Novel anti-EPHA2 antibody, DS-8895a for cancer treatment

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

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

Targeting EphA2: a promising strategy to overcome chemoresistance and drug resistance in cancer

Erythropoietin-producing hepatocellular A2 (EphA2) is a vital member of the Eph tyrosine kinase receptor family and has been associated with developmental processes. However, it is often overexpressed in tumors and correlates with cancer progression and worse prognosis due to the activation of its noncanonical signaling pathway. Throughout cancer treatment, the emergence of drug-resistant tumor cells is relatively common. Since the early 2000s, researchers have focused on understanding the role of EphA2 in promoting drug resistance in different types of cancer, as well as finding efficient and secure EphA2 inhibitors. In this review, the current knowledge regarding induced resistance by EphA2 in cancer treatment is summarized, and the types of cancer that lead to the most cancer-related deaths are highlighted. Some EphA2 inhibitors were also investigated. Regardless of whether the cancer treatment has reached a drug-resistance stage in EphA2-overexpressing tumors, once EphA2 is involved in cancer progression and aggressiveness, targeting EphA2 is a promising therapeutic strategy, especially in combination with other target-drugs for synergistic effect. For that reason, monoclonal antibodies against EphA2 and inhibitors of this receptor should be investigated for efficacy and drug toxicity.

Targeted delivery of immune-stimulating bispecific RNA, inducing apoptosis and anti-tumor immunity in cancer cells

Double-stranded RNAs (dsRNA)-based strategies appeared as promising therapies to induce an inflammation in the tumor microenvironment. However, currently described systems generally lack active targeting of tissues, and their clinical translation is thus limited to intratumoral injection. Herein, we developed an antibody-siRNA-5'triphosphate conjugate with multiple modes of action, combining cell surface EphA2-specific internalization, leading to a simultaneous gene silencing and activation of the receptor retinoic acid-inducible gene I (RIG-I). Recognition of cytosolic siRNA-5'triphosphate by RIG-I triggers the expression of interferons and pro-inflammatory cytokines, inducing an inflammation of the tumor environment and activating neighboring immune cells. In addition, these RIG-I-specific effects synergized with siRNA-mediated PLK1 silencing to promote cancer cell death by apoptosis. Altogether, such immune-stimulating antibody-RNA conjugate opens a novel modality to overcome some limitations encountered by dsRNA molecules currently in clinical trials.

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.

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.

Effectiveness of anti-erythropoietin producing Hepatocellular receptor Type-A2 antibody in pancreatic cancer treatment

Erythropoietin-producing hepatocyte receptor type A2 (EphA2) is a tyrosine kinase that binds to ephrins (e.g., ephrin-A1) to initiate bidirectional signaling between cells. The binding of EphA2 and ephrin-A1 leads to the inhibition of Ras-MAPK activity and tumor growth. During tumorigenesis, the normal interaction between EphA2 and ephrin-A1 is hindered, which leads to the overexpression of EphA2 and induces cancer. The overexpression of EphA2 has been identified as a notable tumor marker in diagnosing and treating pancreatic cancer. In this study, we used phage display to isolate specific antibodies against the active site of EphA2 by using a discontinuous recombinant epitope for immunization. The therapeutic efficacy and inhibition mechanism of the generated antibody against pancreatic cancer was validated and clarified. The generated antibodies were bound to the conformational epitope of endogenous EphA2 on cancer cells, thus inducing cellular endocytosis and causing EphA2 degradation. Molecule signals pAKT, pERK, pFAK, and pSTAT3 were weakened, inhibiting the proliferation and migration of pancreatic cancer cells. The humanized antibody hSD5 could effectively inhibit the growth of the xenograft pancreatic cancer tumor cells BxPc-3 and Mia PaCa-2 in mice, respectively. When antibody hSD5 was administered with gemcitabine, significantly improved effects on tumor growth inhibition were observed. Based on the efficacy of the IgG hSD5 antibodies, clinical administration of the hSD5 antibodies is likely to suppress tumors in patients with pancreatic cancer and abnormal activation or overexpression of EphA2 signaling.

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.

