Abnormal ezrin localization is associated with clinicopathological features in invasive breast carcinomas

Contribution of radixin and ezrin to the maintenance of hepatocytes' excretory function in health and disease

Background & aims

Excretory liver failure is frequently associated with poor prognosis in critically ill patients. It is characterized by the loss of canalicular membrane export pumps at the hepatocyte membrane. The membrane export pump Multidrug resistant-associated protein (MRP) 2 is pivotal in hepatocytes for brushed membrane morphology and transport of various metabolites. In addition, MRP2 anchoring proteins of the Ezrin/Radixin/Moesin (ERM) family are crucial for the correct MRP2 location, integration, and function in different tissues. In hepatocytes, altered ERM signaling is elementary for developing excretory liver failure.

Methods

Polarized human HepaRG cells, primary human hepatocytes, and hepatocyte-specific Ezrin knockout mice are employed to investigate ERM expression and function in health and the bile duct ligation model of obstructive cholestasis.

Results

ERM-scaffolding protein Ezrin has no relevant function in maintaining the canalicular structure in hepatocytes during health and disease.

Conclusions

Homeostasis of the canalicular pole in hepatocytes is maintained exclusively by Radixin but not Ezrin, and Radixin dysfunction promotes cholestasis.

A retrospective analysis of ezrin protein and mRNA expression in breast cancer: Ezrin expression is associated with patient survival and survival of patients with receptor-positive disease

INTRODUCTION

The cytoskeletal protein ezrin is upregulated in many cancer types and is strongly associated with poor patient outcome. While the clinical and prognostic value of ezrin has been previously evaluated in breast cancer, most studies to date have been conducted in smaller cohorts (less than 500 cases) or have focused on specific disease characteristics. The current study is the largest of its kind to evaluate ezrin both at the protein and mRNA levels in early-stage breast cancer patients using the Nottingham (n = 1094) and METABRIC (n = 1980) cohorts, respectively.

RESULTS

High expression of ezrin was significantly associated with larger tumour size (p = 0.027), higher tumour grade (p < 0.001), worse Nottingham Prognostic Index prognostic group (p = 0.011) and HER2-positive status (p = 0.001). High ezrin expression was significantly associated with adverse survival of breast cancer patients (p < 0.001) and remained associated with survival in multivariate Cox-regression analysis (p = 0.018, hazard ratio (HR) = 1.343, 95% confidence interval (CI) = 1.051-1.716) when potentially confounding factors were included. High ezrin expression was significantly associated with adverse survival of patients whose tumours were categorised as receptor (oestrogen receptor (ER), progesterone receptor (PgR) or HER2) positive (p < 0.001) in comparison to those categorised as triple-negative breast cancer (p = 0.889). High expression of ezrin mRNA (VIL2) in the METABRIC cohort was also significantly associated with adverse survival of breast cancer patients (p < 0.001).

CONCLUSION

Retrospective analyses show that ezrin is an independent prognostic marker, with higher expression associated with shortened survival in receptor-positive (ER, PgR or HER2) patients. Ezrin expression is associated with more aggressive disease and may have clinical utility as a biomarker of patient prognosis in early-stage breast cancer.

Ezrin and Its Phosphorylated Thr567 Form Are Key Regulators of Human Extravillous Trophoblast Motility and Invasion

The protein ezrin has been shown to enhance cancer cell motility and invasion leading to malignant behaviours in solid tumours, but a similar regulatory function in the early physiological reproduction state is, however, much less clear. We speculated that ezrin may play a key role in promoting first-trimester extravillous trophoblast (EVT) migration/invasion. Ezrin, as well as its Thr567 phosphorylation, were found in all trophoblasts studied, whether primary cells or lines. Interestingly, the proteins were seen in a distinct cellular localisation in long, extended protrusions in specific regions of cells. Loss-of-function experiments were carried out in EVT HTR8/SVneo and Swan71, as well as primary cells, using either ezrin siRNAs or the phosphorylation Thr567 inhibitor NSC668394, resulting in significant reductions in both cell motility and cellular invasion, albeit with differences between the cells used. Our analysis further demonstrated that an increase in focal adhesion was, in part, able to explain some of the molecular mechanisms involved. Data collected using human placental sections and protein lysates further showed that ezrin expression was significantly higher during the early stage of placentation and, importantly, clearly seen in the EVT anchoring columns, further supporting the potential role of ezrin in regulating migration and invasion in vivo.

Cytoskeletal and Cytoskeleton-Associated Proteins: Key Regulators of Cancer Stem Cell Properties

Cancer stem cells (CSCs) are a subpopulation of cancer cells possessing stemness characteristics that are closely associated with tumor proliferation, recurrence and resistance to therapy. Recent studies have shown that different cytoskeletal components and remodeling processes have a profound impact on the behavior of CSCs. In this review, we outline the different cytoskeletal components regulating the properties of CSCs and discuss current and ongoing therapeutic strategies targeting the cytoskeleton. Given the many challenges currently faced in targeted cancer therapy, a deeper comprehension of the molecular events involved in the interaction of the cytoskeleton and CSCs will help us identify more effective therapeutic strategies to eliminate CSCs and ultimately improve patient survival.

Ezrin gone rogue in cancer progression and metastasis: An enticing therapeutic target

Cancer metastasis is the primary cause of morbidity and mortality in cancer as it remains the most complicated, devastating, and enigmatic aspect of cancer. Several decades of extensive research have identified several key players closely associated with metastasis. Among these players, cytoskeletal linker Ezrin (the founding member of the ERM (Ezrin-Radixin-Moesin) family) was identified as a critical promoter of metastasis in pediatric cancers in the early 21st century. Ezrin was discovered 40 years ago as a aminor component of intestinal epithelial microvillus core protein, which is enriched in actin-containing cell surface structures. It controls gastric acid secretion and plays diverse physiological roles including maintaining cell polarity, regulating cell adhesion, cell motility and morphogenesis. Extensive research for more than two decades evinces that Ezrin is frequently dysregulated in several human cancers. Overexpression, altered subcellular localization and/or aberrant activation of Ezrin are closely associated with higher metastatic incidence and patient mortality, thereby justifying Ezrin as a valuable prognostic biomarker in cancer. Ezrin plays multifaceted role in multiple aspects of cancer, with its significant contribution in the complex metastatic cascade, through reorganizing the cytoskeleton and deregulating various cellular signaling pathways. Current preclinical studies using genetic and/or pharmacological approaches reveal that inactivation of Ezrin results in significant inhibition of Ezrin-mediated tumor growth and metastasis as well as increase in the sensitivity of cancer cells to various chemotherapeutic drugs. In this review, we discuss the recent advances illuminating the molecular mechanisms responsible for Ezrin dysregulation in cancer and its pleiotropic role in cancer progression and metastasis. We also highlight its potential as a prognostic biomarker and therapeutic target in various cancers. More importantly, we put forward some potential questions, which we strongly believe, will stimulate both basic and translational research to better understand Ezrin-mediated malignancy, ultimately leading to the development of Ezrin-targeted cancer therapy for the betterment of human life.

DPYSL2 interacts with JAK1 to mediate breast cancer cell migration

The intricate neuronal wiring during development requires cytoskeletal reorganization orchestrated by signaling cues. Because cytoskeletal remodeling is a hallmark of cell migration, we investigated whether metastatic cancer cells exploit axon guidance proteins to migrate. Indeed, in breast cancer patients, we found a significant correlation between mesenchymal markers and the expression of dihydropyrimidinase-like 2 (DPYSL2), a regulator of cytoskeletal dynamics in growing axons. Strikingly, DPYSL2 knockout in mesenchymal-like breast cancer cells profoundly inhibited cell migration, invasion, stemness features, tumor growth rate, and metastasis. Next, we decoded the molecular mechanism underlying this phenomenon and revealed an interaction between DPYSL2 and Janus kinase 1 (JAK1). This binding is crucial for activating signal transducer and activator of transcription 3 (STAT3) and the subsequent expression of vimentin, the promigratory intermediate filament. These findings identify DPYSL2 as a molecular link between oncogenic signaling pathways and cytoskeletal reorganization in migrating breast cancer cells.

