Correlation of EPHA2 overexpression with high microvessel count in human primary colorectal cancer

Potential role of the Eph/ephrin system in colorectal cancer: emerging druggable molecular targets

The Eph/ephrin system regulates many developmental processes and adult tissue homeostasis. In colorectal cancer (CRC), it is involved in different processes including tumorigenesis, tumor angiogenesis, metastasis development, and cancer stem cell regeneration. However, conflicting data regarding Eph receptors in CRC, especially in its putative role as an oncogene or a suppressor gene, make the precise role of Eph-ephrin interaction confusing in CRC development. In this review, we provide an overview of the literature and highlight evidence that collaborates with these ambiguous roles of the Eph/ephrin system in CRC, as well as the molecular findings that represent promising therapeutic targets.

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.

Targeting EPHA2 with Kinase Inhibitors in Colorectal Cancer

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

Combination of protein and cell internalization SELEX identifies a potential RNA therapeutic and delivery platform to treat EphA2-expressing tumors

The EphA2 receptor tyrosine kinase is overexpressed in most solid tumors and acts as the major driver of tumorigenesis. In this study, we developed a novel approach for targeting the EphA2 receptor using a 2'-fluoro-modified pyrimidine RNA aptamer termed ATOP. We identified the ATOP EphA2 aptamer using a novel bioinformatics strategy that compared aptamers enriched during a protein SELEX using recombinant human EphA2 and a cell-internalization SELEX using EphA2-expressing MDA231 tumor cells. When applied to EphA2-expressing tumor cell lines, the ATOP EphA2 aptamer attenuated tumor cell migration and clonogenicity. In a mouse model of spontaneous metastasis, the ATOP EphA2 aptamer slowed primary tumor growth and significantly reduced the number of lung metastases. The EphA2 ATOP aptamer represents a promising candidate for the development of next-generation targeted therapies that provide safer and more effective treatment of EphA2-overexpressing tumors.

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

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

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.

EFNA1 in gastrointestinal cancer: Expression, regulation and clinical significance

Ephrin-A1 is a protein that in humans is encoded by the EFNA1 gene. The ephrins and EPH-related receptors comprise the largest subfamily of receptor protein-tyrosine kinases which play an indispensable role in normal growth and development or in the pathophysiology of various tumors. The role of EFNA1 in tumorigenesis and development is complex and depends on the cell type and microenvironment which in turn affect the expression of EFNA1. This article reviews the expression, prognostic value, regulation and clinical significance of EFNA1 in gastrointestinal tumors.

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.

Rationally integrating peptide-induced targeting and multimodal therapies in a dual-shell theranostic platform for orthotopic metastatic spinal tumors

Metastatic tumors present great challenges in diagnosis and treatment. Herein, a proof-of-concept theranostic nanoplatform composed of an Au nanoparticle core and a double-shell of metal-organic framework (MOF) and mesoporous silica (MS) is developed for combating spinal metastasis of lung cancer in an orthotopic model. Two drugs, Alpelisib (BYL719) as an inhibitor and cisplatin as a chemotherapeutic drug, are separately loaded into the double-shell with high loading content. A targeting peptide called dYNH and indocyanine green (ICG) are conjugated onto the outmost MS layer for specifically targeting metastatic tumor cells and enhancing photothermal effect. The resultant Au@MOF@MS-ICG -dYNH-PAA (AMMD) shows enhanced cellular uptake on tumor cells and accumulation at metastatic spinal tumors, as evidenced by fluorescent and photoacoustic imaging. Benefiting from this ultra-high affinity to tumor cells and the photothermal effect of ICG, the dual-drug-loaded AMMD (BCAMMD) modified with ICG exhibits superior therapeutic efficacy on spinal tumors. More importantly, bone destruction, which frequently occurs in bone-related tumors, is effectively suppressed by BYL719 in BCAMMD. Hence, by rationally integrating multiple functions, including excellent targeting ability, dual-drug loading, photothermal therapy, and photoacoustic imaging, the developed all-in-one theranostic nanoplatform provides a useful paradigm of employing nanomedicine to treat metastatic spinal tumors efficiently.

The Expression Profile and Prognostic Values of EPHA Family Members in Breast Cancer

BACKGROUND

EphAs are a class of ephrin receptors that belong to the membrane-bound receptor tyrosine kinases group. Accumulating experimental evidence has shown that the EphA family is involved in tumor progression, namely in cell proliferation, invasiveness, and metastasis. EphAs are a promising target for anticancer therapy. However, their role in breast cancer (BC) is still not well understood.

MATERIALS AND METHODS

We used a series of bioinformatic approaches to analyze the expression of the EphA family members and investigate their prognostic value in BC.

RESULTS

Lower expression levels of EphA2, EphA3, EphA4, EphA5, and EphA7 and higher expression levels of EphA10 were found in BC tissues compared to those in normal tissues. The expression levels of the EphA family genes were correlated with molecular subtyping but not with tumor stage. High expression levels of most EphAs indicated a better prognosis in BC.

CONCLUSIONS

This study suggested that EphA2, EphA3, EphA4, and EphA5 can act as tumor-inhibiting factors as well as biomarkers for the prognosis of BC.

Role of EFNA1 in tumorigenesis and prospects for cancer therapy

Cancer is one of the major threats to human health. It is of vital importance to reveal the mechanisms of tumorigenesis, identify effective biomarkers and develop novel treatments to improve patient outcome. EFNA1 (ephrinA1) is a member of the EFN family, and it has been studied extensively since its discovery in 1990. Increasing evidence indicates that EFNA1 plays a pivotal role in the pathogenesis of tumors. We provide a detailed overview of the expression and prognostic value of EFNA1 in different types of human malignancies. We briefly discuss the mechanisms of EFNA1 induction in hypoxic environments and its pro-angiogenic function in different cancer cells. We describe the effects of EFNA1 on tumor growth, invasiveness and metastasis. We summarize recent advances in EFNA1-associated cancer therapeutics with emphasis on the prospect of novel anti-tumor methods based on EFNA1.

Cantharidin-loaded functional mesoporous titanium peroxide nanoparticles for non-small cell lung cancer targeted chemotherapy combined with high effective photodynamic therapy

BACKGROUND

Although photodynamic therapy (PDT) has emerged as a potential alternative to conventional chemotherapy, the low reactive oxygen species (ROS) yield of the photosensitizer such as TiO2 nanoparticles has limited its application. In addition, it is difficult to achieve effective tumor treatment with a single tumor therapy.

