Purification and molecular cloning of a secreted, Frizzled-related antagonist of Wnt action

Dual role of Sfrp4 in bone remodelling during orthodontic tooth movement

OBJECTIVES

The objective of this study was to determine changes in gene expression by establishing an orthodontic tooth movement (OTM) rat model with appropriate and excessive orthodontic force.

MATERIALS AND METHODS

Using a closed coil nickel-titanium spring, the OTM was carried out to apply a mesial force of 50 or 100 g to the maxillary first molars. Micro-CT, histological and immunohistochemical staining were used to evaluate the bone formation at the tension site and the bone resorption and bone formation at pressure site. Then RNA sequencing and bioinformatic analysis were performed.

RESULTS

According to the results of the Mirco-CT scan of OTM rat models, both the 50 g group and the 100 g group showed variable degrees of reduction in alveolar bone density on the tension and pressure sides. The results of histological and immunohistochemical staining demonstrated that the periodontal tissue and osteogenic ability of the 50 g group were restored at the 14 days, while the 100 g group caused severe periodontal tissue damage. The GO and KEGG analysis results, as well as the number of differentially expressed genes (DEGs), varied depending on the loading time and value of appliance, according to the results of the RNA sequencing. And the immunohistochemical staining results showed that Sfrp4 functioned by efficiently influencing both bone formation and bone absorption.

CONCLUSIONS

Appropriate orthodontic force value could cause appropriate movement of teeth in rats without adverse periodontal damage. Simultaneously, distinct gene expression patterns were observed at various force levels and time intervals.

Wnt/β-catenin signalling underpins juvenile Fasciola hepatica growth and development

Infection by the liver fluke, Fasciola hepatica, places a substantial burden on the global agri-food industry and poses a significant threat to human health in endemic regions. Widespread resistance to a limited arsenal of chemotherapeutics, including the frontline flukicide triclabendazole (TCBZ), renders F. hepatica control unsustainable and accentuates the need for novel therapeutic target discovery. A key facet of F. hepatica biology is a population of specialised stem cells which drive growth and development - their dysregulation is hypothesised to represent an appealing avenue for control. The exploitation of this system as a therapeutic target is impeded by a lack of understanding of the molecular mechanisms underpinning F. hepatica growth and development. Wnt signalling pathways govern a myriad of stem cell processes during embryogenesis and drive tumorigenesis in adult tissues in animals. Here, we identify five putative Wnt ligands and five Frizzled receptors in liver fluke transcriptomic datasets and find that Wnt/β-catenin signalling is most active in juveniles, the most pathogenic life stage. FISH-mediated transcript localisation revealed partitioning of the five Wnt ligands, with each displaying a distinct expression pattern, consistent with each Wnt regulating the development of different cell/tissue types. The silencing of each individual Wnt or Frizzled gene yielded significant reductions in juvenile worm growth and, in select cases, blunted the proliferation of neoblast-like cells. Notably, silencing FhCTNNB1, the key effector of the Wnt/β-catenin signal cascade led to aberrant development of the neuromuscular system which ultimately proved lethal - the first report of a lethal RNAi-induced phenotype in F. hepatica. The absence of any discernible phenotypes following the silencing of the inhibitory Wnt/β-catenin destruction complex components is consistent with low destruction complex activity in rapidly developing juvenile worms, corroborates transcriptomic expression profiles and underscores the importance of Wnt signalling as a key molecular driver of growth and development in early-stage juvenile fluke. The putative pharmacological inhibition of Wnt/β-catenin signalling using commercially available inhibitors phenocopied RNAi results and provides impetus for drug repurposing. Taken together, these data functionally and chemically validate the targeting of Wnt signalling as a novel strategy to undermine the pathogenicity of juvenile F. hepatica.

Tumor endothelial cell-derived Sfrp1 supports the maintenance of cancer stem cells via Wnt signaling

Cancer stem cells (CSCs), which are critical targets for cancer therapy as they are involved in drug resistance to anticancer drugs, and metastasis, are maintained by angiocrine factors produced by particular niches that form within tumor tissue. Secreted frizzled-related protein 1 (Sfrp1) is an extracellular protein that modulates Wnt signaling. However, the cells that produce Sfrp1 in the tumor environment and its function remain unclear. We aimed to elucidate angiocrine factors related to CSC maintenance, focusing on Sfrp1. Although Sfrp1 is a Wnt pathway-related factor, its impact on tumor tissues remains unknown. We investigated the localization of Sfrp1 in tumors and found that it is expressed in some tumor vessels. Analysis of mice lacking Sfrp1 showed that tumor growth was suppressed in Sfrp1-deficient tumor tissues. Flow cytometry analysis indicated that CSCs were maintained in the early tumor growth phase in the Sfrp1 knockout (KO) mouse model of tumor-bearing cancer. However, tumor growth was inhibited in the late tumor growth phase because of the inability to maintain CSCs. Real-time PCR results from tumors of Sfrp1 KO mice showed that the expression of Wnt signaling target genes significantly decreased in the late stage of tumor growth. This suggests that Sfrp1, an angiocrine factor produced by the tumor vascular niche, is involved in Wnt signaling-mediated mechanisms in tumor tissues.

Why Is Wnt/β-Catenin Not Yet Targeted in Routine Cancer Care?

Despite significant progress in cancer prevention, screening, and treatment, the still limited number of therapeutic options is an obstacle towards increasing the cancer cure rate. In recent years, many efforts were put forth to develop therapeutics that selectively target different components of the oncogenic Wnt/β-catenin signaling pathway. These include small molecule inhibitors, antibodies, and more recently, gene-based approaches. Although some of them showed promising outcomes in clinical trials, the Wnt/β-catenin pathway is still not targeted in routine clinical practice for cancer management. As for most anticancer treatments, a critical limitation to the use of Wnt/β-catenin inhibitors is their therapeutic index, i.e., the difficulty of combining effective anticancer activity with acceptable toxicity. Protecting healthy tissues from the effects of Wnt/β-catenin inhibitors is a major issue due to the vital role of the Wnt/β-catenin signaling pathway in adult tissue homeostasis and regeneration. In this review, we provide an up-to-date summary of clinical trials on Wnt/β-catenin pathway inhibitors, examine their anti-tumor activity and associated adverse events, and explore strategies under development to improve the benefit/risk profile of this therapeutic approach.

New insights in ubiquitin-dependent Wnt receptor regulation in tumorigenesis

Wnt signaling plays a crucial role in embryonic development and homeostasis maintenance. Delicate and sensitive fine-tuning of Wnt signaling based on the proper timings and positions is required to balance cell proliferation and differentiation and maintain individual health. Therefore, homeostasis is broken by tissue hypoplasia or tumor formation once Wnt signal dysregulation disturbs the balance of cell proliferation. The well-known regulatory mechanism of Wnt signaling is the molecular reaction associated with the cytoplasmic accumulation of effector β-catenin. In addition to β-catenin, most Wnt effector proteins are also regulated by ubiquitin-dependent modification, both qualitatively and quantitatively. This review will explain the regulation of the whole Wnt signal in four regulatory phases, as well as the different ubiquitin ligases and the function of deubiquitinating enzymes in each phase. Along with the recent results, the mechanism by which RNF43 negatively regulates the surface expression of Wnt receptors, which has recently been well understood, will be detailed. Many RNF43 mutations have been identified in pancreatic and gastrointestinal cancers and examined for their functional alteration in Wnt signaling. Several mutations facilitate or activate the Wnt signal, reversing the RNF43 tumor suppressor function into an oncogene. RNF43 may simultaneously play different roles in classical multistep tumorigenesis, as both wild-type and mutant RNF43 suppress the p53 pathway. We hope that the knowledge obtained from further research in RNF43 will be applied to cancer treatment in the future despite the fully unclear function of RNF43.

The Intricacies of Renal Phosphate Reabsorption-An Overview

To maintain an optimal body content of phosphorus throughout postnatal life, variable phosphate absorption from food must be finely matched with urinary excretion. This amazing feat is accomplished through synchronised phosphate transport by myriads of ciliated cells lining the renal proximal tubules. These respond in real time to changes in phosphate and composition of the renal filtrate and to hormonal instructions. How they do this has stimulated decades of research. New analytical techniques, coupled with incredible advances in computer technology, have opened new avenues for investigation at a sub-cellular level. There has been a surge of research into different aspects of the process. These have verified long-held beliefs and are also dramatically extending our vision of the intense, integrated, intracellular activity which mediates phosphate absorption. Already, some have indicated new approaches for pharmacological intervention to regulate phosphate in common conditions, including chronic renal failure and osteoporosis, as well as rare inherited biochemical disorders. It is a rapidly evolving field. The aim here is to provide an overview of our current knowledge, to show where it is leading, and where there are uncertainties. Hopefully, this will raise questions and stimulate new ideas for further research.

