Anti-apoptotic action of Wnt5a in dermal fibroblasts is mediated by the PKA signaling pathways

WISP1 and Macrophage Migration Inhibitory Factor in Respiratory Inflammation: Novel Insights and Therapeutic Potentials for Asthma and COPD

Recent advancements highlight the intricate interplay between the extracellular matrix (ECM) and immune responses, notably in respiratory diseases such as asthma and Chronic Obstructive Pulmonary Disease (COPD). The ECM, a dynamic structural framework within tissues, orches-trates a plethora of cellular processes, including immune cell behavior and tissue repair mecha-nisms. WNT1-inducible-signaling pathway protein 1 (WISP1), a key ECM regulator, controls immune cell behavior, cytokine production, and tissue repair by modulating integrins, PI3K, Akt, β-catenin, and mTOR signaling pathways. WISP1 also induces macrophage migration inhibitory factor (MIF) expression via Src kinases and epidermal growth factor receptor (EGFR) activation. MIF, through its wide range of activities, enhances inflammation and tissue restructuring. Rec-ognized for its versatile roles in regulating the immune system, MIF interacts with multiple immune components, such as the NLRP3 inflammasome, thereby sustaining inflammatory pro-cesses. The WISP1-MIF axis potentially unveils complex molecular mechanisms governing im-mune responses and inflammation. Understanding the intricate roles of WISP1 and MIF in the pathogenesis of chronic respiratory diseases such as asthma and COPD could lead to the identi-fication of novel targets for therapeutic intervention to alleviate disease severity and enhance patient outcomes.

Unraveling Cancer's Wnt Signaling: Dynamic Control through Protein Kinase Regulation

Since the initial identification of oncogenic Wnt in mice and Drosophila, the Wnt signaling pathway has been subjected to thorough and extensive investigation. Persistent activation of Wnt signaling exerts diverse cancer characteristics, encompassing tumor initiation, tumor growth, cell senescence, cell death, differentiation, and metastasis. Here we review the principal signaling mechanisms and the regulatory influence of pathway-intrinsic and extrinsic kinases on cancer progression. Additionally, we underscore the divergences and intricate interplays of the canonical and non-canonical Wnt signaling pathways and their critical influence in cancer pathophysiology, exhibiting both growth-promoting and growth-suppressing roles across diverse cancer types.

Noncanonical WNT5A controls the activation of latent TGF-β to drive fibroblast activation and tissue fibrosis

Transforming growth factor β (TGF-β) signaling is a core pathway of fibrosis, but the molecular regulation of the activation of latent TGF-β remains incompletely understood. Here, we demonstrate a crucial role of WNT5A/JNK/ROCK signaling that rapidly coordinates the activation of latent TGF-β in fibrotic diseases. WNT5A was identified as a predominant noncanonical WNT ligand in fibrotic diseases such as systemic sclerosis, sclerodermatous chronic graft-versus-host disease, and idiopathic pulmonary fibrosis, stimulating fibroblast-to-myofibroblast transition and tissue fibrosis by activation of latent TGF-β. The activation of latent TGF-β requires rapid JNK- and ROCK-dependent cytoskeletal rearrangements and integrin αV (ITGAV). Conditional ablation of WNT5A or its downstream targets prevented activation of latent TGF-β, rebalanced TGF-β signaling, and ameliorated experimental fibrosis. We thus uncovered what we believe to be a novel mechanism for the aberrant activation of latent TGF-β in fibrotic diseases and provided evidence for targeting WNT5A/JNK/ROCK signaling in fibrotic diseases as a new therapeutic approach.

Role of microRNAs in regulation of WNT signaling pathway in urothelial and prostate cancers

Background

Urothelial cancer (UC) and prostate cancer (PCa) are the most common cancers among men with a high ratio of mortality in advanced-stages. The higher risk of these malignancies among men can be associated with higher carcinogens exposure. Molecular pathology of UC and PCa is related to the specific mutations and aberrations in some signaling pathways. WNT signaling is a highly regulated pathway that has a pivotal role during urothelial and prostate development and homeostasis. This pathway also plays a vital role in adult stem cell niches to maintain a balance between stemness and differentiation. Deregulation of the WNT pathway is frequently correlated with tumor progression and metastasis in urothelial and prostate tumors. Therefore, regulatory factors of WNT pathways are being investigated as diagnostic or prognostic markers and novel therapeutic targets during urothelial and prostate tumorigenesis. MicroRNAs (miRNAs) have a pivotal role in WNT signaling regulation in which there are interactions between miRNAs and WNT signaling pathway during tumor progression. Since, the miRNAs are sensitive, specific, and noninvasive, they can be introduced as efficient biomarkers of tumor progression.

Main body

In present review, we have summarized all of the miRNAs that have been involved in regulation of WNT signaling pathway in urothelial and prostate cancers.

Conclusions

It was observed that miRNAs were mainly involved in regulation of WNT signaling in bladder cancer cells through targeting the WNT ligands and cytoplasmic WNT components such as WNT5A, WNT7A, CTNNB1, GSK3β, and AXIN. Whereas, miRNAs were mainly involved in regulation of WNT signaling in prostate tumor cells via targeting the cytoplasmic WNT components and WNT related transcription factors such as CTNNB1, GSK3β, AXIN, TCF7, and LEF1. MiRNAs mainly functioned as tumor suppressors in bladder and prostate cancers through the WNT signaling inhibition. This review paves the way of introducing a noninvasive diagnostic panel of WNT related miRNAs in urothelial and prostate tumors.

Diverse transcriptional regulation and functional effects revealed by CRISPR/Cas9-directed epigenetic editing

DNA methylation is an epigenetic process that controls DNA accessibility and serves as a transcriptomic switch when deposited at regulatory regions. The adequate functioning of this process is indispensable for tissue homeostasis and cell fate determination. Conversely, altered DNA methylation patterns result in abnormal gene transcription profiles that contribute to tumor initiation and progression. However, whether the consequence of DNA methylation on gene expression and cell fate is uniform regardless of the cell type or state could so far not been tested due to the lack of technologies to target DNA methylation in-situ. Here, we have taken advantage of CRISPR/dCas9 technology adapted for epigenetic editing through site-specific targeting of DNA methylation to characterize the transcriptional changes of the candidate gene and the functional effects on cell fate in different tumor settings. As a proof-of-concept, we were able to induce de-novo site-specific methylation of the gene promoter of IGFBP2 up to 90% with long-term and bona-fide inheritance by daughter cells. Strikingly, this modification led to opposing expression profiles of the target gene in different cancer cell models and affected the expression of mesenchymal genes CDH1, VIM1, TGFB1 and apoptotic marker BCL2. Moreover, methylation-induced changes in expression profiles was also accompanied by a phenotypic switch in cell migration and cell morphology. We conclude that in different cell types the consequence of DNA methylation on gene expression and cell fate can be completely different.

