Eph/ephrin profiling in human breast cancer reveals significant associations between expression level and clinical outcome

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.

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.

Identification of therapeutic targets and prognostic biomarkers of the ephrin receptor subfamily in pancreatic adenocarcinoma

OBJECTIVES

We aimed to examine the significance of ephrin receptor A2 (EphA2) expression in pancreatic adenocarcinoma (PAAD) and its associated mechanism.

METHODS

EphA2 mRNA expression patterns were compared in pancreatic cancer and normal tissues using GEPIA. Kaplan-Meier analysis was used to examine the correlation between EphA2 expression and PAAD patient prognosis. EphA2 gene methylation and associations with tumor immune cell infiltration were analyzed with UALCAN and TIMER, respectively. EphA2-interacting proteins were investigated with GeneMANIA, while STRING helped predict potentially relevant signaling pathways. EphA2 protein expression was examined with immunohistochemistry (IHC) in PAAD patient tissues.

RESULTS

EphA2 was highly expressed in pancreatic cancer tissues and associated with pathological stage. PAAD patients with high EphA2 expression had shorter overall survival and disease-free survival times. EphA2 expression levels were significantly and positively associated with CD4+ T cell infiltration. EphA2 can interact with ENFNA1, ACP1, and CDC42. High EphA2 mRNA expression was enriched for regulation of cell size and cell proliferation. IHC assays suggested that pancreatic cancer tissues had higher EphA2 protein levels than normal pancreatic tissues.

CONCLUSIONS

EphA2 is highly expressed in PAAD and closely related to poor patient prognosis, and is therefore a potential biomarker and target for PAAD diagnosis and treatment.

AXL - a new player in resistance to HER2 blockade

HER2 is a driver in solid tumors, mainly breast, oesophageal and gastric cancer, through activation of oncogenic signaling pathways such as PI3K or MAPK. HER2 overexpression associates with aggressive disease and poor prognosis. Despite targeted anti-HER2 therapy has improved outcomes and is the current standard of care, resistance emerge in some patients, requiring additional therapeutic strategies. Several mechanisms, including the upregulation of receptors tyrosine kinases such as AXL, are involved in resistance. AXL signaling leads to cancer cell proliferation, survival, migration, invasion and angiogenesis and correlates with poor prognosis. In addition, AXL overexpression accompanied by a mesenchymal phenotype result in resistance to chemotherapy and targeted therapies. Preclinical studies show that AXL drives anti-HER2 resistance and metastasis through dimerization with HER2 and activation of downstream pathways in breast cancer. Moreover, AXL inhibition restores response to HER2 blockade in vitro and in vivo. Limited data in gastric and oesophageal cancer also support these evidences. Furthermore, AXL shows a strong value as a prognostic and predictive biomarker in HER2+ breast cancer patients, adding a remarkable translational relevance. Therefore, current studies enforce the potential of co-targeting AXL and HER2 to overcome resistance and supports the use of AXL inhibitors in the clinic.

Development of an Anti-EphB4 Monoclonal Antibody for Multiple Applications Against Breast Cancers

The erythropoietin-producing hepatocellular carcinoma (Eph) receptors are the largest receptor tyrosine kinase family. EphB4 is essential for cell adhesion and motility during embryogenesis. Pathologically, EphB4 is overexpressed and contributes to poor prognosis in various tumors. Therefore, specific monoclonal antibodies (mAbs) should be developed to predict the prognosis for multiple tumors with high EphB4 expression, including breast and gastric cancers. This study aimed to develop specific anti-EphB4 mAbs for multiple applications using the Cell-Based Immunization and Screening method. EphB4-overexpressed Chinese hamster ovary (CHO)-K1 (CHO/EphB4) cells were immunized into mice, and we established an anti-EphB4 mAb (clone B4Mab-7), which is applicable for flow cytometry, Western blot, and immunohistochemistry (IHC). B4Mab-7 reacted with endogenous EphB4-positive breast cancer cell line, MCF-7, but did not react with EphB4-knockout MCF-7 (BINDS-52) in flow cytometry. Dissociation constant (KD) values were determined to be 2.9 × 10-9 M and 1.3 × 10-9 M by flow cytometric analysis for CHO/EphB4 and MCF-7 cells, respectively. B4Mab-7 detected the EphB4 protein bands from breast cancer cells in Western blot, and stained breast cancer tissues in IHC. Altogether, B4Mab-7 is very useful for detecting EphB4 in various applications.

EPH/Ephrin Signaling in Normal Hematopoiesis and Hematologic Malignancies: Deciphering Their Intricate Role and Unraveling Possible New Therapeutic Targets

Erythropoietin-producing hepatocellular carcinoma receptors (EPHs) represent the largest family of receptor tyrosine kinases (RTKs). EPH interaction with ephrins, their membrane-bound ligands, holds a pivotal role in embryonic development, while, though less active, it is also implicated in various physiological functions during adult life. In normal hematopoiesis, different patterns of EPH/ephrin expression have been correlated with hematopoietic stem cell (HSC) maintenance and lineage-committed hematopoietic progenitor cell (HPC) differentiation, as well as with the functional properties of their mature offspring. Research in the field of hematologic malignancies has unveiled a rather complex involvement of the EPH/ephrinsignaling pathway in the pathophysiology of these neoplasms. Aberrations in genetic, epigenetic, and protein levels have been identified as possible players implicated both in tumor progression and suppression, while correlations have also been highlighted regarding prognosis and response to treatment. Initial efforts to therapeutically target the EPH/ephrin axis have been undertaken in the setting of hematologic neoplasia but are mainly confined to the preclinical level. To this end, deciphering the complexity of this signaling pathway both in normal and malignant hematopoiesis is necessary.

Novel Isoform DTX3c Associates with UBE2N-UBA1 and Cdc48/p97 as Part of the EphB4 Degradation Complex Regulated by the Autocrine IGF-II/IRA Signal in Malignant Mesothelioma

EphB4 angiogenic kinase over-expression in Mesothelioma cells relies upon a degradation rescue signal provided by autocrine IGF-II activation of Insulin Receptor A. However, the identity of the molecular machinery involved in EphB4 rapid degradation upon IGF-II signal deprivation are unknown. Using targeted proteomics, protein-protein interaction methods, PCR cloning, and 3D modeling approaches, we identified a novel ubiquitin E3 ligase complex recruited by the EphB4 C tail upon autocrine IGF-II signal deprivation. We show this complex to contain a previously unknown N-Terminal isoform of Deltex3 E3-Ub ligase (referred as "DTX3c"), along with UBA1(E1) and UBE2N(E2) ubiquitin ligases and the ATPase/unfoldase Cdc48/p97. Upon autocrine IGF-II neutralization in cultured MSTO211H (a Malignant Mesothelioma cell line that is highly responsive to the EphB4 degradation rescue IGF-II signal), the inter-molecular interactions between these factors were enhanced and their association with the EphB4 C-tail increased consistently with the previously described EphB4 degradation pattern. The ATPase/unfoldase activity of Cdc48/p97 was required for EphB4 recruitment. As compared to the previously known isoforms DTX3a and DTX3b, a 3D modeling analysis of the DTX3c Nt domain showed a unique 3D folding supporting isoform-specific biological function(s). We shed light on the molecular machinery associated with autocrine IGF-II regulation of oncogenic EphB4 kinase expression in a previously characterized IGF-II+/EphB4+ Mesothelioma cell line. The study provides early evidence for DTX3 Ub-E3 ligase involvement beyond the Notch signaling pathway.

