Activation Of Beta-catenin Signaling Research Articles

Inhibition of BMP signaling with LDN 193189 can influence bone marrow stromal cell fate but does not prevent hypertrophy during chondrogenesis.

SummaryBone morphogenetic protein (BMP) cascades are upregulated during bone marrow-derived stromal cell (BMSC) chondrogenesis, contributing to hypertrophy and preventing effective BMSC-mediated cartilage repair. Previous work demonstrated that a proprietary BMP inhibitor prevented BMSC hypertrophy, yielding stable cartilage tissue. Because of the significant therapeutic potential of a molecule capable of hypertrophy blockade, we evaluated the capacity of a commercially available BMP type I receptor inhibitor with similar properties, LDN 193189, to prevent BMSC hypertrophy. Using 14-day microtissue chondrogenic induction cultures we found that LDN 193189 permitted BMSC chondrogenesis but did not prevent hypertrophy. LDN 193189 was sufficiently potent to counter mineralization and adipogenesis in response to exogenous BMP-2 in osteogenic induction cultures. LDN 193189 did not modify BMSC behavior in adipogenic induction cultures. Although LDN 193189 is effective in countering BMP signaling in a manner that influences BMSC fate, this blockade is insufficient to prevent hypertrophy.

IDO in Colorectal Tumorigenesis: Involvement of Immune Tolerance and Significance in Prevention and Therapy

IDO in Colorectal Tumorigenesis: Involvement of Immune Tolerance and Significance in Prevention and Therapy

Activated Beta-Catenin Signaling Ameliorates Radiation-Induced Skin Injury by Suppressing Marvel D3 Expression.

Radiation-induced skin injury remains a serious concern for cancer radiotherapy, radiation accidents and occupational exposure, and the damage mainly occurs due to apoptosis and reactive oxygen species (ROS) generation. There is currently no effective treatment for this disorder. The β-catenin signaling pathway is involved in the repair and regeneration of injured tissues. However, the role of the β-catenin signaling pathway in radiation-induced skin injury has not been reported. In this study, we demonstrated that the β-catenin signaling pathway was activated in response to radiation and that its activation by Wnt3a, a ligand-protein involved in the β-catenin signaling pathway, inhibited apoptosis and the production of ROS in irradiated human keratinocyte HaCaT cells and skin fibroblast WS1 cells. Additionally, Wnt3a promoted cell migration after irradiation. In a mouse model of full-thickness skin wounds combined with total-body irradiation, Wnt3a was shown to facilitate skin wound healing. The results from RNA-Seq revealed that 24 genes were upregulated and 154 were downregulated in Wnt3a-treated irradiated skin cells, and these dysregulated genes were mainly enriched in the tight junction pathway. Among them, Marvel D3 showed the most obvious difference. We further found that the activated β-catenin signaling pathway stimulated the phosphorylation of JNK by silencing Marvel D3. Treatment of irradiated cells with SP600125, a JNK inhibitor, augmented ROS production and impeded cell migration. Furthermore, treatment with Wnt3a or transfection with Marvel D3-specific siRNAs could reverse the above effects. Taken together, these findings illustrate that activated β-catenin signaling stimulates the activation of JNK by negatively regulating Marvel D3 to ameliorate radiation-induced skin injury.

Dlg1 activates beta-catenin signaling to regulate retinal angiogenesis and the blood-retina and blood-brain barriers.

Beta-catenin (i.e., canonical Wnt) signaling controls CNS angiogenesis and the blood-brain and blood-retina barriers. To explore the role of the Discs large/membrane-associated guanylate kinase (Dlg/MAGUK) family of scaffolding proteins in beta-catenin signaling, we studied vascular endothelial cell (EC)-specific knockout of Dlg1/SAP97. EC-specific loss of Dlg1 produces a retinal vascular phenotype that closely matches the phenotype associated with reduced beta-catenin signaling, synergizes with genetically-directed reductions in beta-catenin signaling components, and can be rescued by stabilizing beta-catenin in ECs. In reporter cells with CRISPR/Cas9-mediated inactivation of Dlg1, transfection of Dlg1 enhances beta-catenin signaling ~4 fold. Surprisingly, Frizzled4, which contains a C-terminal PDZ-binding motif that can bind to Dlg1 PDZ domains, appears to function independently of Dlg1 in vivo. These data expand the repertoire of Dlg/MAGUK family functions to include a role in beta-catenin signaling, and they suggest that proteins other than Frizzled receptors interact with Dlg1 to enhance beta-catenin signaling.