Splicing factor SRSF6 mediates pleural fibrosis

Pleural fibrosis is defined as an excessive deposition of extracellular matrix that results in destruction of the normal pleural tissue architecture and compromised function. Tuberculous pleurisy, asbestos injury, and rheumatoid pleurisy are main causes of pleural fibrosis. Pleural mesothelial cells (PMCs) play a key role in pleural fibrosis. However, detailed mechanisms are poorly understood. Serine/arginine-rich protein SRSF6 belongs to a family of highly conserved RNA-binding splicing-factor proteins. Based on its known functions, SRSF6 should be expected to play a role in fibrotic diseases. However, the role of SRSF6 in pleural fibrosis remains unknown. In this study, SRSF6 protein was found to be increased in cells of tuberculous pleural effusions (TBPE) from patients, and decellularized TBPE, bleomycin, and TGF-β1 were confirmed to increase SRSF6 levels in PMCs. In vitro, SRSF6 mediated PMC proliferation and synthesis of the main fibrotic protein COL1A2. In vivo, SRSF6 inhibition prevented mouse experimental pleural fibrosis. Finally, activated SMAD2/3, increased SOX4, and depressed miRNA-506-3p were associated with SRSF6 upregulation in PMCs. These observations support a model in which SRSF6 induces pleural fibrosis through a cluster pathway, including SRSF6/WNT5A and SRSF6/SMAD1/5/9 signaling. In conclusion, we propose inhibition of the splicing factor SRSF6 as a strategy for treatment of pleural fibrosis.

LINC00173 promotes the apoptosis of hypertrophic scar fibroblasts through increasing β-catenin expression

Previous studies have demonstrated the involvement of long intergenic nonprotein coding RNA 173 (LINC00173) in several pathological disorders. However, the function of LINC00173 in the hypertrophic scar is not well understood. This study confirmed that the two transcript variants of TSV1 and TSV2 were both upregulated in hypertrophic scar fibroblasts. The overexpression of TSV1 or TSV2 promoted the apoptosis of fibroblasts, whereas the overexpression of TSV2 inhibited the proliferation of fibroblasts. RNA-sequencing (RNA-seq), Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis, and gene set enrichment analysis (GSEA) showed that phosphatidylinositol 3-kinase (PI3K)/Akt and Mitogen-activated protein kinases (MAPK) signaling might be involved in the role of LINC00173 in hypertrophic scar pathogenesis. Furthermore, the protein expression of β-catenin was upregulated in the TSV1 or TSV2 overexpression group. Overall, the study demonstrated that LINC00173 promoted the apoptosis of fibroblasts through increasing β-catenin expression, suggesting that LINC00173 might be a new target for hypertrophic scar treatment.

Combination therapy with cilostazol, aripiprazole, and donepezil protects neuronal cells from β-amyloid neurotoxicity through synergistically enhanced SIRT1 expression

Alzheimer's disease (AD) is a multi-faceted neurodegenerative disease. Thus, current therapeutic strategies require multitarget-drug combinations to treat or prevent the disease. At the present time, single drugs have proven to be inadequate in terms of addressing the multifactorial pathology of AD, and multitarget-directed drug design has not been successful. Based on these points of views, it is judged that combinatorial drug therapies that target several pathogenic factors may offer more attractive therapeutic options. Thus, we explored that the combination therapy with lower doses of cilostazol and aripiprazole with add-on donepezil (CAD) might have potential in the pathogenesis of AD. In the present study, we found the superior efficacies of donepezil add-on with combinatorial mixture of cilostazol plus aripiprazole in modulation of expression of AD-relevant genes: Aβ accumulation, GSK-3β, P300, acetylated tau, phosphorylated-tau levels, and activation of α-secretase/ADAM 10 through SIRT1 activation in the N2a Swe cells expressing human APP Swedish mutation (N2a Swe cells). We also assessed that CAD synergistically raised acetylcholine release and choline acetyltransferase (CHAT) expression that were declined by increased β-amyloid level in the activated N2a Swe cells. Consequently, CAD treatment synergistically increased neurite elongation and improved cell viability through activations of PI3K, BDNF, β-catenin and a7-nicotinic cholinergic receptors in neuronal cells in the presence of Aβ_1-42. This work endorses the possibility for efficient treatment of AD by supporting the synergistic therapeutic potential of donepezil add-on therapy in combination with lower doses of cilostazol and aripiprazole.

Multitarget-directed cotreatment with cilostazol and aripiprazole for augmented neuroprotection against oxidative stress-induced toxicity in HT22 mouse hippocampal cells

Cerebrovascular dysfunction is crucially associated with cognitive impairment and a high prevalence of psychotic symptoms in the vascular dementia characterized by oxidative stress and multifactorial neurodegeneration. In this study, the significant decrease in BDNF expression in HT22 cells due to H₂O₂ (0.25 mM) was little affected by either aripiprazole (1 μM) or cilostazol (1 μM) alone, but significantly increased by cotreatment with both drugs. Even in the presence of H₂O₂, P-CK2α (Tyr 255), nuclear P-CREB (Ser 133), and nuclear P-β-catenin (Ser 675) levels were significantly increased in a synergistic manner by aripiprazole plus cilostazol cotreatment. Aripiprazole and cilostazol cotreatment synergistically increased P-GSK-3β (Ser 9) level. Nrf2/HO-1 expression was significantly elevated time- and concentration-dependently by either aripiprazole or cilostazol. In line with these, concurrent treatment with aripiprazole (1 μM) plus cilostazol (1 μM) significantly increased Nrf2 and HO-1 expression in a synergistic manner, accompanying with increased ARE luciferase activity, while each drug monotherapy showed little effects. Consequently, this cotreatment synergistically ameliorated the attenuated neurite outgrowth induced by H₂O₂ in the HT22 cells, and these were inhibited by K252A (inhibitor of BDNF receptor), TBCA (CK2 inhibitor), imatinib (β-catenin inhibitor) and ZnPP (inhibitor of HO-1), indicating that BDNF, P-CK2α, β-catenin and HO-1 activation are implicated in the enhanced neurite outgrowth. This study highlights that cotreatment with low concentrations of aripiprazole and cilostazol synergistically elicits neuroprotective effects by overcoming oxidative stress-evoked neurotoxicity associated with increased neurite outgrowth, providing a rationale for the use of this combinatorial treatment in vascular dementia.