Signals transduced by Eph receptors and ephrin ligands converge on MAP kinase and AKT pathways in human cancers

Eph receptors, the largest known family of receptor tyrosine kinases, and ephrin ligands have been implicated in a variety of human cancers. The novel bidirectional signaling events initiated by binding of Eph receptors to their cognate ephrin ligands modulate many cellular processes such as proliferation, metastasis, angiogenesis, invasion, and apoptosis. The relationships between the abundance of a unique subset of Eph receptors and ephrin ligands with associated cellular processes indicate a key role of these molecules in tumorigenesis. The combinatorial expression of these molecules converges on MAP kinase and/or AKT/mTOR signaling pathways. The intracellular target proteins of the initial signal may, however, vary in some cancers. Furthermore, we have also described the commonality of up- and down-regulation of individual receptors and ligands in various cancers. The current state of research in Eph receptors illustrates MAP kinase and mTOR pathways as plausible targets for therapeutic interventions in various cancers.

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.

Expression characteristic, immune signature, and prognosis value of EFNA family identified by multi-omics integrative analysis in pan-cancer

Background

EphrinA (EFNA) are Eph receptor ligands that regulate various disease processes. Nonetheless, the expression characteristics of EFNAs in pan-cancer, their relationship with tumor immune microenvironment, and prognostic value landscape remain unknown.

Methods

A comprehensive landscape of EFNAs was created using various statistical data extracted from 33 cancers. Subsequently, we identified differential expression, genetic variations, potential function enrichment, tumor immune-related analysis, and drug sensitivity. Further, we investigated the clinical features and diagnostic prognostic value of EFNAs. RT-qPCR, western blot and immunohistochemistry (IHC) were used to validate the expression level and significant clinical value of EFNA5 in lung adenocarcinoma cell lines and tissues.

Results

EFNAs were highly mutated in various cancers. Genomic and epigenetic alterations of EFNAs were observed in various tumors, where an oncogenic mutation in specific cancer types potentially affected EFNA expression. Moreover, tumor-derived EFNAs were significantly related to the tumor immune microenvironment, suggesting that they are promising therapeutic targets. The majority of EFNA family genes were significantly linked to patient prognosis. Eventually, EFNA5 was an independent prognostic factor in lung adenocarcinoma.

Conclusion

In summary, EFNAs are crucial in tumor immune regulation, and EFNA5 is a prognostic marker in lung adenocarcinoma. Our findings provide new insights into EFNAs from a bioinformatics standpoint and highlight the significance of EFNAs in cancer diagnosis and treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09951-0.

The role of EphA7 in different tumors

Ephrin receptor A7 (EphA7) is a member of the Eph receptor family. It is widely involved in signal transduction between cells, regulates cell proliferation and differentiation, and participates in developing neural tubes and brain. In addition, EphA7 also has a dual role of tumor promoter and tumor suppressor. It can participate in cell proliferation, migration and apoptosis through various mechanisms, and affect tumor differentiation, staging and prognosis. EphA7 may be a potential diagnostic marker and tumor treatment target. This article reviews the effects of EphA7 on a variety of tumor biological processes and pathological characteristics, as well as specific effects and regulatory mechanisms.

EPHA2, EPHA4, and EPHA7 Expression in Triple-Negative Breast Cancer

Ongoing research continues to elucidate the complex role of ephrin receptors (EPHs) and their ligands (ephrins) in breast cancer pathogenesis, with their varying expression patterns implied to have an important impact on patients’ outcome. The current study aims to investigate the clinical significance of EPHA2, EPHA4, and EPHA7 expression in triple-negative breast cancer (TNBC) cases. EPHA2, EPHA4, and EPHA7 protein expression was assessed immunohistochemically on formalin-fixed and paraffin-embedded (FFPE) TNBC tissue sections from 52 TNBC patients and correlated with key clinicopathologic parameters and patients’ survival data (overall survival (OS); disease-free survival (DFS)). EPHA2, EPHA4, and EPHA7 expression was further examined in TNBC cell lines. EPHA2 overexpression was observed in 26 (50%) of the TNBC cases, who exhibited a shorter OS and DFS than their low-expression counterparts, with EPHA2 representing an independent prognostic factor for OS and DFS (p = 0.0041 and p = 0.0232, respectively). EPHA4 overexpression was associated with lymph node metastasis in TNBC patients (p = 0.0546). Alterations in EPHA2, EPHA4, and EPHA7 expression levels were also noted in the examined TNBC cell lines. Our study stresses that EPHA2 expression constitutes a potential prognostic factor for TNBC patients. Given the limited treatment options and poorer outcome that accompany the TNBC subtype, EPHA2 could also pose as a target for novel, more personalized, and effective therapeutic approaches for those patients.

Clinical genomic profiling to identify actionable alterations for very early relapsed triple-negative breast cancer patients in the Chinese population

BACKGROUND

Triple-negative breast cancer (TNBC) represents about 19% of all breast cancer cases in the Chinese population. Lack of targeted therapy contributes to the poorer outcomes compared with other breast cancer subtypes. Comprehensive genomic profiling helps to explore the clinically relevant genomic alterations (CRGAs) and potential therapeutic targets in very-early-relapsed TNBC patients.

METHODS

Formalin-fixed paraffin-embedded (FFPE) tumour tissue specimens from 23 patients with very-early-relapsed TNBC and 13 patients with disease-free survival (DFS) more than 36 months were tested by FoundationOne CDx (F1CDx) in 324 genes and select gene rearrangements, along with genomic signatures including microsatellite instability (MSI) and tumour mutational burden (TMB).

RESULTS

In total, 137 CRGAs were detected in the 23 very-early-relapsed TNBC patients, averaging six alterations per sample. The mean TMB was 4 Muts/Mb, which was higher than that in non-recurrence patients, and is statistically significant. The top-ranked altered genes were TP53 (83%), PTEN (35%), RB1 (30%), PIK3CA (26%) and BRCA1 (22%). RB1 mutation carriers had shorter DFS. Notably, 100% of these patients had at least one CRGA, and 87% of patients had at least one actionable alteration. In pathway analysis, patients who carried a mutation in the cell cycle pathway were more likely to experience very early recurrence. Strikingly, we detected one patient with ERBB2 amplification and one patient with ERBB2 exon20 insertion, both of which were missed by immunohistochemistry (IHC). We also detected novel alterations of ROS1-EPHA7 fusion for the first time, which has not been reported in breast cancer before.

CONCLUSIONS

The comprehensive genomic profiling can identify novel treatment targets and address the limited options in TNBC patients. Therefore, incorporating F1CDx into TNBC may shed light on novel therapeutic opportunities for these very-early-relapsed TNBC patients.

Potential entry receptors for human γ-herpesvirus into epithelial cells: A plausible therapeutic target for viral infections

Herpesviruses are ubiquitous viruses, specifically the Epstein Barr virus (EBV). EBV and Kaposi's sarcoma-associated herpesvirus (KSHV) establish their latency for a long period in B-cells and their reactivation instigates dreadful diseases from cancer to neurological modalities. The envelope glycoprotein of these viruses makes an attachment with several host receptors. For instance; glycoprotein 350/220, gp42, gHgL and gB of EBV establish an attachment with CD21, HLA-DR, Ephs, and other receptor molecules to hijack the B- and epithelial cell machinery. Ephs are reported recently as potent receptors for EBV entry into epithelial cells. Eph receptors play a role in the maintenance and control of various cellular processes including morphology, adhesion, proliferation, survival and differentiation. Alterations in the structure and expression of Eph and ephrin (Eph ligands) molecules is entangled with various pathologies including tumours and neurological complications. Along with Eph, integrins, NRP, NMHC are also key players in viral infections as they are possibly involved in viral transmission, replication and persistence. Contrarily, KSHV gH is known to interact with EphA2 and -A4 molecules, whereas in the case of EBV only EphA2 receptors are being reported to date. The ELEFN region of KSHV gH was involved in the interaction with EphA2, however, the interacting region of EBV gH is elusive. Further, the gHgL of KSHV and EBV form a complex with the EphA2 ligand-binding domain (LBD). Primarily by using gL both KSHV and EBV gHgL bind to the peripheral regions of LBD. In addition to γ-herpesviruses, several other viruses like Nipah virus, Cedar virus, Hepatitis C virus and Rhesus macaque rhadinovirus (RRV) also access the host cells via Eph receptors. Therefore, we summarise the possible roles of Eph and ephrins in virus-mediated infection and these molecules could serve as potential therapeutic targets.

