Eph Receptors: Actors in Tumor Microenvironment

Diversity of Intercellular Communication Modes: A Cancer Biology Perspective

From the moment a cell is on the path to malignant transformation, its interaction with other cells from the microenvironment becomes altered. The flow of molecular information is at the heart of the cellular and systemic fate in tumors, and various processes participate in conveying key molecular information from or to certain cancer cells. For instance, the loss of tight junction molecules is part of the signal sent to cancer cells so that they are no longer bound to the primary tumors and are thus free to travel and metastasize. Upon the targeting of a single cell by a therapeutic drug, gap junctions are able to communicate death information to by-standing cells. The discovery of the importance of novel modes of cell-cell communication such as different types of extracellular vesicles or tunneling nanotubes is changing the way scientists look at these processes. However, are they all actively involved in different contexts at the same time or are they recruited to fulfill specific tasks? What does the multiplicity of modes mean for the overall progression of the disease? Here, we extend an open invitation to think about the overall significance of these questions, rather than engage in an elusive attempt at a systematic repertory of the mechanisms at play.

Cell Death, by Any Other Name…

Studies trying to understand cell death, this ultimate biological process, can be traced back to a century ago. Yet, unlike many other fashionable research interests, research on cell death is more alive than ever. New modes of cell death are discovered in specific contexts, as are new molecular pathways. But what is "cell death", really? This question has not found a definitive answer yet. Nevertheless, part of the answer is irreversibility, whereby cells can no longer recover from stress or injury. Here, we identify the most distinctive features of different modes of cell death, focusing on the executive final stages. In addition to the final stages, these modes can differ in their triggering stimulus, thus referring to the initial stages. Within this framework, we use a few illustrative examples to examine how intercellular communication factors in the demise of cells. First, we discuss the interplay between cell-cell communication and cell death during a few steps in the early development of multicellular organisms. Next, we will discuss this interplay in a fully developed and functional tissue, the gut, which is among the most rapidly renewing tissues in the body and, therefore, makes extensive use of cell death. Furthermore, we will discuss how the balance between cell death and communication is modified during a pathological condition, i.e., colon tumorigenesis, and how it could shed light on resistance to cancer therapy. Finally, we briefly review data on the role of cell-cell communication modes in the propagation of cell death signals and how this has been considered as a potential therapeutic approach. Far from vainly trying to provide a comprehensive review, we launch an invitation to ponder over the significance of cell death diversity and how it provides multiple opportunities for the contribution of various modes of intercellular communication.

Inhibition of EphA3 Expression in Tumour Stromal Cells Suppresses Tumour Growth and Progression

Tumour progression relies on interactions with untransformed cells in the tumour microenvironment (TME), including cancer-associated fibroblasts (CAFs), which promote blood supply, tumour progression, and immune evasion. Eph receptor tyrosine kinases are cell guidance receptors that are most active during development but re-emerge in cancer and are recognised drug targets. EphA3 is overexpressed in a wide range of tumour types, and we previously found expression particularly in stromal and vascular tissues of the TME. To investigate its role in the TME, we generated transgenic mice with inducible shRNA-mediated knockdown of EphA3 expression. EphA3 knockdown was confirmed in aortic mesenchymal stem cells (MSCs), which displayed reduced angiogenic capacity. In mice with syngeneic lung tumours, EphA3 knockdown reduced vasculature and CAF/MSC-like cells in tumours, and inhibited tumour growth, which was confirmed also in a melanoma model. Single cell RNA sequencing analysis of multiple human tumour types confirmed EphA3 expression in CAFs, including in breast cancer, where EphA3 was particularly prominent in perivascular- and myofibroblast-like CAFs. Our results thus indicate expression of the cell guidance receptor EphA3 in distinct CAF subpopulations is important in supporting tumour angiogenesis and tumour growth, highlighting its potential as a therapeutic target.

