Identification of a third Protein 4.1 tumor suppressor, Protein 4.1R, in meningioma pathogenesis

EPB41L3 Inhibits the Progression of Cervical Cancer Via the ERK/p38 MAPK Signaling Pathway

This study was aimed to uncover the character and potential regulatory mechanism of EPB41L3 in cervical cancer (CC). CC cells were injected into BALB/c nude mice (female) to construct a xenograft tumor model. Real-time quantitative polymerase chain reaction (qRT-PCR) and western blot were performed to evaluate the expression of EPB41L3, ERK/p38 MAPK signal markers in CC tissues and cells. Cell counting kit-8 (CCK-8) and Transwell was applied to analyze the viability, invasion, and migration of CC cell lines. EPB41L3 was substantially decreased both in CC tissues and cells. Cell viability, invasion, and migration of CC cells were reduced by overexpressing EPB41L3. Bioinformatics analysis prerdicted that EPB41L3 was strongly related to the ERK/p38 MAPK pathway. Compared with Ad-nc mice, the volume and weight of tumors and ERK/p38 MAPK signal markers were down-regulated in Ad-EPB41L3 mice. After knocking down EPB41L3 with EPB41L3 siRNA (siEPB41L3), the ERK/p38 MAPK pathway was activated. Moreover, SB203580 treatment reversed the effect of EPB41L3 silencing on the improvement in viability, migration, and invasion of CC cells. EPB41L3 suppresses the progression of CC via activating the ERK/p38 MAPK pathway. EPB41L3 may serve as an effective therapeutic target for CC.

PKR associates with 4.1R to promote anchorage-independent growth of hepatocellular carcinoma and lead to poor prognosis

RNA-dependent protein kinase (PKR) may have a positive regulatory role in controlling tumor growth and progression in hepatocellular carcinoma (HCC). However, the downstream substrates and the molecular mechanism of PKR in the growth and progression of HCC have not been clarified. In this study, mass spectrometry analysis was performed with immunoprecipitated samples, and 4.1R was identified as a protein that binds to PKR. In transfected COS7 cells, an immunoprecipitation experiment showed that 4.1R binds to wild-type PKR, but not to a kinase-deficient mutant PKR, suggesting that PKR binds to 4.1R in a kinase activity-dependent manner. In HCC cell lines, HuH7 and HepG2, the expression level of 4.1R protein was shown to be regulated by protein expression and activation of PKR. Interestingly, high expression of 4.1R, as well as PKR, is associated with a worse prognosis in HCC. PKR increased HCC cell growth in both anchorage-dependent and anchorage-independent manners, whereas 4.1R was involved in HCC cell growth only in an anchorage-independent manner, not in an anchorage-dependent manner. The rescue experiment indicated that increased anchorage-independent growth of HCC cells by PKR might be caused by 4.1R. In conclusion, PKR associates with 4.1R and promotes anchorage-independent growth of HCC. The PKR-4.1R axis might be a new therapeutic target in HCC.

Cytoskeletal Protein 4.1R in Health and Diseases

The protein 4.1R is an essential component of the erythrocyte membrane skeleton, serving as a key structural element and contributing to the regulation of the membrane's physical properties, including mechanical stability and deformability, through its interaction with spectrin-actin. Recent research has uncovered additional roles of 4.1R beyond its function as a linker between the plasma membrane and the membrane skeleton. It has been found to play a crucial role in various biological processes, such as cell fate determination, cell cycle regulation, cell proliferation, and cell motility. Additionally, 4.1R has been implicated in cancer, with numerous studies demonstrating its potential as a diagnostic and prognostic biomarker for tumors. In this review, we provide an updated overview of the gene and protein structure of 4.1R, as well as its cellular functions in both physiological and pathological contexts.

The Role of Cytoskeleton Protein 4.1 in Immunotherapy

Cytoskeleton protein 4.1 is an essential class of skeletal membrane protein, initially found in red blood cells, and can be classified into four types: 4.1R (red blood cell type), 4.1N (neuronal type), 4.1G (general type), and 4.1B (brain type). As research progressed, it was discovered that cytoskeleton protein 4.1 plays a vital role in cancer as a tumor suppressor. Many studies have also demonstrated that cytoskeleton protein 4.1 acts as a diagnostic and prognostic biomarker for tumors. Moreover, with the rise of immunotherapy, the tumor microenvironment as a treatment target in cancer has attracted great interest. Increasing evidence has shown the immunoregulatory potential of cytoskeleton protein 4.1 in the tumor microenvironment and treatment. In this review, we discuss the role of cytoskeleton protein 4.1 within the tumor microenvironment in immunoregulation and cancer development, with the intention of providing a new approach and new ideas for future cancer diagnosis and treatment.

Multifunctional protein 4.1R regulates the asymmetric segregation of Numb during terminal erythroid maturation

The asymmetric cell division of stem or progenitor cells generates daughter cells with distinct fates that balance proliferation and differentiation. Asymmetric segregation of Notch signaling regulatory protein Numb plays a crucial role in cell diversification. However, the molecular mechanism remains unclear. Here, we examined the unequal distribution of Numb in the daughter cells of murine erythroleukemia cells (MELCs) that undergo DMSO-induced erythroid differentiation. In contrast to the cytoplasmic localization of Numb during uninduced cell division, Numb is concentrated at the cell boundary in interphase, near the one-spindle pole in metaphase, and is unequally distributed to one daughter cell in anaphase in induced cells. The inheritance of Numb guides this daughter cell toward erythroid differentiation while the other cell remains a progenitor cell. Mitotic spindle orientation, critical for distribution of cell fate determinants, requires complex communication between the spindle microtubules and the cell cortex mediated by the NuMA-LGN-dynein/dynactin complex. Depletion of each individual member of the complex randomizes the position of Numb relative to the mitotic spindle. Gene replacement confirms that multifunctional erythrocyte protein 4.1R (4.1R) functions as a member of the NuMA-LGN-dynein/dynactin complex and is necessary for regulating spindle orientation, in which interaction between 4.1R and NuMA plays an important role. These results suggest that mispositioning of Numb is the result of spindle misorientation. Finally, disruption of the 4.1R-NuMA-LGN complex increases Notch signaling and decreases the erythroblast population. Together, our results identify a critical role for 4.1R in regulating the asymmetric segregation of Numb to mediate erythropoiesis.

Protein 4.1R affects photodynamic therapy for B16 melanoma by regulating the transport of 5-aminolevulinic acid

Melanoma is the most aggressive malignant tumor of skin cancer as it can grow rapidly and metastasize. Photodynamic therapy (PDT) is a promising cancer ablation method for skin tumors, although it lacks efficiency owing to factors such as tumor characteristics, delivery of photosensitizers, immune response in vivo etc. Extensive investigation of molecules that can potentially modulate treatment efficacy is required. Protein 4.1R is a cytoskeletal protein molecule. Previous studies have shown that protein 4.1R knockdown reduces PDT sensitivity in mouse embryonic fibroblast cells. However, the functional role of protein 4.1R in melanoma is unclear. In this study, we aimed to elucidate the effect of protein 4.1R on PDT for melanoma in mice and the mechanism of anti-tumor immunity. Our results indicated that CRISPR/Cas9-mediated protein 4.1R knockout promotes the proliferation, migration, and invasion of B16 cells. We further investigated the potential mechanism of protein 4.1R on tumor cell PDT sensitivity. Our results showed that protein 4.1R knockout reduced the expression of membrane transporters γ-aminobutyric acid transporter (GAT)-1 and (GAT)-2 in B16 cells, which affected 5-ALA transmembrane transport and reduced the efficiency of PDT on B16 cells. Protein 4.1R knockout downregulated the anti-tumor immune response triggered by PDT in vivo. In conclusion, our data suggest that protein 4.1R is an important regulator in PDT for tumors and may promote the progress and efficacy of melanoma treatment.

