The Eph/Ephrin family in cancer metastasis: communication at the service of invasion

Predictive biomarkers for response to TGF- β inhibition in resensitizing chemo(radiated) esophageal adenocarcinoma

Epithelial-mesenchymal transition (EMT) has been identified as a driver of therapy resistance, particularly in esophageal adenocarcinoma (EAC), where transforming growth factor beta (TGF-β) can induce this process. Inhibitors of TGF-β may counteract the occurrence of mesenchymal, resistant tumor cell populations following chemo(radio)therapy and improve treatment outcomes in EAC. Here, we aimed to identify predictive biomarkers for the response to TGF-β targeting. In vitro approximations of neoadjuvant treatment were applied to publicly available primary EAC cell lines. TGF-β inhibitors fresolimumab and A83-01 were employed to inhibit EMT, and mesenchymal markers were quantified via flow cytometry to assess efficacy. Our results demonstrated a robust induction of mesenchymal cell states following chemoradiation, with TGF-β inhibition leading to variable reductions in mesenchymal markers. The cell lines were clustered into responders and non-responders. Genomic expression profiles were obtained through RNA-seq analysis. Differentially expressed gene (DEG) analysis identified 10 positively- and 23 negatively-associated hub genes, which were bioinformatically identified. Furthermore, the correlation of DEGs with response to TGF-β inhibition was examined using public pharmacogenomic databases, revealing 9 positively associated and 11 negatively associated DEGs. Among these, ERBB2, EFNB1, and TNS4 were the most promising candidates. Our findings reveal a distinct gene expression pattern associated with the response to TGF-β inhibition in chemo(radiated) EAC. The identified DEGs and predictive markers may assist patient selection in clinical studies investigating TGF-β targeting.

Therapeutic advances of targeting receptor tyrosine kinases in cancer

Receptor tyrosine kinases (RTKs), a category of transmembrane receptors, have gained significant clinical attention in oncology due to their central role in cancer pathogenesis. Genetic alterations, including mutations, amplifications, and overexpression of certain RTKs, are critical in creating environments conducive to tumor development. Following their discovery, extensive research has revealed how RTK dysregulation contributes to oncogenesis, with many cancer subtypes showing dependency on aberrant RTK signaling for their proliferation, survival and progression. These findings paved the way for targeted therapies that aim to inhibit crucial biological pathways in cancer. As a result, RTKs have emerged as primary targets in anticancer therapeutic development. Over the past two decades, this has led to the synthesis and clinical validation of numerous small molecule tyrosine kinase inhibitors (TKIs), now effectively utilized in treating various cancer types. In this manuscript we aim to provide a comprehensive understanding of the RTKs in the context of cancer. We explored the various alterations and overexpression of specific receptors across different malignancies, with special attention dedicated to the examination of current RTK inhibitors, highlighting their role as potential targeted therapies. By integrating the latest research findings and clinical evidence, we seek to elucidate the pivotal role of RTKs in cancer biology and the therapeutic efficacy of RTK inhibition with promising treatment outcomes.

New insights into the function and pathophysiology of the ectodomain sheddase A Disintegrin And Metalloproteinase 10 (ADAM10)

The 'A Disintegrin And Metalloproteinase 10' (ADAM10) has gained considerable attention due to its discovery as an 'α-secretase' involved in the nonamyloidogenic processing of the amyloid precursor protein, thereby possibly preventing the excessive generation of the amyloid beta peptide, which is associated with the pathogenesis of Alzheimer's disease. ADAM10 was found to exert many additional functions, cleaving about 100 different membrane proteins. ADAM10 is involved in many pathophysiological conditions, ranging from cancer and autoimmune disorders to neurodegeneration and inflammation. ADAM10 cleaves its substrates close to the plasma membrane, a process referred to as ectodomain shedding. This is a central step in the modulation of the functions of cell adhesion proteins and cell surface receptors. ADAM10 activity is controlled by transcriptional and post-translational events. The interaction of ADAM10 with tetraspanins and the way they functionally and structurally depend on each other is another topic of interest. In this review, we will summarize findings on how ADAM10 is regulated and what is known about the biology of the protease. We will focus on novel aspects of the molecular biology and pathophysiology of ADAM10 that were previously poorly covered, such as the role of ADAM10 on extracellular vesicles, its contribution to virus entry, and its involvement in cardiac disease, cancer, inflammation, and immune regulation. ADAM10 has emerged as a regulator controlling cell surface proteins during development and in adult life. Its involvement in disease states suggests that ADAM10 may be exploited as a therapeutic target to treat conditions associated with a dysfunctional proteolytic activity.

Ephs in cancer progression: complexity and context-dependent nature in signaling, angiogenesis and immunity

Eph receptors constitute the largest family of receptor tyrosine kinases, comprising 14 distinct members classified into two subgroups: EphAs and EphBs.. Despite their essential functions in normal physiological processes, accumulating evidence suggests that the involvement of the Eph family in cancer is characterized by a dual and often contradictory nature. Research indicates that Eph/ephrin bidirectional signaling influences cell-cell communication, subsequently regulating cell migration, adhesion, differentiation and proliferation. The contradictory functionalities may arise from the diversity of Eph signaling pathways and the heterogeneity of different cancer microenvironment. In this review, we aim to discuss the dual role of the Eph receptors in tumor development, attempting to elucidate the paradoxical functionality through an exploration of Eph receptor signaling pathways, angiogenesis, immune responses, and more. Our objective is to provide a comprehensive understanding of the molecular mechanisms underlying tumor development. Additionally, we will explore the evolving landscape of utilizing Eph receptors as potential targets for tumor therapy and diagnostic tools.

Diversity of Intercellular Communication Modes: A Cancer Biology Perspective

From the moment a cell is on the path to malignant transformation, its interaction with other cells from the microenvironment becomes altered. The flow of molecular information is at the heart of the cellular and systemic fate in tumors, and various processes participate in conveying key molecular information from or to certain cancer cells. For instance, the loss of tight junction molecules is part of the signal sent to cancer cells so that they are no longer bound to the primary tumors and are thus free to travel and metastasize. Upon the targeting of a single cell by a therapeutic drug, gap junctions are able to communicate death information to by-standing cells. The discovery of the importance of novel modes of cell-cell communication such as different types of extracellular vesicles or tunneling nanotubes is changing the way scientists look at these processes. However, are they all actively involved in different contexts at the same time or are they recruited to fulfill specific tasks? What does the multiplicity of modes mean for the overall progression of the disease? Here, we extend an open invitation to think about the overall significance of these questions, rather than engage in an elusive attempt at a systematic repertory of the mechanisms at play.

Cell Death, by Any Other Name…

Studies trying to understand cell death, this ultimate biological process, can be traced back to a century ago. Yet, unlike many other fashionable research interests, research on cell death is more alive than ever. New modes of cell death are discovered in specific contexts, as are new molecular pathways. But what is "cell death", really? This question has not found a definitive answer yet. Nevertheless, part of the answer is irreversibility, whereby cells can no longer recover from stress or injury. Here, we identify the most distinctive features of different modes of cell death, focusing on the executive final stages. In addition to the final stages, these modes can differ in their triggering stimulus, thus referring to the initial stages. Within this framework, we use a few illustrative examples to examine how intercellular communication factors in the demise of cells. First, we discuss the interplay between cell-cell communication and cell death during a few steps in the early development of multicellular organisms. Next, we will discuss this interplay in a fully developed and functional tissue, the gut, which is among the most rapidly renewing tissues in the body and, therefore, makes extensive use of cell death. Furthermore, we will discuss how the balance between cell death and communication is modified during a pathological condition, i.e., colon tumorigenesis, and how it could shed light on resistance to cancer therapy. Finally, we briefly review data on the role of cell-cell communication modes in the propagation of cell death signals and how this has been considered as a potential therapeutic approach. Far from vainly trying to provide a comprehensive review, we launch an invitation to ponder over the significance of cell death diversity and how it provides multiple opportunities for the contribution of various modes of intercellular communication.

The Ephrin tyrosine kinase a3 (EphA3) is a novel mediator of RAGE-prompted motility of breast cancer cells

BACKGROUND

The receptor for advanced glycation-end products (RAGE) and its ligands have been implicated in obesity and associated inflammatory processes as well as in metabolic alterations like diabetes. In addition, RAGE-mediated signaling has been reported to contribute to the metastatic progression of breast cancer (BC), although mechanistic insights are still required. Here, we provide novel findings regarding the transcriptomic landscape and the molecular events through which RAGE may prompt aggressive features in estrogen receptor (ER)-positive BC.