Erythropoietin-producing hepatocyte kinase receptor A1 facilitating the prgression of SGC-7901 cells and its transplanted tumor by increasing the expression of interleukin-6 and vascular endothelial growth factor in tumor microenvironment

Objectives

Many researches showed that Erythropoietin-producing hepatocyte kinase receptor A1 (EphA1) can promote the occurrence and development of malignant tumors and may be related to tumor microenvironment. But most of them are phenomenon studies, and there are few in-depth and complete mechanism studies. This study aims to understand how EphA1 promotes the progression of malignant tumors by regulating tumor microenvironment (focusing on Interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF)) from two experimental dimensions of in vitro and in vivo by using genetic engineering technology.

Material and Methods

We used genetic engineering technology to enhance and knock down EphA1 gene expression in SGC-7901 cells, respectively, and analyzed its influence on cell function and the expression levels of VEGF and IL-6 in cells. Subsequently, we constructed human EphA1 gene overexpression, EphA1 gene silencing, and normal expression of human EphA1 gene subcutaneous transplanted tumor models of SGC-7901 cells nude mice, and analyzed the differences in tumor development and the changes in the expression levels of VEGF and ILl-6 in tumor tissues.

Results

After EphA1 gene expression was enhanced, the proliferation, invasion and migration of SGC-7901 cells were enhanced, and apoptosis was weakened, and the expression levels of VEGF and IL-6 were increased. While the opposite results were found when EphA1 gene expression were knocked down. Meanwhile, tumor formation time and growth rate of subcutaneous transplantation in nude mice were advanced and the expression levels of VEGF and IL-6 in tumor tissues were increased when EphA1 gene expression were overexpressed by genetic engineering technology. Similarly, the opposite effect occurred in transplanted tumor model when EphA1 gene was silenced.

Conclusion

Our study showed that EphA1 can up-regulating VEGF and IL-6 expression, thereby enhancing the inflammatory environment and angiogenesis in the tumor microenvironment, and this helps to promote the progression of SGC-7901 cells and its transplanted tumor.

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.

Harnessing the Power of Eph/ephrin Biosemiotics for Theranostic Applications

Comprehensive basic biological knowledge of the Eph/ephrin system in the physiologic setting is needed to facilitate an understanding of its role and the effects of pathological processes on its activity, thereby paving the way for development of prospective therapeutic targets. To this end, this review briefly addresses what is currently known and being investigated in order to highlight the gaps and possible avenues for further investigation to capitalize on their diverse potential.

Association Between EphA1 and Tumor Microenvironment in Gastric Carcinoma and its Clinical Significance

BACKGROUND With the growing global burden of gastric carcinoma (GC) and the urgent need for biomolecular targeted therapies, this study aimed to elucidate the relationship between EphA1 and the tumor microenvironment (focusing primarily on the key inflammatory cytokines IL-6 and tumor angiogenic cytokine VEGF) to identify a new potential therapeutic target. MATERIAL AND METHODS IHC and qRT-PCR were performed to quantify the protein and gene expression levels of EphA1, IL-6, and VEGF in normal mucosal tissues, carcinoma tissues, and paracarcinomatous tissues from 57 GC patients. Spearman's rank correlation test was performed to determine the relationship between EphA1, IL-6, and VEGF expression levels. The relationships of EphA1 with clinicopathologic parameter and survival in GC patients were also evaluated. RESULTS The protein and gene expression levels of EphA1 were all attenuated gradually from carcinoma tissues to paracarcinomatous tissues and then to normal mucosal tissues in GC patients. Additionally, significant correlations between the overexpression of EphA1 with aggressive clinicopathological features and shorter survival time of GC patients were verified. In particular, we found a significant positive correlation between the expression of EphA1 and tumor microenvironment hallmark proteins IL-6 and VEGF in carcinoma tissues and paracarcinomatous tissues. CONCLUSIONS EphA1 can promote the occurrence and development of GC by its selective high expression in cancer tissues and its relationship with malignant clinical features and prognosis of GC patients. The underlying potential mechanism appears to involve enhancement of the tumor microenvironment, which via drives the expression of tumor microenvironment hallmark proteins IL-6 and VEGF.