Proteomic detection of COX-2 pathway-related factors in patients with adenomyosis

Background

Investigating the relationship between cyclooxygenase-2 (COX-2) pathway-related factors and clinical features in patients with adenomyosis by proteomics could provide potential therapeutic targets.

Methods

This study recruited 40 patients undergoing surgical hysterectomy and pathological diagnosis of adenomyosis, collected ectopic endometrial specimens, and recorded clinical data. The expression levels of COX-2 in ectopic uterus lesions were detected using the immunohistochemical (IHC) SP method. The 40 samples were then divided into a COX-2 low or high expression group. Five samples with the most typical expression levels were selected from each of the two groups and the differential proteins between the two groups were identified using label-free quantitative proteomics. WW domain-binding protein 2 (WBP2), interferon induced transmembrane protein 3 (IFITM3), and secreted frizzled-related protein 4 (SFRP4) were selected for further verification, and their relationships with COX-2 and clinical characteristics were analyzed.

Results

There were statistically significant differences in the expression of WBP2, IFITM3, and SFRP4 between the COX-2 low and high expression groups (P < 0.01). The expressions of COX-2, IFITM3, and SFRP4 were significantly correlated with dysmenorrhea between the two groups (P < 0.05), but not with uterine size or menstrual volume (P > 0.05). However, there was no significant correlation between the expression of WBP2 and dysmenorrhea, uterine size, and menstruation volume in both the high expression and low expression groups (P > 0.05).

Conclusions

COX-2, IFITM3, SFRP4, and WBP2 may be involved in the pathogenesis of adenomyosis. COX-2, IFITM3, and SFRP4 may serve as potential molecular biomarkers or therapeutic targets in dysmenorrhea in patients with early adenomyosis.

Ischemia-reperfusion injury: molecular mechanisms and therapeutic targets

Ischemia-reperfusion (I/R) injury paradoxically occurs during reperfusion following ischemia, exacerbating the initial tissue damage. The limited understanding of the intricate mechanisms underlying I/R injury hinders the development of effective therapeutic interventions. The Wnt signaling pathway exhibits extensive crosstalk with various other pathways, forming a network system of signaling pathways involved in I/R injury. This review article elucidates the underlying mechanisms involved in Wnt signaling, as well as the complex interplay between Wnt and other pathways, including Notch, phosphatidylinositol 3-kinase/protein kinase B, transforming growth factor-β, nuclear factor kappa, bone morphogenetic protein, N-methyl-D-aspartic acid receptor-Ca2+-Activin A, Hippo-Yes-associated protein, toll-like receptor 4/toll-interleukine-1 receptor domain-containing adapter-inducing interferon-β, and hepatocyte growth factor/mesenchymal-epithelial transition factor. In particular, we delve into their respective contributions to key pathological processes, including apoptosis, the inflammatory response, oxidative stress, extracellular matrix remodeling, angiogenesis, cell hypertrophy, fibrosis, ferroptosis, neurogenesis, and blood-brain barrier damage during I/R injury. Our comprehensive analysis of the mechanisms involved in Wnt signaling during I/R reveals that activation of the canonical Wnt pathway promotes organ recovery, while activation of the non-canonical Wnt pathways exacerbates injury. Moreover, we explore novel therapeutic approaches based on these mechanistic findings, incorporating evidence from animal experiments, current standards, and clinical trials. The objective of this review is to provide deeper insights into the roles of Wnt and its crosstalk signaling pathways in I/R-mediated processes and organ dysfunction, to facilitate the development of innovative therapeutic agents for I/R injury.

Regulation of otic neurosensory specification by Notch and Wnt signalling: insights from RNA-seq screenings in the embryonic chicken inner ear

The Notch and Wnt signalling pathways play key roles in the formation of inner ear sensory organs, but little is known about their transcriptional effectors and targets in this context. Here, we perturbed Notch and Wnt activities in the embryonic chicken otic vesicle using pharmacological treatment or in ovo electroporation of plasmid DNA, and used RNA-Seq to analyse the resulting changes in gene expression. Compared to pharmacological treatments, in ovo electroporation changed the expression of fewer genes, a likely consequence of the variability and mosaicism of transfection. The pharmacological inhibition of Notch activity induced a rapid change in the expression of known effectors of this pathway and genes associated with neurogenesis, consistent with a switch towards an otic neurosensory fate. The Wnt datasets contained many genes associated with a neurosensory biological function, confirming the importance of this pathway for neurosensory specification in the otocyst. Finally, the results of a preliminary gain-of-function screening of selected transcription factors and Wnt signalling components suggest that the endogenous programs of otic neurosensory specification are very robust, and in general unaffected by the overexpression of a single factor. Altogether this work provides new insights into the effectors and candidate targets of the Notch and Wnt pathways in the early developing inner ear and could serve as a useful reference for future functional genomics experiments in the embryonic avian inner ear.

Secreted frizzled-related proteins: A promising therapeutic target for cancer therapy through Wnt signaling inhibition

The Wnt signaling system is a critical pathway that regulates embryonic development and adult homeostasis. Secreted frizzled-related proteins (SFRPs) are extracellular inhibitors of Wnt signaling that act by binding directly to Wnt ligands or Frizzled receptors. SFRPs can act as anti-Wnt agents and suppress cancer growth by blocking the action of Wnt ligands. However, SFRPs are often silenced by promoter methylation in cancer cells, resulting in hyperactivation of the Wnt pathway. Epigenetic modifiers can reverse this silencing and restore SFRPs expression. Despite the potential of SFRPs as a therapeutic target, the effects of SFRPs on tumor development remain unclear. Therefore, a review of the expression of various members of the SFRPs family in different cancers and their potential as therapeutic targets is warranted. This review aims to summarize the current knowledge of SFRPs in cancer, focusing on their expression patterns and their potential as novel therapeutic targets.

Frizzled 7 modulates goblet and Paneth cell fate, and maintains homeostasis in mouse intestine

Intestinal homeostasis depends on interactions between the intestinal epithelium, the immune system and the microbiota. Because of these complicated connections, there are many problems that need to be solved. Current research has indicated that genes targeted by Wnt signaling are responsible for controlling intestinal stem cell fate and for modulating intestinal homeostasis. Our data show that loss of frizzled 7 (Fzd7), an important element in Wnt signaling, interrupts the differentiation of mouse intestinal stem cells into absorptive progenitors instead of secretory progenitors (precursors of goblet and Paneth cells). The alteration in canonical Wnt and Notch signaling pathways interrupts epithelial homeostasis, resulting in a decrease in physical protection in the intestine. Several phenotypes in our Fzd7-deleted model were similar to the features of enterocolitis, such as shortened intestines, decreased numbers of goblet cells and Paneth cells, and severe inflammation. Additionally, loss of Fzd7 exacerbated the defects in a chemical-induced colitis model and could initiate tumorigenesis. These findings may provide important information for the discovery of efficient therapeutic methods to treat enterocolitis and related cancers in the intestines.

The logistics of Wnt production and delivery

Wnts are secreted proteins that control stem cell maintenance, cell fate decisions, and growth during development and adult homeostasis. Wnts carry a post-translational modification not seen in any other secreted protein: during biosynthesis, they are appended with a palmitoleoyl moiety that is required for signaling but also impairs solubility and hence diffusion in the extracellular space. In some contexts, Wnts act only in a juxtacrine manner but there are also instances of long range action. Several proteins and processes ensure that active Wnts reach the appropriate target cells. Some, like Porcupine, Wntless, and Notum are dedicated to Wnt function; we describe their activities in molecular detail. We also outline how the cell infrastructure (secretory, endocytic, and retromer pathways) contribute to the progression of Wnts from production to delivery. We then address how Wnts spread in the extracellular space and form a signaling gradient despite carrying a hydrophobic moiety. We highlight particularly the role of lipid-binding Wnt interactors and heparan sulfate proteoglycans. Finally, we briefly discuss how evolution might have led to the emergence of this unusual signaling pathway.

Secreted frizzled-related protein 4 exerts anti-atherosclerotic effects by reducing inflammation and oxidative stress

Atherosclerosis and its sequelae, such as coronary artery disease (CAD), are the most common diseases worldwide and the leading causes of morbidity and mortality in most countries. Our previous studies have shown that circulating secreted frizzled-related protein 4 (SFRP4) levels are increased in patients with CAD. However, the role of SFRP4 in the development of atherosclerosis remains unclear; thus, the purpose of this study was to determine the effect of SFRP4 on high-fat diet (HFD)-induced atherosclerosis and explore the possible mechanisms. In this study, we found for the first time that administration of recombinant SFRP4 alleviates atherosclerosis in ApoE-/- mice by reducing inflammation and oxidative stress. In addition, the anti-atherosclerotic effect of SFRP4 was associated with inhibition of the Wnt/β-catenin signaling pathway, and Wnt1 overexpression abolished the anti-atherosclerotic effects of SFRP4. Taken together, our results highlight the potential beneficial effect of SFRP4 as a therapeutic agent for atherosclerosis and CAD.

