EphA3 biology and cancer

Probing phosphorylation events in biological membranes: The transducer function

The extracellular environment is sensed by receptors in the plasma membrane. Some of these receptors initiate cytoplasmic signaling cascades involving phosphorylation: the addition of a phosphate group to a specific amino acid, such as tyrosine, in a protein. Receptor Tyrosine Kinases (RTKs) are one large class of membrane receptors that can directly initiate signaling cascades through their intracellular kinase domains, which both catalyze tyrosine phosphorylation and get phosphorylated. In the first step of signaling, the ligands stabilize phosphorylation-competent RTK dimers and oligomers, which leads to the phosphorylation of specific tyrosine residues in the activation loop of the kinases. Here we discuss quantitative measurements of tyrosine phosphorylation efficiencies for RTKs, described by the "transducer function". The transducer function links the phosphorylation (the response) and the binding of the activating ligand to the receptor (the stimulus). We overview a methodology that allows such measurements in direct response to ligand binding. We discuss experiments which demonstrate that EGF is a partial agonist, and that two tyrosines in the intracellular domain of EGFR, Y1068 and Y1173, are differentially phosphorylated in the EGF-bound EGFR dimers.

Loss of tumor-derived SMAD4 enhances primary tumor growth but not metastasis following BMP4 signalling

BACKGROUND

Bone morphogenetic protein 4 (BMP4) is a potent inhibitor of breast cancer metastasis. However, a tumor-promoting effect of BMP4 is reported in other tumor types, especially when SMAD4 is inactive.

METHODS

To assess the requirement for SMAD4 in BMP4-mediated suppression of metastasis, we knocked down SMAD4 in two different breast tumors and enforced SMAD4 expression in a third line with endogenous SMAD4 deletion. In addition, we assessed the requirement for SMAD4 in tumor cell-specific BMP signalling by expression of a constitutively active BMP receptor. Delineation of genes regulated by BMP4 in the presence or absence of SMAD4 was assessed by RNA sequencing and a BMP4-induced gene, MYO1F was assessed for its role in metastasis. Genes regulated by BMP4 and/or SMAD4 were assessed in a publicly available database of gene expression profiles of breast cancer patients.

RESULTS

In the absence of SMAD4, BMP4 promotes primary tumor growth that is accompanied by increased expression of genes associated with DNA replication, cell cycle, and MYC signalling pathways. Despite increased primary tumor growth, BMP4 suppresses metastasis in the absence of tumor cell expression of SMAD4. Consistent with the anti-metastatic activity of BMP4, enforced signalling through the constitutively active receptor in SMAD4 positive tumors that lacked BMP4 expression still suppressed metastasis, but in the absence of SMAD4, the suppression of metastasis was largely prevented. Thus BMP4 is required for suppression of metastasis regardless of tumor SMAD4 status. The BMP4 upregulated gene, MYO1F, was shown to be a potent suppressor of breast cancer metastasis. Gene signature upregulated by BMP4 in the absence of SMAD4 was associated with poor prognosis in breast cancer patients, whereas gene signature upregulated by BMP4 in the presence of SMAD4 was associated with improved prognosis.

CONCLUSIONS

BMP4 expression is required for suppression of metastasis regardless of the SMAD4 status of the tumor cells. Since BMP4 is a secreted protein, we conclude that it can act both in an autocrine manner in SMAD4-expressing tumor cells and in a paracrine manner on stromal cells to suppress metastasis. Deletion of SMAD4 from tumor cells does not prevent BMP4 from suppressing metastasis via a paracrine mechanism.

Single-cell profiling of MC1R-inhibited melanocytes

The human red hair color (RHC) trait is caused by increased pheomelanin (red-yellow) and reduced eumelanin (black-brown) pigment in skin and hair due to diminished melanocortin 1 receptor (MC1R) function. In addition, individuals harboring the RHC trait are predisposed to melanoma development. While MC1R variants have been established as causative of RHC and are a well-defined risk factor for melanoma, it remains unclear mechanistically why decreased MC1R signaling alters pigmentation and increases melanoma susceptibility. Here, we use single-cell RNA sequencing (scRNA-seq) of melanocytes isolated from RHC mouse models to define a MC1R-inhibited Gene Signature (MiGS) comprising a large set of previously unidentified genes which may be implicated in melanogenesis and oncogenic transformation. We show that one of the candidate MiGS genes, TBX3, a well-known anti-senescence transcription factor implicated in melanoma progression, binds both E-box and T-box elements to regulate genes associated with melanogenesis and senescence bypass. Our results provide key insights into further mechanisms by which melanocytes with reduced MC1R signaling may regulate pigmentation and offer new candidates of study toward understanding how individuals with the RHC phenotype are predisposed to melanoma.

Screening of Biomarkers Associated with Osteoarthritis Aging Genes and Immune Correlation Studies

Purpose

Osteoarthritis (OA) is a joint disease with a long and slow course, which is one of the major causes of disability in middle and old-aged people. This study was dedicated to excavating the cellular senescence-associated biomarkers of OA.

Methods

The Gene Expression Omnibus (GEO) database was searched and five datasets pertaining to OA were obtained. After removing the batch effect, the GSE55235, GSE55457, GSE82107, and GSE12021 datasets were integrated together for screening of the candidate genes by differential analysis and weighted gene co-expression network analysis (WGCNA). Next, those genes were further filtered by machine learning algorithms to obtain cellular senescence-associated biomarkers of OA. Subsequently, enrichment analyses based on those biomarkers were conducted, and we profiled the infiltration levels of 22 types immune cells with the ERSORT algorithm. A lncRNA-miRNA-mRNA regulatory and drug-gene network were constructed. Finally, we validated the senescence-associated biomarkers at both in vivo and in vitro levels.

Results

Five genes (BCL6, MCL1, SLC16A7, PIM1, and EPHA3) were authenticated as cellular senescence-associated biomarkers in OA. ROC curves demonstrated the reliable capacity of the five genes as a whole to discriminate OA samples from normal samples. The nomogram diagnostic model based on 5 genes proved to be a reliable predictor of OA. Single-gene GSEA results pointed to the involvement of the five biomarkers in immune-related pathways and oxidative phosphorylation in the development of OA. Immune infiltration analysis manifested that the five genes were significantly correlated with differential immune cells. Subsequently, a lncRNA-miRNA-mRNA network and gene-drug network containing were generated based on five cellular senescence-associated biomarkers in OA.

Conclusion

A foundation for understanding the pathophysiology of OA and new insights into OA diagnosis and treatment were provided by the identification of five genes, namely BCL6, MCL1, SLC16A7, PIM1, and EPHA3, as biomarkers associated with cellular senescence in OA.

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.

microRNA-365 attenuated intervertebral disc degeneration through modulating nucleus pulposus cell apoptosis and extracellular matrix degradation by targeting EFNA3

This present study is aimed to investigate the role of microRNA-365 (miR-365) in the development of intervertebral disc degeneration (IDD). Nucleus pulposus (NP) cells were transfected by miR-365 mimic and miR-365 inhibitor, respectively. Concomitantly, the transfection efficiency and the expression level of miRNA were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Meanwhile, NP cells apoptosis was measured through propidium iodide (PI)-AnnexinV-fluorescein isothiocyanate (FITC) apoptosis detection kit. Subsequently, immunofluorescence (IF) staining was performed to assess the expression of collagen II, aggrecan and matrix metalloproteinase 13 (MMP-13). In addition, bioinformatic prediction and Luciferase reporter assay were used to reveal the target gene of miR-365. Finally, we isolated the primary NP cells from rats and injected NP-miR-365 in rat IDD models. The results showed that overexpression of miR-365 could effectively inhibit NP cells apoptosis and MMP-13 expression and upregulate the expression of collagen II and aggrecan. Conversely, suppression of miR-365 enhanced NP cell apoptosis and elevated MMP-13 expression, but decreased the expression of collagen II and aggrecan. Moreover, the further data demonstrated that miR-365 mediated NP cell degradation through targeting ephrin-A3 (EFNA3). In addition, the cells apoptosis and catabolic markers were increased in NP cells when EFNA3 upregulated. More importantly, the vivo data supported that miR-365-NP cells injection ameliorated IDD in rats models. miR-365 could alleviate the development of IDD by regulating NP cell apoptosis and ECM degradation, which is likely mediated by targeting EFNA3. Therefore, miR-365 may be a promising therapeutic avenue for treatment IDD through EFNA3.

