FAK activation and the role of epithelial membrane protein 2 (EMP2) in collagen gel contraction

The impact of early pregnancy metabolic disorders on pregnancy outcome and the specific mechanism

Miscarriage is the most common complication of pregnancy. The most common causes of early miscarriage are chromosomal abnormalities of the embryo, maternal endocrine abnormalities, organ malformations, and abnormal immune factors. Late miscarriages are mostly caused by factors such as cervical insufficiency. However, the causes of 50% of miscarriages remain unknown. Recently, increasing attention has been given to the role of metabolic abnormalities in miscarriage. In this review, we mainly discuss the roles of four major metabolic pathways (glucose, lipid, and amino acid metabolism, and oxidation‒reduction balance) in miscarriage and the metabolism-related genes that lead to metabolic disorders in miscarriage. Depending on aetiology, the current treatments for miscarriage include hormonal and immunological drugs, as well as surgery, while there are few therapies for metabolism. Therefore, we also summarize the drugs for metabolism-related targets. The study of altered metabolism underlying miscarriage not only helps us to understand the mechanisms involved in miscarriage but also provides an important basis for clinical research on new therapies.

Exploring the Past, Present, and Future of Anti-Angiogenic Therapy in Glioblastoma

Glioblastoma, a WHO grade IV astrocytoma, constitutes approximately half of malignant tumors of the central nervous system. Despite technological advancements and aggressive multimodal treatment, prognosis remains dismal. The highly vascularized nature of glioblastoma enables the tumor cells to grow and invade the surrounding tissue, and vascular endothelial growth factor-A (VEGF-A) is a critical mediator of this process. Therefore, over the past decade, angiogenesis, and more specifically, the VEGF signaling pathway, has emerged as a therapeutic target for glioblastoma therapy. This led to the FDA approval of bevacizumab, a monoclonal antibody designed against VEGF-A, for treatment of recurrent glioblastoma. Despite the promising preclinical data and its theoretical effectiveness, bevacizumab has failed to improve patients' overall survival. Furthermore, several other anti-angiogenic agents that target the VEGF signaling pathway have also not demonstrated survival improvement. This suggests the presence of other compensatory angiogenic signaling pathways that surpass the anti-angiogenic effects of these agents and facilitate vascularization despite ongoing VEGF signaling inhibition. Herein, we review the current state of anti-angiogenic agents, discuss potential mechanisms of anti-angiogenic resistance, and suggest potential avenues to increase the efficacy of this therapeutic approach.

Epithelial membrane protein 2 (EMP2): A systematic review of its implications in pathogenesis

OBJECTIVES

Epithelial membrane protein 2 (EMP2) is a cell surface protein composed of approximately 160 amino acids and encoded by the growth arrest-specific 3 (GAS3)/peripheral myelin protein 22 kDa (PMP22) gene family. Although EMP2 expression has been investigated in several diseases, much remains unknown regarding its mechanism of action and the extent of its role in pathogenesis. Our aim was to perform a systematic review on the involvement of EMP2 in disease processes and the current usage of anti-EMP2 therapies.

METHODS

A Boolean search of the English-language medical literature was performed. PubMed, Scopus, Cochrane, and Web of Science were used to identify relevant citations. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

52 studies met the inclusion criteria for qualitative analysis. Of those, 28 (53.8%) were human-only studies, 11 (21.2%) were animal-only studies, and 13 (25%) studies included both human and animal models. Furthermore, 34 (65.4%) studies focused on EMP2's role in neoplasms, while the remaining 18 (34.6%) articles evaluated its role in other pathologies.

CONCLUSION

Overall, the evidence suggests the mechanisms of action of EMP2 are context dependent. Promising results have been produced by utilizing EMP2 as a biomarker and therapeutic target. More studies are warranted to better understand the mechanism and comprehend the role of EMP2 in the pathogenesis of diseases.

Unraveling the structures, functions and mechanisms of epithelial membrane protein family in human cancers

Peripheral myelin protein 22 (PMP22) and epithelial membrane proteins (EMP-1, -2, and -3) belong to a small hydrophobic membrane protein subfamily, with four transmembrane structures. PMP22 and EMPs are widely expressed in various tissues and play important roles in cell growth, differentiation, programmed cell death, and metastasis. PMP22 presents its highest expression in the peripheral nerve and participates in normal physiological and pathological processes of the peripheral nervous system. The progress of molecular genetics has shown that the genetic changes of the PMP22 gene, including duplication, deletion, and point mutation, are behind various hereditary peripheral neuropathies. EMPs have different expression patterns in diverse tissues and are closely related to the risk of malignant tumor progression. In this review, we focus on the four members in this protein family which are related to disease pathogenesis and discuss gene mutations and post-translational modification of them. Further research into the interactions between structural alterations and function of PMP22 and EMPs will help understand their normal physiological function and role in diseases and might contribute to developing novel therapeutic tools.

Repression of Smad4 by MicroRNA-1285 moderates TGF-β-induced epithelial-mesenchymal transition in proliferative vitreoretinopathy

The purpose of this study was to assess whether microRNA (miR)-1285 can suppress the epithelial-mesenchymal transition (EMT) in retinal pigment epithelial cells. Expression of miR-1285 was evaluated using quantitative real-time polymerase chain reaction (RT-qPCR). The features of EMT were assessed using Western blotting, immunocytochemical staining, scratch wound healing tests, modified Boyden chamber assay, and collagen gel contraction assay. A rabbit model of proliferative vitreoretinopathy (PVR) was used for in vivo testing, which involved the induction of PVR by injection of transfected ARPE cells into the vitreous chamber. Luciferase reporter assay was performed to identify the putative target of miR-1285. The expression of miR-1285 was downregulated in ARPE-19 cells treated with transforming growth factor (TGF)-β. Overexpression of miR-1285 led to upregulation of zonula occludens-1, downregulation of α-smooth muscle actin and vimentin, cell migration and cell contractility-all EMT features-in the TGF-β2-treated ARPE-19 cells. The reporter assay indicated that the 3' untranslated region of Smad4 was the direct target of miR1285. PVR progression was alleviated in the miR-1285 transfected rabbits. In conclusion, overexpression of miR-1285 attenuates TGF-β2-induced EMT in a rabbit model of PVR, and the effect of miR-1285 in PVR is dependent on Smad4. Further research is warranted to develop a feasible therapeutic approach for the prevention and treatment of PVR.

