Non-canonical Wnt Pathway Research Articles

Variation in the Kozak sequence of WNT16 results in an increased translation and is associated with osteoporosis related parameters

The importance of WNT16 in the regulation of bone metabolism was recently confirmed by several genome-wide association studies and by a Wnt16 (Wnt16−/−) knockout mouse model. The aim of this study was thus to replicate and further elucidate the effect of common genetic variation in WNT16 on osteoporosis related parameters. Hereto, we performed a WNT16 candidate gene association study in a population of healthy Caucasian men from the Odense Androgen Study (OAS). Using HapMap, five tagSNPs and one multimarker test were selected for genotyping to cover most of the common genetic variation in and around WNT16 (MAF>5%). This study confirmed previously reported associations for rs3801387 and rs2707466 with bone mineral density (BMD) at several sites. Furthermore, we additionally demonstrated that rs2908007 is strongly associated with BMD at several sites in the young, elderly and complete OAS population. The observed effect of these three associated SNPs on the respective phenotypes is comparable and we can conclude that the presence of the minor allele results in an increase in BMD. Additionally, we performed re-sequencing of WNT16 on two cohorts selected from the young OAS cohort, based on their extreme BMD values. On this basis, rs55710688 was selected for an in vitro translation experiment since it is located in the Kozak sequence of WNT16a. We observed an increased translation efficiency and thus a higher amount of WNT16a for the Kozak sequence that was significantly more prevalent in the high BMD cohort. This observation is in line with the results of the Wnt16−/− mice. Finally, a WNT luciferase reporter assay was performed and showed no activation of the β-catenin dependent pathway by Wnt16. We did detect a dose-dependent inhibitory effect of Wnt16 on WNT1 activation of this canonical WNT pathway. Increased translation of WNT16 can thus lead to an increased inhibitory action of WNT16 on canonical WNT signaling. This statement is in contrast with the known activating effect of canonical WNT signaling on bone formation and suggests a stimulatory effect on bone metabolism via noncanonical WNT signaling. More research is required to not only confirm this hypothesis, but also to further elucidate the role of non-canonical WNT pathways in bone metabolism and the general mechanisms of interplay between the different WNT signaling pathways.

Genome Wide Analysis Reveals Zic3 Interaction with Distal Regulatory Elements of Stage Specific Developmental Genes in Zebrafish

Zic3 regulates early embryonic patterning in vertebrates. Loss of Zic3 function is known to disrupt gastrulation, left-right patterning, and neurogenesis. However, molecular events downstream of this transcription factor are poorly characterized. Here we use the zebrafish as a model to study the developmental role of Zic3 in vivo, by applying a combination of two powerful genomics approaches – ChIP-seq and microarray. Besides confirming direct regulation of previously implicated Zic3 targets of the Nodal and canonical Wnt pathways, analysis of gastrula stage embryos uncovered a number of novel candidate target genes, among which were members of the non-canonical Wnt pathway and the neural pre-pattern genes. A similar analysis in zic3-expressing cells obtained by FACS at segmentation stage revealed a dramatic shift in Zic3 binding site locations and identified an entirely distinct set of target genes associated with later developmental functions such as neural development. We demonstrate cis-regulation of several of these target genes by Zic3 using in vivo enhancer assay. Analysis of Zic3 binding sites revealed a distribution biased towards distal intergenic regions, indicative of a long distance regulatory mechanism; some of these binding sites are highly conserved during evolution and act as functional enhancers. This demonstrated that Zic3 regulation of developmental genes is achieved predominantly through long distance regulatory mechanism and revealed that developmental transitions could be accompanied by dramatic changes in regulatory landscape.

