Targeting Wnt pathways in disease

Targeting LRP6: A new strategy for cancer therapy

Targeting specific molecular drivers of tumor growth is a key approach in cancer therapy. Among these targets, the low-density lipoprotein receptor-related protein 6 (LRP6), a vital component of the Wnt signaling pathway, has emerged as an intriguing candidate. As a cell-surface receptor and vital co-receptor, LRP6 is frequently overexpressed in various cancer types, implicating its pivotal role in driving tumor progression. The pursuit of LRP6 as a target for cancer treatment has gained substantial traction, offering a promising avenue for therapeutic intervention. Here, this comprehensive review explores recent breakthroughs in our understanding of LRP6's functions and underlying molecular mechanisms, providing a profound discussion of its involvement in cancer pathogenesis and drug resistance. Importantly, we go beyond discussing LRP6's role in cancer by discussing diverse potential therapeutic approaches targeting this enigmatic protein. These approaches encompass a wide spectrum, including pharmacological agents, natural compounds, non-coding RNAs, epigenetic factors, proteins, and peptides that modulate LRP6 expression or disrupt its interactions. In addition, also discussed the challenges associated with developing LRP6 inhibitors and their advantages over Wnt inhibitors, as well as the drugs that have entered phase II clinical trials. By shedding light on these innovative strategies, we aim to underscore LRP6's significance as a valuable and multifaceted target for cancer treatment, igniting enthusiasm for further research and facilitating translation into clinical applications.

The regulatory role and clinical application prospects of circRNA in the occurrence and development of CNS tumors

BACKGROUND

Central nervous system (CNS) tumors originate from the spinal cord or brain. The study showed that even with aggressive treatment, malignant CNS tumors have high mortality rates. However, CNS tumor risk factors and molecular mechanisms have not been verified. Due to the reasons mentioned above, diagnosis and treatment of CNS tumors in clinical practice are currently fraught with difficulties. Circular RNAs (circRNAs), single-stranded ncRNAs with covalently closed continuous structures, are essential to CNS tumor development. Growing evidence has proved the numeral critical biological functions of circRNAs for disease progression: sponging to miRNAs, regulating gene transcription and splicing, interacting with proteins, encoding proteins/peptides, and expressing in exosomes.

AIMS

This review aims to summarize current progress regarding the molecular mechanism of circRNA in CNS tumors and to explore the possibilities of clinical application based on circRNA in CNS tumors.

METHODS

We have summarized studies of circRNA in CNS tumors in Pubmed.

RESULTS

This review summarized their connection with CNS tumors and their functions, biogenesis, and biological properties. Furthermore, we introduced current advances in clinical RNA-related technologies. Then we discussed the diagnostic and therapeutic potential (especially for immunotherapy, chemotherapy, and radiotherapy) of circRNA in CNS tumors in the context of the recent advanced research and application of RNA in clinics.

CONCLUSIONS

CircRNA are increasingly proven to participate in decveloping CNS tumors. An in-depth study of the causal mechanisms of circRNAs in CNS tomor progression will ultimately advance their implementation in the clinic and developing new strategies for preventing and treating CNS tumors.

Wnt Signaling in Atherosclerosis: Mechanisms to Therapeutic Implications

Atherosclerosis is a vascular disease in which inflammation plays a pivotal role. Receptor-mediated signaling pathways regulate vascular inflammation and the pathophysiology of atherosclerosis. Emerging evidence has revealed the role of the Wnt pathway in atherosclerosis progression. The Wnt pathway influences almost all stages of atherosclerosis progression, including endothelial dysfunction, monocyte infiltration, smooth muscle cell proliferation and migration, and plaque formation. Targeting the Wnt pathway to treat atherosclerosis represents a promising therapeutic approach that remains understudied. Blocking Wnt signaling utilizing small molecule inhibitors, recombinant proteins, and/or neutralizing antibodies ameliorates atherosclerosis in preclinical models. The Wnt pathway can be potentially manipulated through targeting Wnt ligands, receptors, co-receptors, and downstream signaling molecules. However, there are challenges associated with developing a real world therapeutic compound that targets the Wnt pathway. This review focuses on the role of Wnt signaling in atherosclerosis development, and the rationale for targeting this pathway for the treatment of atherosclerosis.

Wnt5a: A promising therapeutic target for inflammation, especially rheumatoid arthritis

BACKGROUND

Wnt5a is a member of the Wnt protein family, which acts on classical or multiple non-classical Wnt signaling pathways by binding to different receptors. The expression regulation and signal transduction of Wnt5a is closely related to the inflammatory response. Abnormal activation of Wnt5a signaling is an important part of inflammation and rheumatoid arthritis (RA).

OBJECTIVES

This paper mainly focuses on Wnt5a protein and its mediated signaling pathway, summarizes the latest research progress of Wnt5a in the pathological process of inflammation and RA, and looks forward to the main directions of Wnt5a in RA research, aiming to provide a theoretical basis for the prevention and treatment of RA diseases by targeting Wnt5a.

RESULTS

Wnt5a is highly expressed in activated blood vessels, histocytes and synoviocytes in inflammatory diseases such as sepsis, sepsis, atherosclerosis and rheumatoid arthritis. It mediates the production of pro-inflammatory cytokines and chemokines, regulates the migration and recruitment of various immune effector cells, and thus participates in the inflammatory response. Wnt5a plays a pathological role in synovial inflammation and bone destruction of RA, and may be an important clinical therapeutic target for RA.

CONCLUSION

Wnt5a is involved in the pathological process of inflammation and interacts with inflammatory factors. Wnt5a may be a new target for regulating the progression of RA disease and intervening therapy because of its multi-modal effects on the etiology of RA, especially as a regulator of osteoclast activity and inflammation.

The biotoxin BMAA promotes dysfunction via distinct mechanisms in neuroblastoma and glioblastoma cells

Chronic exposure to the Cyanobacteria biotoxin Beta-methylamino-L-alanine (BMAA) has been associated with development of a sporadic form of ALS called Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex (ALS/PDC), as observed within certain Indigenous populations of Guam and Japan. Studies in primate models and cell culture have supported the association of BMAA with ALS/PDC, yet the pathological mechanisms at play remain incompletely characterized, effectively stalling the development of rationally-designed therapeutics or application of preventative measures for this disease. In this study we demonstrate for the first time that sub-excitotoxic doses of BMAA modulate the canonical Wnt signaling pathway to drive cellular defects in human neuroblastoma cells, suggesting a potential mechanism by which BMAA may promote neurological disease. Further, we demonstrate here that the effects of BMAA can be reversed in cell culture by use of pharmacological modulators of the Wnt pathway, revealing the potential value of targeting this pathway therapeutically. Interestingly, our results suggest the existence of a distinct Wnt-independent mechanism activated by BMAA in glioblastoma cells, highlighting the likelihood that neurological disease may result from the cumulative effects of distinct cell-type specific mechanisms of BMAA toxicity.

Non-canonical WNT signalling in cardiovascular disease: mechanisms and therapeutic implications

WNT signalling comprises a diverse spectrum of receptor-mediated pathways activated by a large family of WNT ligands and influencing fundamental biological processes. WNT signalling includes the β-catenin canonical pathway and the non-canonical pathways, namely the planar cell polarity and the calcium-dependent pathways. Advances over the past decade have linked non-canonical WNT signalling with key mechanisms of atherosclerosis, including oxidative stress, endothelial dysfunction, macrophage activation and vascular smooth muscle cell phenotype regulation. In addition, non-canonical WNT signalling is involved in crucial aspects of myocardial biology, from fibrosis to hypertrophy and oxidative stress. Importantly, non-canonical WNT signalling activation has complex effects in adipose tissue in the context of obesity, thereby potentially linking metabolic and vascular diseases. Tissue-specific targeting of non-canonical WNT signalling might be associated with substantial risks of off-target tumorigenesis, challenging its therapeutic potential. However, novel technologies, such as monoclonal antibodies, recombinant decoy receptors, tissue-specific gene silencing with small interfering RNAs and gene editing with CRISPR-Cas9, might enable more efficient therapeutic targeting of WNT signalling in the cardiovascular system. In this Review, we summarize the components of non-canonical WNT signalling, their links with the main mechanisms of atherosclerosis, heart failure and arrhythmias, and the rationale for targeting individual components of non-canonical WNT signalling for the treatment of cardiovascular disease.