METHODS

We used TiOx nanocomposite (YSA-PEG-TiOX ) instead of TiO2 as a photosensitizer to solve the problem of insufficient ROS generation in PDT. Benefiting from the desired mesoporous structure of TiOx, Cantharidin (CTD), one of the active components of mylabris, is loaded into TiOx for targeted combination of chemotherapy and PDT. The cellular uptake in human non-small cell lung carcinoma cell line (A549) and human normal breast cell line (MCF 10A) was evaluated by confocal microscopy. in vitro cytotoxicity was evaluated using Cell Counting Kit-8 assay. The ROS was detected via a chemical probe DCFH-DA and the photodynamic treatment effect of YSA-PEG-TiOx was further evaluated by a living-dead staining. The cell apoptosis was detected by the flow cytometry.

RESULTS

Our findings showed that the modification of YSA peptide improved the cytotoxicity of YSA-PEG-TiOX /CTD to EphA2 overexpressing A549 non-small cell lung cancer (NSCLC) than non-YSA modified counterparts. In addition, TiOx generated adequate ROS under X-ray irradiation to further kill cancer cells. Flow analysis results also proved the superiority of this combined treatment.

CONCLUSIONS

YSA-PEG-TiOX nanoparticles could significantly increase ROS production under X-ray exposure and provide a new drug delivery nanocarrier for CTD in combination with PDT to achieve effective NSCLC treatment.

Evaluation of the Anti-Tumor Activity of Small Molecules Targeting Eph/Ephrins in APC min/J Mice

The Eph receptors are the largest receptors tyrosine kinases (RTKs) family in humans and together with ephrin ligands constitute a complex cellular communication system often dysregulated in many tumors. The role of the Eph-ephrin system in colorectal cancer (CRC) has been investigated and different expression of Eph receptors have been associated with tumor development and progression. In light of this evidence, we investigated if a pharmacological approach aimed at inhibiting Eph/ephrin interaction through small molecules could prevent tumor growth in APC ^min/J mice. The 8-week treatment with the Eph-ephrin antagonist UniPR129 significantly reduced the number of adenomas in the ileum and decreased the diameter of adenomas in the same region. Overall our data suggested as UniPR129 could be able to slow down the tumor development in APC ^min/J mice. These results further confirm literature data about Eph kinases as a new valuable target in the intestinal cancer and for the first time showed the feasibility of the Eph-ephrin inhibition as a useful pharmacological approach against the intestinal tumorigenesis. In conclusion this work paves the way for further studies with Eph-ephrin inhibitors in order to confirm the Eph antagonism as innovative pharmacological approach with preventive benefit in the intestinal tumor development.

Roles of EphA2 Receptor in Angiogenesis Signaling Pathway of Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is one of the most common primary brain tumours in adults, accounting for almost 65% of all cases. Among solid tumours, GBM is characterised by strong angiogenesis, including the highest degree of vascular proliferation and endothelial cell hyperplasia. Despite numerous improvements in existing treatment approaches, the prognosis of GBM patients remains poor, with a mean survival of only 14.6 months. Growing evidence has shown significant overexpression of the ephrin type-A receptor 2 (EphA2) receptor in various malignancies, including GBM, as well as a correlation to poor prognoses. It is believed that EphA2 receptors play important roles in mediating GBM tumourigenesis, including invasion, metastasis, and angiogenesis. Despite the clinical and pathological importance of tumour-associated vasculature, the underlying mechanism involving EphA2 is poorly known. Here, we have summarised the current knowledge in the field regarding EphA2 receptors’ roles in the angiogenesis of GBM.

Increased expression of EphA2 and E-N cadherin switch in primary hepatocellular carcinoma

Aim

To investigate the expression and clinical significance of ephrin type-A receptor 2 and epithelial-mesenchymal transition-related proteins in primary hepatocellular carcinoma.

Methods

Tissues from 52 primary hepatocellular carcinomas and 12 human normal liver tissues were detected for expression of ephrin type-A receptor 2, E-cadherin, and N-cadherin by immunochemistry. Cinicopathological features of hepatocellular carcinoma and tumor recurrence after operation were studied for the association with these molecular expressions and E-N cadherin switch.

Results

Increased expressions of ephrin type-A receptor 2 and N-cadherin and reduced expression of E-cadherin were significantly detected in hepatocellular carcinoma compared with normal liver tissues. Univariate analysis showed that there were close associations between unfavorable clinicopathological features and expressions of ephrin type-A receptor 2, E-cadherin, N-cadherin, and E-N cadherin switch. Ephrin type-A receptor 2 and E-cadherin expressions were confirmed as independent prognostic factors when corrected with age, gender, AFP, HBsAg, liver cirrhosis, tumor size, nodules, capsule, portal vein invasion, cell differentiation, and TNM stage.

Conclusions

The overexpression of ephrin type-A receptor 2 protein is correlated with the number of tumors, capsular integrity, portal vein cancer thrombus and clinical stages. Epithelial-mesenchymal transition regulated by ephrin type-A receptor 2 is involved in the aggressive clinicopathological features and prognosis, suggesting that the receptor may play an important role in the progression and metastasis of hepatocellular carcinoma.

EphA2 signaling is impacted by carcinoembryonic antigen cell adhesion molecule 1-L expression in colorectal cancer liver metastasis in a cell context-dependent manner

We have shown that carcinoembryonic antigen cell adhesion molecule 1 long isoform (CEACAM1-L) expression in MC38 metastatic colorectal cancer (CRC) cells results in liver metastasis inhibition via CCL2 and STAT3 signaling. But other molecular mechanisms orchestrating CEACAM1-L-mediated metastasis inhibition remain to be defined. We screened a panel of mouse and human CRC cells and evaluated their metastatic outcome after CEACAM1 overexpression or downregulation. An unbiased transcript profiling and a phospho-receptor tyrosine kinase screen comparing MC38 CEACAM1-L-expressing and non-expressing (CT) CRC cells revealed reduced ephrin type-A receptor 2 (EPHA2) expression and activity. An EPHA2-specific inhibitor reduced EPHA2 downstream signaling in CT cells similar to that in CEACAM1-L cells with decreased proliferation and migration. Human CRC patients exhibiting high CEACAM1 in combination with low EPHA2 expression benefited from longer time to first recurrence/metastasis compared to those with high EPHA2 expression. With the added interaction of CEACAM6, we denoted that CEACAM1 high- and EPHA2 low-expressing patient samples with lower CEACAM6 expression also exhibited a longer time to first recurrence/metastasis. In HT29 human CRC cells, down-regulation of CEACAM1 along with CEA and CEACAM6 up-regulation led to higher metastatic burden. Overall, CEACAM1-L expression in poorly differentiated CRC can inhibit liver metastasis through cell context-dependent EPHA2-mediated signaling. However, CEACAM1’s role should be considered in the presence of other CEACAM family members.

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.

