WIP Drives Tumor Progression through YAP/TAZ-Dependent Autonomous Cell Growth

Multifaceted role of the actin-binding protein WIP: Promotor and inhibitor of tumor progression and dissemination

Cancer cells depend on actin cytoskeleton reorganization to achieve hallmark malignant functions including abnormal activation, proliferation, migration and invasiveness. (Neural)-Wiskott-Aldrich Syndrome protein ((N-)WASP) binds actin and forms a complex with the WASP-interacting protein (WIP), which plays a critical role in regulating the actin cytoskeleton, through (N)-WASP-dependent and independent functions. Mutations in the WIP gene (WIPF1) lead to severe early onset immunodeficiency in humans and severe autoimmunity and shortened lifespan in mice. This review covers the available evidence about the physiological role of WIP in different tissues and its contribution to human disease, focusing on cancer. In solid tumors overexpression of WIP has mostly been associated with tumor initiation, progression and dissemination through matrix degradation by invadopodia, while a suppressive function has been shown for WIP in certain hematological cancers. Interestingly, a minority of studies suggest a protective role for WIP in specific tumor contexts. These data support the need for further research to fully understand the mechanisms underlying WIP's diverse functions in health and disease and raise important questions for future work.

Compression drives diverse transcriptomic and phenotypic adaptations in melanoma

Physical forces are prominent during tumor progression. However, it is still unclear how they impact and drive the diverse phenotypes found in cancer. Here, we apply an integrative approach to investigate the impact of compression on melanoma cells. We apply bioinformatics to screen for the most significant compression-induced transcriptomic changes and investigate phenotypic responses. We show that compression-induced transcriptomic changes are associated with both improvement and worsening of patient prognoses. Phenotypically, volumetric compression inhibits cell proliferation and cell migration. It also induces organelle stress and intracellular oxidative stress and increases pigmentation in malignant melanoma cells and normal human melanocytes. Finally, cells that have undergone compression become more resistant to cisplatin treatment. Our findings indicate that volumetric compression is a double-edged sword for melanoma progression and drives tumor evolution.

Bone marrow mesenchymal/fibroblastic stromal cells induce a distinctive EMT-like phenotype in AML cells

The development of epithelial-to-mesenchymal transition (EMT) like features is emerging as a critical factor involved in the pathogenesis of acute myeloid leukaemia (AML). However, the extracellular signals and the signalling pathways in AML that may regulate EMT remain largely unstudied. We found that the bone marrow (BM) mesenchymal/fibroblastic cell line HS5 induces an EMT-like migratory phenotype in AML cells. AML cells underwent a strong increase of vimentin (VIM) levels that was not mirrored to the same extent by changes of expression of the other EMT core proteins SNAI1 and SNAI2. We validated these particular pattern of co-expression of core-EMT markers in AML cells by performing an in silico analysis using datasets of human tumours. Our data showed that in AML the expression levels of VIM does not completely correlate with the co-expression of core EMT markers observed in epithelial tumours. We also found that vs epithelial tumours, AML cells display a distinct patterns of co-expression of VIM and the actin binding and adhesion regulatory proteins that regulate F-actin dynamics and integrin-mediated adhesions involved in the invasive migration in cells undergoing EMT. We conclude that the BM stroma induces an EMT related pattern of migration in AML cells in a process involving a distinctive regulation of EMT markers and of regulators of cell adhesion and actin dynamics that should be further investigated. Understanding the tumour specific signalling pathways associated with the EMT process may contribute to the development of new tailored therapies for AML as well as in different types of cancers.

Stiff Substrate Induces Nucleus Pulposus Cell Ferroptosis via YAP and N-Cadherin Mediated Mechanotransduction

Increased tissue stiffness is associated with various pathological processes, such as fibrosis, inflammation, and aging. The matrix stiffness of the nucleus pulposus (NP) tissues increases gradually during intervertebral disc degeneration (IDD), while the mechanism through which NP cells sense and react to matrix stiffness remains unclear. In this study, the results indicate that ferroptosis is involved in stiff substrate-induced NP cell death. The expression of acyl-CoA synthetase long-chain family member 4 (ACSL4) increases in NP cells of the stiff group, which mediates lipid peroxidation and ferroptosis in NP cells. In addition, stiff substrate activates the hippo signaling cascade and induces the nuclear translocation of yes-associated protein (YAP). Interestingly, inhibition of YAP is efficient to reverse the increase of ACSL4 expression caused by matrix stiffness. Furthermore, stiff substrate suppresses the expression of N-cadherin in NP cells. N-cadherin overexpression can inhibit YAP nuclear translocation via the formation of the N-cadherin/β-catenin/YAP complex, and reverse matrix stiffness-induced ferroptosis in NP cells. Finally, the effects of YAP inhibition and N-cadherin overexpression on IDD progression are further illustrated in animal models. These findings reveal a new mechanism of mechanotransduction in NP cells, providing novel insights into the development of therapies for the treatment of IDD.

The regulatory role of LncRNA HCG18 in various cancers

As a member of long non-coding RNAs (lncRNAs), LncRNA HLA complex group 18 (HCG18) has recently become the focus of cancer research. As outlined in this review, LncRNA HCG18 has been reported to be dysregulated in various cancers development and appears to be activated in a variety of tumors, including clear cell renal cell carcinoma (ccRCC), colorectal cancer (CRC), gastric cancer (GC), hepatocellular carcinoma (HCC), laryngeal and hypopharyngeal squamous cell carcinoma (LHSCC), lung adenocarcinoma (LUAD), nasopharyngeal cancer (NPC), osteosarcoma (OS), and prostate cancer (PCa). Furthermore, the expression of lncRNA HCG18 decreased in bladder cancer (BC) and papillary thyroid cancer (PTC). Overall, the presence of these differential expressions suggests the clinical value of HCG18 in cancer therapy. Additionally, lncRNA HCG18 influences various biological processes of cancer cells. This review summarizes the molecular mechanisms of HCG18 in cancer development, highlights reported the abnormal expression of HCG18 found in various cancer types, and aims to discuss the potential of HCG18 as a target for cancer therapy.

