Wnt/β-Catenin/Tcf Signaling Induces the Transcription of Axin2, a Negative Regulator of the Signaling Pathway

ABSTRACT Axin2/Conductin/Axil and its ortholog Axin are negative regulators of the Wnt signaling pathway, which promote the phosphorylation and degradation of β-catenin. While Axin is expressed ubiquitously, Axin2 mRNA was seen in a restricted pattern during mouse embryogenesis and organogenesis. Because many sites of Axin2 expression overlapped with those of several Wnt genes, we tested whether Axin2 was induced by Wnt signaling. Endogenous Axin2 mRNA and protein expression could be rapidly induced by activation of the Wnt pathway, and Axin2 reporter constructs, containing a 5.6-kb DNA fragment including the promoter and first intron, were also induced. This genomic region contains eight Tcf/LEF consensus binding sites, five of which are located within longer, highly conserved noncoding sequences. The mutation or deletion of these Tcf/LEF sites greatly diminished induction by β-catenin, and mutation of the Tcf/LEF site T2 abolished protein binding in an electrophoretic mobility shift assay. These results strongly suggest that Axin2 is a direct target of the Wnt pathway, mediated through Tcf/LEF factors. The 5.6-kb genomic sequence was sufficient to direct the tissue-specific expression of d2EGFP in transgenic embryos, consistent with a role for the Tcf/LEF sites and surrounding conserved sequences in the in vivo expression pattern of Axin2. Our results suggest that Axin2 participates in a negative feedback loop, which could serve to limit the duration or intensity of a Wnt-initiated signal.

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The microRNA miR-8 is a conserved negative regulator of Wnt signaling

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0807763105 ◽

2008 ◽

Vol 105 (40) ◽

pp. 15417-15422 ◽

Cited By ~ 130

Author(s):

Jennifer A. Kennell ◽

Isabelle Gerin ◽

Ormond A. MacDougald ◽

Ken M. Cadigan

Keyword(s):

Wnt Signaling ◽

Signaling Pathway ◽

Target Genes ◽

Wnt Signaling Pathway ◽

Negative Regulator ◽

Animal Development ◽

Protein Levels ◽

Evolutionarily Conserved ◽

Multiple Levels

Wnt signaling plays many important roles in animal development. This evolutionarily conserved signaling pathway is highly regulated at all levels. To identify regulators of the Wnt/Wingless (Wg) pathway, we performed a genetic screen in Drosophila. We identified the microRNA miR-8 as an inhibitor of Wg signaling. Expression of miR-8 potently antagonizes Wg signaling in vivo, in part by directly targeting wntless, a gene required for Wg secretion. In addition, miR-8 inhibits the pathway downstream of the Wg signal by repressing TCF protein levels. Another positive regulator of the pathway, CG32767, is also targeted by miR-8. Our data suggest that miR-8 potently antagonizes the Wg pathway at multiple levels, from secretion of the ligand to transcription of target genes. In addition, mammalian homologues of miR-8 promote adipogenesis of marrow stromal cells by inhibiting Wnt signaling. These findings indicate that miR-8 family members play an evolutionarily conserved role in regulating the Wnt signaling pathway.

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Overexpression of ICAT Inhibits the Progression of Colorectal Cancer by Binding with β-Catenin in the Cytoplasm

Technology in Cancer Research & Treatment ◽

10.1177/15330338211041253 ◽

2021 ◽

Vol 20 ◽

pp. 153303382110412

Author(s):

Jiancong Hu ◽

Zihan Wang ◽

Junxiong Chen ◽

Zhaoliang Yu ◽

Jingdan Zhang ◽

...