Comprehensive analyses of immune tumor microenvironment in papillary renal cell carcinoma

BACKGROUND

Papillary renal cell carcinoma (pRCC) is the most common non-clear cell RCC, and associated with poor outcomes in the metastatic setting. In this study, we aimed to comprehensively evaluate the immune tumor microenvironment (TME), largely unknown, of patients with metastatic pRCC and identify potential therapeutic targets.

METHODS

We performed quantitative gene expression analysis of TME using Microenvironment Cell Populations-counter (MCP-counter) methodology, on two independent cohorts of localized pRCC (n=271 and n=98). We then characterized the TME, using immunohistochemistry (n=38) and RNA-sequencing (RNA-seq) (n=30) on metastatic pRCC from the prospective AXIPAP trial cohort.

RESULTS

Unsupervised clustering identified two "TME subtypes", in each of the cohorts: the "immune-enriched" and the "immune-low". Within AXIPAP trial cohort, the "immune-enriched" cluster was significantly associated with a worse prognosis according to the median overall survival to 8 months (95% CI, 6 to 29) versus 37 months (95% CI, 20 to NA, p=0.001). The two immune signatures, Teff and JAVELIN Renal 101 Immuno signature, predictive of response to immune checkpoint inhibitors (CPI) in clear cell RCC, were significantly higher in the "immune-enriched" group (adjusted p<0.05). Finally, five differentially overexpressed genes were identified, corresponding mainly to B lymphocyte populations.

CONCLUSION

For the first time, using RNA-seq and immunohistochemistry, we have highlighted a specific immune TME subtype of metastatic pRCC, significantly more infiltrated with T and B immune population. This "immune-enriched" group appears to have a worse prognosis and could have a potential predictive value for response to immunotherapy, justifying the confirmation of these results in a cohort of metastatic pRCC treated with CPI and in combination with targeted therapies.

TRIAL REGISTRATION NUMBER

NCT02489695.

Inhibition of EphA3 Expression in Tumour Stromal Cells Suppresses Tumour Growth and Progression

Tumour progression relies on interactions with untransformed cells in the tumour microenvironment (TME), including cancer-associated fibroblasts (CAFs), which promote blood supply, tumour progression, and immune evasion. Eph receptor tyrosine kinases are cell guidance receptors that are most active during development but re-emerge in cancer and are recognised drug targets. EphA3 is overexpressed in a wide range of tumour types, and we previously found expression particularly in stromal and vascular tissues of the TME. To investigate its role in the TME, we generated transgenic mice with inducible shRNA-mediated knockdown of EphA3 expression. EphA3 knockdown was confirmed in aortic mesenchymal stem cells (MSCs), which displayed reduced angiogenic capacity. In mice with syngeneic lung tumours, EphA3 knockdown reduced vasculature and CAF/MSC-like cells in tumours, and inhibited tumour growth, which was confirmed also in a melanoma model. Single cell RNA sequencing analysis of multiple human tumour types confirmed EphA3 expression in CAFs, including in breast cancer, where EphA3 was particularly prominent in perivascular- and myofibroblast-like CAFs. Our results thus indicate expression of the cell guidance receptor EphA3 in distinct CAF subpopulations is important in supporting tumour angiogenesis and tumour growth, highlighting its potential as a therapeutic target.

Knockdown of circ_CLIP2 regulates the proliferation, metastasis and apoptosis of glioma cells through miR-641/EPHA3/STAT3 axis

A great amount of reaches have confirmed that circular RNAs (circRNAs) are novel regulators in glioma progression. Here, our work aimed to probe the specific role of circ_CLIP2 in glioma. The mRNA and protein expressions were analyzed by qRT-PCR and western blot, respectively. Cell viability, migration, invasion and apoptosis were examined by MTT assay, tranwell and flow cytometry assays, respectively. Moreover, the binding relationships between circ_CLIP2, microRNA (miR)-641 and erythropoietin-producing human hepatocellular (Eph)A3 were verified by dual luciferase reporter gene assay and/or RIP assay. The following data showed that circ_CLIP2 and EPHA3 were markedly increased in glioma tissues and cells, while miR-647 was downregulated. Gain- and loss-of-function experiments discovered that circ_CLIP2 knockdown remarkably inhibited cell proliferation, migration and invasion and promoted cell apoptosis of glioma cells, while these effects of circ_CLIP2 knockdown were abolished by miR-641 inhibition. Circ_CLIP2 was proved as a sponge of miR-641 to competitively upregulate EPHA3 expression. In addition, EPHA3 overexpression could abolish the inhibitory effects of miR-641 overexpression on the malignant behaviors of glioma cells by activating the signal transducer and activator of transcription 3 (STAT3). These findings elucidated that circ_CLIP2 knockdown suppressed glioma development by regulation of the miR-641/EP HA3/STAT3 axis, which provided a novel mechanism for understanding the pathogenesis of glioma.

Loss of MC1R signaling implicates TBX3 in pheomelanogenesis and melanoma predisposition

The human Red Hair Color (RHC) trait is caused by increased pheomelanin (red-yellow) and reduced eumelanin (black-brown) pigment in skin and hair due to diminished melanocortin 1 receptor (MC1R) function. In addition, individuals harboring the RHC trait are predisposed to melanoma development. While MC1R variants have been established as causative of RHC and are a well-defined risk factor for melanoma, it remains unclear mechanistically why decreased MC1R signaling alters pigmentation and increases melanoma susceptibility. Here, we use single-cell RNA-sequencing (scRNA-seq) of melanocytes isolated from RHC mouse models to reveal a Pheomelanin Gene Signature (PGS) comprising genes implicated in melanogenesis and oncogenic transformation. We show that TBX3, a well-known anti-senescence transcription factor implicated in melanoma progression, is part of the PGS and binds both E-box and T-box elements to regulate genes associated with melanogenesis and senescence bypass. Our results provide key insights into mechanisms by which MC1R signaling regulates pigmentation and how individuals with the RHC phenotype are predisposed to melanoma.

Identification of Cancer Driver Genes by Integrating Multiomics Data with Graph Neural Networks

Cancer is a heterogeneous disease that is driven by the accumulation of both genetic and nongenetic alterations, so integrating multiomics data and extracting effective information from them is expected to be an effective way to predict cancer driver genes. In this paper, we first generate comprehensive instructive features for each gene from genomic, epigenomic, transcriptomic levels together with protein–protein interaction (PPI)-networks-derived attributes and then propose a novel semisupervised deep graph learning framework GGraphSAGE to predict cancer driver genes according to the impact of the alterations on a biological system. When applied to eight tumor types, experimental results suggest that GGraphSAGE outperforms several state-of-the-art computational methods for driver genes identification. Moreover, it broadens our current understanding of cancer driver genes from multiomics level and identifies driver genes specific to the tumor type rather than pan-cancer. We expect GGraphSAGE to open new avenues in precision medicine and even further predict drivers for other complex diseases.