Expression Patterns of Ezrin and AJAP1 and Clinical Significance in Breast Cancer

Ezrin and adherens junction-associated protein 1 (AJAP1) are structural proteins which are involved in numerous human malignancies. However, little is known about the relationship between them in breast cancer. This study was set out to investigate the relationship between them and to further explore the mechanism of AJAP1-mediating cytoskeleton in breast cancer progression. Ezrin and AJAP1 expressions were detected in 377 samples of breast cancer by immunohistochemistry, and different expression patterns between AJAP1 and Ezrin with clinicopathological parameters were analyzed. Besides, univariate and multivariate Cox models were used to evaluate their prognostic potential. Enzyme-linked immunosorbent assay, Western blot, qRT-PCR, and phalloidin staining of F-actin were used to explore the relationship and the mechanism between AJAP1 and Ezrin in cytoskeleton arrangement. 377 cases of breast cancer results showed that AJAP1 expression was negatively related with histological grade and lymph node involvement and could be an independent prognosis marker of breast cancer. AJAP1 expression tended to be higher in the Ezrin-negative expression case. Patients with AJAP1^negative and Ezrin^positive expression had a worse prognosis (p < 0.0001) and shorter DFS (p = 0.015). More importantly, AJAP1 depletion increased the cell ability of F-actin formation through promoting Ezrin expression. AJAP1 depletion might mediate breast cancer malignancy potential through promoting Ezrin expression and cytoskeleton formation.

Homeostatic membrane tension constrains cancer cell dissemination by counteracting BAR protein assembly

Malignancy is associated with changes in cell mechanics that contribute to extensive cell deformation required for metastatic dissemination. We hypothesized that the cell-intrinsic physical factors that maintain epithelial cell mechanics could function as tumor suppressors. Here we show, using optical tweezers, genetic interference, mechanical perturbations, and in vivo studies, that epithelial cells maintain higher plasma membrane (PM) tension than their metastatic counterparts and that high PM tension potently inhibits cancer cell migration and invasion by counteracting membrane curvature sensing/generating BAR family proteins. This tensional homeostasis is achieved by membrane-to-cortex attachment (MCA) regulated by ERM proteins, whose disruption spontaneously transforms epithelial cells into a mesenchymal migratory phenotype powered by BAR proteins. Consistently, the forced expression of epithelial–mesenchymal transition (EMT)-inducing transcription factors results in decreased PM tension. In metastatic cells, increasing PM tension by manipulating MCA is sufficient to suppress both mesenchymal and amoeboid 3D migration, tumor invasion, and metastasis by compromising membrane-mediated mechanosignaling by BAR proteins, thereby uncovering a previously undescribed mechanical tumor suppressor mechanism.

Changes in cell mechanics contribute to cancer cell dissemination. Here the authors show that high plasma membrane (PM) tension inhibits cancer dissemination by counteracting mechanosensitive BAR family protein assembly, while restoration of PM tension phenotypically convert malignant cells into a non-motile epithelial cell state.

EZR promotes pancreatic cancer proliferation and metastasis by activating FAK/AKT signaling pathway

Background

As a member of the ERM (ezrin-radixin-moesin) protein family, EZR has been recognized as a regulator of adhesion signal pathways by researchers. Moreover, EZR was thought to play irreplaceable roles in invasion and metastasis of versatile cancers. In this study, we managed to undermine the effect of EZR on proliferation and metastasis in pancreatic cancer (PC).

Methods

To analyze the impact of EZR expression on overall survival and free diseases survival of PC patients, we screened abnormally expressed EZR in PC using the Gene Expression Omnibus database (GEO database) and The Cancer Genome Atlas (TCGA) database. Following, Gene Ontology (GO)-based functional analysis and Gene set enrichment analysis (GSEA) was performed to predicate the possible biological processes in which EZR were involved. The clinicopathological characteristics and prognosis of PC patients were analyzed according to clinical data. Further, immunohistochemistry, western blotting and real time PCR analysis were conducted to analyze the expression level of EZR in PC and paired paracancerous tissues. The effect of EZR on proliferation of PC cell lines were detected by Cell Counting Kit-8 assay, and meanwhile, Transwell assay was performed to detect the effect of EZR on invasion and migration of PC cell.

Result

EZR exhibited higher expression level in pancreatic cancer tissues and cell than paracancerous tissues and cell, and its expression level was positively correlated with poor overall survival and diseases-free survival in PC patients. CCK8 assay indicated that EZR facilitated the proliferation of PC cells, meanwhile, Transwell assay showed that EZR promoted the migration and invasion of PC cells. The GO analysis predicated that EZR was involved in biological processes including cell adhesion, ameboidal-type cell migration, cell junction assembly. Through GSEA analysis, pancreatic cancer pathway, and the adhesion junction pathway were screened as the mostly enriched pathways in EZR-regulated pathological process. The inhibition of EZR suppressed proliferation and migration of PC cells. Western blot experiment revealed a positive correlation between EZR and FAK, the proliferation invasion and migration ability of PC cells were significantly decreased after knockdown of EZR.

Conclusion

Our finding revealed EZR accelerated the progression of PC via FAK/AKT signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02222-1.

Acetylation of ezrin regulates membrane-cytoskeleton interaction underlying CCL18-elicited cell migration

Ezrin, a membrane–cytoskeleton linker protein, plays an essential role in cell polarity establishment, cell migration, and division. Recent studies show that ezrin phosphorylation regulates breast cancer metastasis by promoting cancer cell survivor and promotes intrahepatic metastasis via cell migration. However, it was less characterized whether there are additional post-translational modifications and/or post-translational crosstalks on ezrin underlying context-dependent breast cancer cell migration and invasion. Here we show that ezrin is acetylated by p300/CBP-associated factor (PCAF) in breast cancer cells in response to CCL18 stimulation. Ezrin physically interacts with PCAF and is a cognate substrate of PCAF. The acetylation site of ezrin was mapped by mass spectrometric analyses, and dynamic acetylation of ezrin is essential for CCL18-induced breast cancer cell migration and invasion. Mechanistically, the acetylation reduced the lipid-binding activity of ezrin to ensure a robust and dynamic cycling between the plasma membrane and cytosol in response to CCL18 stimulation. Biochemical analyses show that ezrin acetylation prevents the phosphorylation of Thr567. Using atomic force microscopic measurements, our study revealed that acetylation of ezrin induced its unfolding into a dominant structure, which prevents ezrin phosphorylation at Thr567. Thus, these results present a previously undefined mechanism by which CCL18-elicited crosstalks between the acetylation and phosphorylation on ezrin control breast cancer cell migration and invasion. This suggests that targeting PCAF signaling could be a potential therapeutic strategy for combating hyperactive ezrin-driven cancer progression.

Regulatory roles of claudin-1 in cell adhesion and microvilli formation

Aberrant expression of tight junction proteins has recently been focused on in the cancer research field. We previously showed that claudin-1 is aberrantly expressed from an early stage of uterine cervical adenocarcinoma and contributes to malignant potentials. To elucidate the molecular mechanisms underlying tumor-promoting roles of claudin-1, we established and analyzed claudin-1 knockout cells. Knockout of claudin-1 suppressed conventional tight junctional functions, barrier and fence functions, and expression of cell adhesion-associated proteins including E-cadherin. Comparative proteome analysis revealed that expression of claudin-1 affected expression of a wide range of proteins, especially proteins that are associated with cell adhesion and actin cytoskeleton remodeling. Interactome analysis of the identified proteins revealed that E-cadherin and focal adhesion kinase play central roles in the claudin-1-dependently affected protein network. Moreover, knockout of claudin-1 significantly suppressed microvilli formation and activity of Ezrin/Radixin/Moesin. Taken together, the results indicate that expression of claudin-1 affects not only conventional tight junction function but also expression and activity of a wide range of proteins, especially proteins that are associated with cell adhesion and actin cytoskeleton remodeling, to contribute to malignant potentials and microvilli formation in cervical adenocarcinoma cells.

