LDL receptor-related proteins 5 and 6 in Wnt/beta-catenin signaling: arrows point the way

Blocking the Dkk1-LRP6 interaction prevents acute amyloid-β-driven cognitive impairment

Synapse loss driven by amyloid-β (Aβ) is an early event in Alzheimer's disease (AD). Although the mechanism by which Aβ drives synapse loss remain poorly understood data indicate that a disruption of Wnt signalling plays an important part. We have shown that Aβ exerts its effects on synapses through Dickkopf-1 (Dkk1), a secreted protein that acts upon Wnt signalling via a direct interaction with the canonical Wnt pathway co-receptor proteins, LRP5 and LRP6, preventing their interaction with the receptor Frizzled. This antagonises canonical, Wnt/β-catenin, signalling and allows concomitant activation of non-canonical signalling pathways. We contend that it is the switch from canonical to non-canonical Wnt signalling activity that drives synapse loss and subsequent cognitive impairment in AD, driven by Aβ and mediated by Dkk1. Preventing the Dkk1-LRP5/6 interaction could protect synapses and cognition against Aβ by maintaining canonical Wnt signalling. To test this, we mapped the Dkk1-LRP6 interaction by peptide array and identified a small peptide able to disrupt the Dkk1-LRP6 interaction. This Dkk1-LRP6 'disruptor' peptide dose dependently restores canonical Wnt signalling in the presence of Dkk1; blocks Dkk1-driven dendritic spine loss in primary rat cortical cultures and the accompanying increase in endogenous Aβ production; and when administered intracerebroventricularly to a rat acute Aβ model, blocks Aβ-driven cognitive impairment. These data support our contention that the ability of Aβ to induce Dkk1 and the effects of Dkk1 on LRP6 are an important element in AD aetiopathology and establish Dkk1 as a therapeutic target for protecting synapse and cognition in AD.

Therapeutic targets in the Wnt signaling pathway: Treating cancer with specificity

The Wnt signaling pathway is a critical regulatory mechanism that governs cell cycle progression, apoptosis, epithelial-mesenchymal transition (EMT), angiogenesis, stemness, and the tumor immune microenvironment, while also maintaining tissue homeostasis. Dysregulated activation of this pathway is implicated in various cancers, closely linked to tumor initiation, progression, and metastasis. The Wnt/β-catenin axis plays a central role in the pathogenesis of common cancers, including colorectal cancer (CRC), breast cancer (BC), liver cancer, and lung cancer. Unlike traditional chemotherapy, targeted therapy offers a more precise approach to cancer treatment. As a key regulator of oncogenesis, the Wnt pathway represents a promising target for clinical interventions. This review provides a comprehensive analysis of the Wnt signaling pathway, exploring its roles in tumor biology and its implications in human malignancies. It further examines the molecular mechanisms and modes of action across different cancers, detailing how the Wnt pathway contributes to tumor progression through mechanisms such as metastasis promotion, immune modulation, drug resistance, and enhanced cellular proliferation. Finally, therapeutic strategies targeting Wnt pathway components are discussed, including inhibitors targeting extracellular members, as well as those within the cell membrane, cytoplasm, and nucleus. The potential of these targets in the development of novel therapeutic agents underscores the critical importance of intervening in the Wnt signaling pathway for effective cancer treatment.

Wnt signalosome assembly is governed by conformational flexibility of Axin and by the AP2 clathrin adaptor

Wnt signal transduction relies on the direct inhibition of GSK3 by phosphorylated PPPSPxS motifs within the cytoplasmic tail of the LRP6 co-receptor. How GSK3 is recruited to LRP6 remains unclear. Here, we use nuclear magnetic resonance spectroscopy to identify the membrane-proximal PPPSPxS motif and its flanking sequences as the primary binding site for both Axin and GSK3, and an intrinsically disordered segment of Axin as its LRP6-interacting region (LIR). Co-immunoprecipitation and CRISPR-engineered mutations in endogenous Axin indicate that its docking at LRP6 is antagonized by a phospho-dependent foldback within LIR and by a PRTxR motif that allows Axin and GSK3 to form a multi-pronged interaction which favors their detachment from LRP6. Crucially, signaling by LRP6 also depends on its binding to the AP2 clathrin adaptor. We propose that the Wnt-driven clustering of LRP6 within clathrin-coated locales allows the Axin-GSK complex to dock at adjacent LRP6 molecules, while also exposing it to co-targeted kinases that change its activity in Wnt signal transduction.

MEIS1 knockdown upregulates WNT signaling pathway genes in esophageal squamous cell carcinoma

BACKGROUND

The transcription factor MEIS1 belongs to the 3-amino acid loop extension (TALE) family of homeodomain proteins which plays various functions in normal and tumor cell progression. The canonical WNT/β-catenin pathway governs a plethora of biological processes including cell proliferation, differentiation, and tumor development. In the present study, the effect of MEIS1 gene silencing was assessed on WNT pathway genes in esophageal squamous cell carcinoma (ESCC) cells.

MATERIALS AND METHODS

Along with the packaging plasmids, the pLKO.1-MEIS1 plasmid was cotransfected into HEK293T to generate lentiviral particles, followed by transduction of a semi-confluent KYSE-30 cell culture. After total RNA extraction and cDNA synthesis, comparative real-time PCR was applied to assess the efficiency of MEIS1 knockdown and the expression of genes related to the WNT signaling pathway.

RESULTS

The results revealed effective downregulation of MEIS1 in KYSE-30 cells. Interestingly, MEIS1 silencing led to a substantial overexpression of WNT pathway key components while the expression of negative regulators of this pathway was substantially decreased.

CONCLUSIONS

Our data suggest that MEIS1 gene probably induces WNT/β-catenin pathway deactivation in ESCC cells. Consequently, the inverse correlation of MEIS1 expression and WNT signaling pathway activation may introduce a new molecular linkage through ESCC progression and aggressiveness.

Antifibrotic therapeutic strategies in systemic sclerosis: Critical role of the Wnt/β-catenin and TGF-β signal transduction pathways as potential targets

Systemic sclerosis (SSc) is a prototypic fibrosing disorder characterized by widespread fibrosis and immune dysregulation. Current evidence highlights the intricate cross-talk between the canonical Wnt/β-catenin signaling pathway and transforming growth factor-beta (TGF-β) signaling, both of which play fundamental roles in the pathogenesis of fibrosis. This review aims to elucidate the central role of the Wnt/β-catenin-TGF-β pathway and TGF-β signal transduction pathway in fibrotic diseases, focusing on SSc. We summarized evidence from cellular biology studies, animal model investigations and clinical observations to provide a comprehensive view of the mechanisms causing pathological fibrosis. In addition, we explore the possibilities of antifibrotic therapeutic strategies against Wnt/β-catenin-TGF-β signaling to counteract fibrosis, delineating approaches for treatment of SSc patients by targeting these interconnected signaling pathways.

Wnt signaling pathways in biology and disease: mechanisms and therapeutic advances

The Wnt signaling pathway is critically involved in orchestrating cellular functions such as proliferation, migration, survival, and cell fate determination during development. Given its pivotal role in cellular communication, aberrant Wnt signaling has been extensively linked to the pathogenesis of various diseases. This review offers an in-depth analysis of the Wnt pathway, detailing its signal transduction mechanisms and principal components. Furthermore, the complex network of interactions between Wnt cascades and other key signaling pathways, such as Notch, Hedgehog, TGF-β, FGF, and NF-κB, is explored. Genetic mutations affecting the Wnt pathway play a pivotal role in disease progression, with particular emphasis on Wnt signaling's involvement in cancer stem cell biology and the tumor microenvironment. Additionally, this review underscores the diverse mechanisms through which Wnt signaling contributes to diseases such as cardiovascular conditions, neurodegenerative disorders, metabolic syndromes, autoimmune diseases, and cancer. Finally, a comprehensive overview of the therapeutic progress targeting Wnt signaling was given, and the latest progress in disease treatment targeting key components of the Wnt signaling pathway was summarized in detail, including Wnt ligands/receptors, β-catenin destruction complexes, and β-catenin/TCF transcription complexes. The development of small molecule inhibitors, monoclonal antibodies, and combination therapy strategies was emphasized, while the current potential therapeutic challenges were summarized. This aims to enhance the current understanding of this key pathway.