The role of long non-coding RNA HCG18 in cancer

The incidence of cancer is increasing worldwide and is becoming the most common cause of death. Identifying new biomarkers for cancer diagnosis and prognosis is important for developing cancer treatment strategies and reducing mortality. Long non-coding RNAs (lncRNAs) are non-coding, single-stranded RNAs that play an important role as oncogenes or tumor suppressors in the occurrence and development of human tumors. Abnormal expression of human leukocyte antigen complex group 18 (HCG18) is observed in many types of cancer, and its imbalance is closely related to cancer progression. HCG18 regulates cell proliferation, invasion, metastasis, and anti-apoptosis through a variety of mechanisms. Therefore, HCG18 is a potential tumor biomarker and therapeutic target. However, the therapeutic significance of HCG18 has not been well studied, and future research may develop new intervention strategies to combat cancer. In this study, we reviewed the biological function, mechanism, and potential clinical significance of HCG18 in various cancers to provide a reference for future research.

A calpain-6/YAP axis in sarcoma stem cells that drives the outgrowth of tumors and metastases

Sarcomas include cancer stem cells, but how these cells contribute to local and metastatic relapse is largely unknown. We previously showed the pro-tumor functions of calpain-6 in sarcoma stem cells. Here, we use an osteosarcoma cell model, osteosarcoma tissues and transcriptomic data from human tumors to study gene patterns associated with calpain-6 expression or suppression. Calpain-6 modulates the expression of Hippo pathway genes and stabilizes the hippo effector YAP. It also modulates the vesicular trafficking of β-catenin degradation complexes. Calpain-6 expression is associated with genes of the G2M phase of the cell cycle, supports G2M-related YAP activities and up-regulated genes controlling mitosis in sarcoma stem cells and tissues. In mouse models of bone sarcoma, most tumor cells expressed calpain-6 during the early steps of tumor out-growth. YAP inhibition prevented the neoformation of primary tumors and metastases but had no effect on already developed tumors. It could even accelerate lung metastasis associated with large bone tumors by affecting tumor-associated inflammation in the host tissues. Our results highlight a specific mechanism involving YAP transcriptional activity in cancer stem cells that is crucial during the early steps of tumor and metastasis outgrowth and that could be targeted to prevent sarcoma relapse.

The interplay between noncoding RNA and YAP/TAZ signaling in cancers: molecular functions and mechanisms

The Hippo signaling pathway was found coordinately modulates cell regeneration and organ size. Its dysregulation contributes to uncontrolled cell proliferation and malignant transformation. YAP/TAZ are two critical effectors of the Hippo pathway and have been demonstrated essential for the initiation or growth of most tumors. Noncoding RNAs (ncRNAs), including miRNAs, lncRNAs, and circRNAs, have been shown to play critical roles in the development of many cancers. In the past few decades, a growing number of studies have revealed that ncRNAs can directly or indirectly regulate YAP/TAZ signaling. YAP/TAZ also regulate ncRNAs expression in return. This review summarizes the interactions between YAP/TAZ signaling and noncoding RNAs together with their biological functions on cancer progression. We also try to describe the complex feedback loop existing between these components.

Self-Sustained Regulation or Self-Perpetuating Dysregulation: ROS-dependent HIF-YAP-Notch Signaling as a Double-Edged Sword on Stem Cell Physiology and Tumorigenesis

Organ development, homeostasis, and repair often rely on bidirectional, self-organized cell-niche interactions, through which cells select cell fate, such as stem cell self-renewal and differentiation. The niche contains multiplexed chemical and mechanical factors. How cells interpret niche structural information such as the 3D topology of organs and integrate with multiplexed mechano-chemical signals is an open and active research field. Among all the niche factors, reactive oxygen species (ROS) have recently gained growing interest. Once considered harmful, ROS are now recognized as an important niche factor in the regulation of tissue mechanics and topology through, for example, the HIF-YAP-Notch signaling pathways. These pathways are not only involved in the regulation of stem cell physiology but also associated with inflammation, neurological disorder, aging, tumorigenesis, and the regulation of the immune checkpoint molecule PD-L1. Positive feedback circuits have been identified in the interplay of ROS and HIF-YAP-Notch signaling, leading to the possibility that under aberrant conditions, self-organized, ROS-dependent physiological regulations can be switched to self-perpetuating dysregulation, making ROS a double-edged sword at the interface of stem cell physiology and tumorigenesis. In this review, we discuss the recent findings on how ROS and tissue mechanics affect YAP-HIF-Notch-PD-L1 signaling, hoping that the knowledge can be used to design strategies for stem cell-based and ROS-targeting therapy and tissue engineering.

The Cytoskeleton Effectors Rho-Kinase (ROCK) and Mammalian Diaphanous-Related (mDia) Formin Have Dynamic Roles in Tumor Microtube Formation in Invasive Glioblastoma Cells

Glioblastoma (GBM) is a progressive and lethal brain cancer. Malignant control of actin and microtubule cytoskeletal mechanics facilitates two major GBM therapeutic resistance strategies-diffuse invasion and tumor microtube network formation. Actin and microtubule reorganization is controlled by Rho-GTPases, which exert their effects through downstream effector protein activation, including Rho-associated kinases (ROCK) 1 and 2 and mammalian diaphanous-related (mDia) formins (mDia1, 2, and 3). Precise spatial and temporal balancing of the activity between these effectors dictates cell shape, adhesion turnover, and motility. Using small molecules targeting mDia, we demonstrated that global agonism (IMM02) was superior to antagonism (SMIFH2) as anti-invasion strategies in GBM spheroids. Here, we use IDH-wild-type GBM patient-derived cell models and a novel semi-adherent in vitro system to investigate the relationship between ROCK and mDia in invasion and tumor microtube networks. IMM02-mediated mDia agonism disrupts invasion in GBM patient-derived spheroid models, in part by inducing mDia expression loss and tumor microtube network collapse. Pharmacological disruption of ROCK prevented invasive cell-body movement away from GBM spheres, yet induced ultralong, phenotypically abnormal tumor microtube formation. Simultaneously targeting mDia and ROCK did not enhance the anti-invasive/-tumor microtube effects of IMM02. Our data reveal that targeting mDia is a viable GBM anti-invasion/-tumor microtube networking strategy, while ROCK inhibition is contraindicated.