CADM1 promotes malignant features of small-cell lung cancer by recruiting 4.1R to the plasma membrane

Cell adhesion molecule 1 (CADM1), which mediates intercellular adhesion between epithelial cells, is shown to be highly expressed in small-cell lung cancer (SCLC) and to enhance tumorigenicity of SCLC cells in nude mice. Here, we investigated the molecular mechanism underlying the oncogenic role of CADM1 in SCLC. CADM1 promoted colony formation of SCLC cells in soft agar. Analysis of deletion and point mutants of the conserved protein-binding motifs in CADM1 revealed that the 4.1 protein-binding motif in the cytoplasmic domain is responsible for the promotion of colony formation. Among the actin-binding 4.1 proteins, 4.1R was the only protein whose localization to the plasma membrane is dependent on CADM1 expression in SCLC cells. Knockdown of 4.1R suppressed the colony formation enhanced by CADM1, suggesting that 4.1R is required for the oncogenic role of CADM1 in SCLC. In primary SCLC, CADM1 expression was correlated with membranous localization of 4.1R, as was observed in a SCLC cell line. Moreover, membranous co-localization of CADM1 and 4.1R was associated with more advanced tumor stage. These results suggest that the formation of CADM1-4.1R complex would promote malignant features of SCLC.

EPB41 suppresses the Wnt/β-catenin signaling in non-small cell lung cancer by sponging ALDOC

Despite advancements in therapeutic options, the overall prognosis for non-small-cell lung cancer (NSCLC) remains poor. Further exploration of the etiology and targets for novel treatments is crucial for managing NSCLC. In this study, we revealed the significant potential of EPB41 for inhibiting NSCLC proliferation, invasion and metastasis in vitro and in vivo. Consistent with its tumor suppressor role in NSCLC, the expression of EPB41 in NSCLC specimens evidently decreased compared to that in normal tissues, and low EPB41 expression was associated with poor prognoses for NSCLC patients. We further demonstrated the importance of EPB41 protein as a novel inhibitor of the Wnt signaling, which regulates β-Catenin stability, and elucidated the crucial role of the EPB41/ALDOC/GSK3β/β-Catenin axis in NSCLC. Suppression of EPB41 expression in cancer cells elevated the levels of free ALDOC protein released from the EPB41-ALDOC complex, leading to disassembly of the β-catenin destruction complex, reduced proteolytic degradation of β-catenin, elevated cytoplasmic accumulation and nuclear translocation of β-catenin, thereby activating the expression of multiple oncogenes and, thus, NSCLC pathogenesis. Our study highlights the potential of EPB41 as a future therapeutic target for lung cancer.

Comprehensive analysis and establishment of a prediction model of alternative splicing events reveal the prognostic predictor and immune microenvironment signatures in triple negative breast cancer

Background

Triple-negative breast cancer (TNBC) is widely concerning because of high malignancy and poor prognosis. There is increasing evidence that alternative splicing (AS) plays an important role in the development of cancer and the formation of the tumour microenvironment. However, comprehensive analysis of AS signalling in TNBC is still lacking and urgently needed.

Methods

Transcriptome and clinical data of 169 TNBC tissues and 15 normal tissues were obtained and integrated from the cancer genome atlas (TCGA), and an overview of AS events was downloaded from the SpliceSeq database. Then, differential comparative analysis was performed to obtain cancer-associated AS events (CAAS). Metascape was used to perform parent gene enrichment analysis based on CAAS. Unsupervised cluster analysis was performed to analyse the characteristics of immune infiltration in the microenvironment. A splicing network was established based on the correlation between CAAS events and splicing factors (SFs). We then constructed prediction models and assessed the accuracy of these models by receiver operating characteristic (ROC) curve and Kaplan–Meier survival analyses. Furthermore, a nomogram was adopted to predict the individualized survival rate of TNBC patients.

Results

We identified 1194 cancer-associated AS events (CAAS) and evaluated the enrichment of 981 parent genes. The top 20 parent genes with significant differences were mostly related to cell adhesion, cell component connection and other pathways. Furthermore, immune-related pathways were also enriched. Unsupervised clustering analysis revealed the heterogeneity of the immune microenvironment in TNBC. The splicing network also suggested an obvious correlation between SFs expression and CAAS events in TNBC patients. Univariate and multivariate Cox regression analyses showed that the survival-related AS events were detected, including some significant participants in the carcinogenic process. A nomogram incorporating risk, AJCC and radiotherapy showed good calibration and moderate discrimination.

Conclusion

Our study revealed AS events related to tumorigenesis and the immune microenvironment, elaborated the potential correlation between SFs and CAAS, established a prognostic model based on survival-related AS events, and created a nomogram to better predict the individual survival rate of TNBC patients, which improved our understanding of the relationship between AS events and TNBC.

Silencing EPB41 Gene Expression Leads to Cell Cycle Arrest, Migration Inhibition, and Upregulation of Cell Surface Antigen in DC2.4 Cells

BACKGROUND Protein 4.1R (EPB41) is the main cytoskeleton component of the erythrocyte membrane and may be involved in cell migration and adhesion. Previous research discovered overexpression of 4.1R in the thymus of patients with myasthenia gravis (MG). The protein 4.1R on dendritic cells may play a pivotal role in MG pathogenesis. This research investigated the effects of small interfering RNA 4.1R-siRNA on cell migration, cell cycle, and surface antigen expression of DC2.4 mouse dendritic cells, thus providing a new direction for the study of MG pathogenesis. MATERIAL AND METHODS Three 4.1R-specific siRNAs were designed, and the expression of 4.1R was detected by real-time PCR at the mRNA level and Western blot analysis at the protein level to select out the most efficient siRNAs. Changes in cell morphology were observed and cell migration ability was analyzed by Transwell assay. Cell cycle and surface antigen were both analyzed by flow cytometry. RESULTS The cell bodies of DC2.4 diminished, the synapses were increased, and protuberance became more obvious after being transfected with 4.1R-siRNA. After knockdown of 4.1R, cell migration ability decreased and the proportion of cells in S phase significantly increased (both P<0.05). The expression levels of MHCII, CD80, and CD86 were all increased in DC2.4 cells (all <0.05). CONCLUSIONS Silencing the expression of 4.1R in dendritic cells resulted in inhibition of migration ability, cell cycle arrest, and increase in surface antigens, which suggest that 4.1R participates in MG autoimmunity.

Identification of a Two-Gene (PML-EPB41) Signature With Independent Prognostic Value in Osteosarcoma

Background: Osteosarcoma (OSA) is the most prevalent form of malignant bone cancer and it occurs predominantly in children and adolescents. OSA is associated with a poor prognosis and highest cause of cancer-related death. However, there are a few biomarkers that can serve as reasonable assessments of prognosis.

Methods: Gene expression profiling data were downloaded from dataset GSE39058 and GSE21257 from the Gene Expression Omnibus database as well as TARGET database. Bioinformatic analysis with data integration was conducted to discover the significant biomarkers for predicting prognosis. Verification was conducted by qPCR and western blot to measure the expression of genes.

Results: 733 seed genes were selected by combining the results of the expression profiling data with hub nodes in a human protein-protein interaction network with their gene functional enrichment categories identified. Following by Cox proportional risk regression modeling, a 2-gene (PML-EPB41) signature was developed for prognostic prediction of patients with OSA. Patients in the high-risk group had significantly poorer survival outcomes than in the low-risk group. Finally, the signature was validated and analyzed by the external dataset along with Kaplan–Meier survival analysis as well as biological experiment. A molecular gene model was built to serve as an innovative predictor of prognosis for patients with OSA.

Conclusion: Our findings define novel biomarkers for OSA prognosis, which will possibly aid in the discovery of novel therapeutic targets with clinical applications.

