Phosphorylation Of Beta-catenin Research Articles

Interactome Profile of Visceral Adipose Tissue in Obesity Links Key Genes to Cancer Pathogenesis

Obesity increases the risk of the development of several malignancies. The visceral adipose tissue (VAT) depot is one of the pivotal contributors behind the obesity-related pathogenetic mechanisms. In this study, we analyzed the differential gene expression profile in the VAT of obese children using two Gene Expression Omnibus datasets. GSE29718 and GSE9624 were sorted and 68 common differentially expressed genes (DEG) with fold change 1.5 upregulation or downregulation (cutoff |logFC|≥0.58496) were obtained. Gene ontology and functional enrichment and protein-protein interaction (PPI) network for the DEG were analyzed in Search Tool for the Retrieval of Interacting Genes (STRING), which revealed 37 biological processes, 3 cellular components, and 1 molecular function to be significantly associated. Reactome pathway analysis showed the DEG to be involved in- one carbon pool by folate, glycine degradation, transcriptional regulation by TP53, ERK inactivation, G1/S-specific transcription, Fanconi anemia pathway, beta-catenin phosphorylation cascade, RAF activation, and negative regulation of the MAPK pathway. The PPI network was set with a minimum interaction score of 0.400 and a maximum of 10 interactions, and it was significantly enriched (p-value 0.047) with 66 nodes and 46 edges. Target prediction was performed using miRNet. Several miRNA, including hsa-miR-1-3p, hsa-let-7b-5p, hsa-miR-16-5p, hsa-miR-27a-3p and hsa-miR-34a-5p were part of the mRNA-miRNA interaction network. Using the CytoHubba plugin in Cytoscape, the top 10 hub genes from the PPI network were discovered. Thymidine phosphorylase (TYMP) and dihydrofolate reductase (DHFR), essential components of nucleic acid metabolism, have been shown to be involved in angiogenesis and endothelial cell growth, and correlated to p53 mutations, respectively. Protein phosphatase 2, regulatory subunit A & regulatory subunit B (PPP2R1A and PPP2R1B) mutations are involved in ovarian, endometrial, lung and colorectal cancers. HLA-DQA1 mutation is involved cervical cancer, and it is involved in increased immune sensitivity and liver damage in breast cancer patients. The RAB7Ab and RAB7-interacting lysosomal protein (RILP) are regulators of endo-lysosomal trafficking and suppresses breast cancer cell invasion. To conclude, this study identifies several genes and their regulatory pathways in VAT which may contribute to the increased risk of cancer pathogenesis in obese individuals.

Regulation of complexed and free catenin pools by distinct mechanisms. Differential effects of Wnt-1 and v-Src.

Cadherins are transmembrane receptors with an extracellular domain that participates in homophilic cell to cell adhesion and a cytoplasmic domain that associates with proteins called catenins. Cadherin-mediated adhesion as well as adhesion-independent functions for catenins play important roles in differentiation, development, and malignant transformation. Mechanisms that regulate steady-state catenin levels and cadherin-catenin complex stability are poorly understood, but activities of both the Wnt-1 proto-oncogene and tyrosine kinases are implicated. Here I define, at the biochemical level, distinct mechanisms that modulate steady-state catenin levels. Increased cadherin expression, providing more catenin binding sites, leads to selective stabilization of the cadherin-associated population of alpha- and beta-catenin, but not p120(cas). In contrast, expression of Wnt-1 leads primarily to increased stability of the uncomplexed pool of beta-catenin without effect on p120(cas). Significantly, the Wnt-1-induced stabilization of uncomplexed beta-catenin is independent of cadherin expression. Transformation by v-Src does not disrupt the catenin-cadherin complex despite the phosphorylation of E-cadherin and beta-catenin on tyrosine. In contrast to the effects of Wnt-1, v-Src does not modulate the uncomplexed population of beta-catenin. p120(cas) is phosphorylated on tyrosine by v-Src, and this is accompanied by a significant decrease in the level of uncomplexed p120(cas) as well as a change in behavior of p120(cas) upon biochemical fractionation. Taken together these data suggest that p120(cas) and beta-catenin are regulated independently.

Arginine, Agmatine, and Polyamines: Key Regulators of Conceptus Development in Mammals.