Basal constriction during midbrain-hindbrain boundary morphogenesis is mediated by Wnt5b and focal adhesion kinase

Basal constriction occurs at the zebrafish midbrain–hindbrain boundary constriction (MHBC) and is likely a widespread morphogenetic mechanism. 3D reconstruction demonstrates that MHBC cells are wedge-shaped, and initially constrict basally, with subsequent apical expansion. wnt5b is expressed in the MHB and is required for basal constriction. Consistent with a requirement for this pathway, expression of dominant negative Gsk3β overcomes wnt5b knockdown. Immunostaining identifies focal adhesion kinase (Fak) as active in the MHB region, and knockdown demonstrates Fak is a regulator of basal constriction. Tissue specific knockdown further indicates that Fak functions cell autonomously within the MHBC. Fak acts downstream of wnt5b, suggesting that Wnt5b signals locally as an early step in basal constriction and acts together with more widespread Fak activation. This study delineates signaling pathways that regulate basal constriction during brain morphogenesis.

Summary: Focal adhesion kinase acts downstream of Wnt5b to mediate basal constriction of neuroepithelial cells during the formation of the midbrain–hindbrain boundary.

Neuroprotection by aripiprazole against β-amyloid-induced toxicity by P-CK2α activation via inhibition of GSK-3β

Psychosis is reported over 30% of patients with Alzheimer's disease (AD) in clinics. Aripiprazole is an atypical antipsychotic drug with partial agonist activity at the D₂ dopamine and 5-HT_1A receptors with low side-effect profile. We identified aripiprazole is able to overcome the amyloid-β (Aβ)-evoked neurotoxicity and then increase the cell viability. This study elucidated the mechanism(s) by which aripiprazole ameliorates Aβ1-42-induced decreased neurite outgrowth and viability in neuronal cells. Pretreatment with aripiprazole increased Brain-derived neurotrophic factor (BDNF) mRNA and protein expressions in N2a cells. Additionally, phosphorylated casein kinase 2α at Y 255 (P-CK2α) was increased in time- and concentration-dependent manners. Furthermore, Aβ1-42-induced decreased BDNF and P-CK2α expression were increased over control level by aripiprazole. Subsequently, Aβ1-42-induced decreased levels of phosphorylated glycogen synthase-3β at Ser9 (P-GSK-3β) and nuclear P-β-catenin (Ser675) were elevated by aripiprazole, which were inhibited by K252A (inhibitor of BDNF receptor) and tetrabromocinnamic acid (TBCA, CK2 inhibitor), indicating that BDNF and P-CK2α activation are implicated in the aripiprazole effects. Expressions of cyclin D1 and insulin-like growth factor 2 (IGF2) mRNA were increased by aripiprazole; even in the presence of Aβ1-42, which was blocked by K252A and TBCA. In CK2α gene-silenced N2a cells, aripiprazole failed to increase P-GSK-3β and P-β-catenin expressions. Consequently, aripiprazole ameliorated Aβ1-42-induced attenuation of neurite elongation in HT22 cells, and this effect was blocked by both TBCA and imatinib. Decreased viability induced by Aβ1-42 was recovered by aripiprazole. These findings provide evidence supporting that aripiprazole can provide an effective therapeutic strategy against Aβ-induced neurotoxicity in AD-associated psychosis.

Implication of downregulation and prospective pathway signaling of microRNA-375 in lung squamous cell carcinoma

BACKGROUND

Lung cancer is one of the most typical cancers in the world. Altered expression profiles of microRNA-375(miR-375) are linked to many diseases including lung cancer. However, the relationship between miR-375 and lung squamous cell carcinoma (LUSC) is controversial.

METHODS

We first evaluated the 23 LUSCs and the paired normal lung tissues by qRT-PCR. Then we analyzed the LUSC samples with miR-375 expression based on The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). Furthermore, bioinformatics analysis was performed to explore the biological role of miR-375 in LUSC.

RESULTS

The expression of miR-375 was remarkably reduced in LUSC tissues compared with that in paired lung tissues by qRT-PCR (P=0.003). Additionally, the TCGA dataset suggested that miR-375 was significantly downregulated in 478 LUSC tissues compared with 45 normal lung tissues (P<0.0001), as well as the result derived from GEO datasets (the pooled SMD=-1.01; 95%CIs-1.66 to -0.33, P=0.004). Furthermore, a total of 1348 miR-375-related differently expressed genes were identified by the analytical integration, which were involved in critical pathways of LUSC like neuron differentiation, plasma membrane part and sequence-specific DNA binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway examination also unveiled the involvement of target genes in morphine addiction and drug metabolism- other enzymes and neuroactive ligand-receptor interaction. Finally, the expression of WNT5A was inversely correlated with miR-375 expression according to TCGA dataset (r=-0.2342, P<0.0001).

CONCLUSIONS

miR-375 exerts a strong tumor-suppressive effect in LUSC and provided novel insight into the biological function in tumorigenesis and progression of LUSC.

WNT-5A: signaling and functions in health and disease

WNT-5A plays critical roles in a myriad of processes from embryonic morphogenesis to the maintenance of post-natal homeostasis. WNT-5A knock-out mice fail to survive and present extensive structural malformations. WNT-5A predominantly activates β-catenin-independent WNT signaling cascade but can also activate β-catenin signaling to relay its diverse cellular effects such as cell polarity, migration, proliferation, cell survival, and immunomodulation. Moreover, aberrant WNT-5A signaling is associated with several human pathologies such as cancer, fibrosis, and inflammation. Thus, owing to its diverse functions, WNT-5A is a crucial signaling molecule currently under intense investigation with efforts to not only delineate its signaling mechanisms and functions in physiological and pathological conditions, but also to develop strategies for its therapeutic targeting.

Upregulation of the expression of Wnt5a promotes the proliferation of pancreatic cancer cells in vitro and in a nude mouse model

Wnt proteins are a group of secreted signaling proteins, which function to regulate cell fate and pattern formation during embryogenesis. Altered expression of Wnt5a has been implicated in human carcinogenesis and tumor progression. A previous study identified that Wnt5a is overexpressed in human pancreatic cancer tissues, and that upregulated expression of Wnt5a promotes tumor cell migration and invasion. The present study investigated the role of Wnt5a in pancreatic cancer cell proliferation in vitro and in an orthotopic nude mouse model. Wnt5a cDNA or small interfering RNA were stably transfected into pancreatic cancer cells to assess cell proliferation-associated behaviors, including cell viability, colony formation and apoptosis in vitro, as well as tumor cell growth in an orthotopic nude mouse model. Western blot analysis was used to analyze the expression of Wnt signaling molecules. The data showed that upregulation of the expression of Wnt5a significantly promoted proliferation of the human pancreatic cells, but inhibited tumor cell apoptosis in vitro and promoted tumor growth in an orthotopic nude mouse model. By contrast, knockdown of the expression of Wnt5a inhibited cell growth and promoted apoptosis of the pancreatic cancer cells. The data also revealed that β-catenin mediated the effects of Wnt5a on the regulation of pancreatic cancer cell apoptosis in vitro. These results suggested that Wnt5a is involved in the modulation of pancreatic cancer cell proliferation, and that Wnt5a may be a potential target for pancreatic cancer therapy.