Decreased Serum Dickkopf-1 Levels After Hypoglycemic Therapy in Patients with Type 2 Diabetes Mellitus

AIM

Dickkopf-1 (DKK-1) is a major inhibitor of Wingless protein signaling pathway, which is involved in glucose metabolism and cardiovascular diseases. The aim of the study was to investigate the changes of serum DKK-1 levels after hypoglycemic treatments and the relationship between DKK-1 and clinical parameters.

MATERIALS AND METHODS

The study was a sub-study of a previously published clinical trial (the effect of Acarbose on glycemic variability in patients with type 2 diabetes mellitus using premixed insulin compared to metformin). All subjects underwent anthropometric and biochemical assessments at baseline and endpoint. Serum DKK-1 levels of 92 subjects were measured at baseline and after 12-week hypoglycemic treatment.

RESULTS

DKK-1 levels were significantly decreased after hypoglycemic treatment for 12 weeks (P < 0.001). ΔDKK-1 levels were not correlated with improvement of metabolic parameters (all P > 0.05) but were negatively correlated with baseline DKK-1 levels (r = -0.263, P = 0.011). Spearman correlation showed that baseline DKK-1 levels were positively related to baseline total cholesterol (r = 0.226, P = 0.030) and low-density lipoprotein cholesterol (LDL-C) (r = 0.277, P = 0.007). Compared with the higher baseline DKK-1 group (≥3700 pg/mL), subjects in the lower baseline DKK-1 group (<3700 pg/mL) had significantly lower baseline glycated hemoglobin A1c levels (P = 0.008) and LDL-C levels (P = 0.048). Systolic and diastolic pressure were decreased more significantly in the lower baseline DKK-1 group than that in the higher baseline DKK-1 group (both P < 0.05).

CONCLUSION

Serum DKK-1 levels were decreased after hypoglycemic treatments. Patients with lower baseline DKK-1 levels were featured by more favorable cardiometabolic factors.

Domestication of chemicals attacking metazoan embryogenesis: identification of safe natural products modifying developmental signaling pathways in human

Soil microorganisms are rich sources of bioactive natural products. Interspecies interactions are the cues of their production and refine biological activities. These interactions in natural environments include the interplay between microorganisms and Metazoans (animals), such as nematodes, insects, and ticks. Chemical intercellular communication modulators could exert ideal Metazoan-selective toxicity for defending microorganisms. Developmental signaling pathways, such as the Notch, TGF-beta, and Wnt pathways, are intercellular communication networks that contribute to the reproducible formation of complex higher-order Metazoan body structures. Natural modifiers of the developmental signaling pathway are attractive therapeutic seeds for carcinoma and sarcoma treatment. However, these fundamental signaling pathways also play indispensable physiological roles and their perturbation could lead to toxicity, such as defects in stem cell physiology and tissue regeneration processes. In this review, we introduce a screening system that selects developmental signaling inhibitors with wide therapeutic windows using zebrafish embryonic phenotypes and provide examples of microorganism-derived Wnt pathway inhibitors. Moreover, we discuss safety prospects of the developmental signaling inhibitors.

Regulation of Avian Leukosis Virus Subgroup J Replication by Wnt/β-Catenin Signaling Pathway

Wnt/β-catenin signaling is a highly conserved pathway related to a variety of biological processes in different cells. The regulation of replication of various viruses by Wnt/β-catenin signaling pathway has been reported. However, the interaction between the Wnt/β-catenin pathway and avian leukosis virus is unknown. In the present study, we investigated the effect of modulating the Wnt/β-catenin pathway during avian leukosis virus subgroup J (ALV-J) infection. The activation of the Wnt/β-catenin pathway by GSK-3 inhibitor increased ALV-J mRNA, viral protein expression, and virus production in CEF cells. This increase was suppressed by iCRT14, one of the specific inhibitors of the Wnt/β-catenin signaling pathway. Moreover, treatment with iCRT14 reduced virus titer and viral gene expression significantly in CEF and LMH cells in a dose-dependent manner. Inhibition Wnt/β-catenin signaling pathway by knockdown of β-catenin reduced virus proliferation in CEF cells also. Collectively, these results suggested that the status of Wnt/β-catenin signaling pathway modulated ALV-J replication. These studies extend our understanding of the role of Wnt/β-catenin signaling pathway in ALV-J replication and make a new contribution to understanding the virus–host interactions of avian leukosis virus.

PARsylated transcription factor EB (TFEB) regulates the expression of a subset of Wnt target genes by forming a complex with β-catenin-TCF/LEF1

Wnt signaling is mainly transduced by β-catenin via regulation of the β-catenin destruction complex containing Axin, APC, and GSK3β. Transcription factor EB (TFEB) is a well-known master regulator of autophagy and lysosomal biogenesis processes. TFEB's nuclear localization and transcriptional activity are also regulated by various upstream signals. In this study, we found that Wnt signaling induces the nuclear localization of TFEB and the expression of Wnt target genes is regulated by TFEB-β-catenin-TCF/LEF1 as well as β-catenin-TCF/LEF1 complexes. Our biochemical data revealed that TFEB is a part of the β-catenin destruction complex, and destabilization of the destruction complex by knockdown of either Axin or APC causes nuclear localization of TFEB. Interestingly, RNA-sequencing analysis revealed that about 27% of Wnt3a-induced genes were TFEB dependent. However, these "TFEB mediated Wnt target genes" were different from TFEB target genes involved in autophagy and lysosomal biogenesis processes. Mechanistically, we found that Tankyrase (TNKS) PARsylates TFEB with Wnt ON signaling, and the nuclear localized PARsylated TFEB forms a complex with β-catenin-TCF/LEF1 to induce the "TFEB mediated Wnt target genes". Finally, we found that in various types of cancer, the levels of TFEB mediated Wnt target genes exhibit strong correlations with the level of Axin2, which represents the activity of Wnt signaling. Overall, our data suggest that Wnt signaling induces the expression of a subset of genes that are distinct from previously known genes regulated by the β-catenin-TCF/LEF1 complex or TFEB, by forming a transcription factor complex consisting of PARsylated TFEB and β-catenin-TCF/LEF1.

Pharmacological Manipulation of Wnt/β-Catenin Signaling Pathway in Human Neural Precursor Cells Alters Their Differentiation Potential and Neuronal Yield

The canonical Wnt/β-catenin pathway is a master-regulator of cell fate during embryonic and adult neurogenesis and is therefore a major pharmacological target in basic and clinical research. Chemical manipulation of Wnt signaling during in vitro neuronal differentiation of stem cells can alter both the quantity and the quality of the derived neurons. Accordingly, the use of Wnt activators and blockers has become an integral part of differentiation protocols applied to stem cells in recent years. Here, we investigated the effects of the glycogen synthase kinase-3β inhibitor CHIR99021, which upregulates β-catenin agonizing Wnt; and the tankyrase-1/2 inhibitor XAV939, which downregulates β-catenin antagonizing Wnt. Both drugs and their potential neurogenic and anti-neurogenic effects were studied using stable lines human neural precursor cells (hNPCs), derived from embryonic stem cells, which can be induced to generate mature neurons by chemically-defined conditions. We found that Wnt-agonism by CHIR99021 promotes induction of neural differentiation, while also reducing cell proliferation and survival. This effect was not synergistic with those of pro-neural growth factors during long-term neuronal differentiation. Conversely, antagonism of Wnt by XAV939 consistently prevented neuronal progression of hNPCs. We show here how these two drugs can be used to manipulate cell fate and how self-renewing hNPCs can be used as reliable human in vitro drug-screening platforms.

The role of Wnt signaling in skin fibrosis

Skin fibrosis is the excessive deposition of extracellular matrix in the dermis. Cutaneous fibrosis can occur following tissue injury, including burns, trauma, and surgery, resulting in scars that are disfiguring, limit movement and cause significant psychological distress for patients. Many molecular pathways have been implicated in the development of skin fibrosis, yet effective treatments to prevent or reverse scarring are unknown. The Wnt signaling pathways are known to play an important role in skin homeostasis, skin injury, and in the development of fibrotic skin diseases. This review provides a detailed overview of the role of the canonical Wnt signaling pathways in regulating skin scarring. We also discuss how Wnt signaling interacts with other known fibrotic molecular pathways to cause skin fibrosis. We further provide a summary of the different Wnt inhibitor types available for treating skin scarring. Understanding the role of the Wnt pathway in cutaneous fibrosis will accelerate the development of effective Wnt modulators for the treatment of skin fibrosis.