Targeted drug-loaded PLGA-PCL microspheres for specific and localized treatment of triple negative breast cancer

The paper presents the results of the experimental and analytical study of targeted drug-loaded polymer-based microspheres made from blend polymer of polylactic-co-glycolic acid and polycaprolactone (PLGA-PCL) for targeted and localized cancer drug delivery. In vitro sustained release with detailed thermodynamically driven drug release kinetics, over a period of three months using encapsulated targeted drugs (prodigiosin-EphA2 or paclitaxel-EphA2) and control drugs [Prodigiosin (PGS), and paclitaxel (PTX)] were studied. Results from in vitro study showed a sustained and localized drug release that is well-characterized by non-Fickian Korsmeyer-Peppas kinetics model over the range of temperatures of 37 °C (body temperature), 41 °C, and 44 °C (hyperthermic temperatures). The in vitro alamar blue, and flow cytometry assays in the presence of the different drug-loaded polymer formulations resulted to cell death and cytotoxicity that was evidence through cell inhibition and late apoptosis on triple negative breast cancer (TNBC) cells (MDA-MB 231). In vivo studies carried out on groups of 4-week-old athymic nude mice that were induced with subcutaneous TNBC, showed that the localized release of the EphA2-conjugated drugs was effective in complete elimination of residual tumor after local surgical resection. Finally, ex vivo histopathological analysis carried out on the euthanized mice revealed no cytotoxicity and absence of breast cancer metastases in the liver, kidney, and lungs 12 weeks after treatment. The implications of the results are then discussed for the development of encapsulated EphA2-conjugated drugs formulation in the specific targeting, localized, and sustain drug release for the elimination of local recurred TNBC tumors after surgical resection.

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.

Proteomics uncover EPHA2 as a potential novel therapeutic target in colorectal cancer cell lines with acquired cetuximab resistance

BACKGROUND

In metastatic colorectal cancer (mCRC), acquired resistance against anti-EGFR targeted monoclonal antibodies, such as cetuximab (CET), was shown to be frequently caused by activating alterations in the RAS genes KRAS or NRAS. To this day, no efficient follow-up treatment option has emerged to treat mCRC in such a setting of resistance.

METHODS

To uncover potential targets for second-line targeted therapies, we used mass-spectrometric proteomics to shed light on kinome reprogramming in an established cellular model of acquired, KRAS-associated CET resistance.

RESULTS

This CET resistance was reflected by significant changes in the kinome, most of them individual to each cell line. Interestingly, all investigated resistant cell lines displayed upregulation of the Ephrin type-A receptor 2 (EPHA2), a well-known driver of traits of progression. Expectedly resistant cell lines displayed increased migration (p < 0.01) that was significantly reduced by targeting the EPHA2 signalling axis using RNA interference (RNAi) (p < 0.001), ephrin-A1 stimulation (p < 0.001), dasatinib (p < 0.01), or anti-EPHA2 antibody treatment (p < 0.001), identifying it as an actionable target in mCRC with acquired CET resistance.

CONCLUSION

These results highlight EPHA2 and its role in mCRC with KRAS-gene mutated acquired CET resistance and support its use as a potential actionable target for the development of future precision medicine therapies.

Targefrin: A Potent Agent Targeting the Ligand Binding Domain of EphA2

Overexpression of the receptor tyrosine kinase EphA2 is invariably associated with poor prognosis and development of aggressive metastatic cancers. Guided by our recently solved X-ray structure of the complex between an agonistic peptide and EphA2-LBD, we report on a novel agent, targefrin, that binds to EphA2-LBD with a 21 nM dissociation constant by isothermal titration calorimetry and presents an IC50 value of 10.8 nM in a biochemical assay. In cell-based assays, a dimeric version of the agent is as effective as the natural dimeric ligands (ephrinA1-Fc) in inducing cellular receptor internalization and degradation in several pancreatic cancer cell lines. When conjugated with chemotherapy, the agents can effectively deliver paclitaxel to pancreatic cancers in a mouse xenograft study. Given the pivotal role of EphA2 in tumor progression, we are confident that the agents reported could be further developed into innovative EphA2-targeting therapeutics.

Effective Tumor Targeting by EphA2-Agonist-Biotin-Streptavidin Conjugates

We recently reported on a potent synthetic agent, 135H11, that selectively targets the receptor tyrosine kinase, EphA2. While 135H11 possesses a relatively high binding affinity for the ligand-binding domain of EphA2 (Kd~130 nM), receptor activation in the cell required the synthesis of dimeric versions of such agent (namely 135H12). This was expected given that the natural ephrin ligands also need to be dimerized or clustered to elicit agonistic activity in cell. In the present report we investigated whether the agonistic activity of 135H11 could be enhanced by biotin conjugation followed by complex formation with streptavidin. Therefore, we measured the agonistic EphA2 activity of 135H11-biotin (147B5) at various agent/streptavidin ratios, side by side with 135H12, and a scrambled version of 147B5 in pancreatic- and breast-cancer cell lines. The (147B5)n-streptavidin complexes (when n = 2, 3, 4, but not when n = 1) induced a strong receptor degradation effect in both cell lines compared to 135H12 or the (scrambled-147B5)4-streptavidin complex as a control, indicating that multimerization of the targeting agent resulted in an increased ability to cause receptor clustering and internalization. Subsequently, we prepared an Alexa-Fluor-streptavidin conjugate to demonstrate that (147B5)4-AF-streptavidin, but not the scrambled equivalent complex, concentrates in pancreatic and breast cancers in orthotopic nude-mouse models. Hence, we conclude that these novel targeting agents, with proper derivatization with imaging reagents or chemotherapy, can be used as diagnostics, and/or to deliver chemotherapy selectively to EphA2-expressing tumors.

