Erythropoietin-Induced Activation of the JAK2/STAT5, PI3K/Akt, and Ras/ERK Pathways Promotes Malignant Cell Behavior in a Modified Breast Cancer Cell Line

Erythropoietin: A Personal Alice in Wonderland Trip in the Shadow of the Giants

The identification of the hormone erythropoietin (EPO), which regulates red blood cell production, and its development into a pharmaceutical-grade product to treat anemia has been not only a herculean task but it has also been the first of its kind. As with all the successes, it had "winners" and "losers", but its history is mostly told by the winners who, over the years, have published excellent scientific and divulgate summaries on the subject, some of which are cited in this review. In addition, "success" is also due to the superb and dedicated work of numerous "crew" members, who often are under-represented and under-recognized when the story is told and often have several "dark sides" that are not told in the polished context of most reviews, but which raised the need for the development of the current legislation on biotherapeutics. Although I was marginally involved in the clinical development of erythropoietin, I have known on a personal basis most, if not all, the protagonists of the saga and had multiple opportunities to talk with them on the drive that supported their activities. Here, I will summarize the major steps in the development of erythropoietin as the first bioproduct to enter the clinic. Some of the "dark sides" will also be mentioned to emphasize what a beautiful achievement of humankind this process has been and how the various unforeseen challenges that emerged were progressively addressed in the interest of science and of the patient's wellbeing.

Activating mutations in JAK2 and CALR differentially affect intracellular calcium flux in store operated calcium entry

BACKGROUND

Calcium (Ca2+) signaling regulates various vital cellular functions, including integrin activation and cell migration. Store-operated calcium entry (SOCE) via calcium release-activated calcium (CRAC) channels represents a major pathway for Ca2+ influx from the extracellular space in multiple cell types. The impact of JAK2-V617F and CALR mutations which are disease initiating in myeloproliferative neoplasms (MPN) on SOCE, calcium flux from the endoplasmic reticulum (ER) to the cytosol, and related key signaling pathways in the presence or absence of erythropoietin (EPO) or thrombopoietin (TPO) is poorly understood. Thus, this study aimed to elucidate the effects of these mutations on the aforementioned calcium dynamics, in cellular models of MPN.

METHODS

Intracellular Ca2+ levels were measured over a time frame of 0-1080 s in Fura-2 AM labeled myeloid progenitor 32D cells expressing various mutations (JAK2-WT/EpoR, JAK2-V617F/EpoR; CALR-WT/MPL, CALR-ins5/MPL, and del52/MPL). Basal Ca2+ concentrations were assessed from 0-108 s. Subsequently, cells were stimulated with EPO/TPO in Ca2+-free Ringer solution, measuring Ca2+ levels from 109-594 s (store depletion). Then, 2 mM of Ca2+ buffer resembling physiological concentrations was added to induce SOCE, and Ca2+ levels were measured from 595-1080 s. Fura-2 AM emission ratios (F340/380) were used to quantify the integrated Ca2+ signal. Statistical significance was assessed by unpaired Student's t-test or Mann-Whitney-U-test, one-way or two-way ANOVA followed by Tukey's multiple comparison test.

RESULTS

Following EPO stimulation, the area under the curve (AUC) representing SOCE significantly increased in 32D-JAK2-V617F cells compared to JAK2-WT cells. In TPO-stimulated CALR cells, we observed elevated Ca2+ levels during store depletion and SOCE in CALR-WT cells compared to CALR-ins5 and del52 cells. Notably, upon stimulation, key components of the Ca2+ signaling pathways, including PLCγ-1 and IP3R, were differentially affected in these cell lines. Hyper-activated PLCγ-1 and IP3R were observed in JAK2-V617F but not in CALR mutated cells. Inhibition of calcium regulatory mechanisms suppressed cellular growth and induced apoptosis in JAK2-V617F cells.

CONCLUSIONS

This report highlights the impact of JAK2 and CALR mutations on Ca2+ flux (store depletion and SOCE) in response to stimulation with EPO and TPO. The study shows that the JAK2-V617F mutation strongly alters the regulatory mechanism of EpoR/JAK2-dependent intracellular calcium balance, affecting baseline calcium levels, EPO-induced calcium entry, and PLCγ-1 signaling pathways. Our results reveal an important role of calcium flux in the homeostasis of JAK2-V617F positive cells.