High expression of EMP1 predicts a poor prognosis and correlates with immune infiltrates in bladder urothelial carcinoma

Epithelial membrane protein 1 (EMP1) is a key gene that regulates cell proliferation and metastatic capability in various types of cancer, and serves an important role in tumor-immune interactions. However, the association between EMP1 and clinical prognosis, as well as the presence of tumor-infiltrating lymphocytes in bladder urothelial carcinoma (BLCA) remains unclear. The present study aimed to explore the relationship between EMP1 expression and tumor immune cell infiltration in BLCA. In the present study, EMP1 expression in BLCA was analyzed using the Oncomine database, The Cancer Genome Atlas (TCGA) and the Tumor Immune Estimation Resource (TIMER). The effects of EMP1 on clinical prognosis were evaluated using the Kaplan-Meier plotter and Gene Expression Profiling Interactive Analysis. The correlations between EMP1, cancer immune infiltrates and lymphocyte abundance were determined using the TIMER and Tumor immune system interaction database. In addition, correlations between EMP1 expression and gene markers in immune infiltrates were analyzed using cBioportal. The results demonstrated that, compared with adjacent normal tissues, EMP1 was downregulated in BLCA tissues. High expression of EMP1 was significantly associated with poor overall survival (OS) in BLCA cases obtained from TCGA. Multivariate Cox analysis revealed that EMP1 was an independent predictor of OS in patients with BLCA. Gene set enrichment analysis revealed that EMP1 was associated with cancer-related pathways and was positively correlated with the levels of infiltrating CD8⁺ T cells, macrophages, neutrophils and dendritic cells in BLCA. Further analysis demonstrated that EMP1 was significantly associated with the enrichment of multiple types of lymphocyte. EMP1 expression exhibited a strong correlation with a range of immune markers in BLCA. In conclusion, the results of the present study demonstrated that EMP1 was associated with a poor prognosis in patients with BLCA, and that the levels of immune infiltration and multiple immunomarker groups were associated with EMP1 expression. These results suggested that EMP1 may be used as a predictive biomarker to determine the prognosis and immune infiltration in BLCA.

Gene expression of Epithelial Membrane Protein 2 gene and β1-Integrin gene in patients with breast cancer

Background

Breast cancer is the most common invasive cancer and the leading cause of cancer death in women. The function of over a thousand genes is reported as affected by genetic modifications in breast cancer.

Objectives

To study the gene expression of Epithelial Membrane 2 (EMP2) and β1-Integrin genes in patients with breast cancer.

Subjects and methods

This study was carried out by cooperation between the Biochemistry Division Department of Chemistry, Faculty of Science and Medical Biochemistry and Molecular Biology Department, Faculty of Medicine, Menoufia University. This study included 120 subjects divided into 2 groups Group I: Included 60 women with breast cancer undergoing modified radical mastectomy. Tissue specimens were taken from the cancerous breast tissue and from the marginal healthy breast tissues. Group II: Included 60 age and sex-matched apparently healthy women served as a control group. All patients participants were subjected to full history taking, general clinical examination, abdominal ultrasound, CT-scan for abdomen, mammography, fine needle biopsy, histopathological examination, immunostaining of tissues, metastatic work up (chest x-ray and bone scan) and laboratory investigations including: Complete blood count (patients and controls), serum carbohydrate antigen 15–3 (patients and controls), detection of EMP2 and β1-Integrin genes expression in the tissue samples by formation of cDNA by reverse transcription PCR after RNA extraction and real-time PCR using SYBR Green technique.

Results

Compared to healthy tissues, the breast cancer tissues had significant higher EMP2 and β1-Integringene expression levels. Also, there was a significant increase in CA15-3 in patients group as compared with the control group. It was found that EMP2 and β1-Integrin expression in malignant tissue samples correlates with advanced and metastatic disease.

Conclusion

The gene expression of EMP2 and β1-Integrin are important markers for the severity of breast cancer and they are good indicators of its prognosis.

Epithelial Membrane Protein 2 (EMP2) Promotes VEGF-Induced Pathological Neovascularization in Murine Oxygen-Induced Retinopathy

Purpose

Retinopathy of prematurity (ROP) is a leading cause of childhood blindness. ROP occurs as a consequence of postnatal hyperoxia exposure in premature infants, resulting in vasoproliferation in the retina. The tetraspan protein epithelial membrane protein-2 (EMP2) is highly expressed in the retinal pigment epithelium (RPE) in adults, and it controls vascular endothelial growth factor (VEGF) production in the ARPE-19 cell line. We, therefore, hypothesized that Emp2 knockout (Emp2 KO) protects against neovascularization in murine oxygen-induced retinopathy (OIR).

Methods

Eyes were obtained from wildtype (WT) and Emp2 KO mouse pups at P7, P12, P17, and P21 after normoxia or hyperoxia (P7-P12) exposure. Following hyperoxia exposure, RNA sequencing was performed using the retina/choroid layers obtained from WT and Emp2 KO at P17. Retinal sections from P7, P12, P17, and P21 were evaluated for Emp2, hypoxia-inducible factor 1α (Hif1α), and VEGF expression. Whole mount images were generated to assess vaso-obliteration at P12 and neovascularization at P17.

Results

Emp2 KO OIR mice demonstrated a decrease in pathologic neovascularization at P17 compared with WT OIR mice through evaluation of retinal vascular whole mount images. This protection was accompanied by a decrease in Hif1α at P12 and VEGFA expression at P17 in Emp2 KO animals compared with the WT animals in OIR conditions. Collectively, our results suggest that EMP2 enhances the effects of neovascularization through modulation of angiogenic signaling.

Conclusions

The protection of Emp2 KO mice against pathologic neovascularization through attenuation of HIF and VEGF upregulation in OIR suggests that hypoxia-induced upregulation of EMP2 expression in the neuroretina modulates HIF-mediated neuroretinal VEGF expression.

The Pivotal Roles of the Epithelial Membrane Protein Family in Cancer Invasiveness and Metastasis

The members of the family of epithelial membrane proteins (EMPs), EMP1, EMP2, and EMP3, possess four putative transmembrane domain structures and are composed of approximately 160 amino acid residues. EMPs are encoded by the growth arrest-specific 3 (GAS3)/peripheral myelin protein 22 kDa (PMP22) gene family. The GAS3/PMP22 family members play roles in cell migration, growth, and differentiation. Evidence indicates an association of these molecules with cancer progression and metastasis. Each EMP has pro- and anti-metastatic functions that are likely involved in the complex mechanisms of cancer progression. We have recently demonstrated that the upregulation of EMP1 expression facilitates cancer cell migration and invasion through the activation of a small GTPase, Rac1. The inoculation of prostate cancer cells overexpressing EMP1 into nude mice leads to metastasis to the lymph nodes and lungs, indicating that EMP1 contributes to metastasis. Pro-metastatic properties of EMP2 and EMP3 have also been proposed. Thus, targeting EMPs may provide new insights into their clinical utility. Here, we highlight the important aspects of EMPs in cancer biology, particularly invasiveness and metastasis, and describe recent therapeutic approaches.

EMP2 acts as a suppressor of melanoma and is negatively regulated by mTOR-mediated autophagy

Cutaneous melanoma is one of the most common malignant skin tumors and advanced melanoma is usually associated with a poor prognosis. In the current study, we demonstrated the tumor suppressing role of epithelial membrane protein-2 (EMP2) by inducing apoptosis in a A375 human melanoma cell line. Mechanistically, the low expression of EMP2 in melanoma is partially due to autophagic protein degradation mediated by the mTOR pathway. These results suggest there is regulation of autophagy as well as EMP2 levels might be an interesting novel targeted therapeutic strategy for melanoma. Although the further investigation is needed to deeply understand the regulatory mechanisms of EMP2 in melanoma progression and metastasis, our results clarify the functions and mechanisms of autophagy in melanoma, and shed new light on novel targeted therapeutics for melanoma.