METHODS

MCF7 and T47D BC cells stably overexpressing human RAGE were used as a model system to evaluate important changes like cell protrusions, migration, invasion and colony formation both in vitro through scanning electron microscopy, clonogenic, migration and invasion assays and in vivo through zebrafish xenografts experiments. The whole transcriptome of RAGE-overexpressing BC cells was screened by high-throughput RNA sequencing. Thereafter, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses allowed the prediction of potential functions of differentially expressed genes (DEGs). Flow cytometry, real time-PCR, chromatin immunoprecipitation, immunofluorescence and western blot assays were performed to investigate the molecular network involved in the regulation of a novel RAGE target gene namely EphA3. The clinical significance of EphA3 was explored in the TCGA cohort of patients through the survivALL package, whereas the pro-migratory role of EphA3 signaling was ascertained in both BC cells and cancer-associated fibroblasts (CAFs). Statistical analysis was performed by t-tests.

RESULTS

RNA-seq findings and GSEA analysis revealed that RAGE overexpression leads to a motility-related gene signature in ER-positive BC cells. Accordingly, we found that RAGE-overexpressing BC cells exhibit long filopodia-like membrane protrusions as well as an enhanced dissemination potential, as determined by the diverse experimental assays. Mechanistically, we established for the first time that EphA3 signaling may act as a physical mediator of BC cells and CAFs motility through both homotypic and heterotypic interactions.

CONCLUSIONS

Our data demonstrate that RAGE up-regulation leads to migratory ability in ER-positive BC cells. Noteworthy, our findings suggest that EphA3 may be considered as a novel RAGE target gene facilitating BC invasion and scattering from the primary tumor mass. Overall, the current results may provide useful insights for more comprehensive therapeutic approaches in BC, particularly in obese and diabetic patients that are characterized by high RAGE levels.

Eph Receptors in Cancer

Eph receptor tyrosine kinases play critical functions during development, in the formation of tissue and organ borders, and the vascular and neural systems. Uniquely among tyrosine kinases, their activities are controlled by binding to membrane-bound ligands, called ephrins. Ephs and ephrins generally have a low expression in adults, functioning mainly in tissue homeostasis and plasticity, but are often overexpressed in cancers, where they are especially associated with undifferentiated or progenitor cells, and with tumour development, vasculature, and invasion. Mutations in Eph receptors also occur in various tumour types and are suspected to promote tumourigenesis. Ephs and ephrins have the capacity to operate as both tumour promoters and tumour suppressors, depending on the circumstances. They have been demonstrated to impact tumour cell proliferation, migration, and invasion in vitro, as well as tumour development, angiogenesis, and metastases in vivo, making them potential therapeutic targets. However, successful development of therapies will require detailed understanding of the opposing roles of Ephs in various cancers. In this review, we discuss the variations in Eph expression and functions in a variety of malignancies. We also describe the multiple strategies that are currently available to target them in tumours, including preclinical and clinical development.

Cell-cell contact-driven EphB1 cis- and trans- signalings regulate cancer stem cells enrichment after chemotherapy

Reactivation of chemotherapy-induced dormant cancer cells is the main cause of relapse and metastasis. The molecular mechanisms underlying remain to be elucidated. In this study, we introduced a cellular model that mimics the process of cisplatin responsiveness in NSCLC patients. We found that during the process of dormancy and reactivation induced by cisplatin, NSCLC cells underwent sequential EMT-MET with enrichment of cancer stem cells. The ATAC-seq combined with motif analysis revealed that OCT4-SOX2-TCF-NANOG motifs were associated with the enrichment of cancer stem cells induced by chemotherapy. Gene expression profiling suggested a dynamic regulatory mechanism during the process of enrichment of cancer stem cells, where Nanog showed upregulation in the dormant state and SOX2 showed upregulation in the reactivated state. Further, we showed that EphB1 and p-EphB1 showed dynamic expression in the process of cancer cell dormancy and reactivation, where the expression profiles of EphB1 and p-EphB1 showed negatively correlated. In the dormant EMT cells which showed disrupted cell-cell contacts, ligand-independent EphB1 promoted entry of lung cancer cells into dormancy through activating p-p38 and downregulating E-cadherin. On the contrary, in the state of MET, in which cell-cell adhesion was recovered, interactions of EphB1 and ligand EphrinB2 in trans promoted the stemness of cancer cells through upregulating Nanog and Sox2. In conclusion, lung cancer stem cells were enriched during the process of cellular response to chemotherapy. EphB1 cis- and trans- signalings function in the dormant and reactivated state of lung cancer cells respectively. It may provide a therapeutic strategy that target the evolution process of cancer cells induced by chemotherapy.

The Role of Hypoxia-Associated Long Non-Coding RNAs in Breast Cancer

Breast cancer is the leading cause of cancer-related deaths in women worldwide. In the United States, even with earlier diagnosis and treatment improvements, the decline in mortality has stagnated in recent years. More research is needed to provide better diagnostic, prognostic, and therapeutic tools for these patients. Long non-coding RNAs are newly described molecules that have extensive roles in breast cancer. Emerging reports have shown that there is a strong link between these RNAs and the hypoxic response of breast cancer cells, which may be an important factor for enhanced tumoral progression. In this review, we summarize the role of hypoxia-associated lncRNAs in the classic cancer hallmarks, describing their effects on the upstream and downstream hypoxia signaling pathway and the use of them as diagnostic and prognostic tools.

Ephrin receptor A10 monoclonal antibodies and the derived chimeric antigen receptor T cells exert an antitumor response in mouse models of triple-negative breast cancer

Expression of the receptor tyrosine kinase ephrin receptor A10 (EphA10), which is undetectable in most normal tissues except for the male testis, has been shown to correlate with tumor progression and poor prognosis in several malignancies, including triple-negative breast cancer (TNBC). Therefore, EphA10 could be a potential therapeutic target, likely with minimal adverse effects. However, no effective clinical drugs against EphA10 are currently available. Here, we report high expression levels of EphA10 in tumor regions of breast, lung, and ovarian cancers as well as in immunosuppressive myeloid cells in the tumor microenvironment. Furthermore, we developed anti-EphA10 monoclonal antibodies (mAbs) that specifically recognize cell surface EphA10, but not other EphA family isoforms, and target tumor regions precisely in vivo with no apparent accumulation in other organs. In syngeneic TNBC mouse models, we found that anti-EphA10 mAb clone #4 enhanced tumor regression, therapeutic response rate, and T cell–mediated antitumor immunity. Notably, the chimeric antigen receptor T cells derived from clone #4 significantly inhibited TNBC cell viability in vitro and tumor growth in vivo. Together, our findings suggest that targeting EphA10 via EphA10 mAbs and EphA10-specific chimeric antigen receptor–T cell therapy may represent a promising strategy for patients with EphA10-positive tumors.

EFNA3 Is a Prognostic Biomarker Correlated With Immune Cell Infiltration and Immune Checkpoints in Gastric Cancer

Background: Ephrin A3 (EFNA3), like most genes in the ephrin family, plays a central role in embryonic development and can be dysregulated in a variety of tumors. However, the relationship between EFNA3 and gastric cancer (GC) prognosis and tumor-infiltrating lymphocytes remains unclear.

Methods: Tumor Immune Estimation Resource (TIMER) and Gene Expression Profiling Interactive Analysis 2 (GEPIA2) were used to analyze the expression of EFNA3. Kaplan-Meier plots and GEPIA2 were used to evaluate the relationship between EFNA3 expression and GC prognosis. Univariable survival and multivariate Cox analyses were used to compare various clinical characteristics with survival. LinkedOmics database was used for gene set enrichment analysis (GSEA). TIMER database and CIBERSORT algorithm were used to examine the relationship between EFNA3 expression and immune infiltration in GC and to explore cumulative survival in GC. The relationship between EFNA3 and immune checkpoints was examined using cBioPortal genomics analysis. Finally, EFNA3 expression in GC cells and tissues was assayed using quantitative real-time polymerase chain reaction.

Results: EFNA3 expression differs in a variety of cancers, and EFNA3 expression was higher in GC tissue than normal gastric tissue. GC patients with high expression of EFNA3 had worse overall survival, disease-free survival, and first progression. Multivariate analysis identified EFNA3 as an independent prognostic factor for GC. GSEA identified ribosome, cell cycle, ribosome biogenesis in eukaryotes, and aminoacyl-tRNA biosynthesis pathways as differentially enriched in patients with high EFNA3 expression. B cells, CD8⁺ T cells, CD4⁺ T cells, macrophages, neutrophils, and dendritic cells were significantly negatively correlated with a variety of immune markers. EFNA3 participates in changes in GC immune checkpoint markers in a collinear manner. EFNA3 expression in HGC-27, AGS, MKN45, and NCI-N87 was cell lines higher than that in GES-1, and patients with high expression of EFNA3 had a worse prognosis.

Conclusion: EFNA3 can be used as a prognostic and immune infiltration and checkpoint marker in GC patients.