Abstract 3064: Oral cancer stem cells modulate Fusobacterium nucleatum to acquire the capability to induce tumor stemness switch

Abstract Background: Fusobacterium nucleatum is an oral bacteria that contributes to oral carcinogenesis. Its potential role in oral cancer is not known. Fusobacterium nucleatum (henceforth FN) is a gram-negative anaerobe associated with periodontal diseases and also colon cancer. The bacteria modulates the host cell signaling mechanism including the activation of beta-catenin signaling and p38 pathway. The Fap2 is the outer membrane proteins of FN that inhibit lymphocytes and NK cells. The bacteria also directly binds to NKp46 receptor of NK cells. These properties of FN may be exploited by oral CSCs to defend their own niche as a part of niche-defense mechanism against immune system. Hence, it is not surprising that oral CSCs may hijack this specific oral bacterium to enhance tumor stemness. We speculate that oral CSCs may hijack specific bacteria type present in oral mucosa, and enhance their stemness-inducing mechanisms to switch non-CSCs to CSCs. Methods: We have established an in vitro model of oral cancer cells/FN host/pathogen interaction model. Using this model, we wanted to study potential role of the bacteria in cancer stemness. We also used the saliva of subjects with oral cancer to infect oral cancer stem cells and non-stem cancer cells. Results: When the SCC-25 oral cancer cell line was treated with the saliva of subjects with oral cancer, the EpCAM+/ABCG2+ oral CSCs population was increased and showed the presence of FN. The FN recovered from CSCs exhibited high expression of FadA and Fap2, two surface proteins present in FN that can modulate signaling pathways of host cells. Importantly, FN recovered from the infected CSCs induced stemness in the non-stem cancer cell population of SCC-25, suggesting that CSCs may modulate the pathogen. Indeed, our preliminary observation indicates that FN recovered from the FN strain ATCC 25586 infected SCC-25 ABCG2+ cells showed increased expression of FADA and Fap2 as compared to the parental strain ATCC 25586. Conclusion: Our data suggests that CSCs have the capability to reprogram F. nucleatum genome in order to make the bacteria a potent inducer of tumor stemness in non-stem cancer cells. Citation Format: Bidisha Pal, Seema Bhuyan, Debabrat Baishya, Bikul Das. Oral cancer stem cells modulate Fusobacterium nucleatum to acquire the capability to induce tumor stemness switch [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3064.

Abstract SY19-01: Tumor-elicited inflammation in colorectal cancer

Abstract The majority of sporadic human colorectal cancer is initiated by genetic loss or inactivation of tumor suppressor APC (Absent in Polyposis Coli). In addition to activation of beta-catenin signaling, we found that loss of APC results in upregulation of IL-6 signal transducer (IL6/gp130), thereby leading to activation of STAT3 and YAP, two transcription factors that make important contributions to colorectal tumorigenesis. In addition, APC loss results in deterioration of the intestinal epithelial barrier and immune homeostasis, barrier loss due to downregulation of genes encoding tight junction proteins, and suppression of mucin production. Together, such changes promote the invasion of inflammation-inducing colitogenic bacteria and their products. Loss of immune homeostasis is due to defective luminal transport of IgA dimers caused by loss of polyimmunoglobin receptor (PIgR) and CCL28, a chemokine responsible for recruitment of IgA-producing plasma cells. Defective luminal transport of IgA results in dysbiosis and over-representation of inflammation-causing bacteria that can accelerate colorectal tumor genesis through upregulation of IL-17 production. Citation Format: Michael Karin. Tumor-elicited inflammation in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr SY19-01. doi:10.1158/1538-7445.AM2017-SY19-01

Genetic basis of calcifying cystic odontogenic tumors.