Epithelial Membrane Protein-2 (EMP2) Antibody Blockade Reduces Corneal Neovascularization in an In Vivo Model

Purpose

Pathologic corneal neovascularization is a major cause of blindness worldwide, and treatment options are currently limited. VEGF is one of the critical mediators of corneal neovascularization but current anti-VEGF therapies have produced limited results in the cornea. Thus, additional therapeutic agents are needed to enhance the antiangiogenic arsenal. Our group previously demonstrated epithelial membrane protein-2 (EMP2) involvement in pathologic angiogenesis in multiple cancer models including breast cancer and glioblastoma. In this paper, we investigate the efficacy of anti-EMP2 immunotherapy in the prevention of corneal neovascularization.

Methods

An in vivo murine cornea alkali burn model was used to study pathologic neovascularization. A unilateral corneal burn was induced using NaOH, and subconjunctival injection of either anti-EMP2 antibody, control antibody, or sterile saline was performed after corneal burn. Neovascularization was clinically scored at 7 days postalkali burn, and eyes were enucleated for histologic analysis and immunostaining including VEGF, CD31, and CD34 expression.

Results

Anti-EMP2 antibody, compared to control antibody or vehicle, significantly reduced neovascularization as measured by clinical score and central cornea thickness, as well as by histologic reduction of neovascularization, decreased CD34 staining, and decreased CD31 staining. Incubation of corneal limbal cells in vitro with anti-EMP2 blocking antibody significantly decreased EMP2 expression, VEGF expression and secretion, and cell migration.

Conclusions

This work demonstrates the effectiveness of EMP2 as a novel target in pathologic corneal neovascularization in an animal model and supports additional investigation into EMP2 antibody blockade as a potential new therapeutic option.

Cigarette smoke-induced EGFR activation promotes epithelial mesenchymal migration of human retinal pigment epithelial cells through regulation of the FAK-mediated Syk/Src pathway

Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is inevitable change of age‑related macular degeneration (AMD). Smoking is a major risk factor for the development of EMT in several diseases, including lung cancer. Cigarette smoke‑induced stress promotes the production of epidermal growth factor (EGF) in RPE cells. However, the underlying signaling pathways induced by aberrant EGF receptor (EGFR) expression in cigarette smoke-exposed RPE cells remain largely unknown. In the present study, the morphological transformation and production of EMT-associated cytokines were investigated to analyze the effect of smoking on the retina. Furthermore, EGF‑treated or cigarette smoke‑exposed RPE cells, as well as the downstream targets of EGFR, were investigated to identify the key molecules involved in EMT of cigarette smoke‑stimulated RPE cells via immunoblotting. Exposure of RPE cells to cigarette smoke extract (CSE) induced secretion of VEGF and TGF‑β1, and increased the expression of EMT markers. CSE‑mediated focal adhesion kinase (FAK) activation resulted in the phosphorylation and activation of spleen associated tyrosine kinase (Syk)/Src proto‑oncogene, non‑receptor tyrosine kinase (Src), leading to migration and invasion of RPE cells. Knockdown of FAK or pharmacological inhibition of Syk/Src abrogated CSE‑mediated VEGF and TGF‑β1 production and blocked the phosphorylation of Smad2/3 in CSE‑stimulated RPE cells. Erlotinib (an EGFR inhibitor) suppressed EGF and CSE‑mediated switch from an epithelial to mesenchymal phenotype. Baicalein, an inhi-bitor of 12/15‑lipooxygenase, also efficiently suppressed CSE‑induced EMT processes by inhibiting EGFR‑associated downstream signaling transduction. The results identified a novel signaling pathway mediated by EGFR in CSE‑activated RPE cells, and suggest baicalein as a potential new therapeutic drug for CSE‑associated retinopathy.

Epithelial membrane protein 2: Molecular interactions and clinical implications

Epithelial membrane protein 2 (EMP2) is a cell surface protein that has recently emerged as an object of neuro-oncological interest due to its potential to be utilized as a biomarker and target for antibody therapies. Preclinical studies have demonstrated that EMP2 is associated with disease prognosis in a number of human cancers, including glioblastoma. The four large extracellular domains of EMP2 and its association with the extracellular matrix makes it an attractive target for future cancer therapies. Translational research suggests that EMP2 may be targeted with antibodies to improve tumor control and survival in a variety of murine models and cancer types. However, in order to translate these preclinical findings into the clinic, future research will need to focus on elucidating the role EMP2 in the normal human body by better understanding its molecular and chemical interactions. The focus of this review is to provide a comprehensive insight into current research endeavors, discuss the potential for clinically translatable applications, and predict the future directions of such research.

Epithelial Membrane Protein-2 in Human Proliferative Vitreoretinopathy and Epiretinal Membranes

Purpose

To determine the level of epithelial membrane protein-2 (EMP2) expression in preretinal membranes from surgical patients with proliferative vitreoretinopathy (PVR) or epiretinal membranes (ERMs). EMP2, an integrin regulator, is expressed in the retinal pigment epithelium and understanding EMP2 expression in human retinal disease may help determine whether EMP2 is a potential therapeutic target.

Methods

Preretinal membranes were collected during surgical vitrectomies after obtaining consents. The membranes were fixed, processed, sectioned, and protein expression of EMP2 was evaluated by immunohistochemistry. The staining intensity (SI) and percentage of positive cells (PP) in membranes were compared by masked observers. Membranes were categorized by their cause and type including inflammatory and traumatic.

Results

All of the membranes stained positive for EMP2. Proliferative vitreoretinopathy–induced membranes (all causes) showed greater expression of EMP2 than ERMs with higher SI (1.81 vs. 1.38; P = 0.07) and PP (2.08 vs. 1.54; P = 0.09). However all the PVR subgroups had similar levels of EMP2 expression without statistically significant differences by Kruskal-Wallis test. Inflammatory PVR had higher expression of EMP2 than ERMs (SI of 2.58 vs. 1.38); however, this was not statistically significant. No correlation was found between duration of PVR membrane and EMP2 expression. EMP2 was detected by RT-PCR in all samples (n = 6) tested.

Conclusions

All studied ERMs and PVR membranes express EMP2. Levels of EMP2 trended higher in all PVR subgroups than in ERMs, especially in inflammatory and traumatic PVR. Future studies are needed to determine the role of EMP2 in the pathogenesis and treatment of various retinal conditions including PVR.