Wnt signaling activation: targets and therapeutic opportunities for stem cell therapy and regenerative medicine

Wnt proteins are secreted morphogens that play critical roles in embryonic development, stem cell proliferation, self-renewal, tissue regeneration and remodeling in adults. While aberrant Wnt signaling contributes to diseases such as cancer, activation of Wnt/β-catenin signaling is a target of interest in stem cell therapy and regenerative medicine. Recent high throughput screenings from chemical and biological libraries, combined with improved gene expression reporter assays of Wnt/β-catenin activation together with rational drug design, led to the development of a myriad of Wnt activators, with different mechanisms of actions. Among them, Wnt mimics, antibodies targeting Wnt inhibitors, glycogen-synthase-3β inhibitors, and indirubins and other natural product derivatives are emerging modalities to treat bone, neurodegenerative, eye, and metabolic disorders, as well as prevent ageing. Nevertheless, the creation of Wnt-based therapies has been hampered by challenges in developing potent and selective Wnt activators without off-target effects, such as oncogenesis. On the other hand, to avoid these risks, their use to promote ex vivo expansion during tissue engineering is a promising application.

Wnt-C59 inhibits proinflammatory cytokine expression by reducing the interaction between β-catenin and NF-κB in LPS-stimulated epithelial and macrophage cells

Dysregulation of the Wnt pathway causes various diseases including cancer, Parkinson’s disease, Alzheimer’s disease, schizophrenia, osteoporosis, obesity and chronic kidney diseases. The modulation of dysregulated Wnt pathway is absolutely necessary. In the present study, we evaluated the anti-inflammatory effect and the mechanism of action of Wnt-C59, a Wnt signaling inhibitor, in lipopolysaccharide (LPS)-stimulated epithelial cells and macrophage cells. Wnt-C59 showed a dose-dependent anti-inflammatory effect by suppressing the expression of proinflammatory cytokines including IL6, CCL2, IL1A, IL1B, and TNF in LPS-stimulated cells. The dysregulation of the Wnt/β-catenin pathway in LPS stimulated cells was suppressed by Wnt-C59 treatment. The level of β-catenin, the executor protein of Wnt/β-catenin pathway, was elevated by LPS and suppressed by Wnt-C59. Overexpression of β-catenin rescued the suppressive effect of Wnt-C59 on proinflammatory cytokine expression and nuclear factor-kappa B (NF-κB) activity. We found that the interaction between β-catenin and NF-κB, measured by co-immunoprecipitation assay, was elevated by LPS and suppressed by Wnt-C59 treatment. Both NF-κB activity for its target DNA binding and the reporter activity of NF-κB-responsive promoter showed identical patterns with the interaction between β-catenin and NF-κB. Altogether, our findings suggest that the anti-inflammatory effect of Wnt-C59 is mediated by the reduction of the cellular level of β-catenin and the interaction between β-catenin and NF-κB, which results in the suppressions of the NF-κB activity and proinflammatory cytokine expression.

Discovering small molecules as Wnt inhibitors that promote heart regeneration and injury repair

There are intense interests in discovering proregenerative medicine leads that can promote cardiac differentiation and regeneration, as well as repair damaged heart tissues. We have combined zebrafish embryo-based screens with cardiomyogenesis assays to discover selective small molecules that modulate heart development and regeneration with minimal adverse effects. Two related compounds with novel structures, named as Cardiomogen 1 and 2 (CDMG1 and CDMG2), were identified for their capacity to promote myocardial hyperplasia through expansion of the cardiac progenitor cell population. We find that Cardiomogen acts as a Wnt inhibitor by targeting β-catenin and reducing Tcf/Lef-mediated transcription in cultured cells. CDMG treatment of amputated zebrafish hearts reduces nuclear β-catenin in injured heart tissue, increases cardiomyocyte (CM) proliferation, and expedites wound healing, thus accelerating cardiac muscle regeneration. Importantly, Cardiomogen can alleviate the functional deterioration of mammalian hearts after myocardial infarction. Injured hearts exposed to CDMG1 display increased newly formed CMs and reduced fibrotic scar tissue, which are in part attributable to the β-catenin reduction. Our findings indicate Cardiomogen as a Wnt inhibitor in enhancing injury-induced CM proliferation and heart regeneration, highlighting the values of embryo-based small molecule screens in discovery of effective and safe medicine leads.

Induction of Wnt signaling antagonists and p21-activated kinase enhances cardiomyocyte proliferation during zebrafish heart regeneration

Heart regeneration occurs by dedifferentiation and proliferation of pre-existing cardiomyocytes (CMs). However, the signaling mechanisms by which injury induces CM renewal remain incompletely understood. Here, we find that cardiac injury in zebrafish induces expression of the secreted Wnt inhibitors, including Dickkopf 1 (Dkk1), Dkk3, secreted Frizzled-related protein 1 (sFrp1), and sFrp2, in cardiac tissue adjacent to injury sites. Experimental blocking of Wnt activity via Dkk1 overexpression enhances CM proliferation and heart regeneration, whereas ectopic activation of Wnt8 signaling blunts injury-induced CM dedifferentiation and proliferation. Although Wnt signaling is dampened upon injury, the cytoplasmic β-catenin is unexpectedly increased at disarrayed CM sarcomeres in myocardial wound edges. Our analyses indicated that p21-activated kinase 2 (Pak2) is induced at regenerating CMs, where it phosphorylates cytoplasmic β-catenin at Ser 675 and increases its stability at disassembled sarcomeres. Myocardial-specific induction of the phospho-mimetic β-catenin (S675E) enhances CM dedifferentiation and sarcomere disassembly in response to injury. Conversely, inactivation of Pak2 kinase activity reduces the Ser 675-phosphorylated β-catenin (pS675-β-catenin) and attenuates CM sarcomere disorganization and dedifferentiation. Taken together, these findings demonstrate that coordination of Wnt signaling inhibition and Pak2/pS675-β-catenin signaling enhances zebrafish heart regeneration by supporting CM dedifferentiation and proliferation.

Inflammation status in HIV-positive individuals correlates with changes in bone tissue quality after initiation of ART

BACKGROUND

The mechanisms behind ART-induced bone changes in HIV-infected patients are poorly known. We aimed to analyse changes in inflammatory and bone markers in HIV after tenofovir disoproxil fumarate initiation, and the associations with changes in the bone strength parameters.

METHODS

HIV-positive participants starting tenofovir disoproxil fumarate-based ART underwent dual-energy X-ray absorptiometry (QDR 4500 SL®, Hologic, Waltham, MA, USA) for bone mineral density (BMD), a microindentation test (OsteoProbe®, Active Life Scientific, Santa Barbara, CA, USA) for bone quality [bone material strength index (BMSi)] and phlebotomy at baseline and 48 weeks after ART. A panel of inflammatory biomarkers and bone turnover markers were measured by ELISA. HIV-negative controls underwent identical procedures once. Values are expressed as medians and IQRs, and non-parametric tests were used to perform the analysis.

RESULTS

Twenty HIV-infected individuals and 20 HIV-negative control individuals were matched in terms of age and gender. HIV individuals showed higher levels of inflammatory markers. We found no differences in bone turnover markers. HIV-positive individuals presented lower BMSi values at baseline compared with controls [86 (83-90) versus 89 (88-93), respectively; P = 0.034]. We found no difference in BMD (at either of the sites evaluated). BMSi tended to increase with treatment. IL-1β at baseline was positively correlated with changes in BMSi after ART (rho = 0.564, P = 0.014). Baseline levels of sclerostin tended to be negatively correlated with changes in BMSi (rho = -0.402, P = 0.097). We found a negative correlation between time since HIV diagnosis and changes in BMSi (rho = -0.466, P = 0.04).

CONCLUSIONS

We observed a correlation between changes in bone quality and the inflammatory environment in HIV-positive individuals. Moreover, among the underlying mechanisms we highlight the Wnt pathway as having a potentially significant role in ART bone quality recovery.

