Effect of reduced EPHB4 expression in thymic epithelial cells on thymocyte development and peripheral T cell function

Peripheral T-cell responses of EphB2- and EphB3-deficient mice in a model of collagen-induced arthritis

Both EphB2- and EphB3-deficient mice exhibit profound histological alterations in the thymic epithelial network but few changes in T-cell differentiation, suggesting that this organization would be sufficient to produce functional T lymphocytes. Also, other antigen-presenting cells involved in immunological education could substitute the thymic epithelium. Accordingly, we found an increased frequency of plasmacytoid dendritic cells but not of conventional dendritic cells, medullary fibroblasts or intrathymic B lymphocytes. In addition, there are no lymphoid infiltrates in the organs of mutant mice nor do they contain circulating autoantibodies. Furthermore, attempts to induce arthritic lesions after chicken type II collagen administration fail totally in EphB2-deficient mice whereas all WT and half of the immunized EphB3-/- mice develop a typical collagen-induced arthritis. Our results point out that Th17 cells, IL4-producing Th2 cells and regulatory T cells are key for the induction of disease, but mutant mice appear to have deficits in T cell activation or cell migration properties. EphB2-/- T cells show reduced in vitro proliferative responses to anti-CD3/anti-CD28 antibodies, produce low levels of anti-type II collagen antibodies, and exhibit low proportions of T follicular helper cells. On the contrary, EphB3-/- lymph node cells respond accurately to the different immune stimuli although in lower levels than WT cells but show a significantly reduced migration in in vitro transwell assays, suggesting that no sufficient type II collagen-dependent activated lymphoid cells reached the joints, resulting in reduced arthritic lesions.

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.

Transcriptional Signatures That Define Ulcerative Colitis in Remission

BACKGROUND

This study addresses whether existing specific transcriptional profiles can improve and support the current status of the definition of ulcerative colitis (UC) remission apart from the existing endoscopic, histologic, and laboratory scoring systems. For that purpose, a well-stratified UC patient population in remission was compared to active UC and control patients and was investigated by applying the next-generation technology RNA-Seq.

METHODS

Mucosal biopsies from patients in remission (n = 14), patients with active UC (n = 14), and healthy control patientss (n = 16) underwent whole-transcriptome RNA-Seq. Principal component analysis, cell deconvolution methods, gene profile enrichment, and pathway enrichment methods were applied to define a specific transcriptional signature of UC in remission.

RESULTS

Analyses revealed specific transcriptional signatures for UC in remission with increased expression of genes involved in O-glycosylation (MUC17, MUC3A, MUC5AC, MUC12, SPON1, B3GNT3), ephrin-mediated repulsion of cells (EFNB2E, EFNA3, EPHA10, EPHA1), GAP junction trafficking (TUBA1C, TUBA4A, TUBB4B, GJB3, CLTB), and decreased expression of several toll-like receptors (TLR1, TLR3, TLR5, TLR6).

CONCLUSIONS

This study reveals specific transcriptional signatures for remission. Partial restoration and improvement of homeostasis in the epithelial mucus layer and revival of immunological functions were observed. A clear role for bacterial gut flora composition can be implied. The results can be useful for the development of treatment strategies for UC in remission and may be useful targets for further investigations aiming to predict the outcome of UC in the future.

Intrathymic Selection and Defects in the Thymic Epithelial Cell Development

Intimate interactions between thymic epithelial cells (TECs) and thymocytes (T) have been repeatedly reported as essential for performing intrathymic T-cell education. Nevertheless, it has been described that animals exhibiting defects in these interactions were capable of a proper positive and negative T-cell selection. In the current review, we first examined distinct types of TECs and their possible role in the immune surveillance. However, EphB-deficient thymi that exhibit profound thymic epithelial (TE) alterations do not exhibit important immunological defects. Eph and their ligands, the ephrins, are implicated in cell attachment/detachment and govern, therefore, TEC–T interactions. On this basis, we hypothesized that a few normal TE areas could be enough for a proper phenotypical and functional maturation of T lymphocytes. Then, we evaluated in vivo how many TECs would be necessary for supporting a normal T-cell differentiation, concluding that a significantly low number of TEC are still capable of supporting normal T lymphocyte maturation, whereas with fewer numbers, T-cell maturation is not possible.