Epithelial membrane protein 2 (EMP2) deficiency alters placental angiogenesis, mimicking features of human placental insufficiency

Epithelial membrane protein-2 (EMP2) is a tetraspan protein predicted to regulate placental development. Highly expressed in secretory endometrium and trophectoderm cells, previous studies suggest that it may regulate implantation by orchestrating the surface expression of integrins and other membrane proteins. In order to test the role of EMP2 in pregnancy, mice lacking EMP2 (Emp2^-/- ) were generated. Emp2^-/- females are fertile but have reduced litter sizes when carrying Emp2^-/- but not Emp2^+/- fetuses. Placentas of Emp2^-/- fetuses exhibit dysregulation in pathways related to neoangiogenesis, coagulation, and oxidative stress, and have increased fibrin deposition and altered vasculature. Given that these findings often occur due to placental insufficiency resulting in an oxygen-poor environment, the expression of hypoxia-inducible factor-1 alpha (HIF-1α) was examined. Placentas from Emp2^-/- fetuses had increased total HIF-1α expression in large part through an increase in uterine NK (uNK) cells, demonstrating a unique interplay between uNK cells and trophoblasts modulated through EMP2. To determine if these results translated to human pregnancy, placentas from normal, term deliveries or those complicated by placental insufficiency resulting in intrauterine growth restriction (IUGR) were stained for EMP2. EMP2 was significantly reduced in both villous and extravillous trophoblast populations in IUGR placentas. Experiments in vitro using human trophoblast cells lines indicate that EMP2 modulates angiogenesis by altering HIF-1α expression. Our results reveal a novel role for EMP2 in regulating trophoblast function and vascular development in mice and humans, and suggest that it may be a new biomarker for placental insufficiency. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

EMP1, EMP 2, and EMP3 as novel therapeutic targets in human cancer

The epithelial membrane protein genes 1, 2, and 3 (EMP1, EMP2, and EMP3) belong to the peripheral myelin protein 22-kDa (PMP22) gene family, which consists of at least seven members: PMP22, EMP1, EMP2, EMP3, PERP, brain cell membrane protein 1, and MP20. This review addresses the structural and functional features of EMPs, detailing their tissue distribution and functions in the human body, their expression pattern in a variety of tumors, and highlighting the underlying mechanisms involved in carcinogenesis. The implications in cancer biology, patient prognosis prediction, and potential application in disease therapy are discussed. For example, EMP1 was reported to be a biomarker of gefitinib resistance in lung cancer and contributes to prednisolone resistance in acute lymphoblastic leukemia patients. EMP2 functions as an oncogene in human endometrial and ovarian cancers; however, characteristics of EMP2 in urothelial cancer fulfill the criteria of a suppressor gene. Of particular interest, EMP3 overexpression in breast cancer is significantly related to strong HER-2 expression. Co-expression of HER-2 and EMP3 is the most important indicator of progression-free and metastasis-free survival for patients with urothelial carcinoma of the upper urinary tract. Altogether, discovery of pharmacological inhibitors and/or regulators of EMP protein activity could open novel strategies for enhanced therapy against EMP-mediated human diseases.

EMP2 re-expression inhibits growth and enhances radiosensitivity in nasopharyngeal carcinoma

Although radiation therapy is the primary treatment for nasopharyngeal carcinoma, radioresistance remains a major obstacle to successful treatment in many cases, and the exact underlying molecular mechanisms are still ill-defined. EMP2, epithelial membrane protein-2, was a recently identified potential oncogene involved in multiple biological processes including cell migration and cell proliferation. This study was to explore the potential relationship between EMP2 expression, nasopharyngeal carcinoma genesis, and radioresistance. EMP2 expression status in 98 nasopharyngeal carcinoma clinical samples was examined by immunohistochemical staining. As a result, most of the nasopharyngeal carcinoma tumor samples were weakly or negatively stained, while paired adjacent normal tissues were moderately or strongly stained. Moreover, patients with higher expression of EMP2 had significant longer survival times. EMP2 re-expression suppresses cell growth, induces S-phase cell cycle arrest, and promotes radiosensitivity and apoptosis in nasopharyngeal carcinoma cells. These results support that loss of EMP2 is common, and its re-expression may serve as an approach to enhance radiation sensitivity in nasopharyngeal carcinoma.

Resveratrol inhibits transforming growth factor-β2-induced epithelial-to-mesenchymal transition in human retinal pigment epithelial cells by suppressing the Smad pathway

Proliferative vitreoretinopathy (PVR) is the main cause of failure following retinal detachment surgery. Transforming growth factor (TGF)-β2-induced epithelial-to-mesenchymal transition (EMT) plays an important role in the development of PVR, and EMT inhibition decreases collagen gel contraction and fibrotic membrane formation, resulting in prevention of PVR. Resveratrol is naturally found in red wine and has inhibitory effects on EMT. Resveratrol is widely used in cardioprotection, neuroprotection, chemotherapy, and antiaging therapy. The purpose of this study was to investigate the effects of resveratrol on TGF-β2-induced EMT in ARPE-19 cells in vitro. We found that resveratrol suppressed the decrease of zona occludens-1 (ZO-1) and caused an increase of alpha-smooth muscle actin expression in TGF-β2-treated ARPE-19 cells, assessed using Western blots; moreover, it also suppressed the decrease in ZO-1 and the increase of vimentin expression, observed using immunocytochemistry. Resveratrol attenuated TGF-β2-induced wound closure and cell migration in ARPE-19 cells in a scratch wound test and modified Boyden chamber assay, respectively. We also found that resveratrol reduced collagen gel contraction - assessed by collagen matrix contraction assay - and suppressed the phosphorylation of Smad2 and Smad3 in TGF-β2-treated ARPE-19 cells. These results suggest that resveratrol mediates anti-EMT effects, which could be used in the prevention of PVR.

Inhibitory Effect of Bone Morphogenetic Protein 4 in Retinal Pigment Epithelial-Mesenchymal Transition

Proliferative vitreoretinopathy (PVR), a serious vision-threatening complication of retinal detachment (RD), is characterized by the formation of contractile fibrotic membranes, in which epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is a major event. Recent studies suggest an important role of bone morphogenetic protein 4 (BMP4) in the suppression of fibrosis. In this study, we aimed to investigate the role of BMP4 in the pathological process of PVR, particularly in the EMT of RPE cells. We found that BMP4 and its receptors were co-labelled with cytokeratin and α-SMA positive cells within the PVR membrane. Moreover, the mRNA and protein expression levels of BMP4 were decreased whereas BMP4 receptors ALK2, ALK3 and ALK6 were increased during TGF-β-induced EMT in primary RPE cells. Exogenous BMP4 inhibited TGF-β-induced epithelial marker down-regulation, as well as mesenchymal marker up-regulation at both the mRNA and protein levels in RPE cells. In addition, BMP4 treatment attenuated the TGF-β-induced gel contraction, cell migration and Smad2/3 phosphorylation. However, knockdown of endogenous BMP4 stimulated changes in EMT markers. Our results confirm the hypothesis that BMP4 might inhibit TGF-β-mediated EMT in RPE cells via the Smad2/3 pathway and suppress contraction. This might represent a potential treatment for PVR.

