Epo is involved in angiogenesis in human glioma

PTX3 mediates the infiltration, migration, and inflammation-resolving-polarization of macrophages in glioblastoma

Introduction

Pentraxin 3 (PTX3) is an essential regulator of the immune system. However, the immune‐modulatory role of PTX3 in the tumor microenvironment of glioma has not been elucidated.

Methods

The RNA seq samples were obtained from The Cancer Genome Atlas (TCGA) and the China Glioma Genome Atlas (CGGA) datasets. The single‐cell sequencing data of glioblastoma (GBM) samples were obtained from the Single Cell Portal platform (http://singlecell.broadinstitute.org). Immunohistochemistry was used to assess PTX3 expression, HAVCR2, PD‐1, PD‐L1, and CD276 in glioma sections from the Xiangya cohort (n = 60). Multiplex immunofluorescence staining of PTX3, CD68, and CD163 was performed in several solid cancer types, including GBM. HMC3 was cocultured with U251 and U87, and transwell assay and flow cytometry assay were performed to explore the migration and polarization activity of HMC3.

Results

PTX3 expression is significantly increased in GBM. PTX3 expression predicts worse survival in the Xiangya cohort. PTX3 is closely related to the expression of PD‐1, PD‐L1, CD276, and HAVCR2 in the tumor microenvironment. Additionally, PTX3 is involved in tumorigenic and immunogenic processes, especially the activity of macrophages based on various signaling pathways in cellular communications and critical transcription factors. Specifically, PTX3 actively mediates macrophages' infiltration, migration, and inflammation‐resolving‐polarization. PTX3 could also predict immunotherapy response.

Conclusion

PTX3 is critically involved in macrophage infiltration, migration, and inflammation‐resolving‐polarization and modulates an immunosuppressive microenvironment.

Dual Switch Mechanism of Erythropoietin as an Antiapoptotic and Pro-Angiogenic Determinant in the Retina

Constant or intense light degenerates the retina and retinal pigment epithelial cells. Light generates reactive oxygen species and nitric oxide leading to initial reactions of retinal degeneration. Apoptosis is the primary mechanism of abnormal death of photoreceptors, retinal ganglion cells, or retinal pigment epithelium (RPE) in degenerative retinal diseases, including diabetic retinopathy and age-related macular degeneration. The current study evaluated the function of erythropoietin (EPO) on angiogenesis and apoptosis in the retina and RPE under oxidative stress. We determined the pro-angiogenic and antiapoptotic mechanism of EPO under stress conditions using a conditional EPO knockdown model using siRNA, EPO addition, proteomics, immunocytochemistry, and bioinformatic analysis. Our studies verified that EPO protected retinal cells from light-, hypoxia-, hyperoxia-, and hydrogen peroxide-induced apoptosis through caspase inhibition, whereas up-regulated angiogenic reactions through vascular endothelial growth factor (VEGF) and angiotensin pathway. We demonstrated that the EPO expression in the retina and subsequent serine/threonine/tyrosine kinase phosphorylations might be linked to oxidative stress response tightly to determining angiogenesis and apoptosis. Neuroprotective roles of EPO may involve the balance between antiapoptotic and pro-angiogenic signaling molecules, including BCL-xL, c-FOS, caspase-3, nitric oxide, angiotensin, and VEGF receptor. Our data indicate a new therapeutic application of EPO toward retinal degeneration based on the dual roles in apoptosis and angiogenesis at the molecular level under oxidative stress.

Intussusceptive angiogenesis and its counterpart intussusceptive lymphangiogenesis