Classic Hodgkin Lymphoma Refractory for ABVD Treatment Is Characterized by Pathologically Activated Signal Transduction Pathways as Revealed by Proteomic Profiling

Simple Summary

Classic Hodgkin lymphoma (cHL) patients refractory to standard ABVD chemo-therapy are known to have a dismal prognosis. This has led to the hypothesis that ABVD treatment-sensitive and ABVD treatment-refractory tumours are biologically distinct. In this study, cHL patients refractory to standard ABVD treatment show subtle but significant differences in protein expression that enable clustering of the two response groups, thus indicating differences between ABVD sensitive and refractory patients at the molecular level, and thereby strengthening the hypothesis that ABVD sensitive and ABVD refractory tumours may be biologically distinct.

Abstract

In classic Hodgkin lymphoma (cHL), the tumour microenvironment (TME) is of major pathological relevance. The paucity of neoplastic cells makes it important to study the entire TME when searching for prognostic biomarkers. Cure rates in cHL have improved markedly over the last several decades, but patients with primary refractory disease still show inferior survival. We performed a proteomic comparison of pretreatment tumour tissue from ABVD treatment-refractory versus ABVD treatment-sensitive cHL patients, in order to identify biological differences correlating with treatment outcome. Formalin-fixed paraffin-embedded tumour tissues from 36 patients with cHL, 15 with treatment-refractory disease, and 21 with treatment-sensitive disease, were processed for proteomic investigation. Label-free quantification nano liquid chromatography tandem mass spectrometry was performed on the tissues. A total of 3920 proteins were detected and quantified between the refractory and sensitive groups. This comparison revealed several subtle but significant differences in protein expression which could identify subcluster characteristics of the refractory group. Bioinformatic analysis of the biological differences indicated that a number of pathologically activated signal transduction pathways are disturbed in ABVD treatment-refractory cHL.

IL13Rα2 Promotes Proliferation and Outgrowth of Breast Cancer Brain Metastases

PURPOSE

The survival of women with brain metastases (BM) from breast cancer remains very poor, with over 80% dying within a year of their diagnosis. Here, we define the function of IL13Rα2 in outgrowth of breast cancer brain metastases (BCBM) in vitro and in vivo, and postulate IL13Rα2 as a suitable therapeutic target for BM.

EXPERIMENTAL DESIGN

We performed IHC staining of IL13Rα2 in BCBM to define its prognostic value. Using inducible shRNAs in TNBC and HER2+ breast-brain metastatic models, we assessed IL13Rα2 function in vitro and in vivo. We performed RNAseq and functional studies to define the molecular mechanisms underlying IL13Rα2 function in BCBM.

RESULTS

High IL13Rα2 expression in BCBM predicted worse survival after BM diagnoses. IL13Rα2 was essential for cancer-cell survival, promoting proliferation while repressing invasion. IL13Rα2 KD resulted in FAK downregulation, repression of cell cycle and proliferation mediators, and upregulation of Ephrin B1 signaling. Ephrin-B1 (i) promoted invasion of BC cells in vitro, (ii) marked micrometastasis and invasive fronts in BCBM, and (iii) predicted shorter disease-free survival and BM-free survival (BMFS) in breast primary tumors known to metastasize to the brain. In experimental metastases models, which bypass early tumor invasion, downregulation of IL13Rα2 before or after tumor seeding and brain intravasation decreased BMs, suggesting that IL13Rα2 and the promotion of a proliferative phenotype is critical to BM progression.

CONCLUSIONS

Non-genomic phenotypic adaptations at metastatic sites are critical to BM progression and patients' prognosis. This study opens the road to use IL13Rα2 targeting as a therapeutic strategy for BM.

Effects of EFNA1 on cell phenotype and prognosis of esophageal carcinoma

Background

To investigate the expression and clinical significance of EFNA1 in broad-spectrum tumors, and to evaluate its relationship with prognosis and biological functions of esophageal carcinoma (ESCA).

Methods

EFNA1 expression in various cancers was analyzed according to the data in the TCGA database. The clinical data were integrated, to analyze the relationship with ESCA clinical parameters and prognosis, and EFNA1 expression in ESCA tissue samples was detected by immunohistochemistry (IHC). Based on bioinformatics, the functional background of EFNA1 overexpression was analyzed. EFNA1 knockout cell model was established by EFNA1-shRNA transfecting ESCA cells, and the effect of knocking down EFNA1 on the proliferation of ESCA cells was detected by MTT.

Results

Among 7563 samples from TCGA, the EFNA1 gene highly expressed in 15 samples with common cancers and endangered the prognosis of patients with tumors. Its overexpression in ESCA and its influence on the prognosis were most significant. EFNA1 expression in 80 samples with ESCA and their paired samples was tested by IHC to verify its high expression (paired t test, P < 0.001) in ESCA tissues. It was found that EFNA1 expression was related to clinical factors (TNM staging, P = 0.031; lymph node metastasis, P = 0.043; infiltration, P = 0.016). Meanwhile, EFNA1 was found to be an independent risk factor based on the COX multi-factor analysis. And to further explore the importance of EFNA1 in tumors, EC-9706 and ECA109 cells were screened from 8 ESCA-related cell lines to build EFNA1 knockdown cell models. The results showed that EFNA1 knockdown significantly inhibited the proliferation of tumor cells (P < 0.05). In terms of molecular mechanism, EFNA1 related genes were significantly enriched in the proliferative pathway according to the pathway enrichment analysis. It was found that knocking down EFNA1 did inhibit cell proliferation based on cell experiments.

Conclusions

EFNA1 overexpression in ESCA tissue is related to the prognosis of patients. Knocking down EFNA1 can significantly inhibit the proliferation of ESCA cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02362-8.

The Value of EphB2 Receptor and Cognate Ephrin Ligands in Prognostic and Predictive Assessments of Human Breast Cancer

Cell–cell communication proteins Eph and ephrin constitute the largest family of receptor tyrosine kinases (RTKs). They are distinguished by the fact that both receptors and ligands are membrane-bound, and both can drive intracellular signaling in their respective cells. Ever since these RTKs have been found to be involved in cancer development, strategies to target them therapeutically have been actively pursued. However, before this goal can be rationally achieved, the contributions of either Eph receptors or their ephrin ligands to cancer development and progression should be scrutinized in depth. To assess the clinical pertinence of this concern, we performed a systematic review and meta-analysis of the prognostic/predictive value of EphB2 and its multiple cognate ephrin ligands in breast cancer. We found that EphB2 has prognostic value, as indicated by the association of higher EphB2 expression levels with lower distant metastasis-free survival (DMFS), and the association of lower EphB2 expression levels with poorer relapse-free survival (RFS). We also found that higher EphB2 expression could be a prognostic factor for distant metastasis, specifically in the luminal subtypes of breast cancer. EFNB2 showed a marked correlation between higher expression levels and shorter DMFS. EFNA5 or EFNB1 overexpression is correlated with longer RFS. Increased EFNB1 expression is correlated with longer OS in lymph node (LN)-negative patients and the luminal B subtype. Higher levels of EFNB2 or EFNA5 are significantly correlated with shorter RFS, regardless of LN status. However, while this correlation with shorter RFS is true for EFNB2 in all subtypes except basal, it is also true for EFNA5 in all subtypes except HER2+. The analysis also points to possible predictive value for EphB2. In systemically treated patients who have undergone either endocrine therapy or chemotherapy, we found that higher expression of EphB2 is correlated with better rates of RFS. Bearing in mind the limitations inherent to any mRNA-based profiling method, we complemented our analysis with an immunohistochemical assessment of expression levels of both the EphB2 receptor and cognate ephrin ligands. We found that the latter are significantly more expressed in cancers than in normal tissues, and even more so in invasive and metastatic samples than in ductal carcinoma in situ (DCIS). Finally, in an in vitro cellular model of breast cancer progression, based on H-Ras-transformation of the MCF10A benign mammary cell line, we observed dramatic increases in the mRNA expression of EphB2 receptor and EFNB1 and EFNB2 ligands in transformed and invasive cells in comparison with their benign counterparts. Taken together, these data show the clinical validity of a model whereby EphB2, along with its cognate ephrin ligands, have dual anti- and pro-tumor progression effects. In so doing, they reinforce the necessity of further biological investigations into Ephs and ephrins, prior to using them in targeted therapies.

Ligand-Dependent and Ligand-Independent Effects of Ephrin-B2-EphB4 Signaling in Melanoma Metastatic Spine Disease

Tumor–endothelial cell interactions represent an essential mechanism in spinal metastasis. Ephrin-B2–EphB4 communication induces tumor cell repulsion from the endothelium in metastatic melanoma, reducing spinal bone metastasis formation. To shed further light on the Ephrin-B2–EphB4 signaling mechanism, we researched the effects of pharmacological EphB4 receptor stimulation and inhibition in a ligand-dependent/independent context. We chose a preventative and a post-diagnostic therapeutic window. EphB4 stimulation during tumor cell seeding led to an increase in spinal metastatic loci and number of disseminated melanoma cells, as well as earlier locomotion deficits in the presence of endothelial Ephrin-B2. In the absence of endothelial Ephrin-B2, reduction of metastatic loci with a later manifestation of locomotion deficits occurred. Thus, EphB4 receptor stimulation affects metastatic dissemination depending on the presence/absence of endothelial Ephrin-B2. After the manifestation of solid metastasis, EphB4 kinase inhibition resulted in significantly earlier manifestation of locomotion deficits in the presence of the ligand. No post-diagnostic treatment effect was found in the absence of endothelial Ephrin-B2. For solid metastasis treatment, EphB4 kinase inhibition induced prometastatic effects in the presence of endothelial Ephrin-B2. In the absence of endothelial Ephrin-B2, both therapies showed no effect on the growth of solid metastasis.