Wnt pathway in Dupuytren disease: connecting profibrotic signals

A role of Wnt signaling in Dupuytren disease, a fibroproliferative disease of the hand and fingers, has not been fully elucidated. We examined a large set of Wnt pathway components and signaling targets and found significant dysregulation of 41 Wnt-related genes in tissue from the Dupuytren nodules compared with patient-matched control tissue. A large proportion of genes coding for Wnt proteins themselves was downregulated. However, both canonical Wnt targets and components of the noncanonical signaling pathway were upregulated. Immunohistochemical analysis revealed that protein expression of Wnt1-inducible secreted protein 1 (WISP1), a known Wnt target, was increased in nodules compared with control tissue, but knockdown of WISP1 using small interfering RNA (siRNA) in the Dupuytren myofibroblasts did not confirm a functional role. The protein expression of noncanonical pathway components Wnt5A and VANGL2 as well as noncanonical coreceptors Ror2 and Ryk was increased in nodules. On the contrary, the strongest downregulated genes in this study were 4 antagonists of Wnt signaling (DKK1, FRZB, SFRP1, and WIF1). Downregulation of these genes in the Dupuytren tissue was mimicked in vitro by treating normal fibroblasts with transforming growth factor β1 (TGF-β1), suggesting cross talk between different profibrotic pathways. Furthermore, siRNA-mediated knockdown of these antagonists in normal fibroblasts led to increased nuclear translocation of Wnt target β-catenin in response to TGF-β1 treatment. In conclusion, we have shown extensive dysregulation of Wnt signaling in affected tissue from Dupuytren disease patients. Components of both the canonical and the noncanonical pathways are upregulated, whereas endogenous antagonists are downregulated, possibly via interaction with other profibrotic pathways.

Wnt5A regulates ABCB1 expression in multidrug-resistant cancer cells through activation of the non-canonical PKA/β-catenin pathway

Multidrug resistance in cancer cells arises from altered drug permeability of the cell. We previously reported activation of the Wnt pathway in ABCB1-overexpressed human uterus sarcoma drug-resistant MES-SA/Dx5 cells through active β-catenin and associated transactivation activities, and upregulation of Wnt-targeting genes. In this study, Wnt5A was found to be significantly upregulated in MES-SA/Dx5 and MCF7/ADR2 cells, suggesting an important role for the Wnt5A signaling pathway in cancer drug resistance. Higher cAMP response elements and Tcf/Lef transcription activities were shown in the drug-resistant cancer cells. However, expression of Wnt target genes and CRE activities was downregulated in Wnt5A shRNA stably-transfected MES-SA/Dx5 cells. Cell viability of the drug-resistant cancer cells was also reduced by doxorubicin treatment and Wnt5A shRNA transfection, or by Wnt5A depletion. The in vitro data were supported by immunohistochemical analysis of 24 paired breast cancer biopsies obtained pre- and post-chemotherapeutic treatment. Wnt5A, VEGF and/or ABCB1 were significantly overexpressed after treatment, consistent with clinical chemoresistance. Taken together, the Wnt5A signaling pathway was shown to contribute to regulating the drug-resistance protein ABCB1 and β-catenin-related genes in antagonizing the toxic effects of doxorubicin in the MDR cell lines and in clinical breast cancer samples.

Protein kinase A activation enhances β-catenin transcriptional activity through nuclear localization to PML bodies

The Protein Kinase A (PKA) and Wnt signaling cascades are fundamental pathways involved in cellular development and maintenance. In the osteoblast lineage, these pathways have been demonstrated functionally to be essential for the production of mineralized bone. Evidence for PKA-Wnt crosstalk has been reported both during tumorigenesis and during organogenesis, and the nature of the interaction is thought to rely on tissue and cell context. In this manuscript, we analyzed bone tumors arising from mice with activated PKA caused by mutation of the PKA regulatory subunit Prkar1a. In primary cells from these tumors, we observed relocalization of β-catenin to intranuclear punctuate structures, which were identified as PML bodies. Cellular redistribution of β-catenin could be recapitulated by pharmacologic activation of PKA. Using 3T3-E1 pre-osteoblasts as a model system, we found that PKA phosphorylation sites on β-catenin were required for nuclear re-localization. Further, β-catenin's transport to the nucleus was accompanied by an increase in canonical Wnt-dependent transcription, which also required the PKA sites. PKA-Wnt crosstalk in the cells was bi-directional, including enhanced interactions between β-catenin and the cAMP-responsive element binding protein (CREB) and transcriptional crosstalk between the Wnt and PKA signaling pathways. Increases in canonical Wnt/β-catenin signaling were associated with a decrease in the activity of the non-canonical Wnt/Ror2 pathway, which has been shown to antagonize canonical Wnt signaling. Taken together, this study provides a new understanding of the complex regulation of the subcellular distribution of β-catenin and its differential protein-protein interaction that can be modulated by PKA signaling.

cAMP signalling in the normal and tumorigenic pituitary gland

cAMP signalling plays a key role in the normal physiology of the pituitary gland, regulating cellular growth and proliferation, hormone production and release. Deregulation of the cAMP signalling pathway has been reported to be a common occurrence in pituitary tumorigenesis. Several mechanisms have been implicated including somatic mutations, gene-gene interactions and gene-environmental interactions. Somatic mutations in G-proteins and protein kinases directly alter cAMP signalling, while malfunctioning of other signalling pathways such as the Raf/MAPK/ERK, PI3K/Akt/mTOR and Wnt pathways which normally interact with the cAMP pathway may mediate indirect effects on cAMP and varying downstream effectors. The aryl hydrocarbon receptor signalling pathway has been implicated in pituitary tumorigenesis and we review its role in general and specifically in relation to cAMP de-regulation.

Recombinant human lactoferrin as a biomaterial for bone tissue engineering: mechanism of antiapoptotic and osteogenic activity

Lactoferrin is a bioactive globular protein with unique properties towards musculo-skeletal cells and anabolic to bone in vivo. Even though the potent anti-apoptotic and osteogenic activity of lactoferrin has been reported, the mechanism of action has not been fully elucidated. The study demonstrates that the anti-apoptotic effect of rhLF towards MC3T3 pre-osteoblast cells is mediated by Wnt5a/PKA pathway and the stabilization of β-catenin by rhLF is dependent on PKA/LRP6 signaling pathway. The study also investigates the feasibility of developing rhLF as a biomaterial for cell delivery. The injectable rhLF cell delivery vehicles are prepared by enzymatic crosslinking of tyramine-modified rhLF in the presence of hydrogen peroxide and horseradish peroxidase. The modified rhLF shows bioactivity similar to unmodified rhLF. The rhLF gels support encapsulated MC3T3 cell viability, proliferation, and differentiation, as well as phosphorylation of signaling proteins. In conclusion, the study demonstrates the involvement of Wnt5a, LRP6, and PKA signaling in rhLF-mediated bioactivity towards MC3T3 cells and the feasibility of developing an injectable cell delivery vehicle from rhLF.