Cytoskeletal Remodeling in Cancer

Simple Summary

Cell migration is an essential process from embryogenesis to cell death. This is tightly regulated by numerous proteins that help in proper functioning of the cell. In diseases like cancer, this process is deregulated and helps in the dissemination of tumor cells from the primary site to secondary sites initiating the process of metastasis. For metastasis to be efficient, cytoskeletal components like actin, myosin, and intermediate filaments and their associated proteins should co-ordinate in an orderly fashion leading to the formation of many cellular protrusions-like lamellipodia and filopodia and invadopodia. Knowledge of this process is the key to control metastasis of cancer cells that leads to death in 90% of the patients. The focus of this review is giving an overall understanding of these process, concentrating on the changes in protein association and regulation and how the tumor cells use it to their advantage. Since the expression of cytoskeletal proteins can be directly related to the degree of malignancy, knowledge about these proteins will provide powerful tools to improve both cancer prognosis and treatment.

Abstract

Successful metastasis depends on cell invasion, migration, host immune escape, extravasation, and angiogenesis. The process of cell invasion and migration relies on the dynamic changes taking place in the cytoskeletal components; actin, tubulin and intermediate filaments. This is possible due to the plasticity of the cytoskeleton and coordinated action of all the three, is crucial for the process of metastasis from the primary site. Changes in cellular architecture by internal clues will affect the cell functions leading to the formation of different protrusions like lamellipodia, filopodia, and invadopodia that help in cell migration eventually leading to metastasis, which is life threatening than the formation of neoplasms. Understanding the signaling mechanisms involved, will give a better insight of the changes during metastasis, which will eventually help targeting proteins for treatment resulting in reduced mortality and longer survival.

Bidirectional Tumor-Promoting Activities of Macrophage Ezrin

Ezrin links the cytoskeleton to cell surface integrins and plasma membrane receptors, contributing to the proliferative and metastatic potential of cancer cells. Elevated ezrin expression in several cancers is associated with poor outcomes. Tumor cell ezrin expression and function have been investigated in depth; however, its role in macrophages and other tumor microenvironment cells remains unexplored. Macrophages profoundly influence tumorigenesis, and here we explore ezrin’s influence on tumor-promoting macrophage functions. Ezrin knockdown in THP-1 macrophages reveals its important contribution to adhesion to endothelial cells. Unexpectedly, ezrin is essential for the basal and breast cancer cell-stimulated THP-1 expression of ITGAM mRNA that encodes integrin CD11b, critical for cell adhesion. Ezrin skews the differentiation of THP-1 macrophages towards the pro-tumorigenic, M2 subtype, as shown by the reduced expression of FN1, IL10, and CCL22 mRNAs following ezrin knockdown. Additionally, macrophage ezrin contributes to the secretion of factors that stimulate tumor cell migration, invasion, and clonogenic growth. Lastly, THP-1 ezrin is critical for the expression of mRNAs encoding vascular endothelial growth factor (VEGF)-A and matrix metalloproteinase (MMP)-9, consistent with pro-tumorigenic function. Collectively, our results provide insight into ezrin’s role in tumorigenesis, revealing a bidirectional interaction between tumor-associated macrophages and tumor cells, and suggest myeloid cell ezrin as a target for therapeutic intervention against cancer.

Biological behaviour and ezrin expression in canine rhabdomyosarcomas: 25 cases (1990-2012)

There are few published reports of canine rhabdomyosarcomas. In human paediatrics, rhabdomyosarcomas account for 5%-10% of all tumours and >50% of soft tissue sarcomas. They have an aggressive biologic behaviour; most patients develop diffuse metastatic disease. Ezrin, a cytoskeleton linker protein, has been correlated with metastasis in a number of tumours, including rhabdomyosarcomas. The goal of this study was to describe dogs with non-urinary rhabdomyosarcomas including clinical findings, ezrin expression and outcome. Twenty-five dogs with rhabdomyosarcomas were identified from two institutions' databases. Signalment, primary tumour location, cytologic and histologic findings, metastatic sites, treatments, survival time and necropsy results were recorded. Immunohistochemical staining for ezrin expression was performed on archived samples; cellular localization of ezrin was characterized. The mean and median age of all patients was 4.3 and 2 years, respectively. Subcutaneous and retrobulbar/orbital were the most common primary tumour locations. Sixteen dogs had metastatic disease at diagnosis. Three dogs presented with diffuse disease where a primary tumour could not be identified. A round cell tumour was the initial diagnosis in 32% of cases, and 76% of cases required immunohistochemistry to establish the diagnosis. The median survival was 10 days. Twenty-one cases had archived samples available for ezrin staining; all but one was positive and exhibited both membranous and cytoplasmic localization. Rhabdomyosarcomas occur in young dogs, may have a round cell appearance, and exhibit aggressive biologic behaviour. Given ezrin's defined role in metastasis, its observed expression in the tumours in this study suggest its possible role in canine rhabdomyosarcoma's aggressive biologic behaviour.

A-Kinase Anchoring Proteins Diminish TGF-β1/Cigarette Smoke-Induced Epithelial-To-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) plays a role in chronic obstructive pulmonary diseases (COPD). Cyclic adenosine monophosphate (cAMP) can inhibit transforming growth factor-β1 (TGF-β1) mediated EMT. Although compartmentalization via A-kinase anchoring proteins (AKAPs) is central to cAMP signaling, functional studies regarding their therapeutic value in the lung EMT process are lacking. The human bronchial epithelial cell line (BEAS-2B) and primary human airway epithelial (pHAE) cells were exposed to TGF-β1. Epithelial (E-cadherin, ZO-1) and mesenchymal markers (collagen Ӏ, α-SMA, fibronectin) were analyzed (mRNA, protein). ELISA measured TGF-β1 release. TGF-β1-sensitive AKAPs Ezrin, AKAP95 and Yotiao were silenced while using siRNA. Cell migration was analyzed by wound healing assay, xCELLigence, Incucyte. Prior to TGF-β1, dibutyryl-cAMP (dbcAMP), fenoterol, rolipram, cilostamide, and forskolin were used to elevate intracellular cAMP. TGF-β1 induced morphological changes, decreased E-cadherin, but increased collagen Ӏ and cell migration, a process that was reversed by the inhibitor of δ/epsilon casein kinase I, PF-670462. TGF-β1 altered (mRNA, protein) expression of Ezrin, AKAP95, and Yotiao. St-Ht31, the AKAP antagonist, decreased E-cadherin (mRNA, protein), but counteracted TGF-β1-induced collagen Ӏ upregulation. Cigarette smoke (CS) increased TGF-β1 release, activated TGF signaling, augmented cell migration, and reduced E-cadherin expression, a process that was blocked by TGF-β1 neutralizing antibody. The silencing of Ezrin, AKAP95, and Yotiao diminished TGF-β1-induced collagen Ӏ expression, as well as TGF-β1-induced cell migration. Fenoterol, rolipram, and cilostamide, in AKAP silenced cells, pointed to distinct cAMP compartments. We conclude that Ezrin, AKAP95, and Yotiao promote TGF-β1-mediated EMT, linked to a TGF-β1 release by CS. AKAP members might define the ability of fenoterol, rolipram, and cilostamide to modulate the EMT process, and they might represent potential relevant targets in the treatment of COPD.

High expression of EZR (ezrin) gene is correlated with the poor overall survival of breast cancer patients

Background

To evaluate the EZR (ezrin) gene expression in breast cancer and correlation with the prognosis through bioinformatics analysis and immunohistochemistry assay.

Methods

EZR gene expression in breast cancer and corresponding normal breast tissue was compared in the TCGA database. Protein‐protein interaction (PPI) network relevant EZR was established through the STRING database. The correlation between EZR expression and prognosis of breast cancer was analyzed by the log‐rank analysis from the TCGA. Ezrin protein (coded by EZR) expression was also examined by immunohistochemistry assay in 120 breast cancer patients.