Epithelial-specific isoforms of protein 4.1R promote adherens junction assembly in maturing epithelia

Epithelial adherens junctions (AJs) and tight junctions (TJs) undergo disassembly and reassembly during morphogenesis and pathological states. The membrane-cytoskeleton interface plays a crucial role in junctional reorganization. Protein 4.1R (4.1R), expressed as a diverse array of spliceoforms, has been implicated in linking the AJ and TJ complex to the cytoskeleton. However, which specific 4.1 isoform(s) participate and the mechanisms involved in junctional stability or remodeling remain unclear. We now describe a role for epithelial-specific isoforms containing exon 17b and excluding exon 16 4.1R (4.1R+17b) in AJs. 4.1R+17b is exclusively co-localized with the AJs. 4.1R+17b binds to the armadillo repeats 1-2 of β-catenin via its membrane-binding domain. This complex is linked to the actin cytoskeleton via a bispecific interaction with an exon 17b-encoded peptide. Exon 17b peptides also promote fodrin-actin complex formation. Expression of 4.1R+17b forms does not disrupt the junctional cytoskeleton and AJs during the steady-state or calcium-dependent AJ reassembly. Overexpression of 4.1R-17b forms, which displace the endogenous 4.1R+17b forms at the AJs, as well as depletion of the 4.1R+17b forms both decrease junctional actin and attenuate the recruitment of spectrin to the AJs and also reduce E-cadherin during the initial junctional formation of the AJ reassembly process. Expressing 4.1R+17b forms in depleted cells rescues junctional localization of actin, spectrin, and E-cadherin assembly at the AJs. Together, our results identify a critical role for 4.1R+17b forms in AJ assembly and offer additional insights into the spectrin-actin-4.1R-based membrane skeleton as an emerging regulator of epithelial integrity and remodeling.

Expression of Protein 4.1 Family in Breast Cancer: Database Mining for 4.1 Family Members in Malignancies

BACKGROUND The protein 4.1 family is a family of cytoskeletal proteins that play an important role in maintaining normal cell morphology and cell adhesion, migration, division, and intercellular signaling. The main aim of this study was to explore the prognostic significance of the protein 4.1 family in breast cancer (BC) patients and to provide new biomarkers and therapeutic targets for the diagnosis and treatment of BC. MATERIAL AND METHODS The expression of 4.1 family members in various tumor types was compared to normal controls using the ONCOMINE and GOBO databases. The prognostic significance of the 4.1 family in BC patients was determined by Kaplan-Meier Plotter. RESULTS EPB41L2 (4.1G) was expressed at higher levels in normal tissues compared with BC patients for all 4.1 family members. In survival analysis, 4.1G and EPB41 (4.1R) mRNA high expressions were associated with better survival in BC patients. Moreover, 4.1G high expression was significantly associated with longer overall survival (OS) in luminal A and protracted relapse-free survival (RFS) in luminal B subtype BC patients who received Tamoxifen treatment. In addition, high expression of each 4.1 family member also showed better prognostic value in different molecular subtypes of BC. CONCLUSIONS These results indicate that the protein 4.1 family can be regarded as novel biomarkers and potential therapeutic targets for BC. Further research is needed to explore the detailed biological functions.

The Role of Nonerythroid Spectrin αII in Cancer

Nonerythroid spectrin αII (SPTAN1) is an important cytoskeletal protein that ensures vital cellular properties including polarity and cell stabilization. In addition, it is involved in cell adhesion, cell-cell contact, and apoptosis. The detection of altered expression of SPTAN1 in tumors indicates that SPTAN1 might be involved in the development and progression of cancer. SPTAN1 has been described in cancer and therapy response and proposed as a potential marker protein for neoplasia, tumor aggressiveness, and therapeutic efficiency. On one hand, the existing data suggest that overexpression of SPTAN1 in tumor cells reflects neoplastic and tumor promoting activity. On the other hand, nuclear SPTAN1 can have tumor suppressing effects by enabling DNA repair through interaction with DNA repair proteins. Moreover, SPTAN1 cleavage products occur during apoptosis and could serve as markers for the efficacy of cancer therapy. Due to SPTAN1's multifaceted functions and its role in adhesion and migration, SPTAN1 can influence tumor growth and progression in both positive and negative directions depending on its specific regulation. This review summarizes the current knowledge on SPTAN1 in cancer and depicts several mechanisms by which SPTAN1 could impact tumor development and aggressiveness.

A 16-gene expression signature to distinguish stage I from stage II lung squamous carcinoma

The present study aimed to perform screening of a gene signature for the discrimination and prognostic prediction of stage I and II lung squamous carcinoma. A microarray meta‑analysis was performed to identify differentially expressed genes (DEGs) between stage I and II lung squamous carcinoma samples in seven microarray datasets collected from the Gene Expression Omnibus database via the MetaQC and MetaDE package in R. The important DEGs were selected according to the betweenness centrality value of the protein‑protein interaction (PPI) network. Support vector machine (SVM) analysis was performed to screen the feature genes for discrimination and prognosis. One independent dataset downloaded from The Cancer Genome Atlas was used to validate the reliability. Pathway enrichment analysis was also performed for the feature genes. A total of 924 DEGs were identified to construct a PPI network consisting of 392 nodes and 686 edges. The top 100 of the 392 nodes were selected as crucial genes to construct an SVM classifier, and a 16‑gene signature (caveolin 1, eukaryotic translation elongation factor 1γ, casein kinase 2α1, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation η, tyrosine 3‑monooxygenase/tryptophan 5‑monooxygenase activation θ, pleiotrophin, insulin receptor, insulin receptor substrate 1, 3‑phosphoinositide‑dependent protein kinase‑1, specificity protein 1, COP9 signalosome subunit 6, N‑myc downstream regulated gene 1, retinoid X receptor α, heat shock protein 90α A1, karyopherin subunit β1 and erythrocyte membrane protein band 4.1) with high discrimination accuracy was identified. This 16‑gene signature had significant prognostic value, and patients with stage II lung squamous carcinoma exhibited shorter survival rates, compared with those with stage I disease. Seven DEGs of the 16-gene signature were significantly involved in the phosphoinositide 3‑kinase‑Akt signaling pathway. The 16‑gene signature identified in the present study may be useful for stratifying the patients with stage I or II lung squamous carcinoma and predicting prognosis.

Alternative polyadenylation in a family of paralogous EPB41 genes generates protein 4.1 diversity

Alternative polyadenylation (APA) is a step in mRNA 3'-end processing that contributes to the complexity of the transcriptome by generating isoforms that differ in either their coding sequence or their 3'-untranslated regions (UTRs). The EPB41 genes, EPB41, EPB41L2, EPB41L3 and EPB41L1, encode an impressively complex array of structural adaptor proteins (designated 4.1R, 4.1G, 4.1B and 4.1N, respectively) by using alternative transcriptional promoters and tissue-specific alternative pre-mRNA splicing. The great variety of 4.1 proteins mainly results from 5'-end and internal processing of the EPB41 pre-mRNAs. Thus, 4.1 proteins can vary in their N-terminal extensions but all contain a highly homologous C-terminal domain (CTD). Here we study a new group of EPB41-related mRNAs that originate by APA and lack the exons encoding the CTD characteristic of prototypical 4.1 proteins, thereby encoding a new type of 4.1 protein. For the EPB41 gene, this type of processing was observed in all 11 human tissues analyzed. Comparative genomic analysis of EPB41 indicates that APA is conserved in various mammals. In addition, we show that APA also functions for the EPB41L2, EPB41L3 and EPB41L1 genes, but in a more restricted manner in the case of the latter 2 than it does for the EPB41 and EPB41L2 genes. Our study shows alternative polyadenylation to be an additional mechanism for the generation of 4.1 protein diversity in the already complex EPB41-related genes. Understanding the diversity of EPB41 RNA processing is essential for a full appreciation of the many 4.1 proteins expressed in normal and pathological tissues.