Eph Receptors in Cancer

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

EPHA3 Could Be a Novel Prognosis Biomarker and Correlates with Immune Infiltrates in Bladder Cancer

PURPOSE

To assess the mechanism of EPH receptor A3 (EPHA3) and its potential value for immunotherapy in BLCA.

MATERIALS AND METHODS

The Cancer Genome Atlas (TCGA) bladder cancer (BLCA) database and the Gene Expression Omnibus (GEO) database were used for assessing whether EHPA3 could be used to predict BLCA prognosis. This work carried out in vitro and in vivo assays for exploring how EPHA3 affected the biological behaviors. The downstream pathway was explored using a Western blotting technique. The CIBERSORT, ESTIMATE, TIMER, and TIDE tools were used to predict the immunotherapy value of EPHA3 in BLCA.

RESULTS

EPHA3 was poorly expressed in BLCA (p < 0.05), its high expression is related to a good survival prognosis (p = 0.027 and p = 0.0275), and it has a good predictive ability for the histologic grade and status of BLCA (area under curve = 0.787 and 0.904). Overexpressed EPHA3 could inhibit BLCA cell biological behaviors, and it be associated with the downregulation of the Ras/pERK1/2 pathway. EPHA3 was correlated with several immune-infiltrating cells and the corresponding marker genes.

CONCLUSIONS

EPHA3 could be regarded as an acceptable anti-cancer biomarker in BLCA. EPHA3 plays an inhibiting role in BLCA, and it could be the candidate immunotherapeutic target for BLCA.

The role of gene-ambient air pollution interactions in paediatric asthma

Globally, asthma prevention and treatment remain a challenge. Ambient air pollution (AAP) is an environmental risk factor of special interest in asthma research. AAP is poorly defined and has been subdivided either by the origin of the air pollution or by the specific bioactive compounds. The link between AAP exposure and asthma exacerbations is well established and has been extensively reviewed. In this narrative review, we discuss the specific genetic variants that have been associated with increased AAP sensitivity and impact in paediatric asthma. We highlight the relative importance of variants associated with genes with a role in oxidant defences and the nuclear factor-κB pathway supporting a potential central role for these pathways in AAP sensitivity.

Glioblastoma Multiforme Selective Nanomedicines for Improved Anti-Cancer Treatments

Glioblastoma Multiforme (GBM) is a devastating disease with a low survival rate and few efficacious treatment options. The fast growth, late diagnostics, and off-target toxicity of currently used drugs represent major barriers that need to be overcome to provide a viable cure. Nanomedicines (NMeds) offer a way to overcome these pitfalls by protecting and loading drugs, increasing blood half-life, and being targetable with specific ligands on their surface. In this study, the FDA-approved polymer poly (lactic-co-glycolic) acid was used to optimise NMeds that were surface modified with a series of potential GBM-specific ligands. The NMeds were fully characterised for their physical and chemical properties, and then in vitro testing was performed to evaluate cell uptake and GBM cell specificity. While all targeted NMeds showed improved uptake, only those decorated with the-cell surface vimentin antibody M08 showed specificity for GBM over healthy cells. Finally, the most promising targeted NMed candidate was loaded with the well-known chemotherapeutic, paclitaxel, to confirm targeting and therapeutic effects in C6 GBM cells. These results demonstrate the importance of using well-optimised NMeds targeted with novel ligands to advance delivery and pharmaceutical effects against diseased cells while minimising the risk for nearby healthy cells.

LIM Kinases, Promising but Reluctant Therapeutic Targets: Chemistry and Preclinical Validation In Vivo

LIM Kinases are important actors in the regulation of cytoskeleton dynamics by controlling microtubule and actin filament turnover. The signaling pathways involving LIM kinases for actin filament remodeling are well established. They are downstream effectors of small G proteins of the Rho-GTPases family and have become promising targets for the treatment of several major diseases because of their position at the lower end of these signaling cascades. Cofilin, which depolymerizes actin filaments, is the best-known substrate of these enzymes. The phosphorylation of cofilin to its inactive form by LIM kinases avoids actin filament depolymerization. The balance between phosphorylated and non-phosphorylated cofilin is thought to play an important role in tumor cell invasion and metastasis. Since 2006, many small molecules have been developed for LIMK inhibition, and in this review article, we will discuss the structure–activity relationships of the few inhibitor families that have been tested in vivo on different pathological models.

Comparative Pathobiology of Canine and Human Prostate Cancer: State of the Art and Future Directions

First described in 1817, prostate cancer is considered a complex neoplastic entity, and one of the main causes of death in men in the western world. In dogs, prostatic carcinoma (PC) exhibits undifferentiated morphology with different phenotypes, is hormonally independent of aggressive character, and has high rates of metastasis to different organs. Although in humans, the risk factors for tumor development are known, in dogs, this scenario is still unclear, especially regarding castration. Therefore, with the advent of molecular biology, studies were and are carried out with the aim of identifying the main molecular mechanisms and signaling pathways involved in the carcinogenesis and progression of canine PC, aiming to identify potential biomarkers for diagnosis, prognosis, and targeted treatment. However, there are extensive gaps to be filled, especially when considering the dog as experimental model for the study of this neoplasm in humans. Thus, due to the complexity of the subject, the objective of this review is to present the main pathobiological aspects of canine PC from a comparative point of view to the same neoplasm in the human species, addressing the historical context and current understanding in the scientific field.

CAF-Associated Paracrine Signaling Worsens Outcome and Potentially Contributes to Chemoresistance in Epithelial Ovarian Cancer

Background

High-grade serous ovarian cancer (HGSOC) is the predominant and deadliest form of ovarian cancer. Some of its histological subtypes can be distinguished by frequent occurrence of cancer-associated myofibroblasts (CAFs) and desmoplastic stroma reaction (DSR). In this study, we want to explore the relationship between therapy outcome and the activity of CAF-associated signaling pathways in a homogeneous HGSOC patient collective. Furthermore, we want to validate these findings in a general Epithelial ovarian cancer (EOC) cohort.

Methods

The investigation cohort consists of 24 HGSOC patients. All of them were treated with platinum-based components and clinical follow-up was available. The validation cohort was comprised of 303 patients. Sequencing data (whole transcriptome) and clinical data were extracted from The Cancer Genome Atlas (TCGA). RNA of HGSOC patients was isolated using a Maxwell RSC instrument and the appropriate RNA isolation kit. For digital expression analysis a custom-designed gene panel was employed. All genes were linked to various DSR- and CAF- associated pathways. Expression analysis was performed on the NanoString nCounter platform. Finally, data were explored using the R programming environment (v. 4.0.3).

Result

In total, 15 CAF-associated genes were associated with patients’ survival. More specifically, 6 genes (MMP13, CGA, EPHA3, PSMD9, PITX2, PHLPP1) were linked to poor therapy outcome. Though a variety of different pathways appeared to be associated with therapy failure, many were related to CAF paracrine signaling, including MAPK, Ras and TGF-β pathways. Similar results were obtained from the validation cohort.

Discussion

In this study, we could successfully link CAF-associated pathways, as shown by increased Ras, MAPK and PI3K-Akt signaling to therapy failure (chemotherapy) in HGSOC and EOCs in general. As platinum-based chemotherapy has been the state-of-the-art therapy to treat HGSOC for decades, it is necessary to unveil the reasons behind resistance developments and poor outcome. In this work, CAF-associated signaling is shown to compromise therapy response. In the validation cohort, CAF-associated signaling is also associated with therapy failure in general EOC, possibly hinting towards a conserved mechanism. Therefore, it may be helpful to stratify HGSOC patients for CAF activity and consider alternative treatment options.