Oncogenic effects of WNT5A in Epstein-Barr virus‑associated nasopharyngeal carcinoma

The molecular events that drive the progression of Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) are still to be elucidated. Here, we report for the first time the pathogenic significance of an NPC-associated gene, wingless-type MMTV integration site family, member 5A (WNT5A) and the contribution of EBV to its expression. WNT5A is a representative Wnt protein that activates non-canonical Wnt signalling. With regard to its role in carcinogenesis, there is conflicting evidence as to whether WNT5A has a tumour-promoting or tumour-suppressive role. We show that WNT5A is upregulated in primary NPC tissue samples. We also demonstrate that WNT5A expression was dramatically increased in NPC cell lines expressing the EBV-encoded LMP2A gene, suggesting that this EBV-encoded latent gene is responsible for upregulating WNT5A in NPC. In addition, in vitro WNT5A overexpression promotes the proliferation, migration and invasion of NPC cells. Our results not only reveal pro-tumorigenic effects of WNT5A in NPC but also suggest that WNT5A could be an important therapeutic target in patients with EBV-associated disease.

GSK3β inhibition and LEF1 upregulation in skeletal muscle following a bout of downhill running

Canonical Wnt signaling is important in skeletal muscle repair but has not been well characterized in response to physiological stimuli. The objective of this study was to assess the effect of downhill running (DHR) on components of Wnt signaling. Young, male C57BL/J6 mice were exposed to DHR. Muscle injury and repair (MCadherin) were measured in soleus. Gene and protein expression of Wnt3a, active β-catenin, GSK3β, and LEF1 were measured in gastrocnemius. Muscle injury increased 6 days post-DHR and MCadherin protein increased 5 days post-DHR. Total and active GSK3β protein decreased 3 days (9-fold and 3.6-fold, respectively) post-DHR. LEF1 protein increased 6 days (5-fold) post-DHR. DHR decreased GSK3β and increased LEF1 protein expression, but did not affect other components of Wnt signaling. Due to their applicability, using models of physiological stimuli such as DHR will provide significant insight into cellular mechanisms within muscle.

Cooperation of Epac1/Rap1/Akt and PKA in prostaglandin E(2) -induced proliferation of human umbilical cord blood derived mesenchymal stem cells: involvement of c-Myc and VEGF expression

Prostaglandin E(2) (PGE(2)) is well known to regulate cell functions through cAMP; however, the role of exchange protein directly activated by cAMP (Epac1) and protein kinase A (PKA) in modulating such functions is unknown in human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs). Therefore, we investigated the relationship between Epac1 and PKA during PGE(2)-induced hUCB-MSC proliferation and its related signaling pathways. PGE(2) increased cell proliferation, and E-type prostaglandin (EP) 2 receptor mRNA expression level and activated cAMP generation, which were blocked by EP2 receptor selective antagonist AH 6809. PGE(2) increased Epac1 expression, Ras-related protein 1 (Rap1) activation level, and Akt phosphorylation, which were inhibited by AH 6809, adenylyl cyclase inhibitor SQ 22536, and Epac1/Rap1-specific siRNA. Also, PGE(2) increased PKA activity, which was inhibited by AH 6809, SQ 22536, and PKA inhibitor PKI. HUCB-MSCs were incubated with the Epac agonist 8-pCPT-cAMP or the PKA agonist 6-phe-cAMP to examine whether Epac1/Rap1/Akt activation was independent of PKA activation. 8-pCPT-cAMP increased Akt phosphorylation but not PKA activity. 6-Phe-cAMP increased PKA activity, but not Akt phosphorylation. Additionally, an Akt inhibitor or PKA inhibitor (PKI) did not block the PGE(2) -induced increase in PKA activity or Akt phosphorylation, respectively. Moreover, PGE(2) increased glycogen synthase kinase (GSK)-3β phosphorylation and nuclear translocation of active-β-catenin, which were inhibited by Akt inhibitor or/and PKI. PGE(2) increased c-Myc and vascular endothelial growth factor (VEGF) expression levels, which were blocked by β-catenin siRNA. In conclusion, PGE(2) stimulated hUCB-MSC proliferation through β-catenin-mediated c-Myc and VEGF expression via Epac/Rap1/Akt and PKA cooperation.

Proteomic analysis of extracellular matrix from the hepatic stellate cell line LX-2 identifies CYR61 and Wnt-5a as novel constituents of fibrotic liver

Activation of hepatic stellate cells (HSCs) and subsequent uncontrolled accumulation of altered extracellular matrix (ECM) underpin liver fibrosis, a wound healing response to chronic injury, which can lead to organ failure and death. We sought to catalogue the components of fibrotic liver ECM to obtain insights into disease etiology and aid identification of new biomarkers. Cell-derived ECM was isolated from the HSC line LX-2, an in vitro model of liver fibrosis, and compared to ECM from human foreskin fibroblasts (HFFs) as a control. Mass spectrometry analyses of cell-derived ECMs identified, with ≥99% confidence, 61 structural ECM or secreted proteins (48 and 31 proteins for LX-2 and HFF, respectively). Gene ontology enrichment analysis confirmed the enrichment of ECM proteins, and hierarchical clustering coupled with protein–protein interaction network analysis revealed a subset of proteins enriched to fibrotic ECM, highlighting the existence of cell type-specific ECM niches. Thirty-six proteins were enriched to LX-2 ECM as compared to HFF ECM, of which Wnt-5a and CYR61 were validated by immunohistochemistry in human and murine fibrotic liver tissue. Future studies will determine if these and other components may play a role in the etiology of hepatic fibrosis, serve as novel disease biomarkers, or open up new avenues for drug discovery.

Wnt/Ca2+ signaling pathway: a brief overview

The non-canonical Wnt/Ca(2+) signaling cascade is less characterized than their canonical counterpart, the Wnt/β-catenin pathway. The non-canonical Wnt signaling pathways are diverse, defined as planer cell polarity pathway, Wnt-RAP1 signaling pathway, Wnt-Ror2 signaling pathway, Wnt-PKA pathway, Wnt-GSK3MT pathway, Wnt-aPKC pathway, Wnt-RYK pathway, Wnt-mTOR pathway, and Wnt/calcium signaling pathway. All these pathways exhibit a considerable degree of overlap between them. The Wnt/Ca(2+) signaling pathway was deciphered as a crucial mediator in development. However, now there is substantial evidence that the signaling cascade is involved in many other molecular phenomena. Many aspects of Wnt/Ca(2+) pathway are yet enigmatic. This review will give a brief overview of the fundamental and evolving concepts of the Wnt/Ca(2+) signaling pathway.