PITX2 and non-canonical Wnt pathway interaction in metastatic prostate cancer

The non-canonical Wnt pathway, a regulator of cellular motility and morphology, is increasingly implicated in cancer metastasis. In a quantitative PCR array analysis of 84 Wnt pathway associated genes, both non-canonical and canonical pathways were activated in primary and metastatic tumors relative to normal prostate. Expression of the Wnt target gene PITX2 in a prostate cancer (PCa) bone metastasis was strikingly elevated over normal prostate (over 2,000-fold) and primary prostate cancer (over 200-fold). The elevation of PITX2 protein was also evident on tissue microarrays, with strong PITX2 immunostaining in PCa skeletal and, to a lesser degree, soft tissue metastases. PITX2 is associated with cell migration during normal tissue morphogenesis. In our studies, overexpression of individual PITX2A/B/C isoforms stimulated PC-3 PCa cell motility, with the PITX2A isoform imparting a specific motility advantage in the presence of non-canonical Wnt5a stimulation. Furthermore, PITX2 specific shRNA inhibited PC-3 cell migration toward bone cell derived chemoattractant. These experimental results support a pivotal role of PITX2A and non-canonical Wnt signaling in enhancement of PCa cell motility, suggest PITX2 involvement in homing of PCa to the skeleton, and are consistent with a role for PITX2 in PCa metastasis to soft and bone tissues. Our findings, which significantly expand previous evidence that PITX2 is associated with risk of PCa biochemical recurrence, indicate that variation in PITX2 expression accompanies and may promote prostate tumor progression and metastasis.

Abstract C11: Molecular mechanism driving BMI1-induced melanoma metastasis

Abstract Malignant melanoma is one of the most aggressive human cancers, with a high potential for lethal metastasis and therapeutic resistance. The epigenetic chromatin regulator Bmi1 acts as a key component of the Polycomb Repressor Complex 1 (PRC1) and is a known oncogene. Various studies shown that BMI1 is highly expressed in many human hematopoietic malignancies and in different solid tumor types including prostate, breast, ovarian, colon, brain and lung cancer. Importantly, high Bmi1 expression is an excellent predictor of both metastatic progression and poor therapeutic response. Bmi1's role in tumor onset has been assessed using germline mutant mice showing that Bmi1 ablation efficiently suppress tumor development. This impaired tumorigenicity correlates with an impairment of the self-renewal and proliferative properties of tumor initiating cells, mainly due to Bmi1's repressive activity on the Ink4a/Arf tumor suppressor locus. Nevertheless, this function does not explain why Bmi1 is frequently upregulated in tumors nor Bmi1's role in tumor progression. To evaluate Bmi1's contribution to melanoma progression, we upregulated Bmi1 in two different melanoma cell lines, a murine metastatic cell line and a poorly metastatic human cell line. We found that Bmi1 overexpression activates or increases invasive behavior of both cell lines, without enhancing their proliferative capacity. This finding allowed us to dissect Bmi1's oncogenic activity at later stages of tumorigenesis, in the absence of Bmi1's deregulation of cell proliferation. Our data show that Bmi1 significantly enhances in vitro cell movement and modulates adhesion. Bmi1 also protects cells from apoptosis induced by different stimuli and increases lung metastasis formation in vivo. To characterize Bmi1-induced changes in gene expression, we have performed comparative deep sequencing of total RNA libraries generated from Bmi1 or GFP overexpressing cells. Gene ontology analysis revealed enrichment in cancer-relevant pathways that seem to be controlled by Bmi1, including cell movement, cell death and survival, tissue development and cell morphology. In particular, Bmi1 expression modulates the gene regulatory programs associated with EMT, TGFβ and the non-canonical Wnt pathways. We have identified a new Bmi1 target gene, poorly characterized, that seems to be responsible for Bmi1-induced melanoma progression. These data determine a causal role for Bmi1 in melanoma cell migration and establishment of distant melanoma metastasis. Citation Format: Roberta Ferretti, Jacqueline A. Lees. Molecular mechanism driving BMI1-induced melanoma metastasis. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C11.

Mutually exclusive signaling signatures define the hepatic and pancreatic progenitor cell lineage divergence

Understanding how distinct cell types arise from multipotent progenitor cells is a major quest in stem cell biology. The liver and pancreas share many aspects of their early development and possibly originate from a common progenitor. However, how liver and pancreas cells diverge from a common endoderm progenitor population and adopt specific fates remains elusive. Using RNA sequencing (RNA-seq), we defined the molecular identity of liver and pancreas progenitors that were isolated from the mouse embryo at two time points, spanning the period when the lineage decision is made. The integration of temporal and spatial gene expression profiles unveiled mutually exclusive signaling signatures in hepatic and pancreatic progenitors. Importantly, we identified the noncanonical Wnt pathway as a potential developmental regulator of this fate decision and capable of inducing the pancreas program in endoderm and liver cells. Our study offers an unprecedented view of gene expression programs in liver and pancreas progenitors and forms the basis for formulating lineage-reprogramming strategies to convert adult hepatic cells into pancreatic cells.

