Phosphorylated ezrin is located in the nucleus of the osteosarcoma cell

FERM domain-containing proteins are active components of the cell nucleus

The FERM domain is a conserved and widespread protein module that appeared in the common ancestor of amoebae, fungi, and animals, and is therefore now found in a wide variety of species. The primary function of the FERM domain is localizing to the plasma membrane through binding lipids and proteins of the membrane; thus, for a long time, FERM domain-containing proteins (FDCPs) were considered exclusively cytoskeletal. Although their role in the cytoplasm has been extensively studied, the recent discovery of the presence and importance of cytoskeletal proteins in the nucleus suggests that FDCPs might also play an important role in nuclear function. In this review, we collected data on their nuclear localization, transport, and possible functions, which are still scattered throughout the literature, with special regard to the role of the FERM domain in these processes. With this, we would like to draw attention to the exciting, new dimension of the role of FDCPs, their nuclear activity, which could be an interesting novel direction for future research.

A bipartite NLS motif mediates the nuclear import of Drosophila moesin

The ERM protein family, which consists of three closely related proteins in vertebrates, ezrin, radixin, and moesin (ERM), is an ancient and important group of cytoplasmic actin-binding and organizing proteins. With their FERM domain, ERMs bind various transmembrane proteins and anchor them to the actin cortex through their C-terminal F-actin binding domain, thus they are major regulators of actin dynamics in the cell. ERMs participate in many fundamental cellular processes, such as phagocytosis, microvilli formation, T-cell activation and tumor metastasis. We have previously shown that, besides its cytoplasmic activities, the single ERM protein of Drosophila melanogaster, moesin, is also present in the cell nucleus, where it participates in gene expression and mRNA export. Here we study the mechanism by which moesin enters the nucleus. We show that the nuclear import of moesin is an NLS-mediated, active process. The nuclear localization sequence of the moesin protein is an evolutionarily highly conserved, conventional bipartite motif located on the surface of the FERM domain. Our experiments also reveal that the nuclear import of moesin does not require PIP2 binding or protein activation, and occurs in monomeric form. We propose, that the balance between the phosphorylated and non-phosphorylated protein pools determines the degree of nuclear import of moesin.

The MEF2A transcription factor interactome in cardiomyocytes

Transcriptional regulators encoded by the Myocyte Enhancer Factor 2 (MEF2) gene family play a fundamental role in cardiac development, homeostasis and pathology. Previous studies indicate that MEF2A protein-protein interactions serve as a network hub in several cardiomyocyte cellular processes. Based on the idea that interactions with regulatory protein partners underly the diverse roles of MEF2A in cardiomyocyte gene expression, we undertook a systematic unbiased screen of the MEF2A protein interactome in primary cardiomyocytes using an affinity purification-based quantitative mass spectrometry approach. Bioinformatic processing of the MEF2A interactome revealed protein networks involved in the regulation of programmed cell death, inflammatory responses, actin dynamics and stress signaling in primary cardiomyocytes. Further biochemical and functional confirmation of specific protein-protein interactions documented a dynamic interaction between MEF2A and STAT3 proteins. Integration of transcriptome level data from MEF2A and STAT3-depleted cardiomyocytes reveals that the balance between MEF2A and STAT3 activity exerts a level of executive control over the inflammatory response and cardiomyocyte cell survival and experimentally ameliorates Phenylephrine induced cardiomyocyte hypertrophy. Lastly, we identified several MEF2A/STAT3 co-regulated genes, including the MMP9 gene. Herein, we document the cardiomyocyte MEF2A interactome, which furthers our understanding of protein networks involved in the hierarchical control of normal and pathophysiological cardiomyocyte gene expression in the mammalian heart.

Role of Ezrin in Asthma-Related Airway Inflammation and Remodeling

Ezrin is an actin binding protein connecting the cell membrane and the cytoskeleton, which is crucial to maintaining cell morphology, intercellular adhesion, and cytoskeleton remodeling. Asthma involves dysfunction of inflammatory cells, cytokines, and airway structural cells. Recent studies have shown that ezrin, whose function is affected by extensive phosphorylation and protein interactions, is closely associated with asthma, may be a therapeutic target for asthma treatment. In this review, we summarize studies on ezrin and discuss its role in asthma-related airway inflammation and remodeling.

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.

Osteosarcoma mechanobiology and therapeutic targets

Osteosarcoma (OS) is the one of the most common primary tumors of bone with less than a 20% 5-year survival rate after the development of metastases. OS is highly predisposed in Paget's disease (PD) of bone, and both have common characteristic skeletal features due to rapid bone remodeling. OS prognosis is location dependent which further emphasizes the likely contribution of the bone microenvironment in its pathogenesis. Mechanobiology is the phenomenon when mechanical cues from the changing physical microenvironment of bone are transduced to biological pathways through mechanosensitive cellular components. Mechanobiology-driven therapies have been used for curbing tumor progression by direct alteration of the physical microenvironment or inhibition of metastasis-associated mechanosensitive proteins. This review emphasizes the contribution of mechanobiology to OS progression, and sheds light on current mechanobiology-based therapies and potential new targets for improving disease management. Additionally, the variety of 3D models currently used to study OS mechanobiology are summarized.

