Soluble Wnt Antagonist Research Articles

Abstract 5537: How aging promotes immune mediated reactivation from metastatic melanoma dormancy

Abstract Disseminated cancer cells that escape the primary tumor can seed distal tissues but may take several years to grow into clinically detectable metastases, a phenomenon termed tumor dormancy. Despite its importance in metastasis and residual disease, few studies have been able to successfully model melanoma dormancy. We have previously shown that while tumors grow more slowly in aged mouse skin, they form more lung metastases in aged mice compared to young mice. We queried whether the lung microenvironment undergoes age-related changes that establish a permissive niche for metastatic outgrowth. We identified that Wnt5A and AXL are not only required for efficient dissemination away from the primary tumor but also activate dormancy of melanoma cells within the lung. The young lung microenvironment maintains melanoma cells in a dormant state; however, age-associated reprograming of lung fibroblasts increases secretion of the soluble Wnt antagonist sFRP1, which inhibits both Wnt5A and AXL to enable reactivation from dormancy and the formation of larger metastatic colonies in the aged lung. We found that downregulation of AXL in melanoma cells leads to an increase in the related TAM family receptor MERTK, which promotes a proliferative melanoma phenotype and enables reactivation from dormancy. We have now found that both the aged-pre and post metastatic niche regulate immune cells in the lung to create a permissive niche for reactivation of metastatic melanoma. NK cells are significantly decreased in the healthy lungs of aged mice, are significantly less active, and have increased exhaustion markers. NK cell infiltration remains low in early and late-stage metastasis in aged mice. Depletion of NK cells in young mice is sufficient to induce reactivation from dormancy. Further, MERTK induced reactivation of melanoma cells results in paracrine secretion of its own ligand PROS1 to facilitate a growth permissive lung microenvironment. Melanoma-secreted PROS1 increases infiltration of PMN-MDSCs and decreases macrophage infiltration to maintain an immunosuppressive lung niche for efficient outgrowth. Selective inhibition of PMN-MDSCs using a TRIAL-R2 agonistic antibody significantly decreases metastatic outgrowth and promotes smaller, non-proliferative dormant colonies. Our findings indicate a significant role that aging plays in altering NK-cell infiltration and function to create a growth permissive pre-metastatic niche and how reactivation from dormancy can further contribute to create an immunosuppressive microenvironment for efficient outgrowth via PROS1 induced infiltration of PMN-MDSCs. Importantly, the clear differences found in our young and aged mouse modelling systems for outgrowth in metastatic tissues necessitates the need for age-appropriate pre-clinical modelling for better patient and disease representation. Citation Format: Pulkit Datt, Jhon Passamonte, Christopher Price, Daniel Zabransky, Yash Chhabra, Ashani Weeraratna, Mitchell E. Fane. How aging promotes immune mediated reactivation from metastatic melanoma dormancy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5537.

Abstract IA014: The role of aging in reactivation from metastatic melanoma dormancy

Abstract Disseminated cancer cells (DCCs) that escape the primary site can seed in distal tissues, but may take several years, or even decades to grow out into overt metastases, a phenomenon termed tumor dormancy. Despite its importance in metastasis and residual disease, few studies have been able to successfully model or characterize dormancy within melanoma. Our previous data has indicated that while tumors grow more slowly in aged mouse skin, they form more aged lung metastases. We have previously shown that dermal fibroblasts were key drivers of age-related changes in the skin to promote a more aggressive melanoma phenotype. A model of melanoma progression that addresses these microenvironmental complexities is the phenotype switching model, which argues that melanoma cells switch between a proliferative cell state and a slower-cycling, invasive state. We queried whether the lung microenvironment undergoes similar age-related changes that provide a permissive niche for metastatic outgrowth. Our new data identified that while Wnt5A and AXL are required for efficient dissemination from the primary tumor towards metastatic tissues, they act as master regulators of activating melanoma dormancy within the lung. The young lung microenvironment maintains this dormant melanoma state; however, age induced reprograming of lung fibroblasts increases their secretion of the soluble Wnt antagonist sFRP1, which inhibits both Wnt5A and AXL to enable reactivation from dormancy and the formation of larger metastatic colonies in the aged lung. We find that downregulation of AXL in melanoma cells leads to an increase in the related TAM family receptor MERTK, which promotes a proliferative melanoma phenotype, enables reactivation from dormancy and induces efficient metastatic outgrowth in aged models. Follow up data from these models highlights decreases in immune infiltration of CD4+ and CD8+ T-cells, which appears to be partially mediated by an increase in secretion of Arginase-1 (ARG1) from aged lung fibroblasts. Further, we find that aged lung fibroblasts secrete CXCL1 which promotes infiltration of immunosuppressive T-regulatory cells and Myeloid Derived Suppressive Cells. Finally, we see dramatic changes in extracellular matrix secretion and remodeling from young vs aged lung fibroblasts, which alters in vitro melanoma growth to promote dormancy in melanoma cells grown on young lung fibroblast ECM. Overall, we find that a plethora of age-related changes in metastatic microenvironments such as the lung contribute to an increase in melanoma progression relative to younger niches. This not only provides novel tools to assess metastatic dormancy in melanoma, which is critically understudied due to a lack of pre-clincal in vitro and in vivo models, but also necessitates the idea that age needs to be considered in pre-clinical modelling of age-related cancers such as melanoma, where the median age of diagnosis is 63, and when there is a clear increase in incidence, mortality and metastasis within geriatric patients. Citation Format: Mitchell Fane, Yash Chhabra, Gretchen Alicea, Daniel Zabransky, Laura Hüser, Devin Maranto, Julio Aguirre-Ghiso, Ashani Weeraratna. The role of aging in reactivation from metastatic melanoma dormancy [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr IA014.

