Wnt/β-catenin signalling, epithelial-mesenchymal transition and crosslink signalling in colorectal cancer cells

Colorectal cancer (CRC), with its significant incidence and metastatic rates, profoundly affects human health. A common oncogenic event in CRC is the aberrant activation of the Wnt/β-catenin signalling pathway, which drives both the initiation and progression of the disease. Persistent Wnt/β-catenin signalling facilitates the epithelial-mesenchymal transition (EMT), which accelerates CRC invasion and metastasis. This review provides a summary of recent molecular studies on the role of the Wnt/β-catenin signalling axis in regulating EMT in CRC cells, which triggers metastatic pathogenesis. We present a comprehensive examination of the EMT process and its transcriptional controllers, with an emphasis on the crucial functions of β-catenin, EMT transcription factors (EMT-TFs). We also review recent evidences showing that hyperactive Wnt/β-catenin signalling triggers EMT and metastatic phenotypes in CRC via "Destruction complex" of β-catenin mechanisms. Potential therapeutic and challenges approache to suppress EMT and prevent CRC cells metastasis by targeting Wnt/β-catenin signalling are also discussed. These include direct β-catenin inhibitors and novel targets of the Wnt pathway, and finally highlight novel potential combinational treatment options based on the inhibition of the Wnt pathway.

Wnt/β-Catenin Promotes the Osteoblastic Potential of BMP9 Through Down-Regulating Cyp26b1 in Mesenchymal Stem Cells

BACKGROUND

All-trans retinoic acid (ATRA) promotes the osteogenic differentiation induced by bone morphogenetic protein 9 (BMP9), but the intrinsic relationship between BMP9 and ATRA keeps unknown. Herein, we investigated the effect of Cyp26b1, a critical enzyme of ATRA degradation, on the BMP9-induced osteogenic differentiation in mesenchymal stem cells (MSCs), and unveiled possible mechanism through which BMP9 regulates the expression of Cyp26b1.

METHODS

ATRA content was detected with ELISA and HPLC-MS/MS. PCR, Western blot, and histochemical staining were used to assay the osteogenic markers. Fetal limbs culture, cranial defect repair model, and micro-computed tomographic were used to evaluate the quality of bone formation. IP and ChIP assay were used to explore possible mechanism.

RESULTS

We found that the protein level of Cyp26b1 was increased with age, whereas the ATRA content decreased. The osteogenic markers induced by BMP9 were increased by inhibiting or silencing Cyp26b1 but reduced by exogenous Cyp26b1. The BMP9-induced bone formation was enhanced by inhibiting Cyp26b1. The cranial defect repair was promoted by BMP9, which was strengthened by silencing Cyp26b1 and reduced by exogenous Cyp26b1. Mechanically, Cyp26b1 was reduced by BMP9, which was enhanced by activating Wnt/β-catenin, and reduced by inhibiting this pathway. β-catenin interacts with Smad1/5/9, and both were recruited at the promoter of Cyp26b1.

CONCLUSIONS

Our findings suggested the BMP9-induced osteoblastic differentiation was mediated by activating retinoic acid signalling, viadown-regulating Cyp26b1. Meanwhile, Cyp26b1 may be a novel potential therapeutic target for the treatment of bone-related diseases or accelerating bone-tissue engineering.

Berberine inhibits tumour growth in vivo and in vitro through suppressing the lincROR-Wnt/β-catenin regulatory axis in colorectal cancer

BACKGROUND

Berberine, a non-prescription medicine clinically applied for diarrhoea and gastroenteritis. Recent studies have demonstrated that it possesses anti-tumour properties in colorectal cancer, but the exact molecular mechanism remains obscure.

OBJECTIVES

To elucidate the underly molecular mechanisms of berberine in colorectal cancer from a perspective of epigenetics, and tried to explore the role of lincROR-Wnt/β-catenin molecular axis in the berberine induced the anti-tumour activity in colorectal cancer.

METHODS

The effects of berberine on cell growth, cell cycle and apoptosis were examined in CRC cells. The in vivo effect of berberine on tumour growth was investigated using a xenograft mice model. Moreover, lincROR and Wnt/β-catenin signalling were detected by luciferase activity, qRT-PCR and western blotting assays.

KEY FINDINGS

Berberine suppressed cell growth in vitro via inducing cell cycle arrest and apoptosis in CRC cell, and inhibited tumourigenesis in vivo. LincROR was significantly down-regulated by berberine, inducing the inactivation of the canonical Wnt/β-catenin signalling, meanwhile, the overexpression of lincROR partially reversed the suppressive effects on tumour growth and Wnt/β-catenin signalling induced by berberine.

CONCLUSIONS

Berberine inhibits tumour growth partially via regulating the lincROR-Wnt/β-catenin regulatory axis, which provides a strategy for the design of anti-tumour drugs for CRC patients after our advanced validation.

Isoxazole 9 (ISX9), a small molecule targeting Axin, activates Wnt/β-catenin signalling and promotes hair regrowth

BACKGROUND AND PURPOSE

Isoxazole 9 (ISX9) is a neurogenesis-promoting small molecule compound that can up-regulate the expression of NeuroD1 and induce differentiation of neuronal, cardiac and islet endocrine progenitors. So far, the molecular mechanisms underlying the action of ISX9 still remain elusive.

EXPERIMENTAL APPROACH

To identify a novel agonist of the Wnt/β-catenin, a cell-based SuperTOPFlash reporter system was used to screen known-compound libraries. An activation effect of ISX9 on the Wnt/β-catenin pathway was analysed with the SuperTOPFlash or SuperFOPFlash reporter system. Effects of ISX9 on Axin1/LRP6 interaction were examined using a mammalian two-hybrid system, co-immunoprecipitation, microscale thermophoresis, emission spectra and mass spectrometry assays. The expression of Wnt target and stemmness marker genes were evaluated with real-time PCR and immunoblotting. In vivo hair regeneration abilities of ISX9 were analysed by immunohistochemical staining, real-time PCR and immunoblotting in hair regrowth model using C57BL/6J mice.

KEY RESULTS

In this study, ISX9 was identified as a novel agonist of the Wnt/β-catenin pathway. ISX9 targeted Axin1 by covalently binding to its N-terminal region and potentiated the LRP6-Axin1 interaction, thereby resulting in the stabilization of β-catenin and up-regulation of Wnt target genes and stemmness marker genes. Moreover, the topical application of ISX9 markedly promoted hair regrowth in C57BL/6J mice and induced hair follicle transition from telogen to anagen via enhancing Wnt/β-catenin pathway.

CONCLUSIONS AND IMPLICATIONS

Taken together, our study unravelled that ISX9 could activate Wnt/β-catenin signalling by potentiating the association between LRP6 and Axin1, and may be a promising therapeutic agent for alopecia treatment.

Molecular analysis of phenotypic heterogeneity in JAK2V617F-positive myeloproliferative neoplasms reveals a potential target for therapy

JAK2V617F is the most frequent mutation in BCR-ABL-negative myeloproliferative neoplasms (MPNs). It is an important but not the only determinant of MPN phenotype. We performed high-throughput sequencing on JAK2V617F⁺ essential thrombocythaemia (ET) and polycythaemia vera (PV) patient samples to unveil factors involved in phenotypic heterogeneity and to identify novel therapeutic targets for MPN. Two concurrent mutations that may affect phenotype were identified, including mutations in SH2B3, which is primarily prevalent in PV, and SF3B1, which is more commonly mutated in ET. Next, we conducted transcriptomic analysis at the haematopoietic stem cell (HSC) and megakaryocyte (MK)-erythroid progenitor (MEP) levels. Inflammatory signalling pathways were elevated in both ET HSCs and MEPs, unlike in PV HSCs and MEPs. Notably, Wnt/β-catenin signalling was uniquely upregulated during ET haematopoietic differentiation from HSC to MEP, and inhibiting Wnt/β-catenin signalling blocked MK differentiation in vitro. Consistently, Wnt/β-catenin inhibitor administration decreased platelet counts in JAK2V617F⁺ MPN mice by blocking MEPs and MK progenitors and by inhibiting maturation of MKs, while in wild-type mice, Wnt/β-catenin inhibitor did not significantly reduce platelet counts. In conclusion, our findings provide new insights into the mechanisms underlying phenotypic differentiation of JAK2V617F⁺ PV and ET and indicate Wnt/β-catenin signalling as a potential therapeutic target for MPN.

HIF-1α contributes to metastasis in choriocarcinoma by regulating DEC1 expression

PURPOSE

To elucidate the underlying mechanism of HIF-1α in migration and invasion of choriocarcinoma.

METHODS

Cell proliferation was determined by CCK-8 assay when cell invasion was detected by transwell assay. The protein expression was detected by western blotting, immunohistochemistry, and qPCR assay.

RESULT

HIF-1α was shown to be strongly expressed in both clinical tumour tissues and cell lines in choriocarcinoma. When HIF-1α was efficiently knocked down in JEG3 cells, the proliferation rate was reduced by approximately 50% and the number of cells that migrated through the transwell insert was greatly decreased. The cell invasion rate was also significantly reduced. Moreover, typical markers of epithelial-mesenchymal transition such as E-cadherin, were increased, while vimentin and α-SMA were decreased after HIF-1α knockdown. In contrast, overexpression of DEC1 reversed the effects of HIF-1α knockdown. Cell proliferation, migration, and invasion were partially recovered. The level of E-cadherin was decreased, while the level of vimentin and α-SMA was increased. In addition, the level of β-catenin and LEF1 was downregulated after HIF-1α knockdown. The expression of MMP2 and MMP9 also declined. However, overexpression of DEC1 after HIF-1α knockdown partially reversed the expression pattern of these molecules.