Protein 4.1R Influences Myogenin Protein Stability and Skeletal Muscle Differentiation

Protein 4.1R (4.1R) isoforms are expressed in both cardiac and skeletal muscle. 4.1R is a component of the contractile apparatus. It is also associated with dystrophin at the sarcolemma in skeletal myofibers. However, the expression and function of 4.1R during myogenesis have not been characterized. We now report that 4.1R expression increases during C2C12 myoblast differentiation into myotubes. Depletion of 4.1R impairs skeletal muscle differentiation and is accompanied by a decrease in the levels of myosin heavy and light chains and caveolin-3. Furthermore, the expression of myogenin at the protein, but not mRNA, level is drastically decreased in 4.1R knockdown myocytes. Similar results were obtained using MyoD-induced differentiation of 4.1R^-/- mouse embryonic fibroblast cells. von Hippel-Lindau (VHL) protein is known to destabilize myogenin via the ubiquitin-proteasome pathway. We show that 4.1R associates with VHL and, when overexpressed, reverses myogenin ubiquitination and stability. This suggests that 4.1R may influence myogenesis by preventing VHL-mediated myogenin degradation. Together, our results define a novel biological function for 4.1R in muscle differentiation and provide a molecular mechanism by which 4.1R promotes myogenic differentiation.

Integrative Functional Genomics Implicates EPB41 Dysregulation in Hepatocellular Carcinoma Risk

Genome-wide association studies (GWASs) have provided many insights into cancer genetics. However, the molecular mechanisms of many susceptibility SNPs defined by GWASs in cancer heritability and in promoting cancer risk remain elusive. New research strategies, including functional evaluations, are warranted to systematically explore truly causal genetic variants. In this study, we developed an integrative functional genomics methodology to identify cancer susceptibility SNPs in transcription factor-binding sites across the whole genome. Employing integration of functional genomic data from c-Myc cistromics, 1000 Genomes, and the TRANSFAC matrix, we successfully annotated 12 SNPs present in the c-Myc cistrome with properties consistent with modulating c-Myc binding affinity in hepatocellular carcinoma (HCC). After genotyping these 12 SNPs in 1,806 HBV-related HCC case subjects and 1,708 control subjects, we identified a HCC susceptibility SNP, rs157224G>T, in Chinese populations (T allele: odds ratio = 1.64, 95% confidence interval = 1.32-2.02; p = 5.2 × 10(-6)). This polymorphism leads to HCC predisposition through modifying c-Myc-mediated transcriptional regulation of EPB41, with the risk rs157224T allele showing significantly decreased gene expression. Based on cell proliferation, wound healing, and transwell assays as well as the mouse xenograft model, we identify EPB41 as a HCC susceptibility gene in vitro and in vivo. Consistent with this notion, we note that EPB41 expression is significantly decreased in HCC tissue specimens, especially in portal vein metastasis or intrahepatic metastasis, compared to normal tissues. Our results highlight the involvement of regulatory genetic variants in HCC and provide pathogenic insights of this malignancy via a genome-wide approach.

4.1N suppresses hypoxia-induced epithelial-mesenchymal transition in epithelial ovarian cancer cells

Protein 4.1N (4.1N) is a member of the protein 4.1 family and is essential for the regulation of cell adhesion, motility and signaling. Previous studies have suggested that 4.1N may serve a tumor suppressor role. However, the molecular mechanisms remain unclear. In the current study, the role of 4.1N in the downregulation of hypoxia‑induced factor 1α (HIF‑1α) under hypoxic conditions and therefore the suppression of hypoxia induced epithelial‑mesenchymal transition (EMT) was investigated. The data were obtained from overexpressed and knockdown 4.1N epithelial ovarian cancer (EOC) cell lines. It was identified that 4.1N was capable of regulating the sub‑cellular localization and expression levels of HIF‑1α, by which 4.1N served a dominant role in the suppression of hypoxia‑induced EMT and associated genes. Collectively, the data of the current study identified 4.1N as an inhibitor of hypoxia‑induced tumor progression in EOC cells and highlighted its potential role in EOC therapy.

Malignant progression to anaplastic meningioma: Neuropathology, molecular pathology, and experimental models

Meningioma is a common adult intracranial tumor, and while several cases are considered benign, a subset is malignant with biologically aggressive behavior and is refractory to current treatment strategies of combined surgery and radiotherapy. Anaplastic meningiomas are quite aggressive and correspond to a World Health Organization (WHO) Grade III tumor. This highly aggressive phenotype mandates the need for more efficacious therapies. Designing rational therapies for treatment will have its foundation in the biologic understanding of involved genes and molecular pathways in these types of tumors. Anaplastic meningiomas (WHO Grade III) can arise from malignant transformation of lower grade (WHO Grade I/II) tumors, however there is an incomplete understanding of specific genetic drivers of malignant transformation in these tumors. Here, the current understanding of anaplastic meningiomas is reviewed in the context of human neuropathologic specimens and small animal models.

Tumor suppressor role of protein 4.1B/DAL-1

Protein 4.1B/DAL-1 is a membrane skeletal protein that belongs to the protein 4.1 family. Protein 4.1B/DAL-1 is localized to sites of cell-cell contact and functions as an adapter protein, linking the plasma membrane to the cytoskeleton or associated cytoplasmic signaling effectors and facilitating their activities in various pathways. Protein 4.1B/DAL-1 is involved in various cytoskeleton-associated processes, such as cell motility and adhesion. Moreover, protein 4.1B/DAL-1 also plays a regulatory role in cell growth, differentiation, and the establishment of epithelial-like cell structures. Protein 4.1B/DAL-1 is normally expressed in multiple human tissues, but loss of its expression or prominent down-regulation of its expression is frequently observed in corresponding tumor tissues and tumor cell lines, suggesting that protein 4.1B/DAL-1 is involved in the molecular pathogenesis of these tumors and acts as a potential tumor suppressor. This review will focus on the structure of protein 4.1B/DAL-1, 4.1B/DAL-1-interacting molecules, 4.1B/DAL-1 inactivation and tumor progression, and anti-tumor activity of the 4.1B/DAL-1.

Protein 4.1R attenuates autoreactivity in experimental autoimmune encephalomyelitis by suppressing CD4(+) T cell activation

Immune synapse components contribute to multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) pathogenesis as they play important role in autoreactive T cell activation. Protein 4.1R, a red cell membrane cytoskeletal protein, recently was identified as an important component of immunological synapse (IS) and acted as the negative regulator of CD4(+) T cell activation. However, the pathological role of 4.1R in the MS/EAE pathogenesis is still not elucidated. In this study, we investigated the potential role of protein 4.1R in pathologic processes of EAE by using 4.1R knockout mouse model. Our results suggest that 4.1R can prevent pathogenic autoimmunity in MS/EAE progression by suppressing the CD4(+) T cell activation.

The Protein 4.1 family: hub proteins in animals for organizing membrane proteins

Proteins of the 4.1 family are characteristic of eumetazoan organisms. Invertebrates contain single 4.1 genes and the Drosophila model suggests that 4.1 is essential for animal life. Vertebrates have four paralogues, known as 4.1R, 4.1N, 4.1G and 4.1B, which are additionally duplicated in the ray-finned fish. Protein 4.1R was the first to be discovered: it is a major mammalian erythrocyte cytoskeletal protein, essential to the mechanochemical properties of red cell membranes because it promotes the interaction between spectrin and actin in the membrane cytoskeleton. 4.1R also binds certain phospholipids and is required for the stable cell surface accumulation of a number of erythrocyte transmembrane proteins that span multiple functional classes; these include cell adhesion molecules, transporters and a chemokine receptor. The vertebrate 4.1 proteins are expressed in most tissues, and they are required for the correct cell surface accumulation of a very wide variety of membrane proteins including G-Protein coupled receptors, voltage-gated and ligand-gated channels, as well as the classes identified in erythrocytes. Indeed, such large numbers of protein interactions have been mapped for mammalian 4.1 proteins, most especially 4.1R, that it appears that they can act as hubs for membrane protein organization. The range of critical interactions of 4.1 proteins is reflected in disease relationships that include hereditary anaemias, tumour suppression, control of heartbeat and nervous system function. The 4.1 proteins are defined by their domain structure: apart from the spectrin/actin-binding domain they have FERM and FERM-adjacent domains and a unique C-terminal domain. Both the FERM and C-terminal domains can bind transmembrane proteins, thus they have the potential to be cross-linkers for membrane proteins. The activity of the FERM domain is subject to multiple modes of regulation via binding of regulatory ligands, phosphorylation of the FERM associated domain and differential mRNA splicing. Finally, the spectrum of interactions of the 4.1 proteins overlaps with that of another membrane-cytoskeleton linker, ankyrin. Both ankyrin and 4.1 link to the actin cytoskeleton via spectrin, and we hypothesize that differential regulation of 4.1 proteins and ankyrins allows highly selective control of cell surface protein accumulation and, hence, function. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé

Diagnostic and molecular pathology of meningiomas

This article will review the neuropathology of meningiomas. From the neurosurgeon's point of view, accurate neuropathological diagnosis will play an increasingly important role in clinical practice. Predicting an individual patient's prognosis will become ever more important with the advent of various new radiotherapeutic/radiosurgical modalities. Defining the optimal treatment for nonbenign meningiomas requires a robust and reproducible diagnosis. This review will therefore not only describe classical radiological and histopathological diagnosis, but will also focus on the emerging field of molecular neuropathology. Implementing these advances in our daily clinical routine holds the promise of improving diagnostic accuracy.

