LncRNA DGCR5 regulates the non-small cell lung cancer cell growth, migration, and invasion through regulating miR-211-5p/EPHB6 axis

Non-small cell lung cancer (NSCLC) accounts for about 80% of lung cancers worldwide. In recent years, importance of noncoding RNAs including long noncoding RNA and microRNA in regulating tumor progression has been appreciated. Abnormally expression of DiGeorge syndrome critical region gene 5 (DGCR5) was found in multiple human cancers but its function in NSCLC is largely unknown. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was conducted to explore DGCR5 expression level in NSCLC. Bioinformatic analyses were conducted to explore the targets of DGCR5. Cell counting kit-8 assay, wound-healing assay, and transwell invasion assay were performed to analyze functions of DGCR5. RT-qPCR revealed that DGCR5 expression in NSCLC cells was significantly lower than in normal cell. DGCR5 overexpression suppresses NSCLC cell growth, migration, and invasion. Online algorithms found EPH receptor B6 (EPHB6) and DGCR5 contains same miR-211-5p binding region. The predicted connections were further validated by luciferase activity reporter assay. Recue experiments showed DGCR5 regulates NSCLC cell behaviors via targeting miR-211-5p/EPHB6. These findings collectively identified DGCR5/miR-211-5p/EPHB6 triple axis in NSCLC, which may novel understanding regarding the tumorigenesis of NSCLC.

Androgen-deprivation therapy with enzalutamide enhances prostate cancer metastasis via decreasing the EPHB6 suppressor expression

Early studies suggested that using ADT with the recently developed anti-androgen Enzalutamide (Enz, also named as MDV3100 could extent castration resistant prostate cancer (CRPC) patients' survival an extra 4.8 months. Yet the therapy in most patients might eventually fail due to development of Enz-resistance. Here we found Enz might also increase some unwanted side-effects via increasing the CRPC cell invasion that might involve altering the Enz-mediated androgen receptor (AR)/EPHB6 suppressor/JNK signaling. Results from multiple clinical surveys also indicated that EPHP6 might function as a suppressor of PCa metastasis. Mechanism dissection revealed that Enz-mediated AR might function via binding to the androgen-response-element (ARE) on the EPHB6 promoter to decrease EPHB6 suppressor expression, which might then activate the phosphorylation of JNK signals to increase the CRPC cell invasion. Targeting this newly identified AR/EPHB6/JNK signaling with JNK inhibitor (SP600125) may then block/reverse the Enz-increased CRPC cell invasion. Collectively, our results suggest that Enz may increase CRPC cell invasion via altering the AR/EPHB6/JNK/MMP9 signaling and targeting this newly identified signaling may help us to increase the Enz efficacy to better suppress the CRPC at the later metastatic stage.

Targeting synthetic lethality between the SRC kinase and the EPHB6 receptor may benefit cancer treatment

Application of tumor genome sequencing has identified numerous loss-of-function alterations in cancer cells. While these alterations are difficult to target using direct interventions, they may be attacked with the help of the synthetic lethality (SL) approach. In this approach, inhibition of one gene causes lethality only when another gene is also completely or partially inactivated. The EPHB6 receptor tyrosine kinase has been shown to have anti-malignant properties and to be downregulated in multiple cancers, which makes it a very attractive target for SL applications. In our work, we used a genome-wide SL screen combined with expression and interaction network analyses, and identified the SRC kinase as a SL partner of EPHB6 in triple-negative breast cancer (TNBC) cells. Our experiments also reveal that this SL interaction can be targeted by small molecule SRC inhibitors, SU6656 and KX2-391, and can be used to improve elimination of human TNBC tumors in a xenograft model. Our observations are of potential practical importance, since TNBC is an aggressive heterogeneous malignancy with a very high rate of patient mortality due to the lack of targeted therapies, and our work indicates that FDA-approved SRC inhibitors may potentially be used in a personalized manner for treating patients with EPHB6-deficient TNBC. Our findings are also of a general interest, as EPHB6 is downregulated in multiple malignancies and our data serve as a proof of principle that EPHB6 deficiency may be targeted by small molecule inhibitors in the SL approach.