CONCLUSION

HIF-1α contributed to EMT and metastasis through activation of canonical β-catenin signalling in choriocarcinoma and this process was dependent on DEC1. This study provides a new mechanism of HIF-1α in choriocarcinoma and suggests that intervention with DEC1 might be a promising therapeutic choice for choriocarcinoma.

METTL14 promotes migration and invasion of choroidal melanoma by targeting RUNX2 mRNA via m6A modification

The modification of N6-methyladenosine is involved in the progression of various cancers. This study aimed to clarify its regulatory mechanism in the pathogenesis of choroidal melanoma. Expression of methyltransferase-like 14 in choroidal melanoma or normal choroidal tissues was determined by Western blot and immunohistochemistry. The impacts of methyltransferase-like 14 on invasion and migration of choroidal melanoma cells were determined using functional and animal experiments. The interaction between methyltransferase-like 14 and its downstream target was identified by methylated RNA immunoprecipitation and a dual-luciferase reporter assay. Additionally, Wnt/β-catenin signalling pathway was evaluated by Western blot. Methyltransferase-like 14 was upregulated in choroidal melanoma compared to the normal choroidal tissues. Overexpression or knockdown of methyltransferase-like 14 enhanced or inhibited the invasion and migration of choroidal melanoma cells, respectively, both in vivo and in vitro. Methyltransferase-like 14 directly targeted downstream runt-related transcription factor 2 mRNA, depending on N6-methyladenosine. Additionally, the Wnt/β-catenin signalling pathway was activated by methyltransferase-like 14 in choroidal melanoma cells. Our study identified a novel RNA regulatory mechanism in which runt-related transcription factor 2 was upregulated by enhanced expression of methyltransferase-like 14 via N6-methyladenosine modification, thus facilitating migration and invasion of choroidal melanoma cells.

Developmental regulation of barrier- and non-barrier blood vessels in the CNS

The blood-brain barrier (BBB) is essential for creating and maintaining tissue homeostasis in the central nervous system (CNS), which is key for proper neuronal function. In most vertebrates, the BBB is localized to microvascular endothelial cells that acquire barrier properties during angiogenesis of the neuroectoderm. Complex and continuous tight junctions, and the lack of fenestrae combined with low pinocytotic activity render the BBB endothelium a tight barrier for water-soluble molecules that may only enter the CNS via specific transporters. The differentiation of these unique endothelial properties during embryonic development is initiated by endothelial-specific flavours of the Wnt/β-catenin pathway in a precise spatiotemporal manner. In this review, we summarize the currently known cellular (neural precursor and endothelial cells) and molecular (VEGF and Wnt/β-catenin) mechanisms mediating brain angiogenesis and barrier formation. Moreover, we introduce more recently discovered crosstalk with cellular and acellular elements within the developing CNS such as the extracellular matrix. We discuss recent insights into the downstream molecular mechanisms of Wnt/β-catenin in particular, the recently identified target genes like Foxf2, Foxl2, Foxq1, Lef1, Ppard, Zfp551, Zic3, Sox17, Apcdd1 and Fgfbp1 that are involved in refining and maintaining barrier characteristics in the mature BBB endothelium. Additionally, we elute to recent insight into barrier heterogeneity and differential endothelial barrier properties within the CNS, focussing on the circumventricular organs as well as on the neurogenic niches in the subventricular zone and the hippocampus. Finally, open questions and future BBB research directions are highlighted in the context of taking benefit from understanding BBB development for strategies to modulate BBB function under pathological conditions.

LRP6 Receptor Plays Essential Functions in Development and Human Diseases

LRP6 is a member of the low-density lipoprotein receptor superfamily of cell-surface receptors. It is required for the activation of the Wnt/β-catenin signalling pathway. LRP6 is detected in different tissue types and is involved in numerous biological activities such as cell proliferation, specification, metastatic cancer, and embryonic development. LRP6 is essential for the proper development of different organs in vertebrates, such as Xenopus laevis, chickens, and mice. In human, LRP6 overexpression and mutations have been reported in multiple complex diseases including hypertension, atherosclerosis, and cancers. Clinical studies have shown that LRP6 is involved in various kinds of cancer, such as bladder and breast cancer. Therefore, in this review, we focus on the structure of LRP6 and its interactions with Wnt inhibitors (DKK1, SOST). We also discuss the expression of LRP6 in different model systems, with emphasis on its function in development and human diseases.

Design, synthesis and structure-activity relationship optimization of phenanthridine derivatives as new anti-vitiligo compounds

Humans have been suffering from vitiligo for a long time. Target vitiligo drugs have yet been approved. Activation of Wnt/β-catenin signalling has potential in the therapeutic use of vitiligo, so exploring new drugs that specifically directly activate Wnt is worthwhile to obtain new anti-vitiligo agents. In this work, two portions design and synthesis were put into effect. firstly, 17 phenanthridine derivatives with C-4 substitutes were designed and synthesized, which compounds 4, 6, 12, 13 served as H-acceptor with protein showed enhance melanogenesis activity; Secondly, 7 hybrid new scaffolds of compounds were designed and synthesized, scaffold hopping compound 36 that aromatic benzene was replaced pyrazole on ring C showed enhance melanogenesis and tyrosinase activity; The last and most important, a comprehensive optimization and SARs of compound 36 were carried out, compounds 41 and 43 shared phenolic hydroxyl or 3-methyl-pyridine substitutes at C-7 position remarkably improved the capacity of melanogenesis and tyrosinase activity. Compound 43 were identified as new anti-vitiligo agents that specifically activate the Wnt/β-catenin signalling pathway by targeting Axin. Structure-activity relationship analysis implied that H-acceptor substitutions at the C-4 position and phenolic hydroxyl or pyridine substitutions at the C-7 position would improve the activities of the compounds. These findings reveal a new therapeutic strategy for vitiligo, and compounds 41 and 43 may represent potential compounds for vitiligo treatment.

Review: The Role of Wnt/β-Catenin Signalling in Neural Crest Development in Zebrafish

The neural crest (NC) is a multipotent cell population in vertebrate embryos with extraordinary migratory capacity. The NC is crucial for vertebrate development and forms a myriad of cell derivatives throughout the body, including pigment cells, neuronal cells of the peripheral nervous system, cardiomyocytes and skeletogenic cells in craniofacial tissue. NC induction occurs at the end of gastrulation when the multipotent population of NC progenitors emerges in the ectodermal germ layer in the neural plate border region. In the process of NC fate specification, fate-specific markers are expressed in multipotent progenitors, which subsequently adopt a specific fate. Thus, NC cells delaminate from the neural plate border and migrate extensively throughout the embryo until they differentiate into various cell derivatives. Multiple signalling pathways regulate the processes of NC induction and specification. This review explores the ongoing role of the Wnt/β-catenin signalling pathway during NC development, focusing on research undertaken in the Teleost model organism, zebrafish (Danio rerio). We discuss the function of the Wnt/β-catenin signalling pathway in inducing the NC within the neural plate border and the specification of melanocytes from the NC. The current understanding of NC development suggests a continual role of Wnt/β-catenin signalling in activating and maintaining the gene regulatory network during NC induction and pigment cell specification. We relate this to emerging models and hypotheses on NC fate restriction. Finally, we highlight the ongoing challenges facing NC research, current gaps in knowledge, and this field's potential future directions.

Huoxin pill prevents acute myocardial ischaemia injury via inhibition of Wnt/β-catenin signaling

Myocardial infarction (MI) is one of the leading causes of death worldwide, and due to the widespread and irreversible damage caused, new therapeutic treatments are urgently needed in order to limit the degree of ischaemic damage following MI. Aberrant activation of Wnt/β‐catenin signalling pathway often occurs during cardiovascular diseases including MI, which results in excess production of reactive oxygen species (ROS) and further promotes myocardial dysfunction. Huoxin pill (HXP) is a Traditional Chinese Medicine formula that has been widely used in the treatment of coronary heart disease and angina; however, its mechanisms remain unclear. Here, we performed mouse models of MI and examined the effects and mechanisms of HXP in protecting against MI‐induced ischaemic damage. Our study showed that administration with HXP robustly protected against MI‐induced cardiac injuries, decreased infarct size and improved cardiac function. Moreover, HXP attenuated ischaemia‐induced DNA damage occurrence in vivo and H₂O₂‐induced DNA damage occurrence in vitro, via potent inhibition of adverse Wnt/β‑catenin signalling activation. Our study thus elucidated the role and mechanism of HXP in protecting against MI and oxidative stress‐induced injuries and suggests new therapeutic strategies in ischaemic heart disease via inhibition of Wnt/β‐catenin signalling pathway.

Starvation induced autophagy promotes the progression of bladder cancer by LDHA mediated metabolic reprogramming

Background

Aberrant autophagy and preternatural elevated glycolysis are prevalent in bladder cancer (BLCA) and are both related to malignant progression. However, the regulatory relationship between autophagy and glycolytic metabolism remains largely unknown. We imitated starvation conditions in the tumour microenvironment and found significantly increased levels of autophagy and aerobic glycolysis, which both regulated the progression of BLCA cells. We further explored the regulatory relationships and mechanisms between them.