Defective expression of Protein 4.1N is correlated to tumor progression, aggressive behaviors and chemotherapy resistance in epithelial ovarian cancer

OBJECTIVE

Protein 4.1N (4.1N) is a member of the Protein 4.1 family that is involved in cellular processes such as cell adhesion, migration and signaling. In this study, we evaluated the expression of 4.1N protein and its potential roles in epithelial ovarian cancer (EOC) tumorigenesis and progression.

METHODS

4.1N protein expression was investigated in a total of 280 samples including 74 normal tissues, 35 benign, 30 borderline and 141 malignant epithelial ovarian tumors by immunohistochemistry. Correlation between 4.1N expression levels and clinicopathologic features was statistically analyzed. The expression of 4.1N in EOC cell lines was examined by western blotting.

RESULTS

Immunohistochemistry analysis revealed that, although there was no loss of 4.1N expression in normal tissues and benign tumors, absence of Protein 4.1N was significantly more common in EOCs (44.0%) than in borderline tumors (3.3%) (p<0.001). Furthermore, loss or decreased expression of 4.1N protein expression was correlated with malignant potential of the tumors (14.3% in benign tumors, 56.7% in borderline tumors and 92.9% in malignancy) (p<0.001). In EOC samples, loss of 4.1N protein was significantly associated with advanced-stage (p=0.004), ascites (p=0.009), omental metastasis (p=0.018), suboptimal debulking (p=0.024), poorly histological differentiation (p=0.009), high-grade serous carcinoma (p=0.001), short progression-free-survival (p=0.018) and poor chemosensitivity to first-line chemotherapy (p=0.029). Moreover, western blotting analysis revealed that expression of 4.1N protein was lost in 4/8 (50%) EOC cell lines.

CONCLUSIONS

4.1N protein expression level was significantly decreased during malignant transformation of epithelial ovarian tumors and that loss of 4.1N expression was closely correlated to poorly differentiated and biologically aggressive EOCs.

Global DNA methylation screening of liver in piperonyl butoxide-treated mice in a two-stage hepatocarcinogenesis model

Disruptive epigenetic gene control has been shown to be involved in carcinogenesis. To identify key molecules in piperonyl butoxide (PBO)-induced hepatocarcinogenesis, we searched hypermethylated genes using CpG island (CGI) microarrays in non-neoplastic liver cells as a source of proliferative lesions at 25 weeks after tumor promotion with PBO using mice. We further performed methylation-specific polymerase chain reaction (PCR), real-time reverse transcription PCR, and immunohistochemical analysis in PBO-promoted liver tissues. Ebp4.1, Wdr6 and Cmtm6 increased methylation levels in the promoter region by PBO promotion, although Cmtm6 levels were statistically non-significant. These results suggest that PBO promotion may cause altered epigenetic gene regulation in non-neoplastic liver cells surrounding proliferative lesions to allow the facilitation of hepatocarcinogenesis. Both Wdr6 and Cmtm6 showed decreased expression in non-neoplastic liver cells in contrast to positive immunoreactivity in the majority of proliferative lesions produced by PBO promotion. These results suggest that both Wdr6 and Cmtm6 were spared from epigenetic gene modification in proliferative lesions by PBO promotion in contrast to the hypermethylation-mediated downregulation in surrounding liver cells. Considering the effective detection of proliferative lesions, these molecules could be used as detection markers of hepatocellular proliferative lesions and played an important role in hepatocarcinogenesis.

Reduced expression of ELAVL4 in male meningioma patients

Meningioma is a frequently occurring tumor of the central nervous system. Among many genetic alternations, the loss of the short arm of chromosome 1 is the second most frequent chromosomal abnormality observed in these tumors. Here, we focused on the previously described and well-established minimal deletion regions of chromosome 1. In accordance with the Knudson suppressor theory, we designed an analysis of putative suppressor genes localized in the described minimal deletion regions. The purpose was to determine the molecular background of the gender-specific occurrence of meningiomas. A total of 149 samples were examined for loss of heterozygosity (LOH). In addition, 57 tumor samples were analyzed using real-time polymerase chain reaction. We examined the association between the expression of selected genes and patient age, gender, tumor grade and presence of 1p loss. Furthermore, we performed an analysis of the most stable internal control for real-time analysis in meningiomas. LOH analysis revealed gender-specific discrepancies in the frequency of 1p aberrations. Moreover, statistical correlation between the gene expression level and gender was significant for the ELAVL4 gene as we found it to be lower in males than in females. We conclude that meningiomas present different features depending on patient gender. We suggest that ELAVL4 can be involved in the pathogenesis of meningiomas in male patients.

The membrane-cytoskeletal protein 4.1N is involved in the process of cell adhesion, migration and invasion of breast cancer cells

Protein 4.1N belongs to the protein 4.1 superfamily that links transmembrane proteins to the actin cytoskeleton. Recent evidence has shown that protein 4.1 is important in tumor suppression. However, the functions of 4.1N in the metastasis of breast cancer are largely unknown. In the present study, MCF-7, T-47D and MDA-MB-231 breast cancer cell lines with various metastatic abilities were employed. Protein 4.1N was found to be expressed in poorly metastatic MCF-7 and middle metastatic T-47D cell lines, and was predominantly associated with cell-cell junctions. However, no 4.1N expression was detected in the highly metastatic MDA-MB-231 cells. Moreover, re-expression of 4.1N in MDA-MB-231 cells inhibited cell adhesion, migration and invasion. The results suggest that protein 4.1N is a negative regulator of cell metastasis in breast cancer.

FERM-containing protein FRMD5 is a p120-catenin interacting protein that regulates tumor progression

FERM family proteins have been known to play an important role in tumor progression. FERM-domain containing protein 5 (FRMD5), a novel putative cytoskeletal protein, is an unknown function protein. Here, we reported that FRMD5 localized at the cell adherens junction and formed a molecular complex with p120-catenin through its C-terminal region. Functionally, we found that knockdown of endogenous FRMD5 promotes lung cancer cell migration and invasion in vitro as well as tumor growth in vivo, suggesting a tumor suppressive effect. These findings indicated that FRMD5 may play a role in p120-catenin-based cell-cell contact and is involved in the regulation of tumor progression.

