Eph receptors and ephrins: therapeutic opportunities

Cataract-related mutations in EphA2: a survey of literature data and the relevance of the receptor Sam domain

INTRODUCTION

EphA2 is a receptor tyrosine kinase that is associated with various pathological conditions. Mutations in EphA2 are linked to cataract, an eye disorder manifesting as lens opacity, and representing one of the most prominent causes of blindness worldwide.

AREAS COVERED

We collected a list of cataract-related EphA2 mutations and positioned them inside the different protein domains to identify regions of the receptor that could be more likely considered targets in the 'anti-cataract' drug discovery field. Moreover, we analyzed the structural consequences these mutations could induce. A search for literature related to EphA2 and cataracts was carried out through the Pubmed National Library of Medicine. Structural information on diverse EphA2 domains was obtained from the Protein Data Bank. EphA2 variants connected to cataract were checked on the databases Cat-Map and dbSNP.

EXPERT OPINION

Cataract-related mutations are gathered within diverse EphA2 domains and are abundant inside its Sam (Sterile alpha motif, EphA2-Sam) domain. Mutations affecting EphA2-Sam could disturb domain helical fold and hamper interaction with other Sam domains eventually interfering with EphA2 cell migration activity. Identification of stabilizing small molecules targeting EphA2-Sam pathogenic variants could represent an original route to discover novel therapeutic compounds against lens opacity.

Genetic determinants of paclitaxel-induced peripheral neuropathy: a review of current literature

Paclitaxel is a widely used chemotherapeutic agent recognized for its efficacy against various malignancies. However, its clinical utility is often limited by paclitaxel-induced peripheral neuropathy (PIPN), a dose-dependent and debilitating side effect that significantly impacts patient quality of life. Genetic predisposition plays a critical role in individual susceptibility to PIPN, influencing both drug metabolism and neuropathic responses. This review examines the genetic basis of PIPN, focusing on polymorphisms in key genes associated with paclitaxel metabolism, transport, neuroinflammation, and neuronal signaling. Variants in CYP2C8, CYP3A4, and CYP2C9 affect drug metabolism, while polymorphisms in ABCB1 and SLCO1B1 influence drug transport. Genes involved in neuroinflammatory pathways (TNF-α, IL-6, IL-1β), peripheral nerve integrity (MAPT, TUBB2), and neuronal signaling (SCN9A) have also been implicated in PIPN susceptibility. Understanding genetic contributions to PIPN is essential for unraveling its pathophysiology and developing targeted interventions. Integrating genetic markers into clinical practice can facilitate personalized treatment strategies, minimizing PIPN risk and enhancing therapeutic outcomes. Further studies are needed to validate these findings across diverse populations and uncover novel genetic determinants.

EPHA5 promotes cell proliferation and inhibits apoptosis in Follicular Thyroid Cancer via the STAT3 signaling pathway

Follicular thyroid carcinoma (FTC) is a common endocrine malignancy characterized by a higher propensity for invasion and metastasis compared to papillary thyroid carcinoma (PTC). Ephrin type A receptor 5 (EPHA5) is a crucial receptor tyrosine kinase involved in orchestrating diverse physiological processes, including apoptosis and proliferation. However, the mechanism of EPHA5 in FTC remains unclear. This study identified significant overexpression of EPHA5 in FTC. In vitro experiments showed that increased expression of EPHA5 promotes proliferation and inhibits apoptosis in FTC. Furthermore, EPHA5 activates the STAT3 signaling pathway. To explore the interaction between EPHA5 and the STAT3 signaling pathway, we used SH-4-54 (a STAT3-specific inhibitor). Interestingly, the influence of EPHA5 on proliferation and apoptosis was reduced upon combination with SH-4-54. In summary, this study unveils the involvement of the EPHA5-STAT3 signaling pathway in FTC and implies that the function of EPHA5 in FTC may partly depend on the STAT3 signaling pathway.

Cholesterol-dependent dimerization and conformational dynamics of EphA2 receptors from coarse-grained and all-atom simulations

The EphA2 transmembrane receptor regulates cellular growth, differentiation, and motility, and its overexpression in various cancers makes it a potential biomarker for clinical cancer management. EphA2 signaling occurs through ligand-induced dimerization where the transmembrane (TM) and juxtamembrane (JM) domains play crucial roles in stabilizing the dimer conformations, thereby facilitating signal transduction. Electrostatic interactions between basic JM residues and signaling lipids (PIP2 and PIP3) regulate phosphorylation while cholesterol's potential role in modulating EphA2 activation remains unclear. To investigate this, we modeled the TM-full JM peptide of EphA2 and employed coarse-grain and all-atom simulations to investigate its dimerization in cholesterol-rich and cholesterol-deficient membranes. Our findings reveal that cholesterol stabilizes specific TM dimers and TM-JM interactions with PIP2, highlighting the importance of membrane composition in EphA2 dimerization, oligomerization, and clustering. These insights enhance our understanding of lipid-mediated regulation of EphA2 and its implications in receptor signaling and cancer progression.

Role of EFNAs in Shaping the Tumor Immune Microenvironment and Their Impact on Pancreatic Adenocarcinoma Prognosis

Purpose

Due to the highly heterogeneous and immunosuppressed tumor microenvironment (TME), pancreatic adenocarcinoma (PAAD) has limited therapeutic options and an abysmal prognosis. Ephrin A 1-5 (EFNA1-5) have been shown to regulate tumorigenesis and metastasis in various cancers, but its role in PAAD remains unclear.

Methods

We comprehensively analyzed EFNA gene expression levels in pan-cancer and PAAD using the GEPIA and HPA databases. Then, we assessed the prognostic value of EFNA1-5 using the Kaplan-Meier plotter and nomogram model. Further exploration of the association of EFNA1-5 with clinicopathological features of PAAD used information from the UALCAN database, and the TIMER dataset was used to reveal the correlation between EFNA1-5 and the tumor immune microenvironment (TIME) of pancreatic cancer. In addition, cBioPortal Databases, GSEA, and GSCALite were used to explore gene changes, protein interactions, and biological functions. Finally, the oncogenic effect of EFNA5 was verified in vivo and in vitro.

Results

The expression levels of EFNA1-5 were significantly upregulated in PAAD. The expression of EFNA1/3/4/5 were significantly associated with overall survival (OS) and relapse-free survival (RFS) in PAAD patients. The high expression of EFNA2-5 were related to poor clinical features, such as higher tumor stage or grade and a wider range of lymph node metastasis. EFNA1-5 were closely associated with immune cell infiltration, CAFs, and MDSCs expression. Furthermore, EFNA5 is an independent risk factor for poor prognosis in PAAD patients, and it can promote the malignant progression of pancreatic cancer in vitro and in vivo.

Conclusion

Differential expression of EFNA1-5 is associated with TIME in pancreatic cancer, predicts different survival outcomes, and maybe a novel prognostic marker reflecting an immunosuppressive state and a potential therapeutic target.

Cholesterol-Dependent Dimerization and Conformational Dynamics of EphA2 Receptors: Insights from Coarse-Grained and All-Atom Simulations

The EphA2 transmembrane receptor regulates cellular growth, differentiation, and motility, and its overexpression in various cancers makes it a potential biomarker for clinical cancer management. EphA2 signaling occurs through ligand-induced dimerization, where the transmembrane (TM) and juxtamembrane (JM) domains play crucial roles in stabilizing the dimer conformations and thereby facilitating signal transduction. Electrostatic interactions between basic JM residues and signaling lipids (PIP2 and PIP3) regulate phosphorylation while Cholesterol's potential role in modulating EphA2 activation remains unclear. To investigate this, we modeled the TM-full JM peptide of EphA2 and employed coarse-grain and all-atom simulations to investigate its dimerization in cholesterol-rich and cholesterol-deficient membranes. Our findings reveal that cholesterol stabilizes specific TM dimers and TM-JM interactions with PIP2, highlighting the importance of membrane composition in EphA2 dimerization, oligomerization, and clustering. These insights enhance our understanding of lipid-mediated regulation of EphA2 and its implications in receptor signaling and cancer progression.