Abnormal Glycosylation in Cancer Cells and Cancer Stem Cells as a Therapeutic Target

Tumor resistance and recurrence have been associated with the presence of cancer stem cells (CSCs) in tumors. The functions and survival of the CSCs have been associated with several intracellular and extracellular features. Particularly, the abnormal glycosylation of these signaling pathways and markers of CSCs have been correlated with maintaining survival, self-renewal and extravasation properties. Here, we highlight the importance of glycosylation in promoting the stemness character of CSCs and the current strategies for targeting abnormal glycosylation toward generating effective therapies against the CSC population.

Cytoskeleton-associated protein 4 (CKAP4) promotes malignant progression of human gliomas through inhibition of the Hippo signaling pathway

PURPOSE

Gliomas are the most common and aggressive malignant brain tumors and are associated with high mortality and incidence in humans. Despite rigorous multi-modal therapy, including surgery, chemotherapy and radiotherapy, patients with malignant glioma survive an average of 12-15 months following primary diagnosis. Therefore, new molecular biomarkers are urgently needed for diagnosis and targeted therapy. Here, we find that suppression of CKAP4 might inhibit glioma growth through regulation of Hippo signaling.

METHODS

We examined the expression levels of CKAP4 through analysis of RNA sequencing data from GEPIA and CGGA databases. Then, Lentivirus was used to construct stable cell lines with knockout or overexpression of CKAP4. Next, the function of CKAP4 on glioma was investigated in vitro and in an orthotopic brain tumor model in mice. Lastly, luciferase reporter assay, immunofluorescence and immunoblotting were performed to explore the potential mechanism of how CKAP4 affects gliomas.

RESULTS

CKAP4 is highly upregulated in glioma and high CKAP4 expressing tumors were associated with poor patient survival. And CKAP4 promotes malignant progression of gliomas via inhibiting Hippo signaling.

CONCLUSION

CKAP4 has potential as a promising biomarker and can predict the prognosis of patients with gliomas. And targeting CKAP4 expression may be an effective therapeutic strategy for the treatment of human gliomas.

WIP, YAP/TAZ and Actin Connections Orchestrate Development and Transformation in the Central Nervous System

YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif) are transcription co-regulators that make up the terminal components of the Hippo signaling pathway, which plays a role in organ size control and derived tissue homeostasis through regulation of the proliferation, differentiation and apoptosis of a wide variety of differentiated and stem cells. Hippo/YAP signaling contributes to normal development of the nervous system, as it participates in self-renewal of neural stem cells, proliferation of neural progenitor cells and differentiation, activation and myelination of glial cells. Not surprisingly, alterations in this pathway underlie the development of severe neurological diseases. In glioblastomas, YAP and TAZ levels directly correlate with the amount of the actin-binding molecule WIP (WASP interacting protein), which regulates stemness and invasiveness. In neurons, WIP modulates cytoskeleton dynamics through actin polymerization/depolymerization and acts as a negative regulator of neuritogenesis, dendrite branching and dendritic spine formation. Our working hypothesis is that WIP regulates the YAP/TAZ pools using a Hippo-independent pathway. Thus, in this review we will present some of the data that links WIP, YAP and TAZ, with a focus on their function in cells from the central and peripheral nervous systems. It is hoped that a better understanding of the mechanisms involved in brain and nervous development and the pathologies that arise due to their alteration will reveal novel therapeutic targets for neurologic diseases.

Selective Inhibition of Esophageal Cancer Stem-like Cells with Salinomycin

BACKGROUND

Targeting Cancer Stem-Like Cells (CSLCs) can provide promising new therapeutic strategies to inhibit cancer progression, metastasis and recurrence. Salinomycin (Sal), an antibacterial ionophore, has been shown to inhibit CSCs specifically. Recently, it has been reported that Sal can destabilize TAZ, the hypo pathway transducer in CSLCs.

OBJECTIVES

Here, in the current study, we aimed to assess the differential toxicity of Sal in esophageal CSLCs and its relation to TAZ gene expression.

METHODS

The esophageal cancer cell line, KYSE-30, was used for the enrichment of CSLCs. The expression of TAZ was knocked down using specific siRNA transfection and then the cytotoxicity of Sal was measured using XTT assay. The qRT-PCR method was used for gene expression assessment and the sphere formation ability was monitored using light microscopy.

RESULTS

Our findings showed that esophageal CSLCs over-express stemness-associated genes, including SOX2, OCT4 as well as TAZ (~14 fold, P value=0.02) transcription coactivator. We found Sal can selectively inhibit KYSE-30 CSLCs viability and sphere formation ability; however, TAZ knockdown does not change its differential toxicity.

CONCLUSION

Overall, our results indicated that Sal can selectively decrease the viability of esophageal CSLCs in a TAZ-independent manner.

Abnormal Glycosylation of Cancer Stem Cells and Targeting Strategies

Cancer stem cell (CSCs) are deemed as one of the main reasons of tumor relapse due to their resistance to standard therapies. Numerous intracellular signaling pathways along with extracellular features are crucial in regulating CSCs properties, such as heterogeneity, plasticity and differentiation. Aberrant glycosylation of these cellular signaling pathways and markers of CSCs have been directly correlated with maintaining survival, self-renewal and extravasation properties. In this review, we highlight the importance of glycosylation in promoting stemness character of CSCs, and present strategies for targeting abnormal glycosylation to eliminate the resistant CSC population.