Stromal changes in the aged lung induce an emergence from melanoma dormancy.

Disseminated cancer cells from primary tumours can seed in distal tissues, but may take several years to form overt metastases, a phenomenon that is termed tumour dormancy. Despite its importance in metastasis and residual disease, few studies have been able to successfully characterize dormancy within melanoma. Here we show that the aged lung microenvironment facilitates a permissive niche for efficient outgrowth of dormant disseminated cancer cells-in contrast to the aged skin, in which age-related changes suppress melanoma growth but drive dissemination. These microenvironmental complexities can be explained by the phenotype switching model, which argues that melanoma cells switch between a proliferative cell state and a slower-cycling, invasive state1-3. It was previously shown that dermal fibroblasts promote phenotype switching in melanoma during ageing4-8. We now identify WNT5A as an activator of dormancy in melanoma disseminated cancer cells within the lung, which initially enables the efficient dissemination and seeding of melanoma cells in metastatic niches. Age-induced reprogramming of lung fibroblasts increases their secretion of the soluble WNT antagonist sFRP1, which inhibits WNT5Ain melanoma cells and thereby enables efficient metastatic outgrowth. We also identify the tyrosine kinase receptors AXL and MER as promoting a dormancy-to-reactivation axiswithin melanoma cells. Overall, we find that age-induced changes in distal metastatic microenvironments promote the efficient reactivation of dormant melanoma cells in the lung.

Multi-Targeting DKK1 and LRP6 Prevents Bone Loss and Improves Fracture Resistance in Multiple Myeloma.

An imbalance between bone resorption and bone formation underlies the devastating osteolytic lesions and subsequent fractures seen in more than 90% of multiple myeloma (MM) patients. Currently, Wnt-targeted therapeutic agents that prevent soluble antagonists of the Wnt signaling pathway, sclerostin (SOST) and dickkopf-1 (DKK1), have been shown to prevent bone loss and improve bone strength in preclinical models of MM. In this study, we show increasing Wnt signaling via a novel anti-low-density lipoprotein receptor-related protein 6 (LRP6) antibody, which potentiates Wnt1-class ligand signaling through binding the Wnt receptor LRP6, prevented the development of myeloma-induced bone loss primarily through preventing bone resorption. When combined with an agent targeting the soluble Wnt antagonist DKK1, we showed more robust improvements in bone structure than anti-LRP6 treatment alone. Micro-computed tomography (μCT) analysis demonstrated substantial increases in trabecular bone volume in naïve mice given the anti-LRP6/DKK1 combination treatment strategy compared to control agents. Mice injected with 5TGM1eGFP murine myeloma cells had significant reductions in trabecular bone volume compared to naïve controls. The anti-LRP6/DKK1 combination strategy significantly improved bone volume in 5TGM1-bearing mice by 111%, which was also superior to anti-LRP6 single treatment; with similar bone structural changes observed within L4 lumbar vertebrae. Consequently, this combination strategy significantly improved resistance to fracture in lumbar vertebrae in 5TGM1-bearing mice compared to their controls, providing greater protection against fracture compared to anti-LRP6 antibody alone. Interestingly, these improvements in bone volume were primarily due to reduced bone resorption, with significant reductions in osteoclast numbers and osteoclast surface per bone surface demonstrated in 5TGM1-bearing mice treated with the anti-LRP6/DKK1 combination strategy. Importantly, Wnt stimulation with either single or combined Wnt-targeted agents did not exacerbate tumor activity. This work provides a novel approach of targeting both membrane-bound and soluble Wnt pathway components to provide superior skeletal outcomes in patients with multiple myeloma and other bone destructive cancers. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