Evaluation of EphA2 and EphB4 as Targets for Image-Guided Colorectal Cancer Surgery

Targeted image-guided oncologic surgery (IGOS) relies on the recognition of cell surface-associated proteins, which should be abundantly present on tumor cells but preferably absent on cells in surrounding healthy tissue. The transmembrane receptor tyrosine kinase EphA2, a member of the A class of the Eph receptor family, has been reported to be highly overexpressed in several tumor types including breast, lung, brain, prostate, and colon cancer and is considered amongst the most promising cell membrane-associated tumor antigens by the NIH. Another member of the Eph receptor family belonging to the B class, EphB4, has also been found to be upregulated in multiple cancer types. In this study, EphA2 and EphB4 are evaluated as targets for IGOS of colorectal cancer by immunohistochemistry (IHC) using a tissue microarray (TMA) consisting of 168 pairs of tumor and normal tissue. The IHC sections were scored for staining intensity and percentage of cells stained. The results show a significantly enhanced staining intensity and more widespread distribution in tumor tissue compared with adjacent normal tissue for EphA2 as well as EphB4. Based on its more consistently higher score in colorectal tumor tissue compared to normal tissue, EphB4 appears to be a promising candidate for IGOS of colorectal cancer. In vitro experiments using antibodies on human colon cancer cells confirmed the possibility of EphB4 as target for imaging.

Phosphotyrosine profiling identifies ephrin receptor A2 as a potential therapeutic target in esophageal squamous-cell carcinoma

Esophageal squamous‐cell carcinoma (ESCC) is one of the most common malignancies in Asia. Currently, surgical resection of early‐stage tumor is the best available treatment. However, most patients present late when surgery is not an option. Data suggest that chemotherapy regimens are inadequate for clinical management of advanced cancer. Targeted therapy has emerged as one of the most promising approaches to treat several malignancies. A prerequisite for developing targeted therapy is prior knowledge of proteins and pathways that drive proliferation in malignancies. We carried out phosphotyrosine profiling across four different ESCC cell lines and compared it to non‐neoplastic Het‐1A cell line to identify activated tyrosine kinase signaling pathways in ESCC. A total of 278 unique phosphopeptides were identified across these cell lines. This included several tyrosine kinases and their substrates that were hyperphosphorylated in ESCC. Ephrin receptor A2 (EPHA2), a receptor tyrosine kinase, was hyperphosphorylated in all the ESCC cell lines used in the study. EPHA2 is reported to be oncogenic in several cancers and is also known to promote metastasis. Immunohistochemistry‐based studies have revealed EPHA2 is overexpressed in nearly 50% of ESCC. We demonstrated EPHA2 as a potential therapeutic target in ESCC by carrying out siRNA‐based knockdown studies. Knockdown of EPHA2 in ESCC cell line TE8 resulted in significant decrease in cell proliferation and invasion, suggesting it is a promising therapeutic target in ESCC that warrants further evaluation.

EphA2 Expression Is a Key Driver of Migration and Invasion and a Poor Prognostic Marker in Colorectal Cancer

PURPOSE

EphA2, a member of the Eph receptor tyrosine kinases family, is an important regulator of tumor initiation, neovascularization, and metastasis in a wide range of epithelial and mesenchymal cancers; however, its role in colorectal cancer recurrence and progression is unclear.

EXPERIMENTAL DESIGN

EphA2 expression was determined by immunohistochemistry in stage II/III colorectal tumors (N = 338), and findings correlated with clinical outcome. The correlation between EphA2 expression and stem cell markers CD44 and Lgr5 was examined. The role of EphA2 in migration/invasion was assessed using a panel of KRAS wild-type (WT) and mutant (MT) parental and invasive colorectal cancer cell line models.

RESULTS

Colorectal tumors displayed significantly higher expression levels of EphA2 compared with matched normal tissue, which positively correlated with high CD44 and Lgr5 expression levels. Moreover, high EphA2 mRNA and protein expression were found to be associated with poor overall survival in stage II/III colorectal cancer tissues, in both univariate and multivariate analyses. Preclinically, we found that EphA2 was highly expressed in KRASMT colorectal cancer cells and that EphA2 levels are regulated by the KRAS-driven MAPK and RalGDS-RalA pathways. Moreover, EphA2 levels were elevated in several invasive daughter cell lines, and downregulation of EphA2 using RNAi or recombinant EFNA1 suppressed migration and invasion of KRASMT colorectal cancer cells.

CONCLUSIONS

These data show that EpHA2 is a poor prognostic marker in stage II/III colorectal cancer, which may be due to its ability to promote cell migration and invasion, providing support for the further investigation of EphA2 as a novel prognostic biomarker and therapeutic target.

Overexpression of Ephrin A2 receptors in cancer stromal cells is a prognostic factor for the relapse of gastric cancer

BACKGROUND

Microenvironments control cancer growth and progression. We explored the prognostic impact of stromal reaction and cancer stromal cells on relapse risk and survival after curative gastrectomy in gastric cancer patients.

METHODS

Tissue samples were obtained from 107 patients with gastric adenocarcinoma who underwent curative (R0) gastrectomy. Primary stromal cells isolated from gastric cancer tissue (GCSC) and normal gastric tissue (Gastric stromal cell: GSC) in each patient were cultured and subjected to comprehensive proteome (LC-MS/MS) and real-time RT-PCR analysis. Expression of Ephrin A2 receptors (EphA2) in cancers and GCSC was evaluated immunohistochemically. Intermingling of EphA2-positive cancer cells and GCSC (IC/A2+) and overexpression of EphA2 in cancer cells (Ca/A2+) in invasive parts of tumors were assessed, as were relationships of IC/A2+, Ca/A2+, and clinicopathological factors with relapse-free survival and overall survival.

RESULTS

Proteome analysis showed that EphA2 expression was significantly higher in GCSC than GSC. Real-time RT-PCR analysis showed that levels of EphA1/A2/A3/A5 and EphB2/B4 were ≥2.0-fold higher in GCSC than GSC. Ca/A2 and IC/A2 were positive in 65 (60.7 %) and 26 (24.3 %) patients, respectively. Relapse was significantly more frequent in IC/A2-positive than in IC/A2-negative (HR, 2.12; 95 % CI, 1.16-5.41; p = 0.0207) patients. Among the 54 patients who received S-1 adjuvant chemotherapy, relapse-free survival (RFS) was significantly shorter in those who were IC/A2-positive than in those who were IC/A2-negative and Ca/A2-negative (HR, 2.83; 95 % CI, 1.12-12.12; p = 0.0339). Multivariable analysis indicated that pathological stage (p = 0.010) and IC/A2+ (p = 0.008) were independent risk factors for recurrence.

CONCLUSION

IC/A2+ was predictive of relapse after curative (R0) gastrectomy.