Cardiac Fibroblasts: Helping or Hurting

Cardiac fibroblasts (CFs) are the essential cell type for heart morphogenesis and homeostasis. In addition to maintaining the structural integrity of the heart tissue, muscle fibroblasts are involved in complex signaling cascades that regulate cardiomyocyte proliferation, migration, and maturation. While CFs serve as the primary source of extracellular matrix proteins (ECM), tissue repair, and paracrine signaling, they are also responsible for adverse pathological changes associated with cardiovascular disease. Following activation, fibroblasts produce excessive ECM components that ultimately lead to fibrosis and cardiac dysfunction. Decades of research have led to a much deeper understanding of the role of CFs in cardiogenesis. Recent studies using the single-cell genomic approach have focused on advancing the role of CFs in cellular interactions, and the mechanistic implications involved during cardiovascular development and disease. Arguably, the unique role of fibroblasts in development, tissue repair, and disease progression categorizes them into the friend or foe category. This brief review summarizes the current understanding of cardiac fibroblast biology and discusses the key findings in the context of development and pathophysiological conditions.

Selective modulation of the bone remodeling regulatory system through orthodontic tooth movement-a review

Little is known about how tissues mediate the ability to selectively form or resorb bone, as required during orthodontic tooth movement (OTM), facial growth, continued tooth eruption and for healing after fractures, maxillofacial surgical repositioning or implant dentistry. OTM has the unique ability to selectively cause apposition, resorption or a combination of both at the alveolar periosteal surface and therefore, provides an optimal process to study the regulation of bone physiology at a tissue level. Our aim was to elucidate the mechanisms and signaling pathways of the bone remodeling regulatory system (BRRS) as well as to investigate its clinical applications in osteoporosis treatment, orthopedic surgery, fracture management and orthodontic treatment. OTM is restricted to a specific range in which the BRRS permits remodeling; however, surpassing this limit may lead to bone dehiscence. Low-intensity pulsed ultrasound, vibration or photobiomodulation with low-level laser therapy have the potential to modify BRRS with the aim of reducing bone dehiscence and apical root resorption or accelerating OTM. Unloading of bone and periodontal compression promotes resorption via receptor activator of nuclear factor κB-ligand, monocyte chemotactic protein-1, parathyroid hormone-related protein (PTHrP), and suppression of anti-resorptive mediators. Furthermore, proinflammatory cytokines, such as interleukin-1 (IL-1), IL-6, IL-8, tumor necrosis factor-α, and prostaglandins exert a synergistic effect on bone resorption. While proinflammatory cytokines are associated with periodontal sequelae such as bone dehiscence and gingival recessions, they are not essential for OTM. Integrins mediate mechanotransduction by converting extracellular biomechanical signals into cellular responses leading to bone apposition. Active Wnt signaling allows β-catenin to translocate into the nucleus and to stimulate bone formation, consequently converging with integrin-mediated mechanotransductive signals. During OTM, periodontal fibroblasts secrete PTHrP, which inhibits sclerostin secretion in neighboring osteocytes via the PTH/PTHrP type 1 receptor interaction. The ensuing sclerostin-depleted region may enhance stem cell differentiation into osteoblasts and subperiosteal osteoid formation. OTM-mediated BRRS modulation suggests that administering sclerostin-inhibiting antibodies in combination with PTHrP may have a synergistic bone-inductive effect. This approach holds promise for enhancing osseous wound healing, treating osteoporosis, bone grafting and addressing orthodontic treatments that are linked to periodontal complications.

Wnt/β-catenin signaling pathway: an attractive potential therapeutic target in osteosarcoma

Osteosarcoma (OS) is the most common bone malignancy in children and adolescents, and although current neoadjuvant chemotherapy has shown efficacy against OS, the long-term survival rate for patients with OS remains low, highlighting the need to find more effective treatments. In cancer cells, abnormal activation of signaling pathways can widely affect cell activity from growth and proliferation to apoptosis, invasion and metastasis. Wnt/β-catenin is a complex and unique signaling pathway that is considered to be one of the most important carcinogenic pathways in human cancer. Research have confirmed that the Wnt/β-catenin signaling pathway is an important driving factor for the occurrence and development of osteosarcoma, and abnormal activation of this pathway can promote the pathological processes of cell proliferation, invasion, migration, tumor angiogenesis and chemical resistance of osteosarcoma. However, inhibition of Wnt/β-catenin signaling pathway can effectively inhibit or reverse the above pathological processes. Therefore, manipulating the expression or function of the Wnt/β-catenin pathway may be a potential targeted pathway for the treatment of OS. In this review, we describe the characteristics of the Wnt/β-catenin signaling pathway and summarize the role and mechanism of this pathway in OS. This paper discusses the therapeutic significance of inhibiting or targeting Wnt/β-catenin pathway in OS and the shortcomings of current studies on this pathway in OS and the problems to be solved. This review helps us to understand the role of Wnt/β-catenin on OS, and provides a theoretical basis and new ideas for targeting Wnt/β-catenin pathway as a therapeutic target for OS.

Role of Wnt5a in modulation of osteoporotic adipose-derived stem cells and osteogenesis

Osteoporosis, a condition marked by the deterioration of bone microarchitecture and increased facture risk, arises from a disruption in bone metabolism, with osteoclasts surpassing osteoblasts in bone resorption versus formation. The Wnt signalling pathway, a key regulator of bone maintenance, remains partially understood in osteoporosis. Our research delves into the role of Wnt-related molecules in this disease. In osteoporotic adipose-derived stem cells (OP-ASCs), we detected a significant decrease in Ctnnb1 and Frizzled-6 (Fzd6), contrasted by an increase in Gsk-3β and Wnt5a. Activation of the Wnt pathway by LiCl resulted in elevated Ctnnb1 and Fzd6, but decreased Gsk-3β and Wnt5a levels, promoting OP-ASCs' bone-formation capacity. In contrast, inhibition of this pathway by DKK-1 led to diminished Ctnnb1 and Fzd6, and increased Gsk-3β and Wnt5a, adversely affecting osteogenesis. Furthermore, our findings show that overexpressing Wnt5a impedes, while silencing it enhances the bone-forming capability of OP-ASCs. In a cranial bone defect model, the implantation of Wnt5a-silenced OP-ASCs with biphasic calcium phosphate scaffolds significantly promoted new bone formation. These observations indicated a repression of the canonical Wnt pathway and a stimulation of the non-canonical pathway in OP-ASCs. Silencing Wnt5a increased the osteogenic and regenerative abilities of OP-ASCs. Our study suggests targeting Wnt5a could be a promising strategy for enhancing bone regeneration in post-menopausal osteoporosis.

Mapping the sclerostin-LRP4 binding interface identifies critical interaction hotspots in loops 1 and 3 of sclerostin

The interaction of sclerostin (Scl) with the low-density lipoprotein receptor-related protein 4 (LRP4) leads to a marked reduction in bone formation by inhibiting the Wnt/β-catenin pathway. To characterize the Scl-LRP4 binding interface, we sorted a combinatorial library of Scl variants and isolated variants with reduced affinity to LRP4. We identified Scl single-mutation variants enriched during the sorting process and verified their reduction in affinity toward LRP4-a reduction that was not a result of changes in the variants' secondary structure or stability. We found that Scl positions K75 (loop 1) and V136 (loop 3) are critical hotspots for binding to LRP4. Our findings establish the foundation for targeting these hotspots for developing novel therapeutic strategies to promote bone formation.

The Masculinizing gene is a candidate male pathway developmental factor in the mud crab Scylla paramamosain

The Masculinizer (Masc) gene plays a crucial role in masculinization during insect embryonic gonadal development. Nevertheless, the Masc expression pattern and function in crabs remain largely unknown. In the present study, we screened and validated the Masc gene from transcriptome data of mud crab S. paramamosain. The Masc relative transcript level in the testis was significantly higher than that of ovaries and other tissues, as measured by quantitative real-time PCR. In situ hybridization showed that Masc exhibited a significant signal throughout all stages of testicular development. The phylogenetic analysis revealed conservation in the evolution of crustaceans, potentially indicating its functional importance. Masc RNA interference showed that the expression of testis bias-related genes decreased significantly while the ovary bias-related genes increased significantly. Transcriptome data suggested that Masc regulates several signaling pathways, including the mTOR, Wnt, insulin, and other sex-related pathways. These results indicate that Masc may play a role in mud crab male development with possible application in sex control in aquaculture.