Methods

We used immunoblotting, immunofluorescence and transmission electron microscopy to detect autophagy levels in BLCA cells under different treatments. Lactate and glucose concentration detection demonstrated changes in glycolysis. The expression of lactate dehydrogenase A (LDHA) was detected at the transcriptional and translational levels and was also silenced by small interfering RNA, and the effects on malignant progression were further tested. The underlying mechanisms of signalling pathways were evaluated by western blot, immunofluorescence and immunoprecipitation assays.

Results

Starvation induced autophagy, regulated glycolysis by upregulating the expression of LDHA and caused progressive changes in BLCA cells. Mechanistically, after starvation, the ubiquitination modification of Axin1 increased, and Axin1 combined with P62 was further degraded by the autophagy–lysosome pathway. Liberated β-catenin nuclear translocation increased, binding with LEF1/TCF4 and promoting LDHA transcriptional expression. Additionally, high expression of LDHA was observed in cancer tissues and was positively related to progression.

Conclusion

Our study demonstrated that starvation-induced autophagy modulates glucose metabolic reprogramming by enhancing Axin1 degradation and β-catenin nuclear translocation in BLCA, which promotes the transcriptional expression of LDHA and further malignant progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02303-1.

RNF43 overexpression attenuates the Wnt/β-catenin signalling pathway to suppress tumour progression in cholangiocarcinoma

RING finger protein 43 (RNF43) is a ubiquitin E3 ligase that negatively regulates Wnt/β-catenin signalling. Mutation, inactivation and downregulation of RNF43 in cholangiocarcinoma (CCA) are associated with a less favourable prognosis. Since the functional role of RNF43 in CCA has not yet been demonstrated, the present study aimed to assess the effect of its overexpression in mediating CCA suppression via Wnt/β-catenin signalling pathway inhibition. Accordingly, RNF43 was overexpressed, and various malignant phenotypic changes studied, including cell proliferation, cell migration, chemotherapeutic sensitivity and the expression of several Wnt/β-catenin target genes. Overexpression of RNF43 in the CCA cell-line KKU-213B hindered activation of Wnt/β-catenin signalling, evidenced by: i) Accumulation of β-catenin in the cytoplasmic fraction and downregulation of several known Wnt target genes at the mRNA level [AXIN2, survivin (BIRC5), CCND1, MMP-7, c-MYC and ABCB1 (MDR1)]; ii) a reduction of cell proliferation; iii) a significant decrease in KKU-213B cell migration with RNF43 overexpression via upregulation of E-cadherin (CDH1); and iv) a reduction in N-cadherin (CDH2), MMP-2, MMP-7 and MMP-9. In addition, overexpression of RNF43 increased 5-fluorouracil sensitivity and downregulation of ABC transporter genes [including ABCB1 and ABCC1 (MRP1)]. The current results demonstrate a functional role for RNF43 in CCA by: i) Blocking β-catenin nuclear translocation; and ii) the subsequent downregulation of Wnt/β-catenin target genes (the latter being involved in the progression of CCA and chemotherapeutic drug susceptibility). Therefore, the present findings suggest that RNF43 could serve a tumour suppressive role in CCA.

Fractalkine aggravates LPS-induced macrophage activation and acute kidney injury via Wnt/β-catenin signalling pathway

Fractalkine (CX3CL1, FKN), a CX3C gene sequence inflammatory chemokine, has been found to have pro-inflammatory and pro-adhesion effects. Macrophages are immune cells with a critical role in regulating the inflammatory response. The imbalance of M1/M2 macrophage polarization can lead to aggravated inflammation. This study attempts to investigate the mechanisms through which FKN regulates macrophage activation and the acute kidney injury (AKI) involved in inflammatory response induced by lipopolysaccharide (LPS) by using FKN knockout (FKN-KO) mice and cultured macrophages. It was found that FKN and Wnt/β-catenin signalling have a positive interaction in macrophages. FKN overexpression inhibited LPS-induced macrophage apoptosis. However, it enhanced their cell viability and transformed them into the M2 type. The effects of FKN overexpression were accelerated by activation of Wnt/β-catenin signalling. In the in vivo experiments, FKN deficiency suppressed macrophage activation and reduced AKI induced by LPS. Inhibition of Wnt/β-catenin signalling and FKN deficiency further mitigated the pathologic process of AKI. In summary, we provide a novel mechanism underlying activation of macrophages in LPS-induced AKI. Although LPS-induced murine AKI was unable to completely recapitulate human AKI, the positive interactions between FKN and Wnt/β-catenin signalling pathway may be a therapeutic target in the treatment of kidney injury.

Persistent Newcastle disease virus infection in bladder cancer cells is associated with putative pro-survival and anti-viral transcriptomic changes

Background

Newcastle disease virus (NDV) is an oncolytic virus with excellent selectivity against cancer cells, both in vitro and in vivo. Unfortunately, prolonged in vitro NDV infection results in the development of persistent infection in the cancer cells which are then able to resist NDV-mediated oncolysis. However, the mechanism of persistency of infection remains poorly understood.

Methods

In this study, we established persistently NDV-infected EJ28 bladder cancer cells, designated as EJ28P. Global transcriptomic analysis was subsequently carried out by microarray analysis. Differentially expressed genes (DEGs) between EJ28 and EJ28P cells identified by the edgeR program were further analysed by Gene Set Enrichment Analysis (GSEA) and Ingenuity Pathway Analysis (IPA) analyses. In addition, the microarray data were validated by RT-qPCR.

Results

Persistently NDV-infected EJ28 bladder cancer cells were successfully established and confirmed by flow cytometry. Microarray analysis identified a total of 368 genes as differentially expressed in EJ28P cells when compared to the non-infected EJ28 cells. GSEA revealed that the Wnt/β-catenin and KRAS signalling pathways were upregulated while the TGF-β signalling pathway was downregulated. Findings from this study suggest that the upregulation of genes that are associated with cell growth, pro-survival, and anti-apoptosis may explain the survivability of EJ28P cells and the development of persistent infection of NDV.

Conclusions

This study provides insights into the transcriptomic changes that occur and the specific signalling pathways that are potentially involved in the development and maintenance of NDV persistency of infection in bladder cancer cells. These findings warrant further investigation and is crucial towards the development of effective NDV oncolytic therapy against cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08345-y.

KY19382, a novel activator of Wnt/β-catenin signalling, promotes hair regrowth and hair follicle neogenesis

Background and Purpose

The promotion of hair regeneration and growth heavily depends on the activation of Wnt/β‐catenin signalling in the hair follicle, including dermal papilla (DP). KY19382, one of the newly synthesized analogues of indirubin‐3′‐monoxime (I3O), was identified as a Wnt/β‐catenin signalling activator via inhibition of the interaction between CXXC‐type zinc finger protein 5 (CXXC5) and dishevelled (Dvl). Given the close relationship between the Wnt/β‐catenin signalling and hair regeneration, we investigated the effect of KY19382 on hair regrowth and hair follicle neogenesis.

Experimental Approach

In vitro hair induction effects of KY19382 were performed in human DP cells. The hair elongation effects of KY19382 were confirmed through the human hair follicle and vibrissa culture system. In vivo hair regeneration abilities of KY19382 were identified in three models: hair regrowth, wound‐induced hair follicle neogenesis (WIHN) and hair patch assays using C57BL/6 mice. The hair regeneration abilities were analysed by immunoblotting, alkaline phosphatase (ALP) and immunohistochemical staining.

Key Results

KY19382 activated Wnt/β‐catenin signalling and elevated expression of ALP and the proliferation marker PCNA in DP cells. KY19382 also increased hair length in ex vivo‐cultured mouse vibrissa and human hair follicles and induced hair regrowth in mice. Moreover, KY19382 significantly promoted the generation of de novo hair follicles as shown by WIHN and hair patch assays.

Conclusion and Implications

These results indicate that KY19382 is a potential therapeutic drug that exhibits effective hair regeneration ability via activation of the Wnt/β‐catenin signalling for alopecia treatments.

Activation of Wnt/β-catenin signalling and HIF1α stabilisation alters pluripotency and differentiation/proliferation properties of human-induced pluripotent stem cells

BACKGROUND INFORMATION

Wnt/β-catenin signalling, in the microenvironment of pluripotent stem cells (PSCs), plays a critical role in their differentiation and proliferation. Contradictory reports on the role of Wnt/β-catenin signalling in PSCs self-renewal and differentiation, however, render these mechanisms largely unclear.

RESULTS

Wnt/β-catenin signalling pathway in human-induced pluripotent stem cells (hiPSCs) was activated by inhibiting glycogen synthase kinase 3 (GSK3), driving the cells into a mesodermal/mesenchymal state, exhibiting proliferative, invasive and anchorage-independent growth properties, where over 70% of cell population became CD 44 (+)/CD133 (+). Wnt/β-catenin signalling activation also altered the metabolic state of hiPSCs from aerobic glycolysis to oxidative metabolism and changed their drug and oxidative stress sensitivities. These effects of GSK3 inhibition were suppressed in HIF1α-stabilised cells.

CONCLUSIONS

Persistent activation of Wnt/β-catenin signalling endows hiPSCs with proliferative/invasive 'teratoma-like' states, shifting their metabolic dependence and allowing HIF1α-stabilisation to inhibit their proliferative/invasive properties.

SIGNIFICANCE

The hiPSC potential to differentiate into 'teratoma-like' cells suggest that stem cells may exist in two states with differential metabolic and drug dependency.