Dual targeting for metastatic breast cancer and tumor neovasculature by EphA2-mediated nanocarriers

EphA2 is a transmembrane receptor tyrosine kinase that is highly expressed on both tumor neovasculature and some kinds of tumor cells. Here, a homing peptide with a sequence of YSAYPDSVPMMSK (YSA) that binds specifically with EphA2 was utilized to modify the stealth liposomes (YSA-LP). With a particle size of about 85 nm, this functionalized nanocarrier was loaded with fluorescent probe or doxorubicin (DOX) and investigated in vitro and in vivo. In the cellular endocytosis studies in vitro, coumarin-6 loaded YSA-LP exhibited significant specificity to both EphA2-overexpressing tumor cells (MDA-MB-231) and human umbilical vein endothelial cells (HUVEC) via a YSA mediated interaction. In a MDA-MB-231 xenograft tumor mouse model, DiR-loaded YSA-LP showed more lasting accumulation in tumor tissue by small animal imaging compared to unmodified liposomes (LP). Further, YSA-LP greatly facilitated the efficacy of DOX loaded against both tumor cells and tumor angiogenesis in the same mouse model, evidenced by inhibiting tumor growth, metastasis and CD31 expression as well as inducing cancer cell apoptosis. Additionally, YSA-LP (DOX) showed relatively low systemic and cardiac toxicity compared with control groups. In conclusion, YSA might be a promising targeting motif for EphA2-overexpressing tumor cells and tumor neovasculature, which could be used to mediate drug delivery for chemotherapy agents.

Mutational analysis of genes coding for cell surface proteins in colorectal cancer cell lines reveal novel altered pathways, druggable mutations and mutated epitopes for targeted therapy

We carried out a mutational analysis of 3,594 genes coding for cell surface proteins (Surfaceome) in 23 colorectal cancer cell lines, searching for new altered pathways, druggable mutations and mutated epitopes for targeted therapy in colorectal cancer. A total of 3,944 somatic non-synonymous substitutions and 595 InDels, occurring in 2,061 (57%) Surfaceome genes were catalogued. We identified 48 genes not previously described as mutated in colorectal tumors in the TCGA database, including genes that are mutated and expressed in >10% of the cell lines (SEMA4C, FGFRL1, PKD1, FAM38A, WDR81, TMEM136, SLC36A1, SLC26A6, IGFLR1). Analysis of these genes uncovered important roles for FGF and SEMA4 signaling in colorectal cancer with possible therapeutic implications. We also found that cell lines express on average 11 druggable mutations, including frequent mutations (>20%) in the receptor tyrosine kinases AXL and EPHA2, which have not been previously considered as potential targets for colorectal cancer. Finally, we identified 82 cell surface mutated epitopes, however expression of only 30% of these epitopes was detected in our cell lines. Notwithstanding, 92% of these epitopes were expressed in cell lines with the mutator phenotype, opening new venues for the use of "general" immune checkpoint drugs in this subset of patients.

Loss of EphB6 protein expression in human colorectal cancer correlates with poor prognosis

Erythropoietin-producing hepatocyte (Eph) receptor family constitutes the largest family of tyrosine kinase receptors in the human genome. Loss of EphB6, a kinase-deficient receptor, correlated with a negative outcome in several carcinomas. This study aimed to investigate the expression of EphB6 protein and mRNA levels in colorectal cancers (CRCs) and possible correlations with clinicopathological variables and prognosis. To assess protein expression level, 124 CRCs and 57 colorectal adenomas samples were examined by immunostaining, the mRNA level of 43 paired CRC and the adjacent normal tissues were detected by using SYBR Green real-time PCR method. Decreased expression of EphB6 protein was found in CRC as compared with adenoma and normal tissues (χ(2) = 10.146, P = 0.001 and χ(2) = 45.333, P < 0.001, respectively). Low EphB6 mRNA expression was detected in 83.8% of cancers with negative or low EphB6 protein expression. The loss of EphB6 protein in CRC was positively associated with poorly differentiation (P < 0.001), lymph node metastasis (P = 0.006), Dukes stage (P = 0.002) and depth of invasion (P = 0.016). The patients with lymph node metastasis had a worse prognosis independently of gender, age, tumor site, stage and differentiation (RR = 0.404, CI 0.267-0.213, P < 0.001). Low levels of EphB6 protein expression are associated with a shorter mean duration of survival in colorectal cancer. Our results demonstrated that EphB6 may represent a novel, useful tissue biomarker for the prediction of survival rate in CRC.

Eph receptors and ephrins as targets for cancer therapy

Eph receptor tyrosine kinases and their ephrin ligands are involved in various signalling pathways and mediate critical steps of a wide variety of physiological and pathological processes. Increasing experimental evidence demonstrates that both Eph receptor and ephrin ligands are overexpressed in a number of human tumours, and are associated with tumour growth, invasiveness and metastasis. In this regard, the Eph/ephrin system provides the foundation for potentially exciting new targets for anticancer therapies for Eph-expressing tumours. The purpose of this review is to outline current advances in the role of Eph receptors and ephrin ligands in cancer, and to discuss novel therapeutic approaches of anticancer therapies.

Therapeutic synergy between microRNA and siRNA in ovarian cancer treatment

Development of improved RNA interference-based strategies is of utmost clinical importance. Although siRNA-mediated silencing of EphA2, an ovarian cancer oncogene, results in reduction of tumor growth, we present evidence that additional inhibition of EphA2 by a microRNA (miRNA) further "boosts" its antitumor effects. We identified miR-520d-3p as a tumor suppressor upstream of EphA2, whose expression correlated with favorable outcomes in two independent patient cohorts comprising 647 patients. Restoration of miR-520d-3p prominently decreased EphA2 protein levels, and suppressed tumor growth and migration/invasion both in vitro and in vivo. Dual inhibition of EphA2 in vivo using 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) nanoliposomes loaded with miR-520d-3p and EphA2 siRNA showed synergistic antitumor efficiency and greater therapeutic efficacy than either monotherapy alone. This synergy is at least in part due to miR-520d-3p targeting EphB2, another Eph receptor. Our data emphasize the feasibility of combined miRNA-siRNA therapy, and will have broad implications for innovative gene silencing therapies for cancer and other diseases.

SIGNIFICANCE

This study addresses a new concept of RNA inhibition therapy by combining miRNA and siRNA in nanoliposomal particles to target oncogenic pathways altered in ovarian cancer. Combined targeting of the Eph pathway using EphA2-targeting siRNA and the tumor suppressor miR-520d-3p exhibits remarkable therapeutic synergy and enhanced tumor suppression in vitro and in vivo compared with either monotherapy alone.

EphA4 is a prognostic factor in gastric cancer

BACKGROUND

Erythropoietin-producing hepatocellular (Eph) receptor, consisting of a family of receptor tyrosine kinases, plays critical roles in tumour development and is considered an attractive target for cancer therapy.

METHODS

Tumour samples were obtained from 222 patients with gastric adenocarcinoma who underwent gastrectomy. The expressions of EphA2, EphA4, and ephrinA1 were evaluated immunohistochemically.