Ezrin Mediates Invasion and Metastasis in Tumorigenesis: A Review

Ezrin, as encoded by the EZR gene, is a member of the Ezrin/Radixin/Moesin (ERM) family. The ERM family includes three highly related actin filament binding proteins, Ezrin, Radixin, and Moesin. These three members share similar structural properties containing an N-terminal domain named FERM, a central helical linker region, and a C-terminal domain that mediates the interaction with F-actin. Ezrin protein is highly regulated through the conformational change between a closed, inactivate form and an open, active form. As a membrane-cytoskeleton linker protein, Ezrin facilitates numerous signal transductions in tumorigenesis and mediates diverse essential functions through interactions with a variety of growth factor receptors and adhesion molecules. Emerging evidence has demonstrated that Ezrin is an oncogene protein, as high levels of Ezrin are associated with metastatic behavior in various types of cancer. The diverse functions attributed to Ezrin and the understanding of how Ezrin drives the deadly process of metastasis are complex and often controversial. Here by reviewing recent findings across a wide spectrum of cancer types we will highlight the structures, protein interactions and oncogenic roles of Ezrin as well as the emerging therapeutic agents targeting Ezrin. This review provides a comprehensive framework to guide future studies of Ezrin and other ERM proteins in basic and clinical studies.

Targeting Mechanotransduction in Osteosarcoma: A Comparative Oncology Perspective

Mechanotransduction is the process in which cells can convert extracellular mechanical stimuli into biochemical changes within a cell. While this a normal process for physiological development and function in many organ systems, tumour cells can exploit this process to promote tumour progression. Here we summarise the current state of knowledge of mechanotransduction in osteosarcoma (OSA), the most common primary bone tumour, referencing both human and canine models and other similar mesenchymal malignancies (e.g., Ewing sarcoma). Specifically, we discuss the mechanical properties of OSA cells, the pathways that these cells utilise to respond to external mechanical cues, and mechanotransduction-targeting strategies tested in OSA so far. We point out gaps in the literature and propose avenues to address them. Understanding how the physical microenvironment influences cell signalling and behaviour will lead to the improved design of strategies to target the mechanical vulnerabilities of OSA cells.

The matrix environmental and cell mechanical properties regulate cell migration and contribute to the invasive phenotype of cancer cells

The minimal structural unit of a solid tumor is a single cell or a cellular compartment such as the nucleus. A closer look inside the cells reveals that there are functional compartments or even structural domains determining the overall properties of a cell such as the mechanical phenotype. The mechanical interaction of these living cells leads to the complex organization such as compartments, tissues and organs of organisms including mammals. In contrast to passive non-living materials, living cells actively respond to the mechanical perturbations occurring in their microenvironment during diseases such as fibrosis and cancer. The transformation of single cancer cells in highly aggressive and hence malignant cancer cells during malignant cancer progression encompasses the basement membrane crossing, the invasion of connective tissue, the stroma microenvironments and transbarrier migration, which all require the immediate interaction of the aggressive and invasive cancer cells with the surrounding extracellular matrix environment including normal embedded neighboring cells. All these steps of the metastatic pathway seem to involve mechanical interactions between cancer cells and their microenvironment. The pathology of cancer due to a broad heterogeneity of cancer types is still not fully understood. Hence it is necessary to reveal the signaling pathways such as mechanotransduction pathways that seem to be commonly involved in the development and establishment of the metastatic and mechanical phenotype in several carcinoma cells. We still do not know whether there exist distinct metastatic genes regulating the progression of tumors. These metastatic genes may then be activated either during the progression of cancer by themselves on their migration path or in earlier stages of oncogenesis through activated oncogenes or inactivated tumor suppressor genes, both of which promote the metastatic phenotype. In more detail, the adhesion of cancer cells to their surrounding stroma induces the generation of intracellular contraction forces that deform their microenvironments by alignment of fibers. The amplitude of these forces can adapt to the mechanical properties of the microenvironment. Moreover, the adhesion strength of cancer cells seems to determine whether a cancer cell is able to migrate through connective tissue or across barriers such as the basement membrane or endothelial cell linings of blood or lymph vessels in order to metastasize. In turn, exposure of adherent cancer cells to physical forces, such as shear flow in vessels or compression forces around tumors, reinforces cell adhesion, regulates cell contractility and restructures the ordering of the local stroma matrix that leads subsequently to secretion of crosslinking proteins or matrix degrading enzymes. Hence invasive cancer cells alter the mechanical properties of their microenvironment. From a mechanobiological point-of-view, the recognized physical signals are transduced into biochemical signaling events that guide cellular responses such as cancer progression after the malignant transition of cancer cells from an epithelial and non-motile phenotype to a mesenchymal and motile (invasive) phenotype providing cellular motility. This transition can also be described as the physical attempt to relate this cancer cell transitional behavior to a T1 phase transition such as the jamming to unjamming transition. During the invasion of cancer cells, cell adaptation occurs to mechanical alterations of the local stroma, such as enhanced stroma upon fibrosis, and therefore we need to uncover underlying mechano-coupling and mechano-regulating functional processes that reinforce the invasion of cancer cells. Moreover, these mechanisms may also be responsible for the awakening of dormant residual cancer cells within the microenvironment. Physicists were initially tempted to consider the steps of the cancer metastasis cascade as single events caused by a single mechanical alteration of the overall properties of the cancer cell. However, this general and simple view has been challenged by the finding that several mechanical properties of cancer cells and their microenvironment influence each other and continuously contribute to tumor growth and cancer progression. In addition, basement membrane crossing, cell invasion and transbarrier migration during cancer progression is explained in physical terms by applying physical principles on living cells regardless of their complexity and individual differences of cancer types. As a novel approach, the impact of the individual microenvironment surrounding cancer cells is also included. Moreover, new theories and models are still needed to understand why certain cancers are malignant and aggressive, while others stay still benign. However, due to the broad variety of cancer types, there may be various pathways solely suitable for specific cancer types and distinct steps in the process of cancer progression. In this review, physical concepts and hypotheses of cancer initiation and progression including cancer cell basement membrane crossing, invasion and transbarrier migration are presented and discussed from a biophysical point-of-view. In addition, the crosstalk between cancer cells and a chronically altered microenvironment, such as fibrosis, is discussed including the basic physical concepts of fibrosis and the cellular responses to mechanical stress caused by the mechanically altered microenvironment. Here, is highlighted how biophysical approaches, both experimentally and theoretically, have an impact on classical hallmarks of cancer and fibrosis and how they contribute to the understanding of the regulation of cancer and its progression by sensing and responding to the physical environmental properties through mechanotransduction processes. Finally, this review discusses various physical models of cell migration such as blebbing, nuclear piston, protrusive force and unjamming transition migration modes and how they contribute to cancer progression. Moreover, these cellular migration modes are influenced by microenvironmental perturbances such as fibrosis that can induce mechanical alterations in cancer cells, which in turn may impact the environment. Hence, the classical hallmarks of cancer need to be refined by including biomechanical properties of cells, cell clusters and tissues and their microenvironment to understand mechano-regulatory processes within cancer cells and the entire organism.