Keyword(s):

Colorectal Cancer ◽

Cell Proliferation ◽

Wnt Signaling ◽

Signaling Pathway ◽

Transcriptional Activity ◽

Wnt Pathway ◽

Wnt Signaling Pathway ◽

T Cell Factor

Inhibitor of β-catenin and T-cell factor (ICAT) was first found as a polypeptide that blocks β-catenin–TCF interaction. Abundant evidence has shown that ICAT has different functions in diverse cancers’ progression. Nevertheless, the roles it plays in colorectal cancer (CRC) have not been described. Here, we documented that ICAT expression was higher in CRC tissue than in the adjacent normal tissue and that prognosis was better in high-ICAT expression patients. The overexpression of ICAT inhibited CRC cell proliferation both in vitro and in vivo. Wnt pathway transcriptional activity was suppressed in the CRC cells with ICAT overexpression, where the CCND1 and MYC expression, which occurs downstream of the Wnt signaling pathway, was inhibited. Co-immunoprecipitation experiments showed that ICAT bound with β-catenin in stable overexpression cell lines; immunofluorescence showed the co-localization of ICAT and β-catenin in the cytoplasm. Overall, our study reveals that ICAT inhibits CRC cell proliferation by binding to cytoplasm-located β-catenin, and prevents its translocation, which results in Wnt signaling pathway inactivation. It may provide a scientific foundation for focusing on ICAT in treatments for CRC.

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DNA methylation mediated RSPO2 to promote follicular development in mammals

Cell Death and Disease ◽

10.1038/s41419-021-03941-z ◽

2021 ◽

Vol 12 (7) ◽

Author(s):

Xiaofeng Zhou ◽

Yingting He ◽

Nian Li ◽

Guofeng Bai ◽

Xiangchun Pan ◽

...

Keyword(s):

Dna Methylation ◽

Wnt Signaling ◽

Signaling Pathway ◽

Methylation Level ◽

Molecular Mechanisms ◽

Cpg Island ◽

Wnt Signaling Pathway ◽

Follicular Development ◽

Expression Level

AbstractIn female mammals, the proliferation, apoptosis, and estradiol-17β (E2) secretion of granulosa cells (GCs) have come to decide the fate of follicles. DNA methylation and RSPO2 gene of Wnt signaling pathway have been reported to involve in the survival of GCs and follicular development. However, the molecular mechanisms for how DNA methylation regulates the expression of RSPO2 and participates in the follicular development are not clear. In this study, we found that the mRNA and protein levels of RSPO2 significantly increased during follicular development, but the DNA methylation level of RSPO2 promoter decreased gradually. Inhibition of DNA methylation or DNMT1 knockdown could decrease the methylation level of CpG island (CGI) in RSPO2 promoter and upregulate the expression level of RSPO2 in porcine GCs. The hypomethylation of −758/−749 and −563/−553 regions in RSPO2 promoter facilitated the occupancy of transcription factor E2F1 and promoted the transcriptional activity of RSPO2. Moreover, RSPO2 promoted the proliferation of GCs with increasing the expression level of PCNA, CDK1, and CCND1 and promoted the E2 secretion of GCs with increasing the expression level of CYP19A1 and HSD17B1 and inhibited the apoptosis of GCs with decreasing the expression level of Caspase3, cleaved Caspase3, cleaved Caspase8, cleaved Caspase9, cleaved PARP, and BAX. In addition, RSPO2 knockdown promoted the apoptosis of GCs, blocked the development of follicles, and delayed the onset of puberty with decreasing the expression level of Wnt signaling pathway-related genes (LGR4 and CTNNB1) in vivo. Taken together, the hypomethylation of −758/−749 and −563/−553 regions in RSPO2 promoter facilitated the occupancy of E2F1 and enhanced the transcription of RSPO2, which further promoted the proliferation and E2 secretion of GCs, inhibited the apoptosis of GCs, and ultimately ameliorated the development of follicles through Wnt signaling pathway. This study will provide useful information for further exploration on DNA-methylation-mediated RSPO2 pathway during follicular development.

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Dickkopf Wnt signaling pathway inhibitor 1 regulates the differentiation of mouse embryonic stem cells in vitro and in vivo

Molecular Medicine Reports ◽

10.3892/mmr.2015.4586 ◽

2015 ◽

Vol 13 (1) ◽

pp. 720-730 ◽

Cited By ~ 8

Author(s):

LIPING OU ◽

LIAOQIONG FANG ◽

HEJING TANG ◽

HAI QIAO ◽

XIAOMEI ZHANG ◽

...