Sunitinib targets PDGF-receptor and Flt3 and reduces survival and migration of human meningioma cells

The multitargeted tyrosine-kinase inhibitor sunitinib is a highly effective anti-angiogenic and cytostatic agent in the therapy of various tumours. While malignant gliomas have been shown to be responsive to sunitinib, detailed studies analysing human meningiomas are missing. We therefore analysed the effects of sunitinib in two benign (BenMen-1, HBL52) and two malignant (IOMM-Lee, KT21MG) human meningioma cell lines and found that DNA synthesis was significantly (p ≤ 0.001) inhibited following 1, 2 or 5 μM sunitinib, with IC(50) values between 2 and 5 μM in all cell lines. This effect was associated with a G(2)M-arrest at 10 μM for BenMen-1, HBL52 and IOMM-Lee, and 20 μM in KT21MG cells. Nuclear bisbenzimide staining revealed chromatin condensation following treatment with sunitinib concentrations of 10 μM or higher. Corresponding, cell viability assays showed a significant (p ≤ 0.001) short term decrease of viable cells (24h) only for high sunitinib concentrations with IC(50)-values between 10 and 20 μM. However, pre-irradiated meningioma cells (5 Gy) showed a sensitivity shift towards IC(50)-values around 5 μM sunitinib. We also found that 5 μM strongly reduced meningioma cell migration in vitro. Western blot analyses showed abolished platelet derived growth factor receptor (PDGFR)-autophosphorylation after sunitinib. Interestingly, the drug also inhibited the autophosphorylation of the receptor tyrosine kinase fms-like tyrosine kinase 3 (Flt3) in a dose-dependent manner. Taken together, the present data show that micromolar sunitinib has strong cytostatic and anti-migratory effects on human meningioma cells.

The spectrin-ankyrin-4.1-adducin membrane skeleton: adapting eukaryotic cells to the demands of animal life

The cells in animals face unique demands beyond those encountered by their unicellular eukaryotic ancestors. For example, the forces engendered by the movement of animals places stresses on membranes of a different nature than those confronting free-living cells. The integration of cells into tissues, as well as the integration of tissue function into whole animal physiology, requires specialisation of membrane domains and the formation of signalling complexes. With the evolution of mammals, the specialisation of cell types has been taken to an extreme with the advent of the non-nucleated mammalian red blood cell. These and other adaptations to animal life seem to require four proteins--spectrin, ankyrin, 4.1 and adducin--which emerged during eumetazoan evolution. Spectrin, an actin cross-linking protein, was probably the earliest of these, with ankyrin, adducin and 4.1 only appearing as tissues evolved. The interaction of spectrin with ankyrin is probably a prerequisite for the formation of tissues; only with the advent of vertebrates did 4.1 acquires the ability to bind spectrin and actin. The latter activity seems to allow the spectrin complex to regulate the cell surface accumulation of a wide variety of proteins. Functionally, the spectrin-ankyrin-4.1-adducin complex is implicated in the formation of apical and basolateral domains, in aspects of membrane trafficking, in assembly of certain signalling and cell adhesion complexes and in providing stability to otherwise mechanically fragile cell membranes. Defects in this complex are manifest in a variety of hereditary diseases, including deafness, cardiac arrhythmia, spinocerebellar ataxia, as well as hereditary haemolytic anaemias. Some of these proteins also function as tumor suppressors. The spectrin-ankyrin-4.1-adducin complex represents a remarkable system that underpins animal life; it has been adapted to many different functions at different times during animal evolution.

Cytoskeletal protein 4.1R negatively regulates T-cell activation by inhibiting the phosphorylation of LAT

Protein 4.1R (4.1R) was first identified in red cells where it plays an important role in maintaining mechanical stability of red cell membrane. 4.1R has also been shown to be expressed in T cells, but its function has been unclear. In the present study, we use 4.1R-deficient mice to explore the role of 4.1R in T cells. We show that 4.1R is recruited to the immunologic synapse after T cell-antigen receptor (TCR) stimulation. We show further that CD4+ T cells of 4.1R-/- mice are hyperactivated and that they displayed hyperproliferation and increased production of interleukin-2 (IL-2) and interferon gamma (IFNgamma). The hyperactivation results from enhanced phosphorylation of LAT and its downstream signaling molecule ERK. The 4.1R exerts its effect by binding directly to LAT, and thereby inhibiting its phosphorylation by ZAP-70. Moreover, mice deficient in 4.1R display an elevated humoral response to immunization with T cell-dependent antigen. Thus, we have defined a hitherto unrecognized role for 4.1R in negatively regulating T-cell activation by modulating intracellular signal transduction.

Detergent resistant membrane-associated IDE in brain tissue and cultured cells: Relevance to Abeta and insulin degradation

Background

Insulin degrading enzyme (IDE) is implicated in the regulation of amyloid β (Aβ) steady-state levels in the brain, and its deficient expression and/or activity may be a risk factor in sporadic Alzheimer's disease (AD). Although IDE sub-cellular localization has been well studied, the compartments relevant to Aβ degradation remain to be determined.

Results

Our results of live immunofluorescence, immuno gold electron-microscopy and gradient fractionation concurred to the demonstration that endogenous IDE from brain tissues and cell cultures is, in addition to its other localizations, a detergent-resistant membrane (DRM)-associated metallopeptidase. Our pulse chase experiments were in accordance with the existence of two pools of IDE: the cytosolic one with a longer half-life and the membrane-IDE with a faster turn-over. DRMs-associated IDE co-localized with Aβ and its distribution (DRMs vs. non-DRMs) and activity was sensitive to manipulation of lipid composition in vitro and in vivo. When IDE was mis-located from DRMs by treating cells with methyl-β-cyclodextrin (MβCD), endogenous Aβ accumulated in the extracellular space and exogenous Aβ proteolysis was impaired. We detected a reduced amount of IDE in DRMs of membranes isolated from mice brain with endogenous reduced levels of cholesterol (Chol) due to targeted deletion of one seladin-1 allele. We confirmed that a moderate shift of IDE from DRMs induced a substantial decrement on IDE-mediated insulin and Aβ degradation in vitro.

Conclusion

Our results support the notion that optimal substrate degradation by IDE may require its association with organized-DRMs. Alternatively, DRMs but not other plasma membrane regions, may act as platforms where Aβ accumulates, due to its hydrophobic properties, reaching local concentration close to its Km for IDE facilitating its clearance. Structural integrity of DRMs may also be required to tightly retain insulin receptor and IDE for insulin proteolysis. The concept that mis-location of Aβ degrading proteases away from DRMs may impair the physiological turn-over of Aβ in vivo deserves further investigation in light of therapeutic strategies based on enhancing Aβ proteolysis in which DRM protease-targeting may need to be taken into account.

Potential role of EPB41L3 (protein 4.1B/Dal-1) as a target for treatment of advanced prostate cancer

BACKGROUND

Loss of erythrocyte membrane protein band 4.1-like 3 (EPB41L3; aliases: protein 4.1B, differentially expressed in adenocarcinoma of the lung-1 (Dal-1)) expression has been implicated in tumor progression.

OBJECTIVE

To evaluate literature describing the role of EPB41L3 in tumorigenesis and metastasis, and to consider whether targeting this gene would be useful in the treatment of prostate cancer.

METHODS

A literature review of studies describing EPB41L3 and its aliases was conducted. Online databases (NCBI, SwissProt) were also interrogated to collect further data.

RESULTS/CONCLUSION

A growing body of evidence supports a role for loss of EPB41L3 in tumor progression, including in prostate cancer. Therapeutic strategies that could be harnessed to upregulate EPB41L3 gene expression in prostate cancer cells are currently being developed.

Molecular pathogenesis of adult brain tumors and the role of stem cells

Primary brain tumors consist of neoplasms with varied molecular defects, morphologic phenotypes, and clinical outcomes. The genetic and signaling abnormalities involved in tumor initiation and progression of the most prevalent adult primary brain tumors, including gliomas, meningiomas, and medulloblastomas, are described in this article. The current understanding of the cell-of-origin of these neoplasms is reviewed, which suggests that the malignant phenotype is propelled by cells with stem-like qualities. A comprehensive understanding of the molecular basis of transformation and the cell-of-origin of these neoplasms will enable the formulation of more targeted treatment alternatives that could improve survival and quality of life.