Arginine is a key amino acid in pregnant females as it is the precursor for nitric oxide (NO) via nitric oxide synthase and forpolyamines (putrescine, spermidine, and spermine) by either arginase II and ornithine decarboxylase to putrescine or via arginine decarboxylase to agmatine and agmatine to putrescine via agmatinase. Polyamines are critical for placental growth and vascularization. Polyamines stabilize DNA and mRNA for gene transcription and mRNA translation, stimulate proliferation of trophectoderm, and formation of multinucleated trophectoderm cells that give rise to giant cells in the placentae of species such as mice. Polyamines activate MTOR cell signaling to stimulate protein synthesis and they are important for motility through modification of beta-catenin phosphorylation, integrin signaling via focal adhesion kinases, cytoskeletal organization, and invasiveness or superficial implantation of blastocysts. Physiological levels of arginine, agmatine, and polyamines are critical to the secretion of interferon tau for pregnancy recognition in ruminants. Arginine, polyamines, and agmatine are very abundant in fetal fluids, fetal blood, and tissues of the conceptus during gestation. The polyamines are thus available to influence a multitude of events including activation of development of blastocysts, implantation, placentation, fetal growth, and development required for the successful establishment and maintenance of pregnancy in mammals.

Abstract P3-06-08: Pak1 as a novel mediator of resistance to endocrine therapy and CDK4/6 inhibitors in ER+/PAK-1amplified breast cancer

Abstract Background: CDK4/6 inhibitors have been approved in combination with endocrine therapy for the treatment of estrogen receptor positive (ER+) metastatic breast cancer. The goal of this study was to discover mechanisms of resistance to ER antagonists alone and in combination with CDK4/6 inhibitors. Results: p21-activated kinase 1 (PAK1) is a serine/threonine kinase amplified in several human cancer types. Specifically, the survey of TCGA for copy number alterations and/or expression showed PAK1 amplification and/or overexpression in ~23% of ER+ breast cancer. To test the hypothesis that PAK1-amplification is related to CDK4/6 inhibitors resistance, we generated two ER+ breast cancer cell lines T47D (harbouring PAK1 amplification) and MCF7 (non PAK1-amplified) resistant to the combination of fulvestrant (ER downregulator) and abemaciclib (CDK4/6 inhibitor), namely T47DFAR and MCF7FAR. T47DFAR and MCF7FAR were obtained, exposing the parental cells to increasing doses of drugs. Interestingly, only the T47DFAR but not the MCF7FAR showed higher level of PAK1 expression and activation compared to the parental cell line. PAK1 pathway activation was evaluated measuring by immunoblot the levels of phosphorylation of PAK1, MEK, ERK and Beta-Catenin. Moreover, the genomic knockdown of PAK1 through RNAi causes a decrease in cell proliferation of T47DFAR, but not of MCF7FAR and parental cells, suggesting the role of PAK1 as a possible mediator of drug resistance. Conversely, overexpression of PAK1 in MCF7 and T47D parental cells was able to generate resistance to the drug combination. PAK-1 has shown to have a different role in the cytosol as pathways mediator and in the nucleus as transcriptional factor. Our data obtained by subcellular fractionation showed that after treatment with fulvestrant-abemaciclib, PAK1 protein accumulates into the cytosol in T47D-FAR compared to parental T47D, probably mediating an enhancement in cytoplasmatic cell signalling and pathway activation. To univocally demonstrate that PAK1 mediates tumor resistance to fulvestrant-abemaciclib combination, we are generating data from RNA-Seq and whole exome sequencing from T47DFAR and MCF7FAR and the relative parental cell lines. Also, we will assess the efficacy of PAK pharmacological inhibition in overcoming such resistance. Conclusions: In conclusion, our data suggest the role of PAK1 as a novel therapeutic target in ER+/PAK1-amplified breast cancer model resistant to endocrine therapy and CDK4/6 inhibitors. Citation Format: Stefania Belli, Alberto Servetto, Concetta Di Mauro, Daniela Esposito, Ada Pesapane, Fabiana Napolitano, Antonio Santaniello, Pietro De Placido, Priscilla Cascetta, Annachiara Carratù, Eleonora Mozzillo, Roberta Marciano, Roberto Bianco, Luigi Formisano. Pak1 as a novel mediator of resistance to endocrine therapy and CDK4/6 inhibitors in ER+/PAK-1amplified breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-06-08.