Wnt Signaling through the Ror Receptor in the Nervous System

The receptor tyrosine kinase-like orphan receptor (Ror) proteins are conserved tyrosine kinase receptors that play roles in a variety of cellular processes that pattern tissues and organs during vertebrate and invertebrate development. Ror signaling is required for skeleton and neuronal development and modulates cell migration, cell polarity, and convergent extension. Ror has also been implicated in two human skeletal disorders, brachydactyly type B and Robinow syndrome. Rors are widely expressed during metazoan development including domains in the nervous system. Here, we review recent progress in understanding the roles of the Ror receptors in neuronal migration, axonal pruning, axon guidance, and synaptic plasticity. The processes by which Ror signaling execute these diverse roles are still largely unknown, but they likely converge on cytoskeletal remodeling. In multiple species, Rors have been shown to act as Wnt receptors signaling via novel non-canonical Wnt pathways mediated in some tissues by the adapter protein disheveled and the non-receptor tyrosine kinase Src. Rors can either activate or repress Wnt target expression depending on the cellular context and can also modulate signal transduction by sequestering Wnt ligands away from their signaling receptors. Future challenges include the identification of signaling components of the Ror pathways and bettering our understanding of the roles of these pleiotropic receptors in patterning the nervous system.

The roles of canonical and non-canonical Wnt signaling in human de-differentiated articular chondrocytes

Osteoarthritis is the most prevalent form of arthritis in the world and it is becoming a major public health problem. Osteoarthritic chondrocytes undergo morphological and biochemical changes that lead to de-differentiation. The involvement of signaling pathways, such as the Wnt pathway, during cartilage pathology has been reported. Wnt signaling regulates critical biological processes. Wnt signals are transduced through at least three intracellular signaling pathways including the canonical Wnt/β-catenin pathway, the Wnt/Ca2 + pathway and the Wnt/planar cell polarity pathway. We investigated the involvement of the Wnt canonical and non-canonical pathways in human articular chondrocyte de-differentiation in vitro. Human articular chondrocytes were cultured through four passages with no treatment, or with sFRP3 treatment, an inhibitor of Wnt pathways, or with DKK1 treatment, an inhibitor of the canonical pathway. Chondrocyte-secreted markers and Wnt pathway components were analyzed using western blotting and qPCR. Inhibition of the Wnt pathway showed that the canonical Wnt signaling probably is responsible for inhibition of collagen II expression, activation of metalloproteinase 13 expression and regulation of Wnt7a and c-jun expression during chondrocyte de-differentiation in vitro. Our results also suggest that expressions of eNOS, Wnt5a and cyclinE1 are regulated by non-canonical Wnt signaling.

Adult T-cell leukemia cells overexpress Wnt5a and promote osteoclast differentiation

AbstractAdult T-cell leukemia/lymphoma (ATL) is etiologically linked to infection with the human T-cell leukemia/lymphoma virus type 1 (HTLV-I). ATL is classified into 4 distinct clinical diseases: acute, lymphoma, chronic, and smoldering. Acute ATL is the most aggressive form, representing 60% of cases and has a 4-year survival of <5%. A frequent complication and cause of death in acute ATL patients is the presence of lytic bone lesions and hypercalcemia. We analyzed the Wnt/β-catenin pathway because of its common role in cancer and bone remodeling. Our study demonstrated that ATL cells do not express high levels of β-catenin but displayed high levels of LEF-1/TCF genes along with elevated levels of β-catenin (LEF-1/TCF target genes) responsive genes. By profiling Wnt gene expression, we discovered that ATL patient leukemia cells shifted expression toward the noncanonical Wnt pathway. Interestingly, ATL cells overexpressed the osteolytic-associated genes—Wnt5a, PTHLH, and RANKL. We further show that Wnt5a secreted by ATL cells favors osteoclast differentiation and expression of RANK. Our results suggest that Wnt5a is a major contributing factor to the increase in osteolytic bone lesions and hypercalcemia found in ATL patients. Anti-Wnt5a therapy may prevent or reduce osteolytic lesions found in ATL patients and improve therapy outcome.

FRI0055 Ectopic calcification is mediated by inflammatory cytokines enhancing differentiation of adipose-derived stem cells into osteoblasts

BackgroundAlthough ectopic cutaneous calcification is occasionally observed in connective tissue disease such as juvenile dermatomyositis (JDM), causing multiple complications, its mechanism remains unclear. Recent reports have suggested the involvement of...