Secreted Frizzled-Related Protein 1a regulates hematopoietic development in a dose-dependent manner

Hematopoietic stem and progenitor cells (HSPCs) arise only during embryonic development, and their identity specification, emergence from the floor of the dorsal aorta, and proliferation are all tightly regulated by molecular mechanisms such as signaling cues. Among these, Wnt signaling plays an important role in HSPC specification, differentiation, and self-renewal, requiring precise modulation for proper development and homeostasis. Wnt signaling is initiated when a Wnt ligand binds to cell surface receptors such as those encoded by the frizzled gene family, activating intracellular signaling pathways that regulate gene expression. Secreted frizzled-related proteins (Sfrps) are known modulators of Wnt signaling, acting as both agonists and antagonists of this pathway. Yet, in vivo functions of Sfrps in HSPC development remain incompletely understood. Here, we demonstrate that Sfrp1a regulates zebrafish HSPC development and differentiation in a dose-dependent manner. In Sfrp1a loss of function animals, we observe an increase in HSPCs, an upregulation of canonical Wnt signaling, and a decrease in differentiation into both lymphoid and myeloid lineages. Conversely, at low-dose sfrp1a overexpression, there is a decrease in HSPCs and an increase in lymphoid differentiation. High-dose sfrp1a overexpression phenocopies the loss of function animals, with an increase in HSPCs, increased canonical Wnt signaling, and decreased lymphoid and myeloid differentiation. These findings highlight the importance of dose-dependent modulation of Sfrps, paralleling what is observed in hematopoietic cancers where SFRP1 loss-of-function and gain-of-function variants can drive tumorigenesis.

Emerging regulatory mechanisms and functions of biomolecular condensates: implications for therapeutic targets

Cells orchestrate their processes through complex interactions, precisely organizing biomolecules in space and time. Recent discoveries have highlighted the crucial role of biomolecular condensates-membrane-less assemblies formed through the condensation of proteins, nucleic acids, and other molecules-in driving efficient and dynamic cellular processes. These condensates are integral to various physiological functions, such as gene expression and intracellular signal transduction, enabling rapid and finely tuned cellular responses. Their ability to regulate cellular signaling pathways is particularly significant, as it requires a careful balance between flexibility and precision. Disruption of this balance can lead to pathological conditions, including neurodegenerative diseases, cancer, and viral infections. Consequently, biomolecular condensates have emerged as promising therapeutic targets, with the potential to offer novel approaches to disease treatment. In this review, we present the recent insights into the regulatory mechanisms by which biomolecular condensates influence intracellular signaling pathways, their roles in health and disease, and potential strategies for modulating condensate dynamics as a therapeutic approach. Understanding these emerging principles may provide valuable directions for developing effective treatments targeting the aberrant behavior of biomolecular condensates in various diseases.

Small-molecule inhibitors of WNT signalling in cancer therapy and their links to autophagy and apoptosis

Cancer represents an intricate and heterogeneous ailment that evolves from a multitude of epigenetic and genetic variations that disrupt normal cellular function. The WNT/β-catenin pathway is essential in maintaining the balance between cell renewal and differentiation in various tissues. Abnormal activation of this pathway can lead to uncontrolled cell growth and initiate cancer across a variety of tissues such as the colon, skin, liver, and ovary. It enhances characteristics that lead to cancer progression, including angiogenesis, invasion and metastasis. Processes like autophagy and apoptosis which regulate cell death and play a crucial role in maintaining cellular equilibrium are also intimately linked with WNT/ β-catenin pathway. Thus, targeting WNT pathway has become a key strategy in developing antitumor therapies. Employing small molecule inhibitors has emerged as a targeted therapy to improve the clinical outcome compared to conventional cancer treatments. Many strategies using small molecule inhibitors for modulating the WNT/β-catenin pathway, such as hindering WNT ligands' secretion or interaction, disrupting receptor complex, and blocking the nuclear translocation of β-catenin have been investigated. These interventions have shown promise in both preclinical and clinical settings. This review provides a comprehensive understanding of the role of WNT/β-catenin signalling pathway's role in cancer, emphasizing its regulation of autophagy and apoptosis. Our goal is to highlight the potential of specific small molecule inhibitors targeting this pathway, fostering the development of novel, tailored cancer treatments.

Aberrant Wnt/β-catenin signaling in the mesenchymal stem cells of LZTFL1-depleted mice leads to increased adipogenesis, with implications for obesity

Obesity is one of the main clinical characteristics associated with the heterogeneous genetic disorder Bardet-Biedl syndrome (BBS). Leucine zipper transcription factor like 1 (LZTFL1) is a member of the BBS gene family. Our work showed that Lztfl1knockout (LZKO) mice display the obesity phenotype as early as 3 months of age. Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into various cell types, including adipocytes. To understand the role of LZTFL1 in adipogenesis, we analyzed MSCs isolated from LZKO mouse compact bones (CB-MSCs). Compared to wildtype (WT), LZKO CB-MSCs had elongated primary cilia with tapered tips and increased levels of peroxisome proliferator-activated receptor γ (PPARγ), a key transcription factor that favors adipogenesis, and nuclear glucocorticoid receptor (GR), a transcription factor involved in Pparg activation. Also, LZKO CB-MSCs had a lower level of total β-catenin, a core factor of the antiadipogenic canonical Wnt/b-catenin signaling pathway involved in limiting the nuclear localization of GR. Interaction between caveolin1 (CAV1) and LRP6, the main receptor for canonical Wnt signaling, is known to be critical for Wnt pathway activation and β-catenin stabilization. Compared to WT cells, LZKO cells had elevated total, cell-surface, and lipid-raft-associated LRP6 and reduced CAV1, strongly indicating alterations in the components of the Wnt-signaling pathway. We show that in the absence of LZTFL1, adipogenesis-restraining Wnt/β-catenin signaling is inhibited, and adipogenesis-favorable factors are stimulated in CB-MSCs, leading to enhanced adipogenesis. Evidence provided here could help in understanding the mechanism and molecular basis of obesity in LZTFL1-defective patients.

Wnt/β-catenin and notch signaling pathways in cardiovascular disease: Mechanisms and therapeutics approaches

Wnt and Notch signaling pathways play crucial roles in the development and homeostasis of the cardiovascular system. These pathways regulate important cellular processes in cardiomyocytes, endothelial cells, and smooth muscle cells, which are the key cell types involved in the structure and function of the heart and vasculature. During embryonic development, Wnt and Notch signaling coordinate cell fate specification, proliferation, differentiation, and morphogenesis of the heart and blood vessels. In the adult cardiovascular system, these pathways continue to maintain tissue homeostasis and arrange adaptive responses to various physiological and pathological stimuli. Dysregulation of Wnt and Notch signaling has been involved in the pathogenesis of numerous cardiovascular diseases, including atherosclerosis, hypertension, myocardial infarction, and heart failure. Abnormal activation or suppression of these pathways in specific cell types can contribute to endothelial dysfunction, vascular remodeling, cardiomyocyte hypertrophy, impaired cardiac contractility and dead. Understanding the complex interplay between Wnt and Notch signaling in the cardiovascular system has led to the investigation of these pathways as potential therapeutic targets in clinical trials. In conclusion, this review summarizes the current knowledge on the roles of Wnt and Notch signaling in the development and homeostasis of cardiomyocytes, endothelial cells, and smooth muscle cells. It further discusses the dysregulation of these pathways in the context of major cardiovascular diseases and the ongoing clinical investigations targeting Wnt and Notch signaling for therapeutic intervention.

Emerging roles and biomarker potential of WNT6 in human cancers

The WNT6 ligand is a well-known activator of the WNT signaling pathway, considered a vital player in several important physiologic processes during embryonic development and maintaining homeostasis throughout life, regulating the proliferation and differentiation of multiple stem/progenitor cell types. More recently, as it is the case for many key molecular regulators of embryonic development, dysregulation of WNT6 has been implicated in cancer development and progression in multiple studies. In this review, we overview the most significant recent findings regarding WNT6 in the context of human malignancies, exploring its influence on multiple dimensions of tumor pathophysiology and highlighting the putative underlying WNT6-associated molecular mechanisms. We also discuss the potential clinical implications of WNT6 as a prognostic and therapeutic biomarker. This critical review highlights the emerging relevance of WNT6 in multiple human cancers, and its potential as a clinically-useful biomarker, addressing key unanswered questions that could lead to new opportunities in patient diagnosis, stratification, and the development of rationally-designed precision therapies.

The Wnt signaling pathway in hepatocellular carcinoma: Regulatory mechanisms and therapeutic prospects

Hepatocellular carcinoma (HCC) is a malignant tumor that arises from hepatocytes. Multiple signaling pathways play a regulatory role in the occurrence and development of HCC, with the Wnt signaling pathway being one of the primary regulatory pathways. In normal hepatocytes, the Wnt signaling pathway maintains cell regeneration and organ development. However, when aberrant activated, the Wnt pathway is closely associated with invasion, cancer stem cells(CSCs), drug resistance, and immune evasion in HCC. Among these factors, the development of drug resistance is one of the most important factors affecting the efficacy of HCC treatment. These mechanisms form the basis for tumor cell adaptation and evolution within the body, enabling continuous changes in tumor cells, resistance to drugs and immune system attacks, leading to metastasis and recurrence. In recent years, there have been numerous new discoveries regarding these mechanisms. An increasing number of drugs targeting the Wnt signaling pathway have been developed, with some already entering clinical trials. Therefore, this review encompasses the latest research on the role of the Wnt signaling pathway in the onset and progression of HCC, as well as advancements in its therapeutic strategies.