Comparison of serum levels with bone content and gene expression indicate a contradictory effect of kidney transplantation on sclerostin

In an attempt to clarify the mechanisms of post-transplant bone disease we investigated the bone content and gene expression of several bone-related proteins. After a successful kidney transplant, the content of sclerostin in bone biopsies was found to be increased as measured by immunohistochemistry, multiplex assay, and gene expression despite a concomitant decrease of sclerostin in the serum. The phosphorylation of beta-catenin was increased, confirming Wnt pathway inhibition, an effect accompanied by an increase of the receptor activator of nuclear factor kappa-Β ligand (RANKL) and a decrease of osteoprotegerin protein levels in both serum and bone. Thus, changes in circulating biomarkers after kidney transplantation cannot be easily extrapolated to concomitant changes occurring in the bone. Hence, overall treatment decisions post kidney transplant should not be based on serum biochemistry alone.

Beta catenin is regulated by its subcellular distribution and mutant huntingtin status in Huntington's disease cell STHdhQ111/HdhQ111

Dysregulation of gene expression at RNA and protein level is a hallmark of Huntington's disease (HD). Altered levels of microRNAs and beta catenin in HD were studied earlier; however, any direct involvement of full length, basally-expressing mutant huntingtin (Htt) remained to be elusive. Here we reported that the gain-of-function mutation of full-length basally-expressing Htt in HD cell Q111 (STHdhQ111/HdhQ111) upregulated microRNA-214 and decreased beta catenin & its transcriptional activity in an aggregate-independent manner. The result was quite opposite of the function of aggregate-forming mutant Htt fragment 83Q-DsRed. Here, we also reported an elevated level of beta catenin phosphorylation in Q111 cell compared to Q7 cell (SThdhQ7/HdhQ7). We showed that in Q111 cell (compared to Q7), beta catenin was more localized in the cytosol than that of the plasma membrane. This is significant as Gsk3beta phosphorylates beta catenin in the cytosol. Hence, for the first time, our study identified beta catenin localization and mutant Htt status as two key factors of beta catenin regulation in HD.

Abstract 5498: Autoregulation of protein kinase D1 (PRKD1) expression in prostate cancer

Abstract Protein kinase D1 (PRKD1) is down regulated in gastric, breast and prostate cancer. Several regulatory mechanisms modulate PRKD1 activity in cancers. In colon cancer, it has been shown that PRKD1 is down regulated by nuclear beta-catenin. We explored whether beta-catenin is involved in regulation of PRKD1 expression in prostate cancer as well. A CHIP assay performed using prostate cancer LNCaP cell lysate and pull down with beta -catenin antibody, which demonstrated recruitment of beta -catenin to promoter of PRKD1 gene as well as at downstream regions in the gene suggesting that beta -catenin could be involved in PRKD1 regulation. To identify the exact binding site of beta-catenin to PRKD1 gene, we carried out CHIP sequencing. The beta -catenin protein complex was bound to a 166 bp sequence near exon 2 (chr14:29899631-29899796). Because beta -catenin is a coactivator and not a known transcription factor, we performed a transcription factor promoter array, which showed that the MYC/MAX transcription factor complex may be the mediator of the regulatory effect of beta -catenin on PRKD1 expression. We validated the results by performing CHIP assay using MYC and MAX antibodies which showed recruitment of both MYC and MAX to the same beta -catenin binding site to PRKD1. In order to assess the functional impact of beta -catenin regulation of PRKD1 in prostate cancer, beta-catenin mutated at threonine 120 residue (we have previously shown that PRKD1 is the only known kinase to phosphorylate the site) demonstrated increased nuclear translocation of beta-catenin and increase down regulation of PRKD1 and increased androgen receptor (AR) activity (increased AR activity is well established to be associated with PC progression). Our data has identified a novel auto-regulatory mechanism of PRKD1 expression through beta-catenin phosphorylation. Citation Format: Bita Nickkholgh, Sittadjody Sivanandane. Autoregulation of protein kinase D1 (PRKD1) expression in prostate 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 5498. doi:10.1158/1538-7445.AM2017-5498

CBP/Catenin antagonists: Targeting LSCs' Achilles heel.