The Ephb2 Receptor Uses Homotypic, Head-to-Tail Interactions within Its Ectodomain as an Autoinhibitory Control Mechanism

The Eph receptor tyrosine kinases and their ephrin ligands direct axon pathfinding and neuronal cell migration, as well as mediate many other cell-cell communication events. Their dysfunctional signaling has been shown to lead to various diseases, including cancer. The Ephs and ephrins both localize to the plasma membrane and, upon cell-cell contact, form extensive signaling assemblies at the contact sites. The Ephs and the ephrins are divided into A and B subclasses based on their sequence conservation and affinities for each other. The molecular details of Eph-ephrin recognition have been previously revealed and it has been documented that ephrin binding induces higher-order Eph assemblies, which are essential for full biological activity, via multiple, distinct Eph-Eph interfaces. One Eph-Eph interface type is characterized by a homotypic, head-to-tail interaction between the ligand-binding and the fibronectin domains of two adjacent Eph molecules. While the previous Eph ectodomain structural studies were focused on A class receptors, we now report the crystal structure of the full ectodomain of EphB2, revealing distinct and unique head-to-tail receptor-receptor interactions. The EphB2 structure and structure-based mutagenesis document that EphB2 uses the head-to-tail interactions as a novel autoinhibitory control mechanism for regulating downstream signaling and that these interactions can be modulated by posttranslational modifications.

Cell-Extrinsic Differentiation Block Mediated by EphA3 in Pre-Leukaemic Thymus Contributes to Disease Progression

Simple Summary

The NUP98-HOXD13 (NHD13) mouse is a model of T-cell leukaemia (T-ALL) featuring a pre-leukemic phase, in which T-cell progenitors from the thymus of an NHD13 mouse can engraft into the thymus of a recipient mouse—an ability that normal T-cell progenitors do not possess. However, loss of this engraftment ability (by deletion of the Lyl1 gene) did not result in any loss of leukemogenesis activity, indicating the activity of redundant oncogenic pathways in this model. Having observed an overexpression of the EphA3 protein in the NHD13 thymocytes, we hypothesized that this gene might be involved in a redundant leukaemogenic pathway. Deletion of EphA3 did not affect the engraftment ability of the thymocytes, but did reduce the incidence of T-ALL. We thus uncovered a distinct mechanism of leukaemogenesis, which we believe operates in parallel to that mediated by Lyl1.

Abstract

We recently characterised the NUP98-HOXD13 (NHD13) mouse as a model of T-cell pre-leukaemia, featuring thymocytes that can engraft in recipient animals and progress to T-cell acute lymphoblastic leukaemia (T-ALL). However, loss of this engraftment ability by deletion of Lyl1 did not result in any loss of leukemogenesis activity. In the present study, we observe that NHD13 thymocytes overexpress EPHA3, and we characterise thymocyte behaviour in NHD13 mice with deletion of EphA3, which show a markedly reduced incidence of T-ALL. Deletion of EphA3 from the NHD13 mice does not prevent the abnormal accumulation or transplantation ability of these thymocytes. However, upon transplantation, these cells are unable to block the normal progression of recipient wild type (WT) progenitor cells through the normal developmental pathway. This is in contrast to the EphA3^+/+ NHD13 thymocytes, which block the progression of incoming WT progenitors past the DN1 stage. Therefore, EphA3 is not critical for classical self-renewal, but is essential for mediating an interaction between the abnormally self-renewing cells and healthy progenitors—an interaction that results in a failure of the healthy cells to differentiate normally. We speculate that this may orchestrate a loss of healthy cell competition, which in itself has been demonstrated to be oncogenic, and that this may explain the decrease in T-ALL incidence in the absence of EphA3. We suggest that pre-leukaemic self-renewal in this model is a complex interplay of cell-intrinsic and -extrinsic factors, and that multiple redundant pathways to leukaemogenesis are active.

Antibody-mediated depletion of CCR10+EphA3+ cells ameliorates fibrosis in IPF

Idiopathic pulmonary fibrosis (IPF) is characterized by aberrant repair that diminishes lung function via mechanisms that remain poorly understood. CC chemokine receptor (CCR10) and its ligand CCL28 were both elevated in IPF compared with normal donors. CCR10 was highly expressed by various cells from IPF lungs, most notably stage-specific embryonic antigen-4-positive mesenchymal progenitor cells (MPCs). In vitro, CCL28 promoted the proliferation of CCR10+ MPCs while CRISPR/Cas9-mediated targeting of CCR10 resulted in the death of MPCs. Following the intravenous injection of various cells from IPF lungs into immunodeficient (NOD/SCID-γ, NSG) mice, human CCR10+ cells initiated and maintained fibrosis in NSG mice. Eph receptor A3 (EphA3) was among the highest expressed receptor tyrosine kinases detected on IPF CCR10+ cells. Ifabotuzumab-targeted killing of EphA3+ cells significantly reduced the numbers of CCR10+ cells and ameliorated pulmonary fibrosis in humanized NSG mice. Thus, human CCR10+ cells promote pulmonary fibrosis, and EphA3 mAb-directed elimination of these cells inhibits lung fibrosis.

IL-26 mediates epidermal growth factor receptor-tyrosine kinase inhibitor resistance through endoplasmic reticulum stress signaling pathway in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) has a poor prognosis compared to other breast cancer subtypes. Although epidermal growth factor receptor (EGFR) is overexpressed in TNBC, clinical trials with EGFR inhibitors including tyrosine kinase inhibitors (EGFR-TKI) in TNBC have heretofore been unsuccessful. To develop effective EGFR-targeted therapy for TNBC, the precise mechanisms of EGFR-TKI resistance in TNBC need to be elucidated. In this study, to understand the molecular mechanisms involved in the differences in EGFR-TKI efficacy on TNBC between human and mouse, we focused on the effect of IL-26, which is absent in mice. In vitro analysis showed that IL-26 activated AKT and JNK signaling of bypass pathway of EGFR-TKI in both murine and human TNBC cells. We next investigated the mechanisms involved in IL-26-mediated EGFR-TKI resistance in TNBC. We identified EphA3 as a novel functional receptor for IL-26 in TNBC. IL-26 induced dephosphorylation and downmodulation of EphA3 in TNBC, which resulted in increased phosphorylation of AKT and JNK against EGFR-TKI-induced endoplasmic reticulum (ER) stress, leading to tumor growth. Meanwhile, the blockade of IL-26 overcame EGFR-TKI resistance in TNBC. Since the gene encoding IL-26 is absent in mice, we utilized human IL-26 transgenic (hIL-26Tg) mice as a tumor-bearing murine model to characterize the role of IL-26 in the differential effect of EGFR-TKI in human and mice and to confirm our in vitro findings. Our findings indicate that IL-26 activates the bypass pathway of EGFR-TKI, while blockade of IL-26 overcomes EGFR-TKI resistance in TNBC via enhancement of ER stress signaling. Our work provides novel insights into the mechanisms of EGFR-TKI resistance in TNBC via interaction of IL-26 with its newly identified receptor EphA3, while also suggesting IL-26 as a possible therapeutic target in TNBC.

Sam68 Promotes the Progression of Human Breast Cancer through inducing Activation of EphA3

BACKGROUND

Src associated with mitosis of 68 kDa (Sam68), is often highly expressed in human cancers. Overexpression of Sam68 has been shown to be correlated with poor survival prognosis in some cancer patients. However, little is known whether Sam68 plays a role in promoting metastasis in breast cancer.