Spinal Wnt5a Plays a Key Role in Spinal Dendritic Spine Remodeling in Neuropathic and Inflammatory Pain Models and in the Proalgesic Effects of Peripheral Wnt3a

Wnt signaling represents a highly versatile signaling system, which plays critical roles in developmental morphogenesis as well as synaptic physiology in adult life and is implicated in a variety of neural disorders. Recently, we demonstrated that Wnt3a is able to recruit multiple noncanonical signaling pathways to alter peripheral sensory neuron function in a nociceptive modality-specific manner. Furthermore, several studies recently reported an important role for Wnt5a acting via canonical and noncanonical signaling in spinal processing of nociception in a number of pathologic pain disorders. Here, using diverse molecular, genetic, and behavioral approaches in mouse models of pain in vivo, we report a novel role for Wnt5a signaling in nociceptive modulation at the structural level. In models of chronic pain, using male and female mice, we found that Wnt5a is released spinally from peripheral sensory neurons, where it recruits the tyrosine kinase receptors Ror2 and Ryk to modulate dendritic spine rearrangement. Blocking the Wnt5a-Ryk/Ror2 axis in spinal dorsal horn neurons prevented activity-dependent dendritic spine remodeling and significantly reduced mechanical hypersensitivity induced by peripheral injury as well as inflammation. Moreover, we observed that peripheral Wnt3a signaling triggers the release of Wnt5a in the spinal cord, and inhibition of spinal Wnt5a signaling attenuates the functional impact of peripheral Wnt3a on nociceptive sensitivity. In conclusion, this study reports a novel role for the Wnt signaling axis in coordinating peripheral and spinal sensitization and shows that targeting Wnt5a-Ryk/ROR2 signaling alleviates both structural and functional mechanisms of nociceptive hypersensitivity in models of chronic pain in vivo SIGNIFICANCE STATEMENT There is a major need to elucidate molecular mechanisms underlying chronic pain disorders to develop novel therapeutic approaches. Wnt signaling represents a highly versatile signaling system, which plays critical roles during development and adult physiology, and it was implicated in several diseases, including chronic pain conditions. Using mouse models, our study identifies a novel role for Wnt5a signaling in nociceptive modulation at the spinal cord level. We observed that Wnt5a recruits Ror2 and Ryk receptors to enhance dendritic spine density, leading to nociceptive sensitization. Blocking the Wnt5a-Ryk/Ror2 interaction in the spinal dorsal horn prevented spine remodeling and significantly reduced inflammatory and neuropathic hypersensitivity. These findings provide proof-of-concept for targeting spinal Wnt signaling for alleviating nociceptive hypersensitivity in vivo.

Evaluation of the Wnt signaling pathway as a prognostic marker in patients with urosepsis

The Wnt signaling pathway has critical roles in dysregulated inflammation during sepsis; however, its impacts on clinical outcomes remain uncertain. This prospective observational study investigated the association between the Wnt pathway and clinical outcomes in patients with urosepsis. The study included 38 patients with urosepsis and 20 healthy individuals. Wnt3a and Wnt5a levels were measured at admission. The primary outcome was the occurrence of major adverse kidney events (MAKE), defined as new renal replacement therapy, stage 3 acute kidney injury, or death. Both Wnt3a and Wnt5a levels were higher in the patient group than in the control (P = 0.001 and P < 0.001, respectively). The primary outcome occurred in 13 (34.2%) subjects. The levels of Wnt5a were higher in subjects with MAKE than in those without MAKE (P = 0.015); however, Wnt3a levels showed no significant difference. Moreover, Wnt5a levels could be a marker to predict the possibility of MAKE (area under the curve 0.74 [0.57-0.92]; P = 0.016). Serum creatinine levels on day 0, day 5, and on discharge day were evaluated. The levels of creatinine on discharge day were higher in patients with high Wnt5a levels, compared to those with low Wnt5a levels (P = 0.030); however, no difference in Wnt5a levels was observed on day 0 and 5. Wnt3a and Wnt5a levels increased in patients with urosepsis. Moreover, evaluation of Wnt5a levels might help to predict the occurrence of MAKE and renal recovery in these patients.

WNT10A Mutation Causes Ectodermal Dysplasia in a Patient Mosaic for Turner Syndrome

WNT10A plays a role in the proper proliferation and differentiation of ectodermal structures. Mutations in this gene can be responsible for a highly phenotypically variable range of disorders termed ectodermal dysplasias. Here, we describe the case of a five-year-old male patient who is mosaic for Turner syndrome (45,X [90%]/46,X isodicentric Y [10%]) and who presented to dermatology with anhidrosis, conical-shaped teeth, and a slowed rate of hair growth with genetic testing subsequently revealing a likely pathogenic heterozygous variant in WNT10A (c.682T>A; p.Phe228Ile). Future investigation into the WNT10A pathway, which is regulated downstream by β-catenin, might allow topical therapeutics to be developed that promote normal ectodermal growth and differentiation. Current management for this patient includes precautions taken to prevent overheating and heat stroke and close dermatological and dental monitoring.

In-vitro investigation of calcitonin associated effects on the trophoblastic cells

Calcitonin is expressed in the epithelium of endometrium, and modulates zonula adherens junctions which are composed of cadherin-catenins complex during the implantation window. Trophoblastic cells which have complex interaction with the epithelial cells of endometrium during implantation were demonstrated to have calcitonin receptors. Mechanism of action of calcitonin on trophoblastic cells has not yet been elucidated. Therefore, it was aimed to determine the effects of calcitonin on the expressions of β-catenin and phospho-β-catenin in a dose depended manner under the influence of progesterone and estrogen hormones (P + E) by using JAR cell line through the immunocytochemical and Western blot analyses. Moreover, adherens junctions (AJs) were ultrastructurally investigated to assess the involvement of cadherin-catenin complex in accordance with the changes in the specified parameters. Immunocytochemical analysis showed that only 10 nM calcitonin treated group had increased expression of membranous β-catenin compared to the control group, while there was decreased expression of β-catenin in the nucleus of all the experimental groups. Cytoplasmic expressions of the phospho-β-catenin decreased in all experimental groups compared to the control group while the decrease in the nuclear expression was remarkable in the groups treated with P + E, and P + E + 250 nM calcitonin. Western blot analysis showed that total β-catenin and phospho-β-catenin expressions were not significantly different. Ultrastructural analysis showed that increase in the number of AJs was noticeable in the group treated with 10 nM calcitonin. Overall, the localization and expression levels of β-catenin and phospho-β-catenin suggest that calcitonin could show its effects through the non-canonical pathway in the trophoblastic cells.

More Favorable Palmitic Acid Over Palmitoleic Acid Modification of Wnt3 Ensures Its Localization and Activity in Plasma Membrane Domains

While the lateral organization of plasma membrane components has been shown to control binding of Wnt ligands to their receptors preferentially in the ordered membrane domains, the role of posttranslational lipid modification of Wnt on this selective binding is unknown. Here, we identify that the canonical Wnt is presumably acylated by palmitic acid, a saturated 16-carbon fatty acid, at a conserved serine residue. Acylation of Wnt3 is dispensable for its secretion and binding to Fz8 while it is essential for Wnt3's proper binding and domain-like diffusion in the ordered membrane domains. We further unravel that non-palmitoylated Wnt3 is unable to activate Wnt/β-catenin signaling either in zebrafish embryos or in mammalian cells. Based on these results, we propose that the lipidation of canonical Wnt, presumably by a saturated fatty acid, determines its competence in interacting with the receptors in the appropriate domains of the plasma membrane, ultimately keeping the signaling activity under control.

WNT Signaling in Disease

Developmental signaling pathways control a vast array of biological processes during embryogenesis and in adult life. The WNT pathway was discovered simultaneously in cancer and development. Recent advances have expanded the role of WNT to a wide range of pathologies in humans. Here, we discuss the WNT pathway and its role in human disease and some of the advances in WNT-related treatments.

Molecular Mechanisms Associated with ROR1-Mediated Drug Resistance: Crosstalk with Hippo-YAP/TAZ and BMI-1 Pathways

Signaling via the Wnt-related receptor tyrosine kinase-like orphan receptor 1 (ROR1) triggers tumorigenic features associated with cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT), while aberrant expression of ROR1 is strongly linked to advanced disease progression and chemoresistance. Several recent studies have shown that Wnt5a binding to ROR1 promotes oncogenic signaling by activating multiple pathways such as RhoA/Rac1 GTPases and PI3K/AKT, which in turn could induce transcriptional coactivator YAP/TAZ or polycomb complex protein BMI-1 signaling, respectively, to sustain stemness, metastasis and ultimately drug-resistance. These data point towards a new feedback loop during cancer development, linking Wnt5a-ROR1 signaling activation to YAP/TAZ or BMI-1 upregulation that could play an important role in disease progression and treatment resistance. This review focuses on the crosstalk between Wnt5a-ROR1 and YAP/TAZ or the BMI-1 signaling network, together with the current advancements in targeted strategies for ROR1-positive cancers.