Insulin-like growth factor-I stimulates differentiation of ATII cells to ATI-like cells through activation of Wnt5a

Alveolar type II (ATII) epithelial cells play a crucial role in the repair and remodeling of the lung following injury. ATII cells have the capability to proliferate and differentiate into alveolar type I (ATI) cells in vivo and into an ATI-like phenotype in vitro. While previous reports indicate that the differentiation of ATII cells into ATI cells is a complex biological process, the underlying mechanism responsible for differentiation is not fully understood. To investigate factors involved in this differentiation in culture, we used a PCR array and identified several genes that were either up- or downregulated in ATI-like cells (day 6 in culture) compared with day 2 ATII cells. Insulin-like growth factor-I (IGF-I) mRNA was increased nearly eightfold. We found that IGF-I was increased in the culture media of ATI-like cells and demonstrated a significant role in the differentiation process. Treatment of ATII cells with recombinant IGF-I accelerated the differentiation process, and this effect was abrogated by the IGF-I receptor blocker PQ401. We found that Wnt5a, a member of the Wnt-Frizzled pathway, was activated during IGF-I-mediated differentiation. Both protein kinase C and β-catenin were transiently activated during transdifferentiation. Knocking down Wnt5a using small-interfering RNA abrogated the differentiation process as indicated by changes in the expression of an ATII cell marker (prosurfactant protein-C). Treatment of wounded cells with either IGF-I or Wnt5a stimulated wound closure. These results suggest that IGF-I promotes differentiation of ATII to ATI cells through the activation of a noncanonical Wnt pathway.

Wnt5a signaling mediates biliary differentiation of fetal hepatic stem/progenitor cells in mice

The molecular mechanisms regulating differentiation of fetal hepatic stem/progenitor cells, called hepatoblasts, which play pivotal roles in liver development, remain obscure. Wnt signaling pathways regulate the development and differentiation of stem cells in various organs. Although a β-catenin-independent noncanonical Wnt pathway is essential for cell adhesion and polarity, the physiological functions of noncanonical Wnt pathways in liver development are unknown. Here we describe a functional role for Wnt5a, a noncanonical Wnt ligand, in the differentiation of mouse hepatoblasts. Wnt5a was expressed in mesenchymal cells and other cells of wild-type (WT) midgestational fetal liver. We analyzed fetal liver phenotypes in Wnt5a-deficient mice using a combination of histological and molecular techniques. Expression levels of Sox9 and the number of hepatocyte nuclear factor (HNF)1β(+) HNF4α(-) biliary precursor cells were significantly higher in Wnt5a-deficient liver relative to WT liver. In Wnt5a-deficient fetal liver, in vivo formation of primitive bile ductal structures was significantly enhanced relative to WT littermates. We also investigated the function of Wnt5a protein and downstream signaling molecules using a three-dimensional culture system that included primary hepatoblasts or a hepatic progenitor cell line. In vitro differentiation assays showed that Wnt5a retarded the formation of bile duct-like structures in hepatoblasts, leading instead to hepatic maturation of such cells. Whereas Wnt5a signaling increased steady-state levels of phosphorylated calcium/calmodulin-dependent protein kinase II (CaMKII) in fetal liver, inhibition of CaMKII activity resulted in the formation of significantly more and larger-sized bile duct-like structures in vitro compared with those in vehicle-supplemented controls. Wnt5a-mediated signaling in fetal hepatic stem/progenitor cells suppresses biliary differentiation. These findings also suggest that activation of CaMKII by Wnt5a signaling suppresses biliary differentiation. (HEPATOLOGY 2013;).

β-Arrestin 1 mediates non-canonical Wnt pathway to regulate convergent extension movements

β-Arrestins are multifaceted proteins that play critical roles in termination of G protein-coupled receptor (GPCR) signaling by inducing its desensitization and internalization as well as in facilitation of many intracellular signaling pathways. Here, we examine using Xenopus embryos whether β-arrestin 1 might act as a mediator of β-catenin-independent Wnt (non-canonical) signaling. Xenopus β-arrestin 1 (xβarr1) is expressed in the tissues undergoing extensive cell rearrangements in early development. Gain- and loss-of-function analyses of xβarr1 revealed that it regulates convergent extension (CE) movements of mesodermal tissue with no effect on cell fate specification. In addition, rescue experiments showed that xβarr1 controls CE movements downstream of Wnt11/Fz7 signal and via activation of RhoA and JNK. In line with this, xβarr1 associated with key Wnt components including Ryk, Fz, and Dishevelled. Furthermore, we found that xβarr1 could recover CE movements inhibited by xβarr2 knockdown or its endocytosis defective mutant. Overall, these results suggest that β-arrestin 1 and 2 share interchangeable endocytic activity to regulate CE movements downstream of the non-canonical Wnt pathway.