Epithelial membrane protein 2 regulates sphingosylphosphorylcholine-induced keratin 8 phosphorylation and reorganization: Changes of PP2A expression by interaction with alpha4 and caveolin-1 in lung cancer cells

Sphingosylphosphorylcholine (SPC) is found at increased in the malignant ascites of tumor patients and induces perinuclear reorganization of keratin 8 (K8) filaments that contribute to the viscoelasticity of metastatic cancer cells. However, the detailed mechanism of SPC-induced K8 phosphorylation and reorganization is not clear. We observed that SPC dose-dependently reduced the expression of epithelial membrane protein 2 (EMP2) in lung cancer cells. Then, we examined the role of EMP2 in SPC-induced phosphorylation and reorganization of K8 in lung cancer cells. We found that SPC concentration-dependently reduced EMP2 in A549, H1299, and other lung cancer cells. This was verified at the mRNA level by RT-PCR and real-time PCR (qPCR), and intracellular variation through confocal microscopy. EMP2 gene silencing and stable lung cancer cell lines established using EMP2 lentiviral shRNA induced K8 phosphorylation and reorganization. EMP2 overexpression reduced K8 phosphorylation and reorganization. We also observed that SPC-induced loss of EMP2 induces phosphorylation of JNK and ERK via reduced expression of protein phosphatase 2A (PP2A). Loss of EMP2 induces ubiquitination of protein phosphatase 2A (PP2A). SPC induced caveolin-1 (cav-1) expression and EEA1 endosome marker protein but not cav-2. SPC treatment enhanced the binding of cav-1 and PP2A and lowered binding of PP2A and alpha4. Gene silencing of EMP2 increased and gene silencing of cav-1 reduced migration of A549 lung cancer cells. Overall, these results suggest that SPC induces EMP2 down-regulation which reduces the PP2A via ubiquitination induced by cav-1, which sequestered alpha4, leading to the activation of ERK and JNK.

Loss of Epithelial Membrane Protein 2 Aggravates Podocyte Injury via Upregulation of Caveolin-1

Nephrotic syndrome is a CKD defined by proteinuria with subsequent hypoalbuminemia, hyperlipidemia, and edema caused by impaired renal glomerular filtration barrier function. We previously identified mutations in epithelial membrane protein 2 (EMP2) as a monogenic cause of this disease. Here, we generated an emp2-knockout zebrafish model using transcription activator-like effector nuclease-based genome editing. We found that loss of emp2 in zebrafish upregulated caveolin-1 (cav1), a major component of caveolae, in embryos and adult mesonephric glomeruli and exacerbated podocyte injury. This phenotype was partially rescued by glucocorticoids. Furthermore, overexpression of cav1 in zebrafish podocytes was sufficient to induce the same phenotype observed in emp2 homozygous mutants, which was also treatable with glucocorticoids. Similarly, knockdown of EMP2 in cultured human podocytes resulted in increased CAV1 expression and decreased podocyte survival in the presence of puromycin aminonucleoside, whereas glucocorticoid treatment ameliorated this phenotype. Taken together, we have established excessive CAV1 as a mediator of the predisposition to podocyte injury because of loss of EMP2, suggesting CAV1 could be a novel therapeutic target in nephrotic syndrome and podocyte injury.

The APC tumor suppressor is required for epithelial cell polarization and three-dimensional morphogenesis

The Adenomatous Polyposis Coli (APC) tumor suppressor has been previously implicated in the control of apical-basal polarity; yet, the consequence of APC loss-of-function in epithelial polarization and morphogenesis has not been characterized. To test the hypothesis that APC is required for the establishment of normal epithelial polarity and morphogenesis programs, we generated APC-knockdown epithelial cell lines. APC depletion resulted in loss of polarity and multi-layering on permeable supports, and enlarged, filled spheroids with disrupted polarity in 3D culture. Importantly, these effects of APC knockdown were independent of Wnt/β-catenin signaling, but were rescued with either full-length or a carboxy (c)-terminal segment of APC. Moreover, we identified a gene expression signature associated with APC knockdown that points to several candidates known to regulate cell-cell and cell-matrix communication. Analysis of epithelial tissues from mice and humans carrying heterozygous APC mutations further supports the importance of APC as a regulator of epithelial behavior and tissue architecture. These data also suggest that the initiation of epithelial-derived tumors as a result of APC mutation or gene silencing may be driven by loss of polarity and dysmorphogenesis.

Review of the GAS3 Family of Proteins and their Relevance to Cancer

The GAS3 family of tetraspan proteins has recently been implicated in the progression of cancer. Currently, six members of the GAS3 family have been identified in humans and mice, and while their expressions in disease vary, data suggest that they play a role in epithelial cell structure and function. In this review, we highlight the studies implicating four of the members in disease pathogenesis as well as probe the structural similarities between the family members. Finally, the impact of targeting select members of the family such as PMP22 and EMP2 is discussed.

Regulation of FAK Activity by Tetraspan Proteins: Potential Clinical Implications in Cancer

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that regulates multiple cell signaling pathways in both physiological and pathological conditions. Overexpression and activation of FAK is associated with many advanced stage cancers through promoting cancer cell tumorigenicity and progression as well as by regulating the tumor microenvironment. FAK has multiple binding partners through which FAK exerts its functions including RhoGEF, Src family, talin, cortactin, and paxilin. Over the last few years, it has been proposed that a novel group of four transmembrane proteins can interact with FAK and regulate its activity. These include select tetraspanins such as CD151 and CD9 as well as the GAS3 family members epithelial membrane protein-2 (EMP2) and peripheral myelin protein-22 (PMP22). In this review, we discuss the current knowledge of the interaction between FAK and tetraspan proteins in physiological and pathological conditions, with an emphasis on the potential of tetraspan family members as therapeutic targets in cancer.

Epithelial membrane protein-2 (EMP2) activates Src protein and is a novel therapeutic target for glioblastoma

Despite recent advances in molecular classification, surgery, radiotherapy, and targeted therapies, the clinical outcome of patients with malignant brain tumors remains extremely poor. In this study, we have identified the tetraspan protein epithelial membrane protein-2 (EMP2) as a potential target for glioblastoma (GBM) killing. EMP2 had low or undetectable expression in normal brain but was highly expressed in GBM as 95% of patients showed some expression of the protein. In GBM cells, EMP2 enhanced tumor growth in vivo in part by up-regulating αvβ3 integrin surface expression, activating focal adhesion kinase and Src kinases, and promoting cell migration and invasion. Consistent with these findings, EMP2 expression significantly correlated with activated Src kinase in patient samples and promoted tumor cell invasion using intracranial mouse models. As a proof of principle to determine whether EMP2 could serve as a target for therapy, cells were treated using specific anti-EMP2 antibody reagents. These reagents were effective in killing GBM cells in vitro and in reducing tumor load in subcutaneous mouse models. These results support the role of EMP2 in the pathogenesis of GBM and suggest that anti-EMP2 treatment may be a novel therapeutic treatment.

Pathological vitreous causes cell line-derived (but not donor-derived) retinal pigment epithelial cells to display proliferative vitreoretinopathy-like features in culture

BACKGROUND

It is well understood that epithelial mesenchymal transformation occurs when retinal pigment epithelial cells, sourced from either a cell line or cadaver eye, are cultured in the presence of cadaver-derived vitreous. We sought to study the changes in retinal pigment epithelial cells when cell line-derived retinal pigment epithelial cells are cultured in the presence of pathological vitreous.

DESIGN

Prospective study.

SAMPLES

42 patients with rhegmatogenous retinal detachments.

METHODS

D407 retinal pigment epithelial cells were cultured in the presence of cadaver-derived vitreous or vitreous/subretinal fluid derived from patients undergoing retinal reattachment surgeries. Besides the changes in phenotypic characteristics, the viability, proliferation, migration, mesenchymal marker expression and changes in the extracellular matrix components were also evaluated.