Keyword(s):

Stem Cells ◽

Embryonic Stem Cells ◽

Wnt Signaling ◽

Signaling Pathway ◽

Wnt Signaling Pathway ◽

Embryonic Stem ◽

Mouse Embryonic Stem Cells

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Silencing of long noncoding RNA HOXA11-AS inhibits the Wnt signaling pathway via the upregulation of HOXA11 and thereby inhibits the proliferation, invasion, and self-renewal of hepatocellular carcinoma stem cells

Experimental & Molecular Medicine ◽

10.1038/s12276-019-0328-x ◽

2019 ◽

Vol 51 (11) ◽

pp. 1-20 ◽

Cited By ~ 2

Author(s):

Jun-Cheng Guo ◽

Yi-Jun Yang ◽

Jin-Fang Zheng ◽

Jian-Quan Zhang ◽

Min Guo ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Stem Cells ◽

Stem Cell ◽

Wnt Signaling ◽

Signaling Pathway ◽

Methylation Level ◽

Wnt Signaling Pathway ◽

The Self ◽

Self Renewal

AbstractHepatocellular carcinoma (HCC) is a major cause of cancer-related deaths, but its molecular mechanisms are not yet well characterized. Long noncoding RNAs (lncRNAs) play crucial roles in tumorigenesis, including that of HCC. However, the role of homeobox A11 antisense (HOXA11-AS) in determining HCC stem cell characteristics remains to be explained; hence, this study aimed to investigate the effects of HOXA11-AS on HCC stem cell characteristics. Initially, the expression patterns of HOXA11-AS and HOXA11 in HCC tissues, cells, and stem cells were determined. HCC stem cells, successfully sorted from Hep3B and Huh7 cells, were transfected with short hairpin or overexpression plasmids for HOXA11-AS or HOXA11 overexpression and depletion, with an aim to study the influences of these mediators on the self-renewal, proliferation, migration, and tumorigenicity of HCC stem cells in vivo. Additionally, the potential relationship and the regulatory mechanisms that link HOXA11-AS, HOXA11, and the Wnt signaling pathway were explored through treatment with Dickkopf-1 (a Wnt signaling pathway inhibitor). HCC stem cells showed high expression of HOXA11-AS and low expression of HOXA11. Both HOXA11-AS silencing and HOXA11 overexpression suppressed the self-renewal, proliferation, migration, and tumorigenicity of HCC stem cells in vivo, as evidenced by the decreased expression of cancer stem cell surface markers (CD133 and CD44) and stemness-related transcription factors (Nanog, Sox2, and Oct4). Moreover, silencing HOXA11-AS inactivated the Wnt signaling pathway by decreasing the methylation level of the HOXA11 promoter, thereby inhibiting HCC stem cell characteristics. Collectively, this study suggested that HOXA11-AS silencing exerts an antitumor effect, suppressing HCC development via Wnt signaling pathway inactivation by decreasing the methylation level of the HOXA11 promoter.

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Modulation of Calretinin Expression in Human Mesothelioma Cells Reveals the Implication of the FAK and Wnt Signaling Pathways in Conferring Chemoresistance towards Cisplatin

International Journal of Molecular Sciences ◽

10.3390/ijms20215391 ◽

2019 ◽

Vol 20 (21) ◽

pp. 5391 ◽

Cited By ~ 5

Author(s):

Wörthmüller ◽

Salicio ◽

Oberson ◽

Blum ◽

Schwaller

Keyword(s):