Cancer stem cells (CSCs), including leukemia stem cells (LSCs), exhibit self-renewal capacity and differentiation potential and have the capacity to maintain or renew and propagate a tumor/leukemia. The initial isolation of CSCs/LSCs was in adult myelogenous leukemia, although more recently, the existence of CSCs in a wide variety of other cancers has been reported. CSCs, in general, and LSCs, specifically with respect to this review, are responsible for initiation of disease, therapeutic resistance and ultimately disease relapse. One key focus in cancer research over the past decade has been the development of therapies that safely eliminate the LSC/CSC population. One major obstacle to this goal is the identification of key mechanisms that distinguish LSCs from normal endogenous hematopoietic stem cells. An additional daunting feature that has recently come to light with advances in next-generation sequencing and single-cell sequencing is the heterogeneity within leukemias/tumors, with multiple combinations of mutations, gain and loss of function of genes, and so on being capable of driving disease, even within the CSC/LSC population. The focus of this review/perspective is on our work in identifying and validating, in both chronic myelogenous leukemia and acute lymphoblastic leukemia, a safe and efficacious mechanism to target an evolutionarily conserved signaling nexus, which constitutes a common "Achilles heel" for LSCs/CSCs, using small molecule-specific CBP/catenin antagonists.

Proteomic Analysis Reveals a New Benefit of Periodic Mechanical Stress on Chondrocytes

Background/Aims: In recent years, a variety of studies have been performed to investigate the cellular responses of periodic mechanical stress. In our previous studies, we found that periodic mechanical stress can promote proliferation and matrix synthesis through the integrin beta 1-mediated ERK1/2 pathway, and we used proteomic analysis to detect quantitative changes in chondrocytes under periodic mechanical stress. Despite these results, the effects and mechanisms of periodic mechanical stress are still not fully understood, so in this study we extended our study using phosphoproteomic techniques. Methods: We used phosphoproteomic techniques to detect phosphorylation changes in chondrocytes under periodic mechanical stress and combined the results with the quantitative proteomic data to further explore the underlying mechanisms. Data were obtained by phosphorylation inhibition, quantitative real-time PCR (qPCR) analysis, western blot analysis and immunofluorescence assay. Results: From phosphoproteomic analysis, a total of 1073 phosphorylated proteins and 2054 phosphopeptides were identified. The number of significant differentially expressed proteins and phosphopeptides was 97 and 108, respectively (ratio >1.20 or <0.83 at p<0.05). Periodic mechanical stress increased glycogen synthase kinase 3-beta (GSK3-beta) phosphorylation at Y216, promoted the phosphorylation of beta-catenin, decreased beta-catenin levels and suppressed the expression of type I collagen. In contrast, inhibition of GSK3-beta by TWS119, which specifically inhibits the phosphorylation of Y216, suppressed the phosphorylation of beta-catenin, which resulted in the accumulation of beta-catenin and an increase in the expression of type I collagen. Conclusions: We successfully constructed differentially expressed phosphoproteomic profiles of rat chondrocytes under periodic mechanical stress, and discovered a potential new therapeutic benefit in which periodic mechanical stress suppressed the formation of type I collagen in the matrix of chondrocytes via phosphorylation of GSK3-beta and beta-catenin.

Abstract 3664: RARRES2 functions as a direct tumor suppressor by promoting beta-catenin phosphorylation and degradation independent of CMKLR1 and CMKLR1-mediated antitumor immune response in adrenocortical carcinoma

Abstract Tumor suppressors and the immune system are critical players in tumor suppression. However, little is known about whether a tumor suppressor can function through both immune-dependent and immune-independent mechanisms. RARRES2 is a small secreted protein that is down-regulated in multiple human cancer types such as adrenocortical carcinoma (ACC), hepatocellular carcinoma (HCC) and melanoma. It has been shown that RARRES2 can play an indirect tumor-suppressive role by acting as a chemoattractant to recruit anti-cancer immune cells expressing its receptor CMKLR1 to sites of tumor. In this study, we show that epigenetic CpG hypermethylation of RARRES2 in vivo and in vitro in ACC causes RARRES2 down-regulation. We also found that RARRES2 can function as a direct tumor suppressor and that its tumor suppressive effect does not depend on the recruitment of CMKLR1-expressing immune cells. We show that although exogenous treatment of cultured cells with recombinant human RARRES2 protein did not show any tumor-suppressive effect, transient overexpression of RARRES2 significantly inhibited cellular invasion. Stable overexpression of RARRES2 in ACC cell line NCI-H295R led to significantly reduced cell proliferation, cell invasion, and tumorigenecity in a RARRES2 dose-dependent manner. Using xenografts of stable NCI-H295R cell lines in two immunodeficient mouse models (athymic nude mice and NSG mice), we found that in the absence of functional immune cells, stable RARRES2 overexpression can still significantly suppress tumor growth in vivo. RARRES2 overexpression promoted beta-catenin phosphorylation and degradation, reduced the phosphorylation of p38 MAP kinase and inhibited the secretion of matrix metalloprotease protein 10 (MMP10) from cancer cells in a RARRES2 dose-dependent manner. Taken into account that CMKLR1 expression is barely detectable in all the cell lines tested, our results present the first evidence that RARRES2 can function as a direct tumor suppressor independent of CMKLR1 and CMKLR1-mediated anti-tumor immune response. Citation Format: Yi Liu-Chittenden, Kelli Gaskins, Sophie Wang, Electron Kebebew. RARRES2 functions as a direct tumor suppressor by promoting beta-catenin phosphorylation and degradation independent of CMKLR1 and CMKLR1-mediated antitumor immune response in adrenocortical carcinoma. [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 3664.