The IDH-TAU-EGFR triad defines the neovascular landscape of diffuse gliomas

Gliomas that express the mutated isoforms of isocitrate dehydrogenase 1/2 (IDH1/2) have better prognosis than wild-type (wt) IDH1/2 gliomas. However, how these mutant (mut) proteins affect the tumor microenvironment is still a pending question. Here, we describe that the transcription of microtubule-associated protein TAU (MAPT), a gene that has been classically associated with neurodegenerative diseases, is epigenetically controlled by the balance between wt and mut IDH1/2 in mouse and human gliomas. In IDH1/2 mut tumors, we found high expression of TAU that decreased with tumor progression. Furthermore, MAPT was almost absent from tumors with epidermal growth factor receptor (EGFR) mutations, whereas its trancription negatively correlated with overall survival in gliomas carrying wt or amplified (amp) EGFR We demonstrated that the overexpression of TAU, through the stabilization of microtubules, impaired the mesenchymal/pericyte-like transformation of glioma cells by blocking EGFR, nuclear factor kappa-light-chain-enhancer of activated B (NF-κB) and the transcriptional coactivator with PDZ-binding motif (TAZ). Our data also showed that mut EGFR induced a constitutive activation of this pathway, which was no longer sensitive to TAU. By inhibiting the transdifferentiation capacity of EGFRamp/wt tumor cells, TAU protein inhibited angiogenesis and favored vascular normalization, decreasing glioma aggressiveness and increasing their sensitivity to chemotherapy.

Long noncoding RNA HCG18 up-regulates the expression of WIPF1 and YAP/TAZ by inhibiting miR-141-3p in gastric cancer

BACKGROUND

Accumulating works show that lncRNAs play critical roles in the development of gastric cancer (GC). LncRNA HLA complex group 18 (HCG18) was implicated in the progression of bladder cancer and glioma, but its role in GC is unknown.

METHODS

RT-PCR was used to detect HCG18 and miR-141-3p expression in GC specimen. GC cell lines (AGS and MKN-28) were exploited as cell model. The biological effect of HCG18 on cancer cells was probed by CCK-8, colony formation, flow cytometry, Transwell and wound-healing experiments in vitro, and subcutaneous xenotransplanted tumor model and tail vein injection model in vivo. Interaction between HCG18 and miR-141-3p was determined by bioinformatics analysis, RT-PCR, and luciferase reporter experiments. Downstream gene expression of miR-141-3p, including Wiskott-Aldrich syndrome protein interacting protein family member 1 (WIPF1), Yes associated protein 1 (YAP), and tafazzin (TAZ) were detected using Western blot.

RESULTS

HCG18 was markedly up-regulated in GC specimens, while miR-141-3p was markedly down-regulated. Down-regulation of HCG18 inhibited viability, migration, and invasion of GC cells, while miR-141-3p transfection led to opposite effect. HCG18 could down-regulate miR-141-3p through adsorbing it, and a negative association between HCG18 and miR-141-3p was found in GC specimens. HCG18 promoted WIPF1, YAP and TAZ expression, nonetheless, such influence was reversed by co-transfecting with miR-141-3p.

CONCLUSION

HCG18 was aberrantly up-regulated in GC tissues, and it indirectly regulated the activity of Hippo signaling through counteracting miR-141-3p expression.

WIP Modulates Oxidative Stress through NRF2/KEAP1 in Glioblastoma Cells

Due to their high metabolic rate, tumor cells produce exacerbated levels of reactive oxygen species that need to be under control. Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP) is a scaffold protein with multiple yet poorly understood functions that participates in tumor progression and promotes cancer cell survival. However, its participation in the control of oxidative stress has not been addressed yet. We show that WIP depletion increases the levels of reactive oxygen species and reduces the levels of transcription factor NRF2, the master regulator of redox homeostasis. We found that WIP stabilizes NRF2 by restraining the activity of its main NRF2 repressor, the E3 ligase adapter KEAP1, because the overexpression of a NRF2ΔETGE mutant that is resistant to targeted proteasome degradation by KEAP1 or the knock-down of KEAP1 maintains NRF2 levels in the absence of WIP. Mechanistically, we show that the increased KEAP1 activity in WIP-depleted cells is not due to the protection of KEAP1 from autophagic degradation, but is dependent on the organization of the Actin cytoskeleton, probably through binding between KEAP1 and F-Actin. Our study provides a new role of WIP in maintaining the oxidant tolerance of cancer cells that may have therapeutic implications.

The Disordered Cellular Multi-Tasker WIP and Its Protein-Protein Interactions: A Structural View

WASp-interacting protein (WIP), a regulator of actin cytoskeleton assembly and remodeling, is a cellular multi-tasker and a key member of a network of protein-protein interactions, with significant impact on health and disease. Here, we attempt to complement the well-established understanding of WIP function from cell biology studies, summarized in several reviews, with a structural description of WIP interactions, highlighting works that present a molecular view of WIP's protein-protein interactions. This provides a deeper understanding of the mechanisms by which WIP mediates its biological functions. The fully disordered WIP also serves as an intriguing example of how intrinsically disordered proteins (IDPs) exert their function. WIP consists of consecutive small functional domains and motifs that interact with a host of cellular partners, with a striking preponderance of proline-rich motif capable of interactions with several well-recognized binding partners; indeed, over 30% of the WIP primary structure are proline residues. We focus on the binding motifs and binding interfaces of three important WIP segments, the actin-binding N-terminal domain, the central domain that binds SH3 domains of various interaction partners, and the WASp-binding C-terminal domain. Beyond the obvious importance of a more fundamental understanding of the biology of this central cellular player, this approach carries an immediate and highly beneficial effect on drug-design efforts targeting WIP and its binding partners. These factors make the value of such structural studies, challenging as they are, readily apparent.

Role of Hippo-YAP1/TAZ pathway and its crosstalk in cardiac biology

The Hippo pathway undertakes a pivotal role in organ size control and the process of physiology and pathology in tissue. Its downstream effectors YAP1 and TAZ receive upstream stimuli and exert transcription activity to produce biological output. Studies have demonstrated that the Hippo pathway contributes to maintenance of cardiac homeostasis and occurrence of cardiac disease. And these cardiac biological events are affected by crosstalk among Hippo-YAP1/TAZ, Wnt/β-catenin, Bone morphogenetic protein (BMP) and G-protein-coupled receptor (GPCR) signaling, which provides new insights into the Hippo pathway in heart. This review delineates the interaction among Hippo, Wnt, BMP and GPCR pathways and discusses the effects of these pathways in cardiac biology.