Adenovirus-mediated small interfering RNA targeting ezrin induces apoptosis and inhibits metastasis of human osteosarcoma MG-63 cells

Osteosarcoma is a disease prone to recurrence and metastasis, and adenovirus expression vector is frequently studied as a therapeutic target of osteosarcoma in recent years. The present study attempts to explore the effect of adenovirus-mediated siRNA targetting ezrin on the proliferation, migration, invasion, and apoptosis of human osteosarcoma MG-63 cells. Human osteosarcoma MG-63 cell line was selected for construction of recombinant adenovirus vector. The mRNA and protein levels of ezrin, Bcl2-associated X protein (Bax), B cell lymphoma-2 (Bcl-2), p21, p53, Caspase-3, matrix metalloproteinase (MMP) 2 (MMP-2) and MMP-9, Cyclin D1, and cyclin-dependent kinase 4a (CDK4a) were determined. Through ELISA, the levels of Caspase-3, MMP-2 and MMP-9 were examined. Finally, human osteosarcoma MG-63 cell viability, growth, invasion, migration, and apoptosis were detected. Initially, adenovirus expression vector of ezrin was constructed by ezrin 2 siRNA sequence. Adenovirus-mediated siRNA targetting ezrin reduced expression of ezrin in MG-63 cells. The results revealed that adenovirus-mediated siRNA targetting ezrin elevated expression levels of Bax, p21, p53, and Caspase-3, Cyclin D1, and CDK4a and reduced expression levels of Bcl-2, MMP-2 and MMP-9. Furthermore, adenovirus-mediated siRNA targetting ezrin inhibited human osteosarcoma MG-63 cell viability, growth, invasion, and migration, and promoted apoptosis. Our study demonstrates that adenovirus-mediated siRNA targetting ezrin can induce apoptosis and inhibit the proliferation, migration, and invasion of human osteosarcoma MG-63 cells.

Epac1 links prostaglandin E2 to β-catenin-dependent transcription during epithelial-to-mesenchymal transition

In epithelial cells, β-catenin is localized at cell-cell junctions where it stabilizes adherens junctions. When these junctions are disrupted, β-catenin can translocate to the nucleus where it functions as a transcriptional cofactor. Recent research has indicated that PGE₂ enhances the nuclear function of β-catenin through cyclic AMP. Here, we aim to study the role of the cyclic AMP effector Epac in β-catenin activation by PGE₂ in non-small cell lung carcinoma cells.

We show that PGE₂ induces a down-regulation of E-cadherin, promotes cell migration and enhances β-catenin translocation to the nucleus. This results in β-catenin-dependent gene transcription. We also observed increased expression of Epac1. Inhibition of Epac1 activity using the CE3F4 compound or Epac1 siRNA abolished the effects of PGE₂ on β-catenin. Further, we observed that Epac1 and β-catenin associate together. Expression of an Epac1 mutant with a deletion in the nuclear pore localization sequence prevents this association. Furthermore, the scaffold protein Ezrin was shown to be required to link Epac1 to β-catenin.

This study indicates a novel role for Epac1 in PGE₂-induced EMT and subsequent activation of β-catenin.

Whole-exome analysis in osteosarcoma to identify a personalized therapy

Osteosarcoma is the most common pediatric primary non-hematopoietic bone tumor. Survival of these young patients is related to the response to chemotherapy and development of metastases. Despite many advances in cancer research, chemotherapy regimens for osteosarcoma are still based on non-selective cytotoxic drugs. It is essential to investigate new specific molecular therapies for osteosarcoma to increase the survival rate of these patients. We performed exomic sequence analyses of 8 diagnostic biopsies of patients with conventional high grade osteosarcoma to advance our understanding of their genetic underpinnings and to correlate the genetic alteration with the clinical and pathological features of each patient to identify a personalized therapy. We identified 18,275 somatic variations in 8,247 genes and we found three mutated genes in 7/8 (87%) samples (KIF1B, NEB and KMT2C). KMT2C showed the highest number of variations; it is an important component of a histone H3 lysine 4 methyltransferase complex and it is one of the histone modifiers previously implicated in carcinogenesis, never studied in osteosarcoma. Moreover, we found a group of 15 genes that showed variations only in patients that did not respond to therapy and developed metastasis and some of these genes are involved in carcinogenesis and tumor progression in other tumors. These data could offer the opportunity to get a key molecular target to identify possible new strategies for early diagnosis and new therapeutic approaches for osteosarcoma and to provide a tailored treatment for each patient based on their genetic profile.