Results

EZR expression level in tumor tissue was significantly upregulated compared to that of normal breast tissue of breast cancer patients (P < 0.05). In the PPI analysis, there were 51 nodes and 455 edges in the network. The top 10 hub genes of the network were identified. High expression of EZR mRNA was correlated with poor overall survival (OS) of the breast cancer patients (HR = 1.40, P = 0.038). However, the disease‐free survival (DFS) of breast cancer patients did not correlate with the EZR mRNA level (HR = 0.86, P = 0.44). The ezrin protein expression was positive with uniform brown‐yellow granules in the cell membrane, cavity surface and cytoplasm of the breast cancer cells. Of the included 120 cancer samples, 98 cases were positive for ezrin expression and 22 were negative. No correlation was found between ezrin expression site and patients’ clinicopathological features.

Conclusion

EZR is upregulated in breast cancer and can be used as potential biomarker for overall survival.

IgG based immunome analyses of breast cancer patients reveal underlying signaling pathways

Background: Breast cancer is the most frequent and one of the most fatal malignancies among women. Within the concept of personalized medicine, molecular characterization of tumors is usually performed by analyzing somatic mutations, RNA gene expression signatures or the proteome by mass-spectrometry. Alternatively, the immunological fingerprint of the patients can be analyzed by protein microarrays, which is able to provide another layer of molecular pathological information without invasive intervention.

Results: We have investigated the immune signature of breast cancer patients and compared them with healthy controls, using protein microarray-based IgG profiling. The identified differentially reactive antigens (n=517) were further evaluated by means of various pathway analysis tools. Our results indicate that the immune signature of breast cancer patients shows a clear distinction from healthy individuals characterized by differentially reactive antigens involved in known disease relevant signaling pathways, such as VEGF, AKT/PI3K/mTOR or c-KIT, which is in close agreement with the findings from RNA-based expression profiles.

Conclusion: Differential antigenic properties between breast cancer patients and healthy individual classes can be defined by serum-IgG profiling on protein microarrays. These immunome profiles provide an additional layer of molecular pathological information, which has the potential to refine and complete the systems biological map of neoplastic disease.

UBA6 and Its Bispecific Pathways for Ubiquitin and FAT10

Questions have been raised since the discovery of UBA6 and its significant coexistence with UBE1 in the ubiquitin–proteasome system (UPS). The facts that UBA6 has the dedicated E2 enzyme USE1 and the E1–E2 cascade can activate and transfer both ubiquitin and ubiquitin-like protein FAT10 have attracted a great deal of attention to the regulational mechanisms of the UBA6–USE1 cascade and to how FAT10 and ubiquitin differentiate with each other. This review recapitulates the latest advances in UBA6 and its bispecific UBA6–USE1 pathways for both ubiquitin and FAT10. The intricate networks of UBA6 and its interplays with ubiquitin and FAT10 are briefly reviewed, as are their individual and collective functions in diverse physiological conditions.

Bisphenol S increases EZRIN expression and the detrimental effects induced by dehydroepiandrosterone in rat endometrium

The use of Bisphenol S (BPS) was proposed as an alternative to Bisphenol A (BPA), a chemical employed in the production of polycarbonate plastics and epoxy resins. BPA is a xenoestrogen that affects normal physiology in several species. It was reported that BPS may also act as a xenoestrogen with harmful effects in the reproductive system. Here we studied the effects of BPS during the induction of a polycystic ovarian syndrome (PCOS)-like condition in rats. Animals were injected daily with vehicle, DHEA 60 mg/kg, BPS 1 μg/kg and DHEA-BPS, for 20 days. Cell apoptosis, cell proliferation, and EZRIN expression were analyzed by immunohistochemistry. We found an increase in PCNA expression, which correlates with cytoplasmic accumulation of the polarization marker, EZRIN, in the BPS treated groups. Additionally, the administration of BPS in the DHEA treated group augmented the stratification and number of "intraepithelial lumina" in the endometrial surface epithelium.

Inhibition of ezrin causes PKCα-mediated internalization of erbb2/HER2 tyrosine kinase in breast cancer cells

Unlike other ErbB family members, HER2 levels are maintained on the cell surface when the receptor is activated, allowing prolonged signaling and contributing to its transforming ability. Interactions between HER2, HSP90, PMCA2, and NHERF1 within specialized plasma membrane domains contribute to the membrane retention of HER2. We hypothesized that the scaffolding protein ezrin, which has been shown to interact with NHERF1, might also help stabilize the HER2-PMCA2-NHERF1 complex at the plasma membrane. Therefore, we examined ezrin expression and its relationship with HER2, NHERF1, and PMCA2 levels in murine and human breast cancers. We also used genetic knockdown and/or pharmacologic inhibition of ezrin, HSP90, NHERF1, PMCA2, and HER2 to examine the functional relationships between these factors and membrane retention of HER2. We found ezrin to be expressed at low levels at the apical surface of normal mammary epithelial cells, but its expression is up-regulated and correlates with HER2 expression in hyperplasia and tumors in murine mammary tumor virus-Neu mice, in human HER2-positive breast cancer cell lines, and in ductal carcinoma in situ and invasive breast cancers from human patients. In breast cancer cells, ezrin co-localizes and interacts with HER2, NHERF1, PMCA2, and HSP90 in specialized membrane domains, and inhibiting ezrin disrupts interactions between HER2, PMCA2, NHERF1, and HSP90, inhibiting HER2 signaling and causing PKCα-mediated internalization and degradation of HER2. Inhibition of ezrin synergizes with lapatinib in a PKCα-dependent fashion to inhibit proliferation and promote apoptosis in HER2-positive breast cancer cells. We conclude that ezrin stabilizes a multiprotein complex that maintains active HER2 at the cell surface.

S100P and Ezrin promote trans-endothelial migration of triple negative breast cancer cells

PURPOSE

Triple negative breast cancer (TNBC) patients generally have an adverse clinical outcome because their tumors often recur and metastasize to distant sites in the first 3 years after surgery. Therefore, it has become pivotal to identify potential factors associated with metastasis. Here, we focused on the effects of S100P and Ezrin on the trans-endothelial migration (TEM) of TNBC cells, as they have both been suggested to play a role in this process in other malignancies.

METHODS

The expression of S100P and Ezrin was examined by immunohistochemistry in 58 primary TNBC samples. The mRNA and protein levels of S100P and Ezrin were assessed in breast cancer-derived cell lines using qRT-PCR and Western blotting, respectively. Proliferation and migration assays were performed using TNBC-derived MFM-223 and SUM-185-PE cells transfected with S100P and Ezrin siRNAs. Two different timeframes were employed for TEM assays using TNBC-derived cells and human umbilical vein endothelial-derived cells, respectively. Correlations between the status of Ezrin^Thr-567 expression and various clinicopathological features were analyzed by immunohistochemistry.

RESULTS

We found that S100P and Ezrin double negative TNBC cases were significantly associated with a better disease-free survival. We also found that single and double siRNA-mediated knockdown of S100P and Ezrin in TNBC-derived cells significantly inhibited their TEM and destabilized the intercellular junctions of endothelial cells. In addition, we found that Ezrin^Thr-567 immunoreactivity significantly correlated with vascular invasion in TNBC patients.

CONCLUSIONS

From our data we conclude that S100P, Ezrin and Ezrin^Thr-567 are involved in the trans-endothelial migration of TNBC cells and that they may serve as potential targets in TNBC patients.

Distinct Ezrin Truncations Differentiate Metastases in Sentinel Lymph Nodes from Unaffected Lymph Node Tissues, from Primary Breast Tumors, and from Healthy Glandular Breast Tissues

BACKGROUND

Lymph node metastasis status is a prognostic factor for further lymph node involvement and for patient survival in breast cancer patients. Frozen section analysis of lymph nodes is a reliable method for detection of macro-metastases. However, this method is far less effective in detecting micro-metastases, requesting improved diagnostic procedures.