MATERIALS AND METHODS

The expression of Sam68 protein in breast cancer tissue was detected by immunohistochemistry. Trans-well assay, wound-healing, real-time PCR and Western blotting analysis were used to detect the effect of Sam68 on promoting EMT or metastasis of breast cancer. Next-generation RNA sequencing was used to analyze genes that may be regulated by Sam68.

RESULTS

Sam68 plays a positive role in promoting breast cancer metastasis. Sam68 was found to be overexpressed in breast cancer along with lymph node metastasis. MMP-9 was also found to be overexpressed in breast cancer tissue and was correlated to the expression of Sam68 (P<0.01). Xenograft in NOD/SCID mice and in vitro experiments confirmed that the invasion and metastatic ability of breast cancer cells were regulated by Sam68. And EPHA3 could be up-regulated by Sam68 in breast cancer.

CONCLUSION

High expression of Sam68 participates in breast cancer metastasis by up-regulating the EPHA3 gene.

EPHA3 Contributes to Epigenetic Suppression of PTEN in Radioresistant Head and Neck Cancer

EPHA3, a member of the EPH family, is overexpressed in various cancers. We demonstrated previously that EPHA3 is associated with radiation resistance in head and neck cancer via the PTEN/Akt/EMT pathway; the inhibition of EPHA3 significantly enhances the efficacy of radiotherapy in vitro and in vivo. In this study, we investigated the mechanisms of PTEN regulation through EPHA3-related signaling. Increased DNA methyltransferase 1 (DNMT1) and enhancer of zeste homolog 2 (EZH2) levels, along with increased histone H3 lysine 27 trimethylation (H3K27me3) levels, correlated with decreased levels of PTEN in radioresistant head and neck cancer cells. Furthermore, PTEN is regulated in two ways: DNMT1-mediated DNA methylation, and EZH2-mediated histone methylation through EPHA3/C-myc signaling. Our results suggest that EPHA3 could display a novel regulatory mechanism for the epigenetic regulation of PTEN in radioresistant head and neck cancer cells.

Recent advances in development of hetero-bivalent kinase inhibitors

Identifying a pharmacological agent that targets only one of more than 500 kinases present in humans is an important challenge. One potential solution to this problem is the development of bivalent kinase inhibitors, which consist of two connected fragments, each bind to a dissimilar binding site of the bisubstrate enzyme. The main advantage of bivalent (type V) kinase inhibitors is generating more interactions with target enzymes that can enhance the molecules' selectivity and affinity compared to single-site inhibitors. Earlier type V inhibitors were not suitable for the cellular environment and were mostly used in in vitro studies. However, recently developed bivalent compounds have high kinase affinity, high biological and chemical stability in vivo. This review summarized the hetero-bivalent kinase inhibitors described in the literature from 2014 to the present. We attempted to classify the molecules by serine/threonine and tyrosine kinase inhibitors, and then each target kinase and its hetero-bivalent inhibitor was assessed in depth. In addition, we discussed the analysis of advantages, limitations, and perspectives of bivalent kinase inhibitors compared with the monovalent kinase inhibitors.

Glioblastoma Break-in; Try Something New

Context: Glioblastoma is the most invasive brain tumor with a poor prognosis and rapid progression. The standard therapy (surgical resection, adjuvant chemotherapy, and radiotherapy) ensures survival only up to 18 months. In this article, we focus on innovative types of radiotherapy, various combinations of temozolomide with novel substances, and methods of their administration and vector delivery to tumor cells. Evidence Acquisition: For a detailed study of the various options for chemotherapy and radiotherapy, Elsevier, NCBI MedLine, Scopus, Google Scholar, Embase, Web of Science, The Cochrane Library, EMBASE, Global Health, CyberLeninka, and RSCI databases were analyzed. Results: The most available method is oral or intravenous administration of temozolomide. More efficient is the combined chemotherapy of temozolomide with innovative drugs and substances such as lomustine, histone deacetylase inhibitors, and chloroquine, as well as olaparib. These combinations improve patient survival and are effective in the treatment of resistant tumors. Compared to standard fractionated radiotherapy (60 Gy, 30 fractions, 6 weeks), hypofractionated is more effective for elderly patients due to lack of toxicity; brachytherapy reduces the risk of glioblastoma recurrence, while radiosurgery with bevacizumab is more effective against recurrent or inoperable tumors. Currently, the most effective treatment is considered to be the intranasal administration of anti-Ephrin A3 (anti-EPHA3)-modified containing temozolomide butyl ester-loaded (TBE-loaded) poly lactide-co-glycolide nanoparticles (P-NPs) coated with N-trimethylated chitosan (TMC) to overcome nasociliary clearance. Conclusions: New radiotherapeutic methods significantly increase the survival rates of glioblastoma patients. With some improvement, it may lead to the elimination of all tumor cells leaving the healthy alive. New chemotherapeutic drugs show impressive results with adjuvant temozolomide. Anti-EPHA3-modified TBE-loaded P-NPs coated with TMC have high absorption specificity and kill glioblastoma cells effectively. A new “step forward” may become a medicine of the future, which reduces the specific accumulation of nanoparticles in the lungs, but simultaneously does not affect specific absorption by tumor cells.

The EphA2 and cancer connection: potential for immune-based interventions

The Eph (erythropoietin-producing human hepatocellular) receptors form the largest known subfamily of receptor tyrosine kinases. These receptors interact with membrane-bound ephrin ligands via direct cell-cell interactions resulting in bi-directional activation of signal pathways. Importantly, the Eph receptors play critical roles in embryonic tissue organization and homeostasis, and in the maintenance of adult processes such as long-term potentiation, angiogenesis, and stem cell differentiation. The Eph receptors also display properties of both tumor promoters and suppressors depending on the cellular context. Characterization of EphA2 receptor in regard to EphA2 dysregulation has revealed associations with various pathological processes, especially cancer. The analysis of various tumor types generally identify EphA2 receptor as overexpressed and/or mutated, and for certain types of cancers EphA2 is linked with poor prognosis and decreased patient survival. Thus, here we highlight the role of EphA2 in malignant tissues that are specific to cancer; these include glioblastoma multiforme, prostate cancer, ovarian and uterine cancers, gastric carcinoma, melanoma, and breast cancer. Due to its large extracellular domain, therapeutic targeting of EphA2 with monoclonal antibodies (mAbs), which may function as inhibitors of ligand activation or as molecular agonists, has been an oft-attempted strategy. Therefore, we review the most current mAb-based therapies against EphA2 expressing cancers currently in pre-clinical and/or clinical stages. Finally, we discuss the latest peptides and cyclical-peptides that function as selective agonists for EphA2 receptor.

Critical role of EphA3 in cancer and current state of EphA3 drug therapeutics

The erythropoietin-producing human hepatocellular (Eph) receptors are transmembrane glycoprotein members of the tyrosine kinase receptors family. The Ephs may bind to various ephrin ligands resulting in the phosphorylation of their tyrosine kinase domain and the activation of the Eph receptor. In this review we focus on EphA3, one receptor of the 14 different Ephs, as it carries out both redundant and restricted functions in the germline development of mammals and in the maintenance of various adult tissues. The loss of EphA3 regulation is correlated with various human malignancies, the most notable being cancer. This receptor is overexpressed and/or mutated in multiple tumors, and is also associated with poor prognosis and decreased survival in patients. Here we highlight the role of EphA3 in normal and malignant tissues that are specific to cancer; these include hematologic disorders, gastric cancer, glioblastoma multiforme, colorectal cancer, lung cancer, renal cell carcinoma, and prostate cancer. Moreover, various anticancer agents against EphA3 have been developed to either inhibit its kinase domain activity or to function as agonists. Thus, we examine the most potent small molecule drugs and mAb-based therapeutics against EphA3 that are currently in pre-clinical or clinical stages.