The Wnt Signaling Pathway Is Differentially Expressed during the Bovine Herpesvirus 1 Latency-Reactivation Cycle: Evidence That Two Protein Kinases Associated with Neuronal Survival, Akt3 and BMPR2, Are Expressed at Higher Levels during Latency.

Sensory neurons in trigeminal ganglia (TG) of calves latently infected with bovine herpesvirus 1 (BoHV-1) abundantly express latency-related (LR) gene products, including a protein (ORF2) and two micro-RNAs. Recent studies in mouse neuroblastoma cells (Neuro-2A) demonstrated ORF2 interacts with β-catenin and a β-catenin coactivator, high-mobility group AT-hook 1 (HMGA1) protein, which correlates with increased β-catenin-dependent transcription and cell survival. β-Catenin and HMGA1 are readily detected in a subset of latently infected TG neurons but not TG neurons from uninfected calves or reactivation from latency. Consequently, we hypothesized that the Wnt/β-catenin signaling pathway is differentially expressed during the latency and reactivation cycle and an active Wnt pathway promotes latency. RNA-sequencing studies revealed that 102 genes associated with the Wnt/β-catenin signaling pathway were differentially expressed in TG during the latency-reactivation cycle in calves. Wnt agonists were generally expressed at higher levels during latency, but these levels decreased during dexamethasone-induced reactivation. The Wnt agonist bone morphogenetic protein receptor 2 (BMPR2) was intriguing because it encodes a serine/threonine receptor kinase that promotes neuronal differentiation and inhibits cell death. Another differentially expressed gene encodes a protein kinase (Akt3), which is significant because Akt activity enhances cell survival and is linked to herpes simplex virus 1 latency and neuronal survival. Additional studies demonstrated ORF2 increased Akt3 steady-state protein levels and interacted with Akt3 in transfected Neuro-2A cells, which correlated with Akt3 activation. Conversely, expression of Wnt antagonists increased during reactivation from latency. Collectively, these studies suggest Wnt signaling cooperates with LR gene products, in particular ORF2, to promote latency.IMPORTANCE Lifelong BoHV-1 latency primarily occurs in sensory neurons. The synthetic corticosteroid dexamethasone consistently induces reactivation from latency in calves. RNA sequencing studies revealed 102 genes associated with the Wnt/β-catenin signaling pathway are differentially regulated during the latency-reactivation cycle. Two protein kinases associated with the Wnt pathway, Akt3 and BMPR2, were expressed at higher levels during latency but were repressed during reactivation. Furthermore, five genes encoding soluble Wnt antagonists and β-catenin-dependent transcription inhibitors were induced during reactivation from latency. These findings are important because Wnt, BMPR2, and Akt3 promote neurogenesis and cell survival, processes crucial for lifelong viral latency. In transfected neuroblastoma cells, a viral protein expressed during latency (ORF2) interacts with and enhances Akt3 protein kinase activity. These findings provide insight into how cellular factors associated with the Wnt signaling pathway cooperate with LR gene products to regulate the BoHV-1 latency-reactivation cycle.

A Genome-wide Association Study of Dupuytren Disease Reveals 17 Additional Variants Implicated in Fibrosis

Individuals with Dupuytren disease (DD) are commonly seen by physicians and surgeons across multiple specialties. It is an increasingly common and disabling fibroproliferative disorder of the palmar fascia, which leads to flexion contractures of the digits, and is associated with other tissue-specific fibroses. DD affects between 5% and 25% of people of European descent and is the most common inherited disease of connective tissue. We undertook the largest GWAS to date in individuals with a surgically validated diagnosis of DD from the UK, with replication in British, Dutch, and German individuals. We validated association at all nine previously described signals and discovered 17 additional variants with p ≤ 5 × 10−8. As a proof of principle, we demonstrated correlation of the high-risk genotype at the statistically most strongly associated variant with decreased secretion of the soluble WNT-antagonist SFRP4, in surgical specimen-derived DD myofibroblasts. These results highlight important pathways involved in the pathogenesis of fibrosis, including WNT signaling, extracellular matrix modulation, and inflammation. In addition, many associated loci contain genes that were hitherto unrecognized as playing a role in fibrosis, opening up new avenues of research that may lead to novel treatments for DD and fibrosis more generally. DD represents an ideal human model disease for fibrosis research.