Intussusceptive angiogenesis (IA) is currently considered an important alternative and complementary form of sprouting angiogenesis (SA). Conversely, intussusceptive lymphangiogenesis (IL) is in an initial phase of study. We compare their morphofunctional characteristics, since many can be shared by both processes. To that end, the following aspects are considered: A) The concept of IA and IL as the mechanism by which blood and lymphatic vessels split, expand and remodel through transluminal pillar formations (hallmarks of intussusception). B) Terminology and historical background, with particular reference to the group of Burri, including Djonov and Patan, who initiated and developed the vessel intussusceptive concept in blood vessels. C) Incidence in normal (e.g. in the sinuses of developing lymph nodes) and pathologic conditions, above all in vessel diseases, such as dilated veins in hemorrhoidal disease, intravascular papillary endothelial hyperplasia (IPEH), sinusoidal hemangioma, lobular capillary hemangioma, lymphangiomas/lymphatic malformations and vascular transformation of lymph nodes. D) Differences and complementarity between vessel sprouting and intussusception. E) Characteristics of the cover (endothelial cells) and core (connective tissue components) of pillars and requirements for pillar identification. F) Structures involved in pillar formation, including endothelial contacts of opposite vessel walls, interendothelial bridges, merged adjacent capillaries, vessel loops and spilt pillars. G) Structures resulting from pillars with intussusceptive microvascular growth, arborization, remodeling and segmentation (compartmentalization). H) Influence of intussusception in the morphogenesis of vessel tumors/ pseudotumors; and I) Hemodynamic and molecular control of vessel intussusception, including VEGF, PDGF BB, Hypoxia, Notch, Endoglobin and Nitric oxide.

Vasculogenic Mimicry Formation Is Associated with Erythropoietin Expression but Not with Erythropoietin Receptor Expression in Cervical Squamous Cell Carcinoma

Background

Vasculogenic mimicry (VM), as an endothelium-independent cancer microcirculation, has been observed in many malignancies including cervical cancer. Erythropoietin (EPO) and erythropoietin receptor (EPO-R) could produce an angiogenic effect to promote cervical squamous cell carcinoma (CSCC) progression. However, the association between VM formation and EPO/EPO-R expression in CSCC is poorly explored.

Methods

Seventy-six paraffin-embedded CSCC samples, 25 high-grade squamous intraepithelial lesion (HSIL) samples, 20 low-grade squamous intraepithelial lesion (LSIL) samples, and 20 normal cervix samples were collected. Immunohistochemistry SP method was performed to detect EPO/EPO-R expression and CD31/periodic acid-Schiff (PAS) double staining was performed to detect VM formation. The associations of EPO/EPO-R and VM with clinicopathological parameters of CSCC were analyzed. The associations between VM formation and EPO/EPO-R expression were also analyzed.

Results

The positive expression rates of EPO and EPO-R were gradually increasing along the progression of normal cervix-LSIL-HSIL-CSCC sequence (P<0.05). EPO and EPO-R expression were not significantly associated with clinicopathological parameters of CSCC patients (P>0.05). VM was significantly associated with FIGO stage, lymphovascular space involvement, and lymph node metastasis (P<0.05). VM was positively associated with EPO expression (r=0.284, P<0.05) but was not associated with EPO-R expression (P>0.05).

Conclusion

These data suggest that increased EPO/EPO-R expression may play an important role in cervical carcinogenesis. EPO overexpression may promote VM formation in CSCC.

An injectable and thermosensitive hydrogel: Promoting periodontal regeneration by controlled-release of aspirin and erythropoietin

Periodontitis is an inflammatory disease induced by complex interactions between host immune system and plaque microorganism. Alveolar bone resorption caused by periodontitis is considered to be one of the main reasons for tooth loss in adults. To terminate the alveolar bone resorption, simultaneous anti-inflammation and periodontium regeneration is required, which has not appeared in the existing methods. In this study, chitosan (CS), β-sodium glycerophosphate (β-GP), and gelatin were used to prepare an injectable and thermosensitive hydrogel, which could continuously release aspirin and erythropoietin (EPO) to exert pharmacological effects of anti-inflammation and tissue regeneration, respectively. The releasing profile showed that aspirin and EPO could be continuously released from the hydrogels, which exhibited no toxicity both in vitro and in vivo, for at least 21 days. Immunohistochemistry staining and micro-CT analyses indicated that administration of CS/β-GP/gelatin hydrogels loaded with aspirin/EPO could terminate the inflammation and recover the height of the alveolar bone, which is further confirmed by histological observations. Our results suggested that CS/β-GP/gelatin hydrogels are easily prepared as drug-loading vectors with excellent biocompatibility, and the CS/β-GP/gelatin hydrogels loaded with aspirin/EPO are quite effective in anti-inflammation and periodontium regeneration, which provides a great potential candidate for periodontitis treatment in the dental clinic. Statement of Significance To terminate the alveolar bone resorption caused by periodontitis, simultaneous anti-inflammation and periodontium regeneration is required, which has not appeared in the existing methods. Here, (1) the chitosan (CS)/β-sodium glycerophosphate/gelatin hydrogels loaded with aspirin/erythropoietin (EPO) can form at body temperature in 5 min with excellent biocompatibility in vitro and in vivo; (2) The faster release of aspirin than EPO in the early stage is beneficial for anti-inflammation and provides a microenvironment for ensuring the regeneration function of EPO in the following step. In vivo experiments revealed that the hydrogels are effective in the control of inflammation and regeneration of the periodontium. These results indicate that our synthesized hydrogels have a great potential in the future clinical application.