The intrinsically kinase-inactive EPHB6 receptor predisposes cancer cells to DR5-induced apoptosis by promoting mitochondrial fragmentation

Death Receptor 5 (DR5) is a promising target for cancer therapy due to its ability to selectively induce apoptosis in cancer cells. However, the therapeutic usefulness of DR5 agonists is currently limited by the frequent resistance of malignant tumours to its activation. The identification of molecular mechanisms that determine outcomes of DR5 action is therefore crucial for improving the efficiency of DR5-activating reagents in cancer treatment. Here, we provide evidence that an intrinsically kinase-inactive member of the Eph group of receptor tyrosine kinases, EPHB6, induces marked fragmentation of the mitochondrial network in breast cancer cells of triple-negative origin, lacking expression of the estrogen, progesterone and HER2 receptors. Remarkably, this response renders cancer cells more susceptible to DR5-mediated apoptosis. EPHB6 action in mitochondrial fragmentation proved to depend on its ability to activate the ERK-DRP1 pathway, which increases the frequency of organelle fission. Moreover, DRP1 activity is also essential to the EPHB6-mediated pro-apoptotic response that we observe in the context of DR5 activation. These findings provide the first description of a member of the receptor tyrosine kinase family capable of producing a pro-apoptotic effect through the activation of ERK-DRP1 signaling and subsequent mitochondrial fragmentation. Our observations are of potential practical importance, as they imply that DR5-activating therapeutic approaches should be applied in a more personalized manner to primarily treat EPHB6-expressing tumours. Finally, our findings also suggest that the EPHB6 receptor itself may represent a promising target for cancer therapy, since EPHB6 and DR5 co-activation should support more efficient elimination of cancer cells.

The PI3Kα inhibitor DFX24 suppresses tumor growth and metastasis in non-small cell lung cancer via ERK inhibition and EPHB6 reactivation

EPHB6 is a metastasis inhibitory gene that is frequently decreased or deficiency in non-small cell lung cancer (NSCLC), which contributed to the subsequent development of distant metastasis. These suggested the possibility that reactivation of EPHB6 might prevent the metastasis of NSCLC. Nevertheless, EPHB6 expression might also promote cancer cell growth and inhibit cell apoptosis by activating Akt and ERK pathway, apart from inhibition of migration and invasion. In the present study, we developed a novel quinazolin-4(3H)-one analog (DFX24) as a potential PI3Kα inhibitor, which inhibited both cell proliferation and metastasis of NSCLC cell lines. Investigation to the molecular mechanisms revealed DFX24 inhibited the cell growth and metastasis via inhibition of PI3Kα and ERK activity, as well as the increase in EPHB6 expression. In addition, DFX24 also induced cell cycle arrest and tumor cell apoptosis by inhibiting PI3K/Akt pathway and activating mitochondria-dependent pathway, respectively. These findings suggested that DFX24 might be considered as a novel drug candidate and may provide a potential therapy for NSCLC.

NRAS and EPHB6 mutation rates differ in metastatic melanomas of patients in the North Island versus South Island of New Zealand

Melanoma, the most aggressive skin cancer type, is responsible for 75% of skin cancer related deaths worldwide. Given that New Zealand (NZ) has the world's highest melanoma incidence, we sought to determine the frequency of mutations in NZ melanomas in recurrently mutated genes. NZ melanomas were from localities distributed between North (35°S-42°S) and South Islands (41°S-47°S). A total of 529 melanomas were analyzed for BRAF exon 15 mutations by Sanger sequencing, and also by Sequenom MelaCarta MassARRAY. While, a relatively low incidence of BRAFV600E mutations (23.4%) was observed overall in NZ melanomas, the incidence of NRAS mutations in South Island melanomas was high compared to North Island melanomas (38.3% vs. 21.9%, P=0.0005), and to The Cancer Genome Atlas database (TCGA) (38.3% vs. 22%, P=0.0004). In contrast, the incidence of EPHB6G404S mutations was 0% in South Island melanomas, and was 7.8% in North Island (P=0.0002). Overall, these data suggest that melanomas from geographically different regions in NZ have markedly different mutation frequencies, in particular in the NRAS and EPHB6 genes, when compared to TCGA or other populations. These data have implications for the causation and treatment of malignant melanoma in NZ.