Evidence for functional and regulatory cross-talk between Wnt/β-catenin signalling and Mre11-Rad50-Nbs1 complex in the repair of cisplatin-induced DNA cross-links

The canonical Wnt/β-catenin signalling pathway plays a crucial role in a variety of functions including cell proliferation and differentiation, tumorigenic processes and radioresistance in cancer cells. The Mre11–Rad50–Nbs1 (MRN) complex has a pivotal role in sensing and repairing DNA damage. However, it remains unclear whether a connection exists between Wnt/β-catenin signalling and the MRN complex in the repair of cisplatin-induced DNA interstrand cross-links (ICLs). Here, we report that (1) cisplatin exposure results in a significant increase in the levels of MRN complex subunits in human tumour cells; (2) cisplatin treatment stimulates Wnt/β-catenin signalling through increased β-catenin expression; (3) the functional perturbation of Wnt/β-catenin signalling results in aberrant cell cycle dynamics and the activation of DNA damage response and apoptosis; (4) a treatment with CHIR99021, a potent and selective GSK3β inhibitor, augments cisplatin-induced cell death in cancer cells. On the other hand, inactivation of the Wnt/β-catenin signalling with FH535 promotes cell survival. Consistently, the staining pattern of γH2AX-foci is significantly reduced in the cells exposed simultaneously to cisplatin and FH535; and (5) inhibition of Wnt/β-catenin signalling impedes cisplatin-induced phosphorylation of Chk1, abrogates the G2/M phase arrest and impairs recombination-based DNA repair. Our data further show that Wnt signalling positively regulates the expression of β-catenin, Mre11 and FANCD2 at early time points, but declining thereafter due to negative feedback regulation. These results support a model wherein Wnt/β-catenin signalling and MRN complex crosstalk during DNA ICL repair, thereby playing an important role in the maintenance of genome stability.

Osteogenic differentiation potential of human bone marrow-derived mesenchymal stem cells enhanced by bacoside-A

Stem cell therapy is growing rapidly to treat numerous diseases including bone-associated diseases. Mesenchymal stem cells (MSCs) are most commonly preferred to treat bone diseases because it possesses high osteogenic potency. Though, to obtain maximum osteogenic efficiency of MSCs is challenging. Therefore, this study was planned to evaluate the osteogenic efficiency of human bone marrow derived mesenchymal stem cells (hBMSCs) by bacoside-A. This study was investigated the activity of alkaline phosphatase (ALP) and expressions of the genes specific to osteogenic regulation mainly runt-related transcription factor 2 (Runx2), osterix (Osx), osteocalcin (OCN) and collagen type Iα1 (Col I α1) in hBMSCs cultured under osteogenic conditions at different concentrations of bacoside-A for 14 days. The results of this study depicted significant upregulation in the activity of ALP and expressions of osteogenic regulator genes in bacoside-A treated cells when compared with control cells. Besides, expressions of glycogen synthase kinase-3β (GSK-3β) and Wnt/β-catenin were evaluated; these expressions were also significantly increased in bacoside-A treated cells when compared with control cells. This result provides a further supporting evidence of bacoside-A role on osteogenesis in hBMSCs. The present study suggest that bacoside-A will be applied to ameliorate the process of osteogenesis in hBMSCs to repair damaged bone structure during MSC-based therapy; this will be an excellent and auspicious treatment for bone-associated disorders including osteoporosis. Significance of the study Osteoporosis is a bone metabolic disorder characterized by an imbalance between the activity of osteoblastic bone formation and osteoclastic bone resorption that disrupts the bone microarchitecture. Current anti-osteoporotic drugs are inhibiting bone resorption, but they are unable to restore the bone structure due to extreme bone remodelling process and causes numerous side effects. The finding of natural bioactive compounds with osteogenic property is very essential for osteoporosis treatment. This study was reported that bacoside-A ameliorated osteogenic differentiation of hBMSCs through upregulation of osteogenic differentiation genes and Wnt/β-catenin signalling pathway. This result is indicating that bacoside-A may be useful for osteoporosis treatments.

CHANGES OF WNT/B-CATENIN SIGNALING AND DIFFERENTIATION POTENTIAL OF BONE MARROW MESENCHYMAL STEM CELLS IN PROCESS OF BONE LOSS IN OVARIECTOMIZED RATS

Background

In vitro studies of the changes about osteoblastogenesis and adipogenesis potential of BMSCs were not clear. As it is the critical pathway for osteogenic differentiation and bone formation, whether or not Wnt/β-catenin signalling is involved in the changes of osteogenic and adipogenic potential of BMSCs and participates in bone content decrease of ovariectomized (OVX)osteoporosis rats has been rarely reported.

Material/Methods

BMSCs from femurs of ovariectomzed rats were isolated and cultured in vitro. The proliferation potential of BMSCs was analysed by CCK-8 assays . Osteoblastic and adipogenic differentiation potential of the BMSCs was assessed by ALP activity assay, Alizarin red S staining, Oil red O staining and RT-PCR analysis.

Results

The results demonstrated that BMSCs from bilateral ovariectomization rats were endowed with lower proliferation and osteoblastic differentiation potential but higher adipogenic potential than the control group in vitro. In addition, β-catenin was found to have been decreased in OVX BMSCs, indicating that Wnt/β-catenin signalling pathways were suppressed in OVX BMSCs .

Conclusions

Results suggested that changes in the Wnt canonical signalling pathway may be related to imbalances of osteogenic and adipogenic potential of BMSCs, and this may be an important factor related to bone content decrease in ovariectomized osteoporosis rats.

Human amniotic mesenchymal stem cells inhibit hepatocellular carcinoma in tumour-bearing mice

Hepatocellular carcinoma (HCC) is the third leading cause of the cancer‐related death in the world. Human amniotic mesenchymal stem cells (hAMSCs) have been characterized with a pluripotency, low immunogenicity and no tumorigenicity. Especially, the immunosuppressive and anti‐inflammatory effects of hAMSCs make them suitable for treating HCC. Here, we reported that hAMSCs administrated by intravenous injection significantly inhibited HCC through suppressing cell proliferation and inducing cell apoptosis in tumour‐bearing mice with Hepg2 cells. Cell tracking experiments with GFP‐labelled hAMSCs showed that the stem cells possessed the ability of migrating to the tumorigenic sites for suppressing tumour growth. Importantly, both hAMSCs and the conditional media (hAMSC‐CM) have the similar antitumour effects in vitro, suggesting that hAMSCs‐derived cytokines might be involved in their antitumour effects. Antibody array assay showed that hAMSCs highly expressed dickkopf‐3 (DKK‐3), dickkopf‐1 (DKK‐1) and insulin‐like growth factor‐binding protein 3 (IGFBP‐3). Furthermore, the antitumour effects of hAMSCs were further confirmed by applications of the antibodies or the specific siRNAs of DKK‐3, DKK‐1 and IGFBP‐3 in vitro. Mechanically, hAMSCs‐derived DKK‐3, DKK‐1 and IGFBP‐3 markedly inhibited cell proliferation and promoted apoptosis of Hepg2 cells through suppressing the Wnt/β‐catenin signalling pathway and IGF‐1R‐mediated PI3K/AKT signalling pathway, respectively. Taken together, our study demonstrated that hAMSCs possess significant antitumour effects in vivo and in vitro and might provide a novel strategy for HCC treatment clinically.

Interfering with long non-coding RNA MIR22HG processing inhibits glioblastoma progression through suppression of Wnt/β-catenin signalling

Long non-coding RNAs play critical roles in tumour progression. Through analysis of publicly available genomic datasets, we found that MIR22HG, the host gene of microRNAs miR-22-3p and miR-22-5p, is ranked among the most dysregulated long non-coding RNAs in glioblastoma. The main purpose of this work was to determine the impact of MIR22HG on glioblastoma growth and invasion and to elucidate its mechanistic function. The MIR22HG/miR-22 axis was highly expressed in glioblastoma as well as in glioma stem-like cells compared to normal neural stem cells. In glioblastoma, increased expression of MIR22HG is associated with poor prognosis. Through a number of functional studies, we show that MIR22HG silencing inhibits the Wnt/β-catenin signalling pathway through loss of miR-22-3p and -5p. This leads to attenuated cell proliferation, invasion and in vivo tumour growth. We further show that two genes, SFRP2 and PCDH15, are direct targets of miR-22-3p and -5p and inhibit Wnt signalling in glioblastoma. Finally, based on the 3D structure of the pre-miR-22, we identified a specific small-molecule inhibitor, AC1L6JTK, that inhibits the enzyme Dicer to block processing of pre-miR-22 into mature miR-22. AC1L6JTK treatment caused an inhibition of tumour growth in vivo. Our findings show that MIR22HG is a critical inducer of the Wnt/β-catenin signalling pathway, and that its targeting may represent a novel therapeutic strategy in glioblastoma patients.