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Crucial understanding of human γ-herpesviruses entry mechanism.

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Eph receptors relate to changed biomolecular profile upon EBV infection.

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EBV association with neurological disorders.

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Eph receptors could be an elegant drug for human γ-herpesviruses.

The Clinical Impact of the EPH/Ephrin System in Cancer: Unwinding the Thread

Erythropoietin-producing human hepatocellular receptors (EPHs) compose the largest known subfamily of receptor tyrosine kinases (RTKs). They bind and interact with the EPH family receptor interacting proteins (ephrins). EPHs/ephrins are implicated in a variety of physiological processes, as well as in cancer pathogenesis. With neoplastic disease remaining a leading cause of death world-wide, the development of novel biomarkers aiding in the field of diagnosis, prognosis, and disease monitoring is of utmost importance. A multitude of studies have proven the association between the expression of members of the EPH/ephrin system and various clinicopathological parameters, including disease stage, tumor histologic grade, and patients' overall survival. Besides their utilization in timely disease detection and assessment of outcome, EPHs/ephrins could also represent possible novel therapeutic targets. The aim of the current review of the literature was to present the existing data regarding the association between EPH/ephrin system expression and the clinical characteristics of malignant tumors.

Low Expression of EphB2, EphB3, and EphB4 in Bladder Cancer: Novel Potential Indicators of Muscular Invasion

PURPOSE

Eph receptors are differentially expressed in numerous malignant tumors. This study intended to analyze the roles of EphB receptors (EphB2, B3, and B4) in urinary bladder cancer.

MATERIALS AND METHODS

Tissue microarray-based immunohistochemical analysis was used to investigate the expression patterns of EphB2, EphB3, and EphB4 in 154 bladder cancer specimens. Immunohistochemical staining was conducted examining the extent of stained cells and staining intensity. EphB was considered to be highly expressed when the intensity of staining was more than moderate in >25% of cells in the tissue section. Small interfering RNA (siRNA) was used to knock down EphB expression in bladder cancer cell lines (T24, 5637) to determine the effects of EphB on tumor cell invasion, proliferation, and migration.

RESULTS

EphB receptors (B2, B3, and B4) were detected in 40.9% (EphB2, 63/154), 71.4% (EphB3, 110/154), and 53.2% (EphB4, 82/154) of bladder cancer specimens. Low expression of EphB2, B3, and B4 receptors were significantly associated with higher tumor grade (EphB2, p<0.001; EphB3, p=0.032; EphB4, p<0.001) and muscular invasion (EphB2, p=0.002; EphB3, p=0.009; EphB4, p<0.001). No obvious correlation was observed with other clinicopathological variables, such as age, sex, recurrence, lymph node involvement, metastasis, and overall survival. Inactivation of EphB receptors by siRNA transfection increased cell viability, tumor cell invasion, proliferation, and migration in comparison with untransfected cancer cells.

CONCLUSION

Low expression of EphB receptors (B2, B3, and B4) can be a predictive marker for muscular invasion of bladder cancer.

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

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

Expression Pattern and Prognostic Value of EPHA/EFNA in Breast Cancer by Bioinformatics Analysis: Revealing Its Importance in Chemotherapy

The activities of the ephrin family in breast cancer (BrCa) are complex. Family A receptors (EPHA) and ligands (EFNA) can act as oncogenes or tumor suppressors and are implicated in chemoresistance. Here, we examined the expression pattern and prognostic value of the EPHA/EFNA family in patients with breast cancer, including patients with different subtypes or different chemotherapy cohorts. In the UALCAN database, the mRNA expression of EPHA1, EPHA10, EFNA1, EFNA3, and EFNA4 was significantly higher, whereas that of EPHA2, EPHA4, EPHA5, and EFNA5 was significantly lower in breast cancer tissues than in paracancerous tissues. The transcriptional levels of EPHA/EFNA family members were correlated with intrinsic subclasses of breast cancer. The relationship between EPHA/EFNA and the clinicopathological parameters of BrCa was analyzed using bc-GenExMiner V4.5. EPHA1, EPHA2, EPHA4, EPHA7, EFNA3, EFNA4, and EFNA5 were upregulated in estrogen receptor- (ER-) and progesterone receptor- (PR-) negative tumors, whereas EPHA3, EPHA6, and EFNA1 were upregulated in ER- and PR-positive tumors. EPHA1, EPHA2, EFNA3, and EFNA4 mRNA expression was significantly higher in human epidermal growth factor receptor 2- (HER2-) positive tumors than in HER2-negative tumors. Triple-negative status was positively correlated with EPHA1, EPHA2, EPHA4, EPHA7, EFNA3, EFNA4, and EFNA5 and negatively correlated with EPHA3 and EPHA10 mRNA expression. Genetic alterations of EPHA/EFNA in breast cancer varied from 1.1% to 10% for individual genes, as determined by the cBioPortal database. The Kaplan–Meier plotter indicated that high EphA7 mRNA expression was associated with poor overall survival (OS) and recurrence-free survival (RFS), especially in the HER2 and luminal A subtypes. EFNA4 was predicted to have poor OS and RFS in breast cancers, especially in luminal B, basal-like subtype, and patients treated with adjuvant chemotherapy. High EPHA3 expression was significantly associated with better OS and RFS, especially in the luminal A subtype, but with poor RFS in BrCa patients receiving chemotherapy. Our findings systematically elucidate the expression pattern and prognostic value of the EPHA/EFNA family in BrCa, which might provide potential prognostic factors and novel targets in BrCa patients, including those with different subtypes or treated with chemotherapy.

EphA2 as a new target for breast cancer and its potential clinical application

PURPOSE

The aim of this research was to study the expression of EphA2 to assess its suitability as a new breast cancer target.

METHODS

Immunohistochemistry (IHC) was used to detect EphA2 protein expression in pathology tissue samples from 250 cases of breast cancer, and the expression of EphA2 mRNA was detected by in situ hybridization (ISH). Breast cancer cells were isolated and cultured. The expression of EphA2 in the cells was detected by the indirect immunofluorescence assay (IFA), and the expression of EphA2 in breast cancer was analysed.

RESULTS

EphA2 protein and mRNA were mainly expressed in tumor cells and vascular endothelial cells. EphA2 protein was expressed in 187 cases, with a positive rate of 74.80%, whereas EphA2 mRNA was expressed in 209 cases, with a positive rate of 83.60%. EphA2 protein and mRNA expression were correlated with lymph node metastasis, clinical stage, and breast cancer histologic grade (P<0.05). In addition, the positive expression rates of EphA2 protein and EphA2 mRNA were correlated (P<0.05). EphA2 was barely expressed in normal breast cells but highly expressed in breast cancer cells.

CONCLUSION

EphA2 is highly expressed in breast cancer tissues and has the potential to be a new breast cancer target, providing a preliminary basis for the development of new targeted drugs for breast cancer and the construction of fluorescent-targeted tracers for fluorescence-guided mastoscopic breast-conserving surgery.