Mechanical Induction of the Tumorigenic β-Catenin Pathway by Tumour Growth Pressure in vivo

The tumour microenvironment may contribute to tumorigenesis due to mechanical forces such as fibrotic stiffness or mechanical pressure caused by the expansion of hyper-proliferative cells. Here we explore the contribution of the mechanical pressure exerted by tumour growth onto non-tumorous adjacent epithelium. In the early stage of mouse colon tumour development in the Notch+Apc+/1638N mouse model, we observed mechanistic pressure stress in the non-tumorous epithelial cells caused by hyper-proliferative adjacent crypts overexpressing active Notch, associated with increased Ret and beta-catenin signalling. We thus developed a method that allows the delivery of a defined mechanical pressure in vivo, by subcutaneously inserting a magnet close to the mouse colon. The implanted magnet generated a magnetic force on ultra-magnetic liposomes, stabilized in the mesenchymal cells of the connective tissue surrounding colonic crypts after intravenous injection. The magnetically induced pressure quantitatively mimicked the endogenous early tumour growth stress in the order of 1,200 Pa, without affecting tissue stiffness, as monitored by acoustic strain imaging and shear wave elastography. Exertion of pressure mimicking that of tumour growth led to rapid Ret activation and downstream phosphorylation of beta-catenin on Tyr654, which impairs its interaction with the E-cadherin in adherens junctions, and which was followed by beta-catenin nuclear translocation after 15 days. As a consequence, elevated expression of beta-catenin-target genes was observed at 1 month, together with crypt enlargement accompanying the formation of early tumorous aberrant crypt foci. Mechanical activation of the tumorigenic beta-catenin pathway, conserved from early embryos beta-catenin dependent mechanical induction of patterning-genes expression, suggests unexplored modes of tumour propagation based on mechanical signalling pathways in healthy epithelial cells surrounding the tumour, which may contribute to tumour heterogeneity.Fernandez-Sanchez, Barbier et al, Nature 2015, Jul 2;523(7558):92-5. http://dx.doi.org/10.1038/nature14329. Epub 2015 May 11.

The curry spice curcumin attenuates beta-amyloid-induced toxicity through beta-catenin and PI3K signaling in rat organotypic hippocampal slice culture

Objective: Accumulating evidence indicates that curcumin potently protects against beta-amyloid (Abeta) due to its oxygen free radicals scavenging and anti-inflammatory properties. However, cellular mechanisms that may underlie the neuroprotective effect of curcumin in Abeta-induced toxicity are not fully understood yet. The present study was undertaken to investigate the mechanisms involved in neuroprotective effects of curcumin, particularly involving Wnt/beta-catenin and PI3K pathways.Methods: Organotypic hippocampal slice cultures were treated with curcumin and exposed to Abeta1–42 for 48 hours. Synaptic dysfunction, cell death, ROS formation, neuroinflammation and beta-catenin, Akt, and GSK-3beta phosphorylation were measured to determine the effects of curcumin against Abeta toxicity.Results: Curcumin significantly attenuated Abeta-induced cell death, loss of synaptophysin, and ROS generation. Furthermore, curcumin was able to decrease IL-6 release and increase IL-10 release, and prevented glial activation. The phosphorylation of beta-catenin was avoided and the levels of free beta-catenin were increased by curcumin to promote cell survival upon treatment with Abeta. Curcumin, in the presence of Abeta, activated Akt which in turn phosphorylates GSK-3beta, and resulted in the inhibition of GSK-3beta. The presence of LY294002, an inhibitor of PI3K pathway, blocked the pro-survival effect of curcumin.Discussion: These results reinforce the neuroprotective effects of curcumin on Abeta toxicity and add some evidence that its mechanism may involve beta-catenin and PI3K signaling pathway in organotypic hippocampal slice culture.