Targeting the Eph/Ephrin System as Anti-Inflammatory Strategy in IBD

Besides their long-known critical role in embryonic growth and in cancer development and progression, erythropoietin-producing hepatocellular carcinoma type B (EphB) receptor tyrosine kinases and their ephrin-B ligands are involved in the modulation of immune responses and in remodeling and maintaining the integrity of the intestinal epithelial layer. These processes are critically involved in the pathogenesis of inflammatory-based disorders of the gut, like inflammatory bowel diseases (IBDs). Accordingly, our aim was to investigate the role of the EphB/ephrin-B system in intestinal inflammation by assessing the local and systemic effects produced by its pharmacological manipulation in 2,4,6-trinitrobenzenesulfonic acid (TNBS)- (Th1-dependent model) and dextran sulphate sodium (DSS)- (innate response model) induced colitis in mice. To this purpose, we administered chimeric Fc-conjugated proteins, allegedly able to uni-directionally activate either forward (ephrin-B1-Fc) or reverse (EphB1-Fc) signaling, and the soluble monomeric EphB4 extracellular domain protein, that, simultaneously interfering with both signaling pathways, acts as EphB/ephrin-B antagonist.The blockade of the EphB/ephrin-B forward signaling by EphB4 and EphB1-Fc was ineffective against DSS-induced colitis while it evoked remarkable beneficial effects against TNBS colitis: it counteracted all the evaluated inflammatory responses and the changes elicited on splenic T lymphocytes subpopulations, without preventing the appearance of a splice variant of ephrin-B2 gene elicited by the haptenating agent in the colon. Interestingly, EphB4, preferentially displacing EphB4/ephrin-B2 interaction over EphB1/ephrin-B1 binding, was able to promote Tumor Necrosis Factor alpha (TNFα) release by splenic mononuclear cells in vitro. On the whole, the collected results point to a potential role of the EphB/ephrin-B system as a pharmacological target in intestinal inflammatory disorders and suggest that the therapeutic efficacy of its blockade seemingly works through the modulation of immune responses, independent of the changes at the transcriptional and translational level of EphB4 and ephrin-B2 genes.

EPHB6 controls catecholamine biosynthesis by up-regulating tyrosine hydroxylase transcription in adrenal gland chromaffin cells

EPHB6 is a member of the erythropoietin-producing hepatocellular kinase (EPH) family and a receptor tyrosine kinase with a dead kinase domain. It is involved in blood pressure regulation and adrenal gland catecholamine (CAT) secretion, but several facets of EPHB6-mediated CAT regulation are unclear. In this study, using biochemical, quantitative RT-PCR, immunoblotting, and gene microarray assays, we found that EPHB6 up-regulates CAT biosynthesis in adrenal gland chromaffin cells (AGCCs). We observed that epinephrine content is reduced in the AGCCs from male Ephb6-KO mice, caused by decreased expression of tyrosine hydroxylase, the rate-limiting enzyme in CAT biosynthesis. We demonstrate that the signaling pathway from EPHB6 to tyrosine hydroxylase expression in AGCCs involves Rac family small GTPase 1 (RAC1), MAP kinase kinase 7 (MKK7), c-Jun N-terminal kinase (JNK), proto-oncogene c-Jun, activator protein 1 (AP1), and early growth response 1 (EGR1). On the other hand, signaling via extracellular signal-regulated kinase (ERK1/2), p38 mitogen-activated protein kinase, and ELK1, ETS transcription factor (ELK1) was not affected by EPHB6 deletion. We further report that EPHB6's effect on AGCCs was via reverse signaling through ephrin B1 and that EPHB6 acted in concert with the nongenomic effect of testosterone to control CAT biosynthesis. Our findings elucidate the mechanisms by which EPHB6 modulates CAT biosynthesis and identify potential therapeutic targets for diseases, such as hypertension, caused by dysfunctional CAT biosynthesis.