TRIM8-driven transcriptomic profile of neural stem cells identified glioma-related nodal genes and pathways

BACKGROUND

We recently reported TRIM8, encoding an E3 ubiquitin ligase, as a gene aberrantly expressed in glioblastoma whose expression suppresses cell growth and induces a significant reduction of clonogenic potential in glioblastoma cell lines.

METHODS

we provided novel insights on TRIM8 functions by profiling the transcriptome of TRIM8-expressing primary mouse embryonal neural stem cells by RNA-sequencing and bioinformatic analysis. Functional analysis including luciferase assay, western blot, PCR arrays, Real time quantitative PCR were performed to validate the transcriptomic data.

RESULTS

Our study identified enriched pathways related to the neurotransmission and to the central nervous system (CNS) functions, including axonal guidance, GABA receptor, Ephrin B, synaptic long-term potentiation/depression, and glutamate receptor signalling pathways. Finally, we provided additional evidence about the existence of a functional interactive crosstalk between TRIM8 and STAT3.

CONCLUSIONS

Our results substantiate the role of TRIM8 in the brain functions through the dysregulation of genes involved in different CNS-related pathways, including JAK-STAT.

GENERAL SIGNIFICANCE

This study provides novel insights on the physiological TRIM8 function by profiling for the first time the primary Neural Stem Cell over-expressing TRIM8 by using RNA-Sequencing methodology.

Hematopoietic growth factors and tumor angiogenesis

Angiogenesis is regulated by numerous "classic" factors such as vascular endothelial growth factor (VEGF) and many other endogenous "non-classic"peptides, including erythropoietin (Epo), and granulocyte-/granulocyte macrophage colony stimulating factor (G-/GM-CSF). The latter play an important regulatory role in angiogenesis, especially under pathological conditions and constitute a crosslink between angiogenesis and hematopoiesis. This article reviews studies on the ability of hematopoietic cytokines to affect several endothelial cell functions in tumor angiogenesis. These findings in all these studies support the hypothesis formulated at the beginning of this century that a common ancestral cell, the hemangioblast, gives rise to cells of both the endothelial and the hematopoietic lineages.

Effects of over-expression of HIF-1alpha in bone marrow-derived mesenchymal stem cells on traumatic brain injury

Mesenchymal stem cells (MSCs) have been shown to play therapeutic effect in traumatic brain injury (TBI). To augment the therapeutic effect, MSCs could be engineered to over-express genes that are beneficial for treatment. In the present study, we over-expressed hypoxia inducible factor (HIF)-1alpha in bone marrow derived MSCs (BM-MSCs) and sought to investigate whether HIF-1alpha could enhance the therapeutic effect of MSCs in a mouse model of TBI. Balb/c mice were subjected to controlled cortical impact injury and MSCs were transplanted intravenously at 6 h after injury. The lesion volume and brain water content were measured and the neurological function was assessed by modified neurologic severity score tests. Double-labeled immunofluorescence for BrdU and NeuU was performed to determine angiogenesis and neurogenesis. The expression of erythropoietin (EPO) and vascular endothelial growth factor (VEGF) was measured by quantitative RT-PCR and western blotting. After TBI, mice received BM-MSCs over-expressing HIF-1alpha showed significantly more functional recovery, reduced brain damage, increased angiogenesis and neurogenesis and increased expression of VEGF and EPO, compared with control mice or mice treated with non-transduced BM-MSCs. Over-expression of HIF-1alpha enhanced BM-MSCs induced improvement of neurological recovery after TBI, by stimulating angiogenesis and neurogenesis.