Alterations of Axis Inhibition Protein 1 (AXIN1) in Hepatitis B Virus-Related Hepatocellular Carcinoma and Overexpression of AXIN1 Induces Apoptosis in Hepatocellular Cancer Cells

Axis inhibition protein 1 (AXIN1) is a negative regulator of Wnt/beta-catenin signaling via regulating the level of beta-catenin. However, the role of AXIN1 in the tumorigenesis and progression of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) is less clear. PCR sequence analysis, immunohistochemistry, and Western blot were performed on 22 HBV-related HCC samples and corresponding nontumor liver tissues to detect variants in AXIN1 gene and the expression level of AXIN1. Human hepatoma cell lines SNU475 and SNU423 were transfected with pCDNA3.1-AXIN1-myc or AXIN1 G425S-myc mutant. The growth curve and apoptosis rate of cell lines, phosphorylation of beta-catenin, and cell cycle regulatory proteins depending on beta-catenin transcriptional activity were detected. We identified four mutations of AXIN1 in 22 primary HBV-related HCCs and demonstrated a lower expression of AXIN1 in HBV-related HCC tissues than that in paired adjacent nontumor tissues. Overexpression of AXIN1 wild-type but not AXIN1 mutant inhibited the growth of HCC cell lines, accelerated their apoptosis, and negatively regulated beta-catenin-dependent transcriptional activity. Our study revealed that alterations of AXIN1 were involved in HBV-related HCC. Overexpression of AXIN1 but not AXIN1 mutant negatively regulated beta-catenin-dependent transcriptional activity and downregulated the level of cell cycle regulatory proteins, suggesting that AXIN1 may be a potential target for gene therapy of primary HCC.

Abstract 1306: SR48692 inhibits EGF receptor transactivation and proliferation of lung cancer cells.

Abstract Neurotensin (NTS) is an autocrine growth factor for some lung cancer cells (Moody et al., 1985;Life Sci 36:1727). NTS binds with high affinity to the GPCR NTSR1 causing phosphatidyl inositol turnover and proliferation of lung cancer cells; SR48692 is a NTSR1 antagonist (Moody et al., 2001; Peptides 22:109). NTSR1 expression is associated with poor survival of non-small cell lung cancer (NSCLC) patients (Alfano et al., 2010; Clin Cancer Res 16:4401). NSCLC cells express the epidermal growth factor receptor (EGFR) whose tyrosine kinase activity is inhibited by gefitinib. Here the abillity of SR48692 to block EGFR transactivation caused by NTS was investigated. NTS and NTS8-13 but not NTS1-8 addition to NSCLC cell lines NCI-H1299 or A549 cells increased phosphorylation of Tyr1068 of the EGFR after 2 min which was blocked by 10 uM SR48692 or 10 ug/ml gefitinib. The ability of NTS to regulate EGF receptor transactivation was blocked by GM6001 (matrix metalloprotease inhibitor), PP2 (Src inhibitor), N-acetylcysteine (anti-oxidant) and transforming growth factor TGF) α antibody. By ELISA, NTS significantly increased secretion of TGFα from lung cancer cells. NTS but not levocabastine (NTSR2 agonist) increased cytosolic Ca2+ within seconds after addition to NCI-H1299 cells which was antagonized by SR48692. NTS addition to NCI-H1299 cells increased tyrosine phosphorylation of beta-catenin, ERK, FAK, PYK-2 and Src which was antagonized by SR48692. SR48692 inhibited the proliferation of NCI-H1299 and A549 cells which have wild type EGFR. Also, SR48692 potentiated the ability of gefitinib to inhibit growth of NCI-H1299 and A549 cells. These results indicate that SR48692 is a NTSR1 antagonist which increases the potency of gefitinib in lung cancer cells. Citation Format: Terry W. Moody, Robert T. Jensen. SR48692 inhibits EGF receptor transactivation and proliferation of lung cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1306. doi:10.1158/1538-7445.AM2013-1306

Apc deficiency alters pulmonary epithelial cell fate and inhibits Nkx2.1 via triggering TGF-beta signaling