Cellular effects of diquat dibromide exposure: Interference with Wnt signaling and cytoskeletal development

The herbicidal action of diquat dibromide (DD) on plant cells is due primarily to the initiation of reactive oxygen species (ROS) formation, lipoperoxidation, and apoptotic cell death. It has been demonstrated that oxidative stress also occurs in animal cells exposed to high concentrations of DD; however, observations of DD’s effects on animal cells at concentrations below the reported ROS-initiation threshold suggest that some of these effects may not be attributable to ROS-induced cell death. Our results suggest that DD causes disruption of the Wnt pathway, calcium dysregulation, and cytoskeletal damage during development. Using embryos of the pond snail Lymnaea palustris as our model organism, we observed increased mortality, developmental delay and abnormality, altered motility, calcium dysregulation, decreased heart rate, and arrhythmia in embryos exposed to DD. Sperm extracted from adult snails that were exposed to DD exhibit altered motility, increased abundance, and high mortality. Effects were quantified via real-time imaging, heart rate assessment, flow cytometry, and mortality scoring. We propose that there are two models for the mechanism of DD’s action in animal cells: at low concentrations (≤28 µg/L), apoptotic cell death does not occur, but cytoskeletal elements, calcium regulation, and Wnt signaling are compromised, causing irreversible damage in L. palustris embryos; such damage is partially remediated with antioxidants or lithium chloride. At high concentrations of DD (≥44.4 µg/L), calcium dysregulation may be triggered, leading to the establishment of an intracellular positive feedback loop of ROS formation in the mitochondria, calcium release from the endoplasmic reticulum, calcium efflux, and apoptotic cell death. Permanent cellular damage occurring from exposure to sublethal concentrations of this widespread herbicide underscores the importance of research that elucidates the mechanism of DD on nontarget organisms.

Sfrp4 repression of the Ror2/Jnk cascade in osteoclasts protects cortical bone from excessive endosteal resorption

Loss-of-function mutations in the Wnt inhibitor secreted frizzled receptor protein 4 (SFRP4) cause Pyle's disease (OMIM 265900), a rare skeletal disorder characterized by wide metaphyses, significant thinning of cortical bone, and fragility fractures. In mice, we have shown that the cortical thinning seen in the absence of Sfrp4 is associated with decreased periosteal and endosteal bone formation and increased endocortical resorption. While the increase in Rankl/Opg in cortical bone of mice lacking Sfrp4 suggests an osteoblast-dependent effect on endocortical osteoclast (OC) activity, whether Sfrp4 can cell-autonomously affect OCs is not known. We found that Sfrp4 is expressed during bone marrow macrophage OC differentiation and that Sfrp4 significantly suppresses the ability of early and late OC precursors to respond to Rankl-induced OC differentiation. Sfrp4 deletion in OCs resulted in activation of canonical Wnt/β-catenin and noncanonical Wnt/Ror2/Jnk signaling cascades. However, while inhibition of canonical Wnt/β-catenin signaling did not alter the effect of Sfrp4 on OCgenesis, blocking the noncanonical Wnt/Ror2/Jnk cascade markedly suppressed its regulation of OC differentiation in vitro. Importantly, we report that deletion of Ror2 exclusively in OCs (CtskCreRor2 ^fl/fl ) in Sfrp4 null mice significantly reversed the increased number of endosteal OCs seen in these mice and reduced their cortical thinning. Altogether, these data show autocrine and paracrine effects of Sfrp4 in regulating OCgenesis and demonstrate that the increase in endosteal OCs seen in Sfrp4 ^-/- mice is a consequence of noncanonical Wnt/Ror2/Jnk signaling activation in OCs overriding the negative effect that activation of canonical Wnt/β-catenin signaling has on OCgenesis.

Triazole-Based Inhibitors of the Wnt/β-Catenin Signaling Pathway Improve Glucose and Lipid Metabolisms in Diet-Induced Obese Mice

Wnt/β-catenin signaling pathway is implicated in the etiology and progression of metabolic disorders. Although lines of genetic evidence suggest that blockage of this pathway yields favorable outcomes in treating such ailments, few inhibitors have been used to validate the promising genetic findings. Here, we synthesized and characterized a novel class of triazole-based Wnt/β-catenin signaling inhibitors and assessed their effects on energy metabolism. One of the top inhibitors, compound 3a, promoted Axin stabilization, which led to the proteasome degradation of β-catenin and subsequent inhibition of the Wnt/β-catenin signaling in cells. Treatment of hepatocytes and high fat diet-fed mice with compound 3a resulted in significantly decreased hepatic lipid accumulation. Moreover, compound 3a improved glucose tolerance of high fat diet-fed mice without noticeable toxicity, while downregulating the genes involved in the glucose and fatty acid anabolisms. The new inhibitors are expected to be further developed for the treatment of metabolic disorders.

Wnt Pathway in Bone Repair and Regeneration - What Do We Know So Far

Wnt signaling plays a central regulatory role across a remarkably diverse range of functions during embryonic development, including those involved in the formation of bone and cartilage. Wnt signaling continues to play a critical role in adult osteogenic differentiation of mesenchymal stem cells. Disruptions in this highly-conserved and complex system leads to various pathological conditions, including impaired bone healing, autoimmune diseases and malignant degeneration. For reconstructive surgeons, critically sized skeletal defects represent a major challenge. These are frequently associated with significant morbidity in both the recipient and donor sites. The Wnt pathway is an attractive therapeutic target with the potential to directly modulate stem cells responsible for skeletal tissue regeneration and promote bone growth, suggesting that Wnt factors could be used to promote bone healing after trauma. This review summarizes our current understanding of the essential role of the Wnt pathway in bone regeneration and repair.

XAV939, a Wnt/β-catenin pathway modulator, has inhibitory effects on LPS-induced inflammatory response

Aim: In this study, we report the anti-inflammatory activity of XAV939, a modulator of the Wnt/β-catenin pathway. Methods: WNT/β-catenin pathway and NF-κB signaling pathway were examined in LPS-stimulated human bronchial epithelial cells and effects of XAV939 on these pathways were analyzed. The effect of XAV939 was confirmed in human umbilical vein endothelial cells. Results: LPS-induced expressions of pro-inflammatory genes IL-6, IL-8, TNF-α, IL-1β, MCP-1, MMP-9, iNOS and COX-2 were significantly and dose-dependently suppressed by XAV939. LPS-induced NF-κB signaling, such as IκB phosphorylation and degradation as well as nuclear translocation of NF-κB, was also suppressed by XAV939. Target DNA binding of NF-κB was significantly and dose-dependently suppressed by XAV939 during LPS-induced inflammatory response. The suppressive effects of XAV939 on NF-κB signaling, target DNA binding of NF-κB and pro-inflammatory gene expression were all rescued by over expression of β-catenin, which shows that the anti-inflammatory effect of XAV939 is mediated by the modulation of β-catenin, a central component of the WNT/β-catenin pathway. Conclusion: The findings of this study showed that XAV939 exerts anti-inflammatory effects through the modulation of the Wnt/β-catenin pathway.

Design, synthesis and structure-activity relationship optimization of phenanthridine derivatives as new Wnt/β-catenin signalling pathway agonists

Phenanthridine derivativeHLY78 has previously been identified as the first Wnt/β-catenin signalling pathway agonist that targets the DAX domain of axin. However, due to the relatively weak activation on the Wnt/β-catenin signalling pathway, HLY78 is insufficient for further pharmacological study. Herein, the structural optimization of HLY78 and analyses of the structure-activity relationships (SARs) of HLY78-derived phenanthridine derivatives as agonists of the Wnt/β-catenin signalling pathway are presented. In this work, 36 derivatives were designed and synthesized with some derivatives exhibiting stronger Wnt activity than the activity of HLY78. In particular, one of them, 8-((1,3-dimethy-pyrazol-5-yl)methoxy)-5-ethyl-4-methyl-5,6-dihydro-phenanthridin-9-ol, exhibited strong Wnt active activity and is 10 times more potent than HLY78. The following SAR analysis suggests that a pyrazole group, especially at the C-8 position, is important for Wnt activation; a methyl group at the C-4position seems to be more beneficial for Wnt activation than ethyl; and oxidation of the C-6 position reduces the Wnt activation.