Calcifying cystic odontogenic tumors (CCOTs) are benign cystic tumors that form abnormally keratinized ghost cells. Mutations in CTNNB1, which encodes beta-catenin, have been implicated in the development of these tumors, but a causal relationship has not been definitively established. Thus, mutational hot spots in 50 cancer genes were examined by targeted next-generation sequencing in 11 samples of CCOT. Mutations in CTNNB1, but not in other genes, were observed in 10 of 11 cases. These mutations constitutively activate beta-catenin signaling by abolishing the phosphorylation sites Asp32, Ser33, or Ser37, and are similar to those reported in pilomatrixoma and adamantinomatous craniopharyngioma. In contrast, BRAF or NRAS mutations were observed in 12 and two control samples of ameloblastoma, respectively. In HEK293 cells, overexpression of mutated CTNNB1 also upregulated hair keratin, a marker of ghost cells. Furthermore, ghost cells were present in two cases of ameloblastoma with BRAF and CTNNB1 mutations, indicating that ghost cells form due to mutations in CTNNB1. The data suggest that mutations in CTNNB1 are the major driver mutations of CCOT, and that CCOT is the genetic analog of pilomatrixoma and adamantinomatous craniopharyngioma in odontogenic tissue.

Abstract 4756: N-cadherin signaling predicts prognosis in medulloblastoma subtypes

Abstract Identification of signaling pathways that drive the clinical behavior of tumors will guide specific molecular therapies. Medulloblastoma, the most common malignant pediatric solid tumor, shows considerable clinical and molecular diversity, providing impetus for specific targeted therapies of predicted molecular drivers. Here we show a gene signature derived from in vitro experimental inhibition of N-cadherin in medulloblastoma (MB) cells predicts survival in human MB in two large independent patient cohorts. Patients with high N-cadherin signature scores had earlier death and reduced overall survival. We found novel heterogeneity in proposed MB molecular subgroups, with significant differences in survival predicted by the N-cadherin signature in sonic hedgehog (SHH) and c2 tumors. In cultured MB cells, N-cadherin cell-cell interactions activated beta-catenin signaling and increased expression of the cancer stem cell regulator Sox2, known to be critical in the growth and relapse of SHH MB. Inhibition of N-cadherin reduced beta-catenin signaling and Sox2. Together, these findings indicate N-cadherin activity predicts the survival of patients with MB and suggest that differential activity of cellular pathways can identify novel disease subgroups and reveal molecular mechanisms with therapeutic significance. Citation Format: Maria Sverdlov, Michael P. Downing, Shuqi Kang, Anjen Chenn. N-cadherin signaling predicts prognosis in medulloblastoma subtypes. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4756.

Wnt3a protein reduces growth factor-driven expansion of human hematopoietic stem and progenitor cells in serum-free cultures.

Ex vivo expansion of hematopoietic stem and progenitor cells (HSPC) is a promising approach to improve insufficient engraftment after umbilical cord blood stem cell transplantation (UCB-SCT). Although culturing HSPC with hematopoietic cytokines results in robust proliferation, it is accompanied with extensive differentiation and loss of self-renewal capacity. Wnt signaling has been implicated in regulating HSPC fate decisions in vivo and in promoting HSPC self-renewal by inhibition of differentiation, but the effects of Wnt on the ex vivo expansion of HSPC are controversial. Here, we demonstrate that exogenous Wnt3a protein suppresses rather than promotes the expansion of UCB-derived CD34+ cells in serum free expansion cultures. The reduced expansion was also observed in cultures initiated with Lin-CD34+CD38lowCD45RA-CD90+ cells which are highly enriched in HSC and was also observed in response to activation of beta-catenin signaling by GSK3 inhibition. The presence of Wnt3a protein during the culture reduced the frequency of multilineage CFU-GEMM and the long-term repopulation ability of the expanded HSPC. These data suggest that Wnt signaling reduces expansion of human HSPC in growth factor-driven expansion cultures by promoting differentiation of HSPC.