Antibody Targeting of Eph Receptors in Cancer

The Eph subfamily of receptor tyrosine kinases mediate cell-cell communication controlling cell and tissue patterning during development. While generally less active in adult tissues, they often re-emerge in cancers, particularly on undifferentiated or progenitor cells in tumors and the tumor microenvironment, associated with tumor initiation, angiogenesis and metastasis. Eph receptors are thus attractive therapeutic targets, and monoclonal antibodies have been commonly developed and tested for anti-cancer activity in preclinical models, and in some cases in the clinic. This review summarizes 20 years of research on various antibody-based approaches to target Eph receptors in tumors and the tumor microenvironment, including their mode of action, tumor specificity, and efficacy in pre-clinical and clinical testing.

Nasal Drug Delivery of Anticancer Drugs for the Treatment of Glioblastoma: Preclinical and Clinical Trials

Glioblastoma (GBM) is the most lethal form of brain tumor, being characterized by the rapid growth and invasion of the surrounding tissue. The current standard treatment for glioblastoma is surgery, followed by radiotherapy and concurrent chemotherapy, typically with temozolomide. Although extensive research has been carried out over the past years to develop a more effective therapeutic strategy for the treatment of GBM, efforts have not provided major improvements in terms of the overall survival of patients. Consequently, new therapeutic approaches are urgently needed. Overcoming the blood–brain barrier (BBB) is a major challenge in the development of therapies for central nervous system (CNS) disorders. In this context, the intranasal route of drug administration has been proposed as a non-invasive alternative route for directly targeting the CNS. This route of drug administration bypasses the BBB and reduces the systemic side effects. Recently, several formulations have been developed for further enhancing nose-to-brain transport, mainly with the use of nano-sized and nanostructured drug delivery systems. The focus of this review is to provide an overview of the strategies that have been developed for delivering anticancer compounds for the treatment of GBM while using nasal administration. In particular, the specific properties of nanomedicines proposed for nose-to-brain delivery will be critically evaluated. The preclinical and clinical data considered supporting the idea that nasal delivery of anticancer drugs may represent a breakthrough advancement in the fight against GBM.

Nose-to-brain delivery of temozolomide-loaded PLGA nanoparticles functionalized with anti-EPHA3 for glioblastoma targeting

Glioblastoma is the most common malignant brain tumor. Efficient delivery of drugs targeting glioblastomas remains a challenge. Ephrin type-A receptor 3 (EPHA3) tyrosine kinase antibody-modified polylactide-co-glycolide (PLGA) nanoparticles (NPs) were developed to target glioblastoma via nose-to-brain delivery. Anti-EPHA3-modified, TBE-loaded NPs were prepared using an emulsion-solvent evaporation method, showed a sustained in vitro release profile up to 48 h and a mean particle size of 145.9 ± 8.7 nm. The cellular uptake of anti-EPHA3-modified NPs by C6 cells was significantly enhanced compared to that of nontargeting NPs (p < .01). In vivo imaging and distribution studies on the glioma-bearing rats showed that anti-EPHA3-modified NPs exhibited high fluorescence intensity in the brain and effectively accumulated to glioma tissues, indicating the targeting effect of anti-EPHA3. Glioma-bearing rats treated with anti-EPHA3-modified NPs resulted in significantly higher tumor cell apoptosis (p < .01) than that observed with other formulations and prolonged the median survival time of glioma-bearing rats to 26 days, which was 1.37-fold longer than that of PLGA NPs. The above results indicated that anti-EPHA3-modified NPs may potentially serve as a nose-to-brain drug carrier for the treatment of glioblastoma.

The prognosis value of EphA3 and the androgen receptor in prostate cancer treated with radical prostatectomy

Background

This study aimed to preliminarily assess the relationship between erythropoietin‐producing hepatocellular carcinoma receptor A3 (EphA3) and androgen receptor (AR) protein expression levels and prognosis in prostate cancer (PCa) to better understand the role of EphA3 in the prognosis and progression of PCa.

Materials

We investigated the expression of EphA3 and AR in human PCa by immunohistochemistry.

Results

EphA3 and AR were both significantly upregulated in PCa, with expression mainly localized to the nucleus. A high level of AR expression was found in 48.4% of 64 tumor samples, which was significantly more than in the adjacent tissue samples (15.6%) (P < 0.01). The percentage of samples expressing a high level of EphA3 was significantly greater in the PCa samples (54.7%) than in the adjacent tissue samples (20.3%) for the 64 tumors (P < 0.01). The high levels of EphA3 and AR expression in the PCa tissue samples were both correlated with the pathological stage, bladder and rectal invasion, distant metastasis, and preoperative PSA level (both P < 0.05). The survival time was significantly shorter in high levels of AR expression of patients. (P < 0.01). A high level of EphA3 in PCa patients suggests a poor prognosis (P < 0.05). Biochemical recurrence, distant metastasis, and the final scores of EphA3 and AR expression were significantly correlated with the prognosis of PCa (P < 0.05).

Conclusions

Increased EphA3 expression is an independent prognostic factor for a poor outcome and decreased survival in PCa.

Integrative genomic analysis of peritoneal malignant mesothelioma: understanding a case with extraordinary chemotherapy response

Peritoneal malignant mesothelioma is a rare disease with a generally poor prognosis and poor response to chemotherapy. To improve survival there is a need for increased molecular understanding of the disease, including chemotherapy sensitivity and resistance. We here present an unusual case concerning a young woman with extensive peritoneal mesothelioma who had a remarkable response to palliative chemotherapy (platinum/pemetrexed). Tumor samples collected at surgery before and after treatment were analyzed on the genomic and transcriptional levels (exome sequencing, RNA-seq, and smallRNA-seq). Integrative analysis of single nucleotide and copy-number variants, mutational signatures, and gene expression was performed to provide a comprehensive picture of the disease. LATS1/2 were identified as the main mutational drivers together with homozygous loss of BAP1 and PBRM1, which also may have contributed to the extraordinary chemotherapy response. The presence of the S3 mutational signature is consistent with homologous recombination DNA repair defects due to BAP1 loss. Up-regulation of the PI3K/AKT/mTOR pathway after treatment, supported by deactivated PTEN through miRNA regulation, is associated with cancer progression and could explain chemotherapy resistance. The molecular profile suggests potential benefit from experimental targeting of PARP, EZH2, the PI3K/AKT/mTOR pathway and possibly also from immune checkpoint inhibition. In addition to providing the molecular background for this unusual case of peritoneal mesothelioma, the results show the potential value of integrative genomic analysis in precision medicine.

Converting a weaker ATP-binding site inhibitor into a potent hetero-bivalent ligand by tethering to a unique peptide sequence derived from the same kinase

Attaching an additional binding site directed moiety or a ligand to an ATP-binding site inhibitor has been used as a strategy to increase kinase binding affinity and specificity. The moieties typically used here as the second binding partner are varied from simple organic groups to ligands such as peptides derived from substrate binding site sequences. So far these hetero-bivalent ligands were developed targeting additional binding sites closer to the ATP-binding pocket. Here we report a unique expansion of this hetero-bivalent idea by: (I) targeting a new binding site much farther away from ATP-binding site, (II) using a peptide uniquely derived from a portion of the same kinase sequence that has been reported to turn and bind to the above distance binding pocket (used as the second binding ligand), and (III) optimizing a much longer and flexible linker (to connect ATP-binding site inhibitor and above mentioned second peptide sequence) with multistep, yet complete on-bead synthesis approach. We converted a very weak EphA3-kinase ATP-binding site inhibitor-PP2 into a potent hetero-bivalent ligand by tethering to a unique 5-mer peptide sequence that derived from the linker region of EphA3 that connects kinase and sterile alpha motif (SAM) domains. Our design highlight the use of distance binding pockets to ATP-binding site as the second targeted site, while introducing the idea of extracting natural peptide sequences that already exist within the same kinase sequence, by a careful screening of available crystal structures.