Effect of ghost pepper on cell proliferation, apoptosis, senescence and global proteomic profile in human renal adenocarcinoma cells

Chili peppers are an important constituent of many foods and contain medicinally valuable compounds, such as capsaicin and dihydrocapsaicin. As various dietary botanicals have anticancer properties, this study was aimed to examine the effect of Ghost pepper (Bhut Jolokia), one of the hottest chili peppers in the world, on cell proliferation, apoptosis, senescence and the global proteomic profile in human renal cell adenocarcinoma in vitro. 769-P human renal adenocarcinoma cells were cultured on RPMI-1640 media supplemented with fetal bovine serum (10%) and antibiotic-antimycotic solution (1%). Treatment stock solutions were prepared in ethanol. Cell proliferation was tested with phenol red-free media with capsaicin (0-400 μM), dihydrocapsaicin (0-400 μM), capsaicin + dihydrocapsaicin (5:1), and dry Ghost peppers (0-3 g L-1) for 24, 48 and 72 h. Polycaspase and senescence associated-beta-galactosidase (SA-beta-gal) activities were tested with capsaicin (400 μM), dihydrocapsaicin (400 μM), capsaicin (400 μM) + dihydrocapsaicin (80 μM), and ghost pepper (3 g L-1) treatments. Global proteomic profile of cells in control and ghost pepper treatment (3 g L-1) was analyzed after 6 h by a shotgun proteomic approach using tandem mass spectrometry. At 24 h after treatment (24 HAT), relative to control, cell proportion with capsaicin (400 μM), dihydrocapsaicin (400 μM), capsaicin (400 μM) + dihydrocapsaicin (80 μM), and ghost pepper (3 g L-1) treatments was reduced to 36%, 18%, 33% and 20%, respectively, and further reduced at 48 and 72 HAT. All treatments triggered an early polycaspase response. SA-beta-gal activity was normal or suppressed with all treatments. About 68,220 protein isoforms were identified by shotgun proteomic approach. Among these, about 8.2% were significantly affected by ghost pepper. Ghost pepper regulated various proteins involved in intrinsic and extrinsic apoptotic pathways, Ras, Rb/E2F, p53, TGF-beta, WNT-beta catenin, and calcium induced cell death pathways. Ghost pepper also induced changes in proteins related to methylation, acetylation, genome stability, cell cycle check points, carbohydrate, protein and other metabolism and cellular mechanisms. Ghost pepper exhibited antiproliferation activity by inducing apoptosis through a complex network of proteins in human renal cell adenocarcinoma in vitro.

A molecular mechanism for Wnt ligand-specific signaling

Wnt signaling is key to many developmental, physiological, and disease processes in which cells seem able to discriminate between multiple Wnt ligands. This selective Wnt recognition or "decoding" capacity has remained enigmatic because Wnt/Frizzled interactions are largely incompatible with monospecific recognition. Gpr124 and Reck enable brain endothelial cells to selectively respond to Wnt7. We show that Reck binds with low micromolar affinity to the intrinsically disordered linker region of Wnt7. Availability of Reck-bound Wnt7 for Frizzled signaling relies on the interaction between Gpr124 and Dishevelled. Through polymerization, Dishevelled recruits Gpr124 and the associated Reck-bound Wnt7 into dynamic Wnt/Frizzled/Lrp5/6 signalosomes, resulting in increased local concentrations of Wnt7 available for Frizzled signaling. This work provides mechanistic insights into the Wnt decoding capacities of vertebrate cells and unravels structural determinants of the functional diversification of Wnt family members.

Low penetrance genetic polymorphisms as potential biomarkers for colorectal cancer predisposition

Colorectal cancer is a leading form of cancer in both males and females. Early detection of individuals at risk of colorectal cancer allows proper treatment and management of the disease to be implemented, which can potentially reduce the burden of colorectal cancer incidence, morbidity and mortality. In recent years, the role of genetic susceptibility factors in mediating predisposition to colorectal cancer has become more and more apparent. Identification of high-frequency, low-penetrance genetic polymorphisms associated with the cancer has therefore emerged as an important approach which can potentially aid prediction of colorectal cancer risk. However, the overwhelming amount of genetic epidemiology data generated over the past decades has made it difficult for one to assimilate the information and determine the exact genetic polymorphisms that can potentially be used as biomarkers for colorectal cancer. This review comprehensively consolidates, based primarily on results from meta-analyses, the recent progresses in the search of colorectal cancer-associated genetic polymorphisms, and discusses the possible mechanisms involved.

Targeting XBP1-mediated β-catenin expression associated with bladder cancer with newly synthetic Oridonin analogues

Conventional chemotherapy is commonly used for advanced stages of transitional cell carcinoma (TCC) with modest success and high morbidity; however, TCC eventually develops resistance. Muscle invasive bladder cancer (MIBC) is recognized as a lethal disease due to its poor response to traditional chemotherapy. Numerous studies have implicated β-catenin, a critical effector in Wnt–mediated pathway associated with epithelial-mesenchymal transition and cancer stem cell, is involved in TCC progression, and furthermore closely associated with chemo-resistance. In this study, we discovered a novel natural product analogue CYD 6-17 that has a potent inhibitory effect on TCC cells exhibiting drug resistance to various chemotherapeutics, with an IC₅₀ at nM range. Delivery of CYD 6-17 significantly inhibited the tumor growth using xenograft model but without detectable side effects. Mechanistically, it targeted β-catenin gene transcription by decreasing the binding of XBP1 to the promoter region, which appeared to be a new regulatory mechanism for β-catenin gene expression. Clinically, XBP1 expression correlated with the poor overall survival of patients. Overall, this study unveils unique mechanism of β-catenin gene regulation in advanced TCC and also offers a potential rational therapeutic regimen to MIBC.

Tissue Engineering Functional Gastrointestinal Regions: The Importance of Stem and Progenitor Cells

The intestine shows extraordinary regenerative potential that might be harnessed to alleviate numerous morbid and lethal human diseases. The intestinal stem cells regenerate the epithelium every 5 days throughout an individual's lifetime. Understanding stem-cell signaling affords power to influence the niche environment for growing intestine. The manifold approaches to tissue engineering may be organized by variations of three basic components required for the transplantation and growth of stem/progenitor cells: (1) cell delivery materials or scaffolds; (2) donor cells including adult stem cells, induced pluripotent stem cells, and in vitro expansion of isolated or cocultured epithelial, smooth muscle, myofibroblasts, or nerve cells; and (3) environmental modulators or biopharmaceuticals. Tissue engineering has been applied to the regeneration of every major region of the gastrointestinal tract from esophagus to colon, with scientists around the world aiming to carry these techniques into human therapy.

Wnt signalling modulates transcribed-ultraconserved regions in hepatobiliary cancers

OBJECTIVE

Transcribed-ultraconserved regions (T-UCR) are long non-coding RNAs which are conserved across species and are involved in carcinogenesis. We studied T-UCRs downstream of the Wnt/β-catenin pathway in liver cancer.

DESIGN

Hypomorphic Apc mice (Apcfl/fl) and thiocetamide (TAA)-treated rats developed Wnt/β-catenin dependent hepatocarcinoma (HCC) and cholangiocarcinoma (CCA), respectively. T-UCR expression was assessed by microarray, real-time PCR and in situ hybridisation.

RESULTS

Overexpression of the T-UCR uc.158- could differentiate Wnt/β-catenin dependent HCC from normal liver and from β-catenin negative diethylnitrosamine (DEN)-induced HCC. uc.158- was overexpressed in human HepG2 versus Huh7 cells in line with activation of the Wnt pathway. In vitro modulation of β-catenin altered uc.158- expression in human malignant hepatocytes. uc.158- expression was increased in CTNNB1-mutated human HCCs compared with non-mutated human HCCs, and in human HCC with nuclear localisation of β-catenin. uc.158- was increased in TAA rat CCA and reduced after treatment with Wnt/β-catenin inhibitors. uc.158- expression was negative in human normal liver and biliary epithelia, while it was increased in human CCA in two different cohorts. Locked nucleic acid-mediated inhibition of uc.158- reduced anchorage cell growth, 3D-spheroid formation and spheroid-based cell migration, and increased apoptosis in HepG2 and SW1 cells. miR-193b was predicted to have binding sites within the uc.158- sequence. Modulation of uc.158- changed miR-193b expression in human malignant hepatocytes. Co-transfection of uc.158- inhibitor and anti-miR-193b rescued the effect of uc.158- inhibition on cell viability.

CONCLUSIONS

We showed that uc.158- is activated by the Wnt pathway in liver cancers and drives their growth. Thus, it may represent a promising target for the development of novel therapeutics.