Erythroid Cells as Full Participants in the Tumor Microenvironment

The tumor microenvironment is an important factor that can determine the success or failure of antitumor therapy. Cells of hematopoietic origin are one of the most important mediators of the tumor-host interaction and, depending on the cell type and functional state, exert pro- or antitumor effects in the tumor microenvironment or in adjacent tissues. Erythroid cells can be full members of the tumor microenvironment and exhibit immunoregulatory properties. Tumor growth is accompanied by the need to obtain growth factors and oxygen, which stimulates the appearance of the foci of extramedullary erythropoiesis. Tumor cells create conditions to maintain the long-term proliferation and viability of erythroid cells. In turn, tumor erythroid cells have a number of mechanisms to suppress the antitumor immune response. This review considers current data on the existence of erythroid cells in the tumor microenvironment, formation of angiogenic clusters, and creation of optimal conditions for tumor growth. Despite being the most important life-support function of the body, erythroid cells support tumor growth and do not work against it. The study of various signaling mechanisms linking tumor growth with the mobilization of erythroid cells and the phenotypic and functional differences between erythroid cells of different origin allows us to identify potential targets for immunotherapy.

The Emerging Roles and Mechanisms of PAQR3 in Human Cancer: Pathophysiology and Therapeutic Implications

Cancer was one of the common causes of death in the world, and it was increasing year by year. At present, Progestin and AdipoQ receptor family member 3 (PAQR3) was widely studied in cancer. It has been found that PAQR3 was down regulated in various cancers, such as the gastric cancer, osteosarcoma, glioma, hepatocellular carcinoma, acute lymphoblastic leukemia, laryngeal squamous cell carcinoma, esophageal cancer, breast cancer, non-small cell lung cancer, and colorectal cancer. The decreased expression of PAQR3 was associated with short overall survival and disease-free survival in patients with gastric cancer, hepatocellular carcinoma, laryngeal squamous cell carcinoma, esophageal cancer, breast cancer, and non-small cell lung cancer. PAQR3 could inhibit cancer progression by using the Ras/Raf/MEK/ERK, PI3/AKT, EMT and other mechanisms, and was negatively regulated by the miR-543, miR-15b-5p and miR-15b. The roles and signaling mechanisms of PAQR3, and the relationship between the expression of PAQR3 and prognosis in cancer progression are reviewed in this article, and provides new tumor marker and idea to guide cancer treatment.

Correlation analysis of hemoglobin, albumin, lymphocyte, platelet score and platelet to albumin ratio and prognosis in patients with lung adenosquamous carcinoma

Objective

To investigate the effect of hemoglobin, albumin, lymphocytes, platelet (HALP) score and platelet to albumin ratio (PAR) on prognosis of patients with lung adenosquamous carcinoma (ASC) after surgery.

Patients and methods

A total of 52 patients diagnosed with ASC after surgical resection were collected from Nanjing Chest Hospital from 2012 to 2021, and their general clinical data, pathological data and laboratory indexes were collected. The changes of Alb and Plt levels before and after surgery, HALP scores (hemoglobin albumin lymphocytes/platelets), and postoperative PAR, PLR, NLR were retrospectively analyzed, and their influence on the prognosis of patients with ASC was investigated. The cut-off value of △Alb, △Plt, postoperative PAR, PLR and NLR were determined by the receiver operating characteristic (ROC) curve, the optimal cut-off value of HALP score before and after surgery was calculated by using X-tile software, and the clinicopathological characteristics were compared between the high PAR and low PAR groups and between high HALP score and low HALP score group to analyze the factors influencing the prognosis of patients with ASC. Univariate and multivariate Cox proportional regression analyses were used to assess independent risk factors affecting overall survival (OS) and disease-free survival (DFS) in patients with ASC. Kaplan-Meier method was used to evaluate the correlation between OS, DFS and PAR and HALP score.

Results

A critical value of PAR was 7.40×10^9 and an area under the curve (AUC) of 0.737 (95%CI: 0.597-0.876, P = 0.004). The best cut-off value of the preoperative HALP score was 24.3. Univariate Cox analysis showed that the cut margin (P = 0.013), the degree of differentiation (P = 0.021), N stage (P = 0.049), △Plt (P = 0.010), △Alb (P = 0.016), PAR (P = 0.003), NLR (P = 0.025), PLR (P = 0.029), preoperative HALP score (P = 0.000) and post-operative HALP score (P = 0.010) were all associated with postoperative OS in ASC patients. Cut margin (P = 0.029), the degree of differentiation (P = 0.045), maximum tumor diameter (P = 0.018), N stage (P = 0.035), △Plt (P = 0.007), △Alb (P = 0.007), PAR (P = 0.004), NLR (P = 0.041), PLR (P = 0.030), preoperative HALP score (P = 0.000), and postoperative HALP score (P = 0.011) were related to postoperative DFS in ASC patients. Multivariate analysis revealed that PAR (HR: 6.877, 95%CI: 1.817-26.038, P = 0.005), differentiation degree (HR: 0.059, 95%CI: 0.006-0.591, P = 0.016) and preoperative HALP score (HR: 0.224, 95%CI: 0.068-0.733, P = 0.013) had significant effect on OS. Tumor maximum diameter (HR: 3.442, 95%CI: 1.148-10.318, P = 0.027) and preoperative HALP score (HR: 0.268, 95%CI: 0.085-0.847, P = 0.025) had significant influence on DFS.

