c-Abl-mediated phosphorylation of WAVE3 is required for lamellipodia formation and cell migration

Hem1 inborn errors of immunity: waving goodbye to coordinated immunity in mice and humans

Inborn errors of immunity (IEI) are a group of diseases in humans that typically present as increased susceptibility to infections, autoimmunity, hyperinflammation, allergy, and in some cases malignancy. Among newly identified genes linked to IEIs include 3 independent reports of 9 individuals from 7 independent kindreds with severe primary immunodeficiency disease (PID) and autoimmunity due to loss-of-function mutations in the NCKAP1L gene encoding Hematopoietic protein 1 (HEM1). HEM1 is a hematopoietic cell specific component of the WASp family verprolin homologous (WAVE) regulatory complex (WRC), which acts downstream of multiple immune receptors to stimulate actin nucleation and polymerization of filamentous actin (F-actin). The polymerization and branching of F-actin is critical for creating force-generating cytoskeletal structures which drive most active cellular processes including migration, adhesion, immune synapse formation, and phagocytosis. Branched actin networks at the cell cortex have also been implicated in acting as a barrier to regulate inappropriate vesicle (e.g. cytokine) secretion and spontaneous antigen receptor crosslinking. Given the importance of the actin cytoskeleton in most or all hematopoietic cells, it is not surprising that HEM1 deficient children present with a complex clinical picture that involves overlapping features of immunodeficiency and autoimmunity. In this review, we will provide an overview of what is known about the molecular and cellular functions of HEM1 and the WRC in immune and other cells. We will describe the common clinicopathological features and immunophenotypes of HEM1 deficiency in humans and provide detailed comparative descriptions of what has been learned about Hem1 disruption using constitutive and immune cell-specific mouse knockout models. Finally, we discuss future perspectives and important areas for investigation regarding HEM1 and the WRC.

Presynaptic structural and functional plasticity are coupled by convergent Rap1 signaling

Dynamic presynaptic actin remodeling drives structural and functional plasticity at synapses, but the underlying mechanisms remain largely unknown. Previous work has shown that actin regulation via Rac1 guanine exchange factor (GEF) Vav signaling restrains synaptic growth via bone morphogenetic protein (BMP)-induced receptor macropinocytosis and mediates synaptic potentiation via mobilization of reserve pool vesicles in presynaptic boutons. Here, we find that Gef26/PDZ-GEF and small GTPase Rap1 signaling couples the BMP-induced activation of Abelson kinase to this Vav-mediated macropinocytosis. Moreover, we find that adenylate cyclase Rutabaga (Rut) signaling via exchange protein activated by cAMP (Epac) drives the mobilization of reserve pool vesicles during post-tetanic potentiation (PTP). We discover that Rap1 couples activation of Rut-cAMP-Epac signaling to Vav-mediated synaptic potentiation. These findings indicate that Rap1 acts as an essential, convergent node for Abelson kinase and cAMP signaling to mediate BMP-induced structural plasticity and activity-induced functional plasticity via Vav-dependent regulation of the presynaptic actin cytoskeleton.

Identification of small molecules that suppress cell invasion and metastasis promoted by WASF3 activation

The WASF3 gene promotes cancer cell invasion and metastasis, and genetic inactivation leads to suppression of metastasis. To identify small molecules that might interfere with WASF3 function, we performed an in silico docking study to the regulatory pocket of WASF3 using the National Cancer Institute (NCI) diversity set VI small molecule library. Compounds that showed the maximum likelihood of interaction with WASF3 were screened for their effect on cell movement in breast and prostate cancer cells, a well-established predictor of invasion and metastasis. Three hit compounds were identified that affected cell movement, and the same compounds also suppressed cell migration and invasion in vitro in both MDA-MB-231 breast cancer cells and Du145 prostate cancer cells. Using a zebrafish metastasis assay, one of these compounds, NSC670283, showed significant suppression of metastasis in vivo while not affecting cell proliferation. NSC670283 showed a consistent effect on suppression of invasion and metastasis, and cellular temperature shift assays provided support for physical interaction with WASF3. In addition, suppression of cell movement and invasion was accompanied by a decrease in actin filament polymerization. The data in this study suggest that these small molecules inhibit cancer cell invasion and metastasis, and to our knowledge, it is the first identification of a small molecule that can potentially inhibit WASF3-directed metastasis, laying the foundation for medicinal chemistry approaches to enhance the potency of the identified compounds.

Drug resistance related genes in lung adenocarcinoma predict patient prognosis and influence the tumor microenvironment

Lung adenocarcinoma (LUAD) is the predominant type of non-small lung cancer (NSCLC) with strong invasive ability and poor prognosis. The drug resistance related genes are potentially associated with prognosis of LUAD. Our research aimed to identify the drug resistance related genes and explore their potential prognostic value in LUAD patients. The data used in this study were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Firstly, we screened drug resistance related genes in LUAD by differential gene analysis, univariate Cox regression and drug sensitivity analyses. Subsequently, we constructed a risk score model using LASSO Cox regression analysis, and verified whether the risk score can predict the survival of LUAD patients independent of other factors. Moreover, we explored the immune infiltration of 22 immune cells between high-risk and low-risk patients. Totally 10 drug-resistance positively related genes (PLEK2, TFAP2A, KIF20A, S100P, GDF15, HSPB8, SASH1, WASF3, LAMA3 and TCN1) were identified in LUAD. The risk score model of LUAD constructed with these 10 genes could reliably predict the prognosis of LUAD patients. 18 pathways were significantly activated in high-risk group compared with low-risk group. In addition, the infiltration proportion of multiple immune cells was significantly different between high-risk and low-risk groups, and the proportion of M1 phagocytes was significantly higher in the high-risk group compared with the low-risk group. The drug resistance related genes (PLEK2, TFAP2A, KIF20A, S100P, GDF15, HSPB8, SASH1, WASF3, LAMA3 and TCN1) could predict the prognosis of LUAD patients. Clarifying the roles and mechanisms of these 10 genes in regulating drug resistance in LUAD will help to improve individualized clinical treatment protocols and predict patient sensitivity to treatment.

Orchestration of synaptic functions by WAVE regulatory complex-mediated actin reorganization

The WAVE regulatory complex (WRC), composed of five components-Cyfip1/Sra1, WAVE/Scar, Abi, Nap1/Nckap1, and Brk1/HSPC300-is essential for proper actin cytoskeletal dynamics and remodeling in eukaryotic cells, likely by matching various patterned signals to Arp2/3-mediated actin nucleation. Accumulating evidence from recent studies has revealed diverse functions of the WRC in neurons, demonstrating its crucial role in dictating the assembly of molecular complexes for the patterning of various trans-synaptic signals. In this review, we discuss recent exciting findings on the physiological role of the WRC in regulating synaptic properties and highlight the involvement of WRC dysfunction in various brain disorders.

The WAVE3/β-catenin oncogenic signaling regulates chemoresistance in triple negative breast cancer

BACKGROUND

Metastatic breast cancer is responsible for the death of the majority of breast cancer patients. In fact, metastatic BC is the 2nd leading cause of cancer-related deaths in women in the USA and worldwide. Triple negative breast cancer (TNBC), which lacks expression of hormone receptors (ER-α and PR) and ErbB2/HER2, is especially lethal due to its highly metastatic behavior, propensity to recur rapidly, and for its resistance to standard of care therapies, through mechanisms that remain incompletely understood. WAVE3 has been established as a promoter of TNBC development and metastatic progression. In this study, we investigated the molecular mechanisms whereby WAVE3 promotes therapy-resistance and cancer stemness in TNBC, through the regulation of β-catenin stabilization.

METHODS

The Cancer Genome Atlas dataset was used to assess the expression of WAVE3 and β-catenin in breast cancer tumors. Kaplan-Meier Plotter analysis was used to correlate expression of WAVE3 and β-catenin with breast cancer patients' survival probability. MTT assay was used to quantify cell survival. CRISPR/Cas9-mediated gene editing, 2D and 3D tumorsphere growth and invasion assays, Immunofluorescence, Western blotting, Semi-quantitative and real-time quantitative PCR analyses were applied to study the WAVE3/β-catenin oncogenic signaling in TNBC. Tumor xenograft assays were used to study the role of WAVE3 in mediating chemotherapy resistance of TNBC tumors.