Inside the Cell: Integrins as New Governors of Nuclear Alterations?

Cancer cell migration is a complex process that requires coordinated structural changes and signals in multiple cellular compartments. The nucleus is the biggest and stiffest organelle of the cell and might alter its physical properties to allow cancer cell movement. Integrins are transmembrane receptors that mediate cell-cell and cell-extracellular matrix interactions, which regulate numerous intracellular signals and biological functions under physiological conditions. Moreover, integrins orchestrate changes in tumor cells and their microenvironment that lead to cancer growth, survival and invasiveness. Most of the research efforts have focused on targeting integrin-mediated adhesion and signaling. Recent exciting data suggest the crucial role of integrins in controlling internal cellular structures and nuclear alterations during cancer cell migration. Here we review the emerging role of integrins in nuclear biology. We highlight increasing evidence that integrins are critical for changes in multiple nuclear components, the positioning of the nucleus and its mechanical properties during cancer cell migration. Finally, we discuss how integrins are integral proteins linking the plasma membrane and the nucleus, and how they control cell migration to enable cancer invasion and infiltration. The functional connections between these cell receptors and the nucleus will serve to define new attractive therapeutic targets.

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.

mTOR signaling in osteosarcoma: Oncogenesis and therapeutic aspects (Review)

The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that belongs to the phosphoinositide-3-kinase (PI3K)-related kinase family. Oncogenic activation of mTOR signaling significantly contributes to the progression of different types of cancers including osteosarcoma (OS; the most common primary malignant tumor of bone). In the present study, we review the association of the mTOR signaling pathway with OS, and the possible effective treatment strategies by targeting this pathway. In the metastatic behavior of OS, one of the most common actionable aberrations was found in the PI3K/Akt/mTOR pathway. Upon phosphorylation, activated mTOR contributes to OS cellular transformation and poor cancer prognosis via downstream effectors such as S6K1, 4EBP1 and eIF4E, which are overexpressed in OS. Targeting the mTOR complex is a significant approach in cancer therapeutic research, and of course, rapamycin is the primary inhibitor of mTOR. Various other chemotherapeutic molecules have also shown potential activity against mTOR. As mTOR is a new promising oncological target and blockade of the mTOR pathway with selective inhibitors has significant potential in OS therapeutic research, the development of the optimal dose, regimen and a rationale for the use of mTOR inhibitors in combination with other anticancer agents may provide a successful treatment strategy for OS.

The difference in Ezrin-pAkt signaling axis between lepidic and papillary predominant invasive adenocarcinomas of the lung

PURPOSE

Histologic classification of invasive lung adenocarcinomas by predominant subtype has prognostic value. Papillary predominant adenocarcinoma (PPA) reportedly shows poorer prognosis than lepidic predominant adenocarcinoma (LPA); however, biological differences between PPA and LPA are unclear. The purpose of this study was to clarify biological differences between PPA and LPA.

METHODS

Clinicopathological characteristics of invasive 62 PPAs and 117 LPAs smaller than 30 mm were investigated. Furthermore, we compared immunochemical staining scores of 9 molecular markers (E-cadherin, S100A4, fibronectin, integrinβ1, ezrin, GLUT1, ALDH1, SOX2 and Nanog) between PPA and LPA. We performed Western blot analysis using ezrin shRNA-knockdown lung adenocarcinoma cell lines to examine whether molecules that are highly expressed in PPA, such as ezrin, affect pAkt. Finally, we performed immunochemical staining to compare pAkt expression level in PPA and LPA.

RESULTS

Lymphovascular and pleural invasion and lymph node metastasis were significantly more often detected in PPA than in LPA (lymphatic permeation: 31 vs 3 %, vascular invasion: 35 vs 3 %, pleural invasion: 29 vs 5 %, lymph node metastasis: 18 vs 1 %; all P < 0.01). Immunohistochemical (IHC) study revealed that expression score of ezrin was significantly higher in PPA than in LPA (38.3 vs 15.0; P < 0.01). The level of pAkt decreased in shEzrin-induced PC-9 and A549 cancer cells. Moreover, the IHC staining score of pAkt was significantly higher in PPA than in LPA (13.3 vs 0.0; P < 0.01).

CONCLUSIONS

Our results show that the activation of the ezrin-pAkt signaling axis is associated with the more aggressive clinicopathological features of PPA compared with LPA.

Expression of ezrin, CD44, and VEGF in giant cell tumor of bone and its significance

Background

This research aimed to study the role of ezrin, CD44, and VEGF in invasion, metastasis, recurrence, and prognosis of giant cell tumor of bone (GCTB) and its association with the clinical and pathological features of GCTB.

Methods

Expression status of ezrin, CD44, and VEGF in 80 GCTB tissues and its adjacent noncancerous tissue samples were measured with immunohistochemical and Elivison staining. Their correlation with the clinical and pathologic factors was statistically analyzed by chi-square test.

Results

The expression status of ezrin, CD44, and VEGF were significantly higher in GCTB tissue samples than in its adjacent noncancerous tissue samples and in GCTB at Campanacci stage III than in Campanacci stages I and II (P < 0.05). No significant difference was found in age and sex of the patients and locations of the tumor (P > 0.05). Survival analysis showed that the expression status of ezrin, CD44, VEGF, and Campanacci clinical stages of GCTB were positively associated with the survival rate of GCTB patients and negatively associated with ezrin and Campanacci stages of GCTB, indicating that ezrin, CD44, VEGF, and Campanacci clinical stages of GCTB are the independent factors for GCTB.