Conclusion

PAR and preoperative HALP score were potentially useful biomarkers for evaluating the outcome of patients with postoperative ASC. PAR, the degree of differentiation and preoperative HALP score were independent prognostic factors for postoperative OS in ASC patients. Maximum tumor diameter and preoperative HALP score were independent prognostic factors for postoperative DFS in ASC patients.

Differentially Expressed Genes Induced by Erythropoietin Receptor Overexpression in Rat Mammary Adenocarcinoma RAMA 37-28 Cells

The erythropoietin receptor (EPOR) is a transmembrane type I receptor with an essential role in the proliferation and differentiation of erythroid progenitors. Besides its function during erythropoiesis, EPOR is expressed and has protective effect in various non-hematopoietic tissues, including tumors. Currently, the advantageous aspect of EPOR related to different cellular events is still under scientific investigation. Besides its well-known effect on cell proliferation, apoptosis and differentiation, our integrative functional study revealed its possible associations with metabolic processes, transport of small molecules, signal transduction and tumorigenesis. Comparative transcriptome analysis (RNA-seq) identified 233 differentially expressed genes (DEGs) in EPOR overexpressed RAMA 37-28 cells compared to parental RAMA 37 cells, whereas 145 genes were downregulated and 88 upregulated. Of these, for example, GPC4, RAP2C, STK26, ZFP955A, KIT, GAS6, PTPRF and CXCR4 were downregulated and CDH13, NR0B1, OCM2, GPM6B, TM7SF3, PARVB, VEGFD and STAT5A were upregulated. Surprisingly, two ephrin receptors, EPHA4 and EPHB3, and EFNB1 ligand were found to be upregulated as well. Our study is the first demonstrating robust differentially expressed genes evoked by simple EPOR overexpression without the addition of erythropoietin ligand in a manner which remains to be elucidated.

Synergistic Effect in Neurological Recovery via Anti-Apoptotic Akt Signaling in Umbilical Cord Blood and Erythropoietin Combination Therapy for Neonatal Hypoxic-Ischemic Brain Injury

Our previous clinical studies demonstrated the synergistic therapeutic effect induced by co-administering recombinant human erythropoietin (rhEPO) in human umbilical cord blood (hUCB) therapy for children with cerebral palsy. However, the cellular mechanism beyond the beneficial effects in this combination therapy still needs to be elucidated. A hypoxic–ischemic encephalopathy (HIE) model of neonates, representing cerebral palsy, was prepared and randomly divided into five groups (hUCB+rhEPO combination, hUCB, and rhEPO treatments over HIE, HIE control, and sham). Seven days after, hUCB was administered intraperitoneally and the rhEPO injections were started. Neurobehavioral tests showed the best outcome in the combination therapy group, while the hUCB and rhEPO alone treatments also showed better outcomes compared with the control (p < 0.05). Inflammatory cytokines were downregulated by the treatments and attenuated most by the combination therapy (p < 0.05). The hUCB+rhEPO treatment also showed remarkable increase in phosphorylation of Akt and potentiation of anti-apoptotic responses with decreased Bax and increased Bcl-2 (p < 0.05). Pre-treatment of MK-2206, an Akt inhibitor, for the combination therapy depressed the anti-apoptotic effects. In conclusion, these findings suggest that the therapeutic effect of hUCB therapy might be potentiated by co-administration of rhEPO via augmentation of anti-inflammatory and anti-apoptotic responses related to the phosphorylation of Akt.

Dapagliflozin attenuates diabetic cardiomyopathy through erythropoietin up-regulation of AKT/JAK/MAPK pathways in streptozotocin-induced diabetic rats

PURPOSE

This study was designed to investigate the mechanism of Dapagliflozin (Dapa) cardioprotection against diabetic cardiomyopathy (DCM). Structural and functional changes in the heart as well as decrease of erythropoietin (EPO) levels were reported in DCM. EPO simultaneously activates three pathways: the Janus-activated kinase-signal transducer and activator of transcription (JAK2/STAT5), phosphatidylinositol-3-kinase-Akt (PI3K/Akt), and extracellular signal-related kinase (ERK/MAPK) cascades, that result in proliferation and differentiation of cardiac cells.