METHODS

We investigated expression and truncation of ezrin in (i) sentinel lymph node metastases, (ii) unaffected axillary lymph nodes, (iii) primary breast tumors, and (iv) healthy glandular breast tissues using 2D gel electrophoresis, SDS-PAGE, and mass spectrometry in addition to Western blotting.

RESULTS

Full-length ezrin (E1; amino acids 1-586) is present in all four investigated tissues. Two truncated ezrin forms, one missing about the first hundred amino acids (E2a) and the other lacking about 150 C-terminal amino acids (E2b) were detectable in primary tumor tissues and in sentinel lymph node metastases but not in glandular tissues. Strikingly, an ezrin truncation (E3) which consists approximately of amino acids 238-586 was found strongly expressed in all sentinel lymph node metastases. Moreover, an N-terminal ezrin fragment (E4) that consists approximately of amino acids 1-273 was identified in sentinel lymph node metastases as well.

CONCLUSIONS

We show for the first time the existence of tissue-dependent specific ezrin truncations. The distinguished strong Western blot staining of ezrin E3 in sentinel lymph node metastases underlines its capability to substantiate the occurrence of lymph node (micro)metastases in breast cancer patients.

LPA-induced migration of ovarian cancer cells requires activation of ERM proteins via LPA1 and LPA2

Lysophosphatidic acid (LPA) has been implicated in the pathology of human ovarian cancer. This phospholipid elicits a wide range of cancer cell responses, such as proliferation, trans-differentiation, migration, and invasion, via various G-protein-coupled LPA receptors (LPARs). Here, we explored the cellular signaling pathway via which LPA induces migration of ovarian cancer cells. LPA induced robust phosphorylation of ezrin/radixin/moesin (ERM) proteins, which are membrane-cytoskeleton linkers, in the ovarian cancer cell line OVCAR-3. Among the LPAR subtypes expressed in these cells, LPA₁ and LPA₂, but not LPA₃, induced phosphorylation of ERM proteins at their C-termini. This phosphorylation was dependent on the Gα_12/13/RhoA pathway, but not on the Gα_q/Ca²⁺/PKC or Gα_s/adenylate cyclase/PKA pathway. The activated ERM proteins mediated cytoskeletal reorganization and formation of membrane protrusions in OVCAR-3 cells. Importantly, LPA-induced migration of OVCAR-3 cells was completely abolished not only by gene silencing of LPA₁ or LPA₂, but also by overexpression of a dominant negative ezrin mutant (ezrin-T567A). Taken together, this study demonstrates that the LPA₁/LPA₂/ERM pathway mediates LPA-induced migration of ovarian cancer cells. These findings may provide a potential therapeutic target to prevent metastatic progression of ovarian cancer.

Regulation of ErbB2 localization and function in breast cancer cells by ERM proteins

The ERM protein family is implicated in processes such as signal transduction, protein trafficking, cell proliferation and migration. Consequently, dysregulation of ERM proteins has been described to correlate with carcinogenesis of different cancer types. However, the underlying mechanisms are poorly understood. Here, we demonstrate a novel functional interaction between ERM proteins and the ErbB2 receptor tyrosine kinase in breast cancer cells. We show that the ERM proteins ezrin and radixin are associated with ErbB2 receptors at the plasma membrane, and depletion or functional inhibition of ERM proteins destabilizes the interaction of ErbB2 with ErbB3, Hsp90 and Ebp50. Accompanied by the dissociation of this protein complex, binding of ErbB2 to the ubiquitin-ligase c-Cbl is increased, and ErbB2 becomes dephosphorylated, ubiquitinated and internalized. Furthermore, signaling via Akt- and Erk-mediated pathways is impaired upon ERM inhibition. Finally, interference with ERM functionality leads to receptor degradation and reduced cellular levels of ErbB2 and ErbB3 receptors in breast cancer cells.

Ezrin as a possible diagnostic and/or prognostic biomarker in mice lymphatic metastatic hepatocellular carcinoma in vivo

Hepatocellular carcinoma (HCC) ranks in the top of cancers leading to death. Early diagnosis is the big challenge in the case of HCC. Our in vitro study showed that Ezrin expression in lymphatic metastasis hepatocellular carcinoma (LNM-HCC) was associated with the metastatic rate. Here we aim to evaluate Ezrin expression as diagnostic and/or prognostic biomarker of LNM-HCC in mice. Chinese inbred 615 mice, Hca-F and Hca-P cell lines were used in the study. Histological changes were determined by Hematoxylin and Eosin, while Ezrin expression was assessed by qRT-PCR, western blot, immunohistochemistry, and enzyme-linked immunosorbent assay. Ezrin expression in this study gives credit to our in vitro study which Ezrin expression was positively correlated with LNM-HCC and negatively with Annexin7 (A7) expression. The highest histological changes were observed in high metastatic primary/secondary tumors combined with high Ezrin expression. Ezrin and A7 are higher in total primary tumors than in total secondary tumors (P = 0.0001, P = 0.021), respectively. Ezrin expression was enhanced in Hca-P A7 down-regulated primary/secondary tumors (P = 0.004), whereas, Ezrin expression was suppressed in Hca-F A7 upregulated primary/secondary tumors. Serum ELISA indicated differential expression of Ezrin among the study groups (P ≤ 0.0001). Ezrin expression was higher in NC-Hca-F than NC-Hca-P (P ≤ 0.0001), suppressed in Hca-F A7 upregulation (P ≤ 0.0001) and in enhanced in Hca-P A7 down-regulation (P = 0.0001). In conclusion, Ezrin level may serve as a differential diagnostic and/or prognostic biomarker for high and low LNM-HCC and may be beneficial in the diagnosis of HCC disease. © 2017 BioFactors, 43(5):662-672, 2017.

Ezrin is Significantly Overexpressed in Luminal A, Luminal B, and HER2 Subtype Breast Cancer

Ezrin, a membrane-linking protein, has been shown to play an important role in the carcinogenesis of infiltrating breast ductal carcinoma and its strong expression has been used to predict poor prognosis in patients with breast carcinoma. In this study, we compared ezrin protein distribution pattern in benign breast disease and breast cancer molecular subtypes and evaluated their association with clinicopathologic variables. A total of 376 breast cases (142 benign and 234 malignant cases) were studied. Immunohistochemical analysis for ezrin was performed and its expression was observed in terms of its distribution, intensity, and proportion of cells reactive for ezrin. Ezrin was expressed in all benign cases and 91.7% of malignant cases. Apical staining was positively associated with benign breast disease, whereas membranous and cytoplasmic staining were more frequently observed in malignant cases, specifically of hormone receptor-positive subtypes (luminal A and luminal B). Ezrin was significantly overexpressed in luminal A, luminal B, and HER2 subtypes. Reduced ezrin expression was significantly associated with triple-negative breast cancer molecular subtype. No significant association was demonstrated between ezrin expression and Her2 gene amplification, tumor grading, or staging.

A decision tree-based combination of ezrin-interacting proteins to estimate the prognostic risk of patients with esophageal squamous cell carcinoma

Our previous studies have highlighted the importance of ezrin in esophageal squamous cell carcinoma (ESCC). Here our objective was to explore the clinical significance of ezrin-interacting proteins, which would provide a theoretical basis for understanding the function of ezrin and potential therapeutic targets for ESCC. We used affinity purification and mass spectrometry to identify PDIA3, CNPY2, and STMN1 as potential ezrin-interacting proteins. Confocal microscopy and coimmunoprecipitation analysis further confirmed the colocalization and interaction of ezrin with PDIA3, CNPY2, and STMN1. Tissue microarray data of ESCC samples (n=263) showed that the 5-year overall survival (OS) and disease-free survival (DFS) were significantly lower for the CNPY2 (OS, P=.003; DFS, P=.011) and STMN1 (OS, P=.010; DFS, P=.002) high-expression groups compared with the low-expression groups. By contrast, overexpression of PDIA3 was significantly correlated with favorable survival (OS, P<.001; DFS, P=.001). Cox regression demonstrated the prognostic value of PDIA3, CNPY2, and STMN1 in ESCC. Furthermore, decision tree analysis revealed that the resulting classifier of both ezrin and its interacting proteins could be used to better predict OS and DFS of patients with ESCC. In conclusion, a signature of ezrin-interacting proteins accurately predicts ESCC patient survival or tumor recurrence.