Role of erythropoietin in the angiogenic activity of bone marrow endothelial cells of MGUS and multiple myeloma patients

Increasing evidences suggest several biological roles for erythropoietin and its receptor (Epo and EpoR), unrelated to erythropoiesis, including angiogenesis. Here, we detected the expression of EpoR in bone marrow-derived endothelial cells from monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) patients (MGECs and MMECs, respectively) and assessed whether Epo plays a role in MGECs- and MMECs-mediated angiogenesis. We show that EpoR is expressed by both MGECs and MMECs even though at a higher level in the first ones. Both EC types respond to rHuEpo in terms of cell proliferation, whereas other responses, including activation of JAK2/STAT5 and PI3K/Akt pathways, cell migration and capillarogenesis are enhanced by Epo in MGECs, but not in MMECs. In addition, the conditioned media of both Epo-treated cells induce a strong angiogenic response in vivo in the chorioallantoic membrane assay, comparable to that of vascular endothelial growth factor (VEGF). Overall, these data highlight the effect of Epo on MGECs- and MMECs-mediated angiogenesis: MGECs are more responsive to Epo treatment than MMECs, probably because over-angiogenic phenotype of MMECs is already activated by their autocrine/paracrine loops occurring in the “angiogenic switch” from MGUS.

Erythropoietin and Its Angiogenic Activity

Erythropoietin (EPO) is the main hematopoietic hormone acting on progenitor red blood cells via stimulation of cell growth, differentiation, and anti-apoptosis. However, its receptor (EPOR) is also expressed in various non-hematopoietic tissues, including endothelium. EPO is a pleiotropic growth factor that exhibits growth stimulation and cell/tissue protection on numerous cells and tissues. In this article we review the angiogenesis potential of EPO on endothelial cells in heart, brain, and leg ischemia, as well as its role in retinopathy protection and tumor promotion. Furthermore, the effect of EPO on bone marrow and adipose tissue is also discussed.

Erythropoietin Promotes Glioblastoma via miR-451 Suppression

Erythropoietin (EPO) is an erythropoiesis stimulating growth factor and hormone. EPO has been widely used in the treatment of chronic renal failure, cancer, and chemotherapy-related anemia for three decades. However, many clinical trials showed that EPO treatment may be associated with tumorigenesis and cancer progression. EPO is able to cross blood-brain barriers, and this may lead to an increased possibility of central nervous system tumors such as glioblastoma. Indeed, EPO promotes glioblastoma growth and invasion in animal studies. Additionally, EPO increases glioblastoma cell survival, proliferation, migration, invasion, and chemoresistancy in vitro. However, the exact mechanisms of cancer progression induced by EPO treatment are not fully understood. Posttranscriptional gene regulation through microRNAs may contribute to EPO's cellular and biological effects in tumor progression. Here, we aimed to study whether tumor suppressive microRNA, miR-451, counteracts the positive effects of EPO on U87 human glioblastoma cell line. Migration and invasion were evaluated by scratch assay and transwell invasion assay, respectively. We found that EPO decreased basal miR-451 expression and increased cell proliferation, migration, invasion, and cisplatin chemoresistancy in vitro. miR-451 overexpression by transfection of its mimic significantly reversed these effects. Furthermore, ectopic expression of miR-451 inhibited expression of its own target genes, such as metalloproteinases-2 and -9, which are stimulated by EPO treatment and involved in carcinogenesis processes, especially invasion. These findings suggest that miR-451 mimic delivery may be useful as adjuvant therapy in addition to chemotherapy and anemia treatment by EPO and should be tested in experimental glioblastoma models.