METHODS AND RESULTS

DCM was induced by a high fat diet for 10 weeks followed by administration of streptozotocin. After confirmation of diabetes, rats were divided randomly to 5 groups: Group 1; normal control group, Group 2; untreated diabetic group and Groups (3-5); diabetic groups received Dapa daily (0.75 mg, 1.5 or 3 mg/Kg, p.o) respectively for a month. At the end of the experiment, full anaesthesia was induced in all rats using ether inhalation and ECG was recorded. Blood samples were collected then rats were sacrificed and their heart were dissected out and processed for biochemical and histopathological studies. Untreated diabetic rats showed abnormal ECG pattern, elevation of serum cardiac enzymes, decrease EPO levels, downregulation of P-Akt, P-JAK2 and pMAPK pathways, abnormal histological structure of the heart and increase immunostaining intensity of P53 and TNF α in the cardiomyocytes. Dapa in a dose dependent manner attenuated the alterations in the previously mentioned parameters.

CONCLUSION

The cardioprotective effect of Dapa could be mediated by increasing EPO levels and activation of P-Akt, P-JAK2 and pMAPK signalling cascades which in turn decrease apoptosis.

STAT5 as a Key Protein of Erythropoietin Signalization

Erythropoietin (EPO) acts on multiple tissues through its receptor EPOR, a member of a cytokine class I receptor superfamily with pleiotropic effects. The interaction of EPO and EPOR triggers the activation of several signaling pathways that induce erythropoiesis, including JAK2/STAT5, PI3K/AKT, and MAPK. The canonical EPOR/JAK2/STAT5 pathway is a known regulator of differentiation, proliferation, and cell survival of erythroid progenitors. In addition, its role in the protection of other cells, including cancer cells, is under intense investigation. The involvement of EPOR/JAK2/STAT5 in other processes such as mRNA splicing, cytoskeleton reorganization, and cell metabolism has been recently described. The transcriptomics, proteomics, and epigenetic studies reviewed in this article provide a detailed understanding of EPO signalization. Advances in this area of research may be useful for improving the efficacy of EPO therapy in hematologic disorders, as well as in cancer treatment.

Treatment of anemia in difficult-to-manage patients with chronic kidney disease

The management of anemia of chronic kidney disease (CKD) is often challenging. In particular, for patients with underlying inflammation, comorbid type 2 diabetes or cancer, those hospitalized, and recipients of a kidney transplant, the management of anemia may be suboptimal. Responsiveness to iron and/or erythropoiesis-stimulating agents, the mainstay of current therapy, may be reduced and the risk of adverse reactions to treatment is increased in these difficult-to-manage patients with anemia of CKD. This review discusses the unique patient and disease characteristics leading to complications and suboptimal treatment response. New treatment options in clinical development, such as hypoxia-inducible factor-prolyl hydroxylase (HIF-PH) inhibitors, may be particularly useful for difficult-to-treat patients. In clinical studies, HIF-PH inhibitors provided increased hemoglobin levels and improved iron utilization in anemic patients with non-dialysis-dependent and dialysis-dependent CKD, and preliminary data suggest that HIF-PH inhibitors may be equally effective in patients with or without underlying inflammation. The availability of new treatment options, including HIF-PH inhibitors, may improve treatment outcomes in difficult-to-manage patients with anemia of CKD.

Erythropoietin Signaling in the Microenvironment of Tumors and Healthy Tissues

Erythropoietin (EPO), the primary cytokine of erythropoiesis, stimulates both proliferation and differentiation of erythroid progenitors and their maturation to red blood cells. Basal EPO levels maintain the optimum levels of circulating red blood cells. However, during hypoxia, EPO secretion and its expression is elevated drastically in renal interstitial fibroblasts, thereby increasing the number of erythroid progenitors and accelerating their differentiation to mature erythrocytes. A tight regulation of this pathway is therefore of paramount importance. The biological response to EPO is commenced through the involvement of its cognate receptor, EPOR. The receptor-ligand complex results in homodimerization and conformational changes, which trigger downstream signaling events and cause activation or inactivation of critical transcription factors that promote erythroid expansion. In recent years, recombinant human EPO (rEPO) has been widely used as a therapeutic tool to treat a number of anemias induced by infection, and chemotherapy for various cancers. However, several studies have uncovered a tumor promoting ability of EPO in man, which likely occurs through EPOR or alternative receptor(s). On the other hand, some studies have demonstrated a strong anticancer activity of EPO, although the mechanism still remains unclear. A thorough investigation of EPOR signaling could yield enhanced understanding of the pathobiology for a variety of disorders, as well as the potential novel therapeutic strategies. In this chapter, in addition to the clinical relevance of EPO/EPOR signaling, we review its anticancer efficacy within various tumor microenvironments.