Brain glucose metabolism: Role of Wnt signaling in the metabolic impairment in Alzheimer's disease

The brain is an organ that has a high demand for glucose. In the brain, glucose is predominantly used in energy production, with almost 70% of the energy used by neurons. The importance of the energy requirement in neurons is clearly demonstrated by the fact that all neurodegenerative disorders exhibit a critical metabolic impairment that includes decreased glucose uptake/utilization and decreased mitochondrial activity, with a consequent diminution in ATP production. In fact, in Alzheimer's disease, the measurement of the general metabolic rate of the brain has been reported to be an accurate tool for diagnosis. Additionally, the administration of metabolic activators such as insulin/glucagon-like peptide 1 can improve memory/learning performance. Despite the importance of energy metabolism in the brain, little is known about the cellular pathways involved in the regulation of this process. Several reports postulate a role for Wnt signaling as a general metabolic regulator. Thus, in the present review, we discuss the antecedents that support the relationship between Wnt signaling and energy metabolism in the Alzheimer's disease.

KLK4 silencing inhibits the growth of oral squamous cell carcinoma through Wnt/β-catenin signaling pathway

Oral squamous cell carcinoma (OSCC) is a malignancy that largely impacts the quality of people's daily life. Kallikrein-related peptidase 4 (KLK4) is highly expressed in OSCC; however, its roles in OSCC cells are unclear. In the present study, the effect of KLK4 silencing on the growth of OSCC cells was investigated. Our study showed that the proliferation and colony formation of OSCC cells was inhibited by KLK4 silencing and their cell cycle was arrested. Additionally, apoptosis of OSCC cells was enhanced by KLK4 silencing, with increased protein levels of cleaved PARP, cleaved caspase-3, Bax and decreased levels of Bcl-2. KLK4 silencing inhibited the Wnt/β-catenin signaling pathway, as evidence by decreased protein levels of Wnt1, β-catenin, reduced GSK-3β phosphorylation as well as decreased levels of cyclinD1 and c-myc proteins. We further showed that Wnt/β-catenin activator reversed the effects of KLK4 silencing on the proliferation and apoptosis of OSCC cells. We concluded that KLK4 silencing inhibited the growth of OSCC cells through Wnt/β-catenin signaling pathway, suggesting that KLK4 may become a promising therapeutic target for the treatment of OSCC.

Chemical biology reveals CARF as a positive regulator of canonical Wnt signaling by promoting TCF/β-catenin transcriptional activity

Wnt/β-catenin signaling regulates multiple biological processes and aberration of this pathway is frequently observed in human cancers. Previously, we uncovered NC043 as a small-molecule inhibitor of Wnt/β-catenin signaling. Here, we identified CARF as the cellular target of NC043. We found that NC043 binds directly to CARF through forming a covalent bond with the Cys-516 residue of CARF. Further study revealed that CARF interacts with Dvl, which potentiates the Dvl-c-Jun-β-catenin-TCF transcriptional complex and thus promotes Wnt signaling activation. NC043 could disrupt the interaction between CARF and Dvl, thereby impairing Wnt signal transduction. In line with this, knockdown of CARF in zebrafish leads to impairment of embryonic development, hematopoietic stem cell generation and caudal fin regeneration. Collectively, we identified CARF as the cellular target of NC043 and revealed CARF as a positive regulator of Wnt/β-catenin signal transduction.

Development of a triazole class of highly potent Porcn inhibitors

The acyltransferase Porcupine (Porcn) is essential for the secretion of Wnt proteins which contribute to embryonic development, tissue regeneration, and tumorigenesis. We have previously discovered four molecular scaffolds harboring Porcn-inhibitory activity. Comparison of their structures led to the identification of a general scaffold that can be readily assembled by modular synthesis. We report herein the development of a triazole version of this new class of Porcn inhibitors. This study yielded IWP-O1, a Porcn inhibitor with an EC₅₀ value of 80pM in a cultured cell reporter assay of Wnt signaling. Additionally, IWP-O1 has significantly improved metabolic stability over our previously reported Porcn inhibitors.

Wnt Drug Discovery: Weaving Through the Screens, Patents and Clinical Trials

The Wnt signaling pathway is intricately involved in many aspects of development and is the root cause of an increasing number of diseases. For example, colorectal cancer is the second leading cause of death in the industrialized world and aberration of Wnt signaling within the colonic stem cell is the cause of more than 90% of these cancers. Despite our advances in successfully targeting other pathways, such as Human Epidermal Growth Factor Receptor 2 (HER2), there are no clinically relevant therapies available for Wnt-related diseases. Here, we investigated where research activities are focused with respect to Wnt signaling modulators by searching the United States Patent and Trade Office (USPTO) for patents and patent applications related to Wnt modulators and compared this to clinical trials focusing on Wnt modulation. We found that while the transition of intellectual property surrounding the Wnt ligand-receptor interface to clinical trials is robust, this is not true for specific inhibitors of β-catenin, which is constitutively active in many cancers. Considering the ubiquitous use of the synthetic T-cell Factor/Lymphoid Enhancer Factor (TCF/Lef) reporter system and its success in identifying novel modulators in vitro, we speculate that this model of drug discovery does not capture the complexity of in vivo Wnt signaling that may be required if we are to successfully target the Wnt pathway in the clinic. Notwithstanding, increasingly more complex models are being developed, which may not be high throughput, but more pragmatic in our pursuit to control Wnt signaling.

Gtpbp2 is a positive regulator of Wnt signaling and maintains low levels of the Wnt negative regulator Axin

Background

Canonical Wnt signals, transduced by stabilized β-catenin, play similar roles across animals in maintaining stem cell pluripotency, regulating cell differentiation, and instructing normal embryonic development. Dysregulated Wnt/β-catenin signaling causes diseases and birth defects, and a variety of regulatory processes control this pathway to ensure its proper function and integration with other signaling systems. We previously identified GTP-binding protein 2 (Gtpbp2) as a novel regulator of BMP signaling, however further exploration revealed that Gtpbp2 can also affect Wnt signaling, which is a novel finding reported here.

Results

Knockdown of Gtpbp2 in Xenopus embryos causes severe axial defects and reduces expression of Spemann-Mangold organizer genes. Gtpbp2 knockdown blocks responses to ectopic Wnt8 ligand, such as organizer gene induction in ectodermal tissue explants and induction of secondary axes in whole embryos. However, organizer gene induction by ectopic Nodal2 is unaffected by Gtpbp2 knockdown. Epistasis tests, conducted by activating Wnt signal transduction at sequential points in the canonical pathway, demonstrate that Gtpbp2 is required downstream of Dishevelled and Gsk3β but upstream of β-catenin, which is similar to the previously reported effects of Axin1 overexpression in Xenopus embryos. Focusing on Axin in Xenopus embryos, we find that knockdown of Gtpbp2 elevates endogenous or exogenous Axin protein levels. Furthermore, Gtpbp2 fusion proteins co-localize with Dishevelled and co-immunoprecipitate with Axin and Gsk3b.

Conclusions

We conclude that Gtpbp2 is required for canonical Wnt/β-catenin signaling in Xenopus embryos. Our data suggest a model in which Gtpbp2 suppresses the accumulation of Axin protein, a rate-limiting component of the β-catenin destruction complex, such that Axin protein levels negatively correlate with Gtpbp2 levels. This model is supported by the similarity of our Gtpbp2-Wnt epistasis results and previously reported effects of Axin overexpression, the physical interactions of Gtpbp2 with Axin, and the correlation between elevated Axin protein levels and lost Wnt responsiveness upon Gtpbp2 knockdown. A wide variety of cancer-causing Wnt pathway mutations require low Axin levels, so development of Gtpbp2 inhibitors may provide a new therapeutic strategy to elevate Axin and suppress aberrant β-catenin signaling in cancer and other Wnt-related diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-016-0138-x) contains supplementary material, which is available to authorized users.

Increased Dickkopf-1 expression is correlated with poisoning severity in carbon monoxide-poisoned humans and rats

CONTEXT

Carbon monoxide (CO) poisoning results in neuronal injury. The expression of Dickkopf-1 (DKK-1) has not been investigated previously after CO poisoning.

OBJECTIVE

The current study aimed to investigate the DKK-1 expression levels in humans and rats with acute CO poisoning and to analyze their correlation with poisoning severity.

MATERIALS AND METHODS

We measured serum DKK-1 levels in patients with acute CO poisoning (n = 94) and in healthy controls (n = 90). On admission, a poisoning severity score (PSS) was determined for each patient. In addition, 36 male Sprague-Dawley rats were randomly assigned into three groups: (a) Sham group, (b) Low CO group and (c) High CO group. At 2 h after CO poisoning, DKK-1 expression and histopathological damage in the hippocampal tissues were measured.

RESULTS

Serum DKK-1 levels were significantly higher in the acute CO-poisoned patients, compared to the healthy controls. Serum DKK-1 levels were significantly higher in the CO-poisoned patients with a lower PSS. In rats, CO poisoning induced significant upregulation of the gene and protein expression of DKK-1 in hippocampal tissues. Moreover, there was a positive correlation between DKK-1 levels and the degree of damage in the hippocampal tissues.