Differential association of EphA2 intracellular regions in biased signaling

Biased signaling is the ability of a receptor to differentially activate certain signaling cascades in response to different ligands. Our previous work demonstrated that the monomeric ephrinA1 ligand and the widely used dimeric ephrinA1-Fc ligand induced EphA2 receptor tyrosine kinase (RTK)-biased signaling. The hypothesis that RTK biased signaling is a consequence of differential interactions between receptor intracellular regions when different ligands are bound to the extracellular region has not been experimentally verified thus far, in part because of the lack of high-resolution structures of full-length RTK oligomers. Here, we compare the effects of deletion of intracellular regions in EphA2 oligomers bound to the biased ligands, monomeric ephrinA1 or ephrinA1-Fc. Our data reveal distinct differences in the intracellular organization of EphA2 oligomers bound to the two ligands, supporting the hypothesis. They also suggest that EphA2 signaling could be modulated by agents that alter interactions between oligomerized EphA2 intracellular regions by binding at sites that can be distant from the ATP-binding pocket.

N-glycosylation of ephrin B1 modulates its function and confers therapeutic potential in B-cell lymphoma

Given the pivotal role of the Eph-Ephrin signaling pathway in tumor progression, agonists or antagonists targeting Eph-Ephrin have emerged as promising anticancer strategies. However, the implications of glycosylation modifications within Eph-Ephrin and their targeted protein therapeutics remain elusive. Here, we identify that N-glycosylation within the receptor-binding domain (RBD) of ephrin B1 (EFNB1) is indispensable for its functional repertoire. Notably, compared with wildtype EFNB1, the glycosylation-deficient N139D mutant drastically diminishes the sensitivity of tumor cells with chemotherapeutic agents, suggesting the existence of both glycosylation-dependent and -independent effects mediated by EFNB1. Transcriptomic analysis highlights immune response and oxidative phosphorylation as the primary signaling pathways modulated by glycosylation modifications. In coculture systems, the EFNB1-RBD-Fc recombinant protein, while inhibiting B-lymphoma cells, also exerts differential impacts on stromal cells depending on their glycosylation status. Furthermore, the efficacy of both glycosylated and nonglycosylated EFNB1-RBD-Fc is influenced by the endogenous EFNB1 levels within tumor cells. Taking together, this study demonstrates the complexity and multifaceted roles of glycosylation in modulating EFNB1 function. These findings underscore the need for a nuanced understanding of glycosylation patterns in Eph-Ephrin-targeted therapies to optimize their therapeutic potential.

Astrocytic EphA4 signaling is important for the elimination of excitatory synapses in Alzheimer's disease

Cell surface receptors, including erythropoietin-producing hepatocellular A4 (EphA4), are important in regulating hippocampal synapse loss, which is the key driver of memory decline in Alzheimer's disease (AD). However, the cell-specific roles and mechanisms of EphA4 are unclear. Here, we show that EphA4 expression is elevated in hippocampal CA1 astrocytes in AD conditions. Specific knockout of astrocytic EphA4 ameliorates excitatory synapse loss in the hippocampus in AD transgenic mouse models. Single-nucleus RNA sequencing analysis revealed that EphA4 inhibition specifically decreases a reactive astrocyte subpopulation with enriched complement signaling, which is associated with synapse elimination by astrocytes in AD. Importantly, astrocytic EphA4 knockout in an AD transgenic mouse model decreases complement tagging on excitatory synapses and excitatory synapses within astrocytes. These findings suggest an important role of EphA4 in the astrocyte-mediated elimination of excitatory synapses in AD and highlight the crucial role of astrocytes in hippocampal synapse maintenance in AD.

Missense mutations of the ephrin receptor EPHA1 associated with Alzheimer's disease disrupt receptor signaling functions

Missense mutations in the EPHA1 receptor tyrosine kinase have been identified in Alzheimer's patients. To gain insight into their potential role in disease pathogenesis, we investigated the effects of four of these mutations. We show that the P460L mutation in the second fibronectin type III (FN2) domain drastically reduces EPHA1 cell surface localization while increasing tyrosine phosphorylation of the cell surface-localized receptor. The R791H mutation in the kinase domain abolishes EPHA1 tyrosine phosphorylation, indicating abrogation of kinase-dependent signaling. Furthermore, both mutations decrease EPHA1 phosphorylation on S906 in the kinase-SAM linker region, suggesting impairment of a noncanonical form of signaling regulated by serine/threonine kinases. The R492Q mutation, also in the FN2 domain, has milder effects than the P460L mutation while the R926C mutation in the SAM domain increases S906 phosphorylation. We also found that EPHA1 undergoes constitutive proteolytic cleavage in the FN2 domain, generating a soluble 55 kDa N-terminal fragment containing the ligand-binding domain and a transmembrane 60 kDa C-terminal fragment. The 60 kDa WT fragment is phosphorylated on both tyrosine residues and S906, suggesting signaling functions. The P460L mutant 60 kDa fragment undergoes proteasomal degradation and the R791H mutant fragment lacks tyrosine phosphorylation and has decreased S906 phosphorylation. These findings advance our understanding of EPHA1 signaling mechanisms and support the notion that alterations in EPHA1 signaling due to missense mutations contribute to Alzheimer's disease pathogenesis.

EphA2 regulates vascular permeability and prostate cancer metastasis via modulation of cell junction protein phosphorylation

Prostate cancer morbidity and mortality demonstrate a need for more effective targeted therapies. One potential target is EphA2, although paradoxically, pro- and anti-oncogenic effects have been shown to be mediated by EphA2. We demonstrate that unique activating and blocking EphA2-targeting monoclonal antibodies display opposing tumor-suppressive and oncogenic properties in vivo. To further explore this complexity, we performed detailed phosphoproteomic analysis following ligand-induced EphA2 activation. Our analysis identified altered phosphorylation of 73 downstream proteins related to the PI3K/AKT/mTOR and ERK/MAPK pathways, with the majority implicated in cell junction and cytoskeletal organization, cell motility, and tumor metastasis. We demonstrate that the adapter protein SHB is an essential component in mediating the inhibition of the ERK/MAPK pathway in response to EphA2 receptor activation. Furthermore, we identify the adherence junction protein afadin as an EphA2-regulated phosphoprotein which is involved in prostate cancer migration and invasion.

Reciprocal tumor-platelet interaction through the EPHB1-EFNB1 axis in the liver metastatic niche promotes metastatic tumor outgrowth in pancreatic ductal adenocarcinoma

BACKGROUND

The interaction between the metastatic microenvironment and tumor cells plays an important role in metastatic tumor formation. Platelets play pivotal roles in hematogenous cancer metastasis through tumor cell-platelet interaction in blood vessels. Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy distinguished by its notable tendency to metastasize to the liver. However, the role of platelet in the liver metastatic niche of PDAC remains elusive. This study aimed to elucidate the role of platelets and their interactions with tumor cells in the liver metastatic niche of PDAC.

METHODS

An mCherry niche-labeling system was established to identify cells in the liver metastatic niche of PDAC. Platelet depletion in a liver metastasis mouse model was used to observe the function of platelets in PDAC liver metastasis. Gain-of-function and loss-of-function of erythropoietin-producing hepatocellular receptor B1 (Ephb1), tumor cell-platelet adhesion, recombinant protein, and tryptophan hydroxylase 1 (Tph1)-knockout mice were used to study the crosstalk between platelets and tumor cells in the liver metastatic niche.

RESULTS

The mCherry metastatic niche-labeling system revealed the presence of activated platelets in the liver metastatic niche of PDAC patients. Platelet depletion decreased liver metastatic tumor growth in mice. Mechanistically, tumor cell-expressed EPHB1 and platelet-expressed Ephrin B1 (EFNB1) mediated contact-dependent activation of platelets via reverse signaling-mediated AKT signaling activation, and in turn, activated platelet-released 5-HT, further enhancing tumor growth.

CONCLUSION

We revealed the crosstalk between platelets and tumor cells in the liver metastatic niche of PDAC. Reciprocal tumor-platelet interaction mediated by the EPHB1-EFNB1 reverse signaling promoted metastatic PDAC outgrowth via 5-HT in the liver. Interfering the tumor-platelet interaction by targeting the EPHB1-EFNB1 axis may represent a promising therapeutic intervention for PDAC liver metastasis.