EphA8 inhibits cell apoptosis via AKT signaling and is associated with poor prognosis in breast cancer

Erythropoietin‑producing hepatocellular receptors (Ephs) comprise the largest subfamily of receptor tyrosine kinases and have been reported to be involved in a variety of biological cellular processes, including tumorigenesis and cancer progression. The present study aimed to determine the expression levels and clinicopathological significance of EphA8 in breast cancer (BC) using immunohistochemistry analysis of tissue microarrays. The results of the present study revealed that EphA8 expression levels were upregulated in BC tissue and were associated with tumor size and TNM stage. In addition, upregulated expression levels of EphA8 were identified to be a poor prognostic biomarker for patients with BC. The knockdown of EphA8 expression using short hairpin RNA resulted in increased levels of apoptosis as well as decreased proliferation, migration and invasion of BC cells both in vivo and in vitro. The knockdown of EphA8 also decreased the phosphorylation of AKT, which was accompanied by downregulation of Bcl‑2 expression levels and upregulation of p53, Caspase‑3 and Bax expression levels. Moreover, knockdown of EphA8 expression increased the chemosensitivity of BC cells to paclitaxel. In conclusion, the results of the present study indicated that EphA8 may be a useful prognostic marker in BC and that knockdown of EphA8 may represent a novel strategy in adjuvant chemotherapy for the treatment of BC.

Aggressive and recurrent ovarian cancers upregulate ephrinA5, a non-canonical effector of EphA2 signaling duality

Erythropoietin producing hepatocellular (Eph) receptors and their membrane-bound ligands ephrins are variably expressed in epithelial cancers, with context-dependent implications to both tumor-promoting and -suppressive processes in ways that remain incompletely understood. Using ovarian cancer tissue microarrays and longitudinally collected patient cells, we show here that ephrinA5/EFNA5 is specifically overexpressed in the most aggressive high-grade serous carcinoma (HGSC) subtype, and increased in the HGSC cells upon disease progression. Among all the eight ephrin genes, high EFNA5 expression was most strongly associated with poor overall survival in HGSC patients from multiple independent datasets. In contrast, high EFNA3 predicted improved overall and progression-free survival in The Cancer Genome Atlas HGSC dataset, as expected for a canonical inducer of tumor-suppressive Eph receptor tyrosine kinase signaling. While depletion of either EFNA5 or the more extensively studied, canonically acting EFNA1 in HGSC cells increased the oncogenic EphA2-S897 phosphorylation, EFNA5 depletion left unaltered, or even increased the ligand-dependent EphA2-Y588 phosphorylation. Moreover, treatment with recombinant ephrinA5 led to limited EphA2 tyrosine phosphorylation, internalization and degradation compared to ephrinA1. Altogether, our results suggest a unique function for ephrinA5 in Eph-ephrin signaling and highlight the clinical potential of ephrinA5 as a cell surface biomarker in the most aggressive HGSCs.

Ephrin-A2 promotes prostate cancer metastasis by enhancing angiogenesis and promoting EMT

BACKGROUND

Ephrin-A2, a member of the Eph receptor subgroup, is used in diagnosing and determining the prognosis of prostate cancer. However, the role of ephrin-A2 in prostate cancer is remains elusive.

METHODS

We established stable clones overexpressing or silencing ephrin-A2 from prostate cancer cells. Then, CCK-8 was used in analyzing the proliferation ability of cells. CD31 staining was used in evaluating angiogenesis. Migration and invasion assay were conducted in vivo and in vitro. The expression of EMT-related markers was evaluated in prostate cancer cells through Western blotting.

RESULTS

We revealed that the ectopic expression of ephrin-A2 in prostate cancer cells facilitated cell migration and invasion in vitro and promoted tumor metastasis and angiogenesis in vivo and that the silencing of ephrin-A2 completely reversed this effect. Although ephrin-A2 did not affect tumor cell proliferation in vitro, ephrin-A2 significantly promoted primary tumor growth in vivo. Furthermore, to determine the biological function of ephrin-A2, we assayed the expression of EMT-related markers in stable-established cell lines. Results showed that the overexpression of ephrin-A2 in prostate cancer cells down-regulated the expression of epithelial markers (ZO-1, E-cadherin, and claudin-1) and up-regulated the expression of mesenchymal markers (N-cadherin, β-catenin, vimentin, Slug, and Snail), but the knocking out of ephrin-A2 opposed the effects on the expression of EMT markers.

CONCLUSIONS

These findings indicate that ephrin-A2 promotes prostate cancer metastasis by enhancing angiogenesis and promoting EMT and may be a potentially therapeutic target in metastatic prostate cancer.

Enhanced efficacy of sitravatinib in metastatic models of antiangiogenic therapy resistance

Tyrosine kinase inhibitors (TKIs) that primarily target angiogenesis are approved to treat several cancers in the metastatic setting; however, resistance is common. Sequential treatment or 'switching' from one TKI to another following failure can be effective, but predicting which drugs will have cross-over sensitivity remains a challenge. Here we examined sitravatinib (MGCD516), a spectrum-selective TKI able to block MET, TAM (TYRO3, AXL, MerTK) and multiple receptor families (including PDGFRs, VEGFRs, and Ephs). Transcriptomic analysis of several mouse and human cell lines revealed diverse molecular changes after resistance to two TKIs (sunitinib and axitinib) with multiple sitravatinib targets found to be upregulated. Sitravatinib treatment in vitro resulted in enhanced anti-proliferative effects in resistant cells and was improved compared to TKIs with similar target profiles. In vivo, primary tumor growth inhibition after sitravatinib treatment in mice was enhanced in resistant tumors and metastasis suppression improved when tumors were surgically removed. Together, these results suggest that the diverse and often inconsistent compensatory signaling mechanisms found to contribute to TKI resistance may paradoxically improve the tumor-inhibiting effects of broad-spectrum TKIs such as sitravatinib that are able to block multiple signaling pathways. Sitravatinib in the second-line setting following antiangiogenic TKI treatment may have enhanced inhibitory effects in local and disseminated disease, and improve outcomes in patients with refractory disease.

EphA8 acts as an oncogene and contributes to poor prognosis in gastric cancer via regulation of ADAM10

EphA8 is a member of the erythropoietin-producing hepatocellular receptor (Eph) family of receptor tyrosine kinases. Ephs and their ephrins ligands play crucial roles in many cellular processed by mediating intracellular signaling resulting from cell-cell interactions. But the underlying mechanisms of EphA8 in gastric cancer (GC) remains unclearly. 298 clinical specimens in tissues microarray, and was found to be significantly higher in GC tissues compared with nontumor tissues (p < 0.001). EphA8 expression was also strongly associated with differentiation level (p = 0.025), tumor-node-metastasis stage (p = 0.019), and poor 5 years survival (p < 0.001). A panel of GC cell lines showed reduced proliferation, invasion, and migration capacities after RNA-mediated knockdown of EphA8, concomitant with downregulation of the proliferation-related proteins (cyclin A, cyclin D1, and cyclin-dependent kinase 4) and the metastasis-related (matrix metalloproteinases MMP2, and MMP9). EphA8 knockdown also decreased expression of the protease ADAM10 (a disintegrin and metalloproteinase domain-containing protein 10) and ADAM10-related protein AKT, suggesting an interaction between EphA8 and ADAM10. In conclusion, we found that EphA8, which is highly expressed in GC tissues, stimulates proliferation, invasion, and migration of cancer cells, and is an independent risk factor for poor prognosis of GC. These dates suggest that EphA8 could be new diagnostic and/or therapeutic targets for GC.

HMQ-T-B10 induces human liver cell apoptosis by competitively targeting EphrinB2 and regulating its pathway

Hepatocellular carcinoma (HCC) is a highly prevalent cancer worldwide and it is necessary to discover and develop novel preventive strategies and therapeutic approaches for HCC. Herein, we report that EphrinB2 expression is correlated with liver cancer progression. Moreover, by using phosphorylated proteomics array, we reveal a pro-apoptosis protein whose phosphorylation and activation levels are up-regulated upon EphrinB2 knockdown. These results suggest that EphrinB2 may act as an anti-apoptotic protein in liver cancer cells. We also explored the therapeutic potential of HMQ-T-B10 (B10), which was designed and synthesized in our laboratory, for HCC and its underlying mechanisms in vitro and in vivo. Our data demonstrate that B10 could bind EphrinB2 and show inhibitory activity on human liver cancer cells. Moreover, induction of human liver cancer cell apoptosis by B10 could be augmented upon EphrinB2 knockdown. B10 inhibited HCC cell growth and induced HCC cell apoptosis by repressing the EphrinB2 and VEGFR2 signalling pathway. Growth of xenograft tumours derived from Hep3B in nude mice was also significantly inhibited by B10. Collectively, these findings highlight the potential molecular mechanisms of B10 and its potential as an effective antitumour agent for HCC.