Far-western blotting as a solution to the non-specificity of the anti-erythropoietin receptor antibody

The erythropoietin receptor (EpoR) is a member of the cytokine receptor family. The interaction between erythropoietin (Epo) and EpoR is important for the production and maturation of erythroid cells, resulting in the stimulation of hematopoiesis. The fact that EpoR was also detected in neoplastic cells has opened the question about the relevance of anemia treatment with recombinant Epo in cancer patients. Numerous studies have reported pro-stimulating and anti-apoptotic effects of Epo in cancer cells, thus demonstrating EpoR functionality in these cells. By contrast, a previous study claims the absence of EpoR in tumor cells. This apparent discrepancy is based, according to certain authors, on the use of non-specific anti-EpoR antibodies. With the aim of bypassing the direct detection of EpoR with an anti-EpoR antibody, the present authors propose a far-western blot methodology, which in addition, confirms the interaction of Epo with EpoR. Applying this technique, the presence of EpoR and its interaction with Epo in human ovarian adenocarcinoma A2780 and normal human umbilical vein endothelial cells was confirmed. Furthermore, modified immunoprecipitation of EpoR followed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry analysis confirmed a 57 kDa protein as a human Epo-interacting protein in both cell lines.

Effects and mechanism of recombinant human erythropoietin on the growth of human breast cancer MDA-MB-231 cells in nude mice

This study aimed to explore the effects of recombinant human erythropoietin (rhEPO) on the growth of human breast cancer MDA-MB-231 cells in nude mice, and investigate its functions in regulating tumor growth, angiogenesis and apoptosis. A tumor-bearing nude mice model was established by subcutaneous injection of human breast cancer MDA-MB-231 cells. Two weeks later, the mice were randomly divided into four groups (n=6 for each group): negative control group, rhEPO group, EPO antibody group and EPO+EPO antibody group. Drugs were administered to the corresponding mice once every 3 days for five times. The size and weight of tumors were measured after the mice were sacrificed by cervical dislocation. The expression levels of EPO/EPOR, TNF-α, IL-10, and Bcl-2 in the tumor tissues were determined using RT-PCR and Western blot. The microvessel density (MVD) and expression of VEGF in the tumors were detected using immunohistochemistry. TUNEL assay was used to determine apoptosis in tumors. Results show that rhEPO significantly promoted the growth of MDA-MB-231 cells in nude mice (P<0.05). Compared with the negative control group, the expression levels of EPO, EPOR, TNF-α, IL-10, and VEGF, as well as the MVD values, were significantly elevated in the rhEPO group. However, the apoptotic index was significantly reduced (P<0.05). The ability of rhEPO to promote tumor growth may be associated with its functions in promoting microvessel formation and inhibiting tumor cell apoptosis.

Epoetin beta for the treatment of chemotherapy-induced anemia: an update

Epoetin beta belongs to the class of erythropoiesis-stimulating agents (ESAs) that are currently available to treat anemic patients receiving chemotherapy. Chemotherapy-induced anemia affects a high percentage of cancer patients and, due to its negative effects on disease outcome and the patient’s quality of life, should be treated when first diagnosed. Initial trials with ESAs have shown efficacy in improving quality of life and reducing the need for blood transfusions in patients with chemotherapy-induced anemia. However, recent meta-analyses have provided conflicting data on the impact of ESAs on survival and tumor progression. Here we provide an overview of these recent data and review the role of epoetin beta in the treatment of chemotherapy-induced anemia over the past 20 years.

Erythropoietin and cancer: the unintended consequences of anemia correction

Until 1990, erythropoietin (EPO) was considered to have a single biological purpose and action, the stimulation of red blood cell growth and differentiation. Slowly, scientific and medical opinion evolved, beginning with the discovery of an effect on endothelial cell growth in vitro and the identification of EPO receptors (EPORs) on neuronal cells. We now know that EPO is a pleiotropic growth factor that exhibits an anti-apoptotic action on numerous cells and tissues, including malignant ones. In this article, we present a short discussion of EPO, receptors involved in EPO signal transduction, and their action on non-hematopoietic cells. This is followed by a more detailed presentation of both pre-clinical and clinical data that demonstrate EPO’s action on cancer cells, as well as tumor angiogenesis and lymphangiogenesis. Clinical trials with reported adverse effects of chronic erythropoiesis-stimulating agents (ESAs) treatment as well as clinical studies exploring the prognostic significance of EPO and EPOR expression in cancer patients are reviewed. Finally, we address the use of EPO and other ESAs in cancer patients.