Germline alteration analysis reveals EPHB4R91H mutation as a key player in multiple primary lung tumors

Multiple primary lung tumors are garnering attention from clinicians, with adenocarcinoma emerging as the predominant histological type. Because of the heterogeneity and diffuse distribution of lesions in the same patient, the treatment of multiple primary lung adenocarcinoma (MPLA) is a significant challenge. As a kind of variation unaffected by tumor heterogeneity, germline alterations may play a key role in the development of MPLA. Here, whole-exome sequencing of peripheral blood was employed to obtain germline alteration data. Intergroup comparative analyses on rare and deleterious alterations of MPLA, solitary lung adenocarcinoma, and healthy individuals in an MPLA family were performed to clarify the candidate alterations. Whole-exome sequencing and targeted Sanger sequencing were performed in 27 disseminated MPLA patients to detect the mutation site that had been screened. A rare and deleterious germline alteration, EPHB4R91H, was found in all of the patients of an MPLA family and a patient with disseminated MPLA. It was revealed that EPHB4R91H was able to enhance the proliferation, migration, and invasion ability of A549 cells through increased binding affinity to ephrinB2, which in turn activated the EPHB4/ERK/JNK/MAPK pathway. Our findings corroborate that germline alterations are involved in the development of MPLA. And it was found for the first time that the EPHB4R91H mutation promotes the development of MPLA by enhancing its affinity for ephrinB2 and thereby active EPHB4/ERK/JNK/MAPK pathway.

Eph receptor signaling complexes in the plasma membrane

Eph receptor tyrosine kinases, together with their cell surface-anchored ephrin ligands, constitute an important cell-cell communication system that regulates physiological and pathological processes in most cell types. This review focuses on the multiple mechanisms by which Eph receptors initiate signaling via the formation of protein complexes in the plasma membrane. Upon ephrin binding, Eph receptors assemble into oligomers that can further aggregate into large complexes. Eph receptors also mediate ephrin-independent signaling through interplay with intracellular kinases or other cell-surface receptors. The distinct characteristics of Eph receptor family members, as well as their conserved domain structure, provide a framework for understanding their functional differences and redundancies. Possible areas of interest for future investigations of Eph receptor signaling complexes are also highlighted.

EphA2 in Cancer: Molecular Complexity and Therapeutic Opportunities

Erythropoietin-producing hepatocellular A2 (EphA2) is a member of the Eph tyrosine kinase receptor family that has been linked to various biological processes. In tumors, EphA2 overexpression is associated with noncanonical pathway activation, tumor progression, and a poor prognosis, which has emphasized its importance as a marker of malignancy. Studies on numerous cancer models have highlighted EphA2's dual and often contradictory action, which can be attributed to EphA2's interactions involving multiple pathways and different ligands, as well as the heterogeneity of the tumor microenvironment. In this review, we summarize the main mechanisms underlying EphA2 dysregulation in cancer, highlighting its molecular complexity. Then, we analyze therapies that have been developed over time to counteract its action. We discuss the limitations of the described approaches, emphasizing the fact that the goal of new options is high specificity without losing therapeutic efficacy. For this reason, immunotherapy or the emerging field of targeted protein degradation with proteolysis-targeting chimeras (PROTACs) may represent a promising solution that can be developed based on a deeper understanding of the molecular mechanisms sustaining EphA2 oncogenic activity.

EPHB4-RASA1 Inhibition of PIEZO1 Ras Activation Drives Lymphatic Valvulogenesis

BACKGROUND

EPHB4 (ephrin receptor B4) and the RASA1 (p120 Ras GTPase-activating protein) are necessary for the development of lymphatic vessel (LV) valves. However, precisely how EPHB4 and RASA1 regulate LV valve development is unknown. In this study, we examine the mechanisms by which EPHB4 and RASA1 regulate the development of LV valves.

METHODS

We used LV-specific inducible EPHB4-deficient mice and EPHB4 knockin mice that express a form of EPHB4 that is unable to bind RASA1 yet retains protein tyrosine kinase activity (EPHB4 2YP) to study the role of EPHB4 and RASA1 in LV valve development in the embryo and LV valve maintenance in adults. We also used human dermal lymphatic endothelial cells in vitro to study the role of EPHB4 and RASA1 as regulators of LV valve specification induced by oscillatory shear stress, considered the trigger for LV valve specification in vivo.

RESULTS

LV valve specification, continued valve development postspecification, and LV valve maintenance were blocked upon induced loss of EPHB4 in LV. LV valve specification and maintenance were also impaired in EPHB4 2YP mice. Defects in LV valve development were reversed by inhibition of the Ras-MAPK (mitogen-activated protein kinase) signaling pathway. In human dermal lymphatic endothelial cells, loss of expression of EPHB4 or its ephrin b2 ligand, loss of expression of RASA1, and inhibition of physical interaction between EPHB4 and RASA1 resulted in dysregulated oscillatory shear stress-induced Ras-MAPK activation and impaired expression of LV specification markers that could be rescued by Ras-MAPK pathway inhibition. The same results were observed when human dermal lymphatic endothelial cells were stimulated with the Yoda1 agonist of the PIEZO1 oscillatory shear stress sensor. Although Yoda1 increased the number of LV valves when administered to wild-type embryos, it did not increase LV valve number when administered to EPHB4 2YP embryos.

CONCLUSIONS

EPHB4 is necessary for LV valve specification, continued valve development postspecification, and valve maintenance. LV valve specification requires physical interaction between EPHB4 and RASA1 to limit activation of the Ras-MAPK pathway in lymphatic endothelial cells. Specifically, EPHB4-RASA1 physical interaction is necessary to dampen Ras-MAPK activation induced through the PIEZO1 oscillatory shear stress sensor. These findings reveal the mechanism by which EPHB4 and RASA1 regulate the development of LV valves.

Master regulators of neurogenesis: the dynamic roles of Ephrin receptors across diverse cellular niches

The ephrin receptors (EphRs) are the largest family of receptor tyrosine kinases (RTKs) that are abundantly expressed in the developing brain and play important roles at different stages of neurogenesis ranging from neural stem cell (NSC) fate specification to neural migration, morphogenesis, and circuit assembly. Defects in EphR signalling have been associated with several pathologies including neurodevelopmental disorders (NDDs), intellectual disability (ID), and neurodegenerative diseases (NDs). Here, we review our current understanding of the complex and dynamic role of EphRs in the brain and discuss how deregulation of these receptors contributes to disease, highlighting their potential as valuable druggable targets.

Canonical ligand-dependent and non-canonical ligand-independent EphA2 signaling in the eye lens of wild-type, knockout, and aging mice

Disruption of Eph-ephrin bidirectional signaling leads to human congenital and age-related cataracts, but the mechanisms for these opacities in the eye lens remain unclear. Eph receptors bind to ephrin ligands on neighboring cells to induce canonical ligand-mediated signaling. The EphA2 receptor also signals non-canonically without ligand binding in cancerous cells, leading to epithelial-to-mesenchymal transition (EMT). We have previously shown that the receptor EphA2 and the ligand ephrin-A5 have diverse functions in maintaining lens transparency in mice. Loss of ephrin-A5 leads to anterior cataracts due to EMT. Surprisingly, both canonical and non-canonical EphA2 activation are present in normal wild-type lenses and in the ephrin-A5 knockout lenses. Canonical EphA2 signaling is localized exclusively to lens epithelial cells and does not change with age. Non-canonical EphA2 signaling is in both epithelial and fiber cells and increases significantly with age. We hypothesize that canonical ligand-dependent EphA2 signaling is required for the morphogenesis and organization of hexagonal equatorial epithelial cells while non-canonical ligand-independent EphA2 signaling is needed for complex membrane interdigitations that change during fiber cell differentiation and maturation. This is the first demonstration of non-canonical EphA2 activation in a non-cancerous tissue or cell and suggests a possible physiological function for ligand-independent EphA2 signaling.