Wnt Signaling ◽

Signaling Pathways ◽

Signaling Pathway ◽

Expression System ◽

Single Agent ◽

Wnt Signaling Pathway ◽

Tumor Formation ◽

Mesenchymal Transition

Malignant mesothelioma (MM) is an aggressive asbestos-linked neoplasm, characterized by dysregulation of signaling pathways. Due to intrinsic or acquired chemoresistance, MM treatment options remain limited. Calretinin is a Ca2+-binding protein expressed during MM tumorigenesis that activates the FAK signaling pathway, promoting invasion and epithelial-to-mesenchymal transition. Constitutive calretinin downregulation decreases MM cells’ growth and survival, and impairs tumor formation in vivo. In order to evaluate early molecular events occurring during calretinin downregulation, we generated a tightly controlled IPTG-inducible expression system to modulate calretinin levels in vitro. Calretinin downregulation significantly reduced viability and proliferation of MM cells, attenuated FAK signaling and reduced the invasive phenotype of surviving cells. Importantly, surviving cells showed a higher resistance to cisplatin due to increased Wnt signaling. This resistance was abrogated by the Wnt signaling pathway inhibitor 3289-8625. In various MM cell lines and regardless of calretinin expression levels, blocking of FAK signaling activated the Wnt signaling pathway and vice versa. Thus, blocking both pathways had the strongest impact on MM cell proliferation and survival. Chemoresistance mechanisms in MM cells have resulted in a failure of single-agent therapies. Targeting of multiple components of key signaling pathways, including Wnt signaling, might be the future method-of-choice to treat MM.

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A Context-Dependent Role for the RNF146 Ubiquitin Ligase in Wingless/Wnt Signaling in Drosophila

Genetics ◽

10.1534/genetics.118.301393 ◽

2018 ◽

Vol 211 (3) ◽

pp. 913-923 ◽

Cited By ~ 3

Author(s):

Zhenghan Wang ◽

Ofelia Tacchelly-Benites ◽

Geoffrey P. Noble ◽

Megan K. Johnson ◽

Jean-Philippe Gagné ◽

...

Keyword(s):

Wnt Signaling ◽

Ubiquitin Ligase ◽

Wnt Pathway ◽

Gene Activation ◽

Negative Regulator ◽

Compensatory Mechanisms ◽

E3 Ligases ◽

Pathway Activation ◽

Wingless Signaling

Aberrant activation of the Wnt signal transduction pathway triggers the development of colorectal cancer. The ADP-ribose polymerase Tankyrase (TNKS) mediates proteolysis of Axin—a negative regulator of Wnt signaling—and provides a promising therapeutic target for Wnt-driven diseases. Proteolysis of TNKS substrates is mediated through their ubiquitination by the poly-ADP-ribose (pADPr)-dependent RING-domain E3 ubiquitin ligase RNF146/Iduna. Like TNKS, RNF146 promotes Axin proteolysis and Wnt pathway activation in some cultured cell lines, but in contrast with TNKS, RNF146 is dispensable for Axin degradation in colorectal carcinoma cells. Thus, the contexts in which RNF146 is essential for TNKS-mediated Axin destabilization and Wnt signaling remain uncertain. Herein, we tested the requirement for RNF146 in TNKS-mediated Axin proteolysis and Wnt pathway activation in a range of in vivo settings. Using null mutants in Drosophila, we provide genetic and biochemical evidence that Rnf146 and Tnks function in the same proteolysis pathway in vivo. Furthermore, like Tnks, Drosophila Rnf146 promotes Wingless signaling in multiple developmental contexts by buffering Axin levels to ensure they remain below the threshold at which Wingless signaling is inhibited. However, in contrast with Tnks, Rnf146 is dispensable for Wingless target gene activation and the Wingless-dependent control of intestinal stem cell proliferation in the adult midgut during homeostasis. Together, these findings demonstrate that the requirement for Rnf146 in Tnks-mediated Axin proteolysis and Wingless pathway activation is dependent on physiological context, and suggest that, in some cell types, functionally redundant pADPr-dependent E3 ligases or other compensatory mechanisms promote the Tnks-dependent proteolysis of Axin in both mammalian and Drosophila cells.