Conclusions

Ezrin, CD44, and VEGF are over-expressed in GCTB tissue and its adjacent noncancerous tissue samples and may play an important role in the occurrence, invasion, metastasis, and recurrence of GCTB. Measurement of ezrin, CD44, and VEGF expression status may contribute to the judgment of prognosis of GCTB patients.

Screening for metastatic osteosarcoma biomarkers with a DNA microarray

OBJECTIVE

The aim of this study was to screen for possible biomarkers of metastatic osteosarcoma (OS) using a DNA microarray.

METHODS

We downloaded the gene expression profile GSE49003 from Gene Expression Omnibus database, which included 6 gene chips from metastatic and 6 from non-metastatic OS patients. The R package was used to screen and identify differentially expressed genes (DEGs) between metastatic and non-metastatic OS patients. Then we compared the expression of DEGs in the two groups and sub-grouped into up-regulated and down-regulated, followed by functional enrichment analysis using the DAVID system. Subsequently, we constructed an miRNA-DEG regulatory network with the help of WebGestalt software.

RESULTS

A total of 323 DEGs, including 134 up-regulated and 189 down-regulated, were screened out. The up-regulated DEGs were enriched in 14 subcategories and most significantly in cytoskeleton organization, while the down-regulated DEGs were prevalent in 13 subcategories, especially wound healing. In addition, we identified two important miRNAs (miR-202 and miR-9) pivotal for OS metastasis, and their relevant genes, CALD1 and STX1A.

CONCLUSIONS

MiR-202 and miR-9 are potential key factors affecting the metastasis of OS and CALD1 and STX1A may be possible targets beneficial for the treatment of metastatic OS. However, further experimental studies are needed to confirm our results.

Ezrin silencing remodulates the expression of Phosphoinositide-specific Phospholipase C enzymes in human osteosarcoma cell lines

Ezrin, a protein belonging to the Ezrin, radixin and moesin (ERM) family, was engaged in the metastatic spread of osteosarcoma. The Protein 4.1, Ezrin, radixin, moesin (FERM) domain of Ezrin binds the membrane Phosphatydil inositol (4,5) bisphosphate (PIP2), a crucial molecule belonging to the Phosphoinositide (PI) signal transduction pathway. The cytoskeleton cross-linker function of Ezrin largely depends on membrane PIP2 levels, and thus upon the activity of related enzymes belonging to the PI-specific phospholipase C (PI-PLC) family. Based on the role of Ezrin in tumour progression and metastasis, we silenced the expression of Vil2 (OMIM *123900), the gene which codifies for Ezrin, in cultured human osteosarcoma 143B and Hs888 cell lines. After Ezrin silencing, the growth rate of both cell lines was significantly reduced and morphogical changes were observed. We also observed moderate variations both of selected PI-PLC enzymes within the cell and of expression of the corresponding PLC genes. In 143B cell line the transcription of PLCB1 decreased, of PLCG2 increased and of PLCE differed in a time-dependent manner. In Hs888, the expression of PLCB1 and of PLCD4 significantly increased, of PLCE moderately increased in a time dependent manner; the expression of PLCG2 was up-regulated. These observations indicate that Ezrin silencing affects the transcription of selected PLC genes, suggesting that Ezrin might influence the expression regulation of PI-PLC enzymes.

Prognostic role of cytovillin expression in patients with osteosarcoma: a meta-analysis

Cytovillin plays structural and regulatory roles in the assembly and stabilization of specialized plasma membrane domains and in the tumor angiogenesis. Cytovillin expression has been proposed to be an effective biomarker of prognosis in patients with osteosarcoma, and many studies have been performed to assess the prognostic role of cytovillin expression in patients with osteosarcoma. We performed this meta-analysis to provide a comprehensive evaluation of the role of cytovillin expression on the overall survival rate by calculating the pooled risk ratio (RR) with corresponding 95% confidence interval (95% CI). Finally, eight studies with a total of 415 patients with osteosarcoma were included into the meta-analysis. Meta-analysis of total eight studies showed that cytovillin expression was obviously associated with lower overall survival rate in patients with osteosarcoma (RR = 0.41, 95% CI 0.28–0.58, P < 0.001). Meta-analysis of five studies with large sample still showed that cytovillin expression was obviously associated with lower overall survival rate (RR = 0.48, 95% CI 0.38–0.60, P < 0.001). In conclusion, the meta-analysis shows that cytovillin expression is obviously associated with lower overall survival rate in patients with osteosarcoma, and it is an effective biomarker of prognosis.

Prognostic implications of ezrin and phosphorylated ezrin expression in non-small cell lung cancer

BACKGROUND

The cytoskeletal organizer ezrin is a member of the ezrin-radixin-moesin (ERM) family and plays important roles in not only cell motility, cell adhesion, and apoptosis, but also in various cell signaling pathways. Phosphorylation at Thr-567 and Tyr-353 are key regulatory events in the transition of the dormant to active form of ezrin. This study investigated the prognostic implications of ezrin and phosphorylated ezrin (p-ezrin) expression in non-small cell lung carcinoma (NSCLC).

METHODS

Ezrin and p-ezrin protein expressions were examined by immunohistochemistry in 150 NSCLC and adjacent non-tumor tissues and 14 normal lung tissues. qRT-PCR was used to determine ezrin mRNA expression levels in fresh tissues. The correlations between overexpression of ezrin and p-ezrin and the clinicopathological features of NSCLC were analyzed. The survival rates were calculated by the Kaplan-Meier method for 108 NSCLC cases.