Unveiling the therapeutic promise of EphA2 in glioblastoma: a comprehensive review

Glioblastoma (GBM), a primary brain tumor, exhibits remarkable invasiveness and is characterized by its intricate location, infiltrative behavior, the presence of both the blood-brain barrier (BBB) and the blood-brain tumor barrier (BBTB), phenotypic diversity, an immunosuppressive microenvironment with limited development yet rich vascularity, as well as the resistant nature of glioblastoma stem cells (GSCs) towards traditional chemotherapy and radiotherapy. These formidable factors present substantial obstacles in the quest for effective GBM treatments. Following extensive research spanning three decades, the hepatocellular receptor A2 (EphA2) receptor tyrosine kinase has emerged as a promising molecular target with translational potential in the realm of cancer therapy. Numerous compounds aimed at targeting EphA2 have undergone rigorous evaluation and clinical investigation. This article provides a comprehensive account of the distinctive roles played by canonical and non-canonical EphA2 signaling in various contexts, while also exploring the involvement of the EphA2-ephrin A1 signaling axis in GBM pathogenesis. Additionally, the review offers an overview of completed clinical trials targeting EphA2 for GBM treatment, shedding light on both the prospects and challenges associated with EphA2-directed interventions in the domain of cancer therapeutics.

The Role of Biomarkers in the Early Diagnosis of Gastric Cancer: A Study on CCR5, CCL5, PDGF, and EphA7

Despite the use of screening programs, gastric cancer (GC) diagnosis may only be possible at an advanced stage. In this study, we examined the serum levels of C-C chemokine receptor type 5 (CCR5), C-C motif chemokine ligand 5 (CCL5), platelet-derived growth factor (PDGF), and EphrinA7 (EphA7) in patients with gastric carcinoma and healthy controls to investigate the significance and usability of these potential biomarkers in the early diagnosis of GC. The study enrolled 69 GC patients and 40 healthy individuals. CCR5, CCL5, PDGF-BB, and EphA7 levels, which have been identified in the carcinogenesis of many cancers, were measured in the blood samples using the ELISA method. CCR5, CCL5, PDGF-BB, and EphA7 were all correlated with GC diagnosis (CCR5, p < 0.001, r = -0.449; CCL5, p = 0.014, r = -0.234; PDGF-BB, p < 0.001, r = -0.700; EPHA7, p < 0.001, r = -0.617). The serum CCR5, EphA7, and especially the PDGF-BB levels of the patients diagnosed with GC were discovered to be significantly higher compared to the healthy controls. PDGF-BB had the highest positive and negative predictive values when evaluated in ROC analysis to determine its diagnostic significance (cut-off value: 59.8 ng/L; AUC: 0.92 (0.87-0.97)). As far as we know, this is the first study to investigate the potential connection between GC and these four biomarkers. The fact that serum CCR5, CCL5, EphA7, and especially PDGF-BB levels in the patient group were significantly higher compared to healthy controls indicates that they can be used with high accuracy in the early diagnosis of GC. In addition, the levels of CCR5, PDGF-BB, and EphA7 can be used as important indicators to predict the biological behavior and prognosis of GC.

Targeting the EphA2 pathway: could it be the way for bone sarcomas?

Bone sarcomas are malignant tumors of mesenchymal origin. Complete surgical resection is the cornerstone of multidisciplinary treatment. However, advanced, unresectable forms remain incurable. A crucial step towards addressing this challenge involves comprehending the molecular mechanisms underpinning tumor progression and metastasis, laying the groundwork for innovative precision medicine-based interventions. We previously showed that tyrosine kinase receptor Ephrin Type-A Receptor 2 (EphA2) is overexpressed in bone sarcomas. EphA2 is a key oncofetal protein implicated in metastasis, self-renewal, and chemoresistance. Molecular, genetic, biochemical, and pharmacological approaches have been developed to target EphA2 and its signaling pathway aiming to interfere with its tumor-promoting effects or as a carrier for drug delivery. This review synthesizes the main functions of EphA2 and their relevance in bone sarcomas, providing strategies devised to leverage this receptor for diagnostic and therapeutic purposes, with a focus on its applicability in the three most common bone sarcoma histotypes: osteosarcoma, chondrosarcoma, and Ewing sarcoma.

Neuroscience of cancer: Research progress and emerging of the field

Cancer cells immediately expand and penetrate adjoining tissues, as opposed to metastasis, that is the spread of cancer cells through the circulatory or lymphatic systems to more distant places via the invasion process. We found that a lack of studies discussed tumor development with the nervous system, by the aspects of cancer-tissue invasion (biological) and chemical modulation of growth that cascades by releasing neural-related factors from the nerve endings via chemical substances known as neurotransmitters. In this review, we aimed to carefully demonstrate and describe the cancer invasion and interaction with the nervous system, as well as reveal the research progress and the emerging neuroscience of cancer. An initial set of 160 references underwent systematic review and summarization. Through a meticulous screening process, these data were refined, ultimately leading to the inclusion of 98 studies that adhered to predetermined criteria. The outcomes show that one formidable challenge in the realm of cancer lies in its intrinsic heterogeneity and remarkable capacity for rapid adaptation. Despite advancements in genomics and precision medicine, there is still a need to identify new molecular targets. Considering cancer within its molecular and cellular environment, including neural components, is crucial for addressing this challenge. In conclusion, this review provides good referential data for direct, indirect, biological, and chemical interaction for nerve tissue-tumor interaction, suggesting the establishment of new therapy techniques and mechanisms by controlling and modifying neuron networks that supply signals to tumors.

The pro-tumoral and anti-tumoral roles of EphA4 on T regulatory cells and tumor associated macrophages during HNSCC tumor progression

Head and Neck Squamous Cell Carcinoma (HNSCC) is a deadly cancer with poor response to targeted therapy, largely driven by an immunosuppressive tumor microenvironment (TME). Here we examine the immune-modulatory role of the receptor tyrosine kinase EphA4 in HNSCC progression. Within the TME, EphA4 is primarily expressed on regulatory T cells (Tregs) and macrophages. In contrast ephrinB2, an activating ligand of EphA4, is expressed in tumor blood vessels. Using genetically engineered mouse models, we show that EphA4 expressed in Tregs promotes tumor growth, whereas EphA4 expressed in monocytes inhibits tumor growth. In contrast, ephrinB2 knockout in blood vessels reduces both intratumoral Tregs and macrophages. A novel specific EphA4 inhibitor, APY-d3-PEG4, reverses the accelerated tumor growth we had previously reported with EphB4 cancer cell knockout. EphA4 knockout in macrophages not only enhanced their differentiation into M2 macrophage but also increased Treg suppressive activity. APY-d3-PEG4 reversed the accelerated growth seen in the EphA4 knockout of monocytes but conferred no additional benefit when EphA4 was knocked out on Tregs. Underscoring an EphA4-mediated interplay between Tregs and macrophages, we found that knockout of EphA4 in Tregs not only decreases their activation but also reduces tumor infiltration of pro-tumoral M2 macrophages. These data identify Tregs as a primary target of APY-d3-PEG4 and suggest a role for Tregs in regulating macrophage conversion. These data also support the possible anti-cancer therapeutic value of bispecific peptides or antibodies capable of promoting EphA4 blockade in Tregs but not macrophages.

Significance

EphA4 in regulatory T cells has a pro-tumoral effect while EphA4 in macrophages plays an anti-tumoral role underscoring the necessity of developing biologically rational therapeutics.

EphB2 Receptor Promotes Dermal Fibrosis in Systemic Sclerosis

OBJECTIVE

Erythropoietin-producing hepatocellular (Eph)/Ephrin cell-cell signaling is emerging as a key player in tissue fibrogenesis. The aim of this study was to test the hypothesis that the receptor tyrosine kinase EphB2 mediates dermal fibrosis in systemic sclerosis (SSc).

METHODS

We assessed normal and SSc human skin biopsies for EphB2 expression. The in vivo role of EphB2 in skin fibrosis was investigated by subjecting EphB2-knockout mice to both bleomycin-induced and tight skin (Tsk1/+) genetic mouse models of skin fibrosis. EphB2 kinase-dead and overactive point mutant mice were used to evaluate the role of EphB2 forward signaling in bleomycin-induced dermal fibrosis. In vitro studies were performed on dermal fibroblasts from patients with SSc and healthy controls, which was followed by in vivo analysis of fibroblast-specific Ephb2-deficient mice.