The receptor tyrosine kinase EPHB6 regulates catecholamine exocytosis in adrenal gland chromaffin cells

The erythropoietin-producing human hepatocellular receptor EPH receptor B6 (EPHB6) is a receptor tyrosine kinase that has been shown previously to control catecholamine synthesis in the adrenal gland chromaffin cells (AGCCs) in a testosterone-dependent fashion. EPHB6 also has a role in regulating blood pressure, but several facets of this regulation remain unclear. Using amperometry recordings, we now found that catecholamine secretion by AGCCs is compromised in the absence of EPHB6. AGCCs from male knockout (KO) mice displayed reduced cortical F-actin disassembly, accompanied by decreased catecholamine secretion through exocytosis. This phenotype was not observed in AGCCs from female KO mice, suggesting that testosterone, but not estrogen, contributes to this phenotype. Of note, reverse signaling from EPHB6 to ephrin B1 (EFNB1) and a 7-amino acid-long segment in the EFNB1 intracellular tail were essential for the regulation of catecholamine secretion. Further downstream, the Ras homolog family member A (RHOA) and FYN proto-oncogene Src family tyrosine kinase (FYN)-proto-oncogene c-ABL-microtubule-associated monooxygenase calponin and LIM domain containing 1 (MICAL-1) pathways mediated the signaling from EFNB1 to the defective F-actin disassembly. We discuss the implications of EPHB6's effect on catecholamine exocytosis and secretion for blood pressure regulation.

Modulation of liver-intestine cadherin (Cadherin 17) expression, ERK phosphorylation and WNT signaling in EPHB6 receptor-expressing MDA-MB-231 cells

Aberrant expression of erythropoietin-producing hepatocellular carcinoma cell (EPH) receptors has been reported in a variety of human cancer types. In addition to modulating cell proliferation and migration, EPH receptors are also involved in tumor progression. The transcriptional activation and silencing of EPH receptors are also associated with tumorigenesis. However, the mechanisms underlying the involvement of EPH receptors in tumorigenesis have not been completely deciphered. We have investigated and described the role of EPHB6, a kinase-deficient receptor, in modulating the abundance of cadherin 17 and activation of other intracellular signaling proteins. We previously showed that EPHB6 alters the tumor phenotype of breast carcinoma cells. However, the mechanisms underlying these phenotypic changes had not previously been investigated. Herein we demonstrated the downstream effects of EPHB6 expression on the abundance of cadherin 17, mitogen-activated protein kinase (MEK2), extracellular signal-regulated kinase (ERK), phospho-ERK, β-catenin, phospho- glycogen synthase kinase 3 beta (GSK3β) (ser21/9), cell morphology and actin cytoskeleton. These comparisons were made between EPHB6-deficient MDA-MB-231 cells transfected with an empty pcDNA3 vector and cells stably transfected with an expression construct of EPHB6. The results indicate elevated levels of MEK2 and phospho-ERK. While there was no change in the amount of ERK, the abundance of cadherin 17, β-catenin and phospho-GSK3β was significantly reduced in EPHB6-transfected cells. These studies clearly demonstrate an inverse relationship between the levels of phospho-ERK and the abundance of cadherin 17, β-catenin and phospho-GSK3β in EPHB6-expressing MDA-MB-231 cells. From these data we conclude that EPHB6-mediated alterations arise due to changes in abundance and localization of cadherin 17 and activation of WNT signaling pathway. Transcriptional silencing of EPHB6 in native MDA-MB-231 cells and consequent effects on cadherin 17 and WNT pathway may, thus, be responsible for the invasive behavior of these cells.