RESULTS

High expressions of EphA2, EphA4, and ephrinA1 significantly correlated with variables related to tumour progression, including the depth of invasion, metastatic lymph nodes, pathological stage, and distant metastasis or recurrent disease. High expressions of EphA2, EphA4, and ephrinA1 were significantly associated with poorer disease-specific survival (DSS; p < 0.001, p < 0.001, p = 0.026). On multivariate analysis, EphA4 was an independent prognostic factor of DSS (hazard ratio [HR], 2.3; 95% confidence interval [CI], 1.1-4.8; p = 0.028), and EphA2 tended to be a prognostic factor (HR, 2.4; 95% CI, 1.0-5.8; p = 0.050). In stage II and III cancer, EphA4 and EphA2 were both significantly associated with shorter survival (p = 0.007 and 0.019), but only EphA2 was an independent prognostic factor (HR, 2.6; 95% CI, 1.1-6.3; p = 0.039).

CONCLUSION

EphA4 may play important roles in tumor progression and outcomes in patients with gastric cancer.

Epigenetic silencing of HOPX promotes cancer progression in colorectal cancer

Homeodomain-only protein X (HOPX)-β promoter methylation was recently shown to be frequent in human cancers and was suggested as tumor suppressor gene in esophageal and gastric cancer. The aim of this study was to investigate the mechanistic roles of HOPX-β promoter methylation and its clinical relevance in colorectal cancer (CRC). HOPX-β promoter methylation was assessed in human CRC cell lines and 294 CRC tissues. HOPX mRNA and protein levels were measured in relation to HOPX-β promoter methylation. The effects of forced HOPX expression on tumorigenesis were studied using in vitro and in vivo assays. The association between HOPX-β promoter methylation and clinical relevance of CRC patients was determined. HOPX-β promoter methylation is cancer-specific and frequently found in CRC cell lines and tissues, resulting in the down-regulation of HOPX mRNA and protein levels. In CRC cell lines, forced expression of HOPX suppressed proliferation, invasion, and anchorage-independent growth. DNA microarray analyses suggested critical downstream genes that are associated with cancer cell proliferation, invasion or angiogenesis. In a mouse xenograft model, HOPX inhibited tumorigenesis and angiogenesis. Finally, HOPX-β promoter methylation was associated with worse prognosis of stage III CRC patients (hazard ratio= 1.40, P = .035) and also with poor differentiation (P = .014). In conclusion, HOPX-β promoter methylation is a frequent and cancer-specific event in CRC progression. This epigenetic alteration may have clinical ramifications in the diagnosis and treatment of CRC patients.

EphA2/ephrinA1 mRNA expression and protein production in adenoid cystic carcinoma of salivary gland

PURPOSE

EphA2/ephrinA1 is believed to play a role in tumor growth and metastasis. The purpose of the present study was to determine the presence of EphA2/ephrinA1 in mRNA and protein adenoid cystic carcinoma.

MATERIALS AND METHODS

mRNA and protein expression and protein product of EphA2 and ephrinA1 in adenoid cystic carcinoma was investigated using real-time reverse transcriptase polymerase chain reaction, Western blot, and immunohistochemistry. The tyrosine-phosphorylated state of EphA2 in adenoid cystic carcinoma cells was also investigated.

RESULTS

Greater expression of EphA2 and ephrinA1 proteins and mRNA was detected in adenoid cystic carcinoma tissues. EphA2/ephrinA1 staining activities in adenoid cystic carcinoma were more significant than those in normal gland tissue (P < .01). EphA2/ephrinA1 expression correlated significantly to the microvessel density (P < .01). EphA2/ephrinA1 expression and microvessel density correlated with the clinical TNM stage, perineural invasion, and vascular invasion (P < .05). In 3 histologic types of adenoid cystic carcinoma, the expression of EphA2/ephrinA1 and microvessel density was significantly greater in the solid type than in the cribriform and tubular types (P < .01). We also noted that EphA2 was present in a nontyrosine-phosphorylated state.

CONCLUSIONS

The present study showed a high expression of EphA2/ephrinA1 in adenoid cystic carcinoma. EphA2/ephrinA1 can serve as a novel therapy target for adenoid cystic carcinoma.

Targeted delivery of paclitaxel to EphA2-expressing cancer cells

PURPOSE

YSA is an EphA2-targeting peptide that effectively delivers anticancer agents to prostate cancer tumors. Here, we report on how we increased the drug-like properties of this delivery system.

EXPERIMENTAL DESIGN

By introducing non-natural amino acids, we have designed two new EphA2 targeting peptides: YNH, where norleucine and homoserine replace the two methionine residues of YSA, and dYNH, where a D-tyrosine replaces the L-tyrosine at the first position of the YNH peptide. We describe the details of the synthesis of YNH and dYNH paclitaxel conjugates (YNH-PTX and dYNH-PTX) and their characterization in cells and in vivo.

RESULTS

dYNH-PTX showed improved stability in mouse serum and significantly reduced tumor size in a prostate cancer xenograft model and also reduced tumor vasculature in a syngeneic orthotopic allograft mouse model of renal cancer compared with vehicle or paclitaxel treatments.

CONCLUSION

This study reveals that targeting EphA2 with dYNH drug conjugates could represent an effective way to deliver anticancer agents to a variety of tumor types.

Proteomic analysis of exosomes from mutant KRAS colon cancer cells identifies intercellular transfer of mutant KRAS

Activating mutations in KRAS occur in 30% to 40% of colorectal cancers. How mutant KRAS alters cancer cell behavior has been studied intensively, but non-cell autonomous effects of mutant KRAS are less understood. We recently reported that exosomes isolated from mutant KRAS-expressing colon cancer cells enhanced the invasiveness of recipient cells relative to exosomes purified from wild-type KRAS-expressing cells, leading us to hypothesize mutant KRAS might affect neighboring and distant cells by regulating exosome composition and behavior. Herein, we show the results of a comprehensive proteomic analysis of exosomes from parental DLD-1 cells that contain both wild-type and G13D mutant KRAS alleles and isogenically matched derivative cell lines, DKO-1 (mutant KRAS allele only) and DKs-8 (wild-type KRAS allele only). Mutant KRAS status dramatically affects the composition of the exosome proteome. Exosomes from mutant KRAS cells contain many tumor-promoting proteins, including KRAS, EGFR, SRC family kinases, and integrins. DKs-8 cells internalize DKO-1 exosomes, and, notably, DKO-1 exosomes transfer mutant KRAS to DKs-8 cells, leading to enhanced three-dimensional growth of these wild-type KRAS-expressing non-transformed cells. These results have important implications for non-cell autonomous effects of mutant KRAS, such as field effect and tumor progression.