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: 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.

Ubiquitin chromatin remodelling after DNA damage is associated with the expression of key cancer genes and pathways

Modification of the cancer-associated chromatin landscape in response to therapeutic DNA damage influences gene expression and contributes to cell fate. The central histone mark H2Bub1 results from addition of a single ubiquitin on lysine 120 of histone H2B and is an important regulator of gene expression. Following treatment with a platinum-based chemotherapeutic, there is a reduction in global levels of H2Bub1 accompanied by an increase in levels of the tumor suppressor p53. Although total H2Bub1 decreases following DNA damage, H2Bub1 is enriched downstream of transcription start sites of specific genes. Gene-specific H2Bub1 enrichment was observed at a defined group of genes that clustered into cancer-related pathways and correlated with increased gene expression. H2Bub1-enriched genes encompassed fifteen p53 target genes including PPM1D, BTG2, PLK2, MDM2, CDKN1A and BBC3, genes related to ERK/MAPK signalling, those participating in nucleotide excision repair including XPC, and genes involved in the immune response and platinum drug resistance including POLH. Enrichment of H2Bub1 at key cancer-related genes may function to regulate gene expression and influence the cellular response to therapeutic DNA damage.

Prostate Cancer Metastases Are Strongly Inhibited by Agonistic Epha2 Ligands in an Orthotopic Mouse Model

Simple Summary

We demonstrate that pro-oncogenic EphA2 (ephrin type-A receptor 2) expression is activated in aggressive prostate cancers, and in mouse models of prostate cancers that are treated with enzalutamide. We also demonstrate in mouse models, that agonistic EphA2 targeting agents are very effective in suppressing cell migration and tumor metastases, hence anticipating the possible use of such agents in innovative anti-metastatic therapeutic modalities.

Abstract

The EphA2 tyrosine kinase receptor is highly expressed in several types of solid tumors. In our recent studies, we targeted EphA2 in pancreatic cancer with agonistic agents and demonstrated that suppression of EphA2 significantly reduced cancer-cell migration in cell-based assays. In the present study, we focused on targeting EphA2 in prostate cancer. While not all prostate cancers express EphA2, we showed that enzalutamide induced EphA2 expression in prostate cancer cells and in a patient-derived xenograft (PDX) animal model, which provides further impetus to target EphA2 in prostate cancer. Western blot studies showed that agonistic dimeric synthetic (135H12) and natural (ephrinA1-Fc) ligands effectively degraded EphA2 receptor in the prostate cancer cell line PC-3. The agents also delayed cell migration of prostate cancer (PC-3) cells, while an in vivo PC-3 orthotopic metastatic nude-mouse model also revealed that administration of ephrinA1-Fc or 135H12 strongly reduced metastases. The present study further validates EphA2 as an important target in metastatic prostate cancer treatment. Our results should incentivize further efforts aimed at developing potent and effective EphA2 synthetic agonistic agents for the treatment of EphA2-driven aggressive metastatic tumors including prostate, pancreatic, and breast cancer.

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.

Targeting EphA2 in cancer

Eph receptors and the corresponding Eph receptor-interacting (ephrin) ligands jointly constitute a critical cell signaling network that has multiple functions. The tyrosine kinase EphA2, which belongs to the family of Eph receptors, is highly produced in tumor tissues, while found at relatively low levels in most normal adult tissues, indicating its potential application in cancer treatment. After 30 years of investigation, a large amount of data regarding EphA2 functions have been compiled. Meanwhile, several compounds targeting EphA2 have been evaluated and tested in clinical studies, albeit with limited clinical success. The present review briefly describes the contribution of EphA2-ephrin A1 signaling axis to carcinogenesis. In addition, the roles of EphA2 in resistance to molecular-targeted agents were examined. In particular, we focused on EphA2's potential as a target for cancer treatment to provide insights into the application of EphA2 targeting in anticancer strategies. Overall, EphA2 represents a potential target for treating malignant tumors.