Analysis of the association of EPHB6, EFNB1 and EFNB3 variants with hypertension risks in males with hypogonadism

Several members of the EPH kinase family and their ligands are involved in blood pressure regulation, and such regulation is often sex- or sex hormone-dependent, based on animal and human genetic studies. EPHB6 gene knockout (KO) in mice leads to hypertension in castrated males but not in un-manipulated KO males or females. To assess whether this finding in mice is relevant to human hypertension, we conducted a human genetic study for the association of EPHB6 and its two ligands, EFNB1 and EFNB3, with hypertension in hypogonadic patients. Seven hundred and fifty hypertensive and 750 normotensive Han Chinese patients, all of whom were hypogonadic, were genotyped for single nucleotide polymorphisms (SNPs) within the regions of the genes, plus an additional 50 kb 5′ of the genes for EPHB6, EFNB1 and EFNB3. An imputed insertion/deletion polymorphism, rs35530071, was found to be associated with hypertension at p-values below the Bonferroni-corrected significance level of 0.0024. This marker is located 5′ upstream of the EFNB3 gene start site. Previous animal studies showed that while male EFNB3 gene knockout mice were normotensive, castration of these mice resulted in hypertension, corroborating the results of the human genetic study. Considering the significant associations of EFNB3 SNPs with hypertension in hypogonadic males and supporting evidence from castrated EFNB3 KO mice, we conclude that loss-of-function variants of molecules in the EPHB6 signaling pathway in the presence of testosterone are protective against hypertension in humans.

[Development of a Fundamental Technology to Seek Drug Targets, and Its Application to Cancer Targeting Therapy]

　Human epidermal growth factor receptor 2 (Her2)-targeting antibodies and anti-hormone therapy are effective for most breast cancer patients. However, such approaches are not viable with resistant cases or in triple-negative breast cancer (TNBC) patients, given the lack of Her2 and estrogen and progesterone receptors in these patients. Thus, new drug targets are urgently required. From this perspective, we searched for novel drug targets using proteomic analysis, and identified Eph receptor A10 (EphA10), which is elevated in breast cancer cells as compared to normal breast tissue. Here, we evaluated the potential of EphA10 as a drug target by analyzing its protein expression profile/function in cancer cells, and then by using an anti-EphA10 antibody to treat EphA10-expressing tumor-bearing mice. Protein expression profile analysis showed that EphA10 was expressed in various breast cancer subtypes, including TNBCs, with no expression observed in normal tissues, apart from the testes. Moreover, functional analysis of the cancer cells revealed that ligand-dependent proliferation was observed in EphA10-expressed cancer cells. Thus, we developed our novel anti-EphA10 antibody, which binds to EphA10 with high specificity and affinity at the nanomolar level. Finally, therapeutic analysis indicated that tumor growth was significantly suppressed in the mAb-treated mice in a dose-dependent manner. These results suggest that the EphA10-targeting therapy may be a novel therapeutic option for the management of breast cancer, including in TNBCs which aren't currently treated with molecular-targeted agents. Consequently, we hope that these findings will contribute to the development of a new targeting therapy for refractory breast cancer patients.