Kidney-secreted erythropoietin lowers lipidemia via activating JAK2-STAT5 signaling in adipose tissue

Background

Dyslipidemia is commonly observed in various kidney diseases, renal specific secreted erythropoietin (EPO) may participate in this process. However, how this process is regulated remains elusive.

Method

Dyslipidemia was evaluated in chronic kidney disease and ischemia kidney injury animal model. Primary cultured adipocytes were harvested to investigate the lipid metabolic effect of EPO. Lipidemia was evaluated in EPO treated animals. Blood samples from cardiac surgery-induced kidney injury patient were collected to assess correlationship between EPO and lipidemia.

Findings

We found a decrease in secreted EPO and hypertriglyceridemia in chronic kidney disease (CKD) mice. In contrast, in renal ischemia animal model, increased EPO triggered by hypoxia signaling activation, was accompanied by decreased triglyceride (TG) in serum. Mechanistically, circulating EPO modulated JAK2-STAT5 signaling, which in turn enhanced lipid catabolism in peripheral adipose tissue and contributed to dysregulated lipidemia. Delivering of recombinant EPO into both wild type and CKD mice suppressed TG in serum by accelerating lipid catabolism in adipose tissue. In a cohort of patients diagnosed with acute kidney injury after cardiopulmonary bypass surgery, the decreased TG and cholesterol negatively correlated with increased EPO in serum.

Interpretation

This study depicted a new mechanism by which renal secreted EPO controlled lipidemia in kidney diseases including chronic kidney disease. Circulating EPO stimulated lipid catabolism by targeting JAK2-STATA5 signaling in peripheral adipose tissue, providing new therapeutic target for dyslipidemia treatment.

Funding

This work was supported by grants from the National Natural Science Foundation of China (Nos. 81700640 and 81970608).

Identification and transcriptome analysis of erythroblastic island macrophages

The erythroblastic island (EBI), composed of a central macrophage and surrounding erythroid cells, was the first hematopoietic niche discovered. The identity of EBI macrophages has thus far remained elusive. Given that Epo is essential for erythropoiesis and that Epor is expressed in numerous nonerythroid cells, we hypothesized that EBI macrophages express Epor so that Epo can act on both erythroid cells and EBI macrophages simultaneously to ensure efficient erythropoiesis. To test this notion, we used Epor-eGFPcre knockin mouse model. We show that in bone marrow (BM) and fetal liver, a subset of macrophages express Epor-eGFP. Imaging flow cytometry analyses revealed that >90% of native EBIs comprised F4/80⁺Epor-eGFP⁺ macrophages. Human fetal liver EBIs also comprised EPOR⁺ macrophages. Gene expression profiles of BM F4/80⁺Epor-eGFP⁺ macrophages suggest a specialized function in supporting erythropoiesis. Molecules known to be important for EBI macrophage function such as Vcam1, CD169, Mertk, and Dnase2α were highly expressed in F4/80⁺Epor-eGFP⁺ macrophages compared with F4/80⁺Epor-eGFP^- macrophages. Key molecules involved in iron recycling were also highly expressed in BM F4/80⁺Epor-eGFP⁺ macrophages, suggesting that EBI macrophages may provide an iron source for erythropoiesis within this niche. Thus, we have characterized EBI macrophages in mouse and man. Our findings provide important resources for future studies of EBI macrophage function during normal as well as disordered erythropoiesis in hematologic diseases such as thalassemia, polycythemia vera, and myelodysplastic syndromes.

Methylation of the first exon in the erythropoietin receptor gene does not correlate with its mRNA and protein level in cancer cells

Background

Erythropoietin receptor (EPOR) is a functional membrane-bound cytokine receptor. Erythropoietin (EPO) represents an important hematopoietic factor for production, maturation and differentiation of erythroid progenitors. In non-hematopoietic tissue, EPO/EPOR signalization could also play cytoprotective and anti-apoptotic role. Several studies identified pro-stimulating EPO/EPOR effects in tumor cells; however, numerous studies opposed this fact due to the usage of unspecific EPOR antibodies and thus potential absence or very low levels of EPOR in tumor cells. It seems that this problem is more complex and therefore we have decided to focus on EPOR expression at several levels such as the role of methylation in the regulation of EPOR expression, identification of possible EPOR transcripts and the presence of EPOR protein in selected tumor cells.

