010; 21(20):3590-600 [PubMed] Free Access to Full Article Related Publications
The Wnt-induced planar cell polarity (PCP) signaling pathway is essential for polarized cell migration and morphogenesis. Dishevelled (Dvl) and its binding protein Daam1 mediate RhoA activation in this pathway. WGEF, a member of the Rho-guanine nucleotide exchange factor (Rho-GEF) family, was shown to play a role in Wnt-induced RhoA activation in Xenopus embryos. However, it has remained unknown which member(s) of a Rho-GEF family are involved in Wnt/Dvl-induced RhoA activation in mammalian cells. Here we identified p114-RhoGEF and Lfc (also called GEF-H1) as the Rho-GEFs responsible for Wnt-3a-induced RhoA activation in N1E-115 mouse neuroblastoma cells. We screened for Rho-GEF-silencing short-hairpin RNAs (shRNAs) that are capable of suppressing Dvl-induced neurite retraction in N1E-115 cells and found that p114-RhoGEF and Lfc shRNAs, but not WGEF shRNA, suppressed Dvl- and Wnt-3a-induced neurite retraction. p114-RhoGEF and Lfc shRNAs also inhibited Dvl- and Wnt-3a-induced RhoA activation, and p114-RhoGEF and Lfc proteins were capable of binding to Dvl and Daam1. Additionally, the Dvl-binding domains of p114-RhoGEF and Lfc inhibited Dvl-induced neurite retraction. Our results suggest that p114-RhoGEF and Lfc are critically involved in Wnt-3a- and Dvl-induced RhoA activation and neurite retraction in N1E-115 cells.

Lai JP, Oseini AM, Moser CD, et al.
The oncogenic effect of sulfatase 2 in human hepatocellular carcinoma is mediated in part by glypican 3-dependent Wnt activation.
Hepatology. 2010; 52(5):1680-9 [PubMed] Free Access to Full Article Related Publications
UNLABELLED: Heparan sulfate proteoglycans (HSPGs) act as coreceptors or storage sites for growth factors and cytokines such as fibroblast growth factor and Wnts. Glypican 3 (GPC3) is the most highly expressed HSPG in hepatocellular carcinoma (HCC). Sulfatase 2 (SULF2), an enzyme with 6-O-desulfatase activity on HSPGs, is up-regulated in 60% of primary HCCs and is associated with a worse prognosis. We have previously shown that the oncogenic effect of SULF2 in HCC may be mediated in part through up-regulation of GPC3. Here we demonstrate that GPC3 stimulates the Wnt/β-catenin pathway and mediates the oncogenic function of SULF2 in HCC. Wnt signaling in vitro and in vivo was assessed in SULF2-negative Hep3B HCC cells transfected with SULF2 and in SULF2-expressing Huh7 cells transfected with short hairpin RNA targeting SULF2. The interaction between GPC3, SULF2, and Wnt3a was assessed by coimmunoprecipitation and flow cytometry. β-catenin-dependent transcriptional activity was assessed with the TOPFLASH (T cell factor reporter plasmid) luciferase assay. In HCC cells, SULF2 increased cell surface GPC3 and Wnt3a expression, stabilized β-catenin, and activated T cell factor transcription factor activity and expression of the Wnt/β-catenin target gene cyclin D1. Opposite effects were observed in SULF2-knockdown models. In vivo, nude mouse xenografts established from SULF2-transfected Hep3B cells showed enhanced GPC3, Wnt3a, and β-catenin levels.
CONCLUSION: Together, these findings identify a novel mechanism mediating the oncogenic function of SULF2 in HCC that includes GPC3-mediated activation of Wnt signaling via the Wnt3a/glycogen synthase kinase 3 beta axis.

von Marschall Z, Fisher LW
Secreted Frizzled-related protein-2 (sFRP2) augments canonical Wnt3a-induced signaling.
Biochem Biophys Res Commun. 2010; 400(3):299-304 [PubMed] Free Access to Full Article Related Publications
Secreted Frizzled-related proteins (sFRP) are involved in embryonic development as well as pathological conditions including bone and myocardial disorders and cancer. Because of their sequence homology with the Wnt-binding domain of Frizzled, they have generally been considered antagonists of canonical Wnt signaling. However, additional activities of various sFRPs including both synergism and mimicry of Wnt signaling as well as functions other than modulation of Wnt signaling have been reported. Using human embryonic kidney cells (HEK293A), we found that sFRP2 enhanced Wnt3a-dependent phosphorylation of LRP6 as well as both cytosolic β-catenin levels and its nuclear translocation. While addition of recombinant sFRP2 had no activity by itself, Top/Fop luciferase reporter assays showed a dose-dependent increase of Wnt3a-mediated transcriptional activity. sFRP2 enhancement of Wnt3a signaling was abolished by treatment with the Wnt antagonist, Dickkopf-1 (DKK1). Wnt-signaling pathway qPCR arrays showed that sFRP2 enhanced the Wnt3a-mediated transcriptional up-regulation of several genes regulated by Wnt3a including its antagonists, DKK1, and Naked cuticle-1 homolog (NKD1). These results support sFRP2's role as an enhancer of Wnt/β-catenin signaling, a result with biological impact for both normal development and diverse pathologies such as tumorigenesis.