GSK-3: An "Ace" Among Kinases

Background: Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase known to participate in the regulation of β-catenin signaling (Wnt signaling). This aids in the establishment of a multicomponent destruction complex that stimulates phosphorylation, leading to the destruction of β-catenin. Evidence about the role of increasingly active β-catenin signaling is involved in many forms of human cancer. The understanding of GSK-3 remains elusive as recent research aims to focus on developing potent GSK-3 inhibitors to target this kinase. Objective: This short review aims to highlight the regulation of GSK-3 with emphasis on Wnt signaling while highlighting its interaction with miRNAs corresponding to pluripotency and epithelial mesenchymal transition substantiating this kinase as an "Ace" among kinases in regulation of cellular processes. Result: Significant findings of miRNA regulation by GSK-3 exemplify the underpinnings of kinase-mediated transcriptional regulation in cancers. Conclusion: The review provides evidence on the role of GSK-3 as a possible master regulator of proteins and noncoding RNA, thereby implicating the fate of a cell.

Role of Wnt/β-catenin pathway in cancer drug resistance: Insights into molecular aspects of major solid tumors

Adaptive resistance to conventional and targeted therapies remains one of the major obstacles in the effective management of cancer. Aberrant activation of key signaling mechanisms plays a pivotal role in modulating resistance to drugs. An evolutionarily conserved Wnt/β-catenin pathway is one of the signaling cascades which regulate resistance to drugs. Elevated Wnt signaling confers resistance to anticancer therapies, either through direct activation of its target genes or via indirect mechanisms and crosstalk over other signaling pathways. Involvement of the Wnt/β-catenin pathway in cancer hallmarks like inhibition of apoptosis, promotion of invasion and metastasis and cancer stem cell maintenance makes this pathway a potential target to exploit for addressing drug resistance. Accumulating evidences suggest a critical role of Wnt/β-catenin pathway in imparting resistance across multiple cancers including PDAC, NSCLC, TNBC, etc. Here we present a comprehensive assessment of how Wnt/β-catenin pathway mediates cancer drug resistance in majority of the solid tumors. We take a deep dive into the Wnt/β-catenin signaling-mediated modulation of cellular and downstream molecular mechanisms and their impact on cancer resistance.

A mechanism of action-reflective, dual cell-based bioassay for determining the bioactivity of sclerostin-neutralizing antibodies

Osteoporosis is a major threat to the elderly worldwide. The Wnt signaling pathway plays a critical role in bone development and homeostasis. Sclerostin, a Wnt ligand inhibitor, competes with Wnt ligands for low-density lipoprotein receptor-related protein 5 or 6 (LRP5/6) on osteoblasts, thereby suppressing bone formation. Sclerostin-neutralizing monoclonal antibodies (mAbs) have emerged as a potential bone-forming therapy for osteoporosis. A cell-based bioassay which determines the relative activity of a product, related to its mechanism of action, is of great importance from drug discovery to quality control and batch release. Currently used cell-based bioassays for sclerostin-neutralizing mAbs usually use Wnt1 or Wnt3a to stimulate the Wnt pathway; sclerostin is a direct inhibitor of Wnt1 but not Wnt3a. Wnt1 is a highly hydrophobic protein that binds to the producing cell membrane and acts in a juxtacrine manner to stimulate the Wnt pathway in neighboring cells. Bioassays for drugs that induce Wnt1 signaling should be performed in a juxtacrine manner. Here, we present a mechanism of action-reflective, dual cell-based reporter gene assay. In this assay, Wnt1 producer cells are co-cultured with cells containing the Wnt reporter genes, Wnt1 on the producer cells activates the Wnt signaling pathway in the reporter cells that are in direct cell-to-cell contact, and sclerostin-neutralizing mAbs specifically and effectively antagonize the sclerostin-mediated Wnt reporter gene suppression. This bioassay demonstrates good specificity, accuracy, linearity, and precision and is suitable for quality control, stability testing, batch release, and biosimilarity assessment of sclerostin-neutralizing mAbs.

Combination of arsenic trioxide and apatinib synergistically inhibits small cell lung cancer by down-regulating VEGFR2/mTOR and Akt/c-Myc signaling pathway via GRB10

BACKGROUND

Small cell lung carcinoma (SCLC) is characterized by -poor prognosis, -high predilection for -metastasis, -proliferation, and -absence of newer therapeutic options. Elucidation of newer pathways characterizing the disease may allow for development of targeted therapies and consequently favorable outcomes.

METHODS

The current study explored the combinatorial action of arsenic trioxide (ATO) and apatinib (APA) in vitro and in vivo. In vitro models were tested using -H446 and -H196 SCLC cell lines. The ability of drugs to reduce -metastasis, -cell proliferation, and -migration were assessed. Using bioinformatic analysis, differentially expressed genes were determined. Gene regulation was assessed using gene knock down models and confirmed using Western blots. The in vivo models were used to confirm the resolution of pathognomic features in the presence of the drugs. Growth factor receptor bound protein (GRB) 10 expression levels of human small cell lung cancer tissues and adjacent tissues were detected by IHC.

RESULTS

In combination, ATO and APA were found to significantly reduce -cell proliferation, -migration, and -metastasis in both the cell lines. Cell proliferation was found to be inhibited by activation of Caspase-3, -7 pathway. In the presence of drugs, it was found that expression of GRB10 was stabilized. The silencing of GRB10 was found to negatively regulate the VEGFR2/Akt/mTOR and Akt/GSK-3β/c-Myc signaling pathway. Concurrently, absence of metastasis and reduction of tumor volume were confirmed in vivo. The immunohistochemical results confirmed that the expression level of GRB10 in adjacent tissues was significantly higher than that in human small cell lung cancer tissues.

CONCLUSIONS

Synergistically, ATO and APA have a more significant impact on inhibiting cell proliferation than each drug independently. ATO and APA may be mediating its action through the stabilization of GRB10 thus acting as a tumor suppressor. We thus, preliminarily report the impact of GRB10 stability as a target for SCLC treatment.

Pathophysiology in Brain Arteriovenous Malformations: Focus on Endothelial Dysfunctions and Endothelial-to-Mesenchymal Transition

Brain arteriovenous malformations (bAVMs) substantially increase the risk for intracerebral hemorrhage (ICH), which is associated with significant morbidity and mortality. However, the treatment options for bAVMs are severely limited, primarily relying on invasive methods that carry their own risks for intraoperative hemorrhage or even death. Currently, there are no pharmaceutical agents shown to treat this condition, primarily due to a poor understanding of bAVM pathophysiology. For the last decade, bAVM research has made significant advances, including the identification of novel genetic mutations and relevant signaling in bAVM development. However, bAVM pathophysiology is still largely unclear. Further investigation is required to understand the detailed cellular and molecular mechanisms involved, which will enable the development of safer and more effective treatment options. Endothelial cells (ECs), the cells that line the vascular lumen, are integral to the pathogenesis of bAVMs. Understanding the fundamental role of ECs in pathological conditions is crucial to unraveling bAVM pathophysiology. This review focuses on the current knowledge of bAVM-relevant signaling pathways and dysfunctions in ECs, particularly the endothelial-to-mesenchymal transition (EndMT).

Cancer, metastasis, and the epigenome

Cancer is the second leading cause of death worldwide and disease burden is expected to increase globally throughout the next several decades, with the majority of cancer-related deaths occurring in metastatic disease. Cancers exhibit known hallmarks that endow them with increased survival and proliferative capacities, frequently as a result of de-stabilizing mutations. However, the genomic features that resolve metastatic clones from primary tumors are not yet well-characterized, as no mutational landscape has been identified as predictive of metastasis. Further, many cancers exhibit no known mutation signature. This suggests a larger role for non-mutational genome re-organization in promoting cancer evolution and dissemination. In this review, we highlight current critical needs for understanding cell state transitions and clonal selection advantages for metastatic cancer cells. We examine links between epigenetic states, genome structure, and misregulation of tumor suppressors and oncogenes, and discuss how recent technologies for understanding domain-scale regulation have been leveraged for a more complete picture of oncogenic and metastatic potential.