The Wnt Pathway: From Signaling Mechanisms to Synthetic Modulators

The Wnt pathway is central to a host of developmental and disease-related processes. The remarkable conservation of this intercellular signaling cascade throughout metazoan lineages indicates that it coevolved with multicellularity to regulate the generation and spatial arrangement of distinct cell types. By regulating cell fate specification, mitotic activity, and cell polarity, Wnt signaling orchestrates development and tissue homeostasis, and its dysregulation is implicated in developmental defects, cancer, and degenerative disorders. We review advances in our understanding of this key pathway, from Wnt protein production and secretion to relay of the signal in the cytoplasm of the receiving cell. We discuss the evolutionary history of this pathway as well as endogenous and synthetic modulators of its activity. Finally, we highlight remaining gaps in our knowledge of Wnt signal transduction and avenues for future research. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Canonical Wnt Signaling in the Pathology of Iron Overload-Induced Oxidative Stress and Age-Related Diseases

Iron accumulates in the vital organs with aging. This is associated with oxidative stress, inflammation, and mitochondrial dysfunction leading to age-related disorders. Abnormal iron levels are linked to neurodegenerative diseases, liver injury, cancer, and ocular diseases. Canonical Wnt signaling is an evolutionarily conserved signaling pathway that regulates many cellular functions including cell proliferation, apoptosis, cell migration, and stem cell renewal. Recent evidences indicate that iron regulates Wnt signaling, and iron chelators like deferoxamine and deferasirox can inhibit Wnt signaling and cell growth. Canonical Wnt signaling is implicated in the pathogenesis of many diseases, and there are significant efforts ongoing to develop innovative therapies targeting the aberrant Wnt signaling. This review examines how intracellular iron accumulation regulates Wnt signaling in various tissues and their potential contribution in the progression of age-related diseases.

Downregulation of SFRP2 facilitates cancer stemness and radioresistance of glioma cells via activating Wnt/β-catenin signaling

Secreted frizzled-related protein 2 (SFRP2) is a glycoprotein with frizzled-like cysteine-rich domain that binds with Wnt ligands or frizzled receptors to regulate Wnt signaling. SFRP2 is frequently hypermethylated in glioma patients, and analysis of TCGA data indicates that SFRP2 is one of the most downregulated genes in radiotherapy treated glioma patients. In the present study, we aimed to explore the potential function of SFRP2 in tumorigenesis and radioresistance of glioma. The RNA sequencing data of TCGA glioma samples were downloaded and analyzed. SFRP2 expression in 166 glioma patients was evaluated by qRT-PCR. The potential functions of SFRP2 in glioma were evaluated by loss-of-function assays and gain-of-function assays in glioma cell lines. We found that SFRP2 was downregulated in radiotherapy-treated glioma patients, and low SFRP2 expression was correlated with advanced tumor stage and poor prognosis. CRISP/Cas9-meidated SFRP2 knockdown promoted soft agar colony formation, cancer stemness and radioresistance of glioma cells, while enforced SFRP2 expression exhibited opposite effects. Moreover, Wnt/β-catenin signaling was activated in radiotherapy treated glioma patients. SFRP2 knockdown activated Wnt/β-catenin signaling in glioma cell lines, while overexpression of SFRP2 inhibited Wnt/β-catenin activation. Besides, pharmacological inhibition of Wnt/β-catenin signaling by XAV-939 abrogated the effects of SFRP2 knockdown on cancer stemness and radioresistance of glioma cells. Our data for the first time demonstrated a role of SFRP2 in radioresistance of glioma cells, and suggested that inhibition of Wnt/β-catenin signaling might be a potential strategy for increasing radiosensitivity of glioma patients.

Roles of Therapeutic Bioactive Compounds in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is due to poor prognosis and lack of availability of effective treatment. Novel therapeutic strategies will be the fine tuning of intracellular ROS signaling to effectively deprive cells of ROS-induced tumor-promoting events. This review discusses the generation of ROS, the major signaling their modulation in therapeutics. We explore some of the major pathways involved in HCC, which include the VEGF, MAPK/ERK, mTOR, FGF, and Ser/Thr kinase pathways. In this review, we study cornerstone on natural bioactive compounds with their effect on hepatocarcinomas. Furthermore, we focus on oxidative stress and FDA-approved signaling pathway inhibitors, along with chemotherapy and radiotherapy enhancers which with early evidence of success. While more in vivo testing is required to confirm the findings presented here, our findings will aid future nonclinical, preclinical, and clinical studies with these compounds, as well as inspire medicinal chemistry scientists to conduct appropriate research on this promising natural compound and their derivatives.

Single-cell transcriptome analysis reveals defective decidua stromal niche attributes to recurrent spontaneous abortion

Objectives

Successful pregnancy involves the homeostasis between maternal decidua and fetoplacental units, whose disruption contributes to compromised pregnancy outcomes, including recurrent spontaneous abortion (RSA). The role of cell heterogeneity of maternal decidua in RSA is yet to be illustrated.

Materials and methods

A total of 66,078 single cells from decidua samples isolated from patients with RSA and healthy controls were analysed by unbiased single‐cell RNA sequencing (scRNA‐seq).

Results

Our scRNA‐seq results revealed that stromal cells are the most abundant cell type in decidua during early pregnancy. RSA samples are accompanied by aberrant decidualization and obviously obstructed communication between stromal cells and other cell types, such as abnormal activation of macrophages and NK cells. In addition, the over‐activated TNF superfamily member 12 (TNFSF12, TWEAK) and FASLG in RSA are closely related to stromal cell demise and pregnancy failure.

Conclusions

Our research reveals that the cell composition and communications in normal and RSA decidua at early pregnancy and provides insightful information for the pathology of RSA and will pave the way for pregnancy loss prevention.

The Role of the Wnt Pathway in VEGF/Anti-VEGF-Dependent Control of the Endothelial Cell Barrier

Purpose

Investigate the contribution of the Wnt pathway to vascular endothelial growth factor (VEGF)/anti-VEGF-mediated control of endothelial cell permeability.

Methods

High glucose-treated primary human retinal endothelial cells (HRECs) were exposed to either VEGF, or VEGF and then anti-VEGF. Changes in gene expression were assayed by RNAseq and qRT-PCR. Permeability was monitored by electrical cell-substrate impedance sensing (ECIS). Approaches to activate the Wnt pathway included treatment with LiCl and overexpression of constitutively activated β-catenin. β-catenin-dependent transcriptional activity was monitored in HRECs stably expressing a TCF/LEF-driven reporter.

Results

VEGF/anti-VEGF altered expression of genes encoding many members of the Wnt pathway. A subset of these genes was regulated in a way that is likely to contribute to control of the endothelial cell barrier. Namely, the VEGF-induced alteration of expression of such genes was reversed by anti-VEGF, and such adjustments occurred at times corresponding to changes in barrier function. While pharmacological and molecular approaches to activate the Wnt pathway had no effect on basal permeability, they suppressed VEGF-induced relaxation. Furthermore, anti-VEGF-mediated restoration of barrier function was unaffected by activation of the Wnt pathway.

Conclusions

VEGF/anti-VEGF engages multiple members of the Wnt pathway, and activating this pathway enforces the endothelial barrier by attenuating VEGF-induced relaxation. These data suggest that FDA-approved agents such as LiCl may be an adjuvant to anti-VEGF therapy for patients afflicted with blinding conditions including diabetic retinopathy.

Wingless-type mouse mammary tumor virus integration site regulation of bovine theca cells

Ovarian paracrine mediation by components of the wingless-type mouse mammary tumor virus integration site ligands (WNT1 to 11) and their receptors, frizzled family members (FZD1 to 10), has been proposed. Secreted truncated forms of FZD proteins (e.g., secreted frizzled-related protein 4 [SFRP4]) block the action of WNT ligands. Dickkopf-1 (DKK1) is another WNT antagonist, and R-spondin-1 (RSPO1) is one of a group of four secreted proteins that enhance WNT/β-catenin signaling. Our hypothesis was that granulosa cells signal theca cells (TCs) via SFRP4, DKK1, RSPO1, and WNT secretion to regulate TC differentiation and proliferation. Therefore, in vitro experiments were conducted to study the effects of WNT family member 3A (WNT3A), WNT5A, RSPO1, DKK1, insulin-like growth factor 1 (IGF1), bone morphogenetic protein 7 (BMP7), Indian hedgehog (IHH), and fibroblast growth factor 9 (FGF9) on bovine TC proliferation and steroidogenesis. TCs of large (8 to 20 mm) and small (3 to 6 mm) follicles were collected from bovine ovaries; TC monolayers were established in vitro and treated with various doses of recombinant human WNT3A, WNT5A, RSPO1, DKK1, IGF1, FGF9, BMP7, IHH, and/or ovine luteinizing hormone (LH) in serum-free medium for 48 h. In experiment 1, using LH-treated TC, IGF1, IHH, and WNT3A increased (P < 0.05) cell numbers and androstenedione production, whereas WNT3A and BMP7 inhibited (P < 0.05) progesterone production. In experiment 2, FGF9 blocked (P < 0.05) the WNT3A-induced increase in androstenedione production in LH plus IGF1-treated TC. In experiment 3, RSPO1 further increased (P < 0.05) LH plus IGF1-induced progesterone and androstenedione production. In experiment 4, SFRP4 and DKK1 alone had no significant effect on TC proliferation or progesterone production of large-follicle TC but both blocked the inhibitory effect of WNT5A on androstenedione production. In contrast, DKK1 alone inhibited (P < 0.05) small-follicle TC androstenedione production whereas SFRP4 was without effect. We conclude that the ovarian TC WNT system is functional in cattle, with WNT3A increasing proliferation and androstenedione production of TC.