Ephrin-B2/Fc promotes proliferation and migration, and suppresses apoptosis in human umbilical vein endothelial cells

Tumor growth and metastasis are angiogenesis dependent. Angiogenic growth involves endothelial cell proliferation, migration, and invasion. Ephrin-B2 is a ligand for Eph receptor tyrosine kinases and is an important mediator in vascular endothelial growth factor-mediated angiogenesis. However, research offer controversial information regarding effects of ephrin-B2 on vascular endothelial cells. In this paper, proteome analyses showed that ephrin-B2/Fc significantly activates multiple signaling pathways related to cell proliferation, survival, and migration and suppresses apoptosis and cell death. Cytological experiments further confirm that ephrin-B2/Fc stimulates endothelial cell proliferation, triggers dose-dependent migration, and suppresses cell apoptosis. Results demonstrate that soluble dose-dependent ephrinB2 can promote proliferation and migration and inhibit apoptosis of human umbilical vein endothelial cells. These results also suggest that ephrinB2 prevents ischemic disease and can potentially be a new therapeutic target for treating angiogenesis-related diseases and tumors.

EphA8 is a prognostic marker for epithelial ovarian cancer

EphA8 is one of the Eph receptors in the Eph/ephrin receptor tyrosine kinase (RTK) subfamily. During tumorigenesis, EphA8 is involved in angiogenesis, cell adhesion and migration. In this study, we determined the mRNA and protein expression levels of EphA8 in cancerous and normal ovarian tissue samples by quantitative reverse transcription PCR (qRT-PCR) (N = 60) and tissue microarray immunohistochemistry analysis (TMA-IHC) (N = 223) respectively. EphA8 protein levels in cancer tissues were correlated with epithelial ovarian cancer (EOC) patients’ clinical characteristics and overall survival. Both EphA8 mRNA and protein levels were significantly higher in EOC tissues than in normal or benign ovarian tissues (all P < 0.05). High EphA8 protein level was associated older age at diagnosis, higher FIGO stage, positive lymph nodes, presence of metastasis, positive ascitic fluid, and higher serum CA-125 level. High EphA8 protein level is an independent prognostic marker in EOC. We conclude that EphA8 acts as an oncogene in EOC development and progression. Detection of EphA8 expression could be a useful prognosis marker and targeting EphA8 represents a novel strategy for EOC treatment.

Therapy of pancreatic cancer via an EphA2 receptor-targeted delivery of gemcitabine

First line treatment for pancreatic cancer consists of surgical resection, if possible, and a subsequent course of chemotherapy using the nucleoside analogue gemcitabine. In some patients, an active transport mechanism allows gemcitabine to enter efficiently into the tumor cells, resulting in a significant clinical benefit. However, in most patients, low expression of gemcitabine transporters limits the efficacy of the drug to marginal levels, and patients need frequent administration of the drug at high doses, significantly increasing systemic drug toxicity. In this article we focus on a novel targeted delivery approach for gemcitabine consisting of conjugating the drug with an EphA2 targeting agent. We show that the EphA2 receptor is highly expressed in pancreatic cancers, and accordingly, the drug-conjugate is more effective than gemcitabine alone in targeting pancreatic tumors. Our preliminary observations suggest that this approach may provide a general benefit to pancreatic cancer patients and offers a comprehensive strategy for enhancing delivery of diverse therapeutic agents to a wide range of cancers overexpressing EphA2, thereby potentially reducing toxicity while enhancing therapeutic efficacy.

EPHA6 rs4857055 C > T polymorphism associates with hypertension through triglyceride and LDL particle size in the Korean population

BACKGROUND

Erythropoietin-producing human hepatocellular (Eph) receptors might contribute to the development of atherosclerosis. A genome-wide association study indicated that the Eph receptor A6 gene (EPHA6) associated with at least 1 blood pressure (BP) phenotype. The objective of the present study was to determine whether EPHA6 is a novel candidate gene for hypertension in a Korean population.

METHODS

A total 2146 study participants with normotension and hypertension were included. Genotype data were obtained using a Korean Chip. To assess the association between single-nucleotide polymorphisms (SNPs) and BP, we performed a linear regression analysis, which showed that rs4850755 in the EPHA6 gene was the SNP most highly associated with both systolic and diastolic BP.

RESULTS

The presence of the TT genotype of the EPHA6 rs4857055 C > T SNP was associated with a higher risk of hypertension after adjusting for age, sex, body mass index (BMI), smoking, and drinking [odds ratio 1.533, P = 0.001]. In the control group, significant associations were observed between systolic BP and the rs4857055 polymorphism and between diastolic BP and the rs4857055 polymorphism. In the hypertension group, a significant association was observed between systolic BP and the rs4857055 polymorphism. In the hypertension group, subjects with the TT genotype showed significantly higher systolic BP than CC subjects. Additionally, in the hypertension group, TT carriers showed a higher tendency of serum triglyceride (P = 0.069) and significantly higher apolipoprotein B (P = 0.015) and smaller low-density lipoprotein (LDL) particle size (P < 0.001) than either TC or CC subjects.

CONCLUSIONS

These results could suggest that the EPHA6 rs4857055 C > T SNP is a novel candidate gene for hypertension in the Korean population. Additionally, the TT genotype could be associated with hypertriglyceridemia and small LDL particle size in hypertension.

EphrinB1 promotes cancer cell migration and invasion through the interaction with RhoGDI1

Eph receptors and their corresponding ephrin ligands have been associated with regulating cell–cell adhesion and motility, and thus have a critical role in various biological processes including tissue morphogenesis and homeostasis, as well as pathogenesis of several diseases. Aberrant regulation of Eph/ephrin signaling pathways is implicated in tumor progression of various human cancers. Here, we show that a Rho family GTPase regulator, Rho guanine nucleotide dissociation inhibitor 1 (RhoGDI1), can interact with ephrinB1, and this interaction is enhanced upon binding the extracellular domain of the cognate EphB2 receptor. Deletion mutagenesis revealed that amino acids 327–334 of the ephrinB1 intracellular domain are critical for the interaction with RhoGDI1. Stimulation with an EphB2 extracellular domain-Fc fusion protein (EphB2-Fc) induces RhoA activation and enhances the motility as well as invasiveness of wild-type ephrinB1-expressing cells. These Eph-Fc-induced effects were markedly diminished in cells expressing the mutant ephrinB1 construct (Δ327–334) that is ineffective at interacting with RhoGDI1. Furthermore, ephrinB1 depletion by siRNA suppresses EphB2-Fc-induced RhoA activation, and reduces motility and invasiveness of the SW480 and Hs578T human cancer cell lines. Our study connects the interaction between RhoGDI1 and ephrinB1 to the promotion of cancer cell behavior associated with tumor progression. This interaction may represent a therapeutic target in cancers that express ephrinB1.

Ubiquitin ligase SPSB4 diminishes cell repulsive responses mediated by EphB2

Eph receptor tyrosine kinases are important for cancer development and progression as well as in cellular repulsive responses. We determined that SOCS box-containing protein SPSB4 destabilizes EphB2 cytoplasmic fragments. SPSB4 is a novel ubiquitin ligase regulating EphB2-dependent cell repulsive responses.

Eph receptor tyrosine kinases and their ephrin ligands are overexpressed in various human cancers, including colorectal malignancies, suggesting important roles in many aspects of cancer development and progression as well as in cellular repulsive responses. The ectodomain of EphB2 receptor is cleaved by metalloproteinases (MMPs) MMP-2/MMP-9 and released into the extracellular space after stimulation by its ligand. The remaining membrane-associated fragment is further cleaved by the presenilin-dependent γ-secretase and releases an intracellular peptide that has tyrosine kinase activity. Although the cytoplasmic fragment is degraded by the proteasome, the responsible ubiquitin ligase has not been identified. Here, we show that SOCS box-containing protein SPSB4 polyubiquitinates EphB2 cytoplasmic fragment and that SPSB4 knockdown stabilizes the cytoplasmic fragment. Importantly, SPSB4 down-regulation enhances cell repulsive responses mediated by EphB2 stimulation. Altogether, we propose that SPSB4 is a previously unidentified ubiquitin ligase regulating EphB2-dependent cell repulsive responses.