Cell signaling and transcriptional regulation of osteoblast lineage commitment, differentiation, bone formation, and homeostasis

The initiation of osteogenesis primarily occurs as mesenchymal stem cells undergo differentiation into osteoblasts. This differentiation process plays a crucial role in bone formation and homeostasis and is regulated by two intricate processes: cell signal transduction and transcriptional gene expression. Various essential cell signaling pathways, including Wnt, BMP, TGF-β, Hedgehog, PTH, FGF, Ephrin, Notch, Hippo, and Piezo1/2, play a critical role in facilitating osteoblast differentiation, bone formation, and bone homeostasis. Key transcriptional factors in this differentiation process include Runx2, Cbfβ, Runx1, Osterix, ATF4, SATB2, and TAZ/YAP. Furthermore, a diverse array of epigenetic factors also plays critical roles in osteoblast differentiation, bone formation, and homeostasis at the transcriptional level. This review provides an overview of the latest developments and current comprehension concerning the pathways of cell signaling, regulation of hormones, and transcriptional regulation of genes involved in the commitment and differentiation of osteoblast lineage, as well as in bone formation and maintenance of homeostasis. The paper also reviews epigenetic regulation of osteoblast differentiation via mechanisms, such as histone and DNA modifications. Additionally, we summarize the latest developments in osteoblast biology spurred by recent advancements in various modern technologies and bioinformatics. By synthesizing these insights into a comprehensive understanding of osteoblast differentiation, this review provides further clarification of the mechanisms underlying osteoblast lineage commitment, differentiation, and bone formation, and highlights potential new therapeutic applications for the treatment of bone diseases.

Non-canonical Wnt pathway expression in the developing mouse and human retina

The non-canonical Wnt pathway is an evolutionarily conserved pathway essential for tissue patterning and development across species and tissues. In mammals, this pathway plays a role in neuronal migration, dendritogenesis, axon growth, and synapse formation. However, its role in development and synaptogenesis of the human retina remains less established. In order to address this knowledge gap, we analyzed publicly available single-cell RNA sequencing (scRNAseq) datasets for mouse retina, human retina, and human retinal organoids over multiple developmental time points during outer retinal maturation. We identified ligands, receptors, and mediator genes with a putative role in retinal development, including those with novel or species-specific expression, and validated this expression using fluorescence in situ hybridization (FISH). By quantifying outer nuclear layer (ONL) versus inner nuclear layer (INL) expression, we provide evidence for the differential expression of certain non-canonical Wnt signaling components in the developing mouse and human retina during outer plexiform layer (OPL) development. Importantly, we identified distinct expression patterns of mouse and human FZD3 and WNT10A, as well as previously undescribed expression, such as for mouse Wnt2b in Chat+ starburst amacrine cells. Human retinal organoids largely recapitulated the human non-canonical Wnt pathway expression. Together, this work provides the basis for further study of non-canonical Wnt signaling in mouse and human retinal development and synaptogenesis.

Multifaceted effects of LRP6 in cancer: exploring tumor development, immune modulation and targeted therapies

Low-density lipoprotein receptor (LDLR)-related protein 6 (LRP6), a member of the LDLR superfamily of cell surface receptors, is most widely known as a crucial co-receptor in the activation of canonical Wnt/β-catenin signaling. This signaling pathway is implicated in multiple biological processes, such as lipoprotein metabolism, protease regulation, cell differentiation, and migration. LRP6 is frequently overexpressed in a variety of tumors, including liver cancer, colorectal cancer, and prostate cancer, and is generally considered an oncogene that promotes tumor proliferation, migration, and invasion. However, there are exceptions; some studies have reported that LRP6 inhibits lung metastasis of breast cancer through its ectodomain (LRP6N), and patients with low LRP6 expression tend to have a poor prognosis. Thus, the role of LRP6 in tumors remains controversial. Although limited studies have shown that LRP6 is associated with the expression and roles of a variety of immune cells in tumors, the interaction of LRP6 with the tumor microenvironment (TME) is not fully understood. Furthermore, it is crucial to acknowledge that LRP6 can engage with alternative pathways, including the mTORC1, CXCL12/CXCR4, and KRAS signaling pathways mentioned earlier, resulting in the regulation of biological functions independent of canonical Wnt/β-catenin signaling. Due to the potential of LRP6 as a molecular target for cancer therapy, various treatment modalities have been developed to directly or indirectly inhibit LRP6 function, demonstrating promising anti-cancer effects across multiple cancer types. This review will concentrate on exploring the expression, function, and potential therapeutic applications of LRP6 in different cancer types, along with its influence on the TME.

Wnt/β-catenin signaling pathway in carcinogenesis and cancer therapy

The Wnt/β-catenin signaling pathway plays a crucial role in various physiological processes, encompassing development, tissue homeostasis, and cell proliferation. Under normal physiological conditions, the Wnt/β-catenin signaling pathway is meticulously regulated. However, aberrant activation of this pathway and downstream target genes can occur due to mutations in key components of the Wnt/β-catenin pathway, epigenetic modifications, and crosstalk with other signaling pathways. Consequently, these dysregulations contribute significantly to tumor initiation and progression. Therapies targeting the Wnt/β-catenin signaling transduction have exhibited promising prospects and potential for tumor treatment. An increasing number of medications targeting this pathway are continuously being developed and validated. This comprehensive review aims to summarize the latest advances in our understanding of the role played by the Wnt/β-catenin signaling pathway in carcinogenesis and targeted therapy, providing valuable insights into acknowledging current opportunities and challenges associated with targeting this signaling pathway in cancer research and treatment.

Signaling Pathways Governing Cardiomyocyte Differentiation

Cardiomyocytes are the largest cell type that make up the heart and confer beating activity to the heart. The proper differentiation of cardiomyocytes relies on the efficient transmission and perception of differentiation cues from several signaling pathways that influence cardiomyocyte-specific gene expression programs. Signaling pathways also mediate intercellular communications to promote proper cardiomyocyte differentiation. We have reviewed the major signaling pathways involved in cardiomyocyte differentiation, including the BMP, Notch, sonic hedgehog, Hippo, and Wnt signaling pathways. Additionally, we highlight the differences between different cardiomyocyte cell lines and the use of these signaling pathways in the differentiation of cardiomyocytes from stem cells. Finally, we conclude by discussing open questions and current gaps in knowledge about the in vitro differentiation of cardiomyocytes and propose new avenues of research to fill those gaps.

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 evolving roles of Wnt signaling in stem cell proliferation and differentiation, the development of human diseases, and therapeutic opportunities

The evolutionarily conserved Wnt signaling pathway plays a central role in development and adult tissue homeostasis across species. Wnt proteins are secreted, lipid-modified signaling molecules that activate the canonical (β-catenin dependent) and non-canonical (β-catenin independent) Wnt signaling pathways. Cellular behaviors such as proliferation, differentiation, maturation, and proper body-axis specification are carried out by the canonical pathway, which is the best characterized of the known Wnt signaling paths. Wnt signaling has emerged as an important factor in stem cell biology and is known to affect the self-renewal of stem cells in various tissues. This includes but is not limited to embryonic, hematopoietic, mesenchymal, gut, neural, and epidermal stem cells. Wnt signaling has also been implicated in tumor cells that exhibit stem cell-like properties. Wnt signaling is crucial for bone formation and presents a potential target for the development of therapeutics for bone disorders. Not surprisingly, aberrant Wnt signaling is also associated with a wide variety of diseases, including cancer. Mutations of Wnt pathway members in cancer can lead to unchecked cell proliferation, epithelial-mesenchymal transition, and metastasis. Altogether, advances in the understanding of dysregulated Wnt signaling in disease have paved the way for the development of novel therapeutics that target components of the Wnt pathway. Beginning with a brief overview of the mechanisms of canonical and non-canonical Wnt, this review aims to summarize the current knowledge of Wnt signaling in stem cells, aberrations to the Wnt pathway associated with diseases, and novel therapeutics targeting the Wnt pathway in preclinical and clinical studies.