Genome-wide CNV investigation suggests a role for cadherin, Wnt, and p53 pathways in primary open-angle glaucoma

BACKGROUND

To investigate whether copy number variations (CNVs) are implicated in molecular mechanisms underlying primary open-angle glaucoma (POAG), we used genotype data of POAG individuals and healthy controls from two case-control studies, AGS (n = 278) and GLGS-UGLI (n = 1292). PennCNV, QuantiSNP, and cnvPartition programs were used to detect CNV. Stringent quality controls at both sample and marker levels were applied. The identified CNVs were intersected in CNV region (CNVR). After, we performed burden analysis, CNV-genome-wide association analysis, gene set overrepresentation and pathway analysis. In addition, in human eye tissues we assessed the expression of the genes lying within significant CNVRs.

RESULTS

We reported a statistically significant greater burden of CNVs in POAG cases compared to controls (p-value = 0,007). In common between the two cohorts, CNV-association analysis identified statistically significant CNVRs associated with POAG that span 11 genes (APC, BRCA2, COL3A1, HLA-DRB1, HLA-DRB5, HLA-DRB6, MFSD8, NIPBL, SCN1A, SDHB, and ZDHHC11). Functional annotation and pathway analysis suggested the involvement of cadherin, Wnt signalling, and p53 pathways.

CONCLUSIONS

Our data suggest that CNVs may have a role in the susceptibility of POAG and they can reveal more information on the mechanism behind this disease. Additional genetic and functional studies are warranted to ascertain the contribution of CNVs in POAG.

WNT3A rs752107(C > T) Polymorphism Is Associated With an Increased Risk of Essential Hypertension and Related Cardiovascular Diseases

Essential Hypertension (EH) results in the burden of cardiovascular disease (CVD) such as Heart Failure (HF) and Ischemic Stroke (IS). A rapidly emerging field involving the role of Wnt/β-catenin signaling pathway in cardiovascular development and dysfunction has recently drawn extensive attention. In the present study, we conducted a genetic association between genomic variants in Wnt/β-catenin signaling pathway and EH, HF, IS. A total of 95 SNPs in 12 Wnt signaling genes (WNT3A, WNT3, WNT4, DKK1, DKK2, LRP5, LRP6, CTNNB1, APC, FZD1, FRZB, SFRP1) were genotyped in 1,860 participants (440 patients with EH, 535 patients with HF, 421 patients with IS and 464 normal control subjects) using Sequenom MassArray technology. WNT3A rs752107(C > T) was strongly associated with an increased risk of EH, HF and IS. Compared with WNT3A rs752107 CC genotype, the CT genotype carriers had a 48% increased risk of EH (OR = 1.48, 95% CI = 1.12-1.96, P = 0.006), the TT genotype conferred a 139% increased risk of EH (OR = 2.39, 95% CI = 1.32-4.34, P = 0.003). Regarding HF and IS, the risk of HF in the T allele carriers (CT + TT) was nearly increased by 58% (OR = 1.58, 95% CI = 1.22-2.04, P = 4.40 × 10^-4) and the risk of IS was increased by 37% (OR = 1.37, 95% CI = 1.04-1.79, P = 0.025). Expression quantitative trait loci (eQTL) analysis indicated that rs752107 C allele corresponded to a significant reduction of WNT3A expression. We described a genetic variant of WNT3A rs752107 in Wnt/β-catenin signaling strongly associated with the risk of EH, HF and IS for the first time.

Beta-catenin activation and immunotherapy resistance in hepatocellular carcinoma: mechanisms and biomarkers

Mutations involving CTNNB1, the gene encoding beta-catenin, and other molecular alterations that affect the Wnt/beta-catenin signaling pathway are exceptionally common in hepatocellular carcinoma. Several of these alterations have also been associated with scarcity of immune cells in the tumor microenvironment and poor clinical response to immune checkpoint inhibitor therapy. In light of these associations, tumor biomarkers of beta-catenin status could have the potential to serve as clinical predictors of immunotherapy outcome. This editorial review article summarizes recent pre-clinical and clinical research pertaining to associations between beta-catenin activation and diminished anti-tumor immunity. Potential non-invasive biomarkers that may provide a window into this oncogenic mechanism of immune evasion are also presented and discussed.

Breast Cancer and Microcalcifications: An Osteoimmunological Disorder?

The presence of microcalcifications in the breast microenvironment, combined with the growing evidences of the possible presence of osteoblast-like or osteoclast-like cells in the breast, suggest the existence of active processes of calcification in the breast tissue during a woman’s life. Furthermore, much evidence that osteoimmunological disorders, such as osteoarthritis, rheumatoid arthritis, or periodontitis influence the risk of developing breast cancer in women exists and vice versa. Antiresorptive drugs benefits on breast cancer incidence and progression have been reported in the past decades. More recently, biological agents targeting pro-inflammatory cytokines used against rheumatoid arthritis also demonstrated benefits against breast cancer cell lines proliferation, viability, and migratory abilities, both in vitro and in vivo in xenografted mice. Hence, it is tempting to hypothesize that breast carcinogenesis should be considered as a potential osteoimmunological disorder. In this review, we compare microenvironments and molecular characteristics in the most frequent osteoimmunological disorders with major events occurring in a woman’s breast during her lifetime. We also highlight what the use of bone anabolic drugs, antiresorptive, and biological agents targeting pro-inflammatory cytokines against breast cancer can teach us.

Secreted frizzled-related protein 2: a key player in noncanonical Wnt signaling and tumor angiogenesis

Secreted frizzled-related proteins (SFRP) are glycoproteins containing a so-called frizzled-like cysteine-rich domain. This domain enables them to bind to Wnt ligands or frizzled (FzD) receptors, making potent regulators of Wnt signaling. As Wnt signaling is often altered in cancer, it is not surprising that Wnt regulators such as SFRP proteins are often differentially expressed in the tumor microenvironment, both in a metastatic and non-metastatic setting. Indeed, SFRP2 is shown to be specifically upregulated in the tumor vasculature of several types of cancer. Several studies investigated the functional role of SFRP2 in the tumor vasculature, showing that SFRP2 binds to FzD receptors on the surface of tumor endothelial cells. This activates downstream Wnt signaling and which is, thereby, stimulating angiogenesis. Interestingly, not the well-known canonical Wnt signaling pathway, but the noncanonical Wnt/Ca²⁺ pathway seems to be a key player in this event. In tumor models, the pro-angiogenic effect of SFRP2 could be counteracted by antibodies targeting SFRP2, without the occurrence of toxicity. Since tumor angiogenesis is an important process in tumorigenesis and metastasis formation, specific tumor endothelial markers such as SFRP2 show great promise as targets for anti-cancer therapies. This review discusses the role of SFRP2 in noncanonical Wnt signaling and tumor angiogenesis, and highlights its potential as anti-angiogenic therapeutic target in cancer.

Secreted Frizzled-Related Protein 1 as a Biomarker against Incomplete Age-Related Lobular Involution and Microcalcifications' Development

As a downregulator of the Wnt signaling pathway, SFRP1 is involved in several components of the age-related lobular involution process such as inflammation, apoptosis, and adipogenesis. Because microcalcifications are associated with inflammation, we aimed to demystify the cross talk between SFRP1, inflammatory markers, and microcalcifications by assessing SFRP1 expression (immunohistochemistry) in a cohort of 162 women with different degrees of lobular involution. SFRP1 expression was inversely associated with the degree of lobular involution (OR = 0.84; p-value < 0.01). SFRP1 expression, age at mastectomy, and waist circumference taken together predicted the degree of lobular involution (AUC = 78.1). This predictive model was best in patients with microcalcifications (AUC = 81.1) and in parous women (AUC = 87.8). SFRP1 expression was correlated with leptin (rho = 0.32), TNF-α (rho = 0.21), and IL-6 (rho = 0.21) expression by epithelial cells (all p-values <0.001). SFRP1 expression was lower in nulliparous women with involuted breast tissue compared with parous women with involuted breast tissue (Δmean = -2.31; p-value < 0.01) and was higher in nulliparous women with microcalcifications compared with nulliparous women without microcalcifications (Δmean = 2.4; p-value < 0.05). In this study, we highlighted two SFRP1-based predictive models for incomplete lobular involution and the development of microcalcifications and identified two distinct inflammatory profiles associated with age-related lobular involution in parous and nulliparous women.