Methods

Methylation status was analysed by bisulfite conversion reaction, PCR and sequencing. The expression of EPOR was monitored by quantitative RT-PCR and western blot analysis.

Results

In this study we investigated the methylation status of exon 1 of EPOR gene in selected human cancer cell lines. Our results indicated that CpGs methylation in exon 1 do not play a significant role in the regulation of EPOR transcription. However, methylation status of EPOR exon 1 was cell type dependent. We also observed the existence of two EPOR splice variants in human ovarian adenocarcinoma cell line - A2780 and confirmed the expression of EPOR protein in these cells using specific A82 anti-EPOR antibody.

Conclusion

We outlined the methylation status of all selected cancer cell lines in exon 1 of EPOR gene and these results could benefit future investigations. Moreover, A82 antibody confirmed our previous results demonstrating the presence of functional EPOR in human ovarian adenocarcinoma A2780 cells.

Role of bone marrow derived mesenchymal stromal cells and Schwann-like cells transplantation on spinal cord injury in adult male albino rats

BACKGROUND

Spinal cord injury is a considerable health impact accompanied with physical, psychological and economic burden. Bone marrow derived mesenchymal stromal cells (BM-MSCs) transplantation was found to produce neuronal regenerative effects. Schwann-like cells differentiated from BM-MSCs have myelin-forming ability.

AIM OF THE WORK

To compare the ability of BM-MSCs versus Schwann like cells to promote recovery of spinal cord injury.

MATERIAL AND METHODS

Adult male albino rats were used throughout the study. BM-MSCs were harvested from femora of rats. Sciatic nerves were extracted and used in the preparation of the induction culture medium for differentiation of BM-MSCs into Schwann-like cells. Rats were divided into control, spinal cord injured (SCI), spinal cord injured plus BM-MSCs transplantation (BM-MSC) and spinal cord injured plus Schwann-like cells transplantation (Sn) groups. BBB scale assessment was performed before and after SCI in all rats. Rats were euthanized at the end of the 7^th week and spinal cords were dissected and processed for light and transmission electron microscopic examinations.

RESULTS

Spinal cord sections of SCI group revealed cavitation, necrosis and demyelination. BM-MSC and Sn groups showed both functional and structural improvement compared to SCI group with better BBB score and histopathological features in the BM-MSC group and more expression of S100 in the Sn group.

CONCLUSION

Transplantation of BM-MSCs and Schwann-like cells improved the structural and functional alterations of spinal cord injury with better improvement in BM-MSC group.

Erythropoietin drives breast cancer progression by activation of its receptor EPOR

Breast cancer is a leading cause of cancer-related deaths. Anemia is common in breast cancer patients and can be treated with blood transfusions or with recombinant erythropoietin (EPO) to stimulate red blood cell production. Clinical studies have indicated decreased survival in some groups of cancer patients treated with EPO. Numerous tumor cells express the EPO receptor (EPOR), posing a risk that EPO treatment would enhance tumor growth, but the mechanisms involved in breast tumor progression are poorly understood.

Here, we have examined the functional role of the EPO-EPOR axis in pre-clinical models of breast cancer. EPO induced the activation of PI3K/AKT and MAPK pathways in human breast cancer cell lines. EPOR knockdown abrogated human tumor cell growth, induced apoptosis through Bim, reduced invasiveness, and caused downregulation of MYC expression. EPO-induced MYC expression is mediated through the PI3K/AKT and MAPK pathways, and overexpression of MYC partially rescued loss of cell proliferation caused by EPOR downregulation. In a xenotransplantation model, designed to simulate recombinant EPO therapy in breast cancer patients, knockdown of EPOR markedly reduced tumor growth.

Thus, our experiments in vitro and in vivo demonstrate that functional EPOR signaling is essential for the tumor-promoting effects of EPO and underline the importance of the EPO-EPOR axis in breast tumor progression.