Oncogenic functions and therapeutic targeting of EphA2 in cancer

More than 25 years of research and preclinical validation have defined EphA2 receptor tyrosine kinase as a promising molecular target for clinical translation in cancer treatment. Molecular, genetic, biochemical, and pharmacological targeting strategies have been extensively tested in vitro and in vivo, and drugs like dasatinib, initially designed to target SRC family kinases, have been found to also target EphA2 activity. Other small molecules, therapeutic targeting antibodies, and peptide-drug conjugates are being tested, and more recently, approaches harnessing antitumor immunity against EphA2-expressing cancer cells have emerged as a promising strategy. This review will summarize preclinical studies supporting the oncogenic role of EphA2 in breast cancer, lung cancer, glioblastoma, and melanoma, while delineating the differing roles of canonical and noncanonical EphA2 signaling in each setting. This review also summarizes completed and ongoing clinical trials, highlighting the promise and challenges of targeting EphA2 in cancer.

EphA2 Is a Clinically Relevant Target for Breast Cancer Bone Metastatic Disease

EphA2 receptor tyrosine kinase (RTK) is highly expressed in breast tumor cells across multiple molecular subtypes and correlates with poor patient prognosis. In this study, the potential role of EphA2 in this clinically relevant phenomenon is investigated as metastasis of breast cancer to bone is a major cause of morbidity and mortality in patients. It was found that the EphA2 function in breast cancer cells promotes osteoclast activation and the development of osteolytic bone disease. Blocking EphA2 function molecularly and pharmacologically in breast tumors reduced the number and size of bone lesions and the degree of osteolytic disease in intratibial and intracardiac mouse models, which correlated with a significant decrease in the number of osteoclasts at the tumor-bone interface. EphA2 loss of function in tumor cells impaired osteoclast progenitor differentiation in coculture, which is mediated, at least in part, by reduced expression of IL-6. EPHA2 transcript levels are enriched in human breast cancer bone metastatic lesions relative to visceral metastatic sites; EphA2 protein expression was detected in breast tumor cells in bone metastases in patient samples, supporting the clinical relevance of the study's findings. These data provide a strong rationale for the development and application of molecularly targeted therapies against EphA2 for the treatment of breast cancer bone metastatic disease. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

EphA2: A promising therapeutic target in breast cancer

Ephrin type-A receptor 2 (EphA2), a receptor tyrosine kinase, is overexpressed in human breast cancers often linked to poor patient prognosis. Accumulating evidence demonstrates that EphA2 plays important roles in several critical processes associated with malignant breast progression, such as proliferation, survival, migration, invasion, drug resistance, metastasis, and angiogenesis. As its inhibition through multiple approaches can inhibit the growth of breast cancer and restore drug sensitivity, EphA2 has become a promising therapeutic target for breast cancer treatment. Here, we summarize the expression, functions, mechanisms of action, and regulation of EphA2 in breast cancer. We also list the potential therapeutic strategies targeting EphA2. Furthermore, we discuss the future directions of studying EphA2 in breast cancer.

CpG Islands Methylation Analysis of CDH11, EphA5, and HS3ST2 Genes in Gastric Adenocarcinoma Patients

PURPOSE

Gastric cancer is an aggressive disease which is the fourth prevalent malignancy in the world. Beside the genetic factors, epigenetic alterations such as promoter CpG island hyper methylation are involved in the emergence of gastric cancer. Herein, we investigated the methylation status of CDH11, EphA5, and HS3ST2 genes in patients with and without gastric adenocarcinoma for the first time.

METHODS

In the study 40 paraffin-embedded tissue sections from gastric adenocarcinoma patients and 40 specimens from patients with functional dyspepsia were taken. DNA extraction was performed using a modified salting out method. Epizen DNA methylation kit was used to the bisulfite DNA conversion. The methylation status of CDH11, EphA5, and HS3ST2 genes were analyzed by methylation-specific PCR (MSP) technique.

RESULTS

Among the 80 specimens, 71 DNA samples were achieved (34 gastric adenocarcinoma patients and 37 control patients). The results showed that CDH11, EphA5, and HS3ST2 genes are methylated in 28 (82.45%), 19 (55.88%), and 26 (76.47%) of 34 DNA samples from gastric adenocarcinoma patients, respectively, whereas, these genes are methylated in 7 (18.91%), 9 (24.32%) and 7 (18.91%) of 37 samples from noncancerous patients, respectively. Statistical analyses using a chi-squared test showed that there is a statistically significant difference in methylation level of CDH11, EphA5, and HS3ST2 genes between gastric cancer and uncancerous patients (p < 0.05).

CONCLUSION

To the best of our knowledge, this is the first report on methylation of CDH11, EphA5, and HS3ST2 promoters' in gastric adenocarcinoma patients using MSP. Identification of novel cancer-related molecular mechanisms can be useful in detection of new treatment strategies.

The Role of the Eph Receptor Family in Tumorigenesis

Simple Summary

The Eph receptor family is implicated in both tumour promotion and suppression, depending on the tissue-specific context of available receptor interactions with ligands, adaptor proteins and triggered downstream signalling pathways. This complex interplay has not only consequences for tumorigenesis but also offers a basis from which new cancer-targeting strategies can be developed. This review comprehensively summarises the current knowledge of Eph receptor implications in oncogenesis in a tissue- and receptor-specific manner, with the aim to develop a better understanding of Eph signalling pathways for potential targeting in novel cancer therapies.

Abstract

The Eph receptor tyrosine kinase family, activated by binding to their cognate ephrin ligands, are important components of signalling pathways involved in animal development. More recently, they have received significant interest due to their involvement in oncogenesis. In most cases, their expression is altered, affecting the likes of cell proliferation and migration. Depending on the context, Eph receptors have the potential to act as both tumour promoters and suppressors in a number of cancers, such as breast cancer, colorectal cancer, lung cancer, prostate cancer, brain cancer and Kaposi’s sarcoma (KS), the latter being intrinsically linked to EphA2 as this is the receptor used for endothelial cell entry by the Kaposi’s sarcoma-associated herpesvirus (KSHV). In addition, EphA2 deregulation is associated with KS, indicating that it has a dual role in this case. Associations between EphA2 sequence variation and KSHV infection/KS progression have been detected, but further work is required to formally establish the links between EphA2 signalling and KS oncogenesis. This review consolidates the available literature of the role of the Eph receptor family, and particularly EphA2, in tumorigenesis, with the aim to develop a better understanding of Eph signalling pathways for potential targeting in novel cancer therapies.

Kinome scale profiling of venom effects on cancer cells reveals potential new venom activities

The search for novel and relevant cancer therapeutics is continuous and ongoing. Cancer adaptations, resulting in therapeutic treatment failures, fuel this continuous necessity for new drugs to novel targets. Recently, researchers have started to investigate the effect of venoms and venom components on different types of cancer, investigating their mechanisms of action. Receptor tyrosine kinases (RTKs) comprise a family of highly conserved and functionally important druggable targets for cancer therapy. This research exploits the novelty of complex venom mixtures to affect phosphorylation of the epidermal growth factor receptor (EGFR) and related RTK family members, dually identifying new activities and unexplored avenues for future cancer and venom research. Six whole venoms from diverse species taxa, were evaluated for their ability to illicit changes in the phosphorylated expression of a panel of 49 commonly expressed RTKs. The triple negative breast cancer cell line MDA-MB-468 was treated with optimised venom doses, pre-determined by SDS PAGE and Western blot analysis. The phosphorylated expression levels of 49 RTKs in response to the venoms were assessed with the use of Human Phospho-RTK Arrays and analysed using ImageLab 5.2.1 analysis software (BioRad). Inhibition of EGFR phosphorylation occurred with treatment of venom from Acanthoscurria geniculata (Theraphosidae), Heterometrus swammerdami (Scorpionidae), Crotalus durissus vegrandis (Crotalidae) and Naja naja (Elapidae). Western green mamba Dendroaspis viridis venom increased EGFR phosphorylation. Eph, HGFR and HER were the most affected receptor families by venoms. Whilst the importance of these changes in terms of effect on MDA-MB-468 cells' long-term viability and functionality are still unclear, the findings present exciting opportunities for further investigation as potential drug targets in cancer and as tools to understand better how these pathways interact.