EphB4 forward signalling mediates angiogenesis caused by CCM3/PDCD10-ablation

CCM3, also named as PDCD10, is a ubiquitous protein expressed in nearly all tissues and in various types of cells. It is essential for vascular development and post-natal vessel maturation. Loss-of-function mutation of CCM3 predisposes for the familial form of cerebral cavernous malformation (CCM). We have previously shown that knock-down of CCM3 stimulated endothelial angiogenesis via impairing DLL4-Notch signalling; moreover, loss of endothelial CCM3 stimulated tumour angiogenesis and promoted tumour growth. The present study was designed to further elucidate the inside signalling pathway involved in CCM3-ablation-mediated angiogenesis. Here we report for the first time that silencing endothelial CCM3 led to a significant up-regulation of EphB4 mRNA and protein expression and to an increased kinase activity of EphB4, concomitantly accompanied by an activation of Erk1/2, which was reversed by treatment with the specific EphB4 kinase inhibitor NVP-BHG712 (NVP), indicating that silencing CCM3 activates EphB4 kinase forward signalling. Furthermore, treatment with NVP rescued the hyper-angiogenic phenotype induced by knock-down of endothelial CCM3 in vitro and in vivo. Additional study demonstrated that the activation of EphB4 forward signalling in endothelial cells under basal condition and after CCM3-silence was modulated by DLL4/Notch signalling, relying EphB4 at downstream of DLL4/Notch signalling. We conclude that angiogenesis induced by CCM3-silence is mediated by the activation of EphB4 forward signalling. The identified endothelial signalling pathway of CCM3-DLL4/Notch-EphB4-Erk1/2 may provide an insight into mechanism of CCM3-ablation-mediated angiogenesis and could potentially contribute to novel therapeutic concepts for disrupting aberrant angiogenesis in CCM and in hyper-vascularized tumours.

Targeting Eph/ephrin system in cancer therapy

It is well established that the Eph/ephrin system plays a central role in the embryonic development, with minor implications in the physiology of the adult. However, it is overexpressed and deregulated in a variety of tumors, with a primary involvement in tumorigenesis, tumor angiogenesis, metastasis development, and cancer stem cell regeneration. Targeting the Eph/ephrin system with biologicals, including antibodies and recombinant proteins, reduces tumor growth in animal models of hematological malignancies, breast, prostate, colon, head and neck cancers and glioblastoma. Currently, some of these biopharmaceutical agents are under investigations in phase I or phase II clinical trials. Peptides and small molecules targeting protein-protein-interaction (PPI) are in the late preclinical phase where they are showing promising activity in models of glioblastoma, ovarian and lung cancer. The present review summarizes the most critical findings proposing the Eph/ephrin signaling system as a new target in molecularly targeted oncology.

A Cell-Surface Membrane Protein Signature for Glioblastoma

We present a systems strategy that facilitated the development of a molecular signature for glioblastoma (GBM), composed of 33 cell-surface transmembrane proteins. This molecular signature, GBMSig, was developed through the integration of cell-surface proteomics and transcriptomics from patient tumors in the REMBRANDT (n = 228) and TCGA datasets (n = 547) and can separate GBM patients from control individuals with a Matthew's correlation coefficient value of 0.87 in a lock-down test. Functionally, 17/33 GBMSig proteins are associated with transforming growth factor β signaling pathways, including CD47, SLC16A1, HMOX1, and MRC2. Knockdown of these genes impaired GBM invasion, reflecting their role in disease-perturbed changes in GBM. ELISA assays for a subset of GBMSig (CD44, VCAM1, HMOX1, and BIGH3) on 84 plasma specimens from multiple clinical sites revealed a high degree of separation of GBM patients from healthy control individuals (area under the curve is 0.98 in receiver operating characteristic). In addition, a classifier based on these four proteins differentiated the blood of pre- and post-tumor resections, demonstrating potential clinical value as biomarkers.

Paradoxes of the EphB1 receptor in malignant brain tumors

Eph receptors are a subfamily of receptor tyrosine kinases. Eph receptor-mediated forward and ephrin ligand-mediated reverse signalings are termed bidirectional signaling. Increasing evidence shows that Eph/ephrin signaling regulates cell migration, adhesion, morphological changes, differentiation, proliferation and survival through cell–cell communication. Some recent studies have started to implicate Eph/ephrin signaling in tumorigenesis, metastasis, and angiogenesis. Previous studies have shown that EphB1 receptor and its ephrin ligands are expressed in the central nervous system. EphB1/ephrin signaling plays an important role in the regulation of synapse formation and maturation, migration of neural progenitors, establishment of tissue patterns, and the development of immune organs. Besides, various recent studies have detected the abnormal expression of EphB1 receptor in different brain tumors. However, the underlying molecular mechanisms of EphB1/ephrins signaling in the development of these tumors are not fully understood. This review focuses on EphB1 that has both tumor-suppressing and -promoting roles in some brain tumors. Understanding the intracellular mechanisms of EphB1 in tumorigenesis and metastasis of brain tumors might provide a foundation for the development of EphB1-targeted therapies.

EphA6 promotes angiogenesis and prostate cancer metastasis and is associated with human prostate cancer progression

Metastasis is the primary cause of prostate cancer (CaP)-related death. We investigate the molecular, pathologic and clinical outcome associations of EphA6 expression and CaP metastasis. The expression profiling of Eph receptors (Ephs) and their ephrin ligands was performed in parental and metastatic CaP cell lines. Among Ephs and ephrins, only EphA6 is consistently overexpressed in metastatic CaP cells. Metastatic potential of EphA6 is assessed by RNAi in a CaP spontaneous metastasis mouse model. EphA6 knock-down in human PC-3M cells causes decreased invasion in vitro and reduced lung and lymph node metastasis in vivo. In addition, knock-down of EphA6 decreases tube formation in vitro and angiogenesis in vivo. EphA6 mRNA expression is higher in 112 CaP tumor samples compared with benign tissues from 58 benign prostate hyperplasia patients. Positive correlation was identified between EphA6 expression and vascular invasion, neural invasion, PSA level, and TNM staging in CaP cases. Further, genome-wide gene expression analysis in EphA6 knock-down cells identified a panel of differentially regulated genes including PIK3IPA, AKT1, and EIF5A2, which could contribute to EphA6-regulated cancer progression. These findings identify EphA6 as a potentially novel metastasis gene which positively correlates with CaP progression. EphA6 may be a therapeutic target in metastatic CaP.

Development of Specific, Irreversible Inhibitors for a Receptor Tyrosine Kinase EphB3

Erythropoietin-producing human hepatocellular carcinoma (Eph) receptor tyrosine kinases (RTKs) regulate a variety of dynamic cellular events, including cell protrusion, migration, proliferation, and cell-fate determination. Small-molecule inhibitors of Eph kinases are valuable tools for dissecting the physiological and pathological roles of Eph. However, there is a lack of small-molecule inhibitors that are selective for individual Eph isoforms due to the high homology within the family. Herein, we report the development of the first potent and specific inhibitors of a single Eph isoform, EphB3. Through structural bioinformatic analysis, we identified a cysteine in the hinge region of the EphB3 kinase domain, a feature that is not shared with any other human kinases. We synthesized and characterized a series of electrophilic quinazolines to target this unique, reactive feature in EphB3. Some of the electrophilic quinazolines selectively and potently inhibited EphB3 both in vitro and in cells. Cocrystal structures of EphB3 in complex with two quinazolines confirmed the covalent linkage between the protein and the inhibitors. A "clickable" version of an optimized inhibitor was created and employed to verify specific target engagement in the whole proteome and to probe the extent and kinetics of target engagement of existing EphB3 inhibitors. Furthermore, we demonstrate that the autophosphorylation of EphB3 within the juxtamembrane region occurs in trans using a specific inhibitor. These exquisitely specific inhibitors will facilitate the dissection of EphB3's role in various biological processes and disease contribution.

Regulation of EBV LMP1-triggered EphA4 downregulation in EBV-associated B lymphoma and its impact on patients' survival

Epstein-Barr virus (EBV), an oncogenic human virus, is associated with several lymphoproliferative disorders, including Burkitt lymphoma, Hodgkin disease, diffuse large B-cell lymphoma (DLBCL), and posttransplant lymphoproliferative disorder (PTLD). In vitro, EBV transforms primary B cells into lymphoblastoid cell lines (LCLs). Recently, several studies have shown that receptor tyrosine kinases (RTKs) play important roles in EBV-associated neoplasia. However, details of the involvement of RTKs in EBV-regulated B-cell neoplasia and malignancies remain largely unclear. Here, we found that erythropoietin-producing hepatocellular receptor A4 (EphA4), which belongs to the largest RTK Eph family, was downregulated in primary B cells post-EBV infection at the transcriptional and translational levels. Overexpression and knockdown experiments confirmed that EBV-encoded latent membrane protein 1 (LMP1) was responsible for this EphA4 suppression. Mechanistically, LMP1 triggered the extracellular signal-regulated kinase (ERK) pathway and promoted Sp1 to suppress EphA4 promoter activity. Functionally, overexpression of EphA4 prevented LCLs from proliferation. Pathologically, the expression of EphA4 was detected in EBV(-) tonsils but not in EBV(+) PTLD. In addition, an inverse correlation of EphA4 expression and EBV presence was verified by immunochemical staining of EBV(+) and EBV(-) DLBCL, suggesting EBV infection was associated with reduced EphA4 expression. Analysis of a public data set showed that lower EphA4 expression was correlated with a poor survival rate of DLBCL patients. Our findings provide a novel mechanism by which EphA4 can be regulated by an oncogenic LMP1 protein and explore its possible function in B cells. The results provide new insights into the role of EphA4 in EBV(+) PTLD and DLBCL.