Parkinson's disease, aging and adult neurogenesis: Wnt/β-catenin signalling as the key to unlock the mystery of endogenous brain repair

A common hallmark of age-dependent neurodegenerative diseases is an impairment of adult neurogenesis. Wingless-type mouse mammary tumor virus integration site (Wnt)/β-catenin (WβC) signalling is a vital pathway for dopaminergic (DAergic) neurogenesis and an essential signalling system during embryonic development and aging, the most critical risk factor for Parkinson's disease (PD). To date, there is no known cause or cure for PD. Here we focus on the potential to reawaken the impaired neurogenic niches to rejuvenate and repair the aged PD brain. Specifically, we highlight WβC-signalling in the plasticity of the subventricular zone (SVZ), the largest germinal region in the mature brain innervated by nigrostriatal DAergic terminals, and the mesencephalic aqueduct-periventricular region (Aq-PVR) Wnt-sensitive niche, which is in proximity to the SNpc and harbors neural stem progenitor cells (NSCs) with DAergic potential. The hallmark of the WβC pathway is the cytosolic accumulation of β-catenin, which enters the nucleus and associates with T cell factor/lymphoid enhancer binding factor (TCF/LEF) transcription factors, leading to the transcription of Wnt target genes. Here, we underscore the dynamic interplay between DAergic innervation and astroglial-derived factors regulating WβC-dependent transcription of key genes orchestrating NSC proliferation, survival, migration and differentiation. Aging, inflammation and oxidative stress synergize with neurotoxin exposure in "turning off" the WβC neurogenic switch via down-regulation of the nuclear factor erythroid-2-related factor 2/Wnt-regulated signalosome, a key player in the maintenance of antioxidant self-defense mechanisms and NSC homeostasis. Harnessing WβC-signalling in the aged PD brain can thus restore neurogenesis, rejuvenate the microenvironment, and promote neurorescue and regeneration.

LncRNA TUG1 alleviates cardiac hypertrophy by targeting miR-34a/DKK1/Wnt-β-catenin signalling

The current study was designed to explore the role and underlying mechanism of lncRNA taurine up‐regulated gene 1 (TUG1) in cardiac hypertrophy. Mice were treated by transverse aortic constriction (TAC) surgery to induce cardiac hypertrophy, and cardiomyocytes were treated by phenylephrine (PE) to induce hypertrophic phenotype. Haematoxylin‐eosin (HE), wheat germ agglutinin (WGA) and immunofluorescence (IF) were used to examine morphological alterations. Real‐time PCR, Western blots and IF staining were used to detect the expression of RNAs and proteins. Luciferase assay and RNA pull‐down assay were used to verify the interaction. It is revealed that TUG1 was up‐regulated in the hearts of mice treated by TAC surgery and in PE‐induced cardiomyocytes. Functionally, overexpression of TUG1 alleviated cardiac hypertrophy both in vivo and in vitro. Mechanically, TUG1 sponged and sequestered miR‐34a to increase the Dickkopf 1 (DKK1) level, which eventually inhibited the activation of Wnt/β‐catenin signalling. In conclusion, the current study reported the protective role and regulatory mechanism of TUG1 in cardiac hypertrophy and suggested that TUG1 may serve as a novel molecular target for treating cardiac hypertrophy.

The dynamic expression of canonical Wnt/β-catenin signalling pathway in the pathologic process of experimental autoimmune neuritis

Background: Guillain-Barré syndrome (GBS), an autoimmune disease and an acute inflammation disorder, is currently the most frequent cause of acute flaccid paralysis worldwide. EAN, an animal model of GBS, is a CD4+ T cell-mediated autoimmune disease of the PNS. Wnt/β-catenin signals are critically important to several fundamental aspects of peripheral nerve development and play a crucial role in Schwann cell proliferation. Here, we investigate the role of Wnt/β-catenin signalling cascades in EAN rats.Methods: 28 male Lewis rats weighing 170 ± 10 g were randomly divided into control group (n = 7) and EAN groups (Early group; Peak group and Recovery group. n = 7 per group). EAN rats were immunized with P2_57-81 peptide; weighed daily, and the neurologic signs of EAN were evaluated every day. The sciatic nerve was taken on the days 10, 17, and 30 p.i. for H&E staining, transmission electron microscopy and immunohistochemical staining; blood samples were collected weekly from caudal vein to detect IFN-γ, IL-4, TGF-β1; and the sciatic nerve was taken to examinate the dynamics expression of Wnt/β-catenin pathway molecules.Results: In our study, we chose tail-root injection to better model GBS. Moreover, we observed that IFN-γ levels paralleled clinical EAN, and the levels of TGF-β1 and IL-4 gradually increased and peaked in the recovery phase. In addition, we have shown that canonical Wnt signalling is upregulated and reached a peak in the late recovery phase.Conclusion: Our findings suggest that Wnt/β-catenin signalling is associated with the promotion of remyelination in EAN rats.

Wnt/β-catenin signalling in ovarian cancer: Insights into its hyperactivation and function in tumorigenesis

Epithelial ovarian cancer (EOC) is the deadliest female malignancy. The Wnt/β-catenin pathway plays critical roles in regulating embryonic development and physiological processes. This pathway is tightly regulated to ensure its proper activity. In the absence of Wnt ligands, β-catenin is degraded by a destruction complex. When the pathway is stimulated by a Wnt ligand, β-catenin dissociates from the destruction complex and translocates into the nucleus where it interacts with TCF/LEF transcription factors to regulate target gene expression. Aberrant activation of this pathway, which leads to the hyperactivity of β-catenin, has been reported in ovarian cancer. Specifically, mutations of CTNNB1, AXIN, or APC, have been observed in the endometrioid and mucinous subtypes of EOC. In addition, upregulation of the ligands, abnormal activation of the receptors or intracellular mediators, disruption of the β-catenin destruction complex, inhibition of the association of β-catenin/E-cadherin on the cell membrane, and aberrant promotion of the β-catenin/TCF transcriptional activity, have all been reported in EOC, especially in the high grade serous subtype. Furthermore, several non-coding RNAs have been shown to regulate EOC development, in part, through the modulation of Wnt/β-catenin signalling. The Wnt/β-catenin pathway has been reported to promote cancer stem cell self-renewal, metastasis, and chemoresistance in all subtypes of EOC. Emerging evidence also suggests that the pathway induces ovarian tumor angiogenesis and immune evasion. Taken together, these studies demonstrate that the Wnt/β-catenin pathway plays critical roles in EOC development and is a strong candidate for the development of targeted therapies.

Methionine promotes the development of hair follicles via the Wnt/β-catenin signalling pathway in Rex rabbits

To investigate the effect and molecular mechanism of methionine (Met) on the growth of hair follicles (HFs) in Rex rabbits. A total of 200 weaning Rex rabbits were divided into four groups and fed varying levels of Met-supplemented diets. We measured the HF density on dorsal skin and the Wnt/β-catenin pathway protein expression level. Meanwhile, whole HFs were isolated from Rex rabbit skins and cultured with Met in vitro to measure hair shaft growth. The relationship between Met and the Wnt/β-catenin signalling pathway was also characterized by using the Wnt/β-catenin signalling inhibitor, XAV-939. The results showed that the addition of dietary Met could significantly increase the HF density on dorsal skin (p < .05) and enhance the protein expression level of Wnt10b (p < .05), β-catenin (p < .05) and DSH (p < .05). Methionine stimulation could also prolong the hair shafts growth in vitro (p < .05). And inhibition of Wnt/β-catenin signalling using XAV-939 could eliminate this phenomenon. In summary, Met can increase the density of HFs on dorsal skin in vitro and prolong the hair shaft growth of HFs in vivo via the Wnt/β-catenin signalling pathway.

Jatrorrhizine inhibits mammary carcinoma cells by targeting TNIK mediated Wnt/β-catenin signalling and epithelial-mesenchymal transition (EMT)

BACKGROUND

Traf2 and Nck interacting serine protein kinase (TNIK) is a tumour target protein which its high expression is closely related to the occurrence and development of mammary carcinoma cells. Molecular docking revealed that jatrorrhizine, a protoberberine alkaloid, exhibits good binding affinity and interaction with TNIK. However, the underlying mechanisms of jatrorrhizine targeting TNIK inhibits the proliferation and metastasis of breast cancer cells remain unclear.

METHODS

To figure out the mechanisms in vitro and in vivo, the CRISPR/Cas9 technology was used to knockout TNIK gene and detected qualitatively by immunofluorescence and immunoblotting assay. The MTT cell viability assay for cytotoxicity test, the apoptosis were detected by flow cytometry, the migration and invasion were evaluated by colony formation, wound healing assay and cell invasion assay, respectively. Anticancer effects were further corroborated by 4T1/Luc homograft tumour model.

RESULTS

The results showed that targeted knockout of TNIK that attenuated Wnt/β-catenin signalling and epithelial-mesenchymal transition (EMT) expression, the effects were potentiated by the addition of jatrorrhizine. Moreover, jatrorrhizine distinctly inhibited the proliferation of MDA-MB-231, MCF-7 and 4T1 cells with IC₅₀ values of 11.08 ± 1.19 μM, 17.11 ± 4.54 μM and 22.14 ± 2.87 μM, induced mitochondrial dysfunction and early apoptosis involving mitochondrial apoptotic pathway. These results were further corroborated by the 4T1 tumour-bearing mice, which showed that jatrorrhizine significantly suppressed the proliferation and metastasis of mammary carcinoma cells without obvious toxicity.

CONCLUSION

These findings provide an overall perspective that jatrorrhizine potentially restrains TNIK regulating Wnt/β-catenin signalling and EMT expression for mammary cancer targeted therapy.