PD-L1 promotes tumor growth and progression by activating WIP and β-catenin signaling pathways and predicts poor prognosis in lung cancer

PD-L1 is overexpressed in tumor cells and contributes to cancer immunoevasion. However, the role of the tumor cell-intrinsic PD-L1 in cancers remains unknown. Here we show that PD-L1 regulates lung cancer growth and progression by targeting the WIP and β-catenin signaling. Overexpression of PD-L1 promotes tumor cell growth, migration and invasion in lung cancer cells, whereas PD-L1 knockdown has the opposite effects. We have also identified WIP as a new downstream target of PD-L1 in lung cancer. PD-L1 positively modulates the expression of WIP. Knockdown of WIP also inhibits cell viability and colony formation, whereas PD-L1 overexpression can reverse this inhibition effects. In addition, PD-L1 can upregulate β-catenin by inhibiting its degradation through PI3K/Akt signaling pathway. Moreover, we show that in lung cancer cells β-catenin can bind to the WIP promoter and activate its transcription, which can be promoted by PD-L1 overexpression. The in vivo experiments in a human lung cancer mouse model have also confirmed the PD-L1-mediated promotion of tumor growth and progression through activating the WIP and β-catenin pathways. Furthermore, we demonstrate that PD-L1 expression is positively correlated with WIP in tumor tissues of human adenocarcinoma patients and the high expression of PD-L1 and WIP predicts poor prognosis. Collectively, our results provide new insights into understanding the pro-tumorigenic role of PD-L1 and its regulatory mechanism on WIP in lung cancer, and suggest that the PD-L1/Akt/β-catenin/WIP signaling axis may be a potential therapeutic target for lung cancers.

Loss of Wasl improves pancreatic cancer outcome

Several studies have suggested an oncogenic role for the neural Wiskott-Aldrich syndrome protein (N-WASP, encoded by the Wasl gene), but thus far, little is known about its function in pancreatic ductal adenocarcinoma (PDAC). In this study, we performed in silico analysis of WASL expression in PDAC patients and found a correlation between low WASL expression and prolonged survival. To clarify the role of Wasl in pancreatic carcinogenesis, we used 2 oncogenic Kras-based PDAC mouse models with pancreas-specific Wasl deletion. In line with human data, both mouse models had an increased survival benefit due to either impaired tumor development in the presence of the tumor suppressor Trp53 or the delayed tumor progression and senescent phenotype upon genetic ablation of Trp53. Mechanistically, loss of Wasl resulted in cell-autonomous senescence through displacement of the N-WASP binding partners WASP-interacting protein (WIP) and p120ctn; vesicular accumulation of GSK3β, as well as YAP1 and phosphorylated β-catenin, which are components of the destruction complex; and upregulation of Cdkn1a(p21), a master regulator of senescence. Our findings, thus, indicate that Wasl functions in an oncogenic manner in PDAC by promoting the deregulation of the p120-catenin/β-catenin/p21 pathway. Therefore, strategies to reduce N-WASP activity might improve the survival outcomes of PDAC patients.

Meeting Report - Workshop 'Actin-based mechanosensation and force generation in health and disease'

International experts in the fields of cellular motility, force generation and mechanosensation met in Baeza, a UNESCO World Heritage city, from the 10th to the 13th of November, 2019. The meeting, part of the 'Current Trends in Biomedicine' series, took place at the 'Sede Antonio Machado', a beautiful 17th century building turned into a conference center of the Universidad Internacional de Andalucía (UNIA), which sponsored the event. The meeting was organized by Alexis Gautreau, Pekka Lappalainen and Miguel Vicente-Manzanares, with the support of the European Molecular Biology Organization (EMBO) and the Spanish-based company IMPETUX. Fifty scientists presented recent results during the talks, poster sessions and thematic discussions. As Baeza itself served as a crossroads of medieval Christian, Moorish and Jewish cultures, the meeting brought together cell biologists, biochemists, biophysicists and engineers from around the world that provided an integrated vision of the role of the actin cytoskeleton, force generation and mechanosensation in diverse physiological processes and pathologies.

The EGFR-TMEM167A-p53 Axis Defines the Aggressiveness of Gliomas

Despite the high frequency of EGFR and TP53 genetic alterations in gliomas, little is known about their crosstalk during tumor progression. Here, we described a mutually exclusive distribution between mutations in these two genes. We found that wild-type p53 gliomas are more aggressive than their mutant counterparts, probably because the former accumulate amplifications and/or mutations in EGFR and show a stronger activation of this receptor. In addition, we identified a series of genes associated with vesicular trafficking of EGFR in p53 wild-type gliomas. Among these genes, TMEM167A showed the strongest implication in overall survival in this group of tumors. In agreement with this observation, inhibition of TMEM167A expression impaired the subcutaneous and the intracranial growth of wild-type p53 gliomas, regardless of the presence of EGFR mutations. In the absence of p53 mutations, TMEM167A knockdown reduced the acidification of intracellular vesicles, affecting the autophagy process and impairing EGFR trafficking and signaling. This effect was mimicked by an inhibitor of the vacuolar ATPase. We propose that the increased aggressiveness of wild-type p53 gliomas might be due to the increase in growth factor signaling activity, which depends on the regulation of vesicular trafficking by TMEM167A.