Molecular pathways and therapeutic targets linked to triple-negative breast cancer (TNBC)

Cancer is a group of diseases characterized by uncontrolled cellular growth, abnormal morphology, and altered proliferation. Cancerous cells lose their ability to act as anchors, allowing them to spread throughout the body and infiltrate nearby cells, tissues, and organs. If these cells are not identified and treated promptly, they will likely spread. Around 70% of female breast cancers are caused by a mutation in the BRCA gene, specifically BRCA1. The absence of progesterone, oestrogen and HER2 receptors (human epidermal growth factor) distinguishes the TNBC subtype of breast cancer. There were approximately 6,85,000 deaths worldwide and 2.3 million new breast cancer cases in women in 2020. Breast cancer is the most common cancer globally, affecting 7.8 million people at the end of 2020. Compared to other cancer types, breast cancer causes more women to lose disability-adjusted life years (DALYs). Worldwide, women can develop breast cancer at any age after puberty, but rates increase with age. The maintenance of mammary stem cell stemness is disrupted in TNBC, governed by signalling cascades controlling healthy mammary gland growth and development. Interpreting these essential cascades may facilitate an in-depth understanding of TNBC cancer and the search for an appropriate therapeutic target. Its treatment remains challenging because it lacks specific receptors, which renders hormone therapy and medications ineffective. In addition to radiotherapy, numerous recognized chemotherapeutic medicines are available as inhibitors of signalling pathways, while others are currently undergoing clinical trials. This article summarizes the vital druggable targets, therapeutic approaches, and strategies associated with TNBC.

Glucocorticoid-Induced Ocular Hypertension and Glaucoma

Glucocorticoid (GC) therapy is indicated in many diseases, including ocular diseases. An important side-effect of GC therapy is GC-induced ocular hypertension (GIOHT), which may cause irreversible blindness known as GC-induced glaucoma (GIG). Here, we reviewed the pathological changes that contribute to GIOHT including in the trabecular meshwork and Schlemm's canal at cellular and molecular levels. We also discussed the clinical aspects of GIOHT/GIG including disease prevalence, risk factors, the type of GCs, the route of GC administration, and management strategies.

Role of APOE in glaucoma

Glaucoma is a chronic blinding eye disease caused by the progressive loss of retinal ganglion cells (RGCs). Currently, no clinically approved treatment can directly improve the survival rate of RGCs. The Apolipoprotein E (APOE) gene is closely related to the genetic risk of numerous neurodegenerative diseases and has become a hot topic in the field of neurodegenerative disease research in recent years. The optic nerve and retina are extensions of the brain's nervous system. The pathogenesis of retinal degenerative diseases is closely related to the degenerative diseases of the nerves in the brain. APOE consists of three alleles, ε4, ε3, and ε2, in a single locus. They have varying degrees of risk for glaucoma. APOE4 and the APOE gene deletion (APOE-/-) can reduce RGC loss. By contrast, APOE3 and the overall presence of APOE genes (APOE+/+) result in significant loss of RGC bodies and axons, increasing the risk of glaucoma RGCs death. Currently, there is no clear literature indicating that APOE2 is beneficial or harmful to glaucoma. This study summarises the mechanism of different APOE genes in glaucoma and speculates that APOE targeted intervention may be a promising method for protecting against RGCs loss in glaucoma.

Canonical and noncanonical Wnt signaling: Multilayered mediators, signaling mechanisms and major signaling crosstalk

Wnt signaling plays a major role in regulating cell proliferation and differentiation. The Wnt ligands are a family of 19 secreted glycoproteins that mediate their signaling effects via binding to Frizzled receptors and LRP5/6 coreceptors and transducing the signal either through β-catenin in the canonical pathway or through a series of other proteins in the noncanonical pathway. Many of the individual components of both canonical and noncanonical Wnt signaling have additional functions throughout the body, establishing the complex interplay between Wnt signaling and other signaling pathways. This crosstalk between Wnt signaling and other pathways gives Wnt signaling a vital role in many cellular and organ processes. Dysregulation of this system has been implicated in many diseases affecting a wide array of organ systems, including cancer and embryological defects, and can even cause embryonic lethality. The complexity of this system and its interacting proteins have made Wnt signaling a target for many therapeutic treatments. However, both stimulatory and inhibitory treatments come with potential risks that need to be addressed. This review synthesized much of the current knowledge on the Wnt signaling pathway, beginning with the history of Wnt signaling. It thoroughly described the different variants of Wnt signaling, including canonical, noncanonical Wnt/PCP, and the noncanonical Wnt/Ca2+ pathway. Further description involved each of its components and their involvement in other cellular processes. Finally, this review explained the various other pathways and processes that crosstalk with Wnt signaling.

Secreted Frizzled-Related Protein 4 Induces Gastric Cancer Progression and Resistance to Cisplatin and Oxaliplatin via β-Catenin Dysregulation

INTRODUCTION

Gastric cancer is the fifth most common cancer and third leading cause of cancer-related death worldwide. There are three main ways to treat gastric cancer: surgical resection, radiation therapy, and drug therapy. Furthermore, combinations of two to three regimens can improve survival. However, the survival outcomes of chemotherapy in advanced gastric cancer patients are still unsatisfactory. Unfortunately, no widely useful biomarkers have been verified to predict the efficacy of chemotherapy for locally advanced gastric cancer.

METHODS

An MTT assay was used to determine the cell viability after cisplatin or oxaliplatin treatment. Western blotting and immunohistochemistry were utilized to examine the secreted frizzled-related protein 4 (sFRP4) level and associated signaling pathways. Immunofluorescence staining was utilized to analyze the location of β-catenin. Colony formation and Transwell assays were used to analyze the functions related with cisplatin, oxaliplatin, and sFRP4.

RESULTS

We have found that gastric cancer patients treated with combinations of 5-fluorouracil (5-FU) and cisplatin regimens have better survival rates than those treated with 5-FU-based chemotherapy alone. sFRP4 was selected as a potential target from stringent analysis and intersection of 5-FU and cisplatin resistance-related gene sets. sFRP4 was shown to be overexpressed in clinical gastric tumor tissues and positively correlated with a worse survival rate. In addition, sFRP4 and β-catenin were upregulated in cisplatin- and oxaliplatin-resistant gastric cancer cells compared to parental cells. Immunofluorescence staining and nuclear fractionation showed that β-catenin was translocated from the cytosol into the nucleus. Moreover, sFRP4 was detected in the conditioned medium of these resistant cells, which indicates that sFRP4 might have an extracellular role in chemotherapy resistance. Increased migration capacity and dysregulation of epithelial-mesenchymal transition-related markers, which might result from the dysregulation of sFRP4, were observed in cisplatin- and oxaliplatin-resistant gastric cancer cells.

DISCUSSION/CONCLUSION

In summary, sFRP4 might play a critical role in resistance to cisplatin and oxaliplatin, cell metastasis, and poor prognosis in gastric cancer via the Wnt-β-catenin pathway. Investigations of the molecular mechanism underlying sFRP4-modulated cancer progression and chemotherapeutic outcomes can provide additional therapeutic strategies for gastric cancer.

Biologics: Teriparatide and Newer Anabolics

The landscape of osteoporosis management has evolved significantly over the years, witnessing a paradigm shift from conventional therapies to the emergence of biologic agents. This chapter delves into the intricate mechanisms, potential applications, and future directions of biologic interventions in osteoporosis care. Biologic agents, with their targeted approach to bone health, have revolutionized the field by offering precision-driven strategies that address the underlying mechanisms of bone fragility. This chapter explores the mechanisms of action of various biologics, including Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) inhibitors, monoclonal antibodies targeting sclerostin, parathyroid hormone (PTH) analogues, and cathepsin K inhibitors. It discusses their potential benefits, limitations, and safety considerations, while shedding light on the promise of combination therapies that merge biologic agents with traditional approaches. Furthermore, the chapter delves into the potential applications of biologic agents in specific patient populations, the role of biomarkers in predicting treatment responses, and the influence of emerging biological targets. It also explores the advancements in novel targets and drug delivery systems that aim to enhance treatment convenience and effectiveness. By tailoring treatments based on patient characteristics and exploring novel therapeutic targets, the chapter envisions a future of precision medicine in osteoporosis care. As research continues to evolve, the chapter anticipates a transformative impact on bone health outcomes, fracture prevention, and overall quality of life for individuals at risk of osteoporosis-related fractures. Through comprehensive insights into the mechanisms, applications, and future directions of biologic agents, this chapter offers a holistic perspective on the evolving landscape of osteoporosis management.

Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome

Familial Exudative Vitreoretinopathy (FEVR), Norrie disease, and persistent fetal vascular syndrome (PFVS) are extremely rare retinopathies that are clinically distinct but are unified by abnormal retinal endothelial cell function, and subsequent irregular retinal vascular development and/or aberrant inner blood-retinal-barrier (iBRB) function. The early angiogenesis of the retina and its iBRB is a delicate process that is mediated by the canonical Norrin Wnt-signaling pathway in retinal endothelial cells. Pathogenic variants in genes that play key roles within this pathway, such as NDP, FZD4, TSPAN12, and LRP5, have been associated with the incidence of these retinal diseases. Recent efforts to further elucidate the etiology of these conditions have not only highlighted their multigenic nature but have also resulted in the discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway. Recent discoveries of FEVR-linked variants in two other Catenin genes (CTNND1, CTNNA1) and the Endoplasmic Reticulum Membrane Complex Subunit-1 gene (EMC1) suggest that we will continue to find additional genes that impact the neural retinal vasculature, especially in multi-syndromic conditions. The goal of this review is to briefly highlight the current understanding of the roles of their encoded proteins in retinal endothelial cells to understand the essential functional mechanisms that can be altered to cause these very rare pediatric retinal vascular diseases.