Altered Maturation of Medullary TEC in EphB-Deficient Thymi Is Recovered by RANK Signaling Stimulation

In the present study, the relevance of EphB2 and EphB3 tyrosine kinase receptors for the maturation of medullary thymic epithelial cells (TECs) is analyzed. The absence of both molecules, but particularly that of EphB2, courses with altered maturation of medullary Cld3,4^hiSSEA1⁺ epithelial progenitor cells, mature medulla epithelial cells, defined by the expression of specific cell markers, including UEA1, MHCII, CD40, CD80, and AIRE, and reduced expansion of medullary islets. In vivo assays demonstrate that these changes are a consequence of the absence of EphBs in both TECs and thymocytes. On the other hand, the changes, that remains in the adult thymus, correlated well with reduced proportions of E15.5 Vγ5⁺RANKL⁺ cells in EphB-deficient thymi that could result in decreased stimulation of RANK⁺ medullary TECs to mature, a fact that was confirmed by recovering of proportions of both CD40^hiCD80⁺ and MHCII^hiUEA1⁺ mature medullary TECs of mutant E14.5 alymphoid thymic lobes by agonist anti-RANK antibody treatment. Accordingly, the effects of EphB deficiency on medullary TECs maturation are recovered by RANK stimulation.

Can a Proper T-Cell Development Occur in an Altered Thymic Epithelium? Lessons From EphB-Deficient Thymi

For a long time, the effects of distinct Eph tyrosine kinase receptors and their ligands, ephrins on the structure, immunophenotype, and development of thymus and their main cell components, thymocytes (T) and thymic epithelial cells (TECs), have been studied. In recent years, the thymic phenotype of mutant mice deficient in several Ephs and ephrins B has been determined. Remarkably, thymic stroma in these animals exhibits important defects that appear early in ontogeny but little alterations in the proportions of distinct lymphoid cell populations. In the present manuscript, we summarize and extend these results discussing possible mechanisms governing phenotypical and functional thymocyte maturation in an absence of the critical T-TEC interactions, concluding that some signaling mediated by key molecules, such as MHCII, CD80, β5t, Aire, etc. could be sufficient to enable a proper maturation of thymocytes, independently of morphological alterations affecting thymic epithelium.

EPHB6 and testosterone in concert regulate epinephrine release by adrenal gland chromaffin cells

Erythropoietin-producing human hepatocellular receptor (EPH) B6 (EPHB6) is a member of the receptor tyrosine kinase family. We previously demonstrated that EPHB6 knockout reduces catecholamine secretion in male but not female mice, and castration reverses this phenotype. We showed here that male EPHB6 knockout adrenal gland chromaffin cells presented reduced acetylcholine-triggered Ca2+ influx. Such reduction depended on the non-genomic effect of testosterone. Increased large conductance calcium-activated potassium channel current densities were recorded in adrenal gland chromaffin cells from male EPHB6 knockout mice but not from castrated knockout or female knockout mice. Blocking of the large conductance calcium-activated potassium channel in adrenal gland chromaffin cells from male knockout mice corrected their reduced Ca2+ influx. We conclude that the absence of EPHB6 and the presence of testosterone would lead to augmented large conductance calcium-activated potassium channel currents, which limit voltage-gated calcium channel opening in adrenal gland chromaffin cells. Consequently, acetylcholine-triggered Ca2+ influx is reduced, leading to lower catecholamine release in adrenal gland chromaffin cells from male knockout mice. This explains the reduced resting-state blood catecholamine levels, and hence the blood pressure, in male but not female EPHB6 knock mice. These findings have certain clinical implications.