Recombinant human erythropoietin stimulates melanoma tumor growth through activation of initiation factor eIF4E

Recombinant human erythropoietin (EPO) is standard treatment for anemia in cancer patients. Recent clinical trials suggest that EPO may accelerate tumor progression and increase mortality. However, the evidence supporting a growth-promoting effect of EPO has remained controversial. Employing an in vivo model of B16 murine melanoma, we observed that administration of EPO to tumor bearing C57BL/6 mice resulted in pronounced acceleration of melanoma growth. Our in vitro studies demonstrate that B16 murine melanoma cells express EPOR, both at the protein and mRNA levels. Interestingly, expression of EPOR was retained in the established tumors. EPO stimulation of B16 cells enhanced proliferation and protein synthesis rates, and correlated with activation of the receptor associated Janus kinase 2 (Jak2) as well as phosphorylation of extracellular signal–regulated kinase (Erk) 1/2 and Akt kinases. Treatment with EPO and Jak-2 antagonists significantly inhibited EPO-mediated B16 cell proliferation. Moreover, EPO dose-dependently induced the phosphorylation and activation of the translation initiation factor eIF4E as well as the phosphorylation of its repressor, the eIF4E binding protein 4E-BP1. Finally, using eIF4E small interfering RNA (siRNA), we observed that EPO-mediated stimulation of B16 cell proliferation is eIF4E-dependent. Our results indicate that EPO exerts a powerful stimulatory effect on cell proliferation and de novo protein synthesis in melanoma cells through activation of the initiation factor eIF4E.

Local blockage of self-sustainable erythropoietin signaling suppresses tumor progression in non-small cell lung cancer

Functional significance of co-expressed erythropoietin (EPO) and its receptor (EPOR) in non-small cell lung cancer (NSCLC) had been under debate. In this study, co-overexpression of EPO/EPOR was confirmed to be positively associated with poor survival in NSCLC. The serum EPO in 14 of 35 enrolled NSCLC patients were found elevated significantly and decreased to normal level after tumor resection. With primary tumor cell culture and patient-derived tumor xenograft (PDX) mouse model, the EPO secretion from the tumors of these 14 patients was verified. Then, we proved the patient derived serum EPO was functionally active and had growth promotion effect in EPO/EPOR overexpressed but not in EPO/EPOR under-expressed NSCLC cells. We also illustrated EPO promoted NSCLC cell proliferation through an EPOR/Jak2/Stat5a/cyclinD1 pathway. In xenograft mouse model, we proved local application of EPO neutralizing antibody and short hairpin RNA (shRNA) against EPOR effectively inhibited the growth of EPO/EPOR overexpressed NSCLC cells and prolonged survivals of the mice. Finally, EPO/EPOR/Jak2/Stat5a/cyclinD1 signaling was found to be a mediator of hypoxia induced growth in EPO/EPOR overexpressed NSCLC. Our results illustrated a subgroup of NSCLC adapt to hypoxia through self-sustainable EPO/EPOR signaling and suggest local blockage of EPO/EPOR as potential therapeutic method in this distinct NSCLC population.

Overexpression of the erythropoietin receptor in RAMA 37 breast cancer cells alters cell growth and sensitivity to tamoxifen

Erythropoietin (EPO) is the main regulator of erythropoiesis, and its receptor (EPOR) is expressed in various tissues, including tumors. Expression of EPOR in breast cancer tissue has been shown to correlate with expression of the estrogen receptor (ER). However, EPOR promotes proliferation in an EPO-independent manner. In patients with breast cancer, EPOR is associated with impaired tamoxifen response in ER-positive tumors, but not in ER-negative tumors. Furthermore, a positive correlation between EPOR/ER status and increased local cancer recurrence has been demonstrated, and EPOR expression is associated with G-protein coupled ER (GPER). Herein, we assessed the effects of EPOR on cell physiology and tamoxifen response in the absence of EPO stimulation using two cell lines that differ only in their EPOR expression status: RAMA 37 cells (low EPOR expression) and RAMA 37-28 cells (high EPOR expression). Alterations in cell growth, morphology, response to tamoxifen cytotoxicity, and EPOR-activated signal transduction were observed. RAMA 37 cells showed higher proliferation capacity without tamoxifen treatment, while RAMA 37-28 cells were more resistant to tamoxifen and proliferated more rapidly in the presence of tamoxifen. EPOR overexpression induced cell-morphology changes upon tamoxifen treatment, which resulted in the production of cell protrusions and subsequent cell death. Short-term treatment with tamoxifen (6 h) prompted RAMA 37 cells to acquired longer protrusions than RAMA 37-28 cells, which indicated a pre-apoptotic stage. Furthermore, prolonged treatment with tamoxifen (72 h) caused a greater reduction in RAMA 37 cell numbers, which indicated a higher rate of cell death. RAMA 37-28 cells showed prolonged activation of AKT signaling. We propose sustained AKT phosphorylation in EPOR-overexpressing cells as a mechanism that can lead to EPOR-induced tamoxifen resistance.