The merlin interacting proteins reveal multiple targets for NF2 therapy

The neurofibromatosis 2 (NF2) tumor suppressor protein merlin is commonly mutated in human benign brain tumors. The gene altered in NF2 was located on human chromosome 22q12 in 1993 and the encoded protein named merlin and schwannomin. Merlin has homology to ERM family proteins, ezrin, radixin, and moesin, within the protein 4.1 superfamily. In efforts to determine merlin function several groups have discovered 34 merlin interacting proteins, including ezrin, radixin, moesin, CD44, layilin, paxillin, actin, N-WASP, betaII-spectrin, microtubules, TRBP, eIF3c, PIKE, NHERF, MAP, RalGDS, RhoGDI, EG1/magicin, HEI10, HRS, syntenin, caspr/paranodin, DCC, NGB, CRM1/exportin, SCHIP1, MYPT-1-PP1delta, RIbeta, PKA, PAK (three types), calpain and Drosophila expanded. Many of the proteins that interact with the merlin N-terminal domain also bind ezrin, while other merlin interacting proteins do not bind other members of the ERM family. Merlin also interacts with itself. This review describes these proteins, their possible roles in NF2, and the resultant hypothesized merlin functions. Review of all of the merlin interacting proteins and functional consequences of losses of these interactions reveals multiple merlin actions in PI3-kinase, MAP kinase and small GTPase signaling pathways that might be targeted to inhibit the proliferation of NF2 tumors.

Merlin Expression in Secretory Meningiomas: Evidence of an NF2-independent Pathogenesis?

One of the most common chromosomal regions implicated in the meningiomas tumorigenesis is 22q12 where the neurofibromatosis 2 (NF2) gene resides. The NF2 tumor-suppressor gene encodes for the merlin/schwannomin protein, which is responsible for the inherited disease neurofibromatosis 2. NF2 gene mutations predominantly occur in transitional and fibroblastic meningiomas, whereas the meningothelial variant is less affected. Secretory meningioma is an infrequent meningioma subtype. Its most typical morphologic feature is the presence of intracytoplasmic or extracytoplasmic round hyaline, eosinophilic, and periodic acid Shiff-positive bodies in a lesion frequently otherwise classifiable as meningothelial meningioma. This study reviews the immunohistochemical merlin expression in 14 consecutive secretory meningiomas. Our purpose was to investigate if secretory meningiomas, analogous to meningothelial meningiomas, follow a molecular route of pathogenesis independent of the neurorofibromatosis 2 gene-associated pathway. All meningiomas showed positive immunocoloration involving the majority of the hyaline inclusions and secretory cells; in 12 (86%) meningiomas, a positive immunoreaction was also documented in nonsecretory tumoral cells. Our results may indicate a molecular, besides morphologic, similarity between secretory and meningothelial meningiomas: the almost constant merlin immunohistochemical expression in our series gives evidence for a possible NF2 gene-independent pathogenesis in secretory meningiomas.

NF2 gene expression in sporadic meningiomas: Relation to grades or histotypes real time-PCR study

One of the most common regions involved in the meningiomas tumorigenesis is chromosome 22q where the NF2 gene resides. The deficiency or loss of the NF2 gene product, merlin/schwannomin, plays a role in tumor development and metastatization. Conflicting results have been reported on the prognostic value of merlin in meningiomas. Several studies have indicated NF2 gene inactivation as an early tumorigenic event unrelated to the histological grade or clinical behavior. On the contrary, the NF2 gene alteration rate differs between the different histotypes. A pathogenesis independent from the NF2 gene has been suggested in meningothelial meningiomas. In the present work, we studied the NF2 gene expression through real time-PCR (RT-PCR) in 30 meningiomas. The average of the NF2 gene expression of all meningiomas was considered as reference value. The average of expression of WHO grade I and II meningiomas was higher than the average of all meningiomas, whereas that of WHO grade III meningiomas was lower. When we compared the NF2 gene expression in the different meningioma grades we did not note a significant difference (P = 0.698) despite the tendency to decrease from grade I to grade III. The average expression of meningothelial meningiomas was higher than the reference value, and that of non-meningothelial meningiomas was lower. The difference in NF2 gene expression between meningothelial and non-meningothelial meningiomas was statistically significant (P = 0.013). Our data supports the finding that alterations in NF2 gene alteration are histotype related but not grade related.

FRMD3, a novel putative tumour suppressor in NSCLC

Lung cancer including non-small cell lung carcinoma (NSCLC) represents a leading cause of cancer death in Western countries. Yet, understanding its pathobiology to improve early diagnosis and therapeutic strategies is still a major challenge of today's biomedical research. We analyzed a set of differentially regulated genes that were identified in skin cancer by a comprehensive microarray study, for their expression in NSCLC. We found that ferm domain containing protein 3 (FRMD3), a member of the protein 4.1 superfamily, is expressed in normal lung tissue but silenced in 54 out of 58 independent primary NSCLC tumours compared to patient-matched normal lung tissue. FRMD3 overexpression in different epithelial cell lines resulted in a decreased clonogenicity as measured by colony formation assay. Although cell attachment capabilities and cell proliferation rate remained unchanged, this phenotype was most likely owing to induced apoptosis. Our data identify FRMD3 as a novel putative tumour suppressor gene suggesting an important role in the origin and progression of lung cancer.

Protein 4.1R self-association: identification of the binding domain

Erythroid protein 4.1 (4.1R) stabilizes the spectrin-actin network and anchors it to the plasma membrane. To contribute to the characterization of non-erythroid protein 4.1R, we used sedimentation, pull-down and co-immunoprecipitation assays to investigate the ability of protein 4.1R to establish inter-/intra-molecular associations. We demonstrated that the small 4.1R isoforms of 60 kDa (4.1R60), but not the larger isoforms of 80 and 135 kDa (4.1R80 and 4.1R135), were self-associated, and that a domain contained in all 4.1R isoforms, the core region, was responsible for 4.1R self-association. Results from denaturing-renaturing experiments, in which an initially non-self-associated 4.1R80 isoform became self-associated, suggested that an initially hidden core region was subsequently exposed. This hypothesis was supported by results from pull-down assays, which showed that the core region interacted with the N-terminal end of the FERM (4.1, ezrin, radixin, moesin) domain that is present in 4.1R80 and 4.1R135 isoforms but absent from 4.1R60 isoforms. Consistently, 4.1R80 isoforms bound neither to each other nor to 4.1R60 isoforms. We propose that 4.1R60 isoforms are constitutively self-associated, whereas 4.1R80 and 4.1R135 self-association is prevented by intramolecular interactions.

Histological classification and molecular genetics of meningiomas

Meningiomas account for up to 30% of all primary intracranial tumours. They are histologically classified according to the World Health Organization (WHO) classification of tumours of the nervous system. Most meningiomas are benign lesions of WHO grade I, whereas some meningioma variants correspond with WHO grades II and III and are associated with a higher risk of recurrence and shorter survival times. Mutations in the NF2 gene and loss of chromosome 22q are the most common genetic alterations associated with the initiation of meningiomas. With increase in tumour grade, additional progression-associated molecular aberrations can be found; however, most of the relevant genes are yet to be identified. High-throughput techniques of global genome and transcriptome analyses and new meningioma models provide increasing insight into meningioma biology and will help to identify common pathogenic pathways that may be targeted by new therapeutic approaches.

Lack of genetic and epigenetic changes in meningiomas without NF2 loss

Approximately 60% of sporadic meningiomas are caused by inactivation of the NF2 tumour suppressor gene. The causative gene for the remaining meningiomas is unknown. Previous studies have shown that these tumours have no recurrent karyotypic abnormalities. They differ from their NF2-related counterparts in that they are more often of the meningothelial subtype and are located preferentially in the anterior skull base. To gain more insight into the aetiology of these tumours, we studied genetic and epigenetic alterations in 25 meningiomas without NF2 involvement. We first established a genome-wide allelotype using 3 microsatellite markers per chromosome arm. Loss of heterozygosity (LOH) was detected at a low frequency and no indication for the location of putative tumour suppressor genes could be established. We next screened the subtelomeric regions by using 2-3 polymorphic markers close to each telomere. Again no evidence for LOH of a particular chromosome arm was obtained, and no LOH was found in the genomic regions containing the NF2-related ERM family members ezrin and radixin, DAL-1, protein 4.1R, and TSLC1. Mutations in the X-chromosome based family member, moesin, were analysed by SSCP and were not detected. Microsatellite instability was studied using 6 commonly used markers but none of these was altered in any meningioma. Methylation was detected in 5 of 16 genes (NF2, p14(ARF), CDH1, BRCA1, RB1) previously shown to be silenced in a variety of tumour types. However, methylation percentages for these genes were generally higher in a group of NF2-related meningiomas, with the exception of the BRCA1 gene. The NF2 gene was methylated in only 1 of 21 tumours. In conclusion, meningiomas with an intact NF2 gene have a normal karyotype and no obvious genetic or epigenetic aberrations, suggesting that the gene(s) involved in the pathogenesis of these tumours are altered by smaller events than can be detected with the techniques used in our study.