The Eph/Ephrin family in cancer metastasis: communication at the service of invasion

Cancer cells rely on intercellular communication throughout the different stages of their transformation and progression into metastasis. They do so by co-opting different processes such as cell-cell junctions, growth factors, receptors, and vesicular release. Initially characterized in neuronal and vascular tissues, Ephs and Ephrins, the largest family of receptor tyrosine kinases, comprised of two classes (i.e., A and B types), is increasingly scrutinized by cancer researchers. These proteins possess the particular features of both the receptors and ligands being membrane-bound which, via mandatory direct cell-cell interactions, undergo a bidirectional signal transduction initiated from both the receptor and the ligand. Following cell-cell interactions, Ephs/Ephrins behave as guidance molecules which trigger both repulsive and attractive signals, so as to direct the movement of cells through their immediate microenvironment. They also direct processes which include sorting and positioning and cytoskeleton rearrangements, thus making them perfect candidates for the control of the metastatic process. In fact, the role of Ephs and Ephrins in cancer progression has been demonstrated for many of the family members and they, surprisingly, have both tumor promoter and suppressor functions in different cellular contexts. They are also able to coordinate between multiple processes including cell survival, proliferation, differentiation, adhesion, motility, and invasion. This review is an attempt to summarize the data available on these Ephs/Ephrins' biological functions which contribute to the onset of aggressive cancers. I will also provide an overview of the factors which could explain the functional differences demonstrated by Ephs and Ephrins at different stages of tumor progression and whose elucidation is warranted for any future therapeutic targeting of this signaling pathway in cancer metastasis.

Regulation and misregulation of Eph/ephrin expression

The erythropoietin-producing hepatocellular (Eph) receptors form the largest family of receptor tyrosine kinases. Upon interaction of the Eph receptors with their ligands the ephrins, signaling cascades are initiated downstream of both receptor and ligand, a feature known as bidirectional signaling. The Eph receptors and ephrin ligands mediate important roles in embryonic development, particularly in establishing tissue organization by mediating cell adhesion or cell repulsion. In several adult tissues, at least one Eph/ephrin pair is found to play critical roles in tissue physiology and homeostasis. In recent years numerous members of this family have gained considerable attention since changes in their expression levels are a typical feature in cancer cells. Despite the fact that Eph/ephrin developmental expression profiles are well documented, little is known on transcriptional and post-transcriptional mechanisms that permits their highly specific, graded, complementary or overlapping expression patterns. Therefore understanding the transcriptional and post-transcriptional mechanisms regulating Eph/ephrin expression has far-reaching significance in biology. This review provides an overview of the mechanisms regulating Eph/ephrin expression. We highlight important emerging mechanisms of Eph/ephrin regulation or misregulation such as epigenetics and miRNAs.

Structural and functional characterization of monomeric EphrinA1 binding site to EphA2 receptor

The EphA2 receptor is overexpressed in glioblastoma multiforme and has been to shown to contribute to cell transformation, tumor initiation, progression, and maintenance. EphrinA1 (eA1) is a preferred ligand for the receptor. Treatment with monomeric eA1, the form of eA1 found in the extracellular environment, causes receptor phosphorylation, internalization, and down-regulation with subsequent anti-tumor effects. Here, we investigated the structure-function relationship of a monomeric eA1 focusing on its G-H loop ((108)FQRFTPFTLGKEFKE(123)G), a highly conserved region among eAs that mediates binding to their receptors. Alanine substitution mutants of the G-H loop amino acids were transfected into U-251 MG glioblastoma multiforme cells, and functional activity of each mutant in conditioned media was assessed by EphA2 down-regulation, ERK and AKT activation and cellular response assays. Alanine substitutions at positions Pro-113 Thr-115, Gly-117, Glu-122, and also Gln-109 enhanced the EphA2 receptor down-regulation and decreased p-ERK and p-AKT. Substitution mutants of eA1 at positions Phe-108, Arg-110, Phe-111, Thr-112, Phe-114, Leu-116, Lys-118, Glu-119, and Phe-120 had a deleterious effect on EphA2 down-regulation when compared with eA1-WT. Mutants at positions Phe-108, Lys-18, Lys-121, Gly-123 retained similar properties to eA1-WT. Recombinant eA1-R110A, -T115A, -G117A, and -F120A have been found to exhibit the same characteristics as the ligands contained in the conditioned media mainly due to the differences in their binding to the receptor. Thus, we have identified variants of eA1 that possess either superagonistic or antagonistic properties. These new findings will be important in the understanding of the receptor/ligand interactions and in further design of anti-cancer therapies targeting the eA/EphA system.

Higher expression of EphA2 and ephrin-A1 is related to favorable clinicopathological features in pathological stage I non-small cell lung carcinoma

BACKGROUND

The overexpression of receptor tyrosine kinase EphA2 has been reported in various cancers. In non-small cell lung cancer (NSCLC), a positive correlation has been reported between high EphA2 immunohistochemical staining level and poor prognosis. However, its ligand, ephrin-A1, is supposed to act as a tumor suppressor via the kinase activity of EphA2. Thus, the biphasic roles of this system are not fully elucidated. We retrospectively evaluated the expression levels of EphA2 and ephrin-A1 in surgically treated pathological (p-) stage I NSCLC tumor samples, and their relation to clinicopathologic features or postoperative prognoses.

METHODS

The levels of EphA2 and ephrin-A1 mRNA expression were quantified by real-time reverse-transcription polymerase chain reaction in tissue samples from p-stage I NSCLC patients who had undergone complete resection in our facility (n=195). They were divided into two (EphA2/ephrin-A1-Low and -High) groups based on the median expression level, and their respective clinicopathologic features and prognoses were analyzed. Furthermore, samples were stained immunohistochemically and classified into four groups according to their staining levels, and their prognoses analyzed.

RESULTS

Marked demographic differences were found between EphA2/ephrin-A1-Low and -High groups. Both EphA2-High and ephrin-A1-High groups had more females, no smoking history, adenocarcinoma histology, well-differentiated carcinomas, p-stage IA patients, and patients with EGFR gene mutations. Five-year overall survival rates of the EphA2-Low and the EphA2-High patient groups were 68.9% and 86.1%, respectively (P=0.017), and five-year disease-free survival rates were 69.9% and 83.2%, respectively (P=0.035). There were no statistical differences between ephrin-A1-Low and ephrin-A1-High groups concerning postoperative survival. Although showing smaller differences, the findings from the immunohistochemical analyses supported the above results.

CONCLUSIONS

Higher expression of EphA2 and ephrin-A1 was more related to the female sex, reduced smoking status, adenocarcinoma, well differentiated carcinomas, p-stage IA, and EGFR gene mutations. Higher EphA2 mRNA expression in p-stage I NSCLC patients was positively related to improved prognoses. These results may reflect a tumor suppressive role for the EphA2/ephrin-A1 system in a population of patients restricted to p-stage I NSCLC.