RESULTS

Ezrin and ezrinThr-567 proteins showed cytosolic and membranous staining patterns; however, ezrinTyr-353 protein only showed cytosolic staining. Ezrin and p-ezrin were significantly upregulated in NSCLC compared with the normal counterparts. Increased ezrin, ezrinThr-567, and ezrinTyr-353 levels were correlated with the late stage and poor differentiation of NSCLC. However, only ezrinThr-567 was correlated with the presence of lymph node metastasis. In regard to survival, only ezrinThr-567 was related with the overall survival time of patients with NSCLC, and both ezrin and ezrinThr-567 were associated with shortened survival time for patients with early stage NSCLC.

CONCLUSIONS

Ezrin and p-ezrin, especially ezrinThr-567, may prove to be useful as a novel prognostic biomarker of NSCLC.

Role of ezrin in osteosarcoma metastasis

The cause of death for the vast majority of cancer patients is the development of metastases at sites distant from that of the primary tumor. For most pediatric sarcoma patients such as those with osteosarcoma (OS), despite successful management of the primary tumor through multimodality approaches, the development of metastases, commonly to the lungs, is the cause of death. Significant improvements in long-term outcome for these patients have not been seen in more than 30 years. Furthermore, the long-term outcome for patients who present with metastatic disease is grave [1-5]. New treatment options are needed.Opportunities to improve outcomes for patients who present with metastases and those at-risk for progression and metastasis require an improved understanding of cancer progression and metastasis. With this goal in mind we and others have identified ezrin as a metastasis-associated protein that associated with OS and other cancers. Ezrin is the prototypical ERM (Ezrin/Radixin/Moesin) protein family member. ERMs function as linker proteins connecting the actin cytoskeleton and the plasma membrane. Since our initial identification of ezrin in pediatric sarcoma, an increasing understanding the role of ezrin in metastasis has emerged. Briefly, ezrin appears to allow metastatic cells to overcome a number of stresses experienced during the metastatic cascade, most notably the stress experienced as cells interact with the microenvironment of the secondary site. Cells must rapidly adapt to this environment in order to survive. Evidence now suggests a connection between ezrin expression and a variety of mechanisms linked to this important cellular adaptation including the ability of metastatic cells to initiate the translation of new proteins and to allow the efficient generation of ATP through a variety of sources. This understanding of the role of ezrin in the biology of metastasis is now sufficient to consider ezrin as an important therapeutic target in osteosarcoma patients. This chapter reviews our understanding of ezrin and the related ERM proteins in normal tissues and physiology, summarizes the expression of ezrin in human cancers and associations with clinical parameters of disease progression, reviews reports that detail a biological understanding of ezrin's role in metastatic progression, and concludes with a rationale that may be considered to target ezrin and ezrin biology in osteosarcoma.

Sphingolipid regulation of ezrin, radixin, and moesin proteins family: implications for cell dynamics

A key but poorly studied domain of sphingolipid functions encompasses endocytosis, exocytosis, cellular trafficking, and cell movement. Recently, the ezrin, radixin and moesin (ERM) family of proteins emerged as novel potent targets regulated by sphingolipids. ERMs are structural proteins linking the actin cytoskeleton to the plasma membrane, also forming a scaffold for signaling pathways that are used for cell proliferation, migration and invasion, and cell division. Opposing functions of the bioactive sphingolipid ceramide and sphingosine-1-phosphate (S1P), contribute to ERM regulation. S1P robustly activates whereas ceramide potently deactivates ERM via phosphorylation/dephosphorylation, respectively. This recent dimension of cytoskeletal regulation by sphingolipids opens up new avenues to target cell dynamics, and provides further understanding of some of the unexplained biological effects mediated by sphingolipids. In addition, these studies are providing novel inroads into defining basic mechanisms of regulation and action of bioactive sphingolipids. This review describes the current understanding of sphingolipid regulation of the cytoskeleton, it also describes the biologies in which ERM proteins have been involved, and finally how these two large fields have started to converge. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.

The expanding family of FERM proteins

Our understanding of the FERM (4.1/ezrin/radixin/moesin) protein family has been rapidly expanding in the last few years, with the result that many new physiological functions have been ascribed to these biochemically unique proteins. In the present review, we will discuss a number of new FRMD (FERM domain)-containing proteins that were initially discovered from genome sequencing but are now being established through biochemical and genetic studies to be involved both in normal cellular processes, but are also associated with a variety of human diseases.

Expression of Phosphoinositide-specific phospholipase C enzymes in human osteosarcoma cell lines

The definition of the number and nature of signal transduction pathways networking in the pathogenesis of osteosarcoma raised great interest. Intracellular calcium ions are important second messengers implicated in the control of cell death. The calcium concentration is regulated by signal transduction pathways, including the Phosphoinositides (PI) signaling. Phosphatydil inositol (4,5) bisphosphate (PIP2) is critical for many cellular activities. The levels of PIP2 are regulated by means of Phosphoinositide-specific Phospholipase C (PI-PLC) family of enzymes. We delineated the panel of expression of PI-PLC enzymes in four human osteosarcoma cell lines. In MG-63 cell line, PI-PLC β1, β2, β3, β4, γ1, γ2, δ1, δ3 and ε resulted expressed. In 143B cell line, PI-PLC β1, β2, β3, β4, γ1, γ2, δ1, δ3 and ε were expressed. In SaOS-2 cell line, PI-PLC β1, β3, β4, γ1, γ2, δ1, δ3, ε and η1. In Hs888 cell line, PI-PLC β1, β3, β4, γ1, δ1, δ3, δ4, ε and η1 the administration of U-73122 to cultures briefly modifies the levels of PI-PLC transcripts. The obtained complete expression panel of PI-PLC isoforms will be a useful tool for further functional studies about the role of the PI signal transduction pathway in osteosarcoma.