RESULTS

Genetic inactivation of WAVE3 in combination of chemotherapy resulted in inhibition of 2D growth and 3D tumorsphere formation and invasion of TNBC cells in vitro, as well as tumor growth and metastasis in vivo. In addition, while re-expression of phospho-active WAVE3 in the WAVE3-deficient TNBC cells restored the oncogenic activity of WAVE3, re-expression of phospho-mutant WAVE3 did not. Further studies revealed that dual blocking of WAVE3 expression or phosphorylation in combination with chemotherapy treatment inhibited the activity and expression and stabilization of β-catenin. Most importantly, the combination of WAVE3-deficiency or WAVE3-phospho-deficiency and chemotherapy suppressed the oncogenic behavior of chemoresistant TNBC cells, both in vitro and in vivo.

CONCLUSION

We identified a novel WAVE3/β-catenin oncogenic signaling axis that modulates chemoresistance of TNBC. This study suggests that a targeted therapeutic strategy against WAVE3 could be effective for the treatment of chemoresistant TNBC tumors.

c-Abl Tyrosine Kinase Is Required for BDNF-Induced Dendritic Branching and Growth

Brain-derived neurotrophic factor (BDNF) induces activation of the TrkB receptor and several downstream pathways (MAPK, PI3K, PLC-γ), leading to neuronal survival, growth, and plasticity. It has been well established that TrkB signaling regulation is required for neurite formation and dendritic arborization, but the specific mechanism is not fully understood. The non-receptor tyrosine kinase c-Abl is a possible candidate regulator of this process, as it has been implicated in tyrosine kinase receptors' signaling and trafficking, as well as regulation of neuronal morphogenesis. To assess the role of c-Abl in BDNF-induced dendritic arborization, wild-type and c-Abl-KO neurons were stimulated with BDNF, and diverse strategies were employed to probe the function of c-Abl, including the use of pharmacological inhibitors, an allosteric c-Abl activator, and shRNA to downregulates c-Abl expression. Surprisingly, BDNF promoted c-Abl activation and interaction with TrkB receptors. Furthermore, pharmacological c-Abl inhibition and genetic ablation abolished BDNF-induced dendritic arborization and increased the availability of TrkB in the cell membrane. Interestingly, inhibition or genetic ablation of c-Abl had no effect on the classic TrkB downstream pathways. Together, our results suggest that BDNF/TrkB-dependent c-Abl activation is a novel and essential mechanism in TrkB signaling.

Structures reveal a key mechanism of WAVE regulatory complex activation by Rac1 GTPase

The Rho-family GTPase Rac1 activates the WAVE regulatory complex (WRC) to drive Arp2/3 complex-mediated actin polymerization in many essential processes. Rac1 binds to WRC at two distinct sites-the A and D sites. Precisely how Rac1 binds and how the binding triggers WRC activation remain unknown. Here we report WRC structures by itself, and when bound to single or double Rac1 molecules, at ~3 Å resolutions by cryogenic-electron microscopy. The structures reveal that Rac1 binds to the two sites by distinct mechanisms, and binding to the A site, but not the D site, drives WRC activation. Activation involves a series of unique conformational changes leading to the release of sequestered WCA (WH2-central-acidic) polypeptide, which stimulates the Arp2/3 complex to polymerize actin. Together with biochemical and cellular analyses, the structures provide a novel mechanistic understanding of how the Rac1-WRC-Arp2/3-actin signaling axis is regulated in diverse biological processes and diseases.

Targeting the WASF3 complex to suppress metastasis

Wiskott-Aldrich syndrome protein family members (WASF) regulate the dynamics of the actin cytoskeleton, which plays an instrumental role in cancer metastasis and invasion. WASF1/2/3 forms a hetero-pentameric complex with CYFIP1/2, NCKAP1/1 L, Abi1/2/3 and BRK1 called the WASF Regulatory Complex (WRC), which cooperatively regulates actin nucleation by WASF1/2/3. Activation of the WRC enables actin networking and provides the mechanical force required for the formation of lamellipodia and invadopodia. Although the WRC drives cell motility essential for several routine physiological functions, its aberrant deployment is observed in cancer metastasis and invasion. WASF3 expression is correlated with metastatic potential in several cancers and inversely correlates with overall progression-free survival. Therefore, disruption of the WRC may serve as a novel strategy for targeting metastasis. Given the complexity involved in the formation of the WRC which is largely comprised of large protein-protein interfaces, there are currently no inhibitors for WASF3. However, several constrained peptide mimics of the various protein-protein interaction interfaces within the WRC were found to successfully disrupt WASF3-mediated migration and invasion. This review explores the role of the WASF3 WRC in driving metastasis and how it may be selectively targeted for suppression of metastasis.

WASP family proteins: Molecular mechanisms and implications in human disease

Proteins of the Wiskott-Aldrich syndrome protein (WASP) family play a central role in regulating actin cytoskeletal dynamics in a wide range of cellular processes. Genetic mutations or misregulation of these proteins are tightly associated with many diseases. The WASP-family proteins act by transmitting various upstream signals to their conserved WH2-Central-Acidic (WCA) peptide sequence at the C-terminus, which in turn binds to the Arp2/3 complex to stimulate the formation of branched actin networks at membranes. Despite this common feature, the regulatory mechanisms and cellular functions of distinct WASP-family proteins are very different. Here, we summarize and clarify our current understanding of WASP-family proteins and how disruption of their functions is related to human disease.

Distinct peripheral blood monocyte and neutrophil transcriptional programs following intracerebral hemorrhage and different etiologies of ischemic stroke

Understanding cell-specific transcriptome responses following intracerebral hemorrhage (ICH) and ischemic stroke (IS) will improve knowledge of the immune response to brain injury. Transcriptomic profiles of 141 samples from 48 subjects with ICH, different IS etiologies, and vascular risk factor controls were characterized using RNA-seq in isolated neutrophils, monocytes and whole blood. In both IS and ICH, monocyte genes were down-regulated, whereas neutrophil gene expression changes were generally up-regulated. The monocyte down-regulated response to ICH included innate, adaptive immune, dendritic, NK cell and atherosclerosis signaling. Neutrophil responses to ICH included tRNA charging, mitochondrial dysfunction, and ER stress pathways. Common monocyte and neutrophil responses to ICH included interferon signaling, neuroinflammation, death receptor signaling, and NFAT pathways. Suppressed monocyte responses to IS included interferon and dendritic cell maturation signaling, phagosome formation, and IL-15 signaling. Activated neutrophil responses to IS included oxidative phosphorylation, mTOR, BMP, growth factor signaling, and calpain proteases-mediated blood-brain barrier (BBB) dysfunction. Common monocyte and neutrophil responses to IS included JAK1, JAK3, STAT3, and thrombopoietin signaling. Cell-type and cause-specific approaches will assist the search for future IS and ICH biomarkers and treatments.

Role of the ABL tyrosine kinases in the epithelial-mesenchymal transition and the metastatic cascade

The ABL kinases, ABL1 and ABL2, promote tumor progression and metastasis in various solid tumors. Recent reports have shown that ABL kinases have increased expression and/or activity in solid tumors and that ABL inactivation impairs metastasis. The therapeutic effects of ABL inactivation are due in part to ABL-dependent regulation of diverse cellular processes related to the epithelial to mesenchymal transition and subsequent steps in the metastatic cascade. ABL kinases target multiple signaling pathways required for promoting one or more steps in the metastatic cascade. These findings highlight the potential utility of specific ABL kinase inhibitors as a novel treatment paradigm for patients with advanced metastatic disease. Video abstract.