Loss of the putative tumor suppressor band 4.1B/Dal1 gene is dispensable for normal development and does not predispose to cancer

The band 4.1 proteins are cytoskeletal proteins, harboring a conserved FERM domain highly homologous to the N-terminal FERM domain of ezrin, radixin, moesin, and merlin. Recently, a truncated form of the 4.1B protein, termed Dal-1, was identified in a screen as down regulated in adenocarcinoma of the lung and was mapped to chromosome 18p11.3, which is lost in 38% of primary non-small cell lung carcinoma tumors. Analysis of several meningiomas has shown that Dal-1 expression was lost in 76% of the tumors. To further elucidate the function of the 4.1B/Dal-1 gene in development and tumorigenesis we generated mice deficient for this allele. The 4.1B/Dal-1 null mice develop normally and are fertile. Rates of cellular proliferation and apoptosis in brain, mammary, and lung tissues from the 4.1B/Dal-1 null mice were indistinguishable from those seen with wild-type mice. Aging studies indicate that these mice do not have a propensity to develop tumors. Analysis of fibroblasts from these mice demonstrated that the growth characteristics and kinetics of these cells were not different from those of cells from the wild-type mice. These findings indicate that the 4.1B gene is not required for normal development and that 4.1B/Dal-1 does not function as a tumor suppressor gene.

Integrative genomic analysis identifies NDRG2 as a candidate tumor suppressor gene frequently inactivated in clinically aggressive meningioma

Although meningiomas are common central nervous system tumors, little is known about the genetic events responsible for malignant progression. In this study, we employed gene expression profiling to identify transcripts whose expression was lost in anaplastic (WHO grade III) versus benign (WHO grade I) meningioma. Approximately 40% of genes down-regulated in anaplastic meningioma were localized to chromosomes 1p and 14q. One specific gene located at 14q11.2, NDRG2, was consistently down-regulated in grade III meningioma, a finding which we validated at both the transcript and protein levels in independent sets of clinically and pathologically diverse meningiomas. Loss of NDRG2 expression was also seen in a subset of lower-grade meningiomas, including atypical meningiomas (WHO grade II) with clinically aggressive behavior. Furthermore, we found that the loss of NDRG2 expression was significantly associated with hypermethylation of the NDRG2 promoter. Collectively, these data identify NDRG2 as the first specific candidate tumor suppressor gene on chromosome 14q that is inactivated during meningioma progression. In addition, these findings highlight the utility of combining genomic, epigenetic, and expression data to identify clinically significant tumor biomarkers, and suggest that NDRG2 expression will be a useful and functionally relevant biomarker to predict aggressive behavior in patients with meningioma.

Protein 4.1B expression is induced in mammary epithelial cells during pregnancy and regulates their proliferation

4.1B is a member of the protein 4.1 superfamily of proteins that link transmembrane proteins to the actin cytoskeleton. The 4.1B gene localizes to chromosome 18p11.3, which undergoes loss of heterozygosity in mammary tumors. Here, we examine the expression of 4.1B in murine mammary epithelium and find that 4.1B is dramatically upregulated in mammary epithelial cells during pregnancy when there is extensive cell proliferation. In contrast, 4.1B is not expressed in virgin, lactating, or involuting mammary epithelium. To examine the consequence of 4.1B loss on mammary epithelial cell proliferation, we analysed mammary glands in 4.1B-null mice. 4.1B loss results in a significant increase in mammary epithelial cell proliferation during pregnancy, but has no effect on mammary epithelial cell proliferation, in virgin or involuting mice. Furthermore, we show that 4.1B inhibits the proliferation of mammary epithelial cell lines by inducing a G1 cell cycle arrest, characterized by decreased cyclin A expression and reduced Rb phosphorylation, and accompanied by reduced erbB2 phosphorylation. This cell cycle arrest does not involve alterations in the activities of MAPK, JNK, or Akt. Collectively, our findings demonstrate that 4.1B regulates mammary epithelial cell proliferation during pregnancy and suggest that its loss may influence mammary carcinoma pathogenesis in multiparous women.

GADD45A and EPB41 as tumor suppressor genes in meningioma pathogenesis

Deletions of 1p occur in approximately 30% of meningiomas. Based on loss of heterozygosity (LOH) analysis, two regions on 1p have been suspected to be carriers of tumor suppressor genes. We chose the GADD45A and EPB41 genes as tumor suppressor candidates based on their function and chromosomal localization. We analyzed 19 cases of meningioma with LOH of 1p by means of sequencing of the GADD45A gene and Western blotting of the GADD45a protein. Twenty cases of meningioma without 1p LOH were also analyzed by Western blotting to find out if changes of the GADD45a protein expression occurred. Nineteen samples with 1p LOH (12 grade I; 7 grade II, WHO classification) and 20 samples without 1p LOH (18 grade I; 2 grade II) were also analyzed by means of real-time polymerase chain reaction to find abnormalities in EPB41 mRNA levels in meningioma. LOH analysis was performed using seven microsatellite markers: D1S508 (1p36.2), D1S199 (1p36.1) D1S2734 (1p36.1), D1S2720 (1p34), D1S197 (1p32), D1S162 (1p32), D1S429 (1p11). LOH analysis confirmed previously described localization of putative tumor suppressor genes on 1p and involvement in meningioma pathogenesis (1p36 and 1p32). The open reading frame of GADD45A and intron splicing sites showed neither mutations nor polymorphisms. GADD45a protein molecular weight and expression level were unaltered in meningiomas with and without 1p LOH. We conclude that the GADD45A gene is not involved in meningioma tumorigenesis. EPB41 gene expression was unchanged in all analyzed meningiomas. This suggests that involvement of the EPB41 gene (4.1R protein) in meningioma pathogenesis should be reconsidered.

Alterations of protein 4.1 family members in ependymomas: a study of 84 cases

Ependymomas are common pediatric and adult CNS malignancies with a wide biologic spectrum that is often hard to predict using classic prognostic variables. The molecular pathogenesis is also poorly understood and few reproducible genetic alterations have been identified. The most common genetic alteration has been the loss of the Protein 4.1 family member, NF2, predominantly in spinal ependymomas. In contrast, a pilot study suggested that 4.1B deletions might be more common in intracranial ependymomas. These findings prompted us to study Protein 4.1 family members (NF2, 4.1B, 4.1R, 4.1G) in a larger cohort of 84 ependymomas (51 intracranial and 33 spinal; 11 WHO grade I, 43 grade II, 30 grade III). Fluorescence in situ hybridization was performed using NF2, 4.1B, 4.1R and 4.1G probes and immunohistochemical staining was performed in a subset using merlin, Protein 4.1B and Protein 4.1R antibodies. Additionally, frozen tissue from nine ependymomas (four intracranial and five spinal) was obtained for Western blot analysis for merlin, 4.1B and 4.1R expression. The majority of cases harbored one or more detectable genetic alterations, but we found that 4.1B gene deletions and 4.1R loss of expression were statistically more common in the pediatric vs adult, intracranial vs spinal, and grade III vs grade I/II subsets (P-values of 0.038 to <0.001). Also, 4.1G deletions were seen in 11/27 (41%) patients who either died of disease or had residual/recurrent tumor vs 5/41 patients with no evidence of disease at last follow-up (P=0.009). We conclude that alterations of Protein 4.1 family members are common in ependymal tumors and that specific alterations are associated with distinct clinicopathologic subsets.