EPHA2 antisense RNA modulates EPHA2 mRNA levels in basal-like/triple-negative breast cancer cells

Ephrin type-A receptor 2 (EPHA2) is a receptor tyrosine kinase (RTK), whose over-expression has been observed in a variety of cancers, including breast cancer. EPHA2 expression may be causally related to tumorigenesis; therefore, it is important to understand how EPHA2 gene (EPHA2) expression is regulated. Here, we report that EPHA2 antisense RNA (EPHA2-AS), a natural antisense transcript, is an important modulator of EPHA2 mRNA levels. EPHA2-AS is a ∼1.8 kb long non-coding RNA (lncRNA) with a poly(A) tail that encodes two splice variants, EPHA2-AS1/2. They are constitutively expressed in a concordant manner with EPHA2 mRNA in human breast adenocarcinoma cell lines and in patient samples, with the highest levels detected in the triple-negative breast cancer (TNBC) subtype. The silencing of EPHA2-AS1/2 by a sense oligonucleotide or over-expression of an antisense oligoribonucleotide, which were both designed from the EPHA2 mRNA region (nt 2955-2974) targeted by AS1/2, showed that EPHA2-AS1/2 modulated EPHA2 mRNA levels by interacting with the specific AS1/2-complementary region in the mRNA. The EPHA2-AS1/2 did not prevent microRNAs from acting on the relevant microRNA response elements shared by EPHA2-AS1/2 and EPHA2 mRNA. Our studies demonstrate a crucial role played by EPHA2-AS1/2 in modulating EPHA2 mRNA levels, and hence production of EPHA2 protein, a key oncogenic RTK that contributes to the tumorigenesis of TNBC 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.

PDCD10-Deficiency Promotes Malignant Behaviors and Tumor Growth via Triggering EphB4 Kinase Activity in Glioblastoma

We previously reported an angiogenic and tumor-suppressor-like function of programmed cell death 10 (PDCD10) in glioblastoma (GBM). However, the underlying mechanism remains to be elucidated. We hypothesized that loss of PDCD10 activates GBM cells and tumor progression via EphB4. To this end, PDCD10 was knocked down in U87 and T98g by lentiviral mediated shRNA transduction (shPDCD10). GBM cell phenotype in vitro and tumor growth in a mouse xenograft model were investigated in presence or absence of the treatment with a specific EphB4 kinase inhibitor NVP-BHG712 (NVP). We demonstrated that knockdown of PDCD10 in GBM cells significantly upregulated the mRNA and protein expression of EphB4 accompanied by the activation of Erk1/2. EphB4 kinase activity, reflected by phospho-EphB4, significantly increased in shPDCD10 GBM cells, and in tumors derived from shPDCD10 GBM xenografts, which was abolished by the treatment with NVP. Furthermore, NVP treatment significantly suppressed PDCD10-knockdown mediated aggressive GBM cell phenotype in vitro and extensive tumor cell proliferation, the tumor neo-angiogenesis, and a quick progression of tumor formation in vivo. In summary, loss of PDCD10 activates GBM cells and promotes tumor growth via triggering EphB4. Targeting EphB4 might be an effective strategy particularly for the personalized therapy in GBM patients with PDCD10-deficiency.

Evaluation of EphB4 as Target for Image-Guided Surgery of Breast Cancer

Background: Targeted image-guided surgery is based on the detection of tumor cells after administration of a radio-active or fluorescent tracer. Hence, enhanced binding of a tracer to tumor tissue compared to healthy tissue is crucial. Various tumor antigens have been evaluated as possible targets for image-guided surgery of breast cancer, with mixed results. Methods: In this study we have evaluated tyrosine kinase receptor EphB4, a member from the Eph tyrosine kinase receptor family, as a possible target for image-guided surgery of breast cancers. Two independent tissue micro arrays, consisting of matched sets of tumor and normal breast tissue, were stained for EphB4 by immunohistochemistry. The intensity of staining and the percentage of stained cells were scored by two independent investigators. Results: Immunohistochemical staining for EphB4 shows that breast cancer cells display enhanced membranous expression compared to adjacent normal breast tissue. The enhanced tumor staining is not associated with clinical variables like age of the patient or stage or subtype of the tumor, including Her2-status. Conclusion: These data suggest that EphB4 is a promising candidate for targeted image-guided surgery of breast cancer, especially for Her2 negative cases.

Eph receptors: the bridge linking host and virus

Eph (erythropoietin-producing hepatoma) receptors and Ephrin ligands constitute the largest subfamily of receptor tyrosine kinase (RTK), which were first discovered in tumors. Heretofore, Eph protein has been shown to be involved in various tumor biological behaviors including proliferation and progression. The occurrence of specific types of tumor is closely related to the virus infection. Virus entry is a complex process characterized by a series of events. The entry into target cells is an essential step for virus to cause diseases, which requires the fusion of the viral envelope and host cellular membrane mediated by viral glycoproteins and cellular receptors. Integrin molecules are well known as entry receptors for most herpes viruses. However, in recent years, Eph receptors and their Ephrin ligands have been reported to be involved in virus infections. The main mechanism may be the interaction between Eph receptors and conserved viral surface glycoprotein, such as the gH/gL or gB protein of the herpesviridae. This review focuses on the relationship between Eph receptor family and virus infection that summarize the processes of viruses such as EBV, KSHV, HCV, RRV, etc., infecting target cells through Eph receptors and activating its downstream signaling pathways resulting in malignancies. Finally, we discussed the perspectives to block virus infection, prevention, and treatment of viral-related tumors via Eph receptor family.

Progranulin/EphA2 axis: A novel oncogenic mechanism in bladder cancer

The growth factor progranulin plays a critical role in bladder cancer by modulating tumor cell motility and invasion. Progranulin regulates remodeling of the actin cytoskeleton by interacting with drebrin, an actin binding protein that regulates tumor growth. We previously discovered that progranulin depletion inhibits epithelial-to-mesenchymal transition and markedly reduces in vivo tumor growth. Moreover, progranulin depletion sensitizes urothelial cancer cells to cisplatin treatment, further substantiating a pro-survival function of progranulin. Until recently, the progranulin signaling receptor remained unidentified, precluding a full understanding of progranulin action in tumor cell biology. We recently identified EphA2, a member of a large family of receptor tyrosine-kinases, as the functional receptor for progranulin. However, it is not established whether EphA2 plays an oncogenic role in bladder cancer. Here we demonstrate that progranulin, and not ephrin-A1, the canonical ligand for EphA2, is the predominant EphA2 ligand in bladder cancer. Progranulin evoked Akt- and Erk1/2-mediated EphA2 phosphorylation at Ser897, which could drive bladder tumorigenesis. We discovered that EphA2 depletion severely blunted progranulin-dependent motility and anchorage-independent growth, and sensitized bladder cancer cells to cisplatin treatment. We further defined the mechanisms of progranulin/EphA2-dependent motility by identifying liprin-α1 as a novel progranulin-dependent EphA2 interacting protein and establishing its critical role in cell motility. The discovery of EphA2 as the functional signaling receptor for progranulin and the identification of novel downstream effectors offer a new avenue for understanding the underlying mechanism of progranulin action and may constitute novel clinical and therapeutic targets in bladder cancer.