Transcription factor NRF2 uses the Hippo pathway effector TAZ to induce tumorigenesis in glioblastomas

Transcription factor NRF2 orchestrates a cellular defense against oxidative stress and, so far, has been involved in tumor progression by providing a metabolic adaptation to tumorigenic demands and resistance to chemotherapeutics. In this study, we discover that NRF2 also propels tumorigenesis in gliomas and glioblastomas by inducing the expression of the transcriptional co-activator TAZ, a protein of the Hippo signaling pathway that promotes tumor growth. The expression of the genes encoding NRF2 (NFE2L2) and TAZ (WWTR1) showed a positive correlation in 721 gliomas from The Cancer Genome Atlas database. Moreover, NRF2 and TAZ protein levels also correlated in immunohistochemical tissue arrays of glioblastomas. Genetic knock-down of NRF2 decreased, while NRF2 overexpression or chemical activation with sulforaphane, increased TAZ transcript and protein levels. Mechanistically, we identified several NRF2-regulated functional enhancers in the regulatory region of WWTR1. The relevance of the new NRF2/TAZ axis in tumorigenesis was demonstrated in subcutaneous and intracranial grafts. Thus, intracranial inoculation of NRF2-depleted glioma stem cells did not develop tumors as determined by magnetic resonance imaging. Forced TAZ overexpression partly rescued both stem cell growth in neurospheres and tumorigenicity. Hence, NRF2 not only enables tumor cells to be competent to proliferate but it also propels tumorigenesis by activating the TAZ-mediated Hippo transcriptional program.

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Expression of NRF2 and TAZ positively correlate in gliomas and glioblastomas.

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NRF2 regulates the expression of WWTR1 encoding the transcription co-activator TAZ in glioma stem cells.

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TAZ provides a redox-independent mechanism of NRF2 induction of glioblastomas.

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Downregulation of the new NRF2/TAZ axis may provide a novel therapy for glioblastomas.

Wnt signaling inhibition by monensin results in a period of Hippo pathway activation during intestinal adaptation in zebrafish

Intestinal adaptation (IA) is a critical response to increase epithelial surface area after intestinal loss. Short bowel syndrome (SBS) may follow massive intestinal resection in human patients, particularly without adequate IA. We previously validated a model in zebrafish (ZF) that recapitulates key SBS pathophysiological features. Previous RNA sequencing in this model identified upregulation of genes in the Wnt and Hippo pathways. We therefore sought to identify the timeline of increasing cell proliferation and considered the signaling that might underpin the epithelial remodeling of IA in SBS. SBS was created in a ZF model as previously reported and compared with sham fish with and without exposure to monensin, an ionophore known to inhibit canonical Wnt signaling. Rescue of the monensin effects was attempted with a glycogen synthase kinase 3 inhibitor that activates wnt signaling, CHIR-99021. A timeline was constructed to identify peak cellular proliferation, and the Wnt and Hippo pathways were evaluated. Peak stem cell proliferation and morphological changes of adaptation were identified at 7 days. Wnt inhibition diminished IA at 2 wk and resulted in activation of genes of the Wnt/β-catenin and Yes-associated protein (YAP)/Hippo pathway. Increased cytoplasmic YAP was observed in monensin-treated SBS fish. Genes of the WASP-interacting protein (WIP) pathway were elevated during Wnt blockade. In conclusion, cellular proliferation and morphological changes accompany SBS even in attempted Wnt blockade. Wnt/β-catenin, YAP/Hippo pathway, and WIP pathway genes increase during early Wnt blockade. Further understanding of the effects of Wnt and YAP pathway signaling in proliferating stem cells might enrich our knowledge of targets to assist IA. NEW & NOTEWORTHY Intestinal adaptation is a critical response to increase epithelial surface area after large intestinal losses. Inhibition of Wnt/β-catenin signaling impairs intestinal adaptation in a zebrafish model of short bowel syndrome. There is a subsequent upregulation in genes of the Yes-associated protein/Hippo and WIP pathway. These may be targets for future human therapies, as patients are salvaged by the compensation of increased intestinal epithelial surface area through successful intestinal adaptation.

Mechanical Roles of F-Actin in the Differentiation of Stem Cells: A Review

In the development and differentiation of stem cells, mechanical forces associated with filamentous actin (F-actin) play a crucial role. The present review aims to reveal the relationship among the chemical components, microscopic structures, mechanical properties, and biological functions of F-actin. Particular attention is given to the functions of the cytoplasmic and nuclear microfilament cytoskeleton and their regulation mechanisms in the differentiation of stem cells. The distributions of different types of actin monomers in mammal cells and the functions of actin-binding proteins are summarized. We discuss how the fate of stem cells is regulated by intra/extracellular mechanical and chemical cues associated with microfilament-related proteins, intercellular adhesion molecules, etc. In addition, we also address the differentiation-induced variation in the stiffness of stem cells and the correlation between the fate and geometric shape change of stem cells. This review not only deepens our understanding of the biophysical mechanisms underlying the fates of stem cells under different culture conditions but also provides inspirations for the tissue engineering of stem cells.

YAP/TAZ upstream signals and downstream responses

Cell behaviour is strongly influenced by physical, mechanical contacts between cells and their extracellular matrix. We review how the transcriptional regulators YAP and TAZ integrate mechanical cues with the response to soluble signals and metabolic pathways to control multiple aspects of cell behaviour, including proliferation, cell plasticity and stemness essential for tissue regeneration. Corruption of cell-environment interplay leads to aberrant YAP and TAZ activation that is instrumental for multiple diseases, including cancer.

WIPF1 antagonizes the tumor suppressive effect of miR-141/200c and is associated with poor survival in patients with PDAC

Background

Aberrant expression of Wiskott–Aldrich syndrome protein interacting protein family member 1 (WIPF1) contributes to the invasion and metastasis of several malignancies. However, the role of WIPF1 in human pancreatic ductal adenocarcinoma (PDAC) remains poorly understood.

Methods

Human pancreatic cancer samples from PDAC patients were collected for methylation analysis. Bioinformatic prediction program and luciferase reporter assay were used to identify microRNAs regulating WIPF1 expression. The association between WIPF1 expression and the overall survival (OS) of patients with PDAC was evaluated by using The Cancer Genome Atlas (TCGA) database. The roles of miR-141/200c and WIPF1 on the invasion and metastasis of PDAC cells were investigated both in vitro and in vivo.