Erythropoietin, a novel versatile player regulating energy metabolism beyond the erythroid system

Erythropoietin (EPO), the required cytokine for promoting the proliferation and differentiation of erythroid cells to stimulate erythropoiesis, has been reported to act as a pleiotropic cytokine beyond hematopoietic system. The various activities of EPO are determined by the widespread distribution of its cell surface EPO receptor (EpoR) in multiple tissues including endothelial, neural, myoblasts, adipocytes and other cell types. EPO activity has been linked to angiogenesis, neuroprotection, cardioprotection, stress protection, anti-inflammation and especially the energy metabolism regulation that is recently revealed. The investigations of EPO activity in animals and the expression analysis of EpoR provide more insights on the potential of EPO in regulating energy metabolism and homeostasis. The findings of crosstalk between EPO and some important energy sensors and the regulation of EPO in the cellular respiration and mitochondrial function further provide molecular mechanisms for EPO activity in metabolic activity regulation. In this review, we will summarize the roles of EPO in energy metabolism regulation and the activity of EPO in tissues that are tightly associated with energy metabolism. We will also discuss the effects of EPO in regulating oxidative metabolism and mitochondrial function, the interactions between EPO and important energy regulation factors, and the protective role of EPO from stresses that are related to metabolism, providing a brief overview of previously less appreciated EPO biological function in energy metabolism and homeostasis.

Application of the chick embryo chorioallantoic membrane in neurosurgery disease

The chick embryo chorioallantoic membrane (CAM) is a highly vascularized extraembryonic membrane. Because of its ease of accessibility, extensive vascularization and immunodeficient environment, the CAM has been broadly used in the oncology, biology, pharmacy, and tissue regeneration research. The present review summarizes the application of the CAM in neurosurgery disease research. We focused on the use of the CAM as an assay for the research of glioma, vascular anomalies, Moyamoya Disease, and the blood-brain barrier.

Progress in detecting cell-surface protein receptors: the erythropoietin receptor example

Testing for the presence of specific cell-surface receptors (such as EGFR or HER2) on tumor cells is an integral part of cancer care in terms of treatment decisions and prognosis. Understanding the strengths and limitations of these tests is important because inaccurate results may occur if procedures designed to prevent false-negative or false-positive outcomes are not employed. This review discusses tests commonly used to identify and characterize cell-surface receptors, such as the erythropoietin receptor (EpoR). First, a summary is provided on the biology of the Epo/EpoR system, describing how EpoR is expressed on erythrocytic progenitors and precursors in the bone marrow where it mediates red blood cell production in response to Epo. Second, studies are described that investigated whether erythropoiesis-stimulating agents could stimulate tumor progression in cancer patients and whether EpoR is expressed and functional on tumor cells or on endothelial cells. The methods used in these studies included immunohistochemistry, Northern blotting, Western blotting, and binding assays. This review summarizes the strengths and limitations of these methods. Critically analyzing data from tests for cell-surface receptors such as EpoR requires understanding the techniques utilized and demonstrating that results are consistent with current knowledge about receptor biology.

Erythropoietin is involved in the angiogenic potential of bone marrow macrophages in multiple myeloma