Transducin (β)-like 1 X-linked receptor 1 promotes proliferation and tumorigenicity in human breast cancer via activation of beta-catenin signaling.

IntroductionTransducin (β)-like 1 X-linked receptor 1(TBLR1) is an F-box-like and WD repeat-containing protein which functions as a switch in transcriptional activation, However, the clinical significance and biological role of TBLR1 in breast cancer remains largely unknown.MethodsWestern blotting, immunocytochemistry and real-time PCR were used to evaluate TBLR1 expression in normal breast epithelial cells and breast cancer cell lines, clinical tissue samples and adjacent nontumor tissues, and in 214 paraffin-embedded specimens. Statistical analyses were used to test for the prognostic and diagnostic associations. The biological role of TBLR1 -induced proliferation and tumorigenicity in breast cancer cells was explored in vitro and in vivo. The effect of TBLR1 on the expression of cyclin D1 and β-catenin signaling was examined by Western blotting, luciferase reporter assay and by several immunoprecipitation techniques.ResultsTBLR1 was significantly upregulated in breast cancer cells and tissues compared to normal control samples. Immunohistochemical analysis revealed high expression of TBLR1 in 113 of 214 (52.8%) paraffin-embedded archival breast cancer. The overall expression level of TBLR1 was significantly correlated with clinical stage (P <0.001), the tumor classification (P <0.001), node classification (P =0.024), and metastasis classification (P = 0.004), histological grade (P = 0.044), as well as with the expression level of c-erbB2 (P = 0.036) and Ki-67 (P <0.001). Patients with higher TBLR1 expression had shorter overall survival time, whereas patients with lower TBLR1 expression had better survival. Multivariate analysis suggested that TBLR1 expression might be an independent prognostic indicator for the survival of breast cancer patients. TBLR1 overexpression promoted, whereas TBLR1 silencing inhibited, proliferation and tumorigenicity in breast cancer cells both in vitro and in vivo. We found that TBLR1 expression was implicated in the upregulation of cyclin D1, phosphorylation of cell-cycle control protein Rb (pRb) and activation of β-catenin signaling in breast cancer.ConclusionsTBLR1 plays a key role in the development and progression of breast cancer cells via cyclin D1-transactivation and activation of the β-catenin signaling pathway. TBLR1 may be a novel prognostic marker and a potential therapeutic target in the treatment human breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-014-0465-z) contains supplementary material, which is available to authorized users.

Enteral Nutrition in the Management of Pediatric Intestinal Failure

Intestinal failure is an uncommon but devastating condition whose natural history has dramatically improved over the past two decades (1). Infants with intestinal failure due to severe short bowel syndrome or other diagnoses previously considered incompatible with life are now routinely being saved and cared for in cutting edge, multidisciplinary programs. Enteral nutrition plays a central role in the management of children with intestinal failure. This review provides an overview of enteral nutrition in pediatric intestinal failure, with specific emphasis on recent advances in clinical management, patient outcomes, and emerging therapies.

Periostin activates beta-catenin signaling and prevents cortical porosity induced by intermittent PTH in mice

Periostin activates beta-catenin signaling and prevents cortical porosity induced by intermittent PTH in mice

Abstract 409: Bacterial protein AvrA targets intestinal stem cells via beta-catenin pathway and enhances intestinal tumorigenesis