EphA4-mediated signaling regulates the aggressive phenotype of irradiation survivor colorectal cancer cells

Radiotherapy is widely used for advanced rectal tumors. However, tumor recurrence after this treatment tends to be more aggressive and is associated with a poor prognosis. Uncovering the molecular mechanism that controls this recurrence is essential for developing new therapeutic applications. In the present study, we demonstrated that radiation increases the EphA4 activation level of the survivor progeny of colorectal cancer cells submitted to this treatment and that such activation promoted the internalization of a complex E-cadherin-EphA4, inducing cell-cell adhesion disruption. Moreover, EphA4 knockdown in the progeny of irradiated cells reduced the migratory and invasive potentials and metalloprotease activity induced by irradiation. Finally, we demonstrated that the cell migration and invasion potential were regulated by AKT and ERK1/2 signaling, with the ERK1/2 activity being dependent on EphA4. In summary, our study demonstrates that these signaling pathways could be responsible for the therapeutic failure, thereby promoting local invasion and metastasis in rectal cancer after radiotherapy. We also postulate that EphA4 is a potential therapeutic target for colorectal cancer treatment.

EphA4-deleted microenvironment regulates cancer development and leukemoid reaction of the isografted 4T1 murine breast cancer via reduction of an IGF1 signal

EphA4 belongs to the largest family of receptor tyrosine kinases (RTKs). Although EphA4 is highly expressed in the central nervous system, EphA4 has also been implicated in cancer progression. Most of the studies focus on the expression and function in tumor cells. It is unknown whether EphA4‐deleted microenvironment affects tumor progression. Some of cancers in animals and humans, such as 4T1 cancer cells, are known to produce a large amount of granulocyte colony‐stimulating factors (G‐CSF/Csf3) which can stimulate myeloproliferation, such as myeloid‐derived suppressor cells (MDSCs) leading to a poor recipient prognosis. We isografted 4T1 breast cancer cells into both EphA4‐knockout and control wild‐type female littermate mice. The results showed that the EphA4‐deleted host could inhibit primary tumor growth and tumor metastasis mainly by decreasing the amount of IGF1 synthesis in the circulation and locally tissues. The EphA4‐deleted microenvironment and delayed tumor development reduced the production of G‐CSF resulting in the decrease of splenomegaly and leukemoid reaction including MDSCs, which in turn inhibit the tumor progression. This inhibition can be reversed by supplying the mice with IGF1. However, an excess of IGF1 supply over demand to the control mice could not further accelerate the tumor growth and metastasis. A better understanding and re‐evaluation of the main role of IGF1 in regulating tumor progression could further enhance our cognition of the tumor development niche. Our findings demonstrated that EphA4‐deleted microenvironment impairs tumor‐supporting conditions. Conclusion: Host EphA4 expression regulates cancer development mainly via EphA4‐mediated IGF1 synthesis signal. Thus, targeting this signaling pathway may provide a potential therapeutic option for cancer treatment.

A Novel Bispecific Antibody against Human CD3 and Ephrin Receptor A10 for Breast Cancer Therapy

Ephrin receptor A10 (EphA10), a transmembrane receptor that binds to ephrin, is a newly identified breast cancer marker protein that has also been detected in HER2-negative tissue. In this study, we report creation of a novel bispecific antibody (BsAb) binding both EphA10 and CD3, thereby forming a bridge between antigens expressed on both tumor and immune cells and promoting recognition of tumor cells by immune cells and redirection of cytotoxic T cells (CTL). This BsAb (EphA10/CD3) was expressed in supernatants of BsAb gene-transfected cells as monomeric and dimeric molecules. Redirected T-cell lysis was observed when monomeric and dimeric BsAb were added to EphA10-overexpressing tumor cells in vitro. Furthermore, dimeric BsAb (EphA10/CD3) was more cytotoxic than monomeric BsAb, with efficient tumor cell lysis elicited by lower concentrations (≤10⁻¹ μg/mL) and a lower effector to target (E/T) cell ratio (E/T = 2.5). Dimeric BsAb (EphA10/CD3) also showed significant anti-tumor effects in human xenograft mouse models. Together, these results revealed opportunities to redirect the activity of CTL towards tumor cells that express EphA10 using the BsAb (EphA10/CD3), which could be tested in future clinical trials as a novel and potent therapeutic for breast cancer tumors.

Histone Deacetylase Inhibitors Antagonize Distinct Pathways to Suppress Tumorigenesis of Embryonal Rhabdomyosarcoma

Embryonal rhabdomyosarcoma (ERMS) is the most common soft tissue cancer in children. The prognosis of patients with relapsed or metastatic disease remains poor. ERMS genomes show few recurrent mutations, suggesting that other molecular mechanisms such as epigenetic regulation might play a major role in driving ERMS tumor biology. In this study, we have demonstrated the diverse roles of histone deacetylases (HDACs) in the pathogenesis of ERMS by characterizing effects of HDAC inhibitors, trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA; also known as vorinostat) in vitro and in vivo. TSA and SAHA suppress ERMS tumor growth and progression by inducing myogenic differentiation as well as reducing the self-renewal and migratory capacity of ERMS cells. Differential expression profiling and pathway analysis revealed downregulation of key oncogenic pathways upon HDAC inhibitor treatment. By gain-of-function, loss-of-function, and chromatin immunoprecipitation (ChIP) studies, we show that Notch1- and EphrinB1-mediated pathways are regulated by HDACs to inhibit differentiation and enhance migratory capacity of ERMS cells, respectively. Our study demonstrates that aberrant HDAC activity plays a major role in ERMS pathogenesis. Druggable targets in the molecular pathways affected by HDAC inhibitors represent novel therapeutic options for ERMS patients.

Biochemical characterization of EphA2 antagonists with improved physico-chemical properties by cell-based assays and surface plasmon resonance analysis

Amino acid conjugates of lithocholic acid (LCA) have been recently described as effective disruptors of the EphA2-ephrin-A1 interaction able to inhibit EphA2 phosphorylation in intact cells and thus able to block prometastatic responses such as cellular retraction and angiogenesis. However, these LCA-based compounds were significantly more potent at disrupting the EphA2-ephrin-A1 interaction than at blocking phenotype responses in cells, which might reflect an unclear mechanism of action or a metabolic issue responsible for a reduction of the compound concentration at the cell's surface. Through the synthesis of new compounds and their examination by a combination of cell-based assays and real-time interaction analysis by surface plasmon resonance, we showed at molecular level that l-tryptophan conjugates of lithocholic acid disrupt EphA2-ephrin-A1 interaction by targeting the EphA 2 receptor and that the presence of a polar group in position 3 of steroid scaffold is a key factor to increase the effective concentration of the compounds in cancer cell lines.

The Alternative Splicing of Cytoplasmic Polyadenylation Element Binding Protein 2 Drives Anoikis Resistance and the Metastasis of Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) represents an anomalous subset of breast cancer with a greatly reduced (30%) 5-year survival rate. The enhanced mortality and morbidity of TNBC arises from the high metastatic rate, which requires the acquisition of AnR, a process whereby anchorage-dependent cells become resistant to cell death induced by detachment. In this study TNBC cell lines were selected for AnR, and these cell lines demonstrated dramatic enhancement in the formation of lung metastases as compared with parental cells. Genetic analysis of the AnR subclones versus parental cells via next generation sequencing and analysis of global alternative RNA splicing identified that the mRNA splicing of cytoplasmic polyadenylation element binding 2 (CPEB2), a translational regulator, was altered in AnR TNBC cells. Specifically, increased inclusion of exon 4 into the mature mRNA to produce the CPEB2B isoform was observed in AnR cell lines. Molecular manipulations of CPEB2 splice variants demonstrated a key role for this RNA splicing event in the resistance of cells to anoikis. Specifically, down-regulation of the CPEB2B isoform using siRNA re-sensitized the AnR cell lines to detachment-induced cell death. The ectopic expression of CPEB2B in parental TNBC cell lines induced AnR and dramatically increased metastatic potential. Importantly, alterations in the alternative splicing of CPEB2 were also observed in human TNBC and additional subtypes of human breast cancer tumors linked to a high metastatic rate. Our findings demonstrate that the regulation of CPEB2 mRNA splicing is a key mechanism in AnR and a driving force in TNBC metastasis.