Anti-Sclerostin Treatment Prevents Multiple Myeloma Induced Bone Loss and Reduces Tumor Burden

Multiple myeloma (MM) is a malignancy of plasma cells and is characterized by unrestricted tumor cell growth in bone marrow (BM). MM causes destructive osteolytic lesions causing bone fracture, bone pain, hypercalcaemia, and nerve-compression, resulting from increased bone resorption and suppressed bone formation. Despite the introduction of agents to inhibit bone resorption, such as bisphosphonates, which prevent further bone loss, approaches to preventing osteoblast suppression and repair bone lesions are limited and there are no agents available clinically.The wnt/β-catenin pathway plays a critical role in the regulation of bone formation. Production of the soluble wnt antagonist dickkopf1 (Dkk1) by MM cells has been implicated in MM inhibition of bone formation. As such, Anti-Dkk1 treatment prevents bone disease in pre-clinical models of MM and is in early clinical development. However, Dkk1 is not expressed by all myeloma cells; hence only a proportion of patients may respond to anti-Dkk1 therapy. Sclerostin (Scl) is a soluble wnt antagonist whose expression, unlike Dkk1, is restricted to osteocytes; therefore Scl targeted agents may have less off target effects. Anti-Sclerostin (Anti-Scl) treatment increased bone formation and bone volume in experimental models of osteoporosis, and increased bone mineral density in phase II osteoporosis clinical trials. However, Anti-Scl treatment effects on myeloma bone disease are unknown. Further, cells of the BM such as osteoblasts have been implicated in the regulation of MM cell survival and growth. Thus, in the present study we explored the potential for Anti-Scl therapy to prevent MM induced bone loss and inhibit MM growth in both murine and human xenograft MM models.Female C57BLKalwRij mice (n=8) were injected i.v, with 5TGM1/eGFP murine MM cells (1×106) and female SCID/beige mice (n=10) were injected i.v. with MM1S/Luc/eGFP human MM cells (4 × 106). 24 hours later, naïve mice (without tumor cells) or mice bearing MM cells were treated with anti-sclerostin antibody (Anti-Scl) (100mg/kg i.v) or control antibody. Mice were sacrificed at day 21 (MM1S) or day 28 (5TGM1) and the effect of Anti-Scl on bone structure in the femora and vertebrae were determined by microCT analysis. The effect of Anti-Scl on MM burden was determined by bioluminescent imaging (BLI) performed twice weekly from week 1 using a Xenogen IVIS system, whereas MM burden in 5TGM1/eGFP bearing mice was examined by FACS analysis.Anti-Scl treatment in naïve C57BLKalwRij mice increased trabecular bone volume fraction (BV/TV, 39%, p<0.01, Fig. 1B) in the femur, which was mediated by increases in trabecular thickness (Tb.Th, 42%, p<0.01). Treatment also increased cortical bone volume (22%, p<0.01) in the femur and increased trabecular BV/TV in the vertebra (32%, p<0.01). This demonstrated the potent bone anabolic effect of Anti-Scl independent of myeloma cells. Injection of 5TGM1 cells resulted in a decrease in femoral trabecular BV/TV (30%, p<0.01) through a 30% reduction in trabecular number (TbN) (p<0.01), but no effect on Tb.Th (Figs. 1A and B), whilst also reducing cortical bone volume (BV) by 6% (p<0.05). Vertebrae were also impacted by 5TGM1 tumor growth with a 29% reduction in Tb BV/TV through a 23% reduction in Tb.Th (p<0.01) and also a 15% reduction in cortical BV (p<0.01). Treatment of 5TGM1-bearing mice with Anti-Scl increased trabecular BV/TV (46%, p<0.01) and Tb.Th (30%, p<0.01) to values equivalent to femora of naïve, non-tumor bearing, control mice. Treatment with Anti-Scl also increased cortical BV by 16% (p<0.01), vertebral Tb BV/TV by 29% and cortical BV by 36% in 5TGM1 burdened mice (p<0.01).Treatment of 5TGM1-bearing mice with Anti-Scl had no effect on the proportion 5TGM1/eGFP cells in the BM or spleen. However Anti-Scl treatment significantly suppressed tumor progression in the MM1S model at 3, 3.5 and 4 weeks post cell injection, as determined by BLI imaging (p=0.02, wk 3; p=0.0019, wk 3.5, and p=0.0068, wk 4, 2-tailed t-tests, Fig. 1C).These data demonstrate that Anti-Scl antibody treatment can prevent development of myeloma bone disease. Furthermore, Anti-Scl treatment also suppressed tumor growth, supporting the possibility that targeting the BM microenvironment with this agent may slow disease progression. Our findings highlight the potential clinical application of Anti-Scl antibody treatment in patients with MM and other bone destructive cancers. [Display omitted] DisclosuresKneissel:Novartis Institutes for Biomedical Research, Novartis Pharma AG: Employment. Kramer:Novartis Pharma AG: Employment. Brooks:Spouse works for Boston Biomedical Inc: Employment.