MAIN OUTCOME MEASURES

Fibrotic phenotype in cell culture.

RESULTS

Our study clearly demonstrates that cell line-derived retinal pigment epithelial cells (unlike donor-derived retinal pigment epithelial cells) cultured in the presence of patient-derived vitreous/subretinal fluid, exhibit characteristic features of proliferative vitreoretinopathy.

CONCLUSIONS

We propose that it is the synergistic effect of the combined use of (i) pathological vitreous, rather than cadaver-derived vitreous (since rhegmatogenous retinal detachment-derived pathological vitreous and subretinal fluid contain exaggerated amounts of growth factors, which could predispose to proliferative vitreoretinopathy development) and (ii) cells from an immortal cell culture (cell line), rather than from primary cell cultures (since cells subjected to continuous serial passaging acquire some mesenchymal characteristics), which together result in not only a unique phenotype, but also prime these cells towards display of features associated with proliferative vitreoretinopathy.

Rationale and preclinical efficacy of a novel anti-EMP2 antibody for the treatment of invasive breast cancer

Despite significant advances in biology and medicine, the incidence and mortality due to breast cancer worldwide is still unacceptably high. Thus, there is an urgent need to discover new molecular targets. In this article, we show evidence for a novel target in human breast cancer, the tetraspan protein epithelial membrane protein-2 (EMP2). Using tissue tumor arrays, protein expression of EMP2 was measured and found to be minimal in normal mammary tissue, but it was upregulated in 63% of invasive breast cancer tumors and in 73% of triple-negative tumors tested. To test the hypothesis that EMP2 may be a suitable target for therapy, we constructed a fully human immunoglobulin G1 (IgG1) antibody specific for a conserved domain of human and murine EMP2. Treatment of breast cancer cells with the anti-EMP2 IgG1 significantly inhibited EMP2-mediated signaling, blocked FAK/Src signaling, inhibited invasion, and promoted apoptosis in vitro. In both human xenograft and syngeneic metastatic tumor monotherapy models, anti-EMP2 IgG1 retarded tumor growth without detectable systemic toxicity. This antitumor effect was, in part, attributable to a potent antibody-dependent cell-mediated cytotoxicity response as well as direct cytotoxicity induced by the monoclonal antibody. Together, these results identify EMP2 as a novel therapeutic target for invasive breast cancer.

Is neutralizing vitreal growth factors a viable strategy to prevent proliferative vitreoretinopathy?

Proliferative vitreoretinopathy (PVR) is a blinding disorder that occurs in eyes with rhegmatogenous retinal detachment and in eyes that have recently undergone retinal detachment surgery. There are presently no treatment strategies to reduce the risk of developing PVR in eyes with retinal detachment, and surgical intervention is the only option for eyes with retinal detachment and established PVR. Given the poor visual outcome associated with the surgical treatment of PVR, considerable work has been done to identify pharmacologic agents that could antagonize the PVR process. Intensive efforts to identify molecular determinants of PVR implicate vitreal growth factors. A surprise that emerged in the course of testing the 'growth factor hypothesis' of PVR was the existence of a functional relationship amongst growth factors that engage platelet-derived growth factor (PDGF) receptor α (PDGFRα), a receptor tyrosine kinase that is key to pathogenesis of experimental PVR. Vascular endothelial cell growth factor A (VEGF), which is best known for its ability to activate VEGF receptors (VEGFRs) and induce permeability and/or angiogenesis, enables activation of PDGFRα by a wide spectrum of vitreal growth factors outside of the PDGF family (non-PDGFs) in a way that triggers signaling events that potently enhance the viability of cells displaced into vitreous. Targeting these growth factors or signaling events effectively neutralizes the bioactivity of PVR vitreous and prevents PVR in a number of preclinical models. In this review, we discuss recent conceptual advances in understanding the role of growth factors in PVR, and consider the tangible treatment strategies for clinical application.

Positron emission tomography imaging of endometrial cancer using engineered anti-EMP2 antibody fragments

Purpose

As imaging of the cell surface tetraspan protein epithelial membrane protein-2 (EMP2) expression in malignant tumors may provide important prognostic and predictive diagnostic information, the goal of this study is to determine if antibody fragments to EMP2 may be useful for imaging EMP2 positive tumors.

Procedures

The normal tissue distribution of EMP2 protein expression was evaluated by immunohistochemistry and found to be discretely expressed in both mouse and human tissues. To detect EMP2 in tumors, a recombinant human anti-EMP2 minibody (scFv-hinge-C_H3 dimer; 80 kDa) was designed to recognize a common epitope in mice and humans and characterized. In human tumor cell lines, the antibody binding induced EMP2 internalization and degradation, prompting the need for a residualizing imaging strategy. Following conjugation to DOTA (1,4,7,10-tetraazacyclododecane-N,N′,N′,N′″-tetraacetic acid), the minibody was radiolabeled with ⁶⁴Cu (t_1/2 = 12.7 h) and evaluated in mice as a positron emission tomography (PET) imaging agent for human EMP2-expressing endometrial tumor xenografts.

Results

The residualizing agent, ⁶⁴Cu-DOTA anti-EMP2 minibody, achieved high uptake in endometrial cancer xenografts overexpressing EMP2 (10.2 ± 2.6, percent injected dose per gram (%ID/g) ± SD) with moderate uptake in wild-type HEC1A tumors (6.0 ± 0.1). In both cases, precise tumor delineation was observed from the PET images. In contrast, low uptake was observed with anti-EMP2 minibodies in EMP2-negative tumors (1.9 ± 0.5).

Conclusions

This new immune-PET agent may be useful for preclinical assessment of anti-EMP2 targeting in vivo. It may also have value for imaging of tumor localization and therapeutic response in patients with EMP2-positive malignancies.

Epithelial membrane protein 2 controls VEGF expression in ARPE-19 cells

PURPOSE

VEGF production by RPE cells has been shown to be important in regulating aberrant angiogenesis in the retina, which is responsible for multiple types of ocular pathology. EMP2 is highly expressed in the RPE and has been shown to regulate FAK activation, which is implicated in VEGF expression in other cell lines. The purpose of this study was to determine whether EMP2 regulates VEGF expression in the RPE cell line, ARPE-19.

METHODS

ARPE-19 cells were engineered to overexpress EMP2. EMP2 siRNA was used to decrease EMP2 expression. The small molecule inhibitor PP2 was used to inhibit FAK activation. VEGF levels were measured by Western blot and ELISA. Functional differences in secreted VEGF were assayed using HUVEC migration.

RESULTS

VEGF expression levels correlated with levels of EMP2. An increase of VEGF by 150% was observed in EMP2 overexpressing cells as compared with ARPE-19 cells. Concordantly, EMP2 knockdown resulted in a 57% decrease in VEGF expression. HUVEC migration (P = 0.01) and vessel tube formation (P < 0.01) were significantly increased when exposed to cell culture supernatants from EMP2 overexpressing cells.

CONCLUSIONS

This study establishes a novel connection between EMP2 and VEGF and may reflect either a direct effect through the tetraspan web or an indirect change through FAK activation. This connection is functionally significant. In addition to the direct use of anti-VEGF antibodies, modulation of EMP2 with impact on VEGF is potentially a distinct therapeutic target for the treatment of neovascularization associated with retinal diseases that involve pathologic angiogenesis.