Erythropoietin (Epo) is the crucial cytokine regulator of red blood cell production, and recombinant human erythropoietin (rHuEpo) is widely used in clinical practice for the treatment of anemia, primarily in kidney disease and in cancer. Increasing evidence suggests several biological roles for Epo and its receptor, Epo-R, unrelated to erythropoiesis, including angiogenesis. Epo-R has been found expressed in various non-haematopoietic cells and tissues, and in cancer cells. Here, we detected the expression of Epo-R in bone marrow-derived macrophages (BMMAs) from multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS) patients and assessed whether Epo/Epo-R axis plays a role in MM macrophage-mediated angiogenesis. We found that Epo-R is over-expressed in BMMAs from MM patients with active disease compared to MGUS patients. The treatment of BMMAs with rHuEpo significantly increased the expression and secretion of key pro-angiogenic mediators, such as vascular endothelial growth factor, hepatocyte growth factor and monocyte chemotactic protein (MCP-1/CCL-2), through activation of JAK2/STAT5 and PI3 K/Akt pathways. In addition, the conditioned media harvested from rHuEpo-treated BMMAs enhanced bone marrow-derived endothelial cell migration and capillary morphogenesis in vitro, and induced angiogenesis in the chorioallantoic membrane of chick embryos in vivo. Furthermore, we found an increase in the circulating levels of several pro-angiogenic cytokines in serum of MM patients with anemia under treatment with Epo. Our findings highlight the direct effect of rHuEpo on macrophage-mediated production of pro-angiogenic factors, suggesting that Epo/Epo-R pathway may be involved in the regulation of angiogenic response occurring in MM.

Human erythropoietin increases the pro-angiogenic potential of A2780 ovarian adenocarcinoma cells under hypoxic conditions

Erythropoietin (Epo) is a key regulator of erythroid cell proliferation, differentiation and apoptosis. In the form of the recombinant protein, it is widely used to treat various types of anemias, including that associated with cancer and with the myelosuppressive effects of chemotherapy, particularly platinum-based regimens. Our previous studies confirmed the presence of Epo receptors (EpoRs) in ovarian adenocarcinoma cell lines and demonstrated that long-term Epo treatment of A2780 cells resulted in the development of a phenotype exhibiting both enhanced Epo signaling and increased paclitaxel resistance. In the present study, we carried out a series of experiments to analyze the pro-angiogenic potential of Epo-treated A2780 and SKOV-3 cells. Our studies revealed that conditioned media of Epo-treated A2780 cells had a stimulative effect on human umbilical vein endothelial cells (HUVECs). This effect was only seen when A2780 cells were incubated under hypoxic conditions. Furthermore, Epo increased the secretion of interleukin (IL)-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-13, GM-CSF and interferon-γ by A2780 cells that grew in hypoxic conditions. In this regard, conditioned media of hypoxic and Epo-treated A2780 cells induced a significant phosphorylation of STAT-5 in HUVECs. Our results may have important implications for ovarian cancer patients receiving Epo.

Erythropoietin in cancer: a dilemma in risk therapy

Erythropoietin (EPO) is a frequently prescribed drug for treatment of cancer-related and chemotherapy-induced anemia in cancer patients. Paradoxically, recent preclinical and clinical studies indicate that EPO could potentially accelerate tumor growth and jeopardize survival in cancer patients. In this review I critically discuss the current knowledge and broad biological functions of EPO in association with tumor growth, invasion, and angiogenesis. The emphasis is focused on discussing the complex interplay between EPO and other tumor-derived factors in angiogenesis, tumor growth, invasion, and metastasis. Understanding the multifarious functions of EPO and its reciprocal relation with other signaling pathways is crucial for developing more effective agents for cancer therapy and for minimizing risks for cancer patients.

In vivo angiogenic activity of erythropoietin

The role of erythropoietin (Epo) has been demonstrated in tissues outside the hematopoietic system, including the cardiovascular system, where Epo promotes various effects in endothelial cells. Here, we have demonstrated the angiogenic capacity of recombinant human Epo (rhuEpo) in vivo, by means of the chick embryo chorioallantoic membrane (CAM) assay, a well-established in vivo assay to study angiogenesis and antiangiogenesis.