Phosphorylation of the proline-rich domain of WAVE3 drives its oncogenic activity in breast cancer

Post-translational modification of proteins, such as tyrosine phosphorylation, plays a major role in driving the oncogenic activity of oncogenes. WAVE3 (WASF3), an adaptor and actin cytoskeleton remodeling protein, contributes to cell migration, cancer cell invasion, and metastasis. WAVE3 plays a vital role in the progression and metastasis of triple negative breast cancer (TNBC), in part through the regulation of cancer stem cells (CSCs). Several studies have shown that WAVE3 tyrosine phosphorylation is required for its oncogenic activity. Moreover, our recent study showed that the proline rich domain (PRD) of WAVE3 is required for maintenance of the CSC niche in breast cancer by regulating the nuclear translocation of the CSC-specific nuclear transcription factor YB1. Here, we show that the PRD domain of WAVE3 and its phosphorylation are essential for driving the oncogenic activity of WAVE3. We show that phosphorylation of WAVE3 PRD is essential for migration and invasion of breast cancer cells in vitro, as well as tumor growth and metastasis in vivo. Mechanistically, we show that phosphorylation of the WAVE3 PRD is essential for interaction between WAVE3 and YB1. Loss of PRD phosphorylation inhibits such interaction and the YB1-mediated activation of expression of CSC markers, as well as the WAVE3 mediated activation of EMT. Together, our study identifies a novel role of WAVE3 and its PRD domain in the regulation of the invasion metastasis cascade in BC that is independent of the known function of WAVE3 as an actin cytoskeleton remodeling protein through the WAVE regulatory complex (WRC).

Targeting WASF3 Signaling in Metastatic Cancer

Increasing evidence indicates that cancer metastasis is regulated by specific genetic pathways independent of those controlling tumorigenesis and cancer growth. WASF3, a Wiskott–Aldrich syndrome protein family member, appears to play a major role not only in the regulation of actin cytoskeleton dynamics but also in cancer cell invasion/metastasis. Recent studies have highlighted that WASF3 is a master regulator and acts as a pivotal scaffolding protein, bringing the various components of metastatic signaling complexes together both spatially and temporally. Herein, targeting WASF3 at the levels of transcription, protein stability, and phosphorylation holds great promise for metastasis suppression, regardless of the diverse genetic backgrounds associated with tumor development. This review focuses on the critical and distinct contributions of WASF3 in the regulation of signal pathways promoting cancer cell invasion and metastasis.

WAVE3 phosphorylation regulates the interplay between PI3K, TGF-β, and EGF signaling pathways in breast cancer

Both TGF-β and the PI3K-AKT signaling pathways are known activators of various intracellular pathways that regulate critical cellular functions, including cancer cell survival and proliferation. The interplay between these two oncogenic pathways plays a major role in promoting the initiation, growth, and progression of tumors, including breast cancers. The molecular underpinning of the inter-relationship between these pathways is, however, not fully understood, as is the role of WAVE3 phosphorylation in the regulation of tumor growth and progression. WAVE3 has been established as a major driver of the invasion–metastasis cascade in breast cancer and other tumors of epithelial origin. WAVE3 phosphorylation downstream of PI3K was also shown to regulate cell migration. Here we show that, in addition to PI3K, WAVE3 tyrosine phosphorylation can also be achieved downstream of TGF-β and EGF and that WAVE3 tyrosine phosphorylation is required for its oncogenic activity. Our in vitro analyses found loss of WAVE3 phosphorylation to significantly inhibit cell migration, as well as tumorsphere growth and invasion. In mouse models for breast cancer, loss of WAVE3 phosphorylation inhibited tumor growth of two aggressive breast cancer cell lines of triple-negative subtype. More importantly, we found that WAVE3 phosphorylation is also required for the activation of PI3K, TGF-β, and EGF signaling and their respective downstream effectors. Therefore, our study identified a novel function for WAVE3 in the regulation of breast cancer development and progression through the modulation of a positive feedback loop between WAVE3 and PI3K-TGF-β-EGF signaling pathways.

Actin regulators in cancer progression and metastases: From structure and function to cytoskeletal dynamics

The cytoskeleton is a central factor contributing to various hallmarks of cancer. In recent years, there has been increasing evidence demonstrating the involvement of actin regulatory proteins in malignancy, and their dysregulation was shown to predict poor clinical prognosis. Although enhanced cytoskeletal activity is often associated with cancer progression, the expression of several inducers of actin polymerization is remarkably reduced in certain malignancies, and it is not completely clear how these changes promote tumorigenesis and metastases. The complexities involved in cytoskeletal induction of cancer progression therefore pose considerable difficulties for therapeutic intervention; it is not always clear which cytoskeletal regulator should be targeted in order to impede cancer progression, and whether this targeting may inadvertently enhance alternative invasive pathways which can aggravate tumor growth. The entire constellation of cytoskeletal machineries in eukaryotic cells are numerous and complex; the system is comprised of and regulated by hundreds of proteins, which could not be covered in a single review. Therefore, we will focus here on the actin cytoskeleton, which encompasses the biological machinery behind most of the key cellular functions altered in cancer, with specific emphasis on actin nucleating factors and nucleation-promoting factors. Finally, we discuss current therapeutic strategies for cancer which aim to target the cytoskeleton.

Elucidating the molecular signaling pathways of WAVE3

Cancer metastasis is a complex, multistep process that requires tumor cells to evade from the original site and form new tumors at a distant site or a different organ, often via bloodstream or the lymphatic system. Metastasis is responsible for more than 90% of cancer-related deaths. WAVE3 belongs to the Wiskott-Aldrich syndrome protein (WASP) family, which regulate actin cytoskeleton remodeling as well as several aspects of cell migration, invasion, and metastasis. In fact, WAVE3 has been established as a driver of tumor progression and metastasis in cancers from several origins, including triple negative breast cancers (TNBCs), which are classified as the most lethal subtype of breast cancer, due to their resistance to standard of care therapy and highly metastatic behavior. In this review, we will attempt to summarize the recent advances that have been made to understand how WAVE3 contributes to the molecular mechanisms that control cancer progression and metastasis. We will also review the signaling pathways that are involved in the regulation of WAVE3 expression and function to identify potential therapeutic options targeted against WAVE3 for the treatment of patients with metastatic tumors.

WAVE3 upregulation in esophageal squamous cell carcinoma and its effect on the migration of human esophageal cancer cell lines in vitro

The present study aimed to investigate the role of Wiskott-Aldrich syndrome verprolin-homologous protein 3 (WAVE3) in the progression of esophageal squamous cell carcinoma (ESCC), and to explore its effect on the migration of esophageal cancer cell lines in vitro. The expression level of WAVE3 in ESCC tissues was determined via immunohistochemistry, and the relative levels of WAVE3 mRNA and micro (mi)RNA200b were assessed in the serum of patients with ESCC using reverse transcription-quantitative PCR (RT-qPCR). Following cell transfection, the levels of miRNA200b and WAVE3 protein were determined via RT-qPCR and western blot analysis, and cell migration was examined using a Transwell assay. Subsequently, the clinical parameters were used to analyze whether the expression of WAVE3 in tissues and serum was associated with the occurrence and development of ESCC. The results demonstrated that the expression of WAVE3 was increased in ESCC tissues compared with normal tissues. The results also revealed increased expression levels of WAVE3 and decreased expression levels of miRNA200b in the serum of patients with ESCC, compared with healthy volunteers. High expression of WAVE3 was significantly associated with tumor TNM stage, invasion depth and lymphatic invasion of ESCC. In cells transfected with miRNA200b mimic, the miRNA200b was overexpressed, WAVE3 protein was downregulated and cell migration ability was decreased. The results of the present study suggest that WAVE3 may serve as an oncogene in ESCC, and its inhibition via miRNA200b decreased tumor cell migration. Therefore, WAVE3 may serve as a novel biological marker and therapeutic target for ESCC.

mir-124-5p Regulates Phagocytosis of Human Macrophages by Targeting the Actin Cytoskeleton via the ARP2/3 Complex

Phagocytosis is a cellular process crucial for recognition and removal of apoptotic cells and foreign particles, subsequently initiating appropriate immune responses. The process of phagocytosis is highly complex and involves major rearrangements of the cytoskeleton. Due to its complexity and importance for tissue homoeostasis and immune responses, it is tightly regulated. Over the last decade, microRNAs (miRNAs) have emerged as important regulators of biological pathways including the immune response by fine-tuning expression of gene regulatory networks. In order to identify miRNAs implicated in the regulation of phagocytosis, a systematic screening of all currently known, human miRNAs was performed using THP-1 macrophage-like cells and serum-opsonized latex beads. Of the total of 2,566 miRNAs analyzed, several led to significant changes in phagocytosis. Among these, we validated miR-124-5p as a novel regulator of phagocytosis. Transfection with miR-124-5p mimics reduced the number of phagocytic cells as well as the phagocytic activity of phorbol-12-myristate-13-acetate (PMA)-activated THP-1 cells and ex vivo differentiated primary human macrophages. In silico analysis suggested that miR-124-5p targets genes involved in regulation of the actin cytoskeleton. Transcriptional analyses revealed that expression of genes encoding for several subunits of the ARP2/3 complex, a crucial regulator of actin polymerization, is reduced upon transfection of cells with miR-124-5p. Further in silico analyses identified potential binding motifs for miR-124-5p in the mRNAs of these genes. Luciferase reporter assays using these binding motifs indicate that at least two of the genes (ARPC3 and ARPC4) are direct targets of miR-124-5p. Moreover, ARPC3 and ARPC4 protein levels were significantly reduced following miR-124-5p transfection. Collectively, the presented results suggest that miR-124-5p regulates phagocytosis in human macrophages by directly targeting expression of components of the ARP2/3 complex.