RESULTS

Expression of EphB2 is up-regulated in SSc skin tissue and explanted SSc dermal fibroblasts compared with healthy controls. EphB2 expression is elevated in two animal models of dermal fibrosis. In mice, EphB2 drives dermal fibrosis in both the bleomycin and the Tsk1/+ models of skin fibrosis. EphB2 forward signaling is a critical mediator of dermal fibrosis. Transforming growth factor-β (TGF-β) cytokines up-regulate EphB2 in dermal fibroblasts via noncanonical TGF-β/mother against decapentaplegic signaling, and silencing EPHB2 in human dermal fibroblasts is sufficient to dampen TGF-β-induced fibroblast-to-myofibroblast differentiation. Moreover, mice with fibroblast-specific deletion of EphB2 showed impaired fibroblast-to-myofibroblast differentiation and reduced skin fibrosis upon bleomycin challenge.

CONCLUSION

Our data implicate TGF-β regulation of EphB2 overexpression and kinase-mediated forward signaling in the development of dermal fibrosis in SSc. EphB2 thus represents a potential new therapeutic target for SSc.

Transmembrane helix interactions regulate oligomerization of the receptor tyrosine kinase EphA2

The transmembrane helices of receptor tyrosine kinases (RTKs) have been proposed to switch between two different dimeric conformations, one associated with the inactive RTK and the other with the active RTK. Furthermore, recent work has demonstrated that some full-length RTKs are associated into oligomers that are larger than dimers, raising questions about the roles of the TM helices in the assembly and function of these oligomers. Here we probe the roles of the TM helices in the assembly of EphA2 RTK oligomers in the plasma membrane. We employ mutagenesis to evaluate the relevance of a published NMR dimeric structure of the isolated EphA2 TM helix in the context of the full-length EphA2 in the plasma membrane. We use two fluorescence methods, Förster Resonance Energy Transfer and Fluorescence Intensity Fluctuations spectrometry, which yield complementary information about the EphA2 oligomerization process. These studies reveal that the TM helix mutations affect the stability, structure, and size of EphA2 oligomers. However, the effects are multifaceted and point to a more complex role of the TM helix than the one expected from the "TM dimer switch" model.

Enhanced EphB2-Specific Peptide Inhibitors through Stabilization of Polyproline II Helical Structure

Ephrin (Eph) receptors are the largest family of receptor tyrosine kinases. Interactions between Eph receptors and their membrane-bound ephrin protein ligands are associated with many developmental processes as well as various cancers and neurodegenerative diseases. With significant crosstalk between different Eph receptors and ephrin ligands, there is an urgent need for high-affinity ligands that bind specifically to individual Eph receptors to interrogate and modulate their functions. Here, we describe the rational development of potent EphB2 receptor inhibitors derived from the EphB2 receptor-specific SNEW peptide. To improve inhibitory potency, we evaluated 20+ cross-linkers with the goal of spanning and stabilizing a single polyproline II helical turn observed when SNEW binds to the EphB2 receptor. Of the cross-linkers evaluated, an 11-atom cross-linker, composed of a rigid 2,7-dimethylnaphthyl moiety between two cysteine residues, was found to yield the most potent inhibitor. Analysis of the cyclized region of this peptide by NMR and molecular dynamics simulations suggests that cross-linking stabilizes the receptor-bound polyproline II helix structure observed in the receptor-peptide complex. Cross-linked SNEW variants retained binding specificity for EphB2 and showed cross-linker-dependent resistance to trypsin proteolysis. Beyond the discovery of more potent EphB2 receptor inhibitors, these studies illustrate a novel cyclization approach with potential to stabilize polyproline II helical structure in various peptides for specific targeting of the myriad protein-protein interactions (PPIs) mediated by polyproline II helices.

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.

The impact of chronic pain on brain gene expression

Background

Chronic pain affects one fifth of American adults, contributing significant public health burden. Chronic pain mechanisms can be further understood through investigating brain gene expression.

Methods

We tested differentially expressed genes (DEGs) in chronic pain, migraine, lifetime fentanyl and oxymorphone use, and with chronic pain genetic risk in four brain regions (dACC, DLPFC, MeA, BLA) and imputed cell type expression data from 304 postmortem donors. We compared findings across traits and with independent transcriptomics resources, and performed gene-set enrichment.

Results

We identified two chronic pain DEGs: B4GALT and VEGFB in bulk dACC. We found over 2000 (primarily BLA microglia) chronic pain cell type DEGs. Findings were enriched for mouse microglia pain genes, and for hypoxia and immune response. Cross-trait DEG overlap was minimal.

Conclusions

Chronic pain-associated gene expression is heterogeneous across cell type, largely distinct from that in pain-related traits, and shows BLA microglia are a key cell type.

The landscape of rare genetic variation associated with inflammatory bowel disease and Parkinson's disease comorbidity

BACKGROUND

Inflammatory bowel disease (IBD) and Parkinson's disease (PD) are chronic disorders that have been suggested to share common pathophysiological processes. LRRK2 has been implicated as playing a role in both diseases. Exploring the genetic basis of the IBD-PD comorbidity through studying high-impact rare genetic variants can facilitate the identification of the novel shared genetic factors underlying this comorbidity.

METHODS

We analyzed whole exomes from the BioMe BioBank and UK Biobank, and whole genomes from a cohort of 67 European patients diagnosed with both IBD and PD to examine the effects of LRRK2 missense variants on IBD, PD and their co-occurrence (IBD-PD). We performed optimized sequence kernel association test (SKAT-O) and network-based heterogeneity clustering (NHC) analyses using high-impact rare variants in the IBD-PD cohort to identify novel candidate genes, which we further prioritized by biological relatedness approaches. We conducted phenome-wide association studies (PheWAS) employing BioMe BioBank and UK Biobank whole exomes to estimate the genetic relevance of the 14 prioritized genes to IBD-PD.

RESULTS

The analysis of LRRK2 missense variants revealed significant associations of the G2019S and N2081D variants with IBD-PD in addition to several other variants as potential contributors to increased or decreased IBD-PD risk. SKAT-O identified two significant genes, LRRK2 and IL10RA, and NHC identified 6 significant gene clusters that are biologically relevant to IBD-PD. We observed prominent overlaps between the enriched pathways in the known IBD, PD, and candidate IBD-PD gene sets. Additionally, we detected significantly enriched pathways unique to the IBD-PD, including MAPK signaling, LPS/IL-1 mediated inhibition of RXR function, and NAD signaling. Fourteen final candidate IBD-PD genes were prioritized by biological relatedness methods. The biological importance scores estimated by protein-protein interaction networks and pathway and ontology enrichment analyses indicated the involvement of genes related to immunity, inflammation, and autophagy in IBD-PD. Additionally, PheWAS provided support for the associations of candidate genes with IBD and PD.

CONCLUSIONS

Our study confirms and uncovers new LRRK2 associations in IBD-PD. The identification of novel inflammation and autophagy-related genes supports and expands previous findings related to IBD-PD pathogenesis, and underscores the significance of therapeutic interventions for reducing systemic inflammation.

Engineering of an EPHA2-Targeted Monobody for the Detection of Colorectal Cancer

BACKGROUND/AIM

Colorectal cancer (CRC) is the third most common cancer worldwide, and is second only to lung cancer with respect to cancer-related deaths. Noninvasive molecular imaging using established markers is a new emerging method to diagnose CRC. The human ephrin receptor family type-A 2 (hEPHA2) oncoprotein is overexpressed at the early, but not late, stages of CRC. Previously, we reported development of an E1 monobody that is specific for hEPHA2-expressing cancer cells both in vitro and in vivo. Herein, we investigated the ability of the E1 monobody to detect hEPHA2 expressing colorectal tumors in a mouse model, as well as in CRC tissue.

MATERIALS AND METHODS

The expression of hEPHA2 on the surface of CRC cells was analyzed by western blotting and flow cytometry. The targeting efficacy of the E1 monobody for CRC cells was examined by flow cytometry, and immunofluorescence staining. E1 conjugated to the Renilla luciferase variant 8 (Rluc8) reporter protein was used for in vivo imaging in mice. Additionally, an enhanced green fluorescence protein (EGFP) conjugated E1 monobody was used to check the ability of the E1 monobody to target CRC tissue.