Sclerostin preserves chondrocyte maintenance by modulating the crosstalk between canonical and non-canonical Wnt pathways

Searchable abstracts of presentations at key conferences on calcified tissues ISSN 2052-1219 (online)

PP064: Wnt5a stimulates migration and invasion in OSCC

Purpose Wnt5a is the most important Wnt protein activating the non-canonical Wnt pathway. It regulates proliferation, differentiation, migration, adhesion and polarity of the cell. Clinical studies have shown that Wnt5a could act as a prognostic marker in various cancers. It seems that Wnt5a acts both as a tumor suppressor (breast, thyroid, colon and livercancer) and as a tumor promotor (malignant melanoma, pancreatic and gastric cancer). In oral squamous cell carcinoma (OSCC) a number of Wnt and Frizzled genes are expressed, mostly Wnt5a and Frizzled-5 but the role of Wnt5a has not yet been thoroughly elucidated. The aim of this study is to evaluate the role of Wnt5a in oral OSCC and its influence on the cell proliferation, migration and invasion. Material and methods The protein content of Wnt5a in two OSCC cell lines (SCC25 and SCC9) was determined by Western blotting. The influence of rWnt5a and two Wnt5a-derived hexapeptides: Foxy5 (an agonist that mimics Wnt5a activity) and Box5 (an antagonist that inhibits Wnt5a) on the migration and proliferation in OSCC cell lines was studied by a scratch assay and BrdU. Invasion influenced by rWnt5a was studied using Boyden chambers. Results Both cell lines express Wnt5a. Dose–response curves of rWnt5a in SCC9 and SCC25 indicate that Wnt5a increases migration with statistically significant effective concentration at 0.4 μg/ml but has no effect on the proliferation of the two cell lines. To confirm this we used Foxy5 and Box5. Foxy5 increases migration with statistically significant effective concentration at 150 μM while Box5 inhibits Wnt5a effect on the migration. Foxy5 and Box5 have no influence on proliferation. Invasion was increased by rWnt5a. Conclusions The results demonstrate that Wnt5a increases migration and invasion but has no influence on proliferation in OSCC cell lines.

Highlights of This Issue

Lung cancer is one of the most prevalent and deadliest cancers worldwide. A major risk factor in the disease comes from the carcinogens produced from cigarette smoking. As such, understanding the cellular mechanisms of detoxification is of general interest. In the current study, mRNA expression analysis indicated that the detoxification enzyme glutathione S-transferase GST-M2 and connective tissue growth factor CCN2 (CTGF) were reduced in lung tumor tissue. Overexpression of GST-M2 increased CTGF expression, reduced cellular migration, and inhibited tumor growth and metastasis in animal models. Importantly, higher expression of GST-M2 and CCN2 using real-time PCR is associated with a favorable prognosis in non–small cell lung cancer (NSCLC). Overall, this study reveals the potential of GST-M2 as a novel tumor suppressor via inhibiting tumor growth and metastasis, which has been demonstrated in vitro and in animal models. The antitumor effects of GST-M2 and CCN2 activity in animal models have provoked an intense interest in the development of small-molecule activators of GST-M2 and CCN2 (and their gene therapy) to prevent NSCLCs in the future.As tumors grow, there is an increased demand for nutrients and oxygen. Therefore, intratumoral hypoxia is considered a major driving force in breast cancer progression and has been linked to metastasis. Gilkes and colleagues demonstrated that hypoxia-inducible factor 1 (HIF-1) mediated increased expression of collagen hydroxylases (PLOD1 and PLOD2), which modify type I collagen prior to its secretion into the extracellular matrix (ECM). In addition, human breast cancer specimens stratified by elevated PLOD2 expression were associated significantly with increased patient mortality. In animal models, PLOD2 knockdown resulted in a marked decrease in tumor stiffness, local tissue invasion, and metastasis to lymph nodes and lungs without affecting primary tumor growth. Taken together, HIF-1 stimulates PLOD2 expression and collagen biogenesis to promote metastasis of hypoxic breast cancer cells. Thus, specific inhibitors of HIF-1 and/or collagen hydroxylases may be of clinical benefit for preventing breast cancer metastasis.The primary treatment for advanced/metastatic prostate cancer involves androgen deprivation therapy. Unfortunately, recurrence develops due to reactivation of androgen receptor (AR) activity resulting in castration-resistance and frequent osteoblastic bone metastasis. Based on genomic analyses, Zheng and colleagues mechanistically identified WNT7B as a novel target of AR in castration-resistant prostate cancer (CRPC). Manipulation of WNT7B levels promoted CRPC cell growth under androgen-deprived conditions and activated a noncanonical WNT pathway involving protein kinase C (PKC) isozymes. Critically, WNT7B was selectively upregulated in human xenografts that induce an osteoblastic reaction when grown in bone. These results establish a connection between AR and WNT signaling and suggest a unique opportunity to develop effective therapies for advanced prostate cancer by targeting the AR-WNT7B-PKCs axis, which would inhibit CRPC growth and prevent the formation of a metastatic reservoir in bone.Considered a major driver of invasive solid tumor progression, epithelial-mesenchymal transformation (EMT) is a cellular reprogramming by which malignant epithelial cells generally lose their cell–cell adhesion properties to become highly invasive. Austin and colleagues used mesenchymally transformed breast cancer cells to demonstrate that the small molecule sarasinoside A1, at noncytotoxic doses, reversed a number of aspects of EMT. Sarasinoside A1 inhibited cell invasion and promoted cell adhesion in three-dimensional cultures. Interestingly, sarasinoside A1 also initiated a morphologic re-epithelialization and stabilized the cytoskeleton at sites of nascent cell–cell contact. Combined, these findings indicate the potential to impede tumor invasion and metastasis without the need to reinduce the expression of cell adhesion molecules, such as E-cadherin, that are often lost or silenced during mesenchymal transformation.