Keloid fibroblasts are more sensitive to Wnt3a treatment in terms of elevated cellular growth and fibronectin expression

BACKGROUND

Current evidence suggests the potential role of Wnt signalling in keloids pathogenesis but such literature remains scanty. We hypothesize that Wnt signalling is upregulated in keloid fibroblasts (KFs) and this promotes cellular growth, migration and extracellular matrix (ECM) production in such fibroblasts.

OBJECTIVES

To verify the downregulation of secreted frizzled-related protein 1 (SFRP1), a Wnt inhibitor and test KFs sensitivity to Wnt3a treatment compared to NFs in terms of activation of Wnt/β-catenin, cellular growth, migration and ECM expressions. Next, to investigate if ectopic expression of SFRP1 and treatment of quercetin in KFs can reverse their phenotypes.

METHODS

Quantitative Real-time PCR and western blotting were used to verify SFRP1 expression in NFs and KFs. The fibroblasts were tested with Wnt3a conditioned media and its effects were tested for (1) the cells' sensitivity to direct Wnt signalling via the activation of TCF reporter assay and protein expression of β-catenin, (2) cellular growth, (3) cell migration and (4) expressions of ECM components. Finally KFs were stably transduced with SFRP1 and treated with 2 doses of quercetin.

RESULTS

Lower levels of SFRP1 were confirmed at mRNA and protein levels in KFs which partly explained their sensitivity to Wnt3a treatment in terms of higher Wnt activation, cellular growth and fibronectin expression. Interestingly, Wnt3a did not promote higher cell migration rate and increase in collagen I expression. Ectopic expression of SFRP1 and quercetin treatment was able to mitigate Wnt3a-mediated phenotype of KFs.

CONCLUSIONS

Using SFRP1 or inhibitors of Wnt signalling might be one of the therapeutic solutions to treat keloid scarring.

International Union of Basic and Clinical Pharmacology. LXXX. The class Frizzled receptors

The receptor class Frizzled, which has recently been categorized as a separate group of G protein-coupled receptors by the International Union of Basic and Clinical Pharmacology, consists of 10 Frizzleds (FZD(1-10)) and Smoothened (SMO). The FZDs are activated by secreted lipoglycoproteins of the Wingless/Int-1 (WNT) family, whereas SMO is indirectly activated by the Hedgehog (HH) family of proteins acting on the transmembrane protein Patched (PTCH). Recent years have seen major advances in our knowledge about these seven-transmembrane-spanning proteins, including: receptor function, molecular mechanisms of signal transduction, and the receptor's role in embryonic patterning, physiology, cancer, and other diseases. Despite intense efforts, many question marks and challenges remain in mapping receptor-ligand interaction, signaling routes, mechanisms of specificity and how these molecular details underlie disease and also the receptor's important role in physiology. This review therefore focuses on the molecular aspects of WNT/FZD and HH/SMO signaling discussing receptor structure, mechanisms of signal transduction, accessory proteins, receptor dynamics, and the possibility of targeting these signaling pathways pharmacologically.

Gene expression profiling of the androgen independent prostate cancer cells demonstrates complex mechanisms mediating resistance to docetaxel

The molecular mechanisms conferring resistance to docetaxel in prostate cancer patients remain partially understood. We generated docetaxel resistant derivatives of the androgen independent prostate cancer cell lines PC-3 and DU-145. Docetaxel rapidly induces DU-145 cell death via apoptosis and the drug resistant cells were produced by periodically exposing proliferating DU-145 cultures to small doses of docetaxel. In PC-3 cells docetaxel induces delayed cell death via mitotic catastrophe evident by profound multinucleation and formation of giant cells. Mononucleated progeny of the giant PC-3 cells shows significant resistance to docetaxel. Gene expression profiling of these docetaxel resistant PC-3 cells revealed sets of docetaxel inducible and constitutively expressed genes associated with major cancer pathways. A contradictory overlap with DU-145 docetaxel resistant cells was also found. Analyses suggested significant changes associated with apoptotic function, DNA repair, cell growth, survival and proliferation, metabolism, maintenance of cytoskeleton and extracellular matrix formation. These cellular processes often contribute to drug resistance and our study identified a set of genes managing this phenotype. Additional analyses of the drug resistant PC-3 cells using shRNA constructs determined direct relevance of Cyclin G2 to docetaxel resistance as well as prevention of multinucleation, whereas the knockdown of upregulated CYP1B1 showed no effect on either of these processes. Downregulated GBP1 was explored by ectopic overexpression and even though GBP1 has a potential to mediate resistance to docetaxel, it was not utilized in PC-3 cells. The results suggest complex combination of gene expression pattern changes that enables resistance to docetaxel while preventing death via multinucleation.

Mesenchymal stem cells negatively regulate dendritic lineage commitment of umbilical-cord-blood-derived hematopoietic stem cells: an unappreciated mechanism as immunomodulators

Due to their immunomodulatory functions, mesenchymal stem cells (MSCs) have great potential for clinical applications to prevent rejection in organ transplantation and to prevent graft-versus-host disease in hematopoietic stem cell (HSC) transplantation. Since dendritic cells (DCs) play an important role in modulating diverse T cell responses, including rejection and graft-versus-host disease, the goal of this study was to investigate whether MSCs modulate DC differentiation from HSCs and if this effect could be one of the mechanisms for MSCs' immune-modulating functions. Our results demonstrate that differentiation of HSCs into mature DCs is inhibited in the presence of MSCs. Similar frequency of dendritic precursors in the cultures, either with or without MSCs, suggests that the inhibition of MSCs on the differentiation of mature DCs from HSCs could be due to the arresting of maturation at the dendritic precursor step. Reduced levels of cyclic AMP, adenosine 3',5'-cyclic monophosphate (cAMP) and beta-catenin in DC-like cells from the cocultures are detected, suggesting that induction of apoptosis and inhibition of differentiation could be the basis for the inhibition of mature DCs from HSCs by MSCs. Further, our results demonstrate that DCs derived from HSCs in the presence of MSCs are functionally impaired, especially for those after direct contact with MSCs. To investigate the basis of functional impairment, our data show downregulated tumor necrosis factor-alpha and transforming growth factor-beta1 secretion and upregulated interleukin-6 (IL6) and IL1beta secretion in the cultures with MSCs. Together, MSCs can inhibit differentiation of mature DCs from HSCs by arresting them at the precursor stage and induce their apoptosis. Further, HSC-derived DCs in the presence of MSCs are functionally impaired, which could be partly due to the upregulation of IL6 secretion.