Ezrin expression and its phosphorylation in gastric carcinoma with lymphoid stroma and Epstein-Barr virus infection

Gastric carcinoma with lymphoid stroma (GCLS) is a unique variant of gastric carcinoma that represents prominent lymphocytic infiltration and is correlated with Epstein-Barr virus (EBV) infection. Ezrin expression and activation are crucial in tumor metastasis and induce cell migration of EBV-related nasopharyngeal carcinomas. Using immunohistochemical methods, the expression of total and phosphorylated ezrin (p-ezrin), Thr567, was examined in 104 GCLS cases, including 78 EBV-positive and 26 EBV-negative cases, as well as 29 non-GCLS cases. Positive ezrin expression was detected to be at markedly higher levels in GCLS compared to non-GCLS (P<0.0001). Furthermore, ezrin expression was detected to be at higher levels in EBV-positive compared to EBV-negative GCLS (P=0.0294). High expression of p-ezrin in GCLS was associated with positive lymph node metastasis (P=0.0187). In summary, these results demonstrated that ezrin overexpression is correlated with the histologic characteristics of GCLS and EBV infection. Phosphorylation of ezrin may, therefore, contribute to lymph node metastasis in GCLS.

Discovery of biomarkers for osteosarcoma by proteomics approaches

Osteosarcomas are the most common malignant bone tumors, and the identification of useful tumor biomarkers and target proteins is required to predict the clinical outcome of patients and therapeutic response as well as to develop novel therapeutic strategies. Global protein expression studies, namely, proteomic studies, can offer important clues to understanding the tumor biology that cannot be obtained by other approaches. These studies, such as two-dimensional gel electrophoresis and mass spectrometry, have provided protein expression profiles of osteosarcoma that can be used to develop novel diagnostic and therapeutic biomarkers, as well as to understand biology of tumor progression and malignancy. In this paper, a brief description of the methodology will be provided followed by a few examples of the recent proteomic studies that have generated new information regarding osteosarcomas.

The ezrin metastatic phenotype is associated with the initiation of protein translation

We previously associated the cytoskeleton linker protein, Ezrin, with the metastatic phenotype of pediatric sarcomas, including osteosarcoma and rhabdomyosarcoma. These studies have suggested that Ezrin contributes to the survival of cancer cells after their arrival at secondary metastatic locations. To better understand this role in metastasis, we undertook two noncandidate analyses of Ezrin function including a microarray subtraction of high-and low-Ezrin-expressing cells and a proteomic approach to identify proteins that bound the N-terminus of Ezrin in tumor lysates. Functional analyses of these data led to a novel and unifying hypothesis that Ezrin contributes to the efficiency of metastasis through regulation of protein translation. In support of this hypothesis, we found Ezrin to be part of the ribonucleoprotein complex to facilitate the expression of complex messenger RNA in cells and to bind with poly A binding protein 1 (PABP1; PABPC1). The relevance of these findings was supported by our identification of Ezrin and components of the translational machinery in pseudopodia of highly metastatic cells during the process of cell invasion. Finally, two small molecule inhibitors recently shown to inhibit the Ezrin metastatic phenotype disrupted the Ezrin/PABP1 association. Taken together, these results provide a novel mechanistic basis by which Ezrin may contribute to metastasis.

Advanced glycation end-products induce calpain-mediated degradation of ezrin

Advanced glycation end-products (AGEs) are important mediators of diabetic complications via incompletely understood pathways. AGEs bind to intracellular ERM proteins (ezrin, radixin and moesin) that modulate cell shape, motility, adhesion and signal transduction. AGEs bind to the N-terminal domain of ezrin but not full-length ezrin. The AGE binding site may be made accessible either by proteolysis releasing an N-terminal fragment or ezrin activation by phosphorylation. Increased intracellular calcium is a primary event in cell activation by high glucose or AGEs. Calpain activity is increased concomitantly, and ezrin is a calpain substrate. The present study assessed whether glycated proteins affect ezrin cleavage and activation in renal tubule epithelial cells. After 7 days, AGE-BSA decreased ezrin levels in MDCK renal tubular cells to 66 ± 4% of control. AGE-RNAse, ribosylated fetal bovine serum and methylglyoxal-BSA all had similar effects. The AGE-BSA-induced decrease in ezrin was abolished by calpastatin peptide, a specific calpain inhibitor, and 1,2-bis-aminophenoxyethane-tetraacetic acid acetoxymethyl ester (BAPTA-AM), a calcium chelator. Ezrin breakdown products were increased in AGE-BSA-treated cells, with a main fragment of ∼ 43 kDa. In vitro, calpain 1 cleaved recombinant human ezrin, generating breakdown fragments including an N-terminal fragment of ∼ 43 kDa. Studies with ezrin mutants showed that non-phosphorylated ezrin was more susceptible to calpain cleavage. AGE-BSA decreased phosphorylated ERM levels to 31 ± 12% in MDCK cells. Thus, AGE-BSA promotes calpain-mediated proteolysis of ezrin in MDCK cells by both increasing calpain activity and reducing phosphorylation. Therapies targeting both glycated proteins and calpain may provide protection against diabetic complications.