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Replicating Adenoviruses That Target Tumors with Constitutive Activation of the wnt Signaling Pathway

Journal of Virology ◽

10.1128/jvi.75.6.2857-2865.2001 ◽

2001 ◽

Vol 75 (6) ◽

pp. 2857-2865 ◽

Cited By ~ 51

Author(s):

Michele Brunori ◽

Maddalena Malerba ◽

Haruhiko Kashiwazaki ◽

Richard Iggo

Keyword(s):

Wnt Signaling ◽

Cancer Cells ◽

Wnt Pathway ◽

Wnt Signaling Pathway ◽

Lung Model ◽

Colorectal Tumors ◽

Colon Tumors ◽

Treat All

ABSTRACT Despite important advances in understanding the molecular basis of cancer, few treatments have been devised which rationally target known causal oncogenic defects. Selectively replicating viruses have a major advantage over nonreplicating viruses to target these defects because the therapeutic effect of the injected virus is augmented by virus produced within the tumor. To permit rational targeting of colon tumors, we have developed replicating adenoviruses that express the viral E1B and E2 genes from promoters controlled by the Tcf4 transcription factor. Tcf4 is constitutively activated by mutations in the adenomatous polyposis coli and β-catenin genes in virtually all colon tumors and is constitutively repressed by Groucho and CtBP in normal tissue. The Tcf-E2 and Tcf-E1B promoters are active in many, but not all, cell lines with activation of the wnt pathway. Viruses with Tcf regulation of E2 expression replicate normally in SW480 colon cancer cells but show a 50- to 100-fold decrease in replication in H1299 lung cancer cells and WI38 normal fibroblasts. Activation of wnt signaling by transduction of a stable β-catenin mutant into normal fibroblasts renders the cells permissive for virus replication. Insertion of Tcf4 sites in the E1B promoter has only small effects on replication in vitro but significantly reduces the inflammatory response in a rodent lung model in vivo. Replicating adenoviruses with Tcf regulation of both E1B and E2 transcription are potentially useful for the treatment of liver metastases from colorectal tumors, but additional changes will be required to produce a virus that can be used to treat all colon tumors.

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AML Survival and In Vivo Progression Is Dependent On β-Catenin Signaling.

Blood ◽

10.1182/blood.v114.22.2398.2398 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2398-2398

Author(s):

Elena K Siapati ◽

Magda Papadaki ◽

Zoi Kozaou ◽

Erasmia Rouka ◽

Evridiki Michali ◽

...

Keyword(s):

Bone Marrow ◽

Wnt Signaling ◽

Signaling Pathway ◽

Cell Lines ◽

Wnt Signaling Pathway ◽

Canonical Wnt Signaling ◽

Down Regulation ◽

Canonical Wnt

Abstract Abstract 2398 Poster Board II-375 B-catenin is the central effector molecule of the canonical wnt signaling pathway which governs cell fate and differentiation during embryogenesis as well as self-renewal of hematopoietic stem cells. Deregulation of the pathway has been observed in various malignancies including myeloid leukemias where over-expression of β-catenin is an independent adverse prognostic factor. In the present study we examined the functional outcome of stable β-catenin down-regulation through lentivirus-mediated expression of short hairpin RNA (shRNA). Reduction of the β-catenin levels in AML cell lines and patient samples diminished their in vitro proliferation ability without significantly affecting cell viability. In order to study the role of β-catenin in vivo, we transplanted leukemic cell lines with control or reduced levels of β-catenin in NOD/SCID animals and analyzed the engraftment levels in the bone marrow. We observed that while the immediate homing of the cells was not affected by the β-catenin levels, the bone marrow engraftment was directly dependent on its levels. Subsequent examination of bone marrow sections revealed that the reduced engraftment was partly due to the inability of the cells with lower β-catenin levels to dock to the endosteal niches, a finding that was confirmed in competitive repopulation assays with untransduced cells. When we examined the expression levels of adhesion molecules and integrins in engrafted cells in vivo, we observed a significant down-regulation of CD44 expression, a molecule that participates in the interaction of HSCs with the niche. Gene expression analysis of the components of the wnt signaling pathway showed that the pathway is subject to tight transcriptional regulation with minor expression deviations. We did, however, observe an up-regulation in components that participate in the non-canonical wnt signaling pathways such as the WNT5B ligand. Ongoing experiments in normal cord blood CD34+ cells will determine the in vivo role of β-catenin signaling in normal hematopoietic progenitors. In conclusion, our study showed that β-catenin comprises an integral part in the development and progression of AML in vivo, indicating that manipulation of the wnt pathway may hold a therapeutic potential in the management of AML. Disclosures: No relevant conflicts of interest to declare.

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