Frizzled 6 mutation regulates reserpine-induced depression-like behavior and Wnt signaling pathway in mice

BACKGROUND

Frizzled 6 (Fzd6) is involved in the development of various disorders; however, its role in the etiology of depression remains unclear. We aimed to determine the potential regulatory mechanisms of Fzd6 as a Wnt receptor in depression.

METHODS

Mice were divided into four groups: wild-type control (Fzd6WT-control), Fzd6 mutant control (Fzd6Q152E-control), wild-type reserpine (Fzd6WT-reserpine), and Fzd6 mutant reserpine (Fzd6Q152E-reserpine). Reserpine (0.5 mg/kg) was injected intraperitoneally for 10 days. Four behavioral experiments were performed to assess the effects of Fzd6Q152E on depression-like behaviors in the reserpine-treated mice. Blood samples were collected for an enzyme-linked immunosorbent assay (ELISA). Gene expression in the hippocampus was quantified using quantitative real-time polymerase chain reaction (qRT-PCR), and protein expression levels in the hippocampus were identified using western blotting.

RESULTS

The Fzd6 mutation affected reserpine-induced depression-like behavioral changes in mice. ELISA revealed significantly reduced serum levels of 5-hydroxytryptamine (5-HT), brain-derived neurotrophic factor (BDNF), and norepinephrine in both Fzd6Q152E-reserpine and Fzd6WT-reserpine mice, with a more pronounced decrease in Fzd6Q152E-reserpine mice, especially in norepinephrine expression. The qRT-PCR results showed significantly decreased Fzd6 expression in Fzd6Q152E-reserpine mice and altered expression of Dkk2, Gsk-3β, Lrp6, Wnt2, Wnt3, and Wnt3a in the Wnt pathway. Western blotting revealed decreased Fzd6 protein expression in Fzd6Q152E-control mice compared to Fzd6WT-control mice, whereas Fzd6 protein expression was restored in Fzd6Q152E-reserpine mice, and Gsk-3β expression was significantly changed.

CONCLUSION

Fzd6 potentially influences reserpine-induced depressive behavioral changes and serum depressive factor alterations and modulates the expression of the Wnt signaling pathway in the hippocampus of depressed mice.

Promoting New Approach Methodologies (NAMs) for research on skin color changes in response to environmental stress factors: tobacco and air pollution

Aging is one of the most dynamic biological processes in the human body and is known to carry significant impacts on individuals' self-esteem. Skin pigmentation is a highly heritable trait made possible by complex, strictly controlled cellular and molecular mechanisms. Genetic, environmental and endocrine factors contribute to the modulation of melanin's amount, type and distribution in the skin layers. One of the hallmarks of extrinsic skin aging induced by environmental stress factors is the alteration of the constitutive pigmentation pattern clinically defined as senile lentigines and/or melasma or other pigmentary dyschromias. The complexity of pollutants and tobacco smoke as environmental stress factors warrants a thorough understanding of the mechanisms by which they impact skin pigmentation through repeated and long-term exposure. Pre-clinical and clinical studies demonstrated that pollutants are known to induce reactive oxygen species (ROS) or inflammatory events that lead directly or indirectly to skin hyperpigmentation. Another mechanistic direction is provided by Aryl hydrocarbon Receptors (AhR) which were shown to mediate processes leading to skin hyperpigmentation in response to pollutants by regulation of melanogenic enzymes and transcription factors involved in melanin biosynthesis pathway. In this context, we will discuss a diverse range of New Approach Methodologies (NAMs) capable to provide mechanistic insights of the cellular and molecular pathways involved in the action of environmental stress factors on skin pigmentation and to support the design of raw ingredients and formulations intended to counter their impact and of any subsequently needed clinical studies.

The Molecular Basis of Wnt/β-Catenin Signaling Pathways in Neurodegenerative Diseases

Defective Wnt signaling is found to be associated with various neurodegenerative diseases. In the canonical pathway, the Frizzled receptor (Fzd) and the lipoprotein receptor-related proteins 5/6 (LRP5/LRP6) create a seven-pass transmembrane receptor complex to which the Wnt ligands bind. This interaction causes the tumor suppressor adenomatous polyposis coli gene product (APC), casein kinase 1 (CK1), and GSK-3β (glycogen synthase kinase-3 beta) to be recruited by the scaffold protein Dishevelled (Dvl), which in turn deactivates the β-catenin destruction complex. This inactivation stops the destruction complex from phosphorylating β-catenin. As a result, β-catenin first builds up in the cytoplasm and then migrates into the nucleus, where it binds to the Lef/Tcf transcription factor to activate the transcription of more than 50 Wnt target genes, including those involved in cell growth, survival, differentiation, neurogenesis, and inflammation. The treatments that are currently available for neurodegenerative illnesses are most commonly not curative in nature but are only symptomatic. According to all available research, restoring Wnt/β-catenin signaling in the brains of patients with neurodegenerative disorders, particularly Alzheimer's and Parkinson's disease, would improve the condition of several patients with neurological disorders. The importance of Wnt activators and modulators in patients with such illnesses is to mainly restore rather than overstimulate the Wnt/β-catenin signaling, thereby reestablishing the equilibrium between Wnt-OFF and Wnt-ON states. In this review, we have tried to summarize the significance of the Wnt canonical pathway in the pathophysiology of certain neurodegenerative diseases, such as Alzheimer's disease, cerebral ischemia, Parkinson's disease, Huntington's disease, multiple sclerosis, and other similar diseases, and as to how can it be restored in these patients.

APPlications of amyloid-β precursor protein metabolites in macrocephaly and autism spectrum disorder

Metabolites of the Amyloid-β precursor protein (APP) proteolysis may underlie brain overgrowth in Autism Spectrum Disorder (ASD). We have found elevated APP metabolites (total APP, secreted (s) APPα, and α-secretase adamalysins in the plasma and brain tissue of children with ASD). In this review, we highlight several lines of evidence supporting APP metabolites' potential contribution to macrocephaly in ASD. First, APP appears early in corticogenesis, placing APP in a prime position to accelerate growth in neurons and glia. APP metabolites are upregulated in neuroinflammation, another potential contributor to excessive brain growth in ASD. APP metabolites appear to directly affect translational signaling pathways, which have been linked to single gene forms of syndromic ASD (Fragile X Syndrome, PTEN, Tuberous Sclerosis Complex). Finally, APP metabolites, and microRNA, which regulates APP expression, may contribute to ASD brain overgrowth, particularly increased white matter, through ERK receptor activation on the PI3K/Akt/mTOR/Rho GTPase pathway, favoring myelination.

Insilco prediction of the role of the FriZZled5 gene in colorectal cancer

INTRODUCTION

In this study, we aimed to elucidate the crosstalk between the Wnt/β-catenin signaling pathway and colorectal cancer (CRC) associated with inflammatory bowel disease (IBD) using a bioinformatics analysis of putative common biomarkers and a systems biology approach.

MATERIALS AND METHODS

The following criteria were used to search the GEO and ArrayExpress databases for terms related to CRC and IBD: 1. The dataset containing the transcriptomic data, and 2. Untreated samples by medications or drugs. A total of 42 datasets were selected for additional analysis. The GEO2R identified the differentially expressed genes. The genes involved in the Wnt signaling pathway were extracted from the KEGG database. Enrichment analysis and miRNA target prediction were conducted through the ToppGene online tool.

RESULTS

In CRC datasets, there were 1168 up- and 998 down-regulated probes, whereas, in IBD datasets, there were 256 up- and 200 down-regulated probes. There were 65 upregulated and 57 downregulated genes shared by CRC and IBD. According to KEGG, there were 166 genes in the Wnt pathway. FriZZled5 (FZD5) was a down-regulated gene in both CRC and IBD, as determined by the intersection of CRC- and IBD-related DEGs with the Wnt pathway. It was also demonstrated that miR-191, miR-885-5p, miR-378a-3p, and miR-396-3p affect the FriZZled5 gene expression.

CONCLUSION

It is possible that increased expression of miR-191 and miR-885-5p, or decreased expression of miR-378a -3p and miR396-3, in IBD and CRC results in decreased expression of the FZD5 gene. Based on the function of this gene, FZD5 may be a potential therapeutic target in IBD that progresses to CRC.