The prognostic value of ephrin type-A2 receptor and Ki-67 in renal cell carcinoma patients: An Immunohistochemical and Bioinformatical Approach; A STROBE - compliant article

Patients with renal cell carcinoma (RCC), the most common malignant renal epithelial tumor, usually present with advanced disease and unpredicted clinical behavior. The receptor tyrosine kinase, ephrin type-A receptor 2 (EphA2) was found to be overexpressed in several malignancies and its expression was found to be associated with poor prognostic features.Our study is an observational study with the aim of investigating the prognostic value of EphA2 in RCC patients and its association with clinicopathological parameters as well as Ki-67 expression, which is a well-known proliferative and prognostic marker in RCC.EphA2 and Ki-67 immunohistochemical staining was performed on whole sections representative of 50 patients diagnosed with primary RCC from 2013 to 2018. In addition, the association between EphA2 mRNA expression and clinicopathological parameters as well as the patients' outcome was also evaluated using two large publicly available databases.Our results showed a significant association between EphA2 immunohistochemical expression and tumor size, nuclear grade, tumor stage, patients' outcome and Ki-67 expression (P < .05 for all). The same trend was also observed with EphA2 mRNA expression using larger patients' cohorts in 2 publicly available databases. Notably, EphA2 protein expression showed higher levels of co-expression with the proliferative marker Ki-67.Our results suggested that higher expression of EphA2 and Ki-67 in tumor tissues predicts a locally aggressive behaviour and poor outcome of patients with RCC. Moreover, our results give a rationale for the potential benefits of using novel therapeutic strategies with the aim of targeting EphA2 receptor in RCC patients that might help in improving their outcome.

Tumor microenvironment complexity and therapeutic implications at a glance

The dynamic interactions of cancer cells with their microenvironment consisting of stromal cells (cellular part) and extracellular matrix (ECM) components (non-cellular) is essential to stimulate the heterogeneity of cancer cell, clonal evolution and to increase the multidrug resistance ending in cancer cell progression and metastasis. The reciprocal cell-cell/ECM interaction and tumor cell hijacking of non-malignant cells force stromal cells to lose their function and acquire new phenotypes that promote development and invasion of tumor cells. Understanding the underlying cellular and molecular mechanisms governing these interactions can be used as a novel strategy to indirectly disrupt cancer cell interplay and contribute to the development of efficient and safe therapeutic strategies to fight cancer. Furthermore, the tumor-derived circulating materials can also be used as cancer diagnostic tools to precisely predict and monitor the outcome of therapy. This review evaluates such potentials in various advanced cancer models, with a focus on 3D systems as well as lab-on-chip devices. Video abstract.

Host deficiency in ephrin-A1 inhibits breast cancer metastasis

Background: The conventional dogma of treating cancer by focusing on the elimination of tumor cells has been recently refined to include consideration of the tumor microenvironment, which includes host stromal cells. Ephrin-A1, a cell surface protein involved in adhesion and migration, has been shown to be tumor suppressive in the context of the cancer cell. However, its role in the host has not been fully investigated. Here, we examine how ephrin-A1 host deficiency affects cancer growth and metastasis in a murine model of breast cancer.

Methods: 4T1 cells were orthotopically implanted into the mammary fat pads or injected into the tail veins of ephrin-A1 wild-type ( Efna1^+/+), heterozygous ( Efna1^+/-), or knockout ( Efna1^-/-) mice. Tumor growth, lung metastasis, and tumor recurrence after surgical resection were measured. Flow cytometry and immunohistochemistry (IHC) were used to analyze various cell populations in primary tumors and tumor-bearing lungs.

Results: While primary tumor growth did not differ between Efna1^+/+, Efna1^+/-, and Efna1^-/- mice, lung metastasis and primary tumor recurrence were significantly decreased in knockout mice. Efna1^-/- mice had reduced lung colonization of 4T1 cells compared to Efna1^+/+ littermate controls as early as 24 hours after tail vein injection. Furthermore, established lung lesions in Efna1^-/- mice had reduced proliferation compared to those in Efna1^+/+ controls.

Conclusions: Our studies demonstrate that host deficiency of ephrin-A1 does not impact primary tumor growth but does affect metastasis by providing a less favorable metastatic niche for cancer cell colonization and growth. Elucidating the mechanisms by which host ephrin-A1 impacts cancer relapse and metastasis may shed new light on novel therapeutic strategies.

Host deficiency in ephrin-A1 inhibits breast cancer metastasis

Background: The conventional dogma of treating cancer by focusing on the elimination of tumor cells has been recently refined to include consideration of the tumor microenvironment, which includes host stromal cells. Ephrin-A1, a cell surface protein involved in adhesion and migration, has been shown to be tumor suppressive in the context of the cancer cell. However, its role in the host has not been fully investigated. Here, we examine how ephrin-A1 host deficiency affects cancer growth and metastasis in a murine model of breast cancer. Methods: 4T1 cells were orthotopically implanted into the mammary fat pads or injected into the tail veins of ephrin-A1 wild-type ( Efna1 ^+/+), heterozygous ( Efna1 ^+/-), or knockout ( Efna1 ^-/-) mice. Tumor growth, lung metastasis, and tumor recurrence after surgical resection were measured. Flow cytometry and immunohistochemistry (IHC) were used to analyze various cell populations in primary tumors and tumor-bearing lungs. Results: While primary tumor growth did not differ between Efna1 ^+/+, Efna1 ^+/-, and Efna1 ^-/- mice, lung metastasis and primary tumor recurrence were significantly decreased in knockout mice. Efna1 ^-/- mice had reduced lung colonization of 4T1 cells compared to Efna1 ^+/+ littermate controls as early as 24 hours after tail vein injection. Furthermore, established lung lesions in Efna1 ^-/- mice had reduced proliferation compared to those in Efna1 ^+/+ controls. Conclusions: Our studies demonstrate that host deficiency of ephrin-A1 does not impact primary tumor growth but does affect metastasis by providing a less favorable metastatic niche for cancer cell colonization and growth. Elucidating the mechanisms by which host ephrin-A1 impacts cancer relapse and metastasis may shed new light on novel therapeutic strategies.

An Overview of Vasculogenic Mimicry in Breast Cancer

Vasculogenic mimicry (VM) is the formation of vascular channels lacking endothelial cells. These channels are lined by tumor cells with cancer stem cell features, positive for periodic acid-Schiff, and negative for CD31 staining. The term VM was introduced by Maniotis et al. (1), who reported this phenomenon in highly aggressive uveal melanomas; since then, VM has been associated with poor prognosis, tumor aggressiveness, metastasis, and drug resistance in several tumors, including breast cancer. It is proposed that VM and angiogenesis (the de novo formation of blood vessels from the established vasculature by endothelial cells, which is observed in several tumors) rely on some common mechanisms. Furthermore, it is also suggested that VM could constitute a means to circumvent anti-angiogenic treatment in cancer. Therefore, it is important to determinant the factors that dictate the onset of VM. In this review, we describe the current understanding of VM formation in breast cancer, including specific signaling pathways, and cancer stem cells. In addition, we discuss the clinical significance of VM in prognosis and new opportunities of VM as a target for breast cancer therapy.

The IGF-II-Insulin Receptor Isoform-A Autocrine Signal in Cancer: Actionable Perspectives

Insulin receptor overexpression is a common event in human cancer. Its overexpression is associated with a relative increase in the expression of its isoform A (IR^A), a shorter variant lacking 11 aa in the extracellular domain, conferring high affinity for the binding of IGF-II along with added intracellular signaling specificity for this ligand. Since IGF-II is secreted by the vast majority of malignant solid cancers, where it establishes autocrine stimuli, the co-expression of IGF-II and IR^A in cancer provides specific advantages such as apoptosis escape, growth, and proliferation to those cancers bearing such a co-expression pattern. However, little is known about the exact role of this autocrine ligand–receptor system in sustaining cancer malignant features such as angiogenesis, invasion, and metastasis. The recent finding that the overexpression of angiogenic receptor kinase EphB4 along with VEGF-A is tightly dependent on the IGF-II/IR^A autocrine system independently of IGFIR provided new perspectives for all malignant IGF2omas (those aggressive solid cancers secreting IGF-II). The present review provides an updated view of the IGF system in cancer, focusing on the biology of the autocrine IGF-II/IR^A ligand–receptor axis and supporting its underscored role as a malignant-switch checkpoint target.