Uncovering the potential differentially expressed miRNAs as diagnostic biomarkers for hepatocellular carcinoma based on machine learning in The Cancer Genome Atlas database

The present study aimed to identify novel diagnostic differentially expressed microRNAs (miRNAs/miRs) in order to understand the molecular mechanisms underlying hepatocellular carcinoma. The expression data of miRNA and mRNA were downloaded for differential expression analysis. Optimal diagnostic differentially expressed miRNA biomarkers were identified via a random forest algorithm. Classification models were established to distinguish patients with hepatocellular carcinoma and normal individuals. A regulatory network between optimal diagnostic differentially expressed miRNA and differentially expressed mRNAs was then constructed. The GSE63046 dataset and in vitro experiments were used to validate the expression of the optimal diagnostic differentially expressed miRNAs identified. In addition, diagnostic and prognostic analyses of optimal diagnostic differentially expressed miRNAs were performed. In total, 14 differentially expressed miRNAs (all upregulated) and 2,982 differentially expressed mRNAs (1,989 upregulated and 993 downregulated) were identified. hsa-miR-10b-5p, hsa-miR-10b-3p, hsa-miR-224-5p, hsa-miR-183-5p and hsa-miR-182-5p were considered as the optimal diagnostic biomarkers for hepatocellular carcinoma. The mRNAs targeted by these five miRNAs included secreted frizzled related protein 1 (SFRP1), endothelin receptor type B (EDNRB), nuclear receptor subfamily 4 group A member 3 (NR4A3), four and a half LIM domains 2 (FHL2), NK3 homeobox 1 (NKX3-1), interleukin 6 signal transducer (IL6ST) and forkhead box O1 (FOXO1). ‘Bile acid biosynthesis and cholesterol’ was the most enriched signaling pathways of these target mRNAs. The expression validation of the five miRNAs was consistent with the present bioinformatics analysis. Notably, hsa-miR-10b-5p and hsa-miR-10b-3p had a significant prognosis value for patients with hepatocellular carcinoma. In conclusion, the five differentially expressed miRNAs may be considered as diagnostic biomarkers for patients with hepatocellular carcinoma. In addition, the differential expression levels of the targets of these five mRNAs, including SFRP1, EDNRB, NR4A3, FHL2, NKX3−1, IL6ST and FOXO1, may be involved in hepatocellular carcinoma tumorigenesis.

Role of Secreted Frizzled-Related Protein 1 in Early Mammary Gland Tumorigenesis and Its Regulation in Breast Microenvironment

In mice, the lack of secreted frizzled-related protein 1 (SFRP1) is responsible for mammogenesis and hyperplasia, while, in bovines, its overexpression is associated with post-lactational mammary gland involution. Interestingly, there are no reports dealing with the role of SFRP1 in female involution. However, SFRP1 dysregulation is largely associated with human tumorigenesis in the literature. Indeed, the lack of SFRP1 is associated with both tumor development and patient prognosis. Considering the increased risk of breast tumor development associated with incomplete mammary gland involution, it is crucial to demystify the "grey zone" between physiological age-related involution and tumorigenesis. In this review, we explore the functions of SFRP1 involved in the breast involution processes to understand the perturbations driven by the disappearance of SFRP1 in mammary tissue. Moreover, we question the presence of recurrent microcalcifications identified by mammography. In bone metastases from prostate primary tumor, overexpression of SFRP1 results in an osteolytic response of the tumor cells. Hence, we explore the hypothesis of an osteoblastic differentiation of mammary cells induced by the lack of SFRP1 during lobular involution, resulting in a new accumulation of hydroxyapatite crystals in the breast tissue.

SFRP4 expression correlates with epithelial mesenchymal transition-linked genes and poor overall survival in colon cancer patients

BACKGROUND

Colon cancer is among the most commonly diagnosed cancers in the United States with an estimated 97220 new cases expected by the end of 2018. It affects 1.2 million people around the world and is responsible for about 0.6 million deaths every year. Despite decline in overall incidence and mortality over the past 30 years, there continues to be an alarming rise in early-onset colon cancer cases (< 50 years). Patients are often diagnosed at late stages of the disease and tend to have poor survival. We previously showed that the WNT “gatekeeper” gene, secreted frizzled-related protein 4 (SFRP4), is over-expressed in early-onset colon cancer. SFRP4 is speculated to play an essential role in cancer by inhibiting the epithelial mesenchymal transition (EMT).

AIM

To investigate the correlation between SFRP4 expression and EMT-linked genes in colon cancer and how it affects patient survival.

METHODS

SFRP4 expression relative to that of EMT-linked genes and survival analysis were performed using the University of California Santa Cruz Cancer Browser interface.

RESULTS

SFRP4 was found to be co-expressed with the EMT-linked markers CDH2, FN1, VIM, TWIST1, TWIST2, SNAI1, SNAI2, ZEB1, ZEB2, POSTN, MMP2, MMP7, MMP9, and COL1A1. SFRP4 expression negatively correlated with the EMT-linked suppressors CLDN4, CLDN7, TJP3, MUC1, and CDH1. The expression of SFRP4 and the EMT-linked markers was higher in mesenchymal-like samples compared to epithelial-like samples which potentially implicates SFRP4-EMT mechanism in colon cancer. Additionally, patients overexpressing SFRP4 presented with poor overall survival (P = 0.0293).

CONCLUSION

Considering the implication of SFRP4 in early-onset colon cancer, particularly in the context of EMT, tumor metastasis, and invasion, and the effect of increased expression on colon cancer patient survival, SFRP4 might be a potential biomarker for early-onset colon cancer that could be targeted for diagnosis and/or disease therapy.

SFRP4 Is a Negative Regulator of Ovarian Follicle Development and Female Fertility

WNT signaling regulates a variety of ovarian processes, including follicle development, granulosa cell (GC) proliferation and differentiation, steroidogenesis, and ovulation. The secreted frizzled-related proteins (SFRPs) comprise a family of WNT signaling antagonists. Sfrp4 expression was previously reported to be induced in ovarian GCs and cumulus cells in vivo following human chorionic gonadotropin treatment, suggesting that it may play key roles in cumulus expansion, ovulation/luteinization, and corpus luteum (CL) function. In this study, we aimed to define the physiological roles of Sfrp4 in the ovary by gene targeting. Sfrp4-null female mice were found to produce larger litters than did their wild-type littermates. Although previous studies had suggested roles of Sfrp4 in luteal cell survival, no differences in CL formation, morphology, steroidogenesis, involution, or luteal cell apoptosis were found in Sfrp4-null mice. Likewise, cumulus expansion occurred normally in Sfrp4-null mice, with minimal changes in cumulus cell gene expression. Hyperfertility in the Sfrp4-null model was ultimately attributed to decreased antral follicle atresia, leading to an enhanced ovulatory rate. Increased expression of FSH- and LH-responsive genes was found in GCs from Sfrp4-null mice, and GCs isolated from Sfrp4-null mice were found to be hyperresponsive to FSH and LH in vitro. Although Sfrp2 was found to be overexpressed in the GCs of Sfrp4-null mice (suggesting a compensatory mechanism), Sfrp2-null mice had normal fertility and ovulatory rates, and Sfrp2/4 double knockout mice did not differ from Sfrp4-null mice. Taken together, our results suggest that SFRP4 acts to attenuate GC responsiveness to gonadotropins, thereby decreasing follicle survival, ovulatory rate, and fertility.

Identification and integrated analysis of key differentially expressed circular RNAs in ER-positive subtype breast cancer

Aim: To systematically profile and characterize the circular RNA (circRNA) expression pattern in estrogen receptor (ER)-positive breast cancer (BC). Materials & methods: CircRNA expression profile was performed in ER-positive BC and adjacent nontumor tissues. The differentially expressed circRNAs (DECs) was analyzed by bioinformatics. The analysis findings were validated by quantitative real-time PCR. Results: In total, 3653 DECs were detected in our ER-positive BC compared with the control. Bioinformatics analysis showed that some pathways related to cancer, especially BC, were significantly enriched. Additionally, hsa_circ_0087378 was validated to be downregulated in ER-positive BC and the hsa_circ_0087378-miR-1260b-SFRP1 axis was proposed to be a key regulatory pathway. Conclusion: This study revealed the general expression characteristics of specific DECs in ER-positive BC and hsa_circ_0087378 might be a promising candidate target.