Downregulated MEG3 contributes to tumour progression and poor prognosis in oesophagal squamous cell carcinoma by interacting with miR-4261, downregulating DKK2 and activating the Wnt/β-catenin signalling

Long noncoding RNA (lncRNA) MEG3 has been widely reported to be decreased in a growing list of primary human tumours and play a key role in tumour suppression. However, there are few reports about MEG3 expression and function in oesophagal squamous cell carcinoma (ESCC). Here, we found that MEG3 expression was significantly downregulated in tumour tissues, and its low expression was associated with large tumour size, lymph node metastasis and advanced clinical stage in ESCC patients. Univariate and multivariate analyses revealed low expression of MEG3 as an independent predictor for disease-free survival and overall survival. Cell experiments showed that MEG3 inhibited ESCC cell proliferation, migration and invasion. Subsequently, miR-4261 was identified and confirmed to be the target of MEG3, and MEG3 functions, at least in part, by targeting miR-4261. Additionally, Dickkopf-2 (DKK2), a Wnt/β-catenin signalling inhibitor, was identified to be a target of miR-4261. MEG3 interacted with miR-4261, derepressed DKK2 and blocked the Wnt/β-catenin signalling, thereby inhibiting tumourigenesis and progression in ESCC. In vivo experiments also confirmed this conclusion. Our study for the first time elaborated the critical role of MEG3-miR-4261-DKK2-Wnt/β-catenin signalling axis in ESCC, and MEG3 could represent a novel diagnostic and prognostic biomarker and therapeutic target in ESCC.

Ginkgolide B promotes osteoblast differentiation via activation of canonical Wnt signalling and alleviates osteoporosis through a bone anabolic way

Osteoporosis has become a worldwide problem as the population ages. Although many advances have been made in the treatment of osteoporosis in the past few years, the outcome are sometimes disturbing because of the adverse effects of these treatments. Further studies are still needed to identify novel alternate agents to improve the therapeutic effect. Ginkgolide B (GB), a derivative of Ginkgo biloba leaves, has numerous pharmacological effects, including anticancer and anti-inflammation activities. However, the effect of GB on the regulation of osteoblast activity and bone formation effect has not yet been investigated. In this study, we showed the in vitro and in vivo effects of GB on osteoblast differentiation and bone formation. We found that GB promotes osteoblast differentiation of Bone Mesenchymal Stem Cells (BMSCs) and MC3T3-E1 cells in vitro in a Wnt/β-catenin-dependent manner. In an in vivo study, we constructed a cranial defect model in rats and treated with GB. Histomorphometric and histological analyses confirmed that the usage of GB significantly promotes bone formation. Further study on ovariectomy (OVX) rats demonstrated that GB is capable of alleviating ovariectomy-induced bone loss by enhancing osteoblast activity. Our findings indicate that GB is a potential therapeutic agent of osteoporosis through an anabolic way in bone.

A comparison of lithium-substituted phosphate and borate bioactive glasses for mineralised tissue repair

OBJECTIVES

Wnt/β-catenin signalling plays important roles in regeneration, particularly in hard tissues such as bone and teeth, and can be regulated by small molecule antagonists of glycogen synthase kinase 3 (GSK3); however, small molecules can be difficult to deliver clinically. Lithium (Li) is also a GSK3 antagonist and can be incorporated into bioactive glasses (BG), which can be used clinically in dental and bone repair applications and tuned to quickly release their constituent ions.

METHODS

Here, we created phosphate (P)- and borate (B)-based BG that also contained Li (LiPBG and LiBBG) and examined their ion release kinetics and the toxicity of their dissolution ions on mouse 17IA4 dental pulp cells.

RESULTS

We found that although LiPBG and LiBBG can both quickly release Li at concentrations known to regulate Wnt/β-catenin signalling, the P and B ions they concomitantly release are highly toxic to cells. Only when relatively low concentrations of LiPBG and LiBBG were placed in cell culture medium were their dissolution products non-toxic. However, at these concentrations, LiPBG and LiBBG's ability to regulate Wnt/β-catenin signalling was limited.

SIGNIFICANCE

These data suggest that identifying a BG composition that can both quickly deliver high concentrations of Li and is non-toxic remains a challenge.

EMT Regulation by Autophagy: A New Perspective in Glioblastoma Biology

Epithelial-to-mesenchymal transition (EMT) and its reverse process MET naturally occur during development and in tissue repair in vertebrates. EMT is also recognized as the crucial event by which cancer cells acquire an invasive phenotype through the activation of specific transcription factors and signalling pathways. Even though glial cells have a mesenchymal phenotype, an EMT-like process tends to exacerbate it during gliomagenesis and progression to more aggressive stages of the disease. Autophagy is an evolutionary conserved degradative process that cells use in order to maintain a proper homeostasis, and defects in autophagy have been associated to several pathologies including cancer. Besides modulating cell resistance or sensitivity to therapy, autophagy also affects the migration and invasion capabilities of tumor cells. Despite this evidence, few papers are present in literature about the involvement of autophagy in EMT-like processes in glioblastoma (GBM) so far. This review summarizes the current understanding of the interplay between autophagy and EMT in cancer, with special regard to GBM model. As the invasive behaviour is a hallmark of GBM aggressiveness, defining a new link between autophagy and EMT can open a novel scenario for targeting these processes in future therapeutical approaches.

Berberine promotes osteogenic differentiation of mesenchymal stem cells with therapeutic potential in periodontal regeneration

Periodontal disease is a bacterial infection-associated disease of the periodontal tissues characterized by the destruction of tooth-supporting structures, including alveolar bone. The ideal goal of periodontal therapy is the complete regeneration of alveolar bone in a healthy microenvironment free of infection. In this study, we found that berberine, a benzylisoquinoline plant alkaloid from Coptidis Rhizoma, strongly inhibited the growth of Porphyromonas gingivalis. Gingipain is the most important virulence factor of Porphyromonas gingivalis in the process of periodontal tissue destruction. Berberine also had an inhibitory effect on gingipain activity in a concentration dependent manner. Remarkably, berberine restored the downregulation of osteogenesis-related genes expression in bone mesenchymal stem cells (BMSCs) induced by Porphyromonas gingivalis infection, and significantly increased the expression of osteogenesis-related genes such as OSX, COLI, ALP, OCN and OPN compared to the control group. This results suggested that berberine may directly promote osteogenesis. Further in-vitro studies demonstrated that berberine statistically significantly promoted the osteogenic differentiation of BMSCs at concentrations of 1-10 μM. In the research on the mechanisms, we found that both total β-catenin and nuclear β-catenin accumulation were statistically significantly increased by berberine. And the transcriptional activity of β-catenin/TCF was about 2 folds higher than the control group. Furthermore, Wnt signalling specific inhibitor DKK-1 blocked the above effects of berberine. These demonstrated that Wnt/β-catenin signalling pathway was involved in the osteogenic differentiation induced by berberine. The antibacterial actions in combination with the promotion role in osteogenic differentiation position berberine as a prospective drug for periodontal tissue regeneration.

Catalpol promotes the osteogenic differentiation of bone marrow mesenchymal stem cells via the Wnt/β-catenin pathway

Background

Rehmanniae Radix is a traditional herbal medicine in East Asia that has been widely used to treat patients with osteoporosis. However, the effect of catalpol, the primary active principle component of Rehmanniae Radix, on the function of bone marrow mesenchymal stem cells (BMSCs) and the underlying molecular mechanisms associated with its activity remain poorly understood.

Methods

The effect of catalpol on the proliferation of BMSCs was evaluated using a Cell Counting Kit-8 assay. Alkaline phosphatase (ALP) staining, ALP activity and Alizarin Red staining were performed to elucidate the effect of catalpol on the osteogenesis of BMSCs. qRT-PCR, Western blotting and immunofluorescence were performed to evaluate the expression of osteo-specific markers and the Wnt/β-catenin signalling-related genes and proteins. Moreover, a rat critical-sized calvarial defect model and a rat ovariectomy model were used to assess the effect of catalpol on bone regeneration in vivo.

Results

Catalpol significantly enhanced osteoblast-specific gene expression, alkaline phosphatase activity and calcium deposition in BMSCs in vitro. This phenomenon was accompanied by an upregulation of Wnt/β-catenin signalling. In addition, the enhanced osteogenesis due to catalpol treatment was partially reversed by a Wnt/β-catenin antagonist. Furthermore, catalpol increased the bone healing capacity of BMSCs in a rat critical-sized calvarial defect model and attenuated bone loss in a rat ovariectomy model.

Conclusions

These data suggest that catalpol enhances the osteogenic differentiation of BMSCs, partly via activation of the Wnt/β-catenin pathway. Catalpol may provide a new strategy for bone tissue engineering and can be a potential agent for the treatment of postmenopausal osteoporosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1143-y) contains supplementary material, which is available to authorized users.

A role for Wnt/β-catenin signalling in suppressing Bacillus Calmette-Guerin-induced macrophage autophagy

Mycobacterium tuberculosis (Mtb)-induced autophagy of alveolar macrophages has been confirmed to play a central role in the pathogenesis of tuberculosis. Growing evidence indicates that excessive or uncontrolled autophagic activity, which results in type II programmed cell death, can be regulated by many factors, including Wnt/β-catenin signalling. Wnt/β-catenin signalling has been demonstrated to be involved in multiple diseases through the regulation of autophagy; however, its exact role in regulating autophagy induced by Mtb remains unclear. Accordingly, this study examined the function of the Wnt/β-catenin signalling pathway in regulating Mycobacterium bovis Bacillus Calmette-Guerin (BCG)-induced autophagy in RAW264.7 macrophage cell line. In the present study, we found that BCG induced the autophagy of RAW264.7 cells in a time- and dose-dependent manner along with an accumulation of LC3 (Microtubule-associated protein 1 light chain 3) protein. Intriguingly, Wnt3a, a Wnt/β-catenin signalling ligand, significantly inhibited autophagy, with decreased autophagy rates and autophagic flux. An immunoblot analysis further revealed that Wnt/β-catenin signalling was capable of inhibiting the expression of the LC3 and autophagy-associated gene (Atg) cascade proteins in BCG-infected cells. Mechanistically, Wnt/β-catenin signalling may inhibit autophagy in BCG-infected macrophages by activating mTOR-dependent pathways. Our findings reveal the mechanisms of Wnt/β-catenin signalling regulates cellular autophagy induced by Mtb and provide novel insights into physiological and immune control of tuberculosis by modulating autophagy processes.