The role of R-spondin2 in keratinocyte proliferation and epidermal thickening in keloid scarring

Keloids are found only in humans and the underlying biochemical mechanisms of their pathogenesis remain unknown. R-spondins (Rspos) are a relatively new group of secreted proteins known to be Wnt/β-catenin signaling agonists, but their role in keloids has yet to be elucidated. We investigated the expression levels of R-spondin2 (Rspo2) in cell lysates and conditioned media of monocultures and co-cultures of fibroblasts and keratinocytes derived from keloids and normal skin. In this study we found increased protein expression and secretion of Rspo2 in respective monocultures of keloid fibroblasts and keratinocytes when compared with their normal counterparts. Double-chamber co-culture experiments implicated the role of keloid keratinocytes (KKs) in the induction of Rspo2 secretion from fibroblasts because of epithelial-mesenchymal interactions. Addition of recombinant human Rspo2 in culture increased the proliferation of keratinocytes and it acted synergistically with Wnt3a through the canonical Wnt/β-catenin pathway. Overexpression of Rspo2 in normal fibroblasts brought about thicker epidermis when compared with control fibroblasts in a skin organotypic culture model. This observation coincides with the hyperproliferative phenotype of thickened epidermis seen in keloids. Taken together, the results suggest the possible double paracrine action of KKs in inducing higher expression of Rspo2 in fibroblasts that promotes keratinocyte proliferation and epidermal thickening.

R-spondin-1 is a novel beta-cell growth factor and insulin secretagogue

R-spondin-1 (Rspo1) is an intestinal growth factor known to exert its effects through activation of the canonical Wnt (cWnt) signaling pathway and subsequent expression of cWnt target genes. We have detected Rspo1 mRNA in murine islets and the murine MIN6 and betaTC beta-cell lines, and Rspo1 protein in MIN6 beta-cells. Rspo1 activated cWnt signaling in MIN6 beta-cells by increasing nuclear beta-catenin and c-myc, a cWnt target gene. Rspo1 also induced insulin mRNA expression in MIN6 cells. Analysis of MIN6 and mouse beta-cell proliferation by [(3)H]thymidine and BrdU incorporation, respectively, revealed that Rspo1 stimulated cell growth. Incubation of MIN6 and mouse beta-cells with cytokines (IL1beta/TNFalpha/interferon-gamma) significantly increased cellular apoptosis; this increase was abolished by pretreatment with Rspo1. Rspo1 also stimulated insulin secretion in a glucose-independent fashion. We further demonstrated that the glucagon-like peptide-1 receptor agonist, exendin4 (EX4), stimulated Rspo1 mRNA transcript levels in MIN6 cells in a glucose-, time-, dose-, and PI3-kinase-dependent fashion. This effect was not limited to this beta-cell line, as similar time-dependent increases in Rspo1 were also observed in the betaTC beta-cell line and mouse islets in response to EX4 treatment. Together, these studies demonstrate that Rspo1 is a novel beta-cell growth factor and insulin secretagogue that is regulated by EX4. These findings suggest that Rspo1 and the cWnt signaling pathway may serve as a novel target to enhance beta-cell growth and function in patients with type 2 diabetes.

Cyclic AMP suppresses matrix metalloproteinase-1 expression through inhibition of MAPK and GSK-3beta

Expression of matrix metalloproteinase-1 (MMP-1) is stimulated by diverse stimuli and is likely to be regulated by many signaling pathways. cAMP is known to act as a second messenger for various extracellular stimuli and to be involved in the regulation of cell proliferation, apoptosis, and inflammation. Here, we investigated the effect of cAMP on tumor necrosis factor (TNF)-alpha-induced MMP-1 expression and the molecular events involved in the processes in human skin fibroblasts. We showed that cAMP suppresses TNF-alpha-induced MMP-1 expression via protein kinase A (PKA) pathway. cAMP inhibited TNF-alpha-stimulated ERK and JNK activation, which was shown to have an important role in MMP-1 expression. However, MMP-1 expression could also be inhibited by cAMP even when ERK and JNK activities were unaffected, indicating that there might be other target(s) that mediate cAMP-mediated suppression of MMP-1 expression. Further studies revealed that glycogen synthase kinase (GSK)-3beta can be inactivated by cAMP/PKA pathway and has important roles in MMP-1 expression, and showed that inactivation of GSK-3beta is critical for suppression of MMP-1 expression by cAMP elevation after TNF-alpha treatment. Taken together, our results suggest that cAMP/PKA pathway can suppress MMP-1 expression through inhibition of multiple signaling pathways, including MAPK and GSK-3beta.

Mechanisms of protein kinase A anchoring

The second messenger cyclic adenosine monophosphate (cAMP), which is produced by adenylyl cyclases following stimulation of G-protein-coupled receptors, exerts its effect mainly through the cAMP-dependent serine/threonine protein kinase A (PKA). Due to the ubiquitous nature of the cAMP/PKA system, PKA signaling pathways underlie strict spatial and temporal control to achieve specificity. A-kinase anchoring proteins (AKAPs) bind to the regulatory subunit dimer of the tetrameric PKA holoenzyme and thereby target PKA to defined cellular compartments in the vicinity of its substrates. AKAPs promote the termination of cAMP signals by recruiting phosphodiesterases and protein phosphatases, and the integration of signaling pathways by binding additional signaling proteins. AKAPs are a heterogeneous family of proteins that only display similarity within their PKA-binding domains, amphipathic helixes docking into a hydrophobic groove formed by the PKA regulatory subunit dimer. This review summarizes the current state of information on compartmentalized cAMP/PKA signaling with a major focus on structural aspects, evolution, diversity, and (patho)physiological functions of AKAPs and intends to outline newly emerging directions of the field, such as the elucidation of AKAP mutations and alterations of AKAP expression in human diseases, and the validation of AKAP-dependent protein-protein interactions as new drug targets. In addition, alternative PKA anchoring mechanisms employed by noncanonical AKAPs and PKA catalytic subunit-interacting proteins are illustrated.