Natural epidithiodiketopiperazine alkaloids as potential anticancer agents: Recent mechanisms of action, structural modification, and synthetic strategies

Cancer has become a grave health crisis that threatens the lives of millions of people worldwide. Because of the drawbacks of the available anticancer drugs, the development of novel and efficient anticancer agents should be encouraged. Epidithiodiketopiperazine (ETP) alkaloids with a 2,5-diketopiperazine (DKP) ring equipped with transannular disulfide or polysulfide bridges or S-methyl moieties constitute a special subclass of fungal natural products. Owing to their privileged sulfur units and intriguing architectural structures, ETP alkaloids exhibit excellent anticancer activities by regulating multiple cancer proteins/signaling pathways, including HIF-1, NF-κB, NOTCH, Wnt, and PI3K/AKT/mTOR, or by inducing cell-cycle arrest, apoptosis, and autophagy. Furthermore, a series of ETP alkaloid derivatives obtained via structural modification showed more potent anticancer activity than natural ETP alkaloids. To solve supply difficulties from natural resources, the total synthetic routes for several ETP alkaloids have been designed. In this review, we summarized several ETP alkaloids with anticancer properties with particular emphasis on their underlying mechanisms of action, structural modifications, and synthetic strategies, which will offer guidance to design and innovate potential anticancer drugs.

Wnt/β-Catenin Signaling Pathway in the Development and Progression of Colorectal Cancer

The Wnt/β-catenin signaling pathway is a growth control pathway involved in various biological processes as well as the development and progression of cancer. Colorectal cancer (CRC) is one of the most common malignancies in the world. The hyperactivation of Wnt signaling is observed in almost all CRC and plays a crucial role in cancer-related processes such as cancer stem cell (CSC) propagation, angiogenesis, epithelial-mesenchymal transition (EMT), chemoresistance, and metastasis. This review will discuss how the Wnt/β-catenin signaling pathway is involved in the carcinogenesis and progression of CRC and related therapeutic approaches.

Novel mutation in LRP5 gene cause rare osteosclerosis: cases studies and literature review

To study the effects of low-density lipoprotein receptor-related protein 5 (LRP5) gene mutations on bone, and to open up our view of LRP5 and Wnt pathways on bone mass regulation. Three patients with increased bone mineral density or thickened bone cortex were included, who were 30-year-old, 22-year-old and 50-year-old men, respectively. The latter two patients were son and father of a same family. The characteristics of bone X-rays were evaluated in detail. Bone turnover markers were detected, such as procollagen type 1 amino-terminal peptide (P1NP), alkaline phosphatase (ALP), and type 1 collagen carboxyl terminal peptide (β-CTX). Dual energy X-ray absorptiometry (DXA) was used to measure the bone mineral density (BMD) at lumbar spine and proximal femur of the patients. The targeted next-generation sequencing (NGS) technology was used to detect pathogenic gene mutations, which were further verified by Sanger sequencing. Moreover, the gene mutation spectrum and phenotypic characteristics of reported patients with LRP5 gain-of-function mutations were summarized by reviewing the literature. The main characteristics of the first patient were headache, facial paralysis, high BMD (lumbar vertebrae 1–4: 1.877 g/cm2, Z-score: 5.8; total hip: 1.705 g/cm2, Z-score: 5.7), slightly increased P1NP (87.0 ng/mL) and β-CTX (0.761 ng/mL) level, and with thickened bone cortex, especially the cranial vault. The latter two patients showed enlargement of the mandible and enlarged osseous prominence of the tours palatinus. X-rays showed that the bone cortex of skull and long bones were thickened. The bone turnover markers and BMD were normal. All three cases carried novel missense mutations in LRP5 gene, which were mutation in exon 3 (c.586 T > G, p.Trp196Gly) of the first patient, and mutation in exon 20 (c.4240C > A, p.Arg1414Ser) of the latter two patients. Combined with the reported literature, a total of 19 gain-of-function mutations in LRP5 were detected in 113 patients from 33 families. Hotspot mutations included c.724G > A, c.512G > T and c.758C > T. Furthermore, mutations in the exon 3 of LRP5 may cause severe phenotypes. LRP5 gain-of-function mutations can lead to rare autosomal dominant osteosclerosis type Ι (ADO Ι), which was characterized by increased bone mass and thickened bone cortex. In-depth research on the Wnt pathway will be benefit for discovering important mechanisms of bone mass regulation.

A rationally designed optochemogenetic switch for activating canonical Wnt signaling

Accurate spatiotemporal control of multicellular self-organization by various signaling pathways is essential for developmental stages. In particular, evolutionarily conserved Wnt signaling serves as a major morphogenetic switch to determine the anteroposterior axis of the embryo. Here, we developed a genetically encoded optochemogenetic Wnt switch, named optochemoWnt, by coupling a blue light-inducible CRY2olig and rapamycin-inducible LRP6c clustering. The rationally designed optochemoWnt successfully modulated Wnt signaling with AND-gated patterns and demonstrated an improved signal-to-noise ratio (SNR). The dual-triggered switch provides a safeguard to prevent signal leakage resulting from ambient light sources under general laboratory conditions. OptochemoWnt expands the molecular toolbox available for the fields of developmental biology and tissue engineering. In addition, the AND-gated strategy of optochemoWnt may be used for other biomedical applications that integrate user defined switch elements with Boolean logic gates.

Extracellular Vesicles Secreted by TGF-β1-Treated Mesenchymal Stem Cells Promote Fracture Healing by SCD1-Regulated Transference of LRP5

Bone fracture repair is a multiphased regenerative process requiring paracrine intervention throughout the healing process. Mesenchymal stem cells (MSCs) play a crucial role in cell-to-cell communication and the regeneration of tissue, but their transplantation is difficult to regulate. The paracrine processes that occur in MSC-derived extracellular vesicles (MSC-EVs) have been exploited for this study. The primary goal was to determine whether EVs secreted by TGF-β1-stimulated MSCs (MSCTGF-β1-EVs) exhibit greater effects on bone fracture healing than EVs secreted by PBS-treated MSCs (MSCPBS-EVs). Our research was conducted using an in vivo bone fracture model and in vitro experiments, which included assays to measure cell proliferation, migration, and angiogenesis, as well as in vivo and in vitro gain/loss of function studies. In this study, we were able to confirm that SCD1 expression and MSC-EVs can be induced by TGF-β1. After MSCTGF-β1-EVs are transplanted in mice, bone fracture repair is accelerated. MSCTGF-β1-EV administration stimulates human umbilical vein endothelial cell (HUVEC) angiogenesis, proliferation, and migration in vitro. Furthermore, we were able to demonstrate that SCD1 plays a functional role in the process of MSCTGF-β1-EV-mediated bone fracture healing and HUVEC angiogenesis, proliferation, and migration. Additionally, using a luciferase reporter assay and chromatin immunoprecipitation studies, we discovered that SREBP-1 targets the promoter of the SCD1 gene specifically. We also discovered that the EV-SCD1 protein could stimulate proliferation, angiogenesis, and migration in HUVECs through interactions with LRP5. Our findings provide evidence of a mechanism whereby MSCTGF-β1-EVs enhance bone fracture repair by regulating the expression of SCD1. The use of TGF-β1 preconditioning has the potential to maximize the therapeutic effects of MSC-EVs in the treatment of bone fractures.

N-Glycosylation of LRP6 by B3GnT2 Promotes Wnt/β-Catenin Signalling

Reception of Wnt signals by cells is predominantly mediated by Frizzled receptors in conjunction with a co-receptor, the latter being LRP6 or LRP5 for the Wnt/β-catenin signalling pathway. It is important that cells maintain precise control of receptor activation events in order to properly regulate Wnt/β-catenin signalling as aberrant signalling can result in disease in humans. Phosphorylation of the intracellular domain (ICD) of LRP6 is well known to regulate Wntβ-catenin signalling; however, less is known for regulatory post-translational modification events within the extracellular domain (ECD). Using a cell culture-based expression screen for functional regulators of LRP6, we identified a glycosyltransferase, B3GnT2-like, from a teleost fish (medaka) cDNA library, that modifies LRP6 and regulates Wnt/β-catenin signalling. We provide both gain-of-function and loss-of-function evidence that the single human homolog, B3GnT2, promotes extension of polylactosamine chains at multiple N-glycans on LRP6, thereby enhancing trafficking of LRP6 to the plasma membrane and promoting Wnt/β-catenin signalling. Our findings further highlight the importance of LRP6 as a regulatory hub in Wnt signalling and provide one of the few examples of how a specific glycosyltransferase appears to selectively target a signalling pathway component to alter cellular signalling events.