Approaches to Manipulate Ephrin-A:EphA Forward Signaling Pathway

Erythropoietin-producing hepatocellular carcinoma A (EphA) receptors and their ephrin-A ligands are key players of developmental events shaping the mature organism. Their expression is mostly restricted to stem cell niches in adults but is reactivated in pathological conditions including lesions in the heart, lung, or nervous system. They are also often misregulated in tumors. A wide range of molecular tools enabling the manipulation of the ephrin-A:EphA system are available, ranging from small molecules to peptides and genetically-encoded strategies. Their mechanism is either direct, targeting EphA receptors, or indirect through the modification of intracellular downstream pathways. Approaches enabling manipulation of ephrin-A:EphA forward signaling for the dissection of its signaling cascade, the investigation of its physiological roles or the development of therapeutic strategies are summarized here.

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.

Therapeutic Targeting of Pancreatic Cancer via EphA2 Dimeric Agonistic Agents

Recently, we reported on potent EphA2 targeting compounds and demonstrated that dimeric versions of such agents can exhibit remarkably increased agonistic activity in cellular assays compared to the monomers. Here we further characterize the activity of dimeric compounds at the structural, biochemical, and cellular level. In particular, we propose a structural model for the mechanism of receptor activation by dimeric agents and characterize the effect of most potent compounds in inducing EphA2 activation and degradation in a pancreatic cancer cell line. These cellular studies indicate that the pro-migratory effects induced by the receptor can be reversed in EphA2 knockout cells, by treatment with either a dimeric natural ligand (ephrinA1-Fc), or by our synthetic agonistic dimers. Based on these data we conclude that the proposed agents hold great potential as possible therapeutics in combination with standard of care, where these could help suppressing a major driver for cell migration and tumor metastases. Finally, we also found that, similar to ephrinA1-Fc, dimeric agents cause a sustained internalization of the EphA2 receptor, hence, with proper derivatizations, these could also be used to deliver chemotherapy selectively to pancreatic tumors.

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.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of the afucosylated, humanized anti-EPHA2 antibody DS-8895a: a first-in-human phase I dose escalation and dose expansion study in patients with advanced solid tumors

Background

Erythropoietin-producing hepatocellular receptor A2 (EPHA2) is overexpressed on the cell surface in many cancers and predicts poor prognosis. DS-8895a is a humanized anti-EPHA2 IgG1 monoclonal antibody afucosylated to enhance antibody-dependent cellular cytotoxicity activity. We conducted a two-step, phase I, multicenter, open-label study to determine the safety, tolerability, and pharmacokinetics of DS-8895a in patients with advanced solid tumors.

Methods

Step 1 was a dose escalation cohort in advanced solid tumor patients (six dose levels, 0.1–20 mg/kg) to determine Step 2 dosing. Step 2 was a dose expansion cohort in EPHA2-positive esophageal and gastric cancer patients. DS-8895a was intravenously administered every 2 weeks for the duration of the study, with a 28-day period to assess dose-limiting toxicity (DLT). Safety, pharmacokinetics, tumor response, and potential biomarkers were evaluated.

Results

Thirty-seven patients (Step 1: 22, Step 2: 15 [9: gastric cancer, 6: esophageal cancer]) were enrolled. Although one DLT (Grade 4 platelet count decreased) was observed in Step 1 (dose level 6, 20 mg/kg), the maximum tolerated dose was not reached; the highest dose (20 mg/kg) was used in Step 2. Of the 37 patients, 24 (64.9%) experienced drug-related adverse events (AEs) including three (8.1%) with Grade ≥ 3 AEs. Infusion-related reactions occurred in 19 patients (51.4%) but were manageable. All patients discontinued the study (evident disease progression, 33; AEs, 4). Maximum and trough serum DS-8895a concentrations increased dose-dependently. One gastric cancer patient achieved partial response and 13 patients achieved stable disease. Serum inflammatory cytokines transiently increased at completion of and 4 h after the start of DS-8895a administration. The proportion of CD16-positive natural killer (NK) cells (CD3⁻CD56⁺CD16⁺) decreased 4 h after the start of DS-8895a administration, and the ratio of CD3⁻CD56⁺CD137⁺ to CD3⁻CD56⁺CD16⁺ cells increased on day 3.

Conclusions

Twenty mg/kg DS-8895a infused intravenously every 2 weeks was generally safe and well tolerated in patients (n = 21) with advanced solid tumors. The exposure of DS-8895a seemed to increase dose-dependently and induce activated NK cells.