Stemness, Pluripotentiality, and Wnt Antagonism: sFRP4, a Wnt antagonist Mediates Pluripotency and Stemness in Glioblastoma

BACKGROUND

Chemotherapeutic resistance of glioblastoma has been attributed to a self-renewing subpopulation, the glioma stem cells (GSCs), which is known to be maintained by the Wnt β-catenin pathway. Our previous findings demonstrated that exogeneous addition of the Wnt antagonist, secreted fizzled-related protein 4 (sFRP4) hampered stem cell properties in GSCs.

METHODS

To understand the molecular mechanism of sFRP4, we overexpressed sFRP4 (sFRP4 OE) in three human glioblastoma cell lines U87MG, U138MG, and U373MG. We also performed chromatin immunoprecipitation (ChIP) sequencing of sFRP4 OE and RNA sequencing of sFRP4 OE and sFRP4 knocked down U87 cells.

RESULTS

We observed nuclear localization of sFRP4, suggesting an unknown nuclear role. ChIP-sequencing of sFRP4 pulldown DNA revealed a homeobox Cphx1, related to the senescence regulator ETS proto-oncogene 2 (ETS2). Furthermore, miRNA885, a p53-mediated apoptosis inducer, was upregulated in sFRP4 OE cells. RNA sequencing analysis suggested that sFRP4-mediated apoptosis is via the Fas-p53 pathway by activating the Wnt calcium and reactive oxygen species pathways. Interestingly, sFRP4 OE cells had decreased stemness, but when knocked down in multipotent mesenchymal stem cells, pluripotentiality was induced and the Wnt β-catenin pathway was upregulated.

CONCLUSIONS

This study unveils a novel nuclear role for sFRP4 to promote apoptosis by a possible activation of DNA damage machinery in glioblastoma.

Oncogenic role of SFRP2 in p53-mutant osteosarcoma development via autocrine and paracrine mechanism

Osteosarcoma (OS), the most common primary bone tumor, is highly metastatic with high chemotherapeutic resistance and poor survival rates. Using induced pluripotent stem cells (iPSCs) generated from Li-Fraumeni syndrome (LFS) patients, we investigate an oncogenic role of secreted frizzled-related protein 2 (SFRP2) in p53 mutation-associated OS development. Interestingly, we find that high SFRP2 expression in OS patient samples correlates with poor survival. Systems-level analyses identified that expression of SFRP2 increases during LFS OS development and can induce angiogenesis. Ectopic SFRP2 overexpression in normal osteoblast precursors is sufficient to suppress normal osteoblast differentiation and to promote OS phenotypes through induction of oncogenic molecules such as FOXM1 and CYR61 in a β-catenin-independent manner. Conversely, inhibition of SFRP2, FOXM1, or CYR61 represses the tumorigenic potential. In summary, these findings demonstrate the oncogenic role of SFRP2 in the development of p53 mutation-associated OS and that inhibition of SFRP2 is a potential therapeutic strategy.

Mechanisms of Wnt signaling and control

The Wnt signaling pathway is a highly conserved system that regulates complex biological processes across all metazoan species. At the cellular level, secreted Wnt proteins serve to break symmetry and provide cells with positional information that is critical to the patterning of the entire body plan. At the organismal level, Wnt signals are employed to orchestrate fundamental developmental processes, including the specification of the anterior-posterior body axis, induction of the primitive streak and ensuing gastrulation movements, and the generation of cell and tissue diversity. Wnt functions extend into adulthood where they regulate stem cell behavior, tissue homeostasis, and damage repair. Disruption of Wnt signaling activity during embryonic development or in adults results in a spectrum of abnormalities and diseases, including cancer. The molecular mechanisms that underlie the myriad of Wnt-regulated biological effects have been the subject of intense research for over three decades. This review is intended to summarize our current understanding of how Wnt signals are generated and interpreted. This article is categorized under: Biological Mechanisms > Cell Signaling Developmental Biology > Stem Cell Biology and Regeneration.

The Role of Wnt/β-Catenin Signaling and K-Cadherin in the Regulation of Intraocular Pressure

Purpose

Wnt/β-catenin signaling in the trabecular meshwork (TM) is required for maintaining normal intraocular pressure (IOP), although the mechanism(s) behind this are unknown. We hypothesize that Wnt/β-catenin signaling regulates IOP via β-catenin's effects on cadherin junctions.

Methods

Nonglaucomatous primary human TM (NTM) cells were treated with or without 100 ng/ml Wnt3a, 1 μg/ml sFRP1, or both for 4 to 48 hours. Cells were immunostained for β-catenin, total cadherins, or cadherin isoforms. Membrane proteins or whole-cell lysates were isolated for Western immunoblotting and probed for cadherin isoforms. RNA was extracted for cDNA synthesis and qPCR analysis of cadherin expression. Some NTM cells were cultured on electric plates for cell impedance assays. Ad5.CMV recombinant adenoviruses encoding K-cadherin, and/or sFRP1 were injected into eyes of 4- to 6-month-old female BALB/cJ mice (n = 8–10). Conscious IOPs were assessed for 35 days.

Results

Upon Wnt3a treatment, total cadherin expression increased and β-catenin accumulated at the TM cell membrane and on processes formed between TM cells. qPCR showed that Wnt3a significantly increased K-cadherin expression in NTM cells (P < 0.01, n = 3), and Western immunoblotting showed that Wnt3a increased K-cadherin in NTM cells, which was inhibited by the addition of sFRP1. Cell impedance assays showed that Wnt3a treatment increased transcellular resistance and anti-K-cadherin siRNA decreased transcellular resistance (P < 0.001, n = 4–6). Our in vivo study showed that K-cadherin significantly decreased sFRP1-induced ocular hypertension (P < 0.05, n = 6). Western immunoblotting also showed that K-cadherin alleviated sFRP1-induced β-catenin decrease in mouse anterior segments.

Conclusions

Our results suggest that cadherins play important roles in the regulation of TM homeostasis and IOP via the Wnt/β-catenin pathway.

Opposite Roles of Wnt7a and Sfrp1 in Modulating Proper Development of Neural Progenitors in the Mouse Cerebral Cortex

The Wingless (Wnt)-mediated signals are involved in many important aspects of development of the mammalian cerebral cortex. How Wnts interact with their modulators in cortical development is still unclear. Here, we show that Wnt7a and secreted frizzled-related protein 1 (Sfrp1), a soluble modulator of Wnts, are co-expressed in mouse embryonic cortical neural progenitors (NPs). Knockout of Wnt7a in mice causes microcephaly due to reduced NP population and neurogenesis, and Sfrp1 has an opposing effect compared to Wnt7a. Similar to Dkk1, Sfrp1 decreases the Wnt1 and Wnt7a activity in vitro. Our results suggest that Wnt7a and Sfrp1 play opposite roles to ensure proper NP progeny in the developing cortex.

Bergmann glial Sonic hedgehog signaling activity is required for proper cerebellar cortical expansion and architecture

Neuronal-glial relationships play a critical role in the maintenance of central nervous system architecture and neuronal specification. A deeper understanding of these relationships can elucidate cellular cross-talk capable of sustaining proper development of neural tissues. In the cerebellum, cerebellar granule neuron precursors (CGNPs) proliferate in response to Purkinje neuron-derived Sonic hedgehog (Shh) before ultimately exiting the cell cycle and migrating radially along Bergmann glial fibers. However, the function of Bergmann glia in CGNP proliferation remains not well defined. Interestingly, the Hh pathway is also activated in Bergmann glia, but the role of Shh signaling in these cells is unknown. In this study, we show that specific ablation of Shh signaling using the tamoxifen-inducible TNC^YFP-CreER line to eliminate Shh pathway activator Smoothened in Bergmann glia is sufficient to cause severe cerebellar hypoplasia and a significant reduction in CGNP proliferation. TNC^YFP-CreER; Smo^F/- (Smo^CKO) mice demonstrate an obvious reduction in cerebellar size within two days of ablation of Shh signaling. Mutant cerebella have severely reduced proliferation and increased differentiation of CGNPs due to a significant decrease in Shh activity and concomitant activation of Wnt signaling in Smo^CKO CGNPs, suggesting that this pathway is involved in cross-talk with the Shh pathway in regulating CGNP proliferation. In addition, Purkinje cells are ectopically located, their dendrites stunted, and the Bergmann glial network disorganized. Collectively, these data demonstrate a previously unappreciated role for Bergmann glial Shh signaling activity in the proliferation of CGNPs and proper maintenance of cerebellar architecture.