Dynamic relocalization of NHERF1 mediates chemotactic migration of ovarian cancer cells toward lysophosphatidic acid stimulation

NHERF1/EBP50 (Na⁺/H⁺ exchanger regulating factor 1; Ezrin-binding phosphoprotein of 50 kDa) organizes stable protein complexes beneath the apical membrane of polar epithelial cells. By contrast, in cancer cells without any fixed polarity, NHERF1 often localizes in the cytoplasm. The regulation of cytoplasmic NHERF1 and its role in cancer progression remain unclear. In this study, we found that, upon lysophosphatidic acid (LPA) stimulation, cytoplasmic NHERF1 rapidly translocated to the plasma membrane, and subsequently to cortical protrusion structures, of ovarian cancer cells. This movement depended on direct binding of NHERF1 to C-terminally phosphorylated ERM proteins (cpERMs). Moreover, NHERF1 depletion downregulated cpERMs and further impaired cpERM-dependent remodeling of the cell cortex, suggesting reciprocal regulation between these proteins. The LPA-induced protein complex was highly enriched in migratory pseudopodia, whose formation was impaired by overexpression of NHERF1 truncation mutants. Consistent with this, NHERF1 depletion in various types of cancer cells abolished chemotactic cell migration toward a LPA gradient. Taken together, our findings suggest that the high dynamics of cytosolic NHERF1 provide cancer cells with a means of controlling chemotactic migration. This capacity is likely to be essential for ovarian cancer progression in tumor microenvironments containing LPA.

Expression of ezrin and moesin in primary breast carcinoma and matched lymph node metastases

Ezrin, radixin, moesin (ERM) are important membrane-cytoskeletal crosslinkers and are suggested to play important role in cancer progression and metastasis. Even though ERM proteins were generally considered to be functionally redundant and the most studied was ezrin, recent studies highlight their distinct roles in metastatic process. Little information is available regarding the role of individual ERM proteins and their phosphorylated forms in human breast cancer. Our study is the first to examine expression of ezrin, moesin and their phosphorylated forms in primary breast tumors and matched lymph node metastases (LNMs) and their correlation with clinicopathological variables. A total of 88 primary breast cancer, 91 LNMs, 54 intraductal carcinoma and 26 normal adjacent breast tissue samples from tissue microarrays were studied. Expression was determined by immunohistochemistry, the intensity and number of positive cells was scored. Statistical analysis of protein expression and patients' age, tumor grade and hormonal status was performed. No statistical significant difference was found in ezrin, moesin, p-ezrinTyr353 and pan-p-ezrinThr567/radixinThr564/moesinThr558 expression between primary tumors and LNMs. Even though it was not significant, moesin expression varied between primary tumors, intraductal carcinoma, normal breast adjacent tissue and LNMs. A significant positive correlation between moesin and tumor grade has been proven. Even though primary tumors and matched LNMs did not show different expression patterns, moesin correlated significantly with higher tumor grade. Its positivity in intraductal carcinoma and normal breast tissue adjacent to cancer might indicate its role in tumor intiation/progression.

The Prognostic Role of Ezrin and HER2/neu Expression in Osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor in Egypt. Ezrin is involved in cell adhesion to the extracellular matrix and in cell-cell interactions facilitating metastasis. HER2/neu is overexpressed in breast cancer and other types of cancer. This study aimed to assess the expression of ezrin and HER2/neu in 57 primary osteosarcoma cases and to correlate their expression with the available clinicopathologic parameters and the overall, metastasis-free and event-free survival. Both ezrin and HER2/neu were not expressed in the normal bone and they were upregulated in 82.5% and 71.9% of osteosarcoma, respectively. Positive ezrin expression was significantly associated with young age (below 25 y) (P=0.01), high grade (P=0.001), and short survival time (P=0.0001). Positive HER2/neu expression was significantly associated with high-grade osteosarcoma (P=0.04). Membranous HER2/neu expression was the only factor that showed significant impact on metastasis-free (P=0.002) and event-free survival (P=0.002). Ezrin was significantly correlated with HER2/neu expression (P=0.02). Advanced stage (P=0.0001), metastasis (P=0.0001), and recurrence (P=0.01) were the factors affecting the overall survival of osteosarcoma patients. Ezrin and HER2/neu are overexpressed and coexpressed in osteosarcoma with adverse prognostic features such as high grade. Membranous pattern of HER2/neu seems to be more important than the cytoplasmic pattern because of its impact on metastasis-free and event-free survival. Therefore, ezrin and HER2/neu could be potential prognostic markers and treatment targets for osteosarcoma.

Concomitant expression of ezrin and HER2 predicts distant metastasis and poor prognosis of patients with salivary gland carcinomas

Salivary gland carcinomas (SGCs) exhibit heterogeneous biological behaviors, including the formation of distant metastases, which is a critical event associated with poor prognosis. Ezrin, which is a member of the ezrin-radixin-moesin family of plasma membrane-cytoskeleton linker proteins, may provide a marker for metastasis and poor survival of patients with cancer. The aim of the present study was to investigate the relationship between ezrin expression and the expression of HER2, p53, and Ki-67 as well as clinicopathological factors in SGCs. For this purpose, we used immunohistochemistry to analyze the expression of these proteins in tissue microarrays prepared from formalin-fixed, paraffin-embedded primary tumor tissues of 221 patients with SGCs. Using receiver operating characteristic curves, we determined cut-off values of 30% and 5.0% for high expression of ezrin and Ki-67, respectively. High ezrin expression detected in samples from 63 (28.5%) patients with SGCs significantly correlated with male sex, high-grade histopathology, high Ki-67 labeling index, HER2 overexpression, aberrant expression of p53, and distant metastasis. Multivariate analysis demonstrated that high ezrin expression was an independent prognostic factor for shorter overall survival (hazard ratio, 2.11 [1.09-4.05]; P=.027). Furthermore, concomitant high expression of ezrin and HER2 overexpression correlated significantly with shorter disease-free survival and overall survival as well as a high incidence of distant metastasis (P<.001). These findings indicate that ezrin and HER2 expression in patients with SGCs represents a high-grade histopathological subtype that requires adjuvant therapy, including molecularly targeted therapies, to decrease the risk of subsequent metastasis.

The clinical significance of the Ezrin gene and circulating tumor cells in osteosarcoma

Purpose

The aim of this study was to investigate the clinical significance of circulating tumor cells (CTCs) in the peripheral blood of an osteosarcoma and the Ezrin gene expressed in CTCs.

Patients and methods

CTC enrichment was done with CanPatrol™ CTC enrichment technique in 41 patients with osteosarcoma. The characterization of CTCs was performed using a multiple messenger RNA in situ analysis (MRIA). The expression of the Ezrin gene in CTCs was detected by RNA probe technology. The correlations of CTC counts, cell type and the expression level of the Ezrin gene with clinical stage and metastasis of osteosarcoma were analyzed using SPSS 16.0 software.

Results

The CTC counts correlated significantly with Enneking stage (P<0.001). The ratio of mesenchymal CTCs correlated with the distant metastases (P<0.001). Ezrin gene expression in CTCs correlated significantly with distant metastases (χ²=152.51, P=0.000).

Conclusion

The ratio of mesenchymal CTCs in the peripheral blood of osteosarcoma correlates with distant metastases. High expression of Ezrin gene in CTCs correlates with distant metastases.