EphA3 Pay-Loaded Antibody Therapeutics for the Treatment of Glioblastoma

The EphA3 receptor has recently emerged as a functional tumour-specific therapeutic target in glioblastoma (GBM). EphA3 is significantly elevated in recurrent disease, is most highly expressed on glioma stem cells (GSCs), and has a functional role in maintaining self-renewal and tumourigenesis. An unlabelled EphA3-targeting therapeutic antibody is currently under clinical assessment in recurrent GBM patients. In this study, we assessed the efficacy of EphA3 antibody drug conjugate (ADC) and radioimmunotherapy (RIT) approaches using orthotopic animal xenograft models. Brain uptake studies, using positron emission tomography/computed tomography (PET/CT) imaging, show EphA3 antibodies are effectively delivered across the blood-tumour barrier and accumulate at the tumour site with no observed normal brain reactivity. A robust anti-tumour response, with no toxicity, was observed using EphA3, ADC, and RIT approaches, leading to a significant increase in overall survival. Our current research provides evidence that GBM patients may benefit from pay-loaded EphA3 antibody therapies.

EphA3 inhibits migration and invasion of esophageal cancer cells by activating the mesenchymal‑epithelial transition process

Eph receptor tyrosine kinases are critical for cell‑cell communication during normal and oncogenic development. Eph receptor A3 (EphA3) expression is associated with tumor promotion in certain types of cancer; however, it acts as a tumor suppressor in others. The expression levels of EphA3 and its effects on tumor progression in esophageal squamous cell carcinoma (ESCC) cell lines were determined using reverse transcription‑quantitative polymerase chain reaction analysis and a Transwell invasion assay. The present study demonstrated that EphA3 expression was decreased in ESCC tissues and cell lines. Treatment with the DNA methylation inhibitor 5‑aza‑2'‑deoxycytidine increased the mRNA expression levels of EphA3 in the ESCC cell lines KYSE510 and KYSE30. In addition, overexpression of EphA3 in KYSE450 and KYSE510 cells inhibited cell migration and invasion. EphA3 overexpression also decreased RhoA GTPase. Furthermore, EphA3 overexpression induced mesenchymal‑epithelial transition, as demonstrated by epithelial‑like morphological alterations, increased expression of epithelial proteins (E‑cadherin and the tight junction protein 1 zonula occludens‑1) and decreased expression of mesenchymal proteins (Vimentin, N‑cadherin and Snail). Conversely, silencing EphA3 in KYSE410 cells triggered epithelial‑mesenchymal transition, and promoted cell migration and invasion. These results suggested that EphA3 may serve a tumor‑suppressor role in ESCC.

Therapeutic potential of targeting the Eph/ephrin signaling complex

The Eph-ephrin signaling pathway mediates developmental processes and the proper functioning of the adult human body. This distinctive bidirectional signaling pathway includes a canonical downstream signal cascade inside the Eph-bearing cells, as well as a reverse signaling in the ephrin-bearing cells. The signaling is terminated by ADAM metalloproteinase cleavage, internalization, and degradation of the Eph/ephrin complexes. Consequently, the Eph-ephrin-ADAM signaling cascade has emerged as a key target with immense therapeutic potential particularly in the context of cancer. An interesting twist was brought forth by the emergence of ephrins as the entry receptors for the pathological Henipaviruses, which has spurred new studies to target the viral entry. The availability of high-resolution structures of the multi-modular Eph receptors in complexes with ephrins and other binding partners, such as peptides, small molecule inhibitors and antibodies, offers a wealth of information for the structure-guided development of therapeutic intervention. Furthermore, genomic data mining of Eph mutants involved in cancer provides information for targeted drug development. In this review we summarize the distinct avenues for targeting the Eph-ephrin signaling pathway, including its termination by ADAM proteinases. We highlight the latest developments in Eph-related pharmacology in the context of Eph-ephrin-ADAM-based antibodies and small molecules. Finally, the future prospects of genomics- and proteomics-based medicine are discussed.

Association of EPHA3 Gene Polymorphisms with Nonsyndromic Cleft Lip With or Without Cleft Palate

AIMS

Nonsyndromic cleft lip with or without palate (NSCL/P) represents a complex condition caused by genetic and environmental factors. The aim of this study was to investigate the relationship between the EPHA3 polymorphisms and NSCL/P.

MATERIALS AND METHODS

To investigate the relationship between five EPHA3 single nucleotide polymorphisms (SNPs) and NSCL/P, we selected 180 affected patients and 167 normal controls from the Chinese Han Population. EPHA3 SNPs (rs7650466, rs1398197, rs17801309, rs1054750, and rs7632427) were genotyped using the SNaPshot technique; bioinformatic analyses were performed to determine if any of them were potentially functional SNPs.

RESULTS

The rs7650466 T allele was associated with the incidence of NSCL/P (OR, 0.211; 95% CI, 0.131-0.338; adjusted p = 4.881 × 10^-10) and cleft lip with or without palate (CL/P) (OR, 0.176; 95% CI, 0.104-0.297; adjusted p = 3.617 × 10^-10), as well as with protective and dominant effects in both conditions. The rs7650466 T allele could be associated with reduced risk of the malformation. In a bioinformatics analysis, we found potential matching sites (miR-1255a, miR-125a-3p, miR-143, and miR-552) for rs7650466 and preliminarily analyzed its potential function.

CONCLUSIONS

Collectively, our data suggest that the EPHA3 rs7650466 polymorphism confers genetic risk for NSCL/P in the Chinese Han Population. Furthermore, rs7650466 is associated with CL/P incidence in stratified analyses, but not with cleft palate only.

EphA3 maintains radioresistance in head and neck cancers through epithelial mesenchymal transition

Radiotherapy is a well-established therapeutic modality used in the treatment of many cancers. However, radioresistance remains a serious obstacle to successful treatment. Radioresistance can cause local recurrence and distant metastases in some patients after radiation treatment. Thus, many studies have attempted to identify effective radiosensitizers. Eph receptor functions contribute to tumor development, modulating cell-cell adhesion, invasion, neo-angiogenesis, tumor growth and metastasis. However, the role of EphA3 in radioresistance remains unclear. In the current study, we established a stable radioresistant head and neck cancer cell line (AMC HN3R cell line) and found that EphA3 was expressed predominantly in the radioresistant head and neck cancer cell line through DNA microarray, real time PCR and Western blotting. Additionally, we found that EphA3 was overexpressed in recurrent laryngeal cancer specimens after radiation therapy. EphA3 mediated the tumor invasiveness and migration in radioresistant head and neck cancer cell lines and epithelial mesenchymal transition- related protein expression. Inhibition of EphA3 enhanced radiosensitivity in the AMC HN 3R cell line in vitro and in vivo study. In conclusion, our results suggest that EphA3 is overexpressed in radioresistant head and neck cancer and plays a crucial role in the development of radioresistance in head and neck cancers by regulating the epithelial mesenchymal transition pathway.

Epha3 acts as proangiogenic factor in multiple myeloma

This study investigates the role of ephrin receptor A3 (EphA3) in the angiogenesis of Multiple Myeloma (MM) and the effects of a selective target of EphA3 by a specific monoclonal antibody on primary bone marrow endothelial cells (ECs) of MM patients.