The effect of erythropoietin on normal and neoplastic cells

Erythropoietin (Epo) is an essential hormone that binds and activates the Epo receptor (EpoR) resident on the surface of erythroid progenitor cells, thereby promoting erythropoiesis. Recombinant human erythropoietin has been used successfully for over 20 years to treat anemia in millions of patients. In addition to erythropoiesis, Epo has also been reported to have other effects, such as tissue protection and promotion of tumor cell growth or survival. This became of significant concern in 2003, when some clinical trials in cancer patients reported increased tumor progression and worse survival outcomes in patients treated with erythropoiesis-stimulating agents (ESAs). One of the potential mechanisms proffered to explain the observed safety issues was that functional EpoR was expressed in tumors and/or endothelial cells, and that ESAs directly stimulated tumor growth and/or antagonized tumor ablative therapies. Since then, numerous groups have performed further research evaluating this potential mechanism with conflicting data and conclusions. Here, we review the biology of endogenous Epo and EpoR expression and function in erythropoiesis, and evaluate the evidence pertaining to the expression of EpoR on normal nonhematopoietic and tumor cells.

Epigenetic silencing of erythropoietin in human cancers

The glycoprotein hormone erythropoietin (EPO) is a key regulator in the production of red blood cells. EPO is produced mainly in the embryonic liver and kidney of adults. Other organs are also known to express varying amounts of EPO. In our study, we have analyzed the epigenetic regulation of EPO in human cancer cell lines by DNA methylation assays, chromatin immunoprecipitation, RT-PCR, and promoter analysis under different growth conditions. Moreover, the growth-related effects of ectopic EPO expression were analyzed in a head and neck cancer cell line. We found frequent DNA hypermethylation of the CpG island promoter and enhancer of EPO in different cancer cell lines. Aberrant methylation of EPO promoter was observed in primary lung, head and neck, breast, and liver cancers. Hypermethylation of EPO was associated with a decreased expression of EPO in cancer cells. Treatment of cancer cell lines with 5-aza-2'-deoxycytidine (Aza), an inhibitor of DNA methylation, reactivated EPO expression under hypoxia. In contrast, in the liver cancer cell line HepB3, the EPO promoter was unmethylated, and a high EPO expression was observed independently of Aza treatment. Moreover, in vitro hypermethylation of the EPO promoter and enhancer reduced expression of a reporter gene under normoxia and hypoxia. Induction of EPO under hypoxia was accompanied by increased histone H3 acetylation and reduced histone H3 lysine 9 trimethylation. In a head and neck cancer cell line, which exhibited low EPO levels, ectopic expression of EPO significantly enhanced proliferation under normoxia and hypoxia. In summary, we show that hypermethylation of regulatory sequences of EPO is frequently observed in tumors and that this aberrant methylation induces epigenetic silencing of EPO in cancer cells.

Intussusceptive microvascular growth in tumors

Intussusception is an alternative to the sprouting mode of angiogenesis. The advantage of this mechanism of vascular growth is that blood vessels are generated more rapidly and the capillaries thereby formed are less leaky. This review article summarizes our current knowledge concerning the role played by intussusceptive microvascular growth in tumor growth. Interestingly, an angiogenic switch from sprouting to intussusceptive angiogenesis occurs after treatment with angiogenesis inhibitors and may be considered as a tumor-protective adaptative response.

Co-expression of erythropoietin receptor with human epidermal growth factor 2 may counteract trastuzumab inhibition in gastric cancer

Gastric cancer has high prevalence and high modality worldwide. For many years, few improvements in the efficacy of treatments were reported for advanced gastric cancer settings. Although a novel molecular target agent trastuzumab, in combination with chemotherapy, prolongs overall survival time in advanced gastric cancer, resistance to this drug still exists among human epidermal growth factor receptor-2 (HER2) positive patients. HER2 and erythropoietin receptor (EPOR) downstream signaling pathway have some common factors like Akt, Erk and STATs. Also there exist evidences that EPOR may express on some solid tumors and probably promote tumor progression. So it is reasonable for us to hypothesis that HER2 and EPOR may be co-expressed in the same gastric cancer cell and if so, EPOR signaling pathway may overlaps that with HER2 and promotes HER2 induced signal transduction to cell proliferation. In clinical settings, a stimulation of EPOR will play antagonistic effects on trastuzumab-induced anti-tumor activity to HER2-positive gastric cancer patients. Co-expression of EPOR and HER2 is a predictive factor for resistance of trastuzumab in gastric cancer.