Components of the Canonical and Non-Canonical Wnt Pathways Are Not Mis-Expressed in Pituitary Tumors

IntroductionCanonical and non-canonical Wnt pathways are involved in the genesis of multiple tumors; however, their role in pituitary tumorigenesis is mostly unknown.ObjectiveThis study evaluated gene and protein expression of Wnt pathways in pituitary tumors and whether these expression correlate to clinical outcome.Materials and MethodsGenes of the Wnt canonical pathway: activating ligands (WNT11, WNT4, WNT5A), binding inhibitors (DKK3, sFRP1), β-catenin (CTNNB1), β-catenin degradation complex (APC, AXIN1, GSK3β), inhibitor of β-catenin degradation complex (AKT1), sequester of β-catenin (CDH1), pathway effectors (TCF7, MAPK8, NFAT5), pathway mediators (DVL-1, DVL-2, DVL-3, PRICKLE, VANGL1), target genes (MYB, MYC, WISP2, SPRY1, TP53, CCND1); calcium dependent pathway (PLCB1, CAMK2A, PRKCA, CHP); and planar cell polarity pathway (PTK7, DAAM1, RHOA) were evaluated by QPCR, in 19 GH-, 18 ACTH-secreting, 21 non-secreting (NS) pituitary tumors, and 5 normal pituitaries. Also, the main effectors of canonical (β-catenin), planar cell polarity (JNK), and calcium dependent (NFAT5) Wnt pathways were evaluated by immunohistochemistry.ResultsThere are no differences in gene expression of canonical and non-canonical Wnt pathways between all studied subtypes of pituitary tumors and normal pituitaries, except for WISP2, which was over-expressed in ACTH-secreting tumors compared to normal pituitaries (4.8x; p = 0.02), NS pituitary tumors (7.7x; p = 0.004) and GH-secreting tumors (5.0x; p = 0.05). β-catenin, NFAT5 and JNK proteins showed no expression in normal pituitaries and in any of the pituitary tumor subtypes. Furthermore, no association of the studied gene or protein expression was observed with tumor size, recurrence, and progressive disease. The hierarchical clustering showed a regular pattern of genes of the canonical and non-canonical Wnt pathways randomly distributed throughout the dendrogram.ConclusionsOur data reinforce previous reports suggesting no activation of canonical Wnt pathway in pituitary tumorigenesis. Moreover, we describe, for the first time, evidence that non-canonical Wnt pathways are also not mis-expressed in the pituitary tumors.

Abstract 553: Interactions among JNK, p38, Akt and canonical Wnt pathways in murine mammary adenocarcinoma cells reexpressing Glypican-3 (GPC3).