Results

We found that compared to the surrounding non-cancerous tissues, there was significantly increased methylation of miR-200c and miR-141 in human PDAC tissues that resulted in their silencing, whereas the members of the other cluster of miR-200 family including miR-200a, miR-200b and miR-429 were hypomethylated. Our data show that forced expression of miR-141 or miR-200c suppressed invasion and metastasis of PDAC cells both in vitro and in xenograft and identified WIPF1 as a direct target of miR-141 and miR-200c. Both miR-141 and miR-200c inhibit WIPF1 by directly interacting with its 3′-untranslated region. Remarkably, silencing of WIPF1 blocked PDAC growth and metastasis both in vitro and in vivo, whereas forced WIPF1 overexpression antagonized the tumor suppressive effect of miR-141/200c. Additionally, by using TCGA database we showed that high expression of WIPF1 correlated with poor survival in patients with PDAC. Moreover, we show that miR-141 and miR-200c blocked YAP/TAZ expression by suppressing WIPF1.

Conclusions

We have identified WIPF1 as an oncoprotein in PDAC and a direct target of miR-141/miR-200c. We have also defined the miR-141/200c-WIPF1-YAP/TAZ as a novel signaling pathway that is involved in the regulation of the invasion and metastasis of human PDAC cells.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0848-6) contains supplementary material, which is available to authorized users.

WIP/ITSN1 complex is involved in cellular vesicle trafficking and formation of filopodia-like protrusions

WIP (WASP interacting protein) together with N-WASP (neural Wiskott-Aldrich syndrome protein) regulates actin polymerization that is crucial for invadopodia and filopodia formation. Recently, we reported the WIP interaction with ITSN1 which is highly implicated in endo-/exocytosis, apoptosis, mitogenic signaling and cytoskeleton rearrangements. Here we demonstrate that the WIP/ITSN1 complex is involved in the transferrin receptor recycling and partially co-localizes with a marker of the fast recycling endosomes, RAB4. Moreover, ITSN1 recruits WIP to RAB4-positive vesicles upon overexpression. Our data indicate that WIP enhances the interaction of N-WASP with ITSN1 and promotes ITSN1/β-actin association. Moreover, the WIP/ITSN1-L complex facilitates formation of filopodia-like protrusions in MCF-7 cells. Thus, WIP/ITSN1 complex is involved in the cellular vesicle trafficking and actin-dependent membrane processes.

Complexes formed by mutant p53 and their roles in breast cancer

Breast cancer is the most frequently diagnosed malignancy in women, and mutations in the tumor suppressor p53 are commonly detected in the most aggressive subtypes. The majority of TP53 gene alterations are missense substitutions, leading to expression of mutant forms of the p53 protein that are frequently detected at high levels in cancer cells. P53 mutants not only lose the physiological tumor-suppressive activity of the wild-type p53 protein but also acquire novel powerful oncogenic functions, referred to as gain of function, that may actively confer a selective advantage during tumor progression. Some of the best-characterized oncogenic activities of mutant p53 are mediated by its ability to form aberrant protein complexes with other transcription factors or proteins not directly related to gene transcription. The set of cellular proteins available to interact with mutant p53 is dependent on cell type and extensively affected by environmental signals, so the prognostic impact of p53 mutation is complex. Specific functional interactions of mutant p53 can profoundly impact homeostasis of breast cancer cells, reprogramming gene expression in response to specific extracellular inputs or cell-intrinsic conditions. The list of protein complexes involving mutant p53 in breast cancer is continuously growing, as is the number of oncogenic phenotypes in which they could be involved. In consideration of the functional impact of such complexes, key interactions of mutant p53 may be exploited as potential targets for development of therapies aimed at defusing the oncogenic potential of p53 mutation.

WIP-YAP/TAZ as A New Pro-Oncogenic Pathway in Glioma

Wild-type p53 (wtp53) is described as a tumour suppressor gene, and mutations in p53 occur in many human cancers. Indeed, in high-grade malignant glioma, numerous molecular genetics studies have established central roles of RTK-PI3K-PTEN and ARF-MDM2-p53 INK4a-RB pathways in promoting oncogenic capacity. Deregulation of these signalling pathways, among others, drives changes in the glial/stem cell state and environment that permit autonomous growth. The initially transformed cell may undergo subsequent modifications, acquiring a more complete tumour-initiating phenotype responsible for disease advancement to stages that are more aggressive. We recently established that the oncogenic activity of mutant p53 (mtp53) is driven by the actin cytoskeleton-associated protein WIP (WASP-interacting protein), correlated with tumour growth, and more importantly that both proteins are responsible for the tumour-initiating cell phenotype. We reported that WIP knockdown in mtp53-expressing glioblastoma greatly reduced proliferation and growth capacity of cancer stem cell (CSC)-like cells and decreased CSC-like markers, such as hyaluronic acid receptor (CD44), prominin-1 (CD133), yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ). We thus propose a new CSC signalling pathway downstream of mtp53 in which Akt regulates WIP and controls YAP/TAZ stability. WIP drives a mechanism that stimulates growth signals, promoting YAP/TAZ and β-catenin stability in a Hippo-independent fashion, which allows cells to coordinate processes such as proliferation, stemness and invasiveness, which are key factors in cancer progression. Based on this multistep tumourigenic model, it is tantalizing to propose that WIP inhibitors may be applied as an effective anti-cancer therapy.

VEGF-neuropilin-2 signaling promotes stem-like traits in breast cancer cells by TAZ-mediated repression of the Rac GAP β2-chimaerin

The role of vascular endothelial growth factor (VEGF) signaling in cancer is not only well known in the context of angiogenesis but also important in the functional regulation of tumor cells. Autocrine VEGF signaling mediated by its co-receptors called neuropilins (NRPs) appears to be essential for sustaining the proliferation and survival of cancer stem cells (CSCs), which are implicated in mediating tumor growth, progression, and drug resistance. Therefore, understanding the mechanisms involved in VEGF-mediated support of CSCs is critical to successfully treating cancer patients. The expression of the Hippo effector TAZ is associated with breast CSCs and confers stem cell-like properties. We found that VEGF-NRP2 signaling contributed to the activation of TAZ in various breast cancer cells, which mediated a positive feedback loop that promoted mammosphere formation. VEGF-NRP2 signaling activated the GTPase Rac1, which inhibited the Hippo kinase LATS, thus leading to TAZ activity. In a complex with the transcription factor TEAD, TAZ then bound and repressed the promoter of the gene encoding the Rac GTPase-activating protein (Rac GAP) β2-chimaerin. By activating GTP hydrolysis, Rac GAPs effectively turn off Rac signaling; hence, the TAZ-mediated repression of β2-chimaerin resulted in sustained Rac1 activity in CSCs. Depletion of β2-chimaerin in non-CSCs increased Rac1 activity, TAZ abundance, and mammosphere formation. Analysis of a breast cancer patient database revealed an inverse correlation between β2-chimaerin and TAZ expression in tumors. Our findings highlight an unexpected role for β2-chimaerin in a feed-forward loop of TAZ activation and the acquisition of CSC properties.