Autophagy induction impairs Wnt/β-catenin signalling through β-catenin relocalisation in glioblastoma cells

Autophagy is an evolutionary conserved process mediating lysosomal degradation of cytoplasmic material. Its involvement in cancer progression is highly controversial, due to its dual role in both limiting tumoural transformation and in protecting established tumoral cells from unfavorable conditions. Little is known about the cross-talk between autophagy and intracellular signalling pathways, as well as about autophagy impact on signalling molecules turnover. An aberrantly activated Wnt/β-catenin signalling is responsible for tumour proliferation, invasion, and stemness maintenance. Here we show that autophagy negatively regulates Wnt/β-catenin signalling in glioblastoma multiforme (GBM) cells, through Dishevelled degradation. We also provide the first evidence that autophagy promotes β-catenin relocalisation within the cell, by inducing a decrease of the nuclear protein fraction. In particular, upon autophagy induction, β-catenin appears mainly localized in sub-membrane areas where it associates with N-cadherin to form epithelial-like cell-cell adhesion structures. Our data indicate, for the first time, that autophagy induction results in Wnt signalling attenuation and in β-catenin relocalisation within the GBM cell. These findings further support the idea that autophagy modulation could represent a potential therapeutical strategy to contrast GBM progression.

The human PKP2/plakophilin-2 gene is induced by Wnt/β-catenin in normal and colon cancer-associated fibroblasts

Colorectal cancer results from the malignant transformation of colonic epithelial cells. Stromal fibroblasts are the main component of the tumour microenvironment, and play an important role in the progression of this and other neoplasias. Wnt/β-catenin signalling is essential for colon homeostasis, but aberrant, constitutive activation of this pathway is a hallmark of colorectal cancer. Here we present the first transcriptomic study on the effect of a Wnt factor on human colonic myofibroblasts. Wnt3A regulates the expression of 1,136 genes, of which 662 are upregulated and 474 are downregulated in CCD-18Co cells. A set of genes encoding inhibitors of the Wnt/β-catenin pathway stand out among those induced by Wnt3A, which suggests that there is a feedback inhibitory mechanism. We also show that the PKP2 gene encoding the desmosomal protein Plakophilin-2 is a novel direct transcriptional target of Wnt/β-catenin in normal and colon cancer-associated fibroblasts. PKP2 is induced by β-catenin/TCF through three binding sites in the gene promoter and one additional binding site located in an enhancer 20 kb upstream from the transcription start site. Moreover, Plakophilin-2 antagonizes Wnt/β-catenin transcriptional activity in HEK-293T cells, which suggests that it may act as an intracellular inhibitor of the Wnt/β-catenin pathway. Our results demonstrate that stromal fibroblasts respond to canonical Wnt signalling and that Plakophilin-2 plays a role in the feedback control of this effect suggesting that the response to Wnt factors in the stroma may modulate Wnt activity in the tumour cells.

Wnt, RSPO and Hippo Signalling in the Intestine and Intestinal Stem Cells

In this review, we address aspects of Wnt, R-Spondin (RSPO) and Hippo signalling, in both healthy and transformed intestinal epithelium. In intestinal stem cells (ISCs), the Wnt pathway is essential for intestinal crypt formation and renewal, whereas RSPO-mediated signalling mainly affects ISC numbers. In human colorectal cancer (CRC), aberrant Wnt signalling is the driving mechanism initiating this type of neoplasia. The signalling role of the RSPO-binding transmembrane proteins, the leucine-rich-repeat-containing G-protein-coupled receptors (LGRs), is possibly more pleiotropic and not only limited to the enhancement of Wnt signalling. There is growing evidence for multiple crosstalk between Hippo and Wnt/β-catenin signalling. In the ON state, Hippo signalling results in serine/threonine phosphorylation of Yes-associated protein (YAP1) and tafazzin (TAZ), promoting formation of the β-catenin destruction complex. In contrast, YAP1 or TAZ dephosphorylation (and YAP1 methylation) results in β-catenin destruction complex deactivation and β-catenin nuclear localization. In the Hippo OFF state, YAP1 and TAZ are engaged with the nuclear β-catenin and participate in the β-catenin-dependent transcription program. Interestingly, YAP1/TAZ are dispensable for intestinal homeostasis; however, upon Wnt pathway hyperactivation, the proteins together with TEA domain (TEAD) transcription factors drive the transcriptional program essential for intestinal cell transformation. In addition, in many CRC cells, YAP1 phosphorylation by YES proto-oncogene 1 tyrosine kinase (YES1) leads to the formation of a transcriptional complex that includes YAP1, β-catenin and T-box 5 (TBX5) DNA-binding protein. YAP1/β-catenin/T-box 5-mediated transcription is necessary for CRC cell proliferation and survival. Interestingly, dishevelled (DVL) appears to be an important mediator involved in both Wnt and Hippo (YAP1/TAZ) signalling and some of the DVL functions were assigned to the nuclear DVL pool. Wnt ligands can trigger alternative signalling that directly involves some of the Hippo pathway components such as YAP1, TAZ and TEADs. By upregulating Wnt pathway agonists, the alternative Wnt signalling can inhibit the canonical Wnt pathway activity.

Expression of low-density lipoprotein-related receptors 5 and 6 (LRP5/6) in psoriasis skin

Low-density lipoprotein-related receptors 5 and 6 (LRP5/6) are transmembrane receptors with key functions in canonical Wnt signalling. Wnt ligands are thought to play an important role in innate immunity and psoriasis, and recent studies assigned LRP5/6 anti-inflammatory properties. The objective of this study was to investigate the expression of LRP5 and LRP6 in lesional and non-lesional skin in peripheral blood and in mononuclear cells of patients with chronic plaque type psoriasis compared with control individuals. To investigate the effect of UV-B radiation, LRP5/6 skin gene expression was analysed before and after narrowband UV-B treatment. Our results showed significantly decreased gene expression of LRP5 and LRP6 in lesional skin and in peripheral blood from patients with psoriasis compared with non-lesional skin and healthy control skin. Immunohistochemistry did not reveal differences in protein expression of LRP5/6. Narrowband UV-B treatment induced a significant increase in LRP5 and LRP6 gene expression in lesional skin. Decreased gene expression of LRP5/6 in lesional skin and upregulation after nb UV-B treatment suggest a possible role for LRP5/6 in psoriasis.

A pathway-based association study reveals variants from Wnt signalling genes contributing to asthma susceptibility

BACKGROUND

Genetic susceptibility to asthma is currently linked to a handful of genes which have a limited ability to predict the overall disease risk, suggesting the existence of many other genes involved in disease development. Accumulated evidence from association studies in genes related by biological pathways could reveal novel asthma genes.

OBJECTIVE

To reveal novel asthma susceptibility genes by means of a pathway-based association study.

METHODS

Based on summary data from a previous a genomewide association study (GWAS) of asthma, we first identified significant biological pathways using a gene-set enrichment analysis. We then mapped all tested single nucleotide polymorphisms (SNPs) on the genes contributing to significant pathways and prioritized those with a disproportionate number of nominal significant associations for further studies. For those prioritized genes, association studies were performed for selected SNPs in independent case-control samples (n = 1765) using logistic regression models, and results were meta-analysed with those from the GWAS.

RESULTS

Two biological processes were significantly enriched: the cytokine-cytokine receptor interaction (P = 0.002) and the Wnt signalling (P = 0.012). From the 417 genes interacting in these two pathways, 10 showed an excess of nominal associations, including a known asthma susceptibility locus (encoding SMAD family member 3) and other novel candidate genes. From the latter, association studies of 14 selected SNPs evidenced replication in a locus near the frizzled class receptor 6 (FZD6) gene (P = 9.90 × 10^-4 ), which had a consistent direction of effects with the GWAS findings (meta-analysed odds ratio = 1.49; P = 5.87 × 10^-6 ) and was in high linkage disequilibrium with expression quantitative trait loci in lung tissues.

CONCLUSIONS AND CLINICAL RELEVANCE

This study revealed the importance of two biological pathways in asthma pathogenesis and identified a novel susceptibility locus near Wnt signalling genes.

The many faces of SRPK1

Serine–arginine protein kinase 1 (SRPK1) phosphorylates proteins involved in the regulation of several mRNA‐processing pathways, including alternative splicing. SRPK1 has been recently reported to be overexpressed in multiple cancers, including prostate cancer, breast cancer, lung cancer, and glioma. Several studies have shown that inhibition of SRPK1 has anti‐tumoural effects, and SRPK1 has therefore become a new candidate for targeted therapies. Interestingly, in terms of molecular mechanism, SRPK1 seems to act heterogeneously, and has been reported to affect several processes in different cancers, e.g. angiogenesis in prostate and colon cancer, apoptosis in breast and colon cancer, and migration in breast cancer. A recent report adds to this puzzle, showing that the main effect of SRPK1 overexpression in non‐small‐cell lung carcinoma is to stimulate a stem cell‐like phenotype. This pleiotropy might be related to preferential activation of different downstream signalling pathways by SRPK1 in various cancers. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Linked Article: Gong et al. J Pathol 2016; 240: 184‐196.