Orthogonal ubiquitin transfer identifies ubiquitination substrates under differential control by the two ubiquitin activating enzymes

Protein ubiquitination is mediated sequentially by ubiquitin activating enzyme E1, ubiquitin conjugating enzyme E2 and ubiquitin ligase E3. Uba1 was thought to be the only E1 until the recent identification of Uba6. To differentiate the biological functions of Uba1 and Uba6, we applied an orthogonal ubiquitin transfer (OUT) technology to profile their ubiquitination targets in mammalian cells. By expressing pairs of an engineered ubiquitin and engineered Uba1 or Uba6 that were generated for exclusive interactions, we identified 697 potential Uba6 targets and 527 potential Uba1 targets with 258 overlaps. Bioinformatics analysis reveals substantial differences in pathways involving Uba1- and Uba6-specific targets. We demonstrate that polyubiquitination and proteasomal degradation of ezrin and CUGBP1 require Uba6, but not Uba1, and that Uba6 is involved in the control of ezrin localization and epithelial morphogenesis. These data suggest that distinctive substrate pools exist for Uba1 and Uba6 that reflect non-redundant biological roles for Uba6.

The transfer of ubiquitin (UB) to cellular targets is mediated sequentially by three groups of enzymes, UB activating enzyme (E1), UB conjugating enzyme (E2) and UB ligase (E3). Here the authors provide evidence that the two mammalian E1 enzymes, Uba1 and Uba6, exert biologically distinct functions.

Similar expression pattern of NHERF1 and EZRIN in papillary but not in solid areas of human serous ovarian carcinomas

NHERF1 is an adaptor protein expressed in the apical membrane of polarized epithelia, which interacts with the EZRIN-Radixin-Moesin (ERM) family of proteins connecting signaling pathways to the cell cytoskeleton. NHERF1 and EZRIN cooperate in the maintenance of the apical microvilli in polarized epithelial cells. In several types of cancers, NHERF1 and EZRIN are displaced from the apical compartment to the cytoplasm and nuclei of cancer cells. At the present, the distribution of NHERF1 in ovarian tumors is not well known. In this study, NHERF1 expression was examined by immunohistochemistry in cyst adenofibromas, serous borderline tumors, and serous ovarian carcinomas. We observed a strong staining of NHERF1 and EZRIN at the membrane level of borderline tumors and areas of papillary structures in ovarian carcinomas. In tumors without papillary structures and compact structure, NHERF1 was exclusively expressed in the apical pole of the cells at the edges of the clefts of luminal spaces. In contrast, positive expression of EZRIN was found in the membrane of tumor cells within the solid tumor where NHERF1 was not expressed. In summary, this study shows, for the first time, the distribution of NHERF1 in ovarian cancer and reveals a different regulation of NHERF1 and EZRIN expression in ovarian tumors which represents the complexity of the molecular changes of this disease.

Regulation of CD44 expression and focal adhesion by Golgi phosphatidylinositol 4-phosphate in breast cancer

CD44, a transmembrane receptor, is expressed in the standard or variant form and plays a critical role in tumor progression and metastasis. This protein regulates cell adhesion and migration in breast cancer cells. We previously reported that phosphatidylinositol-4-phosphate (PI(4)P) at the Golgi regulates cell migration and invasion in breast cancer cell lines. In this study, we showed that an increase in PI(4)P levels at the Golgi by knockdown of PI(4)P phosphatase SAC1 increased the expression of standard CD44, variant CD44, and ezrin/radixin phosphorylation and enhanced the formation of focal adhesions mediated by CD44 and ezrin/radixin in MCF7 and SK-BR-3 cells. In contrast, knockdown of PI 4-kinase IIIβ in highly invasive MDA-MB-231 cells decreased these factors. These results suggest that SAC1 expression and PI(4)P at the Golgi are important in tumor progression and metastasis and are potential prognostic markers of breast cancers.

A glimpse of the ERM proteins

In all eukaryotes, the plasma membrane is critically important as it maintains the architectural integrity of the cell. Proper anchorage and interaction between the plasma membrane and the cytoskeleton is critical for normal cellular processes. The ERM (ezrin-radixin-moesin) proteins are a class of highly homologous proteins involved in linking the plasma membrane to the cortical actin cytoskeleton. This review takes a succinct look at the biology of the ERM proteins including their structure and function. Current reports on their regulation that leads to activation and deactivation was examined before taking a look at the different interacting partners. Finally, emerging roles of each of the ERM family members in cancer was highlighted.

The cell surface mucin podocalyxin regulates collective breast tumor budding

Background

Overexpression of the transmembrane sialomucin podocalyxin, which is known to play a role in lumen formation during polarized epithelial morphogenesis, is an independent indicator of poor prognosis in a number of epithelial cancers, including those that arise in the breast. Therefore, we set out to determine if podocalyxin plays a functional role in breast tumor progression.

Methods

MCF-7 breast cancer cells, which express little endogenous podocalyxin, were stably transfected with wild type podocalyxin for forced overexpression. 4T1 mammary tumor cells, which express considerable endogenous podocalyxin, were retrovirally transduced with a short hairpin ribonucleic acid (shRNA) targeting podocalyxin for stable knockdown. In vitro, the effects of podocalyxin on collective cellular migration and invasion were assessed in two-dimensional monolayer and three-dimensional basement membrane/collagen gel culture, respectively. In vivo, local invasion was assessed after orthotopic transplantation in immunocompromised mice.

Results

Forced overexpression of podocalyxin caused cohesive clusters of epithelial MCF-7 breast tumor cells to bud off from the primary tumor and collectively invade the stroma of the mouse mammary gland in vivo. This budding was not associated with any obvious changes in histoarchitecture, matrix deposition or proliferation in the primary tumour. In vitro, podocalyxin overexpression induced a collective migration of MCF-7 tumor cells in two-dimensional (2-D) monolayer culture that was dependent on the activity of the actin scaffolding protein ezrin, a cytoplasmic binding partner of podocalyxin. In three-dimensional (3-D) culture, podocalyxin overexpression induced a collective budding and invasion that was dependent on actomyosin contractility. Interestingly, the collectively invasive cell aggregates often contained expanded microlumens that were also observed in vivo. Conversely, when endogenous podocalyxin was removed from highly metastatic, but cohesive, 4T1 mammary tumor cells there was a decrease in collective invasion in three-dimensional culture.

Conclusions

Podocalyxin is a tumor cell-intrinsic regulator of experimental collective tumor cell invasion and tumor budding.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0670-4) contains supplementary material, which is available to authorized users.

Prognostic Value of Ezrin in Various Cancers: A Systematic Review and Updated Meta-analysis

More and more studies have investigated the effects of Ezrin expression level on the prognostic role in various tumors. However, the results remain controversial rather than conclusive. Here, we performed a systematic review and meta-analysis to evaluate the correlation of Ezrin expression with the prognosis in various tumors. the pooled hazard ratios (HR) with the corresponding 95% confidence intervals (95% CI) were calculated to evaluate the degree of the association. The overall results of fifty-five studies with 6675 patients showed that elevated Ezrin expression was associated with a worse prognosis in patients with cancers, with the pooled HRs of 1.86 (95% CI: 1.51–2.31, P < 0.001) for over survival (OS), 2.55 (95% CI: 2.14–3.05, P < 0.001) for disease-specific survival (DFS) and 2.02 (95% CI: 1.13–3.63, P = 0.018) for disease-specific survival (DSS)/metastasis-free survival (MFS) by the random, fixed and random effect model respectively. Similar results were also observed in the stratified analyses by tumor types, ethnicity background and sample source. This meta-analysis suggests that Ezrin may be a potential prognostic marker in cancer patients. High Ezrin is associated with a poor prognosis in a variety of solid tumors.

Ezrin regulates focal adhesion and invadopodia dynamics by altering calpain activity to promote breast cancer cell invasion

Ezrin regulates proper focal adhesion and invadopodia turnover by regulating calpain-1, in part by directing its proteolytic activity toward key substrates talin, FAK, and cortactin. Ezrin-deficient tumor cells show reduced lung seeding and colonization in vivo but not primary tumor growth, thus implicating ezrin as a metastasis-associated protein.