Dysregulation of ezrin phosphorylation prevents metastasis and alters cellular metabolism in osteosarcoma

Ezrin links the plasma membrane to the actin cytoskeleton where it plays a pivotal role in the metastatic progression of several human cancers; however, the precise mechanistic basis for its role remains unknown. Here, we define transitions between active (phosphorylated open) and inactive (dephosphorylated closed) forms of Ezrin that occur during metastatic progression in osteosarcoma. In our evaluation of these conformations we expressed C-terminal mutant forms of Ezrin that are open (phosphomimetic T567D) or closed (phosphodeficient T567A) and compared their biologic characteristics to full-length wild-type Ezrin in osteosarcoma cells. Unexpectedly, cells expressing open, active Ezrin could form neither primary orthotopic tumors nor lung metastases. In contrast, cells expressing closed, inactive Ezrin were also deficient in metastasis but were unaffected in their capacity for primary tumor growth. By imaging single metastatic cells in the lung, we found that cells expressing either open or closed Ezrin displayed increased levels of apoptosis early after their arrival in the lung. Gene expression analysis suggested dysregulation of genes that are functionally linked to carbohydrate and amino acid metabolism. In particular, cells expressing closed, inactive Ezrin exhibited reduced lactate production and basal or ATP-dependent oxygen consumption. Collectively, our results suggest that dynamic regulation of Ezrin phosphorylation at amino acid T567 that controls structural transitions of this protein plays a pivotal role in tumor progression and metastasis, possibly in part by altering cellular metabolism.

Protein alterations associated with temozolomide resistance in subclones of human glioblastoma cell lines

Temozolomide (TMZ) is the standard chemotherapeutic agent for human malignant glioma, but intrinsic or acquired chemoresistance represents a major obstacle to successful treatment of this highly lethal group of tumours. Obtaining better understanding of the molecular mechanisms underlying TMZ resistance in malignant glioma is important for the development of better treatment strategies. We have successfully established a passage control line (D54-C10) and resistant variants (D54-P5 and D54-P10) from the parental TMZ-sensitive malignant glioma cell line D54-C0. The resistant sub-cell lines showed alterations in cell morphology, enhanced cell adhesion, increased migration capacities, and cell cycle arrests. Proteomic analysis identified a set of proteins that showed gradual changes in expression according to their 50% inhibitory concentration (IC₅₀). Successful validation was provided by transcript profiling in another malignant glioma cell line U87-MG and its resistant counterparts. Moreover, three of the identified proteins (vimentin, cathepsin D and prolyl 4-hydroxylase, beta polypeptide) were confirmed to be upregulated in high-grade glioma. Our data suggest that acquired TMZ resistance in human malignant glioma is associated with promotion of malignant phenotypes, and our reported molecular candidates may serve not only as markers of chemoresistance but also as potential therapeutic targets in the treatment of TMZ-resistant human malignant glioma, providing a platform for future investigations.

Evaluation of eIF4E expression in an osteosarcoma-specific tissue microarray

The ability to define osteosarcoma (OS) patients at greatest risk for metastatic progression and nonresponsiveness to conventional therapy is currently not possible. Such biomarkers are needed to predict overall prognosis, probability of metastases at diagnosis, and response to chemotherapy. The tissue microarray (TMA) serves as a powerful tool for detecting and validating protein biomarkers across a variety of patients. We constructed a novel outcome-linked TMA to add to and address shortcomings of currently available OS tissue resources. To test the use of our TMA, we surveyed the expression of eukaryotic initiation factor 4E (eIF4E) in OS patients using immunohistochemistry. Aberrant regulation of translation initiation is a feature of many cancers. eIF4E is central to initiation of protein synthesis. Its expression and activity have been implicated in tumor formation and potentially malignant and/or metastatic progression in some carcinomas. We found that eIF4E was uniformly expressed in OS patient samples. No association was found between eIF4E and outcome in OS patients. This novel OS TMA provided a facile mechanism to assess the role of a relevant protein biomarker in OS.

Expression of the membrane-cytoskeletal linker Ezrin in salivary gland adenoid cystic carcinoma

OBJECTIVE

The aim of this study was to investigate the relationship between membrane cytoskeleton linker protein Ezrin and CD44v6, iNOS, Ki-67, and clinicopathologic characteristics, and the prognostic significance of Ezrin expression in salivary gland adenoid cystic carcinoma (SACC).

STUDY DESIGN

Immunohistochemistry and reverse-transcription polymerase chain reaction were used to quantify the expression of Ezrin, CD44v6, inducible nitric oxide synthase (iNOS), and Ki-67 in 75 primary SACCs, 25 tumor-free salivary tissues, and 2 SACC cell lines (ACC-M and ACC-2). Survival analysis was performed to find the prognostic significance of Ezrin expression.

RESULTS

Expressions of Ezrin, CD44v6, iNOS, and Ki-67 in SACC tissues, especially with distant metastasis, were significantly higher than in tumor-free tissues. Ezrin mRNA and protein levels in ACC-M cells were significantly higher than in ACC-2 cells. Ezrin, CD44v6, iNOS, and Ki-67 expressions were significantly higher in solid pattern than in cribriform and tubular patterns. Ezrin and its partners, CD44v6, iNOS, and Ki-67, were significantly related to tumor size, clinical stage, perineural and vascular invasion, and recurrence. Furthermore, Ezrin had an independent prognostic effect on overall survival.

CONCLUSIONS

The increased expression of Ezrin and its partners, CD44v6, iNOS, and Ki-67, in SACC correlated with histologic patterns, may play a role in distant metastasis, and might indicate poor clinical outcome.