Eph receptor and ephrin function in breast, gut, and skin epithelia

Epithelial cells are tightly coupled together through specialized intercellular junctions, including adherens junctions, desmosomes, tight junctions, and gap junctions. A growing body of evidence suggests epithelial cells also directly exchange information at cell-cell contacts via the Eph family of receptor tyrosine kinases and their membrane-associated ephrin ligands. Ligand-dependent and -independent signaling via Eph receptors as well as reverse signaling through ephrins impact epithelial tissue homeostasis by organizing stem cell compartments and regulating cell proliferation, migration, adhesion, differentiation, and survival. This review focuses on breast, gut, and skin epithelia as representative examples for how Eph receptors and ephrins modulate diverse epithelial cell responses in a context-dependent manner. Abnormal Eph receptor and ephrin signaling is implicated in a variety of epithelial diseases raising the intriguing possibility that this cell-cell communication pathway can be therapeutically harnessed to normalize epithelial function in pathological settings like cancer or chronic inflammation.

Investigation of the interactions between the EphB2 receptor and SNEW peptide variants

EphB2 interacts with cell surface-bound ephrin ligands to relay bidirectional signals. Overexpression of the EphB2 receptor protein has been linked to different types of cancer. The SNEW (SNEWIQPRLPQH) peptide binds with high selectivity and moderate affinity to EphB2, inhibiting Eph-ephrin interactions by competing with ephrin ligands for the EphB2 high-affinity pocket. We used rigorous free energy perturbation (FEP) calculations to re-evaluate the binding interactions of SNEW peptide with the EphB2 receptor, followed by experimental testing of the computational results. Our results provide insight into dynamic interactions of EphB2 with SNEW peptide. While the first four residues of the SNEW peptide are already highly optimized, change of the C-terminal end of the peptide has the potential to improve SNEW-binding affinity. We identified a PXSPY motif that can be similarly aligned with several other EphB2-binding peptides.

Promiscuous and specific recognition among ephrins and Eph receptors

Eph-ephrin interactions control the signal transduction between cells and play an important role in carcinogenesis and other diseases. The interactions between Eph receptors and ephrins of the same subclass are promiscuous; there are cross-interactions between some subclasses, but not all. To understand how Eph-ephrin interactions can be both promiscuous and specific, we investigated sixteen energy landscapes of four Eph receptors (A2, A4, B2, and B4) interacting with four ephrin ligands (A1, A2, A5, and B2). We generated conformational ensembles and recognition energy landscapes starting from separated Eph and ephrin molecules and proceeding up to the formation of Eph-ephrin complexes. Analysis of the Eph-ephrin recognition trajectories and the co-evolution entropy of 400 ligand binding domains of Eph receptor and 241 ephrin ligands identified conserved residues during the recognition process. Our study correctly predicted the promiscuity and specificity of the interactions and provided insights into their recognition. The dynamic conformational changes during Eph-ephrin recognition can be described by progressive conformational selection and population shift events, with two dynamic salt bridges between EphB4 and ephrin-B2 contributing to the specific recognition. EphA3 cancer-related mutations lowered the binding energies. The specificity is not only controlled by the final stage of the interaction across the protein-protein interface, but also has large contributions from binding kinetics with the help of dynamic intermediates along the pathway from the separated Eph and ephrin to the Eph-ephrin complex.

Eph receptors: new players in Alzheimer's disease pathogenesis

Alzheimer's disease (AD) is devastating and leads to permanent losses of memory and other cognitive functions. Although recent genetic evidences strongly argue for a causative role of Aβ in AD onset and progression (Jonsson et al., 2012), its role in AD etiology remains a matter of debate. However, even if not the sole culprit or pathological trigger, genetic and anatomical evidences in conjunction with numerous pharmacological studies, suggest that Aβ peptides, at least contribute to the disease. How Aβ contributes to memory loss remains largely unknown. Soluble Aβ species referred to as Aβ oligomers have been shown to be neurotoxic and induce network failure and cognitive deficits in animal models of the disease. In recent years, several proteins were described as potential Aβ oligomers receptors, amongst which are the receptor tyrosine kinases of Eph family. These receptors together with their natural ligands referred to as ephrins have been involved in a plethora of physiological and pathological processes, including embryonic neurogenesis, learning and memory, diabetes, cancers and anxiety. Here we review recent discoveries on Eph receptors-mediated protection against Aβ oligomers neurotoxicity as well as their potential as therapeutic targets in AD pathogenesis.

Gene expression correlations in human cancer cell lines define molecular interaction networks for epithelial phenotype

Using gene expression data to enhance our knowledge of control networks relevant to cancer biology and therapy is a challenging but urgent task. Based on the premise that genes that are expressed together in a variety of cell types are likely to functions together, we derived mutually correlated genes that function together in various processes in epithelial-like tumor cells. Expression-correlated genes were derived from data for the NCI-60 human tumor cell lines, as well as data from the Broad Institute's CCLE cell lines. NCI-60 cell lines that selectively expressed a mutually correlated subset of tight junction genes served as a signature for epithelial-like cancer cells. Those signature cell lines served as a seed to derive other correlated genes, many of which had various other epithelial-related functions. Literature survey yielded molecular interaction and function information about those genes, from which molecular interaction maps were assembled. Many of the genes had epithelial functions unrelated to tight junctions, demonstrating that new function categories were elicited. The most highly correlated genes were implicated in the following epithelial functions: interactions at tight junctions (CLDN7, CLDN4, CLDN3, MARVELD3, MARVELD2, TJP3, CGN, CRB3, LLGL2, EPCAM, LNX1); interactions at adherens junctions (CDH1, ADAP1, CAMSAP3); interactions at desmosomes (PPL, PKP3, JUP); transcription regulation of cell-cell junction complexes (GRHL1 and 2); epithelial RNA splicing regulators (ESRP1 and 2); epithelial vesicle traffic (RAB25, EPN3, GRHL2, EHF, ADAP1, MYO5B); epithelial Ca(+2) signaling (ATP2C2, S100A14, BSPRY); terminal differentiation of epithelial cells (OVOL1 and 2, ST14, PRSS8, SPINT1 and 2); maintenance of apico-basal polarity (RAB25, LLGL2, EPN3). The findings provide a foundation for future studies to elucidate the functions of regulatory networks specific to epithelial-like cancer cells and to probe for anti-cancer drug targets.

EphrinB1 interacts with CNK1 and promotes cell migration through c-Jun N-terminal kinase (JNK) activation

The Eph receptors and their membrane-bound ligands, ephrins, play important roles in various biological processes such as cell adhesion and movement. The transmembrane ephrinBs transduce reverse signaling in a tyrosine phosphorylation-dependent or -independent, as well as PDZ-dependent manner. Here, we show that ephrinB1 interacts with Connector Enhancer of KSR1 (CNK1) in an EphB receptor-independent manner. In cultured cells, cotransfection of ephrinB1 with CNK1 increases JNK phosphorylation. EphrinB1/CNK1-mediated JNK activation is reduced by overexpression of dominant-negative RhoA. Overexpression of CNK1 alone is sufficient for activation of RhoA; however, both ephrinB1 and CNK1 are required for JNK phosphorylation. Co-immunoprecipitation data showed that ephrinB1 and CNK1 act as scaffold proteins that connect RhoA and JNK signaling components, such as p115RhoGEF and MKK4. Furthermore, adhesion to fibronectin or active Src overexpression increases ephrinB1/CNK1 binding, whereas blocking Src activity by a pharmacological inhibitor decreases not only ephrinB1/CNK1 binding, but also JNK activation. EphrinB1 overexpression increases cell motility, however, CNK1 depletion by siRNA abrogates ephrinB1-mediated cell migration and JNK activation. Moreover, Rho kinase inhibitor or JNK inhibitor treatment suppresses ephrinB1-mediated cell migration. Taken together, our findings suggest that CNK1 is required for ephrinB1-induced JNK activation and cell migration.

The epithelial-mesenchymal interactions: insights into physiological and pathological aspects of oral tissues

In the human biological system, the individual cells divide and form tissues and organs. These tissues are hetero-cellular. Basically any tissue consists of an epithelium and the connective tissue. The latter contains mainly mesenchymally-derived tissues with a diversified cell population. The cell continues to grow and differentiate in a pre-programmed manner using a messenger system. The epithelium and the mesenchymal portion of each tissue have two different origins and perform specific functions, but there is a well-defined interaction mechanism, which mediates between them. Epithelial mesenchymal interactions (EMIs) are part of this mechanism, which can be regarded as a biological conversation between epithelial and mesenchymal cell populations involved in the cellular differentiation of one or both cell populations. EMIs represent a process that is essential for cell growth, cell differentiation and cell multiplication. EMIs are associated with normal physiological processes in the oral cavity, such as odontogenesis, dentino-enamel junction formation, salivary gland development, palatogenesis, and also pathological processes, such as oral cancer. This paper focuses the role EMIs in odontogenesis, salivary gland development, palatogenesis and oral cancer.