Wasf3 Deficiency Reveals Involvement in Metastasis in a Mouse Model of Breast Cancer

The WASF3 gene has been implicated in cancer cell movement, invasion, and metastasis by regulating genetic pathways important in these processes. Invasion and metastasis assays, however, are largely centered on xenograft models in immune-compromised mice. To facilitate analysis of the role of WASF3 in the spontaneous development of cancer cell metastasis, we generated a Wasf3 null strain by deleting exons 4 and 5, which encode essential motifs for Wasf3 function. On exposure to cre-recombinase a stop codon is generated immediately downstream in exon 6. Using a cytomegalovirus (CMV)-cre strain, Wasf3 constitutively was inactivated, which led to viable mice with no visible morphologic or behavioral abnormalities. There was no abnormal development or function of the mouse mammary gland in the Wasf3 null mice and brain development was normal. In the mouse mammary tumor virus (MMTV)-driven polyoma middle-T oncogene strain, which shows early onset breast cancer development and metastasis, Wiskott-Aldrich syndrome protein family member 3 (Wasf3) is up-regulated in metastatic lesions. When this oncogene was introduced onto the Wasf3-null background, although metastasis was observed in these mice, there was a reduction in the number and size of metastatic lesions in the lungs. These data provide evidence for a role in WASF3 in the development of metastasis in a spontaneous model of breast cancer.

De novo hotspot variants in CYFIP2 cause early-onset epileptic encephalopathy

OBJECTIVE

The cytoplasmic fragile X mental retardation 1 interacting proteins 2 (CYFIP2) is a component of the WASP-family verprolin-homologous protein (WAVE) regulatory complex, which is involved in actin dynamics. An obvious association of CYFIP2 variants with human neurological disorders has never been reported. Here, we identified de novo hotspot CYFIP2 variants in neurodevelopmental disorders and explore the possible involvement of the CYFIP2 mutants in the WAVE signaling pathway.

METHODS

We performed trio-based whole-exome sequencing (WES) in 210 families and case-only WES in 489 individuals with epileptic encephalopathies. The functional effect of CYFIP2 variants on WAVE signaling was evaluated by computational structural analysis and in vitro transfection experiments.

RESULTS

We identified three de novo CYFIP2 variants at the Arg87 residue in 4 unrelated individuals with early-onset epileptic encephalopathy. Structural analysis indicated that the Arg87 residue is buried at an interface between CYFIP2 and WAVE1, and the Arg87 variant may disrupt hydrogen bonding, leading to structural instability and aberrant activation of the WAVE regulatory complex. All mutant CYFIP2 showed comparatively weaker interactions to the VCA domain than wild-type CYFIP2. Immunofluorescence revealed that ectopic speckled accumulation of actin and CYFIP2 was significantly increased in cells transfected with mutant CYFIP2.

INTERPRETATION

Our findings suggest that de novo Arg87 variants in CYFIP2 have gain-of-function effects on the WAVE signaling pathway and are associated with severe neurological disorders. Ann Neurol 2018;83:794-806.

WASF3 expression correlates with poor prognosis in gastric cancer patients

Aim: WASF3 has been shown to be required for invasion and metastasis in different cancers, this study is to explore the prognostic value of WASF3 in gastric cancer. Materials & methods: The coexpression of WASF3 and E-cadherin in gastric cancer patients and cells were evaluated. Results: WASF3 was overexpressed and the expression of E-cadherin was decreased in gastric cancer tissues compared with normal tissues (p < 0.001). WASF3 expression is associated with decreased expression of E-cadherin (p = 0.002). Patients with WASF3-positive expression had a poorer prognosis. The multivariate analysis showed that WASF3 expression is an independent prognostic factor related to overall survival (p = 0.027). Conclusion: Our analysis demonstrates that WASF3 expression correlates with poor outcomes and is a potential prognostic factor in gastric cancer patients.

EnABLing Tumor Growth and Progression: Recent progress in unraveling the functions of ABL kinases in solid tumor cells

PURPOSE OF REVIEW

The goal of this review is to summarize our current knowledge regarding how ABL family kinases are activated in solid tumors and impact on solid tumor development/progression, with a focus on recent advances in the field.

RECENT FINDINGS

Although ABL kinases are known drivers of human leukemia, emerging data also implicates the kinases in a large number of solid tumor types where they promote diverse processes such as proliferation, survival, cytoskeletal reorganization, cellular polarity, EMT (epithelial-mesenchymal-transition), metabolic reprogramming, migration, invasion and metastasis via unique signaling pathways. ABL1 and ABL2 appear to have overlapping but also unique roles in driving these processes. In some tumor types, the kinases may act to integrate pro- and anti-proliferative and -invasive signals, and also may serve as a switch during EMT/MET (mesenchymal-epithelial) transitions.

CONCLUSIONS

Most data indicate that targeting ABL kinases may be effective for reducing tumor growth and preventing metastasis; however, ABL kinases also may have a tumor suppressive role in some tumor types and in some cellular contexts. Understanding the functions of ABL kinases in solid tumors is critical for developing successful clinical trials aimed at targeting ABL kinases for the treatment of solid tumors.

The Role of micro RNAs in Breast Cancer Metastasis: Preclinical Validation and Potential Therapeutic Targets

Despite the approval of several molecular therapies in the last years, breast cancer-associated death ranks as the second highest in women. This is due to metastatic disease, which represents a challenge for treatment. A better understanding of the molecular mechanisms of metastasis is, therefore, of paramount importance. In this review we summarize the role of micro RNAs (miRs) involved in metastasis of breast cancer. We present an overview on metastasis-promoting, -suppressing and context-dependent miRs with both activities. We have categorized the corresponding miRs according to their target classes, interaction with stromal cells or exosomes. The pathways affected by individual miRs are outlined in regard to in vitro properties, activity in metastasis-related in vivo models and clinical significance. Current approaches that may be suitable for therapeutic inhibition or restauration of miR activity are outlined. Finally, we discuss the delivery bottlenecks which present as a major challenge in nucleic acid (miR)-based therapies.