Secreted Frizzled-related protein potentiation versus inhibition of Wnt3a/β-catenin signaling

Wnt signaling regulates a variety of cellular processes during embryonic development and in the adult. Many of these activities are mediated by the Frizzled family of seven-pass transmembrane receptors, which bind Wnts via a conserved cysteine-rich domain (CRD). Secreted Frizzled-related proteins (sFRPs) contain an amino-terminal, Frizzled-like CRD and a carboxyl-terminal, heparin-binding netrin-like domain. Previous studies identified sFRPs as soluble Wnt antagonists that bind directly to Wnts and prevent their interaction with Frizzleds. However, subsequent observations suggested that sFRPs and Frizzleds form homodimers and heterodimers via their respective CRDs, and that sFRPs can stimulate signal transduction. Here, we present evidence that sFRP1 either inhibits or enhances signaling in the Wnt3a/β-catenin pathway, depending on its concentration and the cellular context. Nanomolar concentrations of sFRP1 increased Wnt3a signaling, while higher concentrations blocked it in HEK293 cells expressing a SuperTopFlash reporter. sFRP1 primarily augmented Wnt3a/β-catenin signaling in C57MG cells, but it behaved as an antagonist in L929 fibroblasts. sFRP1 enhanced reporter activity in L cells that were engineered to stably express Frizzled 5, though not Frizzled 2. This implied that the Frizzled expression pattern could determine the response to sFRP1. Similar results were obtained with sFRP2 in HEK293, C57MG and L cell reporter assays. CRDsFRP1 mimicked the potentiating effect of sFRP1 in multiple settings, contradicting initial expectations that this domain would inhibit Wnt signaling. Moreover, CRDsFRP1 showed little avidity for Wnt3a compared to sFRP1, implying that the mechanism for potentiation by CRDsFRP1 probably does not require an interaction with Wnt protein. Together, these findings demonstrate that sFRPs can either promote or suppress Wnt/β-catenin signaling, depending on cellular context, concentration and most likely the expression pattern of Fzd receptors.

Use of a Molecular Genetic Platform Technology to Produce Human Wnt Proteins Reveals Distinct Local and Distal Signaling Abilities

Functional and mechanistic studies of Wnt signaling have been severely hindered by the inaccessibility of bioactive proteins. To overcome this long-standing barrier, we engineered and characterized a panel of Chinese hamster ovary (CHO) cell lines with inducible transgenes encoding tagged and un-tagged human WNT1, WNT3A, WNT5A, WNT7A, WNT11, WNT16 or the soluble Wnt antagonist Fzd8CRD, all integrated into an identical genomic locus. Using a quantitative real-time bioluminescence assay, we show that cells expressing WNT1, 3A and 7A stimulate Wnt/beta-catenin reporter activity, while the other WNT expressing cell lines interfere with this activation. Additionally, in contrast to WNT3A, WNT1 only exhibits activity when cell-associated, and thus only signals to neighboring cells. The reporter assay also revealed a rapid decline of Wnt activity at 37°C, indicating that Wnt activity is highly labile. These engineered cell lines will reduce the cost of making and purifying Wnt proteins and serve as a continuous, reliable and regulatable source of Wnts to research laboratories around the world.

Epigenetic dysregulation of the Wnt signalling pathway in chronic lymphocytic leukaemia

Background:Wnt signalling has recently been implicated in the pathogenesis of cancer.Methods:This study investigated the activity of Wnt signalling in peripheral blood chronic lymphocytic leukaemia (CLL) lymphocytes, and the methylation status...