Wnt signaling is critical for cell fate specification and cell differentiation in many organs, but its function in pulmonary neuroendocrine cell (PNEC) differentiation has not been fully addressed. In this study, we examined the role of canonical Wnt signaling by targeting the gene for Adenomatous Polyposis Coli (Apc), which controls Wnt signaling activity via mediating phosphorylation of beta-catenin (Ctnnb). Targeting the Apc gene in lung epithelial progenitors by Nkx2.1-cre stabilized Ctnnb and activated canonical Wnt signaling. Apc deficiency altered lung epithelial cell fate by inhibiting Clara and ciliated cell differentiation and activating Uchl1, a marker of neuroendocrine cells. Similar to PNEC in normal lung, Uchl1positive cells were innervated. In mice with targeted inactivation of Ctnnb by Nkx2.1-cre, PNEC differentiation was not interrupted. These indicate that, after lung primordium formation, Wnt signaling is not essential for PNEC differentiation; however, its over-activation promotes PNEC features. Interestingly, Nkx2.1 was extinguished in Apc deficient epithelial progenitors before activation of Uchl1. Examination of Nkx2.1 null lungs suggested that early deletion of Nkx2.1 inhibits PNEC differentiation, while late repression does not. Nkx2.1 was specifically inhibited in Apc deficient lungs but not in Ctnnb gain-of-function lungs indicating a functional difference between Apc deletion and Ctnnb stabilization, both of which activate Wnt signaling. Further analysis revealed that Apc deficiency led to increased TGF-beta signaling, which inhibited Nkx2.1 in cultured lung endodermal explants. In contrast, TGF-beta activity was not increased in Ctnnb gain-of-function lungs. Therefore, our studies revealed an important mechanism involving Apc and TGF-beta signaling in regulating the key transcriptional factor, Nkx2.1, for lung epithelial progenitor cell fate determination.

Fap1 Controls Beta-Catenin Activity in a Gsk3-Beta Dependent Manner in Chronic Myeloid Leukemia.

Abstract 2404Fap1 (Fas-associated phosphatase 1) interacts with the C-terminus of multiple proteins via a PDZ-type protein-protein interaction domain. Interaction of Fap1 with Fas results in Fas-de-phosphorylation and inhibits Fas-induced apoptosis. In previous studies, we determined that PTPN13, the gene encoding Fap1, is a target gene for the interferon consensus sequence binding protein (referred to as Icsbp or Irf8). Icsbp functions as a leukemia suppressor in chronic myeloid leukemia (CML), and we previously demonstrated Icsbp/Fap1-dependent apoptosis resistance in cells expressing the CML-associated oncoprotein, Bcr-abl. Another known interaction partner for Fap1 is the adenomatous polyposis coli protein (Apc). However, the functional significance of this interaction has not been previously explored. In the current stuides, we investigate whether interaction between Fap1 and Apc impacts the pathogenesis of CML. Apc is involved in assembly of a multi-protein complex that includes Apc, Axin, Gsk3-beta and beta-catenin. Association of these proteins results in serine/threonine phosphorylation (pS/T) of beta-catenin by Gsk3-beta. pS/T beta-catenin is released from the complex and degraded by the proteasome. Previous studies demonstrated that pS/T of beta-catenin, and consequent beta-catenin degradation, is impaired in CML, but the mechanism for this impairment is unknown in most cases. We find that Icsbp-dependent increase in Fap1 results in increased interaction between Fap1 and Apc in Bcr-abl+ myeloid progenitor cells. We also find that increased Fap1/Apc interaction is associated with inactivation (de-phosphorylation) of Gsk3-beta and a decrease in inhibitory pS/T of βcatenin. We find that this results in increased beta-catenin protein and activity. We also find that Fap1 co-immuno-precipitates with Apc, Axin, Gsk3-beta and beta-catenin. This result suggests the possibility that Gsk3-beta is a substrate for Fap1 protein tyrosine phosphatase activity. Consistent with this hypothesis, we find that Fap1 is able to dephosphorylate Gsk3-beta in vitro. We tested the functional significance of this observation in experiments using an activated form of Gsk3-beta that cannot be dephosphorylated at a key residue (Y216D-Gsk3-beta). We find that expression of this Gsk3-beta mutant partly reverses the effect of Bcr-abl and Fap1 on beta-catenin protein stability and activity. Increased beta-catenin activity is a characteristic of leukemia stem cells (LSC) in CML, and increasing beta-catenin activity in the bone marrow is associated with poor prognosis in CML. Therefore, these studies identify a novel pathway that regulates events significant to CML pathogenesis. These studies also identify a role for Apc in the pathogenesis of leukemia, and another mechanism for the leukemia suppressor effect of Icsbp. Disclosures:No relevant conflicts of interest to declare.