Upstairs, downstairs: spatial regulation of Hippo signalling

Cellular signalling lies at the heart of every decision involved in the development and homeostasis of multicellular organisms. The Hippo pathway was discovered nearly two decades ago through seminal work in Drosophila and rapidly emerged as a crucial signalling network implicated in developmental and oncogenic growth, tissue regeneration and stem cell biology. Here, we review recent advances in the field relating to the upstream regulation of Hippo signalling and the intracellular tug-of-war that tightly controls its main target, the transcriptional co-activator Yorkie/YAP.

Role of Akt Isoforms Controlling Cancer Stem Cell Survival, Phenotype and Self-Renewal

The cancer stem cell (CSC) hypothesis suggests that tumours are maintained by a subpopulation of cells with stem cell properties. Although the existence of CSCs was initially described in human leukaemia, less evidence exists for CSCs in solid tumours. Recently, a CD133+ cell subpopulation was isolated from human brain tumours exhibiting stem cell properties in vitro as well as the capacity to initiate tumours in vivo. In the present work, we try to summarize the data showing that some elements of the Phosphoinositide 3-kinase Class I (PI3K)/ Thymoma viral oncogene protein kinase (Akt) pathway, such the activity of PI3K Class I or Akt2, are necessary to maintain the CSC-like phenotype as well as survival of CSCs (also denoted as tumour-initiating cells (TICs)). Our data and other laboratory data permit a working hypothesis in which each Akt isoform plays an important and specific role in CSC/TIC growth, self-renewal, maintaining survival, and epithelial-mesenchymal transition (EMT) phenotype, not only in breast cancer, but also in glioma. We suggest that a more complete understanding is needed of the possible roles of isoforms in human tumours (iso-signalling determination). Thus, a comprehensive analysis of how hierarchical signalling is assembled during oncogenesis, how cancer landmarks are interconnected to favour CSC and tumour growth, and how some protein isoforms play a specific role in CSCs to ensure that survival and proliferation must be done in order to propose/generate new therapeutic approaches (alone or in combination with existing ones) to use against cancer.

Crosstalk between WIP and Rho family GTPases

Through actin-binding proteins such as the neural Wiskott-Aldrich syndrome protein (N-WASP) and WASP-interacting protein (WIP), the Rho family GTPases RhoA, Rac1 and Cdc42 are major modulators of the cytoskeleton. (N-)WASP and WIP control Rho GTPase activity in various cell types, either by direct WIP/(N-)WASP/Cdc42 or potential WIP/RhoA binding, or through secondary links that regulate GTPase distribution and/or transcription levels. WIP helps to regulate filopodium generation and participates in the Rac1-mediated ruffle formation that determines cell motility. In neurons, lack of WIP increases dendritic spine size and filamentous actin content in a RhoA-dependent manner. In contrast, WIP deficiency in an adenocarcinoma cell line significantly reduces RhoA levels. These data support a role for WIP in the GTPase-mediated regulation of numerous actin-related cell functions; we discuss the possibility that this WIP effect is linked to cell proliferative status.

Two faces of Hippo: activate or suppress the Hippo pathway in cancer

The Hippo pathway has generated considerable interest in recent years because of its involvement in several key hallmarks of cancer progression and metastasis. Research on the Hippo signaling pathway in cancer has been used to determine the activity of yes-associated protein (YAP) in tumorigenesis and disease progression. Previous studies have shown that the Hippo pathway can be used as a target to inhibit YAP activity and is a viable treatment for cancer. However, more studies are required to further advance our understanding of the Hippo signaling pathway in cancer. It has been shown that knockout of serine/threonine-kinases LATS1/2 in the Hippo pathway suppresses cancer immunity in mice. In addition, suppression of the oncogene YAP could contribute toward cancer immune therapy. Therefore, regulation of Hippo signaling can be an attractive alternative strategy for cancer treatment. This review will provide a summary of currently known compounds that activate or suppress the Hippo pathway.

The Arp2/3 Regulatory System and Its Deregulation in Cancer

The Arp2/3 complex is an evolutionary conserved molecular machine that generates branched actin networks. When activated, the Arp2/3 complex contributes the actin branched junction and thus cross-links the polymerizing actin filaments in a network that exerts a pushing force. The different activators initiate branched actin networks at the cytosolic surface of different cellular membranes to promote their protrusion, movement, or scission in cell migration and membrane traffic. Here we review the structure, function, and regulation of all the direct regulators of the Arp2/3 complex that induce or inhibit the initiation of a branched actin network and that controls the stability of its branched junctions. Our goal is to present recent findings concerning novel inhibitory proteins or the regulation of the actin branched junction and place these in the context of what was previously known to provide a global overview of how the Arp2/3 complex is regulated in human cells. We focus on the human set of Arp2/3 regulators to compare normal Arp2/3 regulation in untransformed cells to the deregulation of the Arp2/3 system observed in patients affected by various cancers. In many cases, these deregulations promote cancer progression and have a direct impact on patient survival.

A TIAM Double Hit to Oppose YAP/TAZ

In this issue of Cancer Cell, Diamantopoulou et al. uncover dual mechanisms of inhibiting YAP/TAZ by TIAM1 that oppose invasiveness of colorectal cancer cells: TIAM1 interacts with TAZ in the cytoplasm to promote TAZ degradation by the destruction complex, whereas it antagonizes binding of TAZ/YAP to TEAD in the nucleus.