Eph receptor B6 shapes a cold immune microenvironment, inhibiting anti-cancer immunity and immunotherapy response in bladder cancer

Background

The role of Eph receptors and related ephrin (EFN) ligands (as the largest family of transmembrane-bound RTKs) in immunomodulation in many types of cancer, especially bladder cancer (BLCA), is scarcely known.

Methods

A pan-cancer dataset was retrieved from The Cancer Genome Atlas (TCGA) to explore the relation between Eph receptor/EFN ligand family genes and immunomodulators and tumor-infiltrated immune cells (TIICs). Local BLCA, GSE32894, and GSE31684 cohorts were applied to validate. The IMvigor210 cohort was employed to explore the relationship between EPHB6 and immunotherapy response. Moreover, association between EPHB6 and molecular subtype was investigated to explore potential therapeutic strategies. Immunohistochemical staining of CD8 and CD68 was performed to validate the correlation between EPHB6 and TIICs.

Results

The pan-cancer analysis revealed variations in the immunological effects of Eph receptor/EFN ligand family genes across different types of cancer. EPHB6 expression negatively correlated with the expression of the majority of immunomodulators (including HLA and immune checkpoints), and CD8 T cells and macrophages in both the TCGA-BLCA and validation BLCA cohorts, shaping a cold immune microenvironment with inhibited immunity. In the IMvigor210 cohort, patients with high-EPHB6 highly correlated with a non-inflamed, low PD-L1 expression immune phenotype, and correspondingly, with less responders to immunotherapy. The high-EPHB6 group, enriched with the basal subtype, presented significantly fewer TP53 and more FGFR3 genomic alterations. Finally, a novel EPHB6-related Genes signature, with reliable and robust ability in prognosis prediction, was constructed.

Conclusions

This study comprehensively investigated the immunological effects of Eph receptor/EFN ligand family genes pan-cancer, and specially identified the immunosuppressive role of EPHB6 in BLCA. Furthermore, EPHB6 may predict the molecular subtype and prognosis of BLCA, and serve as a novel therapeutic target to improve the sensitivity of immunotherapy.

Study on the Role of EPHB6 in Inhibiting the Malignant Progression of Cervical Cancer C33A Cells by Binding to CBX7

Cervical cancer stands as the most frequently diagnosed malignancy affecting the female reproductive. The erythropoietin-producing hepatocyte (Eph) family tyrosine kinases play important roles in tumorigenesis and cancer aggression. However, the exact role of EPHB6 in cervical cancer remains unknown. The present study investigated the role of EPHB6 in the malignant process of cervical cancer. GEPIA, tnmplot and kmplot database was used to study the expression of EPHB6 in cervical cancer tissues. western blotting was used to detect the expression of EPHB6, CyclinD, CDK4, CDK6, CBX7, MMP2 and MMP9. CCK8 and EDU staining were used to detect cell proliferation. Wound healing and transwell were used to detect cell proliferation and migration. Flow cytometry was used to detect cell cycle level. The linkedomics database was used to predict the correlation of EPHB6 and CBX7 in cervical cancer. Subsequently, HDOCK server was used to predict the combination of EPHB6 and CBX7. Our current results suggested that the expression of EPHB6 is reduced in cervical cancer tissues and cell lines, and the lower the expression, the worse the prognosis. Moreover, overexpression of EPHB6 inhibits cell proliferation, invasion and migration and cycle acceleration of C33A cells. Furthermore, EPHB6 and CBX7 bind to each other in C33A cells, and EPHB6 inhibits cell proliferation, invasion, migration and cell cycle acceleration in cervical cancer by binding to CBX7. EPHB6 expression is reduced in cervical cancer tissues and cells. Its overexpression inhibits proliferation, invasion, migration, and cell cycle acceleration in C33A cells, exhibiting synergy when bound to CBX7.