RESULTS

The E1 monobody bound efficiently to hEPHA2-expressing CRC cell lines, and E1 conjugated to the Rluc8 reporter protein targeted tumor tissues in mice transplanted with HCT116 CRC tumor cells. Finally, E1-EGFP stained tumor tissues from human CRC patients, showing a pattern similar to that of an anti-hEPHA2 antibody.

CONCLUSION

The E1 monobody has utility as an EPHA2 targeting agent for the detection of CRC.

PHF6-mediated transcriptional control of NSC via Ephrin receptors is impaired in the intellectual disability syndrome BFLS

The plant homeodomain zinc-finger protein, PHF6, is a transcriptional regulator, and PHF6 germline mutations cause the X-linked intellectual disability (XLID) Börjeson-Forssman-Lehmann syndrome (BFLS). The mechanisms by which PHF6 regulates transcription and how its mutations cause BFLS remain poorly characterized. Here, we show genome-wide binding of PHF6 in the developing cortex in the vicinity of genes involved in central nervous system development and neurogenesis. Characterization of BFLS mice harbouring PHF6 patient mutations reveals an increase in embryonic neural stem cell (eNSC) self-renewal and a reduction of neural progenitors. We identify a panel of Ephrin receptors (EphRs) as direct transcriptional targets of PHF6. Mechanistically, we show that PHF6 regulation of EphR is impaired in BFLS mice and in conditional Phf6 knock-out mice. Knockdown of EphR-A phenocopies the PHF6 loss-of-function defects in altering eNSCs, and its forced expression rescues defects of BFLS mice-derived eNSCs. Our data indicate that PHF6 directly promotes Ephrin receptor expression to control eNSC behaviour in the developing brain, and that this pathway is impaired in BFLS.

Exploring the potential of EphA2 receptor signaling pathway: a comprehensive review in cancer treatment

The protein encoded by the ephrin type-A receptor 2 (EphA2) gene is a member of the ephrin receptor subfamily of the receptor tyrosine kinase family (RTKs). Eph receptors play a significant role in various biological processes, particularly cancer progression, development, and pathogenesis. They have been observed to regulate cancer cell growth, migration, invasion, tumor development, invasiveness, angiogenesis, and metastasis. To target EphA2 activity, various molecular, genetic, biochemical, and pharmacological strategies have been extensively tested in laboratory cultures and animal models. Notably, drugs, such as dasatinib, initially designed to target the kinase family, have demonstrated an additional capability to target EphA2 activity. Additionally, a novel monoclonal antibody named EA5 has emerged as a promising option to counteract the effects of EphA2 overexpression and restore tamoxifen sensitivity in EphA2-transfected MCF-7 cells during in vitro experiments. This antibody mimicked the binding of Ephrin A to EphA2. These methods offer potential avenues for inhibiting EphA2 activity, which could significantly decelerate breast cancer progression and restore sensitivity to certain drugs. This review article comprehensively covers EphA2's involvement in multiple malignancies, including ovarian, colorectal, breast, lung, glioma, and melanoma. Furthermore, we discuss the structure of EphA2, the Eph-Ephrin signaling pathway, various EphA2 inhibitors, and the mechanisms of EphA2 degradation. This article provides an extensive overview of EphA2's vital role in different types of cancers and outlines potential therapeutic approaches to target EphA2, shedding light on the underlying molecular mechanisms that make it an attractive target for cancer treatment.

Optogenetic Regulation of EphA1 RTK Activation and Signaling

Eph receptors are ubiquitous class of transmembrane receptors that mediate cell-cell communication, proliferation, differentiation, and migration. EphA1 receptors specifically play an important role in angiogenesis, fetal development, and cancer progression; however, studies of this receptor can be challenging as its ligand, ephrinA1, binds and activates several EphA receptors simultaneously. Optogenetic strategies could be applied to circumvent this requirement for ligand activation and enable selective activation of the EphA1 subtype. In this work, we designed and tested several iterations of an optogenetic EphA1 - Cryptochrome 2 (Cry2) fusion, investigating their capacity to mimic EphA1-dependent signaling in response to light activation. We then characterized the key cell signaling target of MAPK phosphorylation activated in response to light stimulation. The optogenetic regulation of Eph receptor RTK signaling without the need for external stimulus promises to be an effective means of controlling individual Eph receptor-mediated activities and creates a path forward for the identification of new Eph-dependent functions.

EFNB1 levels determine distinct drug response patterns guiding precision therapy for B-cell neoplasms

The multi-omics data has greatly improved the molecular diagnosis of B-cell neoplasms, but there is still a lack of predictive biomarkers to guide precision therapy. Here, we analyzed publicly available data and found that B-cell neoplasm cell lines with different levels of EFNB1 had distinctive drug response patterns of inhibitors targeting SRC/PI3K/AKT. Overexpression of EFNB1 promoted phosphorylation of key proteins in drug response, such as SRC and STMN1, conferring sensitivity to SRC inhibitor and cytotoxic drugs. EFNB1 phosphorylation signaling network was significantly associated with the prognosis of GCB-DLBCL patients. Moreover, EFNB1 levels were correlated with cell of origin (COO) scores, suggesting that EFNB1 is a quantitative indicator of cell differentiation. Ultimately, we proposed a model for the stratification of human B-cell malignancies and the implementation of targeted therapies based on EFNB1 levels. Our findings highlight that EFNB1 level is a promising biomarker for predicting drug response, COO and prognosis.

The combination of tetracyclines effectively ameliorates liver fibrosis via inhibition of EphB1/2

Eph receptor tyrosine kinase EphB1/2 contributes to the development of liver fibrosis, suggesting the rationale that EphB1/2 inhibitors may be effective in liver fibrosis therapy. Since tetracycline antibiotics were recently demonstrated as EphB kinase inhibitors, in present study we investigated their therapeutic potential against liver fibrosis. Our results showed that the tetracycline combination of demeclocycline (D), chlortetracycline (C), and minocycline (M) inhibited the activation of hepatic stellate cells (HSCs) in vitro and alleviated CCl4-induced animal model of liver fibrosis in vivo. Mechanistically, DCM combination inhibited EphB1/2 phosphorylation and subsequent activation of the MAPK signaling. Moreover, we found that short-term and low-dose DCM combination treatment decreased tissue inflammation and improved liver fibrosis in mice. Thus, our study indicates that tetracyclines may be repurposed for the treatment of liver fibrosis.

Eph receptors and ephrins in cancer progression

Evidence implicating Eph receptor tyrosine kinases and their ephrin ligands (that together make up the 'Eph system') in cancer development and progression has been accumulating since the discovery of the first Eph receptor approximately 35 years ago. Advances in the past decade and a half have considerably increased the understanding of Eph receptor-ephrin signalling mechanisms in cancer and have uncovered intriguing new roles in cancer progression and drug resistance. This Review focuses mainly on these more recent developments. I provide an update on the different mechanisms of Eph receptor-ephrin-mediated cell-cell communication and cell autonomous signalling, as well as on the interplay of the Eph system with other signalling systems. I further discuss recent advances in elucidating how the Eph system controls tumour expansion, invasiveness and metastasis, supports cancer stem cells, and drives therapy resistance. In addition to functioning within cancer cells, the Eph system also mediates the reciprocal communication between cancer cells and cells of the tumour microenvironment. The involvement of the Eph system in tumour angiogenesis is well established, but recent findings also demonstrate roles in immune cells, cancer-associated fibroblasts and the extracellular matrix. Lastly, I discuss strategies under evaluation for therapeutic targeting of Eph receptors-ephrins in cancer and conclude with an outlook on promising future research directions.