Abstract GPC3 is expressed in normal mammary tissues, but it disappears in tumors. We have transfected the GPC3 gene into the murine mammary adenocarcinoma LM3 cells, demonstrating that it acts as a metastasis suppressor. We have also reported that LM3-GPC3 cells exhibit an inhibition of Akt and canonical Wnt pathways, while they show an activation of non-canonical Wnt (JNK) and p38 signaling. The aim of this work was to study the interactions among GPC3 modulated pathways. For this, subconfluent LM3-GPC3 cells were treated with SB203589 or SP600125 (p38 and JNK pharmacological inhibitors, respectively), or with the vehicle. Also, we introduced by viral infection a constitutively active variant of Akt1 (CA Akt), or the empty vector, into LM3-GPC3 cells. The effect of the different treatments on the activity of the other pathways was evaluated by WB. We demonstrated that in addition to the central role of JNK in the non-canonical Wnt pathway, it also regulates canonical signaling. We found that SP600125 induced a 2 to 5-fold increase in the cytoplasmic β-Catenin levels, as well it reduced 2 to 6 times E-Cadherin expression. Therefore, our results suggest that JNK activation would be required for the canonical Wnt signaling inhibition induced by GPC3. On the other side, p38 pathway is considered independent of Wnt signaling. In association, SB203589 did not modulate either cytoplasmic β-Catenin or E-Cadherin levels, suggesting that p38 activation would not participate in the canonical Wnt pathway inhibition induced by GPC3. We also observed that LM3-GPC3 cells expressing CA Akt, showed less E-Cadherin than controls. So, Akt inhibition would be essential to increase of E-Cadherin expression induced by GPC3. In relation with the non-canonical Wnt pathway, we found that SB203589 induced a partial decrease in phospho-JNK levels. Therefore, p38 would be involved in the non-canonical Wnt signaling activation induced by GPC3. Inhibitors actions on Akt pathway were analyzed. We determined that SP600125 had no effect on Akt activation, suggesting that Akt inhibition induced by GPC3 is independent of non-canonical Wnt signaling. On the other hand, although without reaching LM3-vector levels, SB203589 caused a 2-fold increase in phospho-Akt levels. This indicates that the activation of p38 would be necessary to induce the inhibition of Akt signaling detected in GPC3 reexpressing cells. In sum, we have dissected some of the functional and hierarchical interactions between the pathways modulated by GPC3 that may contribute to the metastasis suppressing activity of this proteoglycan. Citation Format: Maria Giselle Peters, Rocio Tascon, Lilian F. Castillo, Elisa Bal de Kier Joffe. Interactions among JNK, p38, Akt and canonical Wnt pathways in murine mammary adenocarcinoma cells reexpressing Glypican-3 (GPC3). [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 553. doi:10.1158/1538-7445.AM2013-553

Abstract 3795: Vangl2 and Prickle1 expression, interaction and regulation of Wnt/PCP signaling in medulloblastoma and neuroblastoma.

Abstract Background /Aims: Wnt are a family of intercellular signaling factors that regulates a wide range of functions during embryonic development including cell proliferation, cell fate determination, differentiation, cell polarity and cell migration. They bind to Frizzled receptors and thereafter proceed via Dishevelled to several intracellular pathways known as the canonical and non-canonical signaling pathways. Activation of the canonical pathway results in an accumulation of cytoplasmic beta-catenin levels. Increased Wnt/beta-catenin signaling is associated with many forms of cancer, including the embryonic neural childhood tumors medulloblastoma and neuroblastoma. The non-canonical Wnt signaling pathways can inhibit the canonical signaling pathway, although the mechanism is still unclear. In this study, we investigate the roles of Prickle1 and Van Gogh-Like 2 (Vangl2), two planar cell polarity (PCP) genes in regulation of the cytoskeleton, Wnt/beta-catenin activity and tumorigenicity in neuroblastoma and medulloblastoma. Methods: mRNA and protein expression of human Prickle1, Vangl2 and beta-catenin were examined in neuroblastoma and medulloblastoma cell lines. siRNA and cDNA transfection were performed together with co-immunoprecipitation and immunocytochemistry. Results and conclusions: We show that Prickle1 and Vangl2 are expressed in neuroblastoma and medulloblastoma cell lines at different levels. Decreased Prickle1 expression correlates with increased levels of Wnt/beta-catenin in both medullo- and neuroblastoma cell lines, demonstrating a downregulation of PCP components and a possible activation of the canonical Wnt signaling pathway. Immunoprecipitation demonstrated that Prickle1 is present in complex with Vangl2. However, the exact mode of interaction between Prickle1 and Vangl2 remains to be eluciated. Microarray analysis revealed that low expressions of Prickle1 or Vangl2 are both associated significantly worse clinical outcome in neuroblastoma. Additionally, siRNA experiments revealed that knockdown of Prickle1 and Vangl2 increased cell proliferation of neuroblastoma cells. Taken together this indicate that the non-canonical Wnt pathway may be an interesting therapeutic target in embryanol neural childhood tumors. Citation Format: Cecilia H. Dyberg, Panagiotis Papachristou, Hugo Lagercrantz, John I Johnsen, Malin Wickström. Vangl2 and Prickle1 expression, interaction and regulation of Wnt/PCP signaling in medulloblastoma and neuroblastoma. [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 3795. doi:10.1158/1538-7445.AM2013-3795