The WAVE3-YB1 interaction regulates cancer stem cells activity in breast cancer

Resistance to therapy is the main cause of tumor recurrence and metastasis and cancer stem cells (CSCs) play a crucial role in this process, especially in triple-negative breast cancers (TNBCs). Unfortunately, no FDA-approved treatment is currently available for this subtype of BC, which explains the high rate of mortality in patients with TNBC tumors. WAVE3, a member of the WASP/WAVE actin-cytoskeleton remodeling family of protein, has been established as a major driver of tumor progression and metastasis of several solid tumors, including those originating in the breast. Our recently published studies found WAVE3 to mediate the process of chemoresistance in TNBCs. The molecular mechanisms whereby WAVE3 regulates chemoresistance in TNBC tumors remains largely unknown, as does the role of WAVE3 in CSC maintenance. Here we show that WAVE3 promotes CSC self-renewal and regulates transcription of CSC-specific genes, which, in part, provides a mechanistic explanation for the function of WAVE3 in chemoresistance in TNBCs. Our data show that WAVE3 is enriched in the CSC-subpopulation of TNBC cell lines. Knockout of WAVE3 via CRISPR/Cas9 significantly attenuates the CSC-subpopulation and inhibits transcription of CSC transcription factors. Mechanistically, we established a link between WAVE3 and the Y-box-binding protein-1 (YB1), a transcription factor and CSC-maintenance gene. Indeed, the interaction of WAVE3 with YB1 is required for YB1 translocation to the nucleus of cancer cells, and activation of transcription of CSC-specific genes. Our findings identify a new WAVE3/YB1 signaling axis that regulates the CSC-mediated resistance to therapy and opens a new therapeutic window for TNBCs treatment.

p63α protein up-regulates heat shock protein 70 expression via E2F1 transcription factor 1, promoting Wasf3/Wave3/MMP9 signaling and bladder cancer invasion

Bladder cancer (BC) is the sixth most common cancer in the United States and is the number one cause of death among patients with urinary system malignancies. This makes the identification of invasive regulator(s)/effector(s) as the potential therapeutic targets for managing BC a high priority. p63 is a member of the p53 family of tumor suppressor genes/proteins, plays a role in the differentiation of epithelial tissues, and is believed to function as a tumor suppressor. However, it remains unclear whether and how p63 functions in BC cell invasion after tumorigenesis. Here, we show that p63α protein levels were much higher in mouse high-invasive BC tissues than in normal tissues. Our results also revealed that p63α is crucial for heat shock protein 70 (Hsp70) expression and subsequently increases the ability of BC invasion. Mechanistic experiments demonstrated that p63α can transcriptionally up-regulate Hsp70 expression, thereby promoting BC cell invasion via the Hsp70/Wasf3/Wave3/MMP-9 axis. We further show that E2F transcription factor 1 (E2F1) mediates p63α overexpression-induced Hsp70 transcription. We also found that p63α overexpression activates E2F1 transcription, which appears to be stimulated by p63α together with E2F1. Collectively, our results demonstrate that p63α is a positive regulator of BC cell invasion after tumorigenesis, providing significant insights into the biological function of p63α in BC and supporting the notion that p63α might be a potential target for invasive BC therapy.

Suppression of Breast Cancer Metastasis Using Stapled Peptides Targeting the WASF Regulatory Complex

The WASF3 gene facilitates the metastatic phenotype, and its inactivation leads to suppression of invasion and metastasis regardless of the genetic background of the cancer cell. This reliance on WASF3 to facilitate metastasis suggests that targeting its function could serve as an effective strategy to suppress metastasis. WASF3 stability and function are regulated by the WASF Regulatory Complex (WRC) of proteins, particularly CYFIP1 and NCKAP1. Knockdown of these proteins in vitro leads to disruption of the WRC and suppression of invasion. We have used mouse xenograft models of breast cancer metastasis to assess whether targeting the WRC complex suppresses metastasis in vivo. Stapled peptides targeting the WASF3-CYFIP1 interface (WAHM1) and the CYFIP1-NCKAP1 interface (WANT3) suppress the development of lung and liver metastases. Targeting these critical protein-protein interactions, therefore, could potentially be developed into a therapeutic strategy to control cancer cell invasion and metastasis.

Promotion of invasion by mutant RAS is dependent on activation of the WASF3 metastasis promoter gene

Metastasis represents an end stage in the evolution of cancer progression and has been related to specific genetic pathways. Overexpression of mutant RAS in particular appears to promote invasion and metastasis, although exactly how this occurs has not been well characterized. It was previously showed that activation of the WASF3 protein regulates actin cytoskeleton dynamics that promote invasion. In this report, how WASF3 overexpression interacts with mutant RAS to increase invasion and metastasis was investigated. The ability of RAS to promote invasion and metastasis was shown to be dependent on WASF3 activation in a PI3K and AKT dependent manner. Proteomics analysis demonstrates the presence of AKT in the WASF3 immunocomplex which is enhanced by overexpression of mutant RAS. During these processes activation of ERK1/2 is not affected by loss of WASF3 expression. Analysis of the relative involvement of p85 and p110 in the WASF3 complex demonstrates that mutant RAS promotes dissociation of p85 promoting activation of p110. These studies provide a deeper understanding of the critical role for WASF3 in facilitating increased invasion potential in cancer cells expressing mutant RAS and supports the idea that targeting WASF3 in metastatic cells overexpressing RAS may be used to suppress invasion and metastasis.

Multifunctional Abl kinases in health and disease

The Abelson tyrosine kinases were initially identified as drivers of leukemia in mice and humans. The Abl family kinases Abl1 and Abl2 regulate diverse cellular processes during development and normal homeostasis, and their functions are subverted during inflammation, cancer and other pathologies. Abl kinases can be activated by multiple stimuli leading to cytoskeletal reorganization required for cell morphogenesis, motility, adhesion and polarity. Depending on the cellular context, Abl kinases regulate cell survival and proliferation. Emerging data support important roles for Abl kinases in pathologies linked to inflammation. Among these are neurodegenerative diseases and inflammatory pathologies. Unexpectedly, Abl kinases have also been identified as important players in mammalian host cells during microbial pathogenesis. Thus, the use of Abl kinase inhibitors might prove to be effective in the treatment of pathologies beyond leukemia and solid tumors. In this Cell Science at a Glance article and in the accompanying poster, we highlight the emerging roles of Abl kinases in the regulation of cellular processes in normal cells and diverse pathologies ranging from cancer to microbial pathogenesis.

The WASF3-NCKAP1-CYFIP1 Complex Is Essential for Breast Cancer Metastasis

Inactivation of the WASF3 gene suppresses invasion and metastasis of breast cancer cells. WASF3 function is regulated through a protein complex that includes the NCKAP1 and CYFIP1 proteins. Here, we report that silencing NCKAP1 destabilizes the WASF3 complex, resulting in a suppression of the invasive capacity of breast, prostate, and colon cancer cells. In an in vivo model of spontaneous metastasis in immunocompromized mice, loss of NCKAP1 also suppresses metastasis. Activation of the WASF protein complex occurs through interaction with RAC1, and inactivation of NCKAP1 prevents the association of RAC1 with the WASF3 complex. Thus, WASF3 depends on NCKAP1 to promote invasion and metastasis. Here, we show that stapled peptides targeting the interface between NCKAP1 and CYFIP1 destabilize the WASF3 complex and suppress RAC1 binding, thereby suppressing invasion. Using a complex-disrupting compound identified in this study termed WANT3, our results offer a mechanistic proof of concept to target this interaction as a novel approach to inhibit breast cancer metastasis. Cancer Res; 76(17); 5133-42. ©2016 AACR.

WASF3 provides the conduit to facilitate invasion and metastasis in breast cancer cells through HER2/HER3 signaling

The WASF3 gene is overexpressed in high-grade breast cancer and promotes invasion and metastasis but does not affect proliferation. The HER2/ERBB2/NEU gene is also frequently overexpressed in breast cancer and has been shown to promote invasion and metastasis in these tumors. Here we show that WASF3 in present in the HER2 immunocomplex and suppression of WASF3 function leads to suppression of invasion even in the presence of HER2 expression. Overexpression of both HER2 and WASF3 in non-metastatic MCF7 breast cancer cells promotes invasion and metastasis more significantly than either gene alone. HER2 forms homodimers as well as heterodimers with other HER family members and we now show that the ability of WASF3 to promote invasion is highly dependent on the HER2/HER3 heterodimer. The engagement of WASF3 with the HER2/HER3 complex facilitates its phospho-activation and transcriptional upregulation, which is facilitated by HER2/HER3 activation of JAK/STAT signaling. In breast cancer cells overexpressing HER2, therefore, WASF3 is specifically required to facilitate the invasion/metastasis response. Targeting WASF3, therefore, could be a potential therapeutic approach to suppress metastasis of HER2-overexpressing breast tumors.