Up-regulation of the cytoskeleton linker protein ezrin frequently occurs in aggressive cancer types and is closely linked with metastatic progression. However, the underlying molecular mechanisms detailing how ezrin is involved in the invasive and metastatic phenotype remain unclear. Here we report a novel function of ezrin in regulating focal adhesion (FA) and invadopodia dynamics, two key processes required for efficient invasion to occur. We show that depletion of ezrin expression in invasive breast cancer cells impairs both FA and invadopodia turnover. We also demonstrate that ezrin-depleted cells display reduced calpain-mediated cleavage of the FA and invadopodia-associated proteins talin, focal adhesion kinase (FAK), and cortactin and reduced calpain-1–specific membrane localization, suggesting a requirement for ezrin in maintaining proper localization and activity of calpain-1. Furthermore, we show that ezrin is required for cell directionality, early lung seeding, and distant organ colonization but not primary tumor growth. Collectively our results unveil a novel mechanism by which ezrin regulates breast cancer cell invasion and metastasis.

Ezrin Binds to DEAD-Box RNA Helicase DDX3 and Regulates Its Function and Protein Level

Ezrin is a key regulator of cancer metastasis that links the extracellular matrix to the actin cytoskeleton and regulates cell morphology and motility. We discovered a small-molecule inhibitor, NSC305787, that directly binds to ezrin and inhibits its function. In this study, we used a nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS-MS)-based proteomic approach to identify ezrin-interacting proteins that are competed away by NSC305787. A large number of the proteins that interact with ezrin were implicated in protein translation and stress granule dynamics. We validated direct interaction between ezrin and the RNA helicase DDX3, and NSC305787 blocked this interaction. Downregulation or long-term pharmacological inhibition of ezrin led to reduced DDX3 protein levels without changes in DDX3 mRNA. Ectopic overexpression of ezrin in low-ezrin-expressing osteosarcoma cells caused a notable increase in DDX3 protein levels. Ezrin inhibited the RNA helicase activity of DDX3 but increased its ATPase activity. Our data suggest that ezrin controls the translation of mRNAs preferentially with a structured 5' untranslated region, at least in part, by sustaining the protein level of DDX3 and/or regulating its function. Therefore, our findings suggest a novel function for ezrin in regulation of gene translation that is distinct from its canonical role as a cytoskeletal scaffold at the cell membrane.

Expression of maspin and ezrin proteins in periocular Basal cell carcinoma

Background. The aim of this study was to investigate maspin and ezrin expression in different subtypes of periocular basal cell carcinoma (BCC). Methods. Tissue samples from 43 patients with periocular BCC. Our cases were comprised of 10 morpheaform, 25 nodular, and 8 adenoid type BCCs. Immunohistochemical staining for maspin and ezrin was performed by Envision detection system. Results. There was no difference between different subtypes of BCC in maspin expression regarding positivity, intensity, and pattern of expression. Ezrin was expressed in all subtypes of BCC but the intensity was significantly higher in morpheaform BCC compared to nodular and adenoid types (P < 0.001 and P = 0.012, resp.); ninety percent of morpheaform samples showed strong ezrin intensity, while this strong intensity was only present in 25% and 12% of adenoid and nodular subtypes, respectively. There was no correlation between age, sex, or tumor margin involvement and expression of neither maspin nor ezrin. There was no correlation between maspin and ezrin expression except in nodular type, in which an inverse correlation was found (P = 0.004). Conclusion. Ezrin is expressed intensely in morpheaform BCC of periocular region. Further studies are needed to show the significance of this finding in prognosis of morpheaform BCC.

Imaging tumour heterogeneity of the consequences of a PKCα-substrate interaction in breast cancer patients

Breast cancer heterogeneity demands that prognostic models must be biologically driven and recent clinical evidence indicates that future prognostic signatures need evaluation in the context of early compared with late metastatic risk prediction. In pre-clinical studies, we and others have shown that various protein-protein interactions, pertaining to the actin microfilament-associated proteins, ezrin and cofilin, mediate breast cancer cell migration, a prerequisite for cancer metastasis. Moreover, as a direct substrate for protein kinase Cα, ezrin has been shown to be a determinant of cancer metastasis for a variety of tumour types, besides breast cancer; and has been described as a pivotal regulator of metastasis by linking the plasma membrane to the actin cytoskeleton. In the present article, we demonstrate that our tissue imaging-derived parameters that pertain to or are a consequence of the PKC-ezrin interaction can be used for breast cancer prognostication, with inter-cohort reproducibility. The application of fluorescence lifetime imaging microscopy (FLIM) in formalin-fixed paraffin-embedded patient samples to probe protein proximity within the typically <10 nm range to address the oncological challenge of tumour heterogeneity, is discussed.

The role of phosphoinositide-regulated actin reorganization in chemotaxis and cell migration

Reorganization of the actin cytoskeleton is essential for cell motility and chemotaxis. Actin-binding proteins (ABPs) and membrane lipids, especially phosphoinositides PI(4,5)P2 and PI(3,4,5)P3 are involved in the regulation of this reorganization. At least 15 ABPs have been reported to interact with, or regulated by phosphoinositides (PIPs) whose synthesis is regulated by extracellular signals. Recent studies have uncovered several parallel intracellular signalling pathways that crosstalk in chemotaxing cells. Here, we review the roles of ABPs and phosphoinositides in chemotaxis and cell migration.

LINKED ARTICLES

This article is part of a themed section on Cytoskeleton, Extracellular Matrix, Cell Migration, Wound Healing and Related Topics. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-24.

A novel role for ezrin in breast cancer angio/lymphangiogenesis

INTRODUCTION

Recent evidence suggests that tumour lymphangiogenesis promotes lymph node metastasis, a major prognostic factor for survival of breast cancer patients. However, signaling mechanisms involved in tumour-induced lymphangiogenesis remain poorly understood. The expression of ezrin, a membrane cytoskeletal crosslinker and Src substrate, correlates with poor outcome in a diversity of cancers including breast. Furthermore, ezrin is essential in experimental invasion and metastasis models of breast cancer. Ezrin acts cooperatively with Src in the regulation of the Src-induced malignant phenotype and metastasis. However, it remains unclear if ezrin plays a role in Src-induced tumour angio/lymphangiogenesis.

METHODS

The effects of ezrin knockdown and mutation on angio/lymphangiogenic potential of human MDA-MB-231 and mouse AC2M2 mammary carcinoma cell lines were examined in the presence of constitutively active or wild-type (WT) Src. In vitro assays using primary human lymphatic endothelial cells (hLEC), an ex vivo aortic ring assay, and in vivo tumour engraftment were utilized to assess angio/lymphangiogenic activity of cancer cells.

RESULTS

Ezrin-deficient cells expressing activated Src displayed significant reduction in endothelial cell branching in the aortic ring assay in addition to reduced hLEC migration, tube formation, and permeability compared to the controls. Intravital imaging and microvessel density (MVD) analysis of tumour xenografts revealed significant reductions in tumour-induced angio/lymphangiogenesis in ezrin-deficient cells when compared to the WT or activated Src-expressing cells. Moreover, syngeneic tumours derived from ezrin-deficient or Y477F ezrin-expressing (non-phosphorylatable by Src) AC2M2 cells further confirmed the xenograft results. Immunoblotting analysis provided a link between ezrin expression and a key angio/lymphangiogenesis signaling pathway by revealing that ezrin regulates Stat3 activation, VEGF-A/-C and IL-6 expression in breast cancer cell lines. Furthermore, high expression of ezrin in human breast tumours significantly correlated with elevated Src expression and the presence of lymphovascular invasion.

CONCLUSIONS

The results describe a novel function for ezrin in the regulation of tumour-induced angio/lymphangiogenesis promoted by Src in breast cancer. The combination of Src/ezrin might prove to be a beneficial prognostic/predictive biomarker for early-stage metastatic breast cancer.