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.

Vandetanib drives growth arrest and promotes sensitivity to imatinib in chronic myeloid leukemia by targeting ephrin type-B receptor 4.

The oncogenic role of ephrin type-B receptor 4 (EPHB4) has been reported in many types of tumors, including chronic myeloid leukemia (CML). Here, we found that CML patients have a higher EPHB4 expression level than healthy subjects. EPHB4 knockdown inhibited growth of K562 cells (a human immortalized myelogenous leukemia cell line). In addition, transient transfection of EPHB4 siRNA led to sensitization to imatinib. These growth defects could be fully rescued by EPHB4 transfection. To identify an EPHB4-specific inhibitor with the potential of rapid translation into the clinic, a pool of clinical compounds was screened and vandetanib was found to be most sensitive to K562 cells, which express a high level of EPHB4. Vandetanib mainly acts on the intracellular tyrosine kinase domain and interacts stably with a hydrophobic pocket. Furthermore, vandetanib downregulated EPHB4 protein via the ubiquitin-proteasome pathway and inhibited PI3K/AKT and MAPK/ERK signaling pathways in K562 cells. Vandetanib alone significantly inhibited tumor growth in a K562 xenograft model. Furthermore, the combination of vandetanib and imatinib exhibited enhanced and synergistic growth inhibition against imatinib-resistant K562 cells in vitro and in vivo. These findings suggest that vandetanib drives growth arrest and overcomes the resistance to imatinib in CML via targeting EPHB4.

Prognostic and Therapeutic Implications of MicroRNA in Malignant Pleural Mesothelioma.

Malignant Pleural Mesothelioma (MPM) is an aggressive disease characterized by a dismal prognosis, mainly due to late diagnosis. To date, there are very few treatment options available and the refractoriness to the majority of therapeutic strategies, leading to consider MPM a relevant problem in public health. Therefore, the identification of novel prognostic markers and alternative therapeutic strategies remain a top priority. Several efforts have been made in this direction and to date a number of studies have investigated the role of microRNA as biomarkers in MPM, identifying the potential prognostic role of miR-29c* and miR-31. Very recently, the first microRNA signature able to discriminate poor or and good prognosis of MPM patients underwent surgery has been published. Very interestingly, several microRNA such as miR-1, miR-16, and miR-34b/c have been identified as potential therapeutic agents. Indeed, the forced expression of these microRNA resulted in anti-tumor effects both in vitro and in vivo. Besides, the introduction of microRNA mimic, some agents such as EphrinA1 and Onconase, seemed to exert anti-tumor effects through specific microRNA. Moreover, microRNA have also been reported to play a role in chemoresistance enhancing the sensitivity to specific drug such as pemetrexed. In this review the most relevant and updated data about the role of microRNA as prognostic markers and therapeutic agents in MPM will be presented, opening new avenues towards improved management of this aggressive disease.

A novel bispecific immunotoxin delivered by human bone marrow-derived mesenchymal stem cells to target blood vessels and vasculogenic mimicry of malignant gliomas.

BACKGROUND: In previous years, immunotoxins have been shown to be a greatly promising therapeutic tool for brain malignancies, such as gliomas. Human mesenchymal stem cells (hMSCs) exhibit tropism to tumor tissue. However, the effect of bispecific immunotoxins in malignant gliomas is still unknown. The aim of this study was to investigate the function of bispecific immunotoxins in human malignant gliomas. MATERIALS AND METHODS: In the present study, the bispecific immunotoxin VEGF165-ephrin A1-PE38KDEL was established using deoxyribonucleic acid shuffling and cloning techniques. The VEGF165-ephrin A1-PE38KDEL was delivered by hMSCs to mouse malignant gliomas. The effects of the bispecific immunotoxins on glioma-derived blood vessels and vasculogenic mimicry to elucidate the molecular mechanisms underlying the antitumorigenic effects of immunotoxins were examined in vivo. RESULTS: In vitro, transfected hMSCs significantly inhibited the cell viability of gliomas cell lines U87 and U251 in a dose-dependent manner compared with untransfected hMSCs (P<0.01). In vivo, the intratumoral injection of engineered hMSCs was effective at inhibiting tumor growth in a malignant glioma tumor model. CONCLUSION: The bispecific immunotoxin secreted from hMSCs acts as a novel strategy for improving treatment options for malignant gliomas in the clinic.

Therapeutic targeting of EPH receptors and their ligands.

Critical roles for EPH receptor (EPH)-ephrin signalling in a range of chronic and regenerative diseases are increasingly being recognized. In particular, the complex roles of EPHs and ephrins in tumour growth and progression, and in nerve injury and regeneration have been studied extensively. This has led to considerable progress in developing strategies for their therapeutic targeting, with some anticancer agents already in clinical trials. Promising leads for non-malignant diseases are also emerging, with compelling preclinical data encouraging clinical development. We discuss this rapidly developing area of drug discovery, highlighting the associated challenges and limitations.

[Angiogenesis research--quo vadis?]. / Angiogeneseforschung--Quo vadis?

The field of angiogenesis research has seen an explosion of knowledge within the last 10 years. More than 3500 angiogenesis-related papers are presently being published per year compared to the less than 200 annual papers published in the early 1990s. Paralleling the progress in the field of basic angiogenesis research, translational research has led to the identification of more than 100 angiomanipulatory compounds. Presently, more than 40 substances are in various phases of clinical trials. The prospect of these exciting developments is presently dampened by the negative outcome of some advanced clinical trials. Thus, following euphoria and disillusion, the field is presently experiencing that translational clinical research requires endurance to eventually accomplish the successful implementation of angiomanipulatory therapies in the clinical setting. The present article provides an overview of the field of angiogenesis research and summarizes ongoing efforts aimed at developing angiomanipulatory therapies.