Glycogen synthase kinase 3beta interaction protein functions as an A-kinase anchoring protein

A-kinase anchoring proteins (AKAPs) include a family of scaffolding proteins that target protein kinase A (PKA) and other signaling proteins to cellular compartments and thereby confine the activities of the associated proteins to distinct regions within cells. AKAPs bind PKA directly. The interaction is mediated by the dimerization and docking domain of regulatory subunits of PKA and the PKA-binding domain of AKAPs. Analysis of the interactions between the dimerization and docking domain and various PKA-binding domains yielded a generalized motif allowing the identification of AKAPs. Our bioinformatics and peptide array screening approaches based on this signature motif identified GSKIP (glycogen synthase kinase 3beta interaction protein) as an AKAP. GSKIP directly interacts with PKA and GSK3beta (glycogen synthase kinase 3beta). It is widely expressed and facilitates phosphorylation and thus inactivation of GSK3beta by PKA. GSKIP contains the evolutionarily conserved domain of unknown function 727. We show here that this domain of GSKIP and its vertebrate orthologues binds both PKA and GSK3beta and thereby provides a mechanism for the integration of PKA and GSK3beta signaling pathways.

Wif-1 is expressed at cartilage-mesenchyme interfaces and impedes Wnt3a-mediated inhibition of chondrogenesis

Wnt factors are involved in the regulation of all steps of cartilage development. The activity of Wnt factors is generally regulated at the extracellular level by factors like the Dkk family, sFRPs, Cerberus and Wnt inhibitory factor 1 (Wif-1). Here we report that Wif-1 is highly expressed at cartilage-mesenchyme interfaces of the early developing skeleton. In fetal and postnatal skeletal development, Wif-1 is expressed in a sharply restricted zone in the upper hyaline layer of epiphyseal and articular cartilage and in trabecular bone. Coimmunoprecipitation and pull-down assays using recombinant Wif-1 and Wnt factors show specific binding of Wif-1 to Wnt3a, Wnt4, Wnt5a, Wnt7a, Wnt9a and Wnt11. Moreover, Wif-1 was able to block Wnt3a-mediated activation of the canonical Wnt signalling pathway. Consequently, Wif-1 impaired growth of mesenchymal precursor cells and neutralised Wnt3a-mediated inhibition of chondrogenesis in micromass cultures of embryonic chick limb-bud cells. These results identify Wif-1 as a novel extracellular Wnt modulator in cartilage biology.

Wnt-5a-induced phosphorylation of DARPP-32 inhibits breast cancer cell migration in a CREB-dependent manner

Tumor cell migration plays a central role in the process of cancer metastasis. We recently identified dopamine and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) as an antimigratory phosphoprotein in breast cancer cells. Here we link this effect of DARPP-32 to Wnt-5a signaling by demonstrating that recombinant Wnt-5a triggers cAMP elevation at the plasma membrane and Thr34-DARPP-32 phosphorylation in MCF-7 cells. In agreement, both protein kinase A (PKA) inhibitors and siRNA-mediated knockdown of Frizzled-3 receptor or Galpha(s) expression abolished Wnt-5a-induced phosphorylation of DARPP-32. Furthermore, Wnt-5a induced DARPP-32-dependent inhibition of MCF-7 cell migration. Phospho-Thr-34-DARPP-32 interacted with protein phosphatase-1 (PP1) and potentiated the Wnt-5a-mediated phosphorylation of CREB, a well-known PP1 substrate, but had no effect on CREB phosphorylation by itself. Moreover, inhibition of the Wnt-5a/DARPP-32/CREB pathway, by expression of dominant negative CREB (DN-CREB), diminished the antimigratory effect of Wnt-5a-induced phospho-Thr-34-DARPP-32. Phalloidin-staining revealed that that the presence of phospho-Thr-34-DARPP-32 in MCF-7 cells results in reduced filopodia formation. In accordance, the activity of the Rho GTPase Cdc42, known to be crucial for filopodia formation, was reduced in MCF-7 cells expressing phospho-Thr-34-DARPP-32. The effects of DARPP-32 on cell migration and filopodia formation could be reversed in T47D breast cancer cells that were depleted of their endogenous DARPP-32 by siRNA targeting. Consequently, Wnt-5a activates a Frizzled-3/Galpha(s)/cAMP/PKA signaling pathway that triggers a DARPP-32- and CREB-dependent antimigratory response in breast cancer cells, representing a novel mechanism whereby Wnt-5a can inhibit breast cancer cell migration.

The opposing roles of Wnt-5a in cancer

Wnt-5a is one of the most highly investigated non-canonical Wnts and has been implicated in almost all aspects of non-canonical Wnt signalling. In terms of cancer development, Wnt-5a has, until recently, lived in the shadow of its better-characterised relatives. This was largely because of its apparent inability to transform cells or signal through the canonical beta-catenin pathway that is so important in cancer, particularly colorectal cancer. Recent work in a wide range of human tumours has pointed to a critical role for Wnt-5a in malignant progression, but there is conflicting evidence whether Wnt-5a has a tumour-promoting or -suppressing role. Emerging evidence suggests that the functions of Wnt-5a can be drastically altered depending on the availability of key receptors. Hence, the presence or absence of these receptors may go some way to explain the conflicting role of Wnt-5a in different cancers. This review summarises our current understanding of Wnt-5a and cancer.

WNT5A is a regulator of fibroblast proliferation and resistance to apoptosis

Usual interstitial pneumonia (UIP) is a specific histopathologic pattern of interstitial lung fibrosis that may be idiopathic or secondary to autoimmune diseases and environmental exposures. In this study, we compared gene expression patterns in primary fibroblasts isolated from lung tissues with UIP histology and fibroblasts isolated from lung tissues with normal histology using expression microarrays. We found that WNT5A was significantly increased in fibroblasts obtained from UIP lung tissues compared with normal lung fibroblasts, an observation verified by quantitative real-time RT-PCR and Western blot. Because the role of WNT5A in UIP is unknown, we treated normal lung fibroblasts or UIP lung fibroblasts with WNT5A, and found that WNT5A increased proliferation as well as relative resistance to H2O2-induced apoptosis. This effect was not mediated through the canonical WNT/beta-catenin pathway, as WNT5A induced a decrease in beta-catenin levels in the same cells. In addition, WNT5A induced increases in fibronectin and alpha(5)-integrin in normal lung fibroblasts. Collectively, our data suggest that WNT5A may play a role in fibroblast expansion and survival characteristics of idiopathic pulmonary fibrosis and other fibrotic interstitial lung diseases that exhibit UIP histological patterns.

Transcriptional outcome of Wnt-Frizzled signal transduction in inflammation: evolving concepts

Wnt-Frizzled signaling was first identified as a key event in Drosophila development. Over the years, ample evidence has accumulated regarding the multiple roles of Wnt-Frizzled signaling in mammalian cell differentiation and tissue/organ morphogenesis. It is thus not surprising that variations in the regulatory network of the Wnt signaling scheme would lead to alterations in cellular organization and cell activation and to the development of pathogenic conditions. Several reports have accordingly implied the involvement of Wnt-Frizzled signaling in the activation of proinflammatory mediators in inflammatory disorders. We will discuss how Wnt-Frizzled signaling may initiate/augment inflammation, focusing on its transcriptional outcome.