Liu P, Yang J, Pei J, et al.
Regulation of MT1-MMP activity by β-catenin in MDCK non-cancer and HT1080 cancer cells.
J Cell Physiol. 2010; 225(3):810-21 [PubMed] Free Access to Full Article Related Publications
Past studies on β-catenin in cancer cells focused on nuclear localized β-catenin and its involvement in the Wnt pathway. Our goal here was to investigate the function of β-catenin in both the cytoplasm and nucleus on the regulation of MT1-MMP expression and activity. We found that β-catenin in MDCK non-cancer cells inhibited the cell surface localization of MT1-MMP, and thus its proteolytic activity on pro-MMP2 activation, via direct interaction with the 18-amino-acid cytoplasmic tail of MT1-MMP in the cytoplasm. In contrast, β-catenin in HT1080 cancer cells enhanced the activity of MT1-MMP by entering the nucleus and activating transcription factor Tcf-4/Lef, and elevating the level of MT1-MMP protein. We also found that enhancement of cell growth in three-dimensional (3-D)/two-dimensional (2-D) type I collagen gels and of cell migration by MT1-MMP were inhibited by β-catenin in MDCK cells, whereas these functions were enhanced in HT1080 cells. In addition, regulation of MT1-MMP by β-catenin involved E-cadherin in MDCK cells and Wnt-3a in HT1080 cells. Taken together, our results present a differential effect of cytoplasmic and nuclear β-catenin on MT1-MMP activity in non-cancer cells versus cancer cells. These differences were most probably due to different subcellular locations and different involved pathways of β-catenin in these cells.

Kang DW, Lee SH, Yoon JW, et al.
Phospholipase D1 drives a positive feedback loop to reinforce the Wnt/beta-catenin/TCF signaling axis.
Cancer Res. 2010; 70(10):4233-42 [PubMed] Related Publications
Activation of the Wnt signaling pathway occurs frequently in human cancers, but an understanding of the targets and regulation of this important pathway remains incomplete. In this study, we report that phospholipase D (PLD), a cell survival mediator that is upregulated in cancer, is an important target of the Wnt signaling pathway that functions in a positive feedback loop to reinforce pathway output. PLD1 expression and activity was enhanced by treatment with Wnt3a and glycogen synthase kinase-3 inhibitors, and the Wnt pathway-regulated transcription factors beta-catenin and TCF-4 were required for this effect. Three functional TCF-4-binding sites were identified within the PLD1 promoter. Interestingly, suppressing PLD1 blocked the ability of beta-catenin to transcriptionally activate PLD1 and other Wnt target genes by preventing beta-catenin/TCF-4 complex formation. Conversely, tactics to elevate intracellular levels of phosphatidic acid, the product of PLD1 enzyme activity, enhanced beta-catenin/TCF-4 complex formation as well as beta-catenin-dependent TCF transcriptional activity. In cell-based assays, PLD1 was necessary for the anchorage-independent growth driven by Wnt/beta-catenin signaling, whereas beta-catenin/TCF-4 was necessary for the anchorage-independent growth driven by PLD1 activation. Taken together, our findings define a function for PLD1 in a positive feedback loop of Wnt/beta-catenin/TCF-4 signaling that provides new mechanistic insights into cancer, with implications of novel strategies to disrupt Wnt signaling in cancer.

Gujral TS, MacBeath G
A system-wide investigation of the dynamics of Wnt signaling reveals novel phases of transcriptional regulation.
PLoS One. 2010; 5(4):e10024 [PubMed] Free Access to Full Article Related Publications
Aberrant Wnt signaling has been implicated in a wide variety of cancers and many components of the Wnt signaling network have now been identified. Much less is known, however, about how these proteins are coordinately regulated. Here, a broad, quantitative, and dynamic study of Wnt3a-mediated stimulation of HEK 293 cells revealed two phases of transcriptional regulation: an early phase in which signaling antagonists were downregulated, providing positive feedback, and a later phase in which many of these same antagonists were upregulated, attenuating signaling. The dynamic expression profiles of several response genes, including MYC and CTBP1, correlated significantly with proliferation and migration (P<0.05). Additionally, their levels tracked with the tumorigenicity of colon cancer cell lines and they were significantly overexpressed in colorectal adenocarcinomas (P<0.05). Our data highlight CtBP1 as a transcription factor that contributes to positive feedback during the early phases of Wnt signaling and serves as a novel marker for colorectal cancer progression.