Abstract Bacterial infection contributes to tumorigenesis and the progression of established cancerous lesions. However, how enteric bacterial products directly contribute to cancer is still unknown. Salmonella infection is a common public health problem that can become chronic and increase the risk of cancer. Moreover, alive and mutated Salmonella is used as a vector to target cancer cells. However, studies are lacking on chronic infection with mutated Salmonella in the host. Salmonella AvrA is a multifunctional protein that influences eukaryotic cell pathways utilizing ubiquitin and acetylation. AvrA protein acts as a deubiquintinase to regulate beta-catenin ubiquitination and stabilize beta-catenin, a key player in intestinal development and tumorigenesis. We hypothesize that the bacterial effector AvrA activates the beta-catenin pathway to promote colonic tumorigenesis. In a colitis-associated colon cancer model, mice were infected with Salmonella AvrA- sufficient or deficient bacterial strains, then stimulated with a carcinogen azoxymethane (AOM) and dextran sodium sulfate (DSS, induced colitis). We investigated consequences of the bacterial AvrA-mucosal interactions in tumorigenesis. The tumor incidence in the AvrA+ infected group is 100% compared to 51.4% in the AOM/DSS only group and 56.3% in the AvrA- infected mice. Mice infected with AvrA-expressed bacteria had significant high incidence of tumor. In contrast, chronic infection of Salmonella AvrA-/- mutation strain was not sufficient to increase the tumor incidence. The AOM/DSS mice had most of the tumors close to the distal colon. In contrast, the location of tumors in the infected mice was moved closer to proximal colon, where has more bacterial growth. We further determined the mechanisms by which bacterial AvrA directly activates beta-catenin signaling by enhancing nuclear beta-catenin in the infected colon cancer models. AvrA expression increased the expression of phosphorylated-beta-catenin (ser552), indicating involvement in inflammation-induced stem-progenitor cell expansion. We confirmed the colonization of Salmonella in the intestine by immunostaining, real-time PCR, and bacterial culture. Salmonella was identified not only at the top of the villus, but also at the basal side, stem cell niches of the intestinal epithelium. Inflammatory cytokines, such as IL-6, were increased by infection and promotes epithelial cancer. Overall, we demonstrated bacterial AvrA activation of the beta-catenin pathway in colonic tumorigenesis. Our findings provide important insights into how a bacterial effector protein contributes to the development of colon cancer. This study also allows for a better understanding of intestinal stem cells targeted by a bacterial protein. It will bring us one step closer to understanding the therapeutic strategies that may hamper dysregulation of stem cells in infection and cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 409. doi:1538-7445.AM2012-409

Beta-Catenin Phosphorylated at Threonine 120 Antagonizes Generation of Active Beta-Catenin by Spatial Localization in trans-Golgi Network

The stability and subcellular localization of beta-catenin, a protein that plays a major role in cell adhesion and proliferation, is tightly regulated by multiple signaling pathways. While aberrant activation of beta-catenin signaling has been implicated in cancers, the biochemical identity of transcriptionally active beta-catenin (ABC), commonly known as unphosphorylated serine 37 (S37) and threonine 41 (T41) β-catenin, remains elusive. Our current study demonstrates that ABC transcriptional activity is influenced by phosphorylation of T120 by Protein Kinase D1 (PKD1). Whereas the nuclear β-catenin from PKD1-low prostate cancer cell line C4-2 is unphosphorylated S37/T41/T120 with high transcription activity, the nuclear β-catenin from PKD1-overexpressing C4-2 cells is highly phosphorylated at T120, S37 and T41 with low transcription activity, implying that accumulation of nuclear β-catenin alone cannot be simply used as a read-out for Wnt activation. In human normal prostate tissue, the phosphorylated T120 β-catenin is mainly localized to the trans-Golgi network (TGN, 22/30, 73%), and this pattern is significantly altered in prostate cancer (14/197, 7.1%), which is consistent with known down regulation of PKD1 in prostate cancer. These in vitro and in vivo data unveil a previously unrecognized post-translational modification of ABC through T120 phosphorylation by PKD1, which alters subcellular localization and transcriptional activity of β-catenin. Our results support the view that β-catenin signaling activity is regulated by spatial compartmentation and post-translational modifications and protein level of β-catenin alone is insufficient to count signaling activity.