Role played by paxillin and paxillin tyrosine phosphorylation in hepatocyte growth factor/sphingosine-1-phosphate-mediated reactive oxygen species generation, lamellipodia formation, and endothelial barrier function

Paxillin is a multifunctional and multidomain focal adhesion adaptor protein. It serves as an important scaffolding protein at focal adhesions by recruiting and binding to structural and signaling molecules. Paxillin tyrosine phosphorylation at Y31 and Y118 is important for paxillin redistribution to focal adhesions and angiogenesis. Hepatocyte growth factor (HGF) and sphingosine-1-phosphate (S1P) are potent stimulators of lamellipodia formation, a prerequisite for endothelial cell migration. The role played by paxillin and its tyrosine phosphorylated forms in HGF- or S1P-induced lamellipodia formation and barrier function is unclear. HGF or S1P stimulated lamellipodia formation, tyrosine phosphorylation of paxillin at Y31 and Y118, and c-Abl in human lung microvascular endothelial cells (HLMVECs). Knockdown of paxillin with small interfering RNA (siRNA) or transfection with paxillin mutants (Y31F or Y118F) mitigated HGF- or S1P-induced lamellipodia formation, translocation of p47 (phox) to lamellipodia, and reactive oxygen species (ROS) generation in HLMVECs. Furthermore, exposure of HLMVECs to HGF or S1P stimulated c-Abl-mediated tyrosine phosphorylation of paxillin at Y31 and Y118 in a time-dependent fashion, and down-regulation of c-Abl with siRNA attenuated HGF- or S1P-mediated lamellipodia formation, translocation of p47 (phox) to lamellipodia, and endothelial barrier enhancement. In vivo, knockdown of paxillin with siRNA in mouse lungs attenuated ventilator-induced lung injury. Together, these results suggest that c-Abl-mediated tyrosine phosphorylation of paxillin at Y31 and Y118 regulates HGF- or S1P-mediated lamellipodia formation, ROS generation in lamellipodia, and endothelial permeability.

Targeting the WASF3-CYFIP1 Complex Using Stapled Peptides Suppresses Cancer Cell Invasion

Activation of the WASF3 protein by extracellular stimuli promotes actin cytoskeleton reorganization and facilitates cancer cell invasion, whereas WASF3 depletion suppresses invasion and metastasis. In quiescent cells, the interaction between WASF3 and a complex of proteins, including CYFIP1, acts as a conformational restraint to prevent WASF3 activation. Therefore, we took advantage of this endogenous regulatory mechanism to investigate potential sites that disrupt WASF3 function. Here, we show that genetic knockdown of CYFIP1 in cancer cells led to the destabilization of the WASF3 complex, loss of WASF3 function, and suppressed invasion. Based on existing crystallographic data, we developed stapled peptides, referred to as WASF Helix Mimics (WAHM), that target an α-helical interface between WASF3 and CYFIP1. Treatment of highly invasive breast and prostate cancer cells with WAHM inhibitor peptides significantly reduced motility and invasion in vitro. Mechanistic investigations revealed that these inhibitors suppressed the interaction between Rac and the WASF3 complex, which has been shown to promote cell migration. Furthermore, peptide-mediated inhibition of WASF3 also resulted in the dysregulation of known downstream targets such as MMP-9 and KISS1. Finally, we demonstrate that this invasive phenotype is specific to WASF3 as depletion of WASF1 and WASF2, which can also bind to CYFIP1, did not affect invasion. Collectively, our findings suggest that targeting WASF3 function with WAHM peptides could represent a promising therapeutic strategy for preventing tumor invasion and metastasis.

Cyclosporine A protects podocytes by regulating WAVE1 phosphorylation

Accumulating evidence suggests that podocytes are direct targets of many classic antiproteinuric drugs. The immunosuppressive drug cyclosporine A (CsA), which is a calcineurin inhibitor, is used to treat proteinuric kidney diseases. One novel mechanism by which CsA reduces proteinuria is by directly stabilizing the podocyte cytoskeleton. Previous studies showed that calcineurin can directly regulate WAVE1 within mouse striatal slices. In this study, WAVE1 was expressed in podocytes and was localized in the podocyte cell bodies and foot processes (FPs). WAVE1 expression increased in both in vivo and in vitro models of puromycin aminonucleoside (PAN)-induced podocyte injury. CsA restored WAVE1 expression and also partially rescued the disordered F-actin arrangement after PAN injury. Co-immunoprecipitation assays showed that calcineurin directly interacted with WAVE1 and regulated WAVE1 phosphorylation in podocytes. Synaptopodin is a well-characterized target of CsA. WAVE1 overexpression and synaptopodin knockdown experiments directly demonstrated that WAVE1 expression is not dependent on synaptopodin expression, and vice versa. Overexpression of WAVE1 using a WAVE1 plasmid disrupted F-actin structure and promoted podocyte migration compared with the empty vector group. Therefore, WAVE1 may be a novel molecular target for the maintenance of podocyte FPs and for antiproteinuric treatment in the future.

Mitochondrial ATAD3A combines with GRP78 to regulate the WASF3 metastasis-promoting protein

AAA domain containing 3A (ATAD3A) is an integral mitochondrial membrane protein with unknown function, although we now show that high-level expression is associated with poor survival in breast cancer patients. Using a mass spectrometry approach we have demonstrated that ATAD3A interacts with the WASF3 metastasis-promoting protein. Knockdown of ATAD3A leads to decreased WASF3 protein levels in breast and colon cancer cells. Silencing ATAD3A also results in loss of both cell anchorage-independent growth and invasion and suppression of tumor growth and metastasis in vivo using immuno-compromised mice. HSP70 is responsible for stabilizing WASF3 in the cytoplasm, but inactivation of HSP70 does not lead to the loss of WASF3 stability at the mitochondrial membrane, where presumably it is protected through its interaction with ATAD3A. In response to endoplasmic reticulum (ER) stress, increases in the GRP78 protein level leads to increased WASF3 protein levels. We also show that ATAD3A was present in a WASF3-GRP78 complex, and suppression of GRP78 led to destabilization of WASF3 at the mitochondrial membrane, which was ATAD3A dependent. Furthermore, ATAD3A-mediated suppression of CDH1/E-cadherin occurs through its regulation of GRP78-mediated WASF3 stability. Proteolysis experiments using isolated mitochondria demonstrates the presence of the N-terminal end of WASF3 within the mitochondria, which is the interaction site with the N-terminal end of ATAD3A. It appears, therefore, that stabilization of WASF3 function occurs through its interaction with ATAD3A and GRP78, which may provide a bridge between the ER and mitochondria, allowing communication between the two organelles. These findings also suggest that pharmacologic inhibition of ATAD3A could be an effective therapeutic strategy to treat human cancer.

Targeting Abl kinases to regulate vascular leak during sepsis and acute respiratory distress syndrome

The vascular endothelium separates circulating fluid and inflammatory cells from the surrounding tissues. Vascular leak occurs in response to wide-spread inflammatory processes, such as sepsis and acute respiratory distress syndrome, because of the formation of gaps between endothelial cells. Although these disorders are leading causes of mortality in the intensive care unit, no medical therapies exist to restore endothelial cell barrier function. Recent evidence highlights a key role for the Abl family of nonreceptor tyrosine kinases in regulating vascular barrier integrity. These kinases have well-described roles in cancer progression and neuronal morphogenesis, but their functions in the vasculature have remained enigmatic until recently. The Abl family kinases, c-Abl (Abl1) and Abl related gene (Arg, Abl2), phosphorylate several cytoskeletal effectors that mediate vascular permeability, including nonmuscle myosin light chain kinase, cortactin, vinculin, and β-catenin. They also regulate cell-cell and cell-matrix junction dynamics, and the formation of actin-based cellular protrusions in multiple cell types. In addition, both c-Abl and Arg are activated by hyperoxia and contribute to oxidant-induced endothelial cell injury. These numerous roles of Abl kinases in endothelial cells and the current clinical usage of imatinib and other Abl kinase inhibitors have spurred recent interest in repurposing these drugs for the treatment of vascular barrier dysfunction. This review will describe the structure and function of Abl kinases with an emphasis on their roles in mediating vascular barrier integrity. We will also provide a critical evaluation of the potential for exploiting Abl kinase inhibition as a novel therapy for inflammatory vascular leak syndromes.