EMP2 regulates angiogenesis in endometrial cancer cells through induction of VEGF

Understanding tumor-induced angiogenesis is a challenging problem with important consequences for the diagnosis and treatment of cancer. In this study, we define a novel function for epithelial membrane protein-2 (EMP2) in the control of angiogenesis. EMP2 functions as an oncogene in endometrial cancer, and its expression has been linked to decreased survival. Using endometrial cancer xenografts, modulation of EMP2 expression resulted in profound changes to the tumor microvasculature. Under hypoxic conditions, upregulation of EMP2 promoted vascular endothelial growth factors (VEGF) expression through a HIF-1α-dependent pathway and resulted in successful capillary-like tube formation. In contrast, reduction of EMP2 correlated with reduced HIF-1α and VEGF expression with the net consequence of poorly vascularized tumors in vivo. We have previously shown that targeting of EMP2 using diabodies in endometrial cancer resulted in a reduction of tumor load, and since then we have constructed a fully human EMP2 IgG1. Treatment of endometrial cancer cells with EMP2-IgG1 reduced tumor load with a significant improvement in survival. These results support the role of EMP2 in the control of the tumor microenvironment and confirm the cytotoxic effects observed by EMP2 treatment in vivo.

A novel function of p53: a gatekeeper of retinal detachment

Proliferative vitreoretinopathy (PVR) is a blinding disease associated with rhegmatogenous retinal detachment, for which there is no satisfactory treatment. Surgery helps in many cases, but, to our knowledge, there are no pharmacological approaches to reduce PVR risk. We report that suppressing expression of p53 was a required event in two assays of PVR (namely, platelet-derived growth factor receptor α-mediated contraction of cells in a collagen gel and retinal detachment in an animal model of PVR). Furthermore, preventing the decline in the level of p53 with agents such as Nutlin-3 protected from retinal detachment, which is the most vision-compromising component of PVR. Finally, Nutlin-3 may be effective in the clinical setting because it prevented human PVR vitreous-induced contraction of cells isolated from a patient PVR membrane. These studies identify Nutlin-3 as a potential PVR prophylaxis.

Anti-EMP2 diabody blocks epithelial membrane protein 2 (EMP2) and FAK mediated collagen gel contraction in ARPE-19 cells

Epithelial membrane protein 2 (EMP2) regulates collagen gel contraction by the retinal pigment epithelium cell line ARPE-19 by modulating FAK activation. Collagen gel contraction is one in vitro model for an aberrant wound healing response, proliferative vitreoretinopathy (PVR), which occurs as a complication of severe ocular trauma. The purpose of this study is to investigate whether EMP2 specific recombinant diabody decreases activation of FAK and collagen gel contraction in ARPE-19. Anti-EMP2 diabody was recombinantly constructed from a human phage library-derived clone selected for reactivity against an extracellular domain of human EMP2. ARPE-19 cells were exposed to an anti-EMP2 or control diabody, and toxicity, adhesion, and migration were assessed respectively through toluidine blue exclusion, binding to collagen type 1, and a migration assay. Collagen gel contraction was assessed using an in vitro assay. FAK activation was evaluated using Western blot. Exposure to anti-EMP2 diabody, resulted in a 75% reduction in EMP2 protein levels at 4 h. No significant toxicity was observed with anti-EMP2 diabody at levels that maximally reduced EMP2. Anti-EMP2 diabody, but not control diabody, significantly reduced collagen gel contraction (p < 0.001), without changes in adhesion or migration. Concordantly, anti-EMP2 diabody as compared to a control diabody reduced collagen stimulated FAK activation (p = 0.01). Anti-EMP2 diabody decreases EMP2 protein levels, FAK activation, and collagen gel contraction by ARPE-19 cells without an adverse effect on cell survival. Modulation of EMP2 using anti-EMP2 diabody could be a new approach for targeting EMP2 and pathologic consequences associated with EMP2.

Rewiring integrin-mediated signaling and cellular response with the peripheral myelin protein 22 and epithelial membrane protein 2 components of the tetraspan web

PURPOSE

Integrin-mediated collagen gel contraction by ARPE-19 is an in vitro model for proliferative vitreoretinopathy (PVR), an aberrant wound healing response after retinal detachment or ocular trauma. Expression of the tetraspan protein epithelial membrane protein 2 (EMP2) controls gel contraction through FAK activation. Peripheral myelin protein 22 (PMP22), another member of the tetraspan web, is closely related to EMP2. The purpose of this study was to determine whether PMP22 also controls the contractile phase associated with PVR.

METHODS

Integrin expression, adhesion, and protein expression were assessed, respectively, through flow cytometry, binding to collagen types I and IV, and Western blot analysis. Collagen gel contraction was assessed using an in vitro assay.

RESULTS

Overexpression of PMP22 in ARPE-19 cells (ARPE-19/PMP22) resulted in increased collagen adhesion. Gel contraction, however, was reduced by greater than 50% in ARPE-19/PMP22 cells (P < 0.001). In contrast to the FAK activation observed by increasing EMP2 expression, PMP22 overexpression led to increased AKT activation. The decrease in gel contraction by the ARPE-19/PMP22 cells was partially reversed through either PMP22 siRNA or by blockade of AKT.

CONCLUSIONS

Relative expression of EMP2 or PMP22 within the tetraspan web drives a cellular response toward a FAK- or AKT-dependent pathway, respectively. EMP2 and PMP22 differentially regulate collagen gel contraction in the ARPE-19 cell line. The implication of this finding adds a new dimension to the concept of the tetraspan web, in which the abundance of individual tetraspan family members differentially regulates signal transduction and the downstream cellular response.

Epithelial membrane protein-2 (EMP2) and experimental proliferative vitreoretinopathy (PVR)

PURPOSE

Proliferative vitreoretinopathy (PVR) is believed to result in part from de-differentiation of retinal pigment epithelium (RPE) with cellular migration in the vitreous cavity, membrane formation, and contraction in an aberrant wound-healing strategy. In an in vitro collagen-gel contraction assay, epithelial membrane protein 2 (EMP2) controls contraction through activation of focal adhesion kinase (FAK) in a RPE cell line (ARPE-19). The purpose of this study was to investigate how blocking or altering the level of EMP2 expression changed clinical PVR in an in vivo model.

METHODS

Using the ARPE-19 cell line, the levels of EMP2 modulated through stable transfections of an EMP2 overexpressing construct, EMP2 ribozyme, or vector alone. These transfected cell lines were used in a rabbit model of PVR. The severity of PVR was classified by two masked observers. An EMP2 blocking antibody was also used to decrease functional EMP2 in the PVR model. Immunohistochemistry was used to evaluate EMP2 expression in vivo.

RESULTS

The transfectants with lower levels of EMP2 had significantly less PVR severity than the degree of PVR induced by wild-type cells (p = 0.05). Also, the transfectants with a low-level of EMP2 expression showed a strong trend of less PVR severity than the high-levels EMP2 transfectants (p = 0.06). Blocking EMP2 with a specific polyclonal antibody significantly decreased the level of PVR severity (p = 0.02). PVR membranes were found to be positive for EMP2 expression.