Biological Significance of EphB4 Expression in Cancer

Eph receptors and their Eph receptor-interacting (ephrin) ligands comprise a vital cell communication system with several functions. In cancer cells, there was evidence of bilateral Eph receptor signaling with both tumor-suppressing and tumor-promoting actions. As a member of the Eph receptor family, EphB4 has been linked to tumor angiogenesis, growth, and metastasis, which makes it a viable and desirable target for drug development in therapeutic applications. Many investigations have been conducted over the last decade to elucidate the structure and function of EphB4 in association with its ligand ephrinB2 for its involvement in tumorigenesis. Although several EphB4-targeting drugs have been investigated, and some selective inhibitors have been evaluated in clinical trials. This article addresses the structure and function of the EphB4 receptor, analyses its possibility as an anticancer therapeutic target, and summarises knowledge of EphB4 kinase inhibitors. To summarise, EphB4 is a difficult but potential treatment option for cancers.

Targeting EPHA2 with Kinase Inhibitors in Colorectal Cancer

The ephrin type-A 2 receptor tyrosine kinase (EPHA2) is involved in the development and progression of various cancer types, including colorectal cancer (CRC). There is also evidence that EPHA2 plays a key role in the development of resistance to the endothelial growth factor receptor (EGFR) monoclonal antibody Cetuximab used clinically in CRC. Despite the promising pharmacological potential of EPHA2, only a handful of specific inhibitors are currently available. In this concept paper, general strategies for EPHA2 inhibition with molecules of low molecular weight (small molecules) are described. Furthermore, available examples of inhibiting EPHA2 in CRC using small molecules are summarized, highlighting the potential of this approach.

An EPHB4-RASA1 signaling complex inhibits shear stress-induced Ras-MAPK activation in lymphatic endothelial cells to promote the development of lymphatic vessel valves

EPHB4 is a receptor protein tyrosine kinase that is required for the development of lymphatic vessel (LV) valves. We show here that EPHB4 is necessary for the specification of LV valves, their continued development after specification, and the maintenance of LV valves in adult mice. EPHB4 promotes LV valve development by inhibiting the activation of the Ras-MAPK pathway in LV endothelial cells (LEC). For LV specification, this role for EPHB4 depends on its ability to interact physically with the p120 Ras-GTPase-activating protein (RASA1) that acts as a negative regulator of Ras. Through physical interaction, EPHB4 and RASA1 dampen oscillatory shear stress (OSS)-induced Ras-MAPK activation in LEC, which is required for LV specification. We identify the Piezo1 OSS sensor as a focus of EPHB4-RASA1 regulation of OSS-induced Ras-MAPK signaling mediated through physical interaction. These findings contribute to an understanding of the mechanism by which EPHB4, RASA1 and Ras regulate lymphatic valvulogenesis.

Molecular Determinants of EphA2 and EphB2 Antagonism Enable the Design of Ligands with Improved Selectivity

With the aim of identifying novel antagonists selective for the EphA receptor family, a combined experimental and computational approach was taken to investigate the molecular basis of the recognition between a prototypical Eph-ephrin antagonist (UniPR1447) and two representative receptors of the EphA and EphB subfamilies, namely, EphA2 and EphB2 receptors. The conformational free-energy surface (FES) of the binding state of UniPR1447 within the ligand binding domain of EphA2 and EphB2, reconstructed from molecular dynamics (MD) simulations performed on the microsecond time scale, was exploited to drive the design and synthesis of a novel antagonist selective for EphA2 over the EphB2 receptor. The availability of compounds with this pharmacological profile will help discriminate the importance of these two receptors in the insurgence and progression of cancer.

Utility of FRET in studies of membrane protein oligomerization: The concept of the effective dissociation constant

The activity of many membrane receptors is controlled through their lateral association into dimers or higher-order oligomers. Although Förster resonance energy transfer (FRET) measurements have been used extensively to characterize the stability of receptor dimers, the utility of FRET in studies of larger oligomers has been limited. Here we introduce an effective equilibrium dissociation constant that can be extracted from FRET measurements for EphA2, a receptor tyrosine kinase (RTK) known to form active oligomers of heterogeneous distributions in response to its ligand ephrinA1-Fc. The newly introduced effective equilibrium dissociation constant has a well-defined physical meaning and biological significance. It denotes the receptor concentration for which half of the receptors are monomeric and inactive, and the other half are associated into oligomers and are active, irrespective of the exact oligomer size. This work introduces a new dimension to the utility of FRET in studies of membrane receptor association and signaling in the plasma membrane.

Unraveling the Potential of EphA4: A Breakthrough Target and Beacon of Hope for Neurological Diseases

Erythropoietin-producing hepatocellular carcinoma A4 (EphA4) is a transmembrane receptor protein which is a part of the most prominent family of receptor tyrosine kinases (RTKs). It serves a crucial role in both physiological, biological, and functional states binding with their ligand like Ephrins. Its abundance in the majority of the body's systems has been reported. Moreover, it draws much attention in the CNS since it influences axonal and vascular guidance. Also, it has a widespread role at the pathological state of various CNS disorders. Reports suggest it obstructs axonal regeneration in various neurodegenerative diseases and neurological disorders. Although, neuro-regeneration is still an open challenge to the modern drug discovery community.  Hence, in this review, we will provide information about the role of EphA4 in neurological diseases by which it may emerge as a therapeutic target for CNS disease. We will also provide a glance at numerous signaling pathways that activate or inhibit the EphA4-associated biological processes contributing to the course of neurodegenerative diseases. Thus, this work might serve as a basis for futuristic studies that are related to the target-based drug discovery in the field of neuro-regeneration. Pathological and physiological events associated with EphA4 and Ephrin upregulation and interaction.

Temporospatial inhibition of Erk signaling is required for lymphatic valve formation

Intraluminal lymphatic valves (LVs) and lymphovenous valves (LVVs) are critical to ensure the unidirectional flow of lymphatic fluid. Morphological abnormalities in these valves always cause lymph or blood reflux, and result in lymphedema. However, the underlying molecular mechanism of valve development remains poorly understood. We here report the implication of Efnb2-Ephb4-Rasa1 regulated Erk signaling axis in lymphatic valve development with identification of two new valve structures. Dynamic monitoring of phospho-Erk activity indicated that Erk signaling is spatiotemporally inhibited in some lymphatic endothelial cells (LECs) during the valve cell specification. Inhibition of Erk signaling via simultaneous depletion of zygotic erk1 and erk2 or treatment with MEK inhibitor selumetinib causes lymphatic vessel hypoplasia and lymphatic valve hyperplasia, suggesting opposite roles of Erk signaling during these two processes. ephb4b mutants, efnb2a;efnb2b or rasa1a;rasa1b double mutants all have defective LVs and LVVs and exhibit blood reflux into lymphatic vessels with an edema phenotype. Importantly, the valve defects in ephb4b or rasa1a;rasa1b mutants are mitigated with high-level gata2 expression in the presence of MEK inhibitors. Therefore, Efnb2-Ephb4 signaling acts to suppress Erk activation in valve-forming cells to promote valve specification upstream of Rasa1. Not only do our findings reveal a molecular mechanism of lymphatic valve formation, but also provide a basis for the treatment of lymphatic disorders.

Ephrin-A4 Ligand (EFNA4) Predicts Poor Prognosis of Hepatocellular Carcinoma and Promotes Tumor Proliferation

Background/Aims

Primary hepatocellular carcinoma (HCC) is one of the most lethal tumor diseases in the world. Receptor tyrosine kinases (RTKs) are thought to play a vital role in HCC and Ephrin-A4 ligand (EFNA4) is a membrane-bound molecule that can activate RTKs through erythropoietin-producing hepatocellular (Eph) receptors. However, the specific role of EFNA4 remains unknown. The aim of our study was to explore the prognostic value of EFNA4 expression in HCC.

Methods

Bioinformatics analyses were conducted to probe the expression levels and prognostic value of EFNA4 in HCC. The quantitative real-time polymerase chain reaction, immunohistochemical and western blot were used to confirm the expression of EFNA4 in paired clinical specimens of HCC. Colony formation assay was used to confirm the proliferation of tumor cell.

Results

The expression of EFNA4 is generally elevated in various cancers. Especially, EFNA4 was upregulated in tumor tissue and associated with clinical stage in HCC patients. HCC patients with lower levels of EFNA4 possessed better survival and progression-free survival times. Colony formation assay indicated that the overexpression of EFNA4 promoted tumor cell proliferation.

Conclusion

These results demonstrated that EFNA4 played as an oncogenic gene and a prognostic biomarker for HCC patients.