Loss of WAVE3 sensitizes triple-negative breast cancers to chemotherapeutics by inhibiting the STAT-HIF-1α-mediated angiogenesis

Chemoresistance allows for disease to recur and ultimately causes the death of most breast cancer patients. This scenario is particularly relevant in patients harboring triple-negative breast cancer (TNBC) tumors for which there are no effective FDA-approved drugs. However, a recent study determined that TNBCs can be segregated into 6 genetically distinct subtypes that do in fact exhibit differential rates of pathological complete response (pCR) to standard-of-care chemotherapies. Of these, the mesenchymal and mesenchymal stem-like subtypes of TNBCs exhibit the lowest rates of pCR when treated with standard-of-care chemotherapies. WAVE3 is an actin-cytoskeleton remodeling protein, and recent studies have highlighted a potential role for WAVE3 in promoting tumor progression and metastasis in TNBC. However, whether WAVE3 activity is involved in the development of chemoresistance in TNBCs remains unclear. Here we show that loss of WAVE3 expression resensitizes human TNBC cells to doxorubicin and docetaxel, as measured by increased apoptosis and cell death. We also show that WAVE3 knockdown in the chemotherapy-treated TNBC cells results in inhibition of STAT1 phosphorylation, as well as a significant decrease in expression levels of its downstream effector HIF-1α. Since HIF-1α is a major activator of VEGF-A production, and therefore a stimulator of tumor angiogenesis, loss of HIF-1α in the WAVE3-knockdown cells resulted in the inhibition the chemotherapy-mediated VEGF-A secretion and the downstream activation of angiogenesis, a phenomenon that often accompanies chemoresistance. Our data identify a critical role of WAVE3 in sensitizing TNBC to chemotherapy by inhibiting the STAT1→HIF-1α→VEGF-A signaling axis, and support the possibility that WAVE3 inhibition may be a promising target for TNBC cancer therapy.

Nonstructural protein 1 (NS1)-mediated inhibition of c-Abl results in acute lung injury and priming for bacterial co-infections: insights into 1918 H1N1 pandemic?

BACKGROUND

Nonstructural protein 1 (NS1) proteins from avian influenza viruses like the 1918 pandemic NS1 are capable of inhibiting the key signaling integrator c-Abl (Abl1), resulting in massive cytopathic cell alterations.

METHODS

In the current study, we addressed the consequences of NS1-mediated alteration of c-Abl on acute lung injury and pathogenicity in an in vivo mouse model.

RESULTS

Comparing isogenic strains that differ only in their ability to inhibit c-Abl, we observed elevated pathogenicity for the c-Abl-inhibiting virus. NS1-mediated blockade of c-Abl resulted in severe lung pathology and massive edema formation and facilitated secondary bacterial pneumonia. This phenotype was independent of differences in replication and immune responses, defining it as an NS1 virulence mechanism distinct from its canonical functions. Microarray analysis revealed extensive downregulation of genes involved in cell integrity and vascular endothelial regulation.

CONCLUSIONS

NS1 protein-mediated blockade of c-Abl signaling drives acute lung injury and primes for bacterial coinfections revealing potential insights into the pathogenicity of the 1918 pandemic virus.

WAVE3-NFκB interplay is essential for the survival and invasion of cancer cells

The WAVE3 cytoskeletal protein promotes cancer invasion and metastasis. We have shown that the WAVE3-mediated activation of cancer cell invasion is due, in part, to its regulation of expression and activity of key metalloproteinases (MMPs), including MMP9, which is centrally involved in invadopodia-mediated degradation of the extracellular matrix (ECM). MMP9 is also a major NFκB target gene, suggesting a potential linkage of WAVE3 to this pathway, which we sought to investigate. Mechanistically, we found that loss of WAVE3 in cancer cells leads to inhibition of NFκB signaling as a result of a decrease in the nuclear translocation of NFκB and therefore loss of activation of NFκB target genes. Conversely, overexpression of WAVE3 was sufficient to enhance NFκB activity. Both pharmacologic and genetic manipulations of NFκB effector molecules show that the biological consequence of loss of WAVE3 function in the NFκB pathway result the inhibition of invadopodia formation and ECM degradation by cancer cells, and these changes are a consequence of decreased MMP9 expression and activity. Loss of WAVE3 also sensitized cancer cells to apoptosis and cell death driven by TNFα, through the inhibition of the AKT pro-survival pathway. Our results identify a novel function of WAVE3 in NFκB signaling, where its activity is essential for the regulation of invadopodia and ECM degradation. Therefore, targeted therapeutic inhibition of WAVE3 will sensitize cancer cells to apoptosis and cell death, and suppress cancer invasion and metastasis.

Steering cell migration: lamellipodium dynamics and the regulation of directional persistence

Membrane protrusions at the leading edge of cells, known as lamellipodia, drive cell migration in many normal and pathological situations. Lamellipodial protrusion is powered by actin polymerization, which is mediated by the actin-related protein 2/3 (ARP2/3)-induced nucleation of branched actin networks and the elongation of actin filaments. Recently, advances have been made in our understanding of positive and negative ARP2/3 regulators (such as the SCAR/WAVE (SCAR/WASP family verprolin-homologous protein) complex and Arpin, respectively) and of proteins that control actin branch stability (such as glial maturation factor (GMF)) or actin filament elongation (such as ENA/VASP proteins) in lamellipodium dynamics and cell migration. This Review highlights how the balance between actin filament branching and elongation, and between the positive and negative feedback loops that regulate these activities, determines lamellipodial persistence. Importantly, directional persistence, which results from lamellipodial persistence, emerges as a critical factor in steering cell migration.

Avian influenza viruses inhibit the major cellular signalling integrator c-Abl

The non-structural protein 1 (NS1) of influenza A viruses (IAV) encodes several src homology (SH) binding motifs (bm) (one SH2bm, up to two SH3bm), which mediate interactions with host cell proteins. In contrast to NS1 of human IAV, NS1 of avian strains possess the second SH3bm (SH3(II)bm) consensus sequence. Since our former studies demonstrated an NS1-CRK interaction, mediated by this motif, here, we addressed the regulatory properties of this SH3bm for cellular signalling. Initially, we observed a reduced basal CRK phosphorylation upon infection with avian IAV harbouring an NS1 with an SH3(II)bm in contrast to human IAV. Reduced activity of the tyrosine kinase c-Abl was identified to be responsible for reduced CRK phosphorylation. Further, binding of NS1 to c-Abl was determined, and mutational manipulation of the SH3(II)bm illustrated the necessity of this motif for c-Abl inhibition. Interestingly, Abl kinase inhibition resulted in impaired avian IAV propagation and pathogenicity and mutational analysis linked the pronounced inhibition of c-Abl to cytopathogenic cell alterations upon avian IAV infections. Taken together, NS1 proteins of avian IAV interfere with the kinase activity of c-Abl, a major cellular signalling integrator that controls multiple signalling processes and cell fate regulations apparently including IAV infections.

Expression of WASF3 in patients with non-small cell lung cancer: Correlation with clinicopathological features and prognosis

Wiskott-Aldrich syndrome protein family member 3 (WASF3) is required for invasion and metastasis in different cancer cell types, and has been demonstrated to possess prognostic value in various types of human cancer. However, to the best of our knowledge, the expression profile of WASF3 and its correlations with the clinicopathological features of non-small cell lung cancer (NSCLC) have not yet been described. In the present study, the mRNA expression levels of WASF3, in 38 NSCLC patients and in matched normal tissues, were assessed using quantitative polymerase chain reaction and the protein expression in 96 specimens was analyzed using immunohistochemistry. In addition, patient survival data were collected retrospectively and the association between WASF3 expression and five-year overall survival was evaluated. The results demonstrated that the mRNA expression level of WASF3 in cancer tissues was markedly (approximately five times) higher compared with that of the normal tissues. The WASF3 protein expression profile in NSCLC was consistent with the mRNA expression result, which also correlated with the histological subtype and tumor stage. Furthermore, patients with WASF3-positive expression were associated with a poorer prognosis compared with those exhibiting WASF3-negative expression, and the five-year survival rate was 20.8 and 46.5%, respectively (Kaplan-Meier; log-rank, P=0.004). In the multivariate analysis, which included other clinicopathological features, WASF3 emerged as an independent prognostic factor (relative risk, 0.463; 95% CI, 0.271–0.792). These results indicate that WASF3 may be critical in the pathogenesis of NSCLC, in addition to being a valuable prognostic factor for NSCLC patients. Further investigations are required to identify the efficacy of WASF3 as a potential therapeutic target for the treatment of NSCLC.