Phosphorylation of EphA2 receptor and vasculogenic mimicry is an indicator of poor prognosis in invasive carcinoma of the breast

PURPOSE

The occurrence of vasculogenic mimicry (VM) and EphA2-mediated tumour progression are associated with poor prognosis in various solid tumours. Here, we aimed to investigate the prognostic implications of VM and its association with phosphorylated EphA2 receptor in invasive carcinoma of the breast.

METHODS

The patients were stratified based on CD-31/PAS dual staining and subsequently the expression status of phospho-EphA2 (S897), FAK, phospho-ERK1/2 and Laminin 5Ƴ2 was analysed by immunohistochemistry. Survival of patients was correlated within the stratified cohort.

RESULTS

The pathologically defined VM phenotype and phospho-EphA2 (S897) expression status were significantly associated with lower disease-free survival (DFS) and overall survival (OS). Both the features were also found to be significantly associated with higher nodal status, poor Nottingham Prognostic Index (NPI) and were more prevalent in the triple-negative breast cancer (TNBC) group. Incidentally, there were no significant association between age of the patient, grade and size of the tumour with VM and phospho-EphA2 (S897). The effector molecules of phospho-EphA2 (S897) viz., Focal Adhesion Kinase (FAK), phospho-ERK1/2 and Laminin 5Ƴ2 were significantly upregulated in the VM-positive cohort. Survival analysis revealed that the VM and phospho-EphA2 (S897) dual-positive cohort had poorest DFS [mean time = 48.313 (39.992-56.633) months] and OS [mean time = 56.692 (49.055-64.328) months]. Individually, VM-positive [Hazard Ratio (HR) 6.005; 95% confidence interval (CI) 2.002-18.018; P = 0.001 for DFS and HR 11.654; 95% CI 3.195-42.508; P < 0.0001 for OS] and phospho-EphA2 (S897)-positive (HR 4.342; 95% CI 1.717-10.983; P = 0.002 for DFS and HR 5.853; 95% CI 1.663-20.602; P = 0.006 for OS) expression proved to be independent indicators of prognosis.

CONCLUSION

This study evaluated tumour dependency on oncogenic EphA2 receptor regulation and VM in invasive carcinoma of the breast and their prognostic significance. Significant correlations between VM, phospho-EphA2 and several clinicopathologic parameters of breast cancer were found. Subsequently, the occurrence of VM or phospho-EphA2 expression proved to be major contributors for poor prognosis in patients with breast cancer but their simultaneous expression failed to be an independent risk factor.

Ephrin‑B2 inhibits cell proliferation and motility in vitro and predicts longer metastasis‑free survival in breast cancer

The tyrosine kinase receptor EphB4 and its ligand ephrin‑B2 interact through cell‑to‑cell contacts. Upon interaction, EphB4 transmits bidirectional signals. A forward signal inside EphB4‑expressing cells is believed to suppress tumor growth, while inside the ephrin‑expressing cells, an oncogenic reverse signal arises. In breast cancer cells with a high EphB4 receptor expression the forward signal is low, in part due to the low expression of the ligand ephrin‑B2. Therefore, we hypothesized that by re‑introducing the ligand in EphB4‑positive cells, tumor suppression could be induced by the stimulation of the forward signal. This question was addressed in vitro by the stable lentiviral infection of breast cancer cells with either wild‑type EFNB2 or with a mutant EFNB2‑5F, unable to transmit reverse signaling. Furthermore, we investigated ephrin‑B and EphB4 protein expression in 216 paraffin‑embedded tumors using immunohistochemistry. The in vitro results indicated that ephrin‑B2 expression was associated with a lower cell proliferation, migration and motility compared with the control cells. These effects were more pronounced when the cells lacked the ability to transmit the reverse signal (B2‑5F). In clinical material, ephrin‑B protein expression was associated with a positive estrogen receptor (ER) status, a low HER‑2 expression and was negatively associated with Nottingham histologic grade (NHG) III. Ephrin‑B expression indicated a good prognosis, whereas EphB4 expression was associated with a shorter metastasis‑free survival in univariate and multivariate analysis. Furthermore, the prognostic value of EFNB2 and EPHB4 was confirmed at the gene expression level in public datasets. Thus, on the whole, the findings of this study suggest that ephrin‑B2 expression is associated with less proliferation and lower motility of breast cancer cells and with a longer patient survival in breast cancer.

Prognostic value of ephrin B receptors in breast cancer: An online survival analysis using the microarray data of 3,554 patients

The roles of Ephrin B (EphB) receptors in cancer are relatively unknown as these receptors are associated with complex signaling pathways. A limited number of studies have investigated the association between EphB receptors and prognosis. Using the Kaplan-Meier plotter database, the present study investigated the associations between the mRNA expression levels of five EphB receptors and the outcomes of 3,554 patients with breast cancer who had been followed-up for 20 years. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated to assess the relative risk of survival. The results demonstrated that high mRNA expression levels of EphB2 (HR, 0.74; 95% CI, 0.66-0.84; P=2.1×10-6), EphB4 (HR, 0.82; 95% CI, 0.72-0.93; P=0.0023) and EphB6 (HR, 0.69; 95% CI, 0.61-0.78; P=3×10-9) were significantly associated with improved survival, while a high mRNA expression level of EphB3 (HR, 1.14; 95% CI, 1.01-1.28; P=0.029) was associated with worse survival for patients with breast cancer. High expression levels of all EphB receptors, including EphB1 (HR, 1.4; 95% CI, 1.02-1.94; P=0.039), EphB2 (HR, 1.34; 95% CI, 1.07-1.67; P=0.011), EphB3 (HR, 1.39; 95% CI, 1.11-1.73, P=0.0038), EphB4 (HR, 1.33; 95% CI, 1.06-1.67; P=0.013) and EphB6 (HR, 1.32; 95% CI, 1.05-1.65; P=0.016), were associated with an increased risk of mortality in patients with lymph-node-positive breast cancer. High mRNA expression levels of EphB1 were not associated with survival for all patients with breast cancer (HR, 0.85; 95% CI, 0.72-1.01; P=0.058). The results of the present suggested that EphB receptors may be useful as prognostic biomarkers of breast cancer.

First-in-human, phase I study of PF-06647263, an anti-EFNA4 calicheamicin antibody-drug conjugate, in patients with advanced solid tumors

PF-06647263, a novel antibody-drug conjugate consisting of an anti-EFNA4 antibody linked to a calicheamicin payload, has shown potent antitumor activity in human xenograft tumor models, including triple-negative breast cancer (TNBC). In the dose-escalation part 1 of this multicenter, open-label, phase I study (NCT02078752), successive cohorts of patients (n, 48) with advanced solid tumors and no available standard therapy received PF-06647263 every 3 weeks (Q3W) or every week (QW), following a modified toxicity probability interval (mTPI) method (initial dosing: 0.015 mg/kg Q3W). Primary objective in part 1 was to estimate the maximum tolerated dose (MTD) and select the recommended phase 2 dose (RP2D). In part 2 (dose-expansion cohort), 12 patients with pretreated, metastatic TNBC received PF-06647263 at the RP2D to further evaluate tumor response and overall safety. PF-06647263 QW administration (n, 23) was better tolerated than the Q3W regimen (n, 25) with only 1 DLT reported (thrombocytopenia). The most common AEs with the QW regimen (fatigue, nausea, vomiting, mucosal inflammation, thrombocytopenia, and diarrhea) were mostly mild to moderate in severity. The MTD was not estimated. PF-06647263 exposures increased in a dose-related manner across the doses evaluated. The RP2D was determined to be 0.015 mg/kg QW. Six (10%) patients achieved a confirmed partial response and 22 (36.7%) patients had stable disease. No correlations were observed between tumor responses and EFNA4 expression levels. Study findings showed manageable safety and favorable PK for PF-06647263 administered QW at the RP2D, with preliminary evidence of limited antitumor activity in patients with TNBC and ovarian cancer.