Epigenetic dysregulation of Wnt signaling pathway in multiple myeloma

Wnt signaling has recently been implicated in carcinogenesis. We studied the activity of Wnt signaling and the methylation status of WIF1, DKK3, APC, SFRP1, SFRP2, SFRP4 and SFRP5 by methylation-specific PCR in myeloma cell lines and primary myeloma samples. Of the four cell lines, Wnt signaling was constitutively activated in LP1 and WL2, correlating with hypermethylation and hence silencing. Moreover, 5-aza-2'-deoxycytidine treatment of these two cell lines showed progressive demethylation of methylated Wnt inhibitors, re-expression of transcripts and downregulation of Wnt signaling. In both LP1 and WL2 cells, multiple Wnts and Fzs were simultaneously expressed. Treatment of WL2, in which SFRP1 was completely methylated, with recombinant secreted Frizzled-related protein 1 (SFRP1) induced downregulation of Wnt signaling and inhibition of proliferation. In primary myeloma samples, 42% patients had methylation of at least one of these seven genes, of which 61.9% had > or = 2 genes methylated. In conclusion, Wnt signaling is constitutively activated in myeloma, associated with methylation silencing of one or multiple soluble Wnt antagonists. An autocrine loop regulating Wnt signaling was demonstrated in the myeloma plasma cells, in which cellular proliferation was efficiently inhibited by recombinant SFRP1. Methylation study of a panel of genes, regulating a cellular pathway instead of isolated genes, is important.

Adipocyte-derived products induce the transcription of the StAR promoter and stimulate aldosterone and cortisol secretion from adrenocortical cells through the Wnt-signaling pathway

Obesity is associated with hypersecretion of cortisol and aldosterone and a high prevalence of arterial hypertension. At the cellular level, a direct effect of adipocytes on the expression of the steroidogenic acute regulatory (StAR) protein, a regulator of cortisol and aldosterone synthesis, and on aldosterone and cortisol secretion has been shown. However, the molecular mechanisms mediating this effect are not known. Wnt-signaling molecules are secreted by adipocytes and regulate the activity of SF-1, a key transcription factor in adrenal steroidogenesis. Therefore, we investigated whether adipocytes stimulate adrenal steroidogenesis through the activation of Wnt-signaling. Using immunohistochemistry, we detected the expression of frizzled and beta-catenin in the adult human adrenal cortex. Transient transfection of a Wnt-dependent reporter-gene into adrenal NCI-H295R cells showed an induction of Wnt-mediated transcription to 308% after treatment with human fat cell-conditioned medium (FCCM). This finding was paralleled by an induction of StAR promoter activity (420%) by FCCM. The induction of StAR promoter activity by FCCM was inhibited by 49% when Wnt-signaling was blocked by the soluble Wnt-antagonist secreted Frizzled-Related-Protein-1 (sFRP-1). Overexpression of a constitutively active mutant of beta-catenin induced the transcription of the StAR promoter (440%). beta-Catenin and FCCM induced SF-1-mediated transcription at a SF-1-driven reporter gene (420 and 402%, respectively). Furthermore, the secretion of aldosterone and cortisol by NCI-H295R cells induced by FCCM was significantly inhibited by the Wnt-antagonist sFRP-1. These data indicate that the Wnt-signaling pathway is one of the mechanisms mediating the effects of fat cells on adrenal StAR transcription and aldosterone and cortisol secretion.

Construction of Wif1-IgG1/Fc Recombinant Vector and Characterization of Its Expression in CHO Cells.

Wnt signalling dysregulation has been implicated in cancers, including lymphoma. The Initiation of Wnt signalling modulated by soluble Wnt ant agonists, including soluble frizzled related proteins, dickkopf proteins, and Wnt inhibitory factor-1 (Wif1). These natural inhibitors can be used directly as theraputic reagents for cancers. But the recombinant antagonist only give very low blood levels, are cleared rapidly from the body (only several hours) and must be administered daily via subcutaneous injection. Therefore, development of new forms of Wnts inhibitors with prolonged circulating half-life is of significant interest. Human IgG immunoglobulins have longer circulating half-life (21 days in humans). When fused with a Wnt inhibitor, its dimeric structure further increases the effective size and circulating half-life. Thus administration of vector plasmid may be every 2~3 week. Moreover, IgG Fc can interact with FcR of CTL, NK, MΦ, and complements and the target cells can be killed through ADCC and CDCC. We constructed a Wif1-IgG1/Fc expressing vector and expressed it in Chinese hamster ovum cells in order to seek effective methods to inhibit lymphoma growth. Wif1 and IgG/Fc cDNAs were amplified by RT-PCR from human lymphocyte and cloned into the eukaryotic expression vector pcDNA3.0 by direct cloning and the resultant recombinant plasmid pcDNA Wif1-IgG1/Fc was transfected into 293 cells with lipofectmin. The constitutively expressing cells were obtained by G418 screening. Expression of the fusion protein was confirmed by Western blot, the fusion protein was purified with affinity chromatography, and its' biological activity was examined by flow cytometry, MTT colorimetry and ELISA. Our results show that the fusion protein significantly upregulated Wif1 density and promoted molt3 cell apoptosis, which was time dependent. The molt3 cell apoptosis induced by the fusion protein increased in the presence of NK cells or complements. Thus, we have successfully constructed and functionally expressed Wif1-IgG1/Fc fusion protein and shown that the purified fusion protein could kill molt3 cells through apoptosis and by ADCC and CDCC.