Eph-A2 and Eph-A4 expression in human benign and malignant thyroid lesions: an immunohistochemical study

Background

Ephrin receptors (Ephs) are frequently overexpressed in a wide variety of human malignant tumors, being associated with tumor growth, invasion, metastasis and angiogenesis. The aim of the present study was to evaluate the clinical significance of Eph-A2 and Eph-A4 expression in human benign and malignant thyroid lesions.

Material/Methods

Eph-A2 and Eph-A4 protein expression was assessed immunohistochemically on paraffin-embedded thyroid tissues from 131 patients with benign and malignant lesions.

Results

Eph-A2 was significantly overexpressed in malignant compared to benign thyroid lesions (p<0.001). Papillary carcinoma cases presented significantly increased Eph-A2 expression compared to those with hyperplasia nodules (p<0.001). Eph-A4 expression was not differentiated between cases with malignant or benign thyroid lesions. Papillary carcinoma cases presented significantly increased Eph-A4 expression compared to those with hyperplasia nodules (p=0.006). In the subgroup of malignant thyroid lesions, Eph-A2 and Eph-A4 expression was not associated with TNM stage, capsular, lymphatic or vascular invasion.

Conclusions

The present data suggest that Eph-A2, but not Eph-A4, overexpression may be associated with the malignant transformation of thyroid neoplasia. Further studies conducted on cohorts including a higher proportion of patients with advanced nodal and metastatic disease are recommended to draw definite conclusions on the clinical significance of Eph proteins in thyroid neoplasia.

Overexpression of EphA2 correlates with epithelial-mesenchymal transition-related proteins in gastric cancer and their prognostic importance for postoperative patients

The expression of EphA2 and three epithelial-mesenchymal transition-related proteins (E-cadherin, β-catenin and vimentin) was detected by immunohistochemistry in human gastric cancer and normal gastric mucosa. The expression of EphA2 and vimentin was significantly higher in gastric cancer tissues than in normal gastric mucosa tissues, and similar results were found for negative E-cadherin expression and ectopic β-catenin expression. Further analysis showed that the expression of EphA2 was closely correlated with the depth of tumor invasion, tumor-node-metastasis (TNM) stages and lymph node metastasis. Down-regulated expression of the epithelial protein E-cadherin, overexpression of the mesenchymal protein vimentin and ectopic expression of β-catenin were associated with the depth of tumor invasion, tumor differentiation, TNM stages and lymph node metastasis. The Spearman rank test indicated that the positive expression of EphA2 was negatively associated with E-cadherin expression and was positively correlated with β-catenin ectopic expression and vimentin expression. In addition, the Kaplan-Meier survival analysis showed that the overexpression of EphA2 and vimentin, ectopic expression of β-catenin and down-regulation of E-cadherin indicate a poor outcome. Moreover, multivariate Cox analysis showed that TNM stages, lymph node metastasis, EphA2 expression, E-cadherin expression and β-catenin ectopic expression were independent prognostic factors for postoperative gastric cancer. These findings indicate that the overexpression of EphA2 correlates with the loss of epithelial proteins and the appearance of mesenchymal proteins. Therefore, EphA2 may play a role in epithelial-mesenchymal transition in gastric cancer.

Clinical relevance of Ephs and ephrins in cancer: lessons from breast, colorectal, and lung cancer profiling

Pre-clinical studies provide compelling evidence that members of the Eph family of receptor tyrosine kinases and their ephrin ligands promote tumor growth, invasion and metastasis, and neovascularization. Tumor suppressive roles have also been reported for the receptors, and ligand-dependent versus ligand-independent signaling has emerged as one key mechanism underlying tumor suppressive function as opposed to oncogenic effects. Determining how these observations relate to clinical outcome is a crucial step for translating the biological and mechanistic data into new molecularly targeted therapies. Expression profiling in human patient samples bridges this gap and provides valuable clinical relevance to laboratory observations. In addition to analyses performed using privately assembled patient tumor samples, publically available microarray datasets and tissue microarrays linked to clinical data have emerged as tractable tools for addressing the clinical relevance of specific molecules and families of related molecules. This review summarizes the clinical relevance of specific Eph and ephrin molecules in human breast, colorectal, and lung cancers.

EphA2 is a critical oncogene in melanoma

EphA2 is a member of the Eph family of receptor tyrosine kinases and is highly expressed in many aggressive cancer types, including melanoma. We recently showed that EphA2 is also upregulated by ultraviolet radiation and is able to induce apoptosis. These findings suggest that EphA2 may have different, even paradoxical, effects on viability depending on the cellular context and that EphA2 mediates a delicate balance between life and death of the cell. To functionally clarify EphA2’s role in melanoma, we analyzed a panel of melanoma cell lines and found that EphA2 levels are elevated in a significant fraction of the samples. Specific depletion of EphA2 in high-expressing melanoma cells using shRNA led to profound reductions in cellular viability, colony formation and migration in vitro and a dramatic loss of tumorigenic potential in vivo. Stable introduction of EphA2 into low-expressing lines enhanced proliferation, colony formation and migration further supporting its pro-malignant phenotype. Interestingly, transient expression of EphA2 and/or Braf^V600E in non-transformed melanocytes led to significant and additive apoptosis. These results verify that EphA2 is an important oncogene and potentially a common source of “addiction” for many melanoma cells. Moreover, acute induction of EphA2 may purge genetically-susceptible cells thereby uncovering a more aggressive population that is in fact dependent on the oncogene.

Emerging strategies for EphA2 receptor targeting for cancer therapeutics

IMPORTANCE OF THE FIELD

High mortality rates with cancers warrant further development of earlier diagnostics and better treatment strategies. Membrane-bound erythropoietin-producing hepatocellular receptor tyrosine kinase class A2 (EphA2) is overexpressed in breast, prostate, urinary bladder, skin, lung, ovary and brain cancers.

AREAS COVERED IN THIS REVIEW

EphA2 overexpression in cancers, its signaling mechanisms and strategies to target its deregulation.

WHAT THE READER WILL GAIN

High EphA2 expression in cancer cells is correlated with a poor prognosis associated with recurrence due to enhanced metastasis. Interaction of the EphA2 receptor with its ligand (e.g., ephrinA1) triggers events that are deregulated and implicated in carcinogenesis. EphrinA1-independent oncogenic activity and ephrinA1-dependent tumor suppressor roles for EphA2 are described. Molecular interactions of EphA2 with signaling proteins are associated with the modulation of cytoskeleton dynamics, cell adhesion, proliferation, differentiation and metastasis. The deregulated signaling by EphA2 and its involvement in oncogenesis provide multiple avenues for the rational design of intervention approaches.

TAKE HOME MESSAGE

EphA2 has been tested as a drug target using multiple approaches such as agonist antibodies, RNA interference, immunotherapy, virus vector-mediated gene transfer, small-molecule inhibitors and nanoparticles. With over a decade of research, encouraging results with targeting of EphA2 expression in various pre-clinical cancer models necessitate further studies.