Van-Gogh-like 2 antagonises the canonical WNT pathway and is methylated in colorectal cancers

Background:Aberrant activation of the canonical WNT signaling is a feature of colorectal cancer (CRC). Van-Gogh-like 2 (VANGL2) belongs to the non-canonical WNT pathway whose activation inhibits canonical WNT signaling. In this study, we investigated the role of VANGL2 and its epigenetic regulation in CRC.Methods:Van-Gogh-like 2 expression and promoter methylation after 5-aza-2′-deoxycytidine (5-aza) treatment were evaluated in CRC cells. DNA samples from 418 sporadic CRCs were tested for VANGL2 promoter methylation and microsatellite instability (MSI). Proliferation, colony formation and activation of the WNT pathway were tested in cells after VANGL2 overexpression.Results:Van-Gogh-like 2 mRNA was significantly higher in 5-aza-treated RKO, LOVO and SW48, whereas no differences were found in SW480. Van-Gogh-like 2 was fully methylated in RKO, SW48, HCT116, DLD1 and Caco2; partially methylated in LOVO, LS174T and SW837; and unmethylated in SW480, SW620 and HT29. Higher expression of VANGL2 mRNA was found in the unmethylated cell lines. In CRC specimens (8.93% MSI), methylated VANGL2 was associated with MSI, higher grade, proximal colon location and BRAF mutation. Van-Gogh-like 2 overexpression in SW480 significantly decreased proliferation, colony formation and β-catenin levels.Conclusion:Van-Gogh-like 2 is frequently methylated in MSI-CRCs with BRAF mutation and may act as a tumour suppressor gene, counteracting WNT/β-catenin signaling.

Suppression of MMQ cells by fulvestrant: possible mechanism of action and potential application for bromocriptine-resistant prolactinomas

Bromocriptine is an effective treatment for most prolactinomas. Estrogen receptor (ER) antagonists are an alternative for treating patients with bromocriptine-resistant prolactinomas (BCRP). Previously, we reported that fulvestrant, a selective ER antagonist, significantly inhibited the proliferation of, and prolactin secretion by, MMQ cells, a prolactin-secreting rat pituitary cell line, an exemplary model for prolactinoma. In this study, we used fulvestrant to block ERα expression by MMQ cells and analyzed the expression of β-catenin and Wnt inhibitory factor-1 (WIF1) to investigate the effects of fulvestrant on the Wnt signaling pathway. In addition, we examined the gene expression of ERα, β-catenin and WIF1 in clinical BCRP specimens to explore the correlation between gender and clinical features. There was no significant difference in β-catenin expression between fulvestrant-treated cells and untreated cells, whereas WIF1 expression was higher in the treated cells. In clinical BCRP specimens, ERα expression was higher (especially in male patients), whereas β-catenin expression was similar to normal pituitaries. In addition, WIF1 expression was significantly lower in BCRP specimens than in normal pituitaries. The tumor volume was larger in male patients than in female patients. Prolactin concentration was positively correlated with tumor volume, and a positive linear correlation was observed between ERα expression and tumor volume. In conclusion, the anti-tumor activity of fulvestrant on MMQ cells seems to be associated with ERα and the non-canonical Wnt pathway, and higher ERα levels in male patients with BCRP may contribute to the larger tumor volumes observed. Fulvestrant holds promise as a therapeutic agent for BCRP.