Aberrant methylation of the Wnt antagonist SFRP1 in breast cancer is associated with unfavourable prognosis

The canonical Wnt signalling pathway plays a key role during embryogenesis and defects in this pathway have been implicated in the pathogenesis of various types of tumours, including breast cancer. The gene for secreted frizzled-related protein 1 (SFRP1) encodes a soluble Wnt antagonist and is located in a chromosomal region (8p22-p12) that is often deleted in breast cancer. In colon, lung, bladder and ovarian cancer SFRP1 expression is frequently inactivated by promoter methylation. We have previously shown that loss of SFRP1 protein expression is a common event in breast tumours that is associated with poor overall survival in patients with early breast cancer. To investigate the cause of SFRP1 loss in breast cancer, we performed mutation, methylation and expression analysis in human primary breast tumours and breast cell lines. No SFRP1 gene mutations were detected. However, promoter methylation of SFRP1 was frequently observed in both primary breast cancer (61%, n=130) and cell lines analysed by methylation-specific polymerase chain reaction (MSP). We found a tight correlation (P<0.001) between methylation and loss of SFRP1 expression in primary breast cancer tissue. SFRP1 expression was restored after treatment of tumour cell lines with the demethylating agent 5-aza-2'-deoxycytidine. Most interestingly, SFRP1 promoter methylation was an independent factor for adverse patient survival in Kaplan-Meier analysis. Our results indicate that promoter hypermethylation is the predominant mechanism of SFRP1 gene silencing in human breast cancer and that SFRP1 gene inactivation in breast cancer is associated with unfavourable prognosis.

Expression of secreted Wnt antagonists in gastrointestinal tissues: potential role in stem cell homeostasis

Background: Wnt signalling dysregulation has been implicated in cancer, including colon and gastric cancer. Initiation of Wnt signalling is modulated by soluble Wnt antagonists (sWAs), including soluble frizzled related proteins,...

Myeloma Cells Suppress Osteoblast Differentiation by Secreting a Soluble Wnt Inhibitor, sFRP-2.

Multiple myeloma (MM), a malignancy of plasma cells, develops in the bone marrow, and generates devastating bone destruction. Along with enhanced bone resorption, clinical evidence has also suggested suppression of bone formation as a contributing factor to the bone loss in MM. In contrast to recent understanding on mechanisms of osteolysis enahnced in MM, little is known about factors responsible for impaired bone formation. A canonical Wingless-type (Wnt) signaling pathway has recently been shown to play a critical role in osteoblast differentiation. Therefore, in the present study, we aimed to clarify mechanisms of suppression of osteoblast differentiation by MM cells with a particular focus on a canonical Wnt signaling pathway. Because several secreted Frizzled related protein (sFRP) and DKK family members are known as soluble Wnt antagonists, we first examined the expression of sFRP-1, 2 and 3 and DKK-1 in MM cell lines including U266, RPMI8226 and ARH77. All cell lines expressed sFRP-2 and sFRP-3 mRNA observed by RT-PCR. However, sFRP-1 was not expressed in any cell line, and Dkk-1 was expressed only in U266 cells at mRNA levels. We next conducted Western blot analyses for these factors and detected only sFRP-2 in immunoprecipitants of conditioned media as well as cell lysates of all these cell lines. However, no other factors were found at protein levels. Furthermore, sFRP-2 mRNA and protein expression was detected in most MM cells from patients with advanced or terminal stages of MM with bone destruction including plasma cell leukemia (3/4 and 8/10, respectively). In order to examine a biological role for sFRP-2, we added recombinant sFRP-2 to MC3T3-E1 cell culture together with BMP-2. Exogenous sFRP-2 partially suppressed alkaline phosphatase activity but almost completely mineralized nodule formation enhanced by BMP-2. Furthermore, sFRP-2 immunodepletion significantly restored mineralized nodule formation in MC3T3-E1 cells suppressed by RPMI8226 and ARH77 CM. These results suggest that sFRP-2 alone is able to suppress osteoblast differentiation induced by BMP-2 and that MM cell-derived sFRP-2 is among predominant factors responsible for defective bone formation in MM. Because MM cell-derived factors such as DKK-1, IGF-BP4 and IL-3 other than sFRP-2 have been implicated as an inhibitor of osteoblast differentiation, sFRP-2 may act alone or in combination with such other factors to potently suppress bone formation in MM. Taken together, MM cells may cause an imbalance of bone turnover with enhanced osteoclastic bone resorption and concomitantly suppressed bone formation, which leads to devastating destruction and a rapid loss of bone.