AMP-activated protein kinase: a potential therapeutic target for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive subset of breast carcinomas that lack expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2). Unlike other breast cancer subtypes, targeted therapy is presently unavailable for patients with TNBC. In spite of initial responses to chemotherapy, drug resistance tends to develop rapidly and the prognosis of metastatic TNBC is poor. Hence, there is an urgent need for novel-targeted treatment methods or development of safe and effective alternatives with recognized mechanism(s) of action. AMP-activated protein kinase (AMPK), an energy sensor, can regulate protein and lipid metabolism responding to alterations in energy supply. In the past 10 years, interest in AMPK has increased widely since it appeared as an attractive targeting molecule for cancer therapy. There has been a deep understanding of the possible role of abnormal AMPK signaling pathways in the regulation of growth and survival and the development of drug resistance in TNBC. The increasing popularity of using AMPK regulators for TNBC-targeted therapy is supported by a considerable development in ascertaining the molecular pathways implicated. This review highlights the available evidence for AMPK-targeted anti-TNBC activity of various agents or treatment strategies, with special attention placed on recent preclinical and clinical advances in the manipulation of AMPK in TNBC. The elaborative analysis of these AMPK-related signaling pathways will have a noteworthy impact on the development of AMPK regulators, resulting in efficacious treatments for this lethal disease.

Ephrin Receptor A4 is a New Kaposi's Sarcoma-Associated Herpesvirus Virus Entry Receptor

Kaposi's sarcoma-associated herpesvirus (KSHV) is a human gammaherpesvirus associated with the development of Kaposi's sarcoma (KS). KSHV target cells include endothelial cells, B cells, monocytes, epithelial cells, dendritic cells, macrophages, and fibroblasts. KSHV entry into target cells is a complex multistep process and is initiated by the binding and interaction of viral envelope glycoproteins with the cellular receptors. In the current studies, we have found that EphA4 promotes KSHV glycoprotein H/glycoprotein L (gH/gL)-mediated fusion and infection better than does ephrin A2 (EphA2) in HEK293T cells, indicating that EphA4 is a new KSHV entry receptor. To confirm that epithelial cells express EphA2 and EphA4, we analyzed the expression of EphA2 and EphA4 in epithelial cells, endothelial cells, B cells, monocytes, fibroblasts using RNA sequencing (RNA-seq) data analysis of existing data sets. We found that these cell types broadly express both EphA2 and EphA4, with the exception of monocytes and B cells. To confirm EphA4 is important for KSHV fusion and infection, we generated EphA2 and EphA4 single- and double-knockout cells. We found that both EphA2 and EphA4 play a role in KSHV fusion and infection, since EphA2-EphA4 double-knockout cells had the greatest decrease in fusion activity and infection compared to single-knockout cells. Fusion and infection of KSHV were rescued in the EphA2-EphA4 double-knockout cells upon overexpression of EphA2 and/or EphA4. EphA2 binds to both Epstein-Barr virus (EBV) and KSHV gH/gL; however, EphA4 binds only to KSHV gH/gL. Taken together, our results identify EphA4 as a new entry receptor for KSHV.IMPORTANCE The overall entry mechanism for herpesviruses is not completely known, including those for the human gammaherpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV). To fully understand the herpesvirus entry process, functional receptors need to be identified. In the current study, we found that EphA4 can also function for a KSHV entry receptor along with EphA2. Interestingly, we found that EphA4 does not function as an entry receptor for EBV, whereas EphA2 does. The discovery of EphA4 as a KSHV entry receptor has important implications for KSHV pathogenesis in humans, may prove useful in understanding the unique pathogenesis of KSHV infection in humans, and may uncover new potential targets that can be used for the development of novel interventional strategies.

EphA4-ADAM10 Interplay Patterns the Cochlear Sensory Epithelium through Local Disruption of Adherens Junctions

The cochlear sensory epithelium contains a functionally important triangular fluid-filled space between adjacent pillar cells referred to as the tunnel of Corti. However, the molecular mechanisms leading to local cell-cell separation during development remain elusive. Here we show that EphA4 associates with ADAM10 to promote the destruction of E-cadherin-based adhesions between adjacent pillar cells. These cells fail to separate from each other, and E-cadherin abnormally persists at the pillar cell junction in EphA4 forward-signaling-deficient mice, as well as in the presence of ADAM10 inhibitor. Using immunolabeling and an in situ proximity ligation assay, we found that EphA4 forms a complex with E-cadherin and its sheddase ADAM10, which could be activated by ephrin-B2 across the pillar cell junction to trigger the cleavage of E-cadherin. Altogether, our findings provide a new molecular insight into the regulation of adherens junctions, which might be extended to a variety of physiological or pathological processes.

Effects of EphB4 receptor expression on colorectal cancer cells, tumor growth, vascularization and composition

BACKGROUND

Colorectal cancer (CRC) is one of the most common causes of cancer-related deaths worldwide. Increased expression of the molecular target, EphB4 receptor, has been observed in several cancer types. However, studies on the role of EphB4 receptor in CRC have yielded contradictory results. The aim of this study was to investigate the influence of EphB4 expression levels on CRC cell behavior and its contribution to tumor growth and vascularization.

METHODS

SW480, LIM2405 and CT26 CRC cell lines were transfected with EphB4 expression vector. High EphB4 expressing cells were compared to low EphB4 expressing empty vector controls. Proliferation and migration assays as well as EphrinB2-Fc cell stimulations were conducted in vitro and subcutaneous xenografts of CRC were analyzed in vivo.

RESULTS

High EphB4 expression enhanced migratory ability of these CRC cell lines in vitro and contributed to a significant increase in tumor growth and vascularization in vivo. Tumours induced with high EphB4 expressing SW480 and LIM2405 cells yielded homogenous masses densely packed with cancer cells. EphrinB2-Fc cell stimulations induced cell clustering of high EphB4 expressing SW480 and LIM2405 in vitro.

CONCLUSION

These results suggest that with enhanced vascularization and an increase in migratory abilities, the high EphB4 expressing cells may be able to metastasize more readily.

Viewing the Eph receptors with a focus on breast cancer heterogeneity

Aberrant expression of different family members of the Eph/ephrin system, which comprises the Eph receptors (Ephs) and their ligands (ephrins), has been implicated in various malignancies including breast cancer. The latter presents as a heterogeneous disease with diverse molecular, morphologic and clinical behavior signatures. This review reflects the existing Eph/ephrin literature while focusing on breast cancer heterogeneity. Hormone positive, HER2 positive and triple negative breast cancer (TNBC) cell lines, xenografts/mutant animal models and patient samples are examined separately as, in humans, they represent entities with differences in prognosis and treatment. EphA2, EphB4 and EphB6 are the members most extensively studied in breast cancer. Existing research points to the potential use of various Eph/ephrin members as biomarkers for assessing prognosis and selecting the most suitable therapeutic strategies in variable clinical scenarios, also for overcoming drug resistance, in the era of breast cancer heterogeneity.