The involvement of JAK-STAT3 in cell motility, invasion, and metastasis

JAK-STAT3 signaling, while regulating many aspects of cancer development and progression, promotes invasion and metastasis through activation of key metastasis promoting genes such as WASF3. STAT3 promotes WASF3 expression and JAK2 independently activates it, which is required for invasion. JAK-STAT3 signaling is dependent on WASF3 function, since its inactivation in cells expressing JAK-STAT3 suppresses invasion. WASF3 overexpression leads to activation of NFκB and ZEB1 which also promote invasion through regulation of target genes involved in metastasis. NFκB frequently cooperates with STAT3 to upregulate metastasis promoting genes such as matrix metalloproteinases and cytokines, as well as to suppress microRNAs which can suppresses invasion. This better understanding of the complex role played by JAK-STAT3 in the regulation of cell movement, invasion, and metastasis provides opportunities to suppress this lethal aspect of cancer progression by not only targeting the JAK and STAT3 proteins directly, but also some of the downstream effectors of JAK-STAT3 signaling.

Upregulated WAVE3 expression is essential for TGF-β-mediated EMT and metastasis of triple-negative breast cancer cells

Breast cancer is the second leading cause of cancer death in women in the United States. Metastasis accounts for the death of ~90 % of these patients, yet the mechanisms underlying this event remain poorly defined. WAVE3 belongs to the WASP/WAVE family of actin-binding proteins that play essential roles in regulating cell morphology, actin polymerization, cytoskeleton remodeling, cell motility, and invasion. Accordingly, we demonstrated previously that WAVE3 promotes the acquisition of invasive and metastatic phenotypes by human breast cancers. Herein, we show that transforming growth factor-β (TGF-β) selectively and robustly induced the expression of WAVE3 in metastatic breast cancer cells, but not in their nonmetastatic counterparts. Moreover, the induction of WAVE3 expression in human and mouse triple-negative breast cancer cells (TNBCs) by TGF-β likely reflects its coupling to microRNA expression via a Smad2- and β3 integrin-dependent mechanism. We further demonstrate the requirement for WAVE3 expression in mediating the initiation of epithelial-mesenchymal transition (EMT) programs stimulated by TGF-β. Indeed, stable depletion of WAVE3 expression in human TNBC cells prevented TGF-β from inducing EMT programs and from stimulating the proliferation, migration, and the formation of lamellipodia in metastatic TNBC cells. Lastly, we observed WAVE3 deficiency to abrogate the outgrowth of TNBC cell organoids in 3-dimensional organotypic cultures as well as to decrease the growth and metastasis of 4T1 tumors produced in syngeneic Balb/C mice. Indeed, WAVE3 deficiency significantly reduced the presence of sarcomatoid morphologies indicative of EMT phenotypes in pulmonary TNBC tumors as compared to those detected in their parental counterparts. Collectively, these findings indicate the necessity for WAVE3 expression and activity during EMT programs stimulated by TGF-β; they also suggest that measures capable of inactivating WAVE3 may play a role in alleviating metastasis stimulated by TGF-β.

c-Abl and Arg induce cathepsin-mediated lysosomal degradation of the NM23-H1 metastasis suppressor in invasive cancer

Metastasis suppressors comprise a growing class of genes whose downregulation triggers metastatic progression. In contrast to tumor suppressors, metastasis suppressors are rarely mutated or deleted, and little is known regarding the mechanisms by which their expression is downregulated. Here, we demonstrate that the metastasis suppressor, NM23-H1, is degraded by lysosomal cysteine cathepsins (L,B), which directly cleave NM23-H1. In addition, activation of c-Abl and Arg oncoproteins induces NM23-H1 degradation in invasive cancer cells by increasing cysteine cathepsin transcription and activation. Moreover, c-Abl activates cathepsins by promoting endosome maturation, which facilitates trafficking of NM23-H1 to the lysosome where it is degraded. Importantly, the invasion- and metastasis-promoting activity of c-Abl/Arg is dependent on their ability to induce NM23-H1 degradation, and the pathway is clinically relevant as c-Abl/Arg activity and NM23-H1 expression are inversely correlated in primary breast cancers and melanomas. Thus, we demonstrate a novel mechanism by which cathepsin expression is upregulated in cancer cells (via Abl kinases). We also identify a novel role for intracellular cathepsins in invasion and metastasis (degradation of a metastasis suppressor). Finally, we identify novel crosstalk between oncogenic and metastasis suppressor pathways, thereby providing mechanistic insight into the process of NM23-H1 loss, which may pave the way for new strategies to restore NM23-H1 expression and block metastatic progression.

Critical role of the WASF3 gene in JAK2/STAT3 regulation of cancer cell motility

WASF3 has been shown to be required for invasion and metastasis in different cancer cell types and knockdown of WASF3 leads to suppression of invasion/metastasis. Aberrant signaling through the interleukin 6/Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) axis in cancer cells has emerged as a major mechanism for cancer progression. In this study, we demonstrate that interleukin 6 induces both WASF3 expression and phosphoactivation in breast and prostate cancer cell lines through the JAK2/STAT3 pathway in two different ways. First, we show that STAT3 binds directly to the WASF3 promoter and increases transcription levels, which correlates with increased migration potential. Inactivation of STAT3 with short hairpin RNA, dominant negative constructs or S3I-201 leads to reduced WASF3 levels and reduced migration. Second, we have shown that JAK2, while activating STAT3, also interacts with and activates WASF3. Inhibition of JAK2 with short hairpin RNA or AG490 leads to loss of migration due to reduced WASF3 activation levels and prevention of its membrane localization. Together, these results define a novel signaling network whereby JAK2/STAT3 signaling creates a feed-forward loop to raise activated WASF3 levels that promote cancer cell motility.

Surfing the big WAVE: Insights into the role of WAVE3 as a driving force in cancer progression and metastasis

WAVE3 belongs to the WASP/WAVE family of actin cytoskeleton remodeling proteins. These proteins are known to be involved in several biological functions ranging from controlling cell shape and movement, to being closely associated with pathological conditions such as cancer progression and metastasis. Last decade has seen an explosion in the literature reporting significant scientific advances on the molecular mechanisms whereby the WASP/WAVE proteins are regulated both in normal physiological as well as pathological conditions. The purpose of this review is to present the major findings pertaining to how WAVE3 has become a critical player in the regulation of signaling pathways involved in cancer progression and metastasis. The review will conclude with suggesting options for the potential use of WAVE3 as a therapeutic target to prevent the progression of cancer to the lethal stage that is the metastatic disease.

Phosphoregulation of the WAVE regulatory complex and signal integration

The WAVE2 regulatory complex (WRC) induces actin polymerization by activating the actin nucleator Arp2/3. Polymerizing actin pushes against the cell membrane and induces dramatic edge protrusions. In order to properly control such changes in cell morphology and function, cells have evolved multiple methods to tightly regulate WRC and Arp2/3 activity in space and time. Of these mechanisms, phosphorylation plays a fundamental role in transmitting extracellular and intracellular signals to the WRC and the actin cytoskeleton. This review discusses the phosphorylation-based regulatory inputs into the WRC. Signaling pathways that respond to growth factors, chemokines, hormones, and extracellular matrix converge upon the WAVE and ABI components of the WRC. The Abl, Src, ERK, and PKA kinases promote complex activation through a WRC conformation change that permits interaction with the Arp2/3 complex and through WRC translocation to the cell edge. The neuron-specific CDK5 and constitutively active CK2 kinases inhibit WRC activation. These regulatory signals are integrated in space and time as they coalesce upon the WRC. The combination of WRC phosphorylation events and WRC activity is controlled by stimulus, cell type, and cell cycle-specific pathway activation and via pathway cross-inhibition and cross-activation.