DISCUSSION

DKK-1 induction in neurons after CO poisoning causes further neuronal injury. The severity of acute CO poisoning in rat models is associated with elevated serum DKK-1 levels and its upregulation in the brain tissue.

CONCLUSION

DKK-1 appears to have potential utility in providing valuable information for determining the severity and damage of CO poisoning.

Chemical Disruption of Wnt-dependent Cell Fate Decision-making Mechanisms in Cancer and Regenerative Medicine

Cell-to-cell signaling molecules such as the Wnt proteins that directly influence the expression of cell-type specific transcriptional programs are essential for tissue generation in metazoans. The mechanisms supporting cellular responses to these molecules represent potential points of intervention for directing cell fate outcomes in therapeutic contexts. Small molecules that modulate Wnt-mediated cellular responses have proven to be powerful probes for Wnt protein function in diverse biological settings including cancer, development, and regeneration. Whereas efforts to develop these chemicals as therapeutic agents have dominated conversation, the unprecedented modes-of-action associated with these molecules and their implications for drug development deserve greater examination. In this review, we will discuss how medicinal chemistry efforts focused on first in class small molecules targeting two Wnt pathway components--the polytopic Porcupine (Porcn) acyltransferase and the cytoplasmic Tankyrase (Tnks) poly-ADP-ribosylases--have contributed to our understanding of the druggable genome and expanded the armamentarium of chemicals that can be used to influence cell fate decision-making.

TCF7L1 Modulates Colorectal Cancer Growth by Inhibiting Expression of the Tumor-Suppressor Gene EPHB3

Dysregulation of the Wnt pathway leading to accumulation of β-catenin (CTNNB1) is a hallmark of colorectal cancer (CRC). Nuclear CTNNB1 acts as a transcriptional coactivator with TCF/LEF transcription factors, promoting expression of a broad set of target genes, some of which promote tumor growth. However, it remains poorly understood how CTNNB1 interacts with different transcription factors in different contexts to promote different outcomes. While some CTNNB1 target genes are oncogenic, others regulate differentiation. Here, we found that TCF7L1, a Wnt pathway repressor, buffers CTNNB1/TCF target gene expression to promote CRC growth. Loss of TCF7L1 impaired growth and colony formation of HCT116 CRC cells and reduced tumor growth in a mouse xenograft model. We identified a group of CTNNB1/TCF target genes that are activated in the absence of TCF7L1, including EPHB3, a marker of Paneth cell differentiation that has also been implicated as a tumor suppressor in CRC. Knockdown of EPHB3 partially restores growth and normal cell cycle progression of TCF7L1-Null cells. These findings suggest that while CTNNB1 accumulation is critical for CRC progression, activation of specific Wnt target genes in certain contexts may in fact inhibit tumor growth.

WINGLESS (WNT) signaling is a progesterone target for rat uterine stromal cell proliferation

Preparation of mammalian uterus for embryo implantation requires a precise sequence of cell proliferation. In rodent uterus, estradiol stimulates proliferation of epithelial cells. Progesterone operates as a molecular switch and redirects proliferation to the stroma by down-regulating glycogen synthase kinase-3β (GSK-3β) and stimulating β-catenin accumulation in the periluminal stromal cells. In this study, the WNT signal involved in the progesterone-dependent proliferative switch was investigated. Transcripts of four candidate Wnt genes were measured in the uteri from ovariectomized (OVX) rats, progesterone-pretreated (3 days of progesterone, 2mg/daily) rats, and progesterone-pretreated rats given a single dose (0.2µg) of estradiol. The spatial distribution of the WNT proteins was determined in the uteri after the same treatments. Wnt5a increased in response to progesterone and the protein emerged in the periluminal stromal cells of progesterone-pretreated rat uteri. To investigate whether WNT5A was required for proliferation, uterine stromal cell lines were stimulated with progesterone (1µM) and fibroblast growth factor (FGF, 50ng/mL). Proliferating stromal cells expressed a two-fold increase in WNT5A protein at 12h post stimulation. Stimulated stromal cells were cultured with actinomycin D (25µg/mL) to inhibit new RNA synthesis. Relative Wnt5a expression increased at 4 and 6 h of culture, suggesting that progesterone plus FGF preferentially increased Wnt5a mRNA stability. Knockdown of Wnt5a in uterine stromal cell lines inhibited stromal cell proliferation and decreased Wnt5a mRNA. The results indicate that progesterone initiates and synchronizes uterine stromal cell proliferation by increasing WNT5A expression and signaling.

Active and water-soluble form of lipidated Wnt protein is maintained by a serum glycoprotein afamin/α-albumin

Wnt plays important role during development and in various diseases. Because Wnts are lipidated and highly hydrophobic, they can only be purified in the presence of detergents, limiting their use in various in vitro and in vivo assays. We purified N-terminally tagged recombinant Wnt3a secreted from cells and accidentally discovered that Wnt3a co-purified with a glycoprotein afamin derived from the bovine serum included in the media. Wnt3a forms a 1:1 complex with afamin, which remains soluble in aqueous buffer after isolation, and can induce signaling in various cellular systems including the intestical stem cell growth assay. By co-expressing with afamin, biologically active afamin-Wnt complex can be easily obtained in large quantity. As afamin can also solubilize Wnt5a, Wnt3, and many more Wnt subtypes, afamin complexation will open a way to put various Wnt ligands and their signaling mechanisms under a thorough biochemical scrutiny that had been difficult for years.

DOI:http://dx.doi.org/10.7554/eLife.11621.001

The Wnt signaling pathway helps animal cells to communicate with each other to coordinate the formation of tissues and organs. The pathway relies on a protein called Wnt that is released from cells and binds to a receptor protein called Frizzled on the surface of other cells to trigger changes in gene activation. Defects in the Wnt signaling pathway contribute to cancer and other diseases.

Great progress has been made in understanding Wnt signaling, but certain types of experiments have been hindered because it has been difficult to isolate pure Wnt proteins. This is partly because Wnt proteins are attached to a fatty molecule that is important for their activity but also makes these proteins “hydrophobic,” or repelled by water.

Hydrophobic proteins have a strong tendency to clump or aggregate when they are isolated from cells, which reduces the biological activity of proteins. Adding detergents to the aggregates can break them apart, but can also hinder the proteins’ activities and cannot be used in all experiments. Previous research has shown that mammalian cells grown in the presence of blood serum can produce Wnt proteins that do not aggregate. Blood serum is a complex mixture of different molecules obtained from blood and is commonly added to cells grown in the laboratory. However, adding serum can have also undesirable effects and it is not understood why serum stops Wnt proteins forming aggregates.

Using biochemical methods, Mihara et al. have now identified the component in blood serum that prevents Wnt proteins from aggregating. The experiments showed that a protein in the blood serum called afamin binds tightly to Wnt proteins. Furthermore, the complex between afamin and Wnt was biologically active, and could bind to the Frizzled receptor and trigger an appropriate response in cells.

Mihara et al. then generated cells that produced both afamin and Wnt and used them to purify large amounts of biologically active Wnt/afamin complexes. This method avoids the potentially undesirable effects of using detergents or serum, and will therefore likely be useful for future experiments and therapeutic applications. Further work is also needed to understand why afamin binds to Wnt proteins and whether this is important for Wnt signaling.

DOI:http://dx.doi.org/10.7554/eLife.11621.002

Design, Synthesis, and Structural Optimization of Lycorine-Derived Phenanthridine Derivatives as Wnt/β-Catenin Signaling Pathway Agonists

Lycorine is a benzylphenethylamine-type alkaloid member of the Amaryllidaceae family. A lycorine derivative, HLY78, was previously identified as a new Wnt/β-catenin signaling pathway agonist that targets the DAX domain of axin. Herein, the structural optimization of HLY78 and analyses of the structure-activity relationships of lycorine-derived phenanthridine derivatives as agonists of the Wnt/β-catenin signaling pathway are presented. This research suggests that triazole groups are important pharmacophores for Wnt activation; triazole groups at C-8 and C-9 of phenanthridine compounds markedly enhanced Wnt activation. A C-11-C-12 single bond is also important for Wnt activation. On the basis of these findings, two Wnt agonists were designed and synthesized. The results for these agonists indicated that the combination of a 4-ethyldihydrophenanthridine skeleton and a triazole substituent improves Wnt activation. These compounds may be useful in further pharmacological or biological studies.