CONCLUSIONS

These in vivo studies support a direct correlation between EMP2 expression and severity of PVR. These results validate the potential for controlling RPE biology through a change in EMP2 expression, and provide a potential therapeutic target for this disease.

Epithelial membrane protein-2 promotes endometrial tumor formation through activation of FAK and Src

Endometrial cancer is the most common gynecologic malignancy diagnosed among women in developed countries. One recent biomarker strongly associated with disease progression and survival is epithelial membrane protein-2 (EMP2), a tetraspan protein known to associate with and modify surface expression of certain integrin isoforms. In this study, we show using a xenograft model system that EMP2 expression is necessary for efficient endometrial tumor formation, and we have started to characterize the mechanism by which EMP2 contributes to this malignant phenotype. In endometrial cancer cells, the focal adhesion kinase (FAK)/Src pathway appears to regulate migration as measured through wound healing assays. Manipulation of EMP2 levels in endometrial cancer cells regulates the phosphorylation of FAK and Src, and promotes their distribution into lipid raft domains. Notably, cells with low levels of EMP2 fail to migrate and poorly form tumors in vivo. These findings reveal the pivotal role of EMP2 in endometrial cancer carcinogenesis, and suggest that the association of elevated EMP2 levels with endometrial cancer prognosis may be causally linked to its effect on integrin-mediated signaling.

Epithelial membrane protein-2 is a novel therapeutic target in ovarian cancer

PURPOSE

The tetraspan protein epithelial membrane protein-2 (EMP2) has been shown to regulate the surface display and signaling from select integrin pairs, and it was recently identified as a prognostic biomarker in human endometrial cancer. In this study, we assessed the role of EMP2 in human ovarian cancer.

EXPERIMENTAL DESIGN

We examined the expression of EMP2 within a population of women with ovarian cancer using tissue microarray assay technology. We evaluated the efficacy of EMP2-directed antibody therapy using a fully human recombinant bivalent antibody fragment (diabody) in vitro and ovarian cancer xenograft models in vivo.

RESULTS

EMP2 was found to be highly expressed in >70% of serous and endometrioid ovarian tumors compared with nonmalignant ovarian epithelium using a human ovarian cancer tissue microarray. Using anti-EMP2 diabody, we evaluated the in vitro response of nine human ovarian cancer cell lines with detectable EMP2 expression. Treatment of human ovarian cancer cell lines with anti-EMP2 diabodies induced cell death and retarded cell growth, and these response rates correlated with cellular EMP2 expression. We next assessed the effects of anti-EMP2 diabodies in mice bearing xenografts from the ovarian endometrioid carcinoma cell line OVCAR5. Anti-EMP2 diabodies significantly suppressed tumor growth and induced cell death in OVCAR5 xenografts.

CONCLUSIONS

These findings indicate that EMP2 is expressed in the majority of ovarian tumors and may be a feasible target in vivo.

Epithelial membrane protein-2 expression is an early predictor of endometrial cancer development

BACKGROUND

Endometrial cancer (EC) is a common malignancy worldwide. It is often preceded by endometrial hyperplasia, whose management and risk of neoplastic progression vary. Previously, the authors have shown that the tetraspan protein epithelial membrane protein-2 (EMP2) is a prognostic indicator for EC aggressiveness and survival. Here the authors validate the expression of EMP2 in EC, and further examine whether EMP2 expression within preneoplastic lesions is an early prognostic biomarker for EC development.

METHODS

A tissue microarray (TMA) was constructed with a wide representation of benign and malignant endometrial samples. The TMA contains a metachronous cohort of cases from individuals who either developed or did not develop EC. Intensity and frequency of EMP2 expression were assessed using immunohistochemistry.

RESULTS

There was a stepwise, statistically significant increase in the average EMP2 expression from benign to hyperplasia to atypia to EC. Furthermore, detailed analysis of EMP2 expression in potentially premalignant cases demonstrated that EMP2 positivity was a strong predictor for EC development.

CONCLUSIONS

EMP2 is an early predictor of EC development in preneoplastic lesions. In addition, combined with our previous findings, these results validate EMP2 as a novel biomarker for EC development.

Functional consequences of interactions between FAK and epithelial membrane protein 2 (EMP2)

PURPOSE

Collagen gel contraction by ARPE-19 is controlled by epithelial membrane protein 2 (EMP2) through focal adhesion kinase (FAK) activation. The purpose of this study was to test the role of EMP2 in the cellular context of FAK activation.

METHODS

The ARPE-19 cell line was recombinantly modified to increase the expression of EMP2 and was used in this study. Quantification of FAK and Src phosphorylation was determined with Western blot analysis of whole cell lysates with the use of specific antibodies for different target sites of phosphorylation. Coimmunoprecipitation of whole cell lysates with an antibody against EMP2, followed by Western blot analysis and identification of FAK, was performed. Focal adhesions and their relationship to EMP2 were identified with immunofluorescence and confocal microscopy. F-actin distribution was identified using fluorescence microscopy, and alpha- smooth muscle actin (alpha-SMA) expression was quantified with Western blot analysis and specific antibodies. Adhesion to collagen type I was determined with a binding assay.

RESULTS

EMP2 overexpression led to increased FAK phosphorylation at all measured phosphorylation sites. Coimmunoprecipitation and confocal microscopy provided evidence for a physical association between EMP2 and FAK. Increased EMP2 was also associated with altered distribution of focal adhesions, changes in actin organization, increased alpha-SMA expression, and increased adherence to a collagen-coated surface.

CONCLUSIONS

The EMP2-FAK association represents a novel protein-protein interaction, not previously reported, that demonstrates significant functional cellular responses in the context of in vitro models of proliferative vitreoretinopathy (PVR).

Diabodies targeting epithelial membrane protein 2 reduce tumorigenicity of human endometrial cancer cell lines

PURPOSE

Endometrial cancer is the most common gynecologic malignancy. One promising biomarker is epithelial membrane protein 2 (EMP2), and its expression is an independent prognostic indicator for tumors with poor clinical outcome expression. The present study assesses the suitability of EMP2 as a therapeutic target.

EXPERIMENTAL DESIGN

Human monovalent anti-EMP2 antibody fragments were isolated from a human phage display library and engineered as bivalent antibody fragments (diabodies) with specificity and avidity to both EMP2 peptides and native cell-surface EMP2 protein. Diabodies were assessed using cell death and apoptosis assays. In addition, the efficacy of EMP2 diabodies on endometrial cancer tumors was determined using mouse xenograft models.

RESULTS

Treatment of human endometrial adenocarcinoma cell lines with anti-EMP2 diabodies induced significant cell death and caspase-3 cleavage in vitro. These responses correlated with cellular EMP2 expression and were augmented by progesterone, which physiologically induces EMP2 expression. In vivo, treatment of subcutaneous human xenografts of HEC-1A cell lines with anti-EMP2 diabodies suppressed tumor growth and induced cell death in the xenograft.

CONCLUSIONS

These findings suggest that EMP2 may be a potential pharmacologic target for human endometrial cancer.