Matricellular proteins in cancer: a focus on secreted Frizzled-related proteins

Tumours are complex entities, wherein cancer cells interact with myriad soluble, insoluble and cell associated factors. These microenvironmental mediators regulate tumour growth, progression and metastasis, and are produced by cancer cells and by stromal components such as fibroblast, adipocytes and immune cells. Through their ability to bind to extracellular matrix proteins, cell surface receptors and growth factors, matricellular proteins enable a dynamic reciprocity between cancer cells and their microenvironment. Hence, matricellular proteins play a critical role in tumour progression by regulating where and when cancer cells are exposed to key growth factors and regulatory proteins. Recent studies suggest that, in addition to altering Wingless (Wnt) signalling, certain members of the Secreted Frizzled Related Protein (sFRP) family are matricellular in nature. In this review, we outline the importance of matricellular proteins in cancer, and discuss how sFRPs may function to both inhibit and promote cancer progression in a context-dependent manner. By considering the matricellular functionality of sFRPs, we may better understand their apparently paradoxical roles in cancers.

Secreted frizzled related protein 4 (sFRP4) update: A brief review

Secreted frizzled-related proteins control a multitude of biological phenomena throughout development and adult life in humans. In parallel, aberrant gene expression and abnormal secreted protein levels accompany a wide range of pathologies in humans. In this review, we provide a brief introduction to sFRP4, an update of the pathways it's involved, its various physiological actions that are reported to contribute to diseases, outlining the importance of its wider research and specific modulation by pharmacologic interventions. First recognized as a novel molecule that co-purified with a disparate protein, its identity was based on its sequence homology to the frizzled receptors. Once multiple members of the family were cloned, their genetic loci, tissue and subcellular distributions were located. Nucleotide and amino acid sequences were characterized and homology to different organisms was found to be present that helped elucidate their actions. Following subsequent experimental studies, they were found to be secreted proteins with an affinity to bind to the Wnt ligands, participating in different developmental and adult homeostatic pathways by the virtue of their regulatory function to the Wnt signal transduction system. Secreted frizzled related protein 4 has garnered considerable attention in the recent years following breakthrough discoveries implicating them in the pathogenesis of various diseases. Studies investigating them can provide information not only regarding their association with a disease but can also help use them as potential biomarkers and therapeutic targets.

High-frequency deregulated expression of Wnt signaling pathway members in breast carcinomas

Purpose

Breast carcinoma is the most common malignancy and leading cause of cancer-related deaths in women worldwide including Saudi Arabia. Breast cancer in Saudi women develops at a much early age with median age of onset of 49 years compared to 62 years observed in patients from USA. Aberrations in wingless and integration site growth factor (Wnt) signaling pathway have been pathologically implicated in development of breast cancers and hence its role was examined in Saudi patients.

Materials and methods

We immunohistochemically examined various components of Wnt signaling pathway including β-catenin, tumor suppressor proteins, adenomatous polyposis coli (APC), and Axin, expression of naturally occurring pathway antagonists such as Dickkopf Wnt signaling pathway inhibitor 3 (DKK3), FRP2, and WIF1, as well as Wnt target cyclin D1 and c-Myc to establish if the pathway is constitutively activated in breast cancers arising in Saudi women.

Results

Cytoplasmic β-catenin, indicative of activation of the pathway, was observed in 24% of cases. Expression of APC and Axin, which are components of β-catenin destruction complex, was lost in 5% and 10% of tumors, respectively. Additionally, Wnt signaling inhibitors DKK3, FRP2, and Wnt inhibitory factor 1 (WIF1) were not expressed in 8%, 14%, and 5% breast tumors, respectively. Overall, accumulation of cytoplasmic β-catenin and downregulation of other Wnt pathway proteins (APC/Axin/DKK3/FRP2/WIF1) were found in approximately half of the breast cancers (47%) in our cohort. Consistent with this, analysis of Wnt target genes demonstrated moderate-to-strong expression of c-Myc in 58% and cyclin D1 in 50% of breast cancers. Deregulation of Wnt pathway was not associated with age of onset of the disease, tumor grade, and triple-negative status of breast cancers.

Conclusions

High level of deregulated expression of Wnt pathway proteins suggests its important role in pathogenesis of breast cancers arising in Saudi women who may benefit from development of therapeutic drugs targeting this pathway.

Wnt Signaling in the Central Nervous System: New Insights in Health and Disease

Since its discovery, Wnt signaling has been shown to be one of the most crucial morphogens in development and during the maturation of central nervous system. Its action is relevant during the establishment and maintenance of synaptic structure and neuronal function. In this chapter, we will discuss the most recent evidence on these aspects, and we will explore the evidence that involves Wnt signaling on other less known functions, such as in adult neurogenesis, in the generation of oscillatory neural rhythms, and in adult behavior. The dysfunction of Wnt signaling at different levels will be also discussed, in particular in those aspects that have been found to be linked with several neurodegenerative diseases and neurological disorders. Finally, we will address the possibility of Wnt signaling manipulation to treat those pathophysiological aspects.

The Wnt/β-catenin pathway is deregulated in cemento-ossifying fibromas

OBJECTIVE

The molecular pathogenesis of cemento ossifying fibroma (COF) is unclear. The purpose of this study was to investigate mutations in 50 oncogenes and tumor suppressor genes, including APC and CTNNB1, in which mutations in COF have been previously reported. In addition, we assessed the transcriptional levels of the Wnt/β-catenin pathway genes in COF.

STUDY DESIGN

We used a quantitative polymerase chain reaction array to evaluate the transcriptional levels of 44 Wnt/β-catenin pathway genes in 6 COF samples, in comparison with 6 samples of healthy jaws. By using next-generation sequencing (NGS) in 7 COF samples, we investigated approximately 2800 mutations in 50 genes.

RESULTS

The expression assay revealed 12 differentially expressed Wnt/β-catenin pathway genes in COF, including the upregulation of CTNNB1, TCF7, NKD1, and WNT5 A, and downregulation of CTNNBIP1, FRZB, FZD6, RHOU, SFRP4, WNT10 A, WNT3 A, and WNT4, suggesting activation of the Wnt/β-catenin signaling pathway. NGS revealed 5 single nucleotide variants: TP53 (rs1042522), PIK3 CA (rs2230461), MET (rs33917957), KIT (rs3822214), and APC (rs33974176), but none of them was pathogenic.

CONCLUSIONS

Although NGS detected no oncogenic mutation, deregulation of key Wnt/β-catenin signaling pathway genes appears to be relevant to the molecular pathogenesis of COF.

Human epicardial adipose tissue-derived and circulating secreted frizzled-related protein 4 (SFRP4) levels are increased in patients with coronary artery disease

Background

Previous studies have demonstrated that secreted frizzled-related protein 4 (SFRP4) is associated with impaired glucose and triglyceride metabolism in patients with stable coronary artery disease. In the present study, we investigated human epicardial adipose tissue (EAT)-derived and circulating SFRP4 levels in patients with coronary artery disease (CAD).

Methods

Plasma samples and adipose biopsies from EAT and subcutaneous adipose tissue (SAT) were collected from patients with CAD (n = 40) and without CAD (non-CAD, n = 30) during elective cardiac surgery. The presence of CAD was identified by coronary angiography. SFRP4 mRNA and protein expression levels in adipose tissue were detected by quantitative real-time PCR and immunohistochemistry, respectively. Plasma SFRP4 concentrations were measured by an enzyme-linked immunosorbent assay (ELISA). Correlation analysis and multivariate linear regression analysis were used to determine the association of SFRP4 expression with atherosclerosis as well as clinical risk factors.

Results

SFRP4 mRNA and protein expression levels were significantly lower in EAT than in paired SAT in patients with and without CAD (all P < 0.05). Compared to non-CAD patients, CAD patients had higher SFRP4 expression levels in EAT (both mRNA and protein levels) and in plasma. Multivariate linear regression analysis showed that CAD was an independent predictor of SFRP4 expression levels in EAT (beta = 0.442, 95% CI 0.030–0.814; P = 0.036) and in plasma (beta = 0.300, 95% CI 0.056–0.545; P = 0.017). SAT-derived SFRP4 mRNA levels were independently associated with fasting insulin levels (beta = 0.382, 95% CI 0.008–0.756; P = 0.045). In addition, plasma SFRP4 levels were positively correlated with BMI (r = 0.259, P = 0.030), fasting insulin levels (r = 0.306, P = 0.010) and homeostasis model assessment of insulin resistance (HOMA-IR) values (r = 0.331, P = 0.005).

Conclusions

EAT-derived and circulating SFRP4 expression levels were increased in patients with CAD. EAT SFRP4 mRNA levels and plasma SFRP4 concentrations were independently associated with the presence of CAD.