A Wnt- and beta -catenin-dependent pathway for mammalian cardiac myogenesis.

Acquisition of a cardiac fate by embryonic mesodermal cells is a fundamental step in heart formation. Heart development in frogs and avians requires positive signals from adjacent endoderm, including bone morphogenic proteins, and is antagonized by a second secreted signal, Wnt proteins, from neural tube. By contrast, mechanisms of mesodermal commitment to create heart muscle in mammals are largely unknown. In addition, Wnt-dependent signals can involve either a canonical beta-catenin pathway or other, alternative mediators. Here, we tested the involvement of Wnts and beta-catenin in mammalian cardiac myogenesis by using a pluripotent mouse cell line (P19CL6) that recapitulates early steps for cardiac specification. In this system, early and late cardiac genes are up-regulated by 1% DMSO, and spontaneous beating occurs. Notably, Wnt3A and Wnt8A were induced days before even the earliest cardiogenic transcription factors. DMSO induced biochemical mediators of Wnt signaling (decreased phosphorylation and increased levels of beta-catenin), which were suppressed by Frizzled-8Fc, a soluble Wnt antagonist. DMSO provoked T cell factor-dependent transcriptional activity; thus, induction of Wnt proteins by DMSO was functionally coupled. Frizzled-8Fc inhibited the induction of cardiogenic transcription factors, cardiogenic growth factors, and sarcomeric myosin heavy chains. Likewise, differentiation was blocked by constitutively active glycogen synthase kinase 3beta, an intracellular inhibitor of the Wntbeta-catenin pathway. Conversely, lithium chloride, which inhibits glycogen synthase kinase 3beta, and Wnt3A-conditioned medium up-regulated early cardiac markers and the proportion of differentiated cells. Thus, Wntbeta-catenin signaling is activated at the inception of mammalian cardiac myogenesis and is indispensable for cardiac differentiation, at least in this pluripotent model system.

Transplacental delivery of the Wnt antagonist Frzb1 inhibits development of caudal paraxial mesoderm and skeletal myogenesis in mouse embryos.

Axial structures (neural tube/notochord) and surface ectoderm activate myogenesis in the mouse embryo; their action can be reproduced, at least in part, by several molecules such as Sonic hedgehog and Wnts. Recently, soluble Wnt antagonists have been identified. Among those examined only Frzb1 was found to be expressed in the presomitic mesoderm and newly formed somites and thus its possible role in regulating myogenesis was investigated in detail. When presomitic mesoderm or newly formed somites were cultured with axial structures and surface ectoderm on a feeder layer of C3H10T1/2 cells expressing Frzb1, myogenesis was abolished or severely reduced in presomitic mesoderm and the three most recently formed somites. In contrast, no effect was observed on more mature somites. Inhibition of myogenesis did not appear to be associated with increased cell death since the final number of cells in the explants grown in the presence of Frzb1 was only slightly reduced in comparison with controls. In order to examine the possible function of Frzb1 in vivo, we developed a method based on the overexpression of the soluble antagonist by transient transfection of WOP cells with a Frzb1 expression vector and injection of transfected cells into the placenta of pregnant females before the onset of maternofoetal circulation. Frzb1, secreted by WOP cells, accumulated in the embryo and caused a marked reduction in size of caudal structures. Myogenesis was strongly reduced and, in the most severe cases, abolished. This was not due to a generalized toxic effect since only several genes downstream of the Wnt signaling pathway such as En1, Noggin and Myf5 were downregulated; in contrast, Pax3 and Mox1 expression levels were not affected even in embryos exhibiting the most severe phenotypes. Taken together, these results suggest that Wnt signals may act by regulating both myogenic commitment and expansion of committed cells in the mouse mesoderm.