EPH-EPHRIN in human gastrointestinal cancers

Ever since its discovery two decades ago, the erythropoietin-producing hepatoma (EPH)-EPHRIN system has been shown to play multifaceted roles in human gastroenterological cancer as well as neurodevelopment. Over-expression, amplification and point mutations have been found in many human cancers and many investigators have shown correlations between these up-regulations and tumor angiogenesis. Thus, the genes in this family are considered to be potential targets of cancer therapy. On the other hand, the down-regulation of some members as a result of epigenetic changes has also been reported in some cancers. Furthermore, the correlation between altered expressions and clinical prognosis seems to be inconclusive. A huge amount of protein-protein interaction studies on the EPH-EPHRIN system have provided a basic scheme for signal transductions, especially bi-directional signaling involving EPH-ERPHRIN molecules at the cell membrane. This information also provides a manipulative strategy for harnessing the actions of these molecules. In this review, we summarize the known alterations of EPH-EPHRIN genes in human tumors of the esophagus, stomach, colorectum, liver and pancreas and present the perspective that the EPH-EPHRIN system could be a potential target of cancer therapy.

Clinical and biological impact of EphA2 overexpression and angiogenesis in endometrial cancer

OBJECTIVE

EphA2 overexpression predicts poor prognosis in endometrial cancer. To explore mechanisms for this association and assess its potential as therapeutic target, the relationship of EphA2 expression to markers of angiogenesis was examined using patient samples and an orthotopic mouse model of uterine cancer.

EXPERIMENTAL DESIGN

Expression of EphA2, estrogen receptor (ER), progesterone receptor (PR), Ki-67, vascular endothelial growth factor (VEGF) and microvessel density (MVD) was evaluated using immunohistochemistry in 85 endometrioid endometrial adenocarcinomas (EEC) by two independent investigators. Results were correlated with clinicopathological characteristics. The effect of EphA2- agonist monoclonal antibody EA5, alone or in combination with docetaxel was studied in vitro and in vivo. Samples were analyzed for markers of angiogenesis, proliferation and apoptosis.

RESULTS

Of 85 EEC samples, EphA2 was overexpressed in 47% of tumors and was significantly associated with high VEGF expression (p=0.001) and high MVD counts (p=0.02). High EphA2 expression, high VEGF expression and high MVD counts were significantly associated with shorter disease-specific survival. EA5 led to decrease in EphA2 expression and phosphorylation in vitro. In the murine model, while EA5 (33-88%) and docetaxel (23-55%) individually led to tumor inhibition over controls, combination therapy had the greatest efficacy (78-92%, p.

Peptide-functionalized nanogels for targeted siRNA delivery

A major bottleneck in the development of siRNA therapies is their delivery to the desired cell type or tissue, followed by effective passage across the cell membrane with subsequent silencing of the targeted mRNA. To address this problem, we describe the synthesis of core/shell hydrogel nanoparticles (nanogels) with surface-localized peptides that specifically target ovarian carcinoma cell lines possessing high expression levels of the Eph2A receptor. These nanogels are also demonstrated to be highly effective in the noncovalent encapsulation of siRNA and enable cell-specific delivery of the oligonucleotides in serum-containing medium. Cell toxicity and viability assays reveal that the nanogel construct is nontoxic under the conditions studied, as no toxicity or decrease in cell proliferation is observed following delivery. Importantly, a preliminary investigation of gene silencing illustrates that nanogel-mediated delivery of siRNA targeted to the EGF receptor results in knockdown of that receptor. Excellent protection of siRNA during endosomal uptake and endosomal escape of the nanogels is suggested by these results since siRNA activity in the cytosol is required for gene silencing.

Up-regulation of EphA2 and down-regulation of EphrinA1 are associated with the aggressive phenotype and poor prognosis of malignant glioma

Malignant gliomas display over-expression of the receptor tyrosine kinase EphA2. However, expression levels of the EphA2 ligand, EphrinA1, have not been fully elucidated. Seventy-eight patients with primary gliomas were included in this study who underwent surgical resection, radiation, and chemotherapy. The expression of EphA2 and EphrinA1 in tumors was assessed by immunohistochemistry and was statistically analyzed in combination with the follow-up data of patients. EphA2 was highly expressed in most malignant gliomas, but EphrinA1 was expressed at low levels in these tumors. The increased EphA2 expression is associated with higher-grade histology and poor patient prognosis. Contrary to this, the increased EphrinA1 expression is associated with lower-grade histology, but not associated with poor patient prognosis. Moreover, patients with tumors positive for EphA2 and negative for EphrinA1 had significantly shorter overall and progression-free survival than patients with tumors positive for both EphA2 and EphrinA1, negative for both EphA2 and EphrinA1, or negative for EphA2 and positive for EphrinA1. RNAi-mediated suppression of endogenous EphA2 in human glioblastoma multiforme cells resulted in increased EphrinA1 levels, as well as decreased cell viability, anchorage independence and in vitro invasion, and increased apoptosis. Furthermore, suppression of EphA2 resulted in delayed tumor growth in mice xenografts. Together, these data indicate that up-regulation of EphA2 and down-regulation of Ephrina1 may correlate with poor prognosis for patients with high-grade glioma. EphA2 suppression partially reversed the aggressive phenotypes of malignant gliomas, possibly through up-regulating EphrinA1 expression, which may help explain how EphA2 modulates the malignant progression of gliomas.

EphA2 mutation in lung squamous cell carcinoma promotes increased cell survival, cell invasion, focal adhesions, and mammalian target of rapamycin activation

Non-small cell lung cancer (NSCLC) has a poor prognosis and improved therapies are needed. Expression of EphA2 is increased in NSCLC metastases. In this study, we investigated EphA2 mutations in NSCLC and examined molecular pathways involved in NSCLC. Tumor and cell line DNA was sequenced. One EphA2 mutation was modeled by expression in BEAS2B cells, and functional and biochemical studies were conducted. A G391R mutation was detected in H2170 and 2/28 squamous cell carcinoma patient samples. EphA2 G391R caused constitutive activation of EphA2 with increased phosphorylation of Src, cortactin, and p130(Cas). Wild-type (WT) and G391R cells had 20 and 40% increased invasiveness; this was attenuated with knockdown of Src, cortactin, or p130(Cas). WT and G391R cells demonstrated a 70% increase in focal adhesion area. Mammalian target of rapamycin (mTOR) phosphorylation was increased in G391R cells with increased survival (55%) compared with WT (30%) and had increased sensitivity to rapamycin. A recurrent EphA2 mutation is present in lung squamous cell carcinoma and increases tumor invasion and survival through activation of focal adhesions and actin cytoskeletal regulatory proteins as well as mTOR. Further study of EphA2 as a therapeutic target is warranted.