Interactions of Wnt/ -Catenin Signaling and Sonic Hedgehog Regulate the Neurogenesis of Ventral Midbrain Dopamine Neurons

Signaling mechanisms involving Wnt/beta-catenin and sonic hedgehog (Shh) are known to regulate the development of ventral midbrain (vMB) dopamine neurons. However, the interactions between these two mechanisms and how such interactions can be targeted to promote a maximal production of dopamine neurons are not fully understood. Here we show that conditional mouse mutants with region-specific activation of beta-catenin signaling in vMB using the Shh-Cre mice show a marked expansion of Sox2-, Ngn2-, and Otx2-positive progenitors but perturbs their cell cycle exit and reduces the generation of dopamine neurons. Furthermore, activation of beta-catenin in vMB also results in a progressive loss of Shh expression and Shh target genes. Such antagonistic effects between the activation of Wnt/beta-catenin and Shh can be recapitulated in vMB progenitors and in mouse embryonic stem cell cultures. Notwithstanding these antagonistic interactions, cell-type-specific activation of beta-catenin in the midline progenitors using the tyrosine hydroxylase-internal ribosomal entry site-Cre (Th-IRES-Cre) mice leads to increased dopaminergic neurogenesis. Together, these results indicate the presence of a delicate balance between Wnt/beta-catenin and Shh signaling mechanisms in the progression from progenitors to dopamine neurons. Persistent activation of beta-catenin in early progenitors perturbs their cell cycle progression and antagonizes Shh expression, whereas activation of beta-catenin in midline progenitors promotes the generation of dopamine neurons.

Wnt signaling may be activated in a subset of Peutz-Jeghers syndrome polyps closely correlating to LKB1 expression

The premalignant potential of Peutz-Jeghers syndrome (PJS) hamartomas has not been established. The major gene responsible for PJS is LKB1. LKB1 has a complex cellular role, therefore, the exact role of LKB1 in Peutz-Jeghers syndrome hamartomas (PJSs) is particularly difficult to understand. It has recently been found that LKB1 functions in the Wnt pathway in Xenopus during early development. Aberrant beta-catenin expression, the key regulator of the activated Wnt/beta-catenin signaling pathway, appears to stimulate interferon-induced gene 1 (IFITM1) products in intestinal tumorigenesis. Both contribute to intestinal tumor formation and tumor progression. This study was designed to investigate expression of LKB1, beta-catenin and IFITM1 in PJSs, colorectal adenomas (CRAs), colorectal carcinomas (CRCs) and normal colorectal mucosas (NCs) using RT-PCR and immunohistochemistry. Immunofluorescence was used to assess the co-expression characteristics of beta-catenin and IFITM1. Results showed that the expression profiles of LKB1, beta-catenin and IFITM1 in PJSs were similar to those in CRAs both at the mRNA and protein levels. The cytoplasmic level of beta-catenin expression correlated strongly with LKB1 and IFITM1 expression in the tumor cells. The dyregulation of beta-catenin was found in a majority (16/20) of the PJS polyps. Immunofluorescence also revealed co-expression of beta-catenin and IFITM1 in the cytoplasm of the PJSs. These findings suggest that Wnt signaling may be activated in a subset of PJSs, and activation of the Wnt/beta-catenin signaling in PJS polyps may be caused by LKB1 expression. The activated beta-catenin signaling pathway including IFITM1 might play an important role in a subset of PJS polyps.

β‐catenin, cartilage, and osteoarthritis

The early cellular events during the development of osteoarthritis (OA) are accelerated articular chondrocyte maturation and extracellular matrix degradation, which are usually seen in the weight-bearing region of articular cartilage. The results of our recent studies from transgenic OA mouse models indicate that upregulation of beta-catenin signaling in articular chondrocytes is most likely responsible for the conversion of normal articular chondrocytes into maturing (arthritic) chondrocytes, which is associated with activation of chondrocyte maturational genes and matrix degradation. Conditional activation of the beta-catenin gene in articular chondrocytes leads to an OA-like phenotype. Overexpression of Smurf2, an E3 ubiquitin ligase, also induces an OA-like phenotype through upregulation of beta-catenin signaling. In addition, beta-catenin upregulation was also found in articular cartilage tissues in patients with OA. These findings indicate that beta-catenin plays a central role in articular cartilage function and that activation of beta-catenin signaling may represent a pathologic mechanism for OA development.