The crystal structure of full-length Sizzled from Xenopus laevis yields insights into Wnt-antagonistic function of secreted Frizzled-related proteins

The Wnt-signaling pathway is crucial to cell proliferation, differentiation, and migration. The secreted Frizzled-related proteins (sFRPs) represent the largest family of secreted Wnt inhibitors. However, their function in antagonizing Wnt signaling has remained somewhat controversial. Here, we report the crystal structure of Sizzled from Xenopus laevis, the first full-length structure of an sFRP. Tethered by an inter-domain disulfide bond and a linker, the N-terminal cysteine-rich domain (CRD) and the C-terminal netrin-like domain (NTR) of Sizzled are arranged in a tandem fashion, with the NTR domain occluding the groove of CRD for Wnt accessibility. A Dual-Luciferase assay demonstrated that removing the NTR domain and replacing the CRD groove residues His-116 and His-118 with aromatic residues may significantly enhance antagonistic function of Sizzled in inhibiting Wnt3A signaling. Sizzled is a monomer in solution, and Sizzled CRD exhibited different packing in the crystal, suggesting that sFRPs do not have a conserved CRD dimerization mode. Distinct from the canonical NTR domain, the Sizzled NTR adopts a novel α/β folding with two perpendicular helices facing the central mixed β-sheet. The subgroup of human sFRP1/2/5 and Sizzled should have a similar NTR domain that features a highly positively charged region, opposite the NTR-CRD interface, suggesting that the NTR domain in human sFRPs, at least sFRP1/2/5, is unlikely to bind to Wnt but is likely involved in biphasic Wnt signaling modulation. In summary, the Sizzled structure provides the first insights into how the CRD and the NTR domains relate to each other for modulating Wnt-antagonistic function of sFRPs.

Regulation of early growth response 2 expression by secreted frizzled related protein 1

BACKGROUND

Secreted frizzled-related protein 1 (SFRP1) expression is down-regulated in a multitude of cancers, including breast cancer. Loss of Sfrp1 also exacerbates weight gain as well as inflammation. Additionally, loss of SFRP1 enhances TGF-β signaling and the downstream MAPK pathway. TGF-β has been shown to increase the expression of Early Growth Response 2 (EGR2), a transcription factor implicated in immune function in a wide variety of cell types. The work described here was initiated to determine whether SFRP1 modulation affects TGF-β mediated EGR2 expression in mammary tissues as well as macrophage polarization.

METHODS

Real-time PCR analysis was performed to examine EGR2 expression in human and murine mammary epithelial cells and tissues in response to SFRP1 modulation. Chemical inhibition was employed to investigate the roles TGF-β and MAPK signaling play in the control of EGR2 expression in response to SFRP1 loss. Primary murine macrophages were isolated from Sfrp1^-/- mice and stimulated to become either M1 or M2 macrophages, treated with recombinant SFRP1, and real-time PCR was used to measure the expression of murine specific M1/M2 markers [Egr2 (M2) and Gpr18 (M1)]. Immunohistochemical analysis was used to measure the expression of human specific M1/M2 markers [CD163 (M2) and HLA-DRA (M2)] in response to rSFRP1 treatment in human mammary explant tissue.

RESULTS

Knockdown of SFRP1 expression increases the expression of EGR2 mRNA in human mammary epithelial cells and addition of rSFRP1 decreases the expression of EGR2 when added to explant mammary gland tissues. Chemical inhibition of both TGF-β and MAPK signaling in Sfrp1^-/- or knockdown mammary epithelial cells results in decreased expression of EGR2. Stimulated murine macrophages obtained from Sfrp1^-/- mice and treated with rSFRP1 exhibit a reduction in Egr2 expression and an increase in Gpr18 mRNA expression. Human mammary explant tissue treated with rSFRP1 decreases CD163 protein expression whereas there was no effect on the expression of HLA-DRA.

CONCLUSIONS

Loss of SFRP1 likely contributes to tumor progression by altering the expression of a critical transcription factor in both the epithelium and the immune system.

DNA hypermethylation of sFRP5 contributes to indoxyl sulfate-induced renal fibrosis

Renal fibrosis is the most common outcome of chronic kidney disease (CKD), while the pathogenesis of renal fibrosis is not fully understood. In this study, we first showed that the progress of renal fibrosis was positively related to serum levels of indoxyl sulfate, a typical protein-bound toxin, and that there was a close correlation between serum indoxyl sulfate levels and β-catenin expression in the kidneys (r = 0.908, p < 0.001) of CKD patients. We then demonstrated that intraperitoneal injections of indoxyl sulfate (100 mg/kg/day) for 4 weeks in uninephrectomized mice explicitly induced renal fibrosis, which was accompanied by a significant activation of Wnt/β-catenin signaling. In vitro investigations in human renal tubular HK-2 cells revealed that indoxyl sulfate exhibited a potent ability to induce Wnt/β-catenin activation through the downregulation of sFRP5, a gene that codes for an extracellular antagonist of Wnt signaling, by increasing the DNA methylation level of its promoter CpG islands. The increased expression of DNA methyltransferases following the activation of ROS/ERK1/2 signaling was responsible for the DNA hypermethylation of sFRP5 induced by indoxyl sulfate. Conversely, treatment with 5-aza-2'-deoxycytidine, an inhibitor of DNA methyltransferases, significantly reduced indoxyl sulfate-induced sFRP5 downregulation and Wnt/β-catenin activation. In vivo, intraperitoneal injections of recombinant sFRP5 protein or 5-aza-2'-deoxycytidine substantially alleviated renal fibrosis in indoxyl sulfate-treated uninephrectomized mice. Our results suggest that indoxyl sulfate promotes renal fibrosis through the induction of DNA hypermethylation of sFRP5, and thereafter the activation of Wnt/β-catenin signaling. These findings provide new insights into the pathogenesis of renal fibrosis in CKD patients.

KEY MESSAGES

IS induces renal fibrosis by increasing ß-catenin expression in CKD mice. IS-induced Wnt signaling activation is due to sFRP5 hypermethylation in HK-2 cells. ROS/ERK1/2 signaling activation is involved in IS-induced sFRP5 hypermethylation. sFRP5 upregulation attenuates IS-induced renal fibrosis by inhibiting Wnt signaling.

Wnt signaling and cellular metabolism in osteoblasts

The adult human skeleton is a multifunctional organ undergoing continuous remodeling. Homeostasis of bone mass in a healthy adult requires an exquisite balance between bone resorption by osteoclasts and bone formation by osteoblasts; disturbance of such balance is the root cause for various bone disorders including osteoporosis. To develop effective and safe therapeutics to modulate bone formation, it is essential to elucidate the molecular mechanisms governing osteoblast differentiation and activity. Due to their specialized function in collagen synthesis and secretion, osteoblasts are expected to consume large amounts of nutrients. However, studies of bioenergetics and building blocks in osteoblasts have been lagging behind those of growth factors and transcription factors. Genetic studies in both humans and mice over the past 15 years have established Wnt signaling as a critical mechanism for stimulating osteoblast differentiation and activity. Importantly, recent studies have uncovered that Wnt signaling directly reprograms cellular metabolism by stimulating aerobic glycolysis, glutamine catabolism as well as fatty acid oxidation in osteoblast-lineage cells. Such findings therefore reveal an important regulatory axis between bone anabolic signals and cellular bioenergetics. A comprehensive understanding of osteoblast metabolism and its regulation is likely to reveal molecular targets for novel bone therapies.

Molecular Signaling of Progesterone, Growth Hormone, Wnt, and HER in Mammary Glands of Dogs, Rodents, and Humans: New Treatment Target Identification

Mammary tumors are the most common form of neoplasia in the bitch. Female dogs are protected when they are spayed before the first estrus cycle, but this effect readily disappears and is already absent when dogs are spayed after the second heat. As the ovaries are removed during spaying, ovarian steroids are assumed to play an essential role in tumor development. The sensitivity toward tumor development is already present during early life, which may be caused by early mutations in stem cells during the first estrus cycles. Later on in life, tumors arise that are mostly steroid-receptor positive, although a small subset of tumors overexpressing human epidermal growth factor 2 (HER2) and some lacking estrogen receptor, progesterone receptor (PR), and HER2 (triple negative) are present, as is the situation in humans. Progesterone (P₄), acting through PR, is the major steroid involved in outgrowth of mammary tissue. PRs are expressed in two forms, the progesterone receptor A (PRA) and progesterone receptor B (PRB) isoforms derived from splice variants from a single gene. The dog and the whole family of canids have only a functional PRA isoform, whereas the PRB isoform, if expressed at all, is devoid of intrinsic biological activity. In human breast cancer, overexpression of the PRA isoform is related to more aggressive carcinomas making the dog a unique model to study PRA-related mammary cancer. Administration of P₄ to adult dogs results in local mammary expression of growth hormone (GH) and wing less-type mouse mammary tumor virus integration site family 4 (Wnt4). Both proteins play a role in activation of mammary stem cells. In this review, we summarize what is known on P₄, GH, and Wnt signaling in canine mammary cancer, how the family of HER receptors could interact with this signaling, and what this means for comparative and translational oncological aspects of human breast cancer development.