EphA3 mRNA and protein were evaluated in ECs of MM patients (MMECs), in ECs of patients with monoclonal gammopathies of undetermined significance (MGECs) and in ECs of healthy subjects (control ECs). The effects of EphA3 targeting by mRNA silencing (siRNA) or by the anti EphA3 antibody on the angiogenesis were evaluated. We found that EphA3 is highly expressed in MMECs compared to the other EC types. Loss of function of EphA3 by siRNA significantly inhibited the ability of MMECs to adhere to fibronectin, to migrate and to form tube like structures in vitro, without affecting cell proliferation or viability. In addition, gene expression profiling showed that knockdown of EphA3 down modulated some molecules that regulate adhesion, migration and invasion processes. Interestingly, EphA3 targeting by an anti EphA3 antibody reduced all the MMEC angiogenesis-related functions in vitro. In conclusion, our findings suggest that EphA3 plays an important role in MM angiogenesis.

Characterization of brain tumor initiating cells isolated from an animal model of CNS primitive neuroectodermal tumors

CNS Primitive Neuroectodermal tumors (CNS-PNETs) are members of the embryonal family of malignant childhood brain tumors, which remain refractory to current therapeutic treatments. Current paradigm of brain tumorigenesis implicates brain tumor-initiating cells (BTIC) in the onset of tumorigenesis and tumor maintenance. However, despite their significance, there is currently no comprehensive characterization of CNS-PNETs BTICs. Recently, we described an animal model of CNS-PNET generated by orthotopic transplantation of human Radial Glial (RG) cells - the progenitor cells for adult neural stem cells (NSC) - into NOD-SCID mice brain and proposed that BTICs may play a role in the maintenance of these tumors. Here we report the characterization of BTIC lines derived from this CNS-PNET animal model. BTIC’s orthotopic transplantation generated highly aggressive tumors also characterized as CNS-PNETs. The BTICs have the hallmarks of NSCs as they demonstrate self-renewing capacity and have the ability to differentiate into astrocytes and early migrating neurons. Moreover, the cells demonstrate aberrant accumulation of wild type tumor-suppressor protein p53, indicating its functional inactivation, highly up-regulated levels of onco-protein cMYC and the BTIC marker OCT3/4, along with metabolic switch to glycolysis - suggesting that these changes occurred in the early stages of tumorigenesis. Furthermore, based on RNA- and DNA-seq data, the BTICs did not acquire any transcriptome-changing genomic alterations indicating that the onset of tumorigenesis may be epigenetically driven. The study of these BTIC self-renewing cells in our model may enable uncovering the molecular alterations that are responsible for the onset and maintenance of the malignant PNET phenotype.

EphA8 is a prognostic marker for epithelial ovarian cancer

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

Mouse Cutaneous Melanoma Induced by Mutant BRaf Arises from Expansion and Dedifferentiation of Mature Pigmented Melanocytes

To identify the cells at the origin of melanoma, we combined single-cell lineage-tracing and transcriptomics approaches with time-lapse imaging. A mouse model that recapitulates key histopathological features of human melanomagenesis was created by inducing a BRafV600E-driven melanomagenic program in tail interfollicular melanocytes. Most targeted mature, melanin-producing melanocytes expanded clonally within the epidermis before losing their differentiated features through transcriptional reprogramming and eventually invading the dermis. Tumors did not form within interscales, which contain both mature and dormant amelanotic melanocytes. The hair follicle bulge, which contains melanocyte stem cells, was also refractory to melanomagenesis. These studies identify varying tumor susceptibilities within the melanocytic lineage, highlighting pigment-producing cells as the melanoma cell of origin, and indicate that regional variation in tumor predisposition is dictated by microenvironmental cues rather than intrinsic differences in cellular origin. Critically, this work provides in vivo evidence that differentiated somatic cells can be reprogrammed into cancer initiating cells.

The role of Eph/ephrin molecules in stromal–hematopoietic interactions

Bone marrow mesenchymal stromal/stem cells(BMSC) are fundamental regulatory elements of the hematopoietic stem cell niche; however, the molecular signals that mediate BMSC support of hematopoiesis are poorly understood. Recent studies indicate that BMSC and hematopoietic stem/progenitors cells differentially express the Eph cell surface tyrosine kinase receptors, and their ephrinligands. Eph/ephrin interactions are thought to mediate cross-talk between BMSC and different hematopoietic cell populations to influence cell development, migration and function. This review summarizes Eph/ephrin interactions in the regulation of BMSC communication with hematopoietic stem/progenitor cells and discusses Eph/ephrintargeted therapeutic strategies that are currently being pursued or various hematotological malignancies.

Overexpression of Ephrin A3 Receptor in Canine Prostatic Carcinoma

Ephrin A3 (EphA3), a member of the ephrin receptor tyrosine kinase family, is involved in a variety of functions in normal cells, especially during embryonic development, and alterations in its expression profile have been observed in several human cancers. However, there are no reports of the expression of EphA3 in normal, hyperplastic or neoplastic canine prostate tissue or in other types of canine tumours. Six normal, 15 hyperplastic and 21 neoplastic canine prostates were examined immunohistochemically with a polyclonal antibody specific for human EphA3. The percentage of positive cells in all prostatic carcinomas was increased, with a mean of 89.28 ± 5.18% compared with normal (9.17 ± 6.72%) and hyperplastic prostates (20.00 ± 8.28%). EphA3 expression was not correlated with the histological subtypes of prostate cancer or with the Gleason score. The increase in EphA3 expression in canine prostatic carcinomas suggests the involvement of this receptor in prostatic carcinogenesis and its potential use as a target for new therapeutic strategies.

Unliganded EphA3 dimerization promoted by the SAM domain

The erythropoietin-producing hepatocellular carcinoma A3 (EphA3) receptor tyrosine kinase (RTK) regulates morphogenesis during development and is overexpressed and mutated in a variety of cancers. EphA3 activation is believed to follow a 'seeding mechanism' model, in which ligand binding to the monomeric receptor acts as a trigger for signal-productive receptor clustering. We study EphA3 lateral interactions on the surface of live cells and we demonstrate that EphA3 forms dimers in the absence of ligand binding. We further show that these dimers are stabilized by interactions involving the EphA3 sterile α-motif (SAM) domain. The discovery of unliganded EphA3 dimers challenges the current understanding of the chain of EphA3 activation events and suggests that EphA3 may follow the 'pre-formed dimer' model of activation known to be relevant for other receptor tyrosine kinases. The present work also establishes a new role for the SAM domain in promoting Eph receptor lateral interactions and signalling on the cell surface.

Distinctive Structure of the EphA3/Ephrin-A5 Complex Reveals a Dual Mode of Eph Receptor Interaction for Ephrin-A5

The Eph receptor tyrosine kinase/ephrin ligand system regulates a wide spectrum of physiological processes, while its dysregulation has been implicated in cancer progression. The human EphA3 receptor is widely upregulated in the tumor microenvironment and is highly expressed in some types of cancer cells. Furthermore, EphA3 is among the most highly mutated genes in lung cancer and it is also frequently mutated in other cancers. We report the structure of the ligand-binding domain of the EphA3 receptor in complex with its preferred ligand, ephrin-A5. The structure of the complex reveals a pronounced tilt of the ephrin-A5 ligand compared to its orientation when bound to the EphA2 and EphB2 receptors and similar to its orientation when bound to EphA4. This tilt brings an additional area of ephrin-A5 into contact with regions of EphA3 outside the ephrin-binding pocket thereby enlarging the size of the interface, which is consistent with the high binding affinity of ephrin-A5 for EphA3. This large variation in the tilt of ephrin-A5 bound to different Eph receptors has not been previously observed for other ephrins.