Trial registration

Phase 1 Study of DS-8895a in patients with advanced solid tumors (NCT02004717; 7 November 2013 to 2 February 2017); retrospectively registered on 9 December 2013.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0679-9) contains supplementary material, which is available to authorized users.

Refueling the Ischemic CNS: Guidance Molecules for Vascular Repair

Stroke patients have only limited therapeutic options and often remain with considerable disabilities. To promote neurological recovery, angiogenesis in the ischemic peri-infarct region has been recognized as an encouraging therapeutic target. Despite advances in mechanistic understanding of vascular growth and repair, effective and safe angiogenic treatments are currently missing. Besides the most intensively studied angiogenic growth factors, recent research has indicated that the process of vascular sprouting and migration also requires the participation of guidance molecules, many of which were initially identified as regulators of axonal growth. Here, we review the inhibitory and growth-promoting effects of guidance molecules on the vascular system and discuss their potential as novel angiogenic targets for neurovascular diseases.

Therapeutic Potential of Natural Killer Cells in Gastric Cancer

Gastric cancer (GC) is one of the most common cancers, with a high incidence of cancer death. Despite various therapeutic approaches, the cures and prognosis of advanced GC remain poor. Natural killer (NK) cells, which are known as important lymphocytes in innate immunity, play vital roles in suppressing GC initiation, progression, and metastases. A wide range of clinical settings shows that increasing the number of NK cells or improving NK cell antitumor activity is promising in GC patients. NK cell adoptive therapy (especially expanded NK cells) is a safe and well-tolerated method, which can enhance NK cell cytotoxicity against GC. Meanwhile, cytokines, immunomodulatory drugs, immune checkpoint blockades, antibodies, vaccines, and gene therapy have been found to directly or indirectly activate NK cells to improve their killing activity toward GC. In this review, we summarize recent advancements in the relationship between NK cells and GC and point out all the innovative strategies that can enhance NK cells' function to inhibit the growth of GC.

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.

Structure-Based Design of Novel EphA2 Agonistic Agents with Nanomolar Affinity in Vitro and in Cell

EphA2 overexpression is invariably associated with poor prognosis and development of aggressive metastatic cancers in pancreatic, prostate, lung, ovarian, and breast cancers and melanoma. Recent efforts from our laboratories identified a number of agonistic peptides targeting the ligand-binding domain of the EphA2 receptor. The individual agents, however, were still relatively weak in affinities (micromolar range) that precluded detailed structural studies on the mode of action. Using a systematic optimization of the 12-mer peptide mimetic 123B9, we were able to first derive an agent that displayed a submicromolar affinity for the receptor. This agent enabled cocrystallization with the EphA2 ligand-binding domain providing for the first time the structural basis for their agonistic mechanism of action. In addition, the atomic coordinates of the complex enabled rapid iterations of structure-based optimizations that resulted in a novel agonistic agent, named 135H11, with a nanomolar affinity for the receptor, as demonstrated by in vitro binding assays (isothermal titration calorimetry measurements), and a biochemical displacement assay. As we have recently demonstrated, the cellular activity of these agents is further increased by synthesizing dimeric versions of the compounds. Hence, we report that a dimeric version of 135H11 is extremely effective at low nanomolar concentrations to induce cellular receptor activation, internalization, and inhibition of cell migration in a pancreatic cancer cell line. Given the pivotal role of EphA2 in tumor growth, angiogenesis, drug resistance, and metastasis, these agents, and the associated structural studies, provide significant advancements in the field for the development of novel EphA2-targeting therapeutics or diagnostics.

Targeting Eph/ephrin system in cancer therapy

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

A review on Eph/ephrin, angiogenesis and lymphangiogenesis in gastric, colorectal and pancreatic cancers

Erythroprotein-producing human hepatocellular carcinoma receptors (Eph receptors) compose a subfamily of transmembrane protein-tyrosine kinases receptors that takes part in numerous physiological and pathological processes. Eph family receptor-interacting proteins (Ephrins) are ligands for those receptors. Eph/ephrin system is responsible for the cytoskeleton activity, cell adhesion, intercellular connection, cellular shape as well as cell motility. It affects neuron development and functioning, bone and glucose homeostasis, immune system and correct function of enterocytes. Moreover Eph/ephrin system is one of the crucial ones in angiogenesis and lymphangiogenesis. With such a wide range of impact it is clear that disturbed function of this system leads to pathology. Eph/ephrin system is involved in carcinogenesis and cancer progression. Although the idea of participation of ephrin in carcinogenesis is obvious, the exact way remains unclear because of complex bi-directional signaling and cross-talks with other pathways. Further studies are necessary to find a new target for treatment.