CK1ε Is Required for Breast Cancers Dependent on β-Catenin Activity

BackgroundAberrant β-catenin signaling plays a key role in several cancer types, notably colon, liver and breast cancer. However approaches to modulate β-catenin activity for therapeutic purposes have proven elusive to date.MethodologyTo uncover genetic dependencies in breast cancer cells that harbor active β-catenin signaling, we performed RNAi-based loss-of-function screens in breast cancer cell lines in which we had characterized β-catenin activity. Here we identify CSNK1E, the gene encoding casein kinase 1 epsilon (CK1ε) as required specifically for the proliferation of breast cancer cells with activated β-catenin and confirm its role as a positive regulator of β-catenin-driven transcription. Furthermore, we demonstrate that breast cancer cells that harbor activated β-catenin activity exhibit enhanced sensitivity to pharmacological blockade of Wnt/β-catenin signaling. We also find that expression of CK1ε is able to promote oncogenic transformation of human cells in a β-catenin-dependent manner.Conclusions/SignificanceThese studies identify CK1ε as a critical contributor to activated β-catenin signaling in cancer and suggest it may provide a potential therapeutic target for cancers that harbor active β-catenin. More generally, these observations delineate an approach that can be used to identify druggable synthetic lethal interactions with signaling pathways that are frequently activated in cancer but are difficult to target with the currently available small molecule inhibitors.

Smad3 Prevents β-Catenin Degradation and Facilitates β-Catenin Nuclear Translocation in Chondrocytes

Our previous study demonstrated that transforming growth factor (TGF)-beta activates beta-catenin signaling through Smad3 interaction with beta-catenin in chondrocytes. In the present studies, we further investigated the detailed molecular mechanism of the cross-talk between TGF-beta/Smad3 and Wnt/beta-catenin signaling pathways. We found that C-terminal Smad3 interacted with both the N-terminal region and the middle region of beta-catenin protein in a TGF-beta-dependent manner. Both Smad3 and Smad4 were required for the interaction with beta-catenin and protected beta-catenin from an ubiquitin-proteasome-dependent degradation. In addition, the formation of the Smad3-Smad4-beta-catenin protein complex also mediated beta-catenin nuclear translocation. This Smad3-mediated regulatory mechanism of beta-catenin protein stability enhanced the activity of beta-catenin to activate downstream target genes during chondrogenesis. Our findings demonstrate a novel mechanism between TGF-beta and Wnt/beta-catenin signaling pathways during chondrocyte development.

Nuclear β-Catenin Induces an Early Liver Progenitor Phenotype in Hepatocellular Carcinoma and Promotes Tumor Recurrence

Transforming growth factor-beta cooperates with oncogenic Ras to activate nuclear beta-catenin during the epithelial to mesenchymal transition of hepatocytes, a process relevant in the progression of hepatocellular carcinoma (HCC). In this study we investigated the role of beta-catenin in the differentiation of murine, oncogene-targeted hepatocytes and in 133 human HCC patients scheduled for orthotopic liver transplantation. Transforming growth factor-beta caused dissociation of plasma membrane E-cadherin/beta-catenin complexes and accumulation of nuclear beta-catenin in Ras-transformed, but otherwise normal hepatocytes in p19(ARF)-/- mice. Both processes were inhibited by Smad7-mediated disruption of transforming growth factor-beta signaling. Overexpression of constitutively active beta-catenin resulted in high levels of CK19 and M2-PK, whereas ablation of beta-catenin by axin overexpression caused strong expression of CK8 and CK18. Therefore, nuclear beta-catenin resulted in dedifferentiation of neoplastic hepatocytes to immature progenitor cells, whereas loss of nuclear beta-catenin led to a differentiated HCC phenotype. Poorly differentiated human HCC showed cytoplasmic redistribution or even loss of E-cadherin, suggesting epithelial to mesenchymal transition. Analysis of 133 HCC patient samples revealed that 58.6% of human HCC exhibited strong nuclear beta-catenin accumulation, which correlated with clinical features such as vascular invasion and recurrence of disease after orthotopic liver transplantation. These data suggest that activation of beta-catenin signaling causes dedifferentiation to malignant, immature hepatocyte progenitors and facilitates recurrence of human HCC after orthotopic liver transplantation.