Serine-arginine protein kinase 1 promotes a cancer stem cell-like phenotype through activation of Wnt/β-catenin signalling in NSCLC

Cancer stem cells (CSCs) are commonly associated with cancer recurrence and metastasis that occurs in up to 30-55% of non-small-cell lung carcinoma (NSCLC) patients. Herein, we showed that serine-arginine protein kinase 1 (SRPK1) was highly expressed at both the mRNA and the protein levels in human NCSLC. SRPK1 was associated with the clinical features of human NSCLC, including clinical stage (p < 0.001) and T (p = 0.001), N (p = 0.007), and M (p = 0.001) classifications. Ectopic overexpression of SRPK1 promoted the acquisition of a stem cell-like phenotype in human NSCLC cell lines cultured in vitro. Overexpression of SRPK1 increased sphere formation and the proportion of side-population cells that exclude Hoechst dye. Conversely, SRPK1 silencing reduced the number of spheres and the proportion of side-population cells. Mouse studies indicated that SRPK1 promoted NSCLC cell line tumour growth and SRPK1 overexpression reduced the number of tumour cells required to initiate tumourigenesis in vivo. Mechanistically, gene set enrichment analysis showed that Wnt/β-catenin signalling correlated with SRPK1 mRNA levels and this signalling pathway was hyperactivated by ectopic SRPK1 expression in NSCLC cell lines. Immunofluorescence demonstrated that SRPK1 enhanced β-catenin accumulation in the nuclei of NSCLC cell lines, and inhibition of β-catenin signalling abrogated the SRPK1-induced stem cell-like phenotype. Together, our findings suggest that SRPK1 promotes a stem cell-like phenotype in NSCLC via Wnt/β-catenin signalling. Moreover, SRPK1 may represent a novel target for human NSCLC diagnosis and therapy. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Hepatic gateways

The intestinal mucosal barrier contributes to homeostasis by limiting systemic dissemination of microbes and toxins while allowing nutrients to pass through to the systemic circulation. In a recent issue of Science, Spadoni et al. demonstrated a novel mechanism to enable this selectivity: the existence of a gut-vascular barrier (GVB) as indicated by a series of studies on the interaction between murine and human intestine with Salmonella typhimurium species . They showed that (i) enteroglial cells and pericytes in contact with endothelial cells (ECs) form the GVB (ii) Salmonella typhimurium can penetrate it by a mechanism dependent on the pathogenicity island (Spi) 2-encoded type III secretion system and on decreased β-catenin dependent signaling in gut endothelial cells. Understanding the GVB may provide new insights into the regulation of the gut-liver axis.

Inhibition of green tea polyphenol EGCG((-)-epigallocatechin-3-gallate) on the proliferation of gastric cancer cells by suppressing canonical wnt/β-catenin signalling pathway

(-)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, could affect carcinogenesis and development of many cancers. However, the effects and underlying mechanisms of EGCG on gastric cancer remain unclear. We found that EGCG significantly inhibited proliferation and increased apoptosis of SGC-7901 cells in vitro. The decreased expressions of p-β-catenin(Ser552), p-GSK3β(S9) and β-catenin target genes were detected in SGC-7901 cells after treated by EGCG. XAV939 and β-catenin plasmid were further used to demonstrate the inhibition of EGCG on canonical Wnt/β-catenin signalling. Moreover, EGCG significantly inhibited gastric tumour growth in vivo by inhibiting Wnt/β-catenin signalling. Taken together, our findings establish that EGCG suppressed gastric cancer cell proliferation and demonstrate that this inhibitory effect is related to canonical Wnt/β-catenin signalling. This study raises a new insight into gastric cancer prevention and therapy, and provides evidence that green tea could be used as a nutraceutical beverage.

Prostate tumour overexpressed-1 promotes tumourigenicity in human breast cancer via activation of Wnt/β-catenin signalling

Breast cancer is the most common malignancy in females. The presence of cancer stem cells (CSCs) is the main cause of local and distant tumour recurrence and is associated with poor outcome in breast cancer. However, the molecular mechanisms underlying the maintenance of CSCs remain largely unknown. This study demonstrates that prostate tumour overexpressed-1 (PTOV1) enhances the CSC population and augments the tumourigenicity of breast cancer cells both in vitro and in vivo. Moreover, PTOV1 suppresses transcription of Dickkopf-1 (DKK1) by recruiting histone deacetylases and subsequently reducing DKK1 promoter histone acetylation, followed by activation of Wnt/β-catenin signalling. Restoration of DKK1 expression in PTOV1-overexpressing cells counteracts the effects of PTOV1 on Wnt/β-catenin activation and the CSC population. Collectively, these results suggest that PTOV1 positively regulates the Wnt/β-catenin signalling pathway and enhances tumourigenicity in breast cancer; this novel mechanism may represent a therapeutic target for breast cancer. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

5-Hydroxytryptamine promotes hepatocellular carcinoma proliferation by influencing β-catenin

5-Hydroxytryptamine (5-HT), a neurotransmitter and vasoactive factor, has been reported to promote proliferation of serum-deprived hepatocellular carcinoma (HCC) cells but the detailed intracellular mechanism is unknown. As Wnt/β-catenin signalling is highly dysregulated in a majority of HCC, this study explored the regulation of Wnt/β-catenin signalling by 5-HT. The expression of various 5-HT receptors was studied by quantitative real-time polymerase chain reaction (qPCR) in HCC cell lines as well as in 33 pairs of HCC tumours and corresponding adjacent non-tumour tissues. Receptors 5-HT1D (21/33, 63.6%), 5-HT2B (12/33, 36.4%) and 5-HT7 (15/33, 45.4%) were overexpressed whereas receptors 5-HT2A (17/33, 51.5%) and 5-HT5 (30/33, 90.1%) were reduced in HCC tumour tissues. In vitro data suggests 5-HT increased total β-catenin, active β-catenin and decreased phosphorylated β-catenin protein levels in serum deprived HuH-7 and HepG2 cells compared to control cells under serum free medium without 5-HT. Activation of Wnt/β-catenin signalling was evidenced by increased expression of β-catenin downstream target genes, Axin2, cyclin D1, dickoppf-1 (DKK1) and glutamine synthetase (GS) by qPCR in serum-deprived HCC cell lines treated with 5-HT. Additionally, biochemical analysis revealed 5-HT disrupted Axin1/β-catenin interaction, a critical step in β-catenin phosphorylation. Increased Wnt/β-catenin activity was attenuated by antagonist of receptor 5-HT7 (SB-258719) in HCC cell lines and patient-derived primary tumour tissues in the presence of 5-HT. SB-258719 also reduced tumour growth in vivo. This study provides evidence of Wnt/β-catenin signalling activation by 5-HT and may represent a potential therapeutic target for hepatocarcinogenesis.

The molecular and cellular signatures of the mouse eminentia thalami support its role as a signalling centre in the developing forebrain

The mammalian eminentia thalami (EmT) (or thalamic eminence) is an embryonic forebrain structure of unknown function. Here, we examined the molecular and cellular properties of the mouse EmT. We first studied mRNA expression of signalling molecules and found that the EmT is a structure, rich in expression of secreted factors, with Wnts being the most abundantly detected. We then examined whether EmT tissue could induce cell fate changes when grafted ectopically. For this, we transplanted EmT tissue from a tau-GFP mouse to the ventral telencephalon of a wild type host, a telencephalic region where Wnt signalling is not normally active but which we showed in culture experiments is competent to respond to Wnts. We observed that the EmT was able to induce in adjacent ventral telencephalic cells ectopic expression of Lef1, a transcriptional activator and a target gene of the Wnt/β-catenin pathway. These Lef1-positive;GFP-negative cells expressed the telencephalic marker Foxg1 but not Ascl1, which is normally expressed by ventral telencephalic cells. These results suggest that the EmT has the capacity to activate Wnt/β-catenin signalling in the ventral telencephalon and to suppress ventral telencephalic gene expression. Altogether, our data support a role of the EmT as a signalling centre in the developing mouse forebrain.

Oxygen regulates proliferation of neural stem cells through Wnt/β-catenin signalling

Reduced oxygen levels (1-5% O2, named herein 'physioxia') are beneficial for stem cell cultures leading to enhanced proliferation, better survival and higher differentiation potential, but the underlying molecular mechanisms remain elusive. A potential link between physioxia and the canonical Wnt pathway was found recently, but the differential involvement of this signalling pathway for the various stem cell properties such as proliferation, stem cell maintenance, and differentiation capacity remains enigmatic. We here demonstrate increased Wnt target gene transcription and stabilised active β-catenin upon physioxic cell culture in primary tissue-specific foetal mouse neural stem cells. Knock-out of the main oxygen sensing molecule, hypoxia-inducible factor-1α (Hif-1α), had no impact on Wnt activation assuming that physioxia induces the Wnt pathway independently of Hif-1α. To determine the physiological relevance of physioxia-induced Wnt/β-catenin signalling, we examined proliferation, cell cycle kinetics, survival and stem cell maintenance upon Wnt activation and inhibition. Whereas survival and stem cell maintenance seem to be independent of the Wnt pathway, our studies provide first evidence that Wnt/β-catenin signalling positively stimulates proliferation of physioxic cells by affecting cell cycle regulation. Together, our results provide mechanistic insight into oxygen-mediated regulation of the self-renewal activity of neural stem cells.