Integration of cancer-related genetic landscape of Eph receptors and ephrins with proteomics identifies a crosstalk between EPHB6 and EGFR

Eph receptors and their ephrin ligands are viewed as promising targets for cancer treatment; however, targeting them is hindered by their context-dependent functionalities. To circumvent this, we explore molecular landscapes underlying their pro- and anti-malignant activities. Using unbiased bioinformatics approaches, we construct a cancer-related network of genetic interactions (GIs) of all Ephs and ephrins to assist in their therapeutic manipulation. We also apply genetic screening and BioID proteomics and integrate them with machine learning approaches to select the most relevant GIs of one Eph receptor, EPHB6. This identifies a crosstalk between EPHB6 and EGFR, and further experiments confirm the ability of EPHB6 to modulate EGFR signaling, enhancing the proliferation of cancer cells and tumor development. Taken together, our observations show EPHB6 involvement in EGFR action, suggesting its targeting might be beneficial in EGFR-dependent tumors, and confirm that the Eph family genetic interactome presented here can be effectively exploited in developing cancer treatment approaches.

Unraveling the Significance of EPH/Ephrin Signaling in Liver Cancer: Insights into Tumor Progression and Therapeutic Implications

Liver cancer is a complex and challenging disease with limited treatment options and dismal prognosis. Understanding the underlying molecular mechanisms driving liver cancer progression and metastasis is crucial for developing effective therapeutic strategies. The EPH/ephrin system, which comprises a family of cell surface receptors and their corresponding ligands, has been implicated in the pathogenesis of HCC. This review paper aims to provide an overview of the current understanding of the role of the EPH/ephrin system in HCC. Specifically, we discuss the dysregulation of EPH/ephrin signaling in HCC and its impact on various cellular processes, including cell proliferation, migration, and invasion. Overall, the EPH/ephrin signaling system emerges as a compelling and multifaceted player in liver cancer biology. Elucidating its precise mechanisms and understanding its implications in disease progression and therapeutic responses may pave the way for novel targeted therapies and personalized treatment approaches for liver cancer patients. Further research is warranted to unravel the full potential of the EPH/ephrin system in liver cancer and its clinical translation.

Therapeutic administration of mouse mast cell protease 6 improves functional recovery after traumatic spinal cord injury in mice by promoting remyelination and reducing glial scar formation

Traumatic spinal cord injury (SCI) most often leads to permanent paralysis due to the inability of axons to regenerate in the adult mammalian central nervous system (CNS). In the past, we have shown that mast cells (MCs) improve the functional outcome after SCI by suppressing scar tissue formation at the lesion site via mouse mast cell protease 6 (mMCP6). In this study, we investigated whether recombinant mMCP6 can be used therapeutically to improve the functional outcome after SCI. Therefore, we applied mMCP6 locally via an intrathecal catheter in the subacute phase after a spinal cord hemisection injury in mice. Our findings showed that hind limb motor function was significantly improved in mice that received recombinant mMCP6 compared with the vehicle-treated group. In contrast to our previous findings in mMCP6 knockout mice, the lesion size and expression levels of the scar components fibronectin, laminin, and axon-growth-inhibitory chondroitin sulfate proteoglycans were not affected by the treatment with recombinant mMCP6. Surprisingly, no difference in infiltration of CD4+ T cells and reactivity of Iba-1+ microglia/macrophages at the lesion site was observed between the mMCP6-treated mice and control mice. Additionally, local protein levels of the pro- and anti-inflammatory mediators IL-1β, IL-2, IL-4, IL-6, IL-10, TNF-α, IFNγ, and MCP-1 were comparable between the two treatment groups, indicating that locally applied mMCP6 did not affect inflammatory processes after injury. However, the increase in locomotor performance in mMCP6-treated mice was accompanied by reduced demyelination and astrogliosis in the perilesional area after SCI. Consistently, we found that TNF-α/IL-1β-astrocyte activation was decreased and that oligodendrocyte precursor cell (OPC) differentiation was increased after recombinant mMCP6 treatment in vitro. Mechanistically, this suggests effects of mMCP6 on reducing astrogliosis and improving (re)myelination in the spinal cord after injury. In conclusion, these data show for the first time that recombinant mMCP6 is therapeutically active in enhancing recovery after SCI.

EphB4 monomer inhibits chronic graft vasculopathy in an aortic transplant model

T cells and macrophages play an important role in the formation of allograft vasculopathy, which is the predominant form of chronic rejection in cardiac transplants. Arteries express Ephrin-B2 as a marker of arterial identity, whereas circulating monocytes express the cognate receptor EphB4, which facilitates monocyte adhesion to the endothelial surface. Adherent monocytes transmigrate and differentiate into macrophages that activate T cells and are a main source of tissue damage during rejection. We hypothesized that inhibition of Ephrin-B2-EphB4 binding would decrease immune cell accumulation within a transplanted graft and prevent allograft vasculopathy. We used EphB4 monomer to inhibit Ephrin-B2-EphB4 binding in a rat infrarenal aortic transplant model. Rats treated with EphB4 monomer had fewer macrophages and T cells in the aortic allografts at 28 days, as well as significantly less neointima formation. These data show that the Ephin-B2-EphB4 axis may be an important target for prevention or treatment of allograft vasculopathy.

Structural and non-structural proteins in SARS-CoV-2: potential aspects to COVID-19 treatment or prevention of progression of related diseases

Coronavirus disease 2019 (COVID-19) is caused by a new member of the Coronaviridae family known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). There are structural and non-structural proteins (NSPs) in the genome of this virus. S, M, H, and E proteins are structural proteins, and NSPs include accessory and replicase proteins. The structural and NSP components of SARS-CoV-2 play an important role in its infectivity, and some of them may be important in the pathogenesis of chronic diseases, including cancer, coagulation disorders, neurodegenerative disorders, and cardiovascular diseases. The SARS-CoV-2 proteins interact with targets such as angiotensin-converting enzyme 2 (ACE2) receptor. In addition, SARS-CoV-2 can stimulate pathological intracellular signaling pathways by triggering transcription factor hypoxia-inducible factor-1 (HIF-1), neuropilin-1 (NRP-1), CD147, and Eph receptors, which play important roles in the progression of neurodegenerative diseases like Alzheimer's disease, epilepsy, and multiple sclerosis, and multiple cancers such as glioblastoma, lung malignancies, and leukemias. Several compounds such as polyphenols, doxazosin, baricitinib, and ruxolitinib could inhibit these interactions. It has been demonstrated that the SARS-CoV-2 spike protein has a stronger affinity for human ACE2 than the spike protein of SARS-CoV, leading the current study to hypothesize that the newly produced variant Omicron receptor-binding domain (RBD) binds to human ACE2 more strongly than the primary strain. SARS and Middle East respiratory syndrome (MERS) viruses against structural and NSPs have become resistant to previous vaccines. Therefore, the review of recent studies and the performance of current vaccines and their effects on COVID-19 and related diseases has become a vital need to deal with the current conditions. This review examines the potential role of these SARS-CoV-2 proteins in the initiation of chronic diseases, and it is anticipated that these proteins could serve as components of an effective vaccine or treatment for COVID-19 and related diseases. Video Abstract.

Optimization of the Lead Compound NVP-BHG712 as a Colorectal Cancer Inhibitor

The ephrin type-A receptor 2 (EPHA2) kinase belongs to the largest family of receptor tyrosine kinases. There are several indications of an involvement of EPHA2 in the development of infectious diseases and cancer. Despite pharmacological potential, EPHA2 is an under-examined target protein. In this study, we synthesized a series of derivatives of the inhibitor NVP-BHG712 and triazine-based compounds. These compounds were evaluated to determine their potential as kinase inhibitors of EPHA2, including elucidation of their binding mode (X-ray crystallography), affinity (microscale thermophoresis), and selectivity (Kinobeads assay). Eight inhibitors showed affinities in the low-nanomolar regime (KD <10 nM). Testing in up to seven colon cancer cell lines that express EPHA2 reveals that several derivatives feature promising effects for the control of human colon carcinoma. Thus, we have developed a set of powerful tool compounds for fundamental new research on the interplay of EPH receptors in a cellular context.