Tauriello DV, Haegebarth A, Kuper I, et al.
Loss of the tumor suppressor CYLD enhances Wnt/beta-catenin signaling through K63-linked ubiquitination of Dvl.
Mol Cell. 2010; 37(5):607-19 [PubMed] Related Publications
The mechanism by which Wnt receptors transduce signals to activate downstream beta-catenin-mediated target gene transcription remains incompletely understood but involves Frizzled (Fz) receptor-mediated plasma membrane recruitment and activation of the cytoplasmic effector Dishevelled (Dvl). Here, we identify the deubiquitinating enzyme CYLD, the familial cylindromatosis tumor suppressor gene, as a negative regulator of proximal events in Wnt/beta-catenin signaling. Depletion of CYLD from cultured cells markedly enhances Wnt-induced accumulation of beta-catenin and target gene activation. Moreover, we demonstrate hyperactive Wnt signaling in human cylindroma skin tumors that arise from mutations in CYLD. At the molecular level, CYLD interacts with and regulates K63-linked ubiquitination of Dvl. Enhanced ubiquitination of the polymerization-prone DIX domain in CYLD-deficient cells positively links to the signaling activity of Dvl. Together, our results argue that loss of CYLD instigates tumor growth in human cylindromatosis through a mechanism in which hyperubiquitination of polymerized Dvl drives enhancement of Wnt responses.

Cai Y, Mohseny AB, Karperien M, et al.
Inactive Wnt/beta-catenin pathway in conventional high-grade osteosarcoma.
J Pathol. 2010; 220(1):24-33 [PubMed] Related Publications
Osteosarcoma is the most common malignant bone tumour, with a peak incidence in children and young adolescents, suggesting a role of rapid bone growth in its pathogenesis. The Wnt/beta-catenin pathway plays a crucial role in skeletal development and is indispensable for osteoblasts' lineage determination. Previous studies suggesting an oncogenic role for the Wnt/beta-catenin pathway in osteosarcoma were based on cytoplasmic staining of beta-catenin or the detection of one component of this pathway. However, those approaches are inappropriate to address whether the Wnt/beta-catenin pathway is functionally active. Therefore, in this study, we examined nuclear beta-catenin expression in 52 human osteosarcoma biopsies, 15 osteoblastomas (benign bone tumours), and four human osteosarcoma cell lines by immunohistochemistry. Furthermore, we modulated Wnt/beta-catenin pathway activity using a GIN (GSK3beta inhibitor) and evaluated its effect on cell growth and osteogenic differentiation. Absence of nuclear beta-catenin staining was found in 90% of the biopsies and all osteosarcoma cell lines, whereas strong nuclear beta-catenin staining was observed in all osteoblastomas. Wnt-luciferase activity was comparable to the negative control in all osteosarcoma cell lines. GIN stimulated the Wnt/beta-catenin pathway, as shown by translocation of beta-catenin into the nucleus and increased Wnt-luciferase activity as well as mRNA expression of AXIN2, a specific downstream target gene. Stimulation of the Wnt/beta-catenin pathway by GIN significantly reduced cell proliferation in the cell lines MG-63 and U-2-OS and enhanced differentiation in the cell lines HOS and SJSA-1, as shown by an increase in alkaline phosphatase (ALP) activity and mineralization. In contrast with the oncogenic role of the Wnt/beta-catenin pathway in osteosarcoma as previous studies suggested, here we demonstrate that this pathway is inactivated in osteosarcoma. Moreover, activation of the Wnt/beta-catenin pathway inhibits cell proliferation or promotes osteogenic differentiation in osteosarcoma cell lines. Our data suggest that loss of Wnt/beta-catenin pathway activity, which is required for osteoblast differentiation, may contribute to osteosarcoma development.

Zhang J, Li Y, Liu Q, et al.
Wnt signaling activation and mammary gland hyperplasia in MMTV-LRP6 transgenic mice: implication for breast cancer tumorigenesis.
Oncogene. 2010; 29(4):539-49 [PubMed] Free Access to Full Article Related Publications
Although Wnt signaling activation is frequently observed in human breast cancer, mutations in genes encoding intracellular components of the Wnt signaling pathway are rare. We found that the expression of Wnt signaling co-receptor, LRP6, is upregulated in a subset of human breast cancer tissues and cell lines. To examine whether the overexpression of LRP6 in mammary epithelial cells is sufficient to activate Wnt signaling and promote cell proliferation, we generated transgenic mice overexpressing LRP6 in mammary epithelial cells driven by the mouse mammary tumor virus (MMTV) promoter. We found that mammary glands from MMTV-LRP6 mice exhibit significant Wnt activation evidenced by the translocation of beta-catenin from membrane to cytoplasmic/nuclear fractions. The expression of several Wnt target genes including Axin2, Cyclin D1 and c-Myc was also increased in MMTV-LRP6 mice. More importantly, mammary glands from virgin MMTV-LRP6 mice exhibit significant hyperplasia, a precursor to breast cancer, when compared with wild-type littermate controls. Several matrix metalloproteinases are upregulated in MMTV-LRP6 mice that could contribute to the hyperplasia phenotype. Our results suggest that Wnt signaling activation at the cell-surface receptor level can contribute to breast cancer tumorigenesis.

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