Aberrant EPHB4 gene methylation and childhood acute lymphoblastic leukemia

The present study aimed to investigate the association between aberrant DNA methylation of the promoter region of the ephrin type-B receptor 4 (EPHB4) gene and the development of childhood acute lymphoblastic leukemia (ALL). Bisulfite sequencing polymerase chain reaction (BSP) was performed to determine the methylation density of cytosine-guanine pair islands in the promoter region of EPHB4, in bone marrow samples from 40 children with ALL. The mRNA and protein expression levels of EPHB4 were detected using reverse transcription-quantitative polymerase chain reaction and western blot analysis. A total of 10 children with idiopathic thrombocytopenic purpura (ITP) were recruited as controls. The results revealed that the average methylation density of the bone marrow samples from the patients with ALL was significantly higher, compared with the patients with ITP (P=0.046). The relative mRNA expression levels of EPHB4 in the patients with ITP (25.08±4.03) and the patients with ALL without methylation (12.33±2.16) were significantly higher, compared with that observed in the patients with ALL with methylation (6.48±2.73; P<0.01). Pearson analysis revealed a significant negative linear correlation between EPHB4 gene methylation and its expression levels (r=−0.957; P<0.01). Western blot analysis indicated that EPHB4 protein expression levels were low in the methylated ALL samples. An evaluation of the two-year disease-free survival (DFS) of the patients with ALL was performed, which revealed that the patients with unmethylated ALL exhibited a significantly higher two-year DFS rate, as compared with patients with methylated ALL (P=0.036). These results suggest that the methylation of the EPHB4 gene is prevalent in childhood ALL and may result in expressional inactivation, which consequently promotes ALL pathogenesis and is associated with an unfavorable prognosis. Therefore, the EPHB4 gene may function as a potential tumor suppressor in childhood ALL.

[Challenge to the Development of Molecular Targeted Therapy against a Novel Target Candidate Identified by Antibody Proteomics Technology]

Disease proteomics that systemically analyzes and identifies differentially expressed proteins between healthy and diseased samples is a potentially useful approach for obtaining target proteins for drug development. To date, however, very few target proteins have been identified from this field. A key issue that remains to be resolved is how to correctly identify target proteins from a number of potential candidates. To circumvent this problem, we have developed "antibody proteomics technology" in which a single chain Fv phage antibody library is utilized for proteome analysis. Here, we describe the application of this technology by primarily focusing on Eph receptor A10 (EphA10), a novel breast cancer-related protein that is a promising target for antibody drugs. To establish an effective and safe targeted cancer therapy, it is important that the target is specifically expressed in cancer tissues. Therefore, we attempted to analyze the EphA10 expression profiles. Tissue microarray analysis showed that EphA10 was expressed in all subtypes of breast cancer containing triple negative breast cancer cases. On the other hand, EphA10 was only expressed in testis tissue among 36 kinds of normal tissues. Thus, EphA10 could be a highly cancer-specific protein, making it a promising target for female breast cancer patients. Finally, we examined the anti-tumor effect by anti-EphA10 antibody, aiming for the development of a novel EphA10 targeting therapy. Administration of the antibody showed that tumor volumes were significantly inhibited. Our results suggest that targeting EphA10 in breast cancer cases might be a promising new form of therapy.

Conditioned deletion of ephrinB1 and/or ephrinB2 in either thymocytes or thymic epithelial cells alters the organization of thymic medulla and favors the appearance of thymic epithelial cysts

Our understanding about medullary compartment, its niches composition and formation is still limited. Previous studies using EphB2 and/or EphB3 knockout mice showed an abnormal thymic development that affects mainly to the epithelial component, including the cortex/medulla distribution, thymic epithelial cell (TEC) morphology and different epithelial-specific marker expression. We have already demonstrated that the lack of ephrinB1 and/or ephrinB2, either on thymocytes or on TECs, alters the cell intermingling processes necessary for thymus organization and affect cortical TEC subpopulations. In the present work, we have used the Cre-LoxP model to selectively delete ephrinB1 and/or ephrinB2 in thymocytes (EfnB1(thy/thy), EfnB2(thy/thy), EfnB1(thy/thy)EfnB2(thy/thy) mice) or TECs (EfnB1(tec/tec), EfnB2(tec/tec), EfnB1(tec/tec)EfnB2(tec/tec) mice) and have analyzed their role on the medullary compartment. In all the studied mutants, medullary areas are smaller and more compact than in the wt thymuses. In most of them, we observe abundant big cysts and a higher proportion of UEA(hi)MTS10(-) cells than in wt mice, which are often forming small cysts. On EfnB1(tec/tec)EfnB2(tec/tec), changes affecting organ size and medullary compartment start at perinatal stage. Our data shed some light on knowledge about wt medulla histological structure and cysts meaning and formation process and on the role played by ephrinB in them.