Aurora A kinase regulates N-myc activity through phosphorylation of GSK3-beta and beta-catenin

Aurora A kinase regulates N-myc activity through phosphorylation of GSK3-beta and beta-catenin

Indole-3-carbinol Inhibits Prostate Cancer Cell Migration via Degradation of β-Catenin

We determined whether indole-3-carbinol (I3C) could affect DU145 human prostate carcinoma cell migration to prevent the development and progression of prostate cancer. Although previous studies have shown anticancer properties of I3C in various cancer cell lines, it has not been determined how I3C regulates epidermal growth factor (EGF)-induced migration and related signaling pathways. DU145 cells were treated with I3C (100 microM) in the absence or presence of EGF (10 ng/ml). Our results showed that I3C significantly inhibited DU145 cell migration with and without EGF stimulation. It has been reported that the beta-catenin signaling pathway controls androgen receptor (AR)-mediated prostate cancer progression, which plays a key role in the metastasis of prostate cancer. Western blot analysis demonstrated that I3C led to the phosphorylation of beta-catenin and subsequent degradation of beta-catenin in the absence and presence of EGF. In contrast, I3C did not have any effect on the expression of beta-catenin mRNA. From these results, we suggest that I3C inhibits EGF (dependent or independent)-induced DU145 cell migration through beta-catenin degradation.

Wnt5b regulates mesenchymal cell aggregation and chondrocyte differentiation through the planar cell polarity pathway

Although genetic evidence has demonstrated a role for Wnt5b during cartilage and limb development, little is known about the mechanisms underlying Wnt5b-regulated chondrocyte differentiation. We observed that Wnt5b inhibited chondrocyte hypertrophy and expression of type X collagen. In addition, Wnt5b regulated the overall size of chondrogenic cultures, suggesting that Wnt5b regulates other processes involved in cartilage development. We therefore investigated the signaling pathways by which Wnt5b influences differentiation. Wnt5b activated known calcium-dependent signaling pathways and JNK, a component of the planar cell polarity pathway. Since the planar cell polarity pathway regulates process such as cell migration and cell aggregation that are involved in limb development, we assayed for effects of Wnt5b on these processes. We observed a marked increase chondroprogenitor cell migration with Wnt5b expression. This effect was blocked by inhibition of JNK, but not by inhibition of other Wnt5b-responsive factors. Expression of Wnt5b also disrupted the cellular aggregation associated with mesenchymal condensation. Decreased aggregation was associated with reduced cadherin expression as well as increased cadherin receptor turnover. This increase in cadherin receptor turnover was associated with an increase in Src-dependent beta-catenin phosphorylation downstream of Wnt5b. Our data demonstrate that not only does Wnt5b inhibit chondrocyte hypertrophy, but document a novel role for Wnt5b in modulating cellular migration through the JNK-dependent and cell adhesion through an activation of Src and subsequent cadherin receptor turnover.

MK-801 induces schizophrenic behaviors through downregulating Wnt signaling pathways in male mice

Wnt signaling is important in various neuropsychiatric diseases. However, its actions on modulating schizophrenia are largely unknown. Our previous study found that three SNPs in adenomatous polyposis coli (APC), a negative regulator of the Wnt signaling, were associated with schizophrenia, and the mRNA levels of APC in blood leucocytes of patients with schizophrenia were significantly increased. This prompted us to further investigate the effects of Wnt signaling components on the pathogenesis of schizophrenia. In our current study, mouse schizophrenia was induced by i.p. injection of MK-801 for 7days and the brain prefrontal cortex (PFC) and ventral tegmental area (VTA) were isolated to investigate the Wnt signaling pathway. Compared with control, schizophrenic mice had increased inhibitory phosphorylation of glycogen synthase kinase 3beta (GSK-3beta) in PFC and VTA, which is disassociated with augmented beta-catenin phosphorylation. However, APC mRNA and protein in the PFC and VTA isolated from the schizophrenic group were increased and matched with increased beta-catenin phosphorylation. The total dendritic length was significantly increased in both PFC and VTA from MK-801-treated mice compared to control. By using cultured SK-N-SH and PC12 cells with and without transfection of APC siRNA, we found that the APC protein facilitates neurite growth in vitro. Our data suggested that MK-801-induced schizophrenia is associated with attenuated Wnt signaling pathway in the brain, which may be due to augmented APC protein during schizophrenia. APC facilitates neurite growth, potentially contributing to the pathology of schizophrenia.