Erythropoietin Rescues Memory Impairment in a Rat Model of Chronic Cerebral Hypoperfusion via the EPO-R/JAK2/STAT5/PI3K/Akt/GSK-3β Pathway

Vascular dementia is the second most common cause of dementia in older people and is characterized by the sudden onset of impairments in thinking skills and behavior, which generally occur following a stroke. Unfortunately, effective therapy for vascular dementia remains inadequate. Erythropoietin (EPO) is a glycoprotein hormone that controls erythropoiesis, or red blood cell production. Recently, a prominent role for EPO has been defined in the nervous system, and there is growing interest in the potential therapeutic use of EPO for neuroprotection. However, whether it is protective from memory impairments and the underlying mechanisms of vascular dementia (VD) remains unknown. In the current study, we reported that supplements with exogenous erythropoietin (EPO) for 4 weeks could restore impaired memory in 2-vessel occlusion (2VO) rats, a well-established vascular dementia animal model. EPO also rescued impairments in dendritic spines and cholinergic dysfunctions in the hippocampus. Moreover, EPO suppressed the overactivation of GSK-3β in the hippocampus by stimulating the JAK2/STAT5/PI3K/Akt signal pathway. Furthermore, we found that genetic knockdown of the EPO receptor (EPO-R) by shRNA blocks the neuroprotection conferred by EPO on memory in VD. We hypothesized that EPO treatment is able to rescue the memory impairments in VD by stimulating the EPO-R/JAK2/STAT5/PI3K/Akt/GSK-3β pathway and suggest the potential usage of EPO in the therapy for VD.

Erythropoietin accelerates tumor growth through increase of erythropoietin receptor (EpoR) as well as by the stimulation of angiogenesis in DLD-1 and Ht-29 xenografts

Anemia is a relatively common symptom coexisting with colorectal carcinoma. Besides having a positive impact on hematological parameters, erythropoietin (Epo) has the serious adverse effect of promoting the neoplastic process. The role of Epo in colon cancer has not been clearly shown. The aim of this study was to assess the effects of Epo therapy on colorectal carcinoma cells both in in vitro and in animal models. Human colon adenocarcinoma cells DLD-1 and Ht-29 were cultured in medium with Epo beta in normoxia. Cell proliferation was measured with an automated cell counter. Expression of erythropoietin receptor (EpoR) mRNA, Akt mRNA, and their proteins were assessed by RT-PCR and confocal microscopy, respectively. Nude mice were inoculated with adenocarcinoma cells and treated with a therapeutic dose of Epo. Expression of EpoR, VEGF, Flt-1 and CD31 was evaluated in xenograft tumors. We identified that Epo through EpoR activates Akt, which promotes colon cancer cell growth and proliferation. Epo, and high levels of phosphorylated EpoR, directly accelerates tumor growth through its proliferative and proangiogenic effects. This study demonstrated that Epo had enhanced carcinogenesis through increase of EpoR and Flt-1 expression, and thereby contributed to tumor development. These results suggest that both EpoR-positive and EpoR-negative cancer cells could be regulated by exogenous Epo. However, an increased response to erythropoietin was observed in the EpoR-positive cells. Thus, erythropoietin increases the risk of tumor progression in colon cancer and should not be used to treat anemia in this type of cancer.

Erythropoietin protects neuroblastoma cells against etoposide and vincristine by activating ERK and AKT pathways but has no effect in kidney cells

AIMS

Chemotherapy induces anaemia in neuroblastoma patients. Cancer-associated anaemia may be treated with recombinant erythropoietin. However, the potential effects of erythropoietin on neuroblastoma and kidney cells have not been extensively evaluated. The present study was designed to investigate the effect of erythropoietin on the proliferation, and protection against vincristine- and etoposide-induced cell death in neuroblastoma (MSN), and embryonic kidney (HEK 293) cells.

MAIN METHODS

The expression of erythropoietin and its receptor in MSN and HEK 293 was analysed by RT-PCR, immunocytochemistry, and Western blotting. The effect of erythropoietin on cell viability and proliferation was evaluated by the MTT assay, and by the Click-iT EdU Alexa Fluor 647 kit, respectively. For the cyto-protective assays, cells were incubated with erythropoietin before etoposide and vincristine treatment. Activation of signalling pathways was studied by Western blotting.

KEY FINDINGS

MSN and HEK 293 cells expressed the erythropoietin receptor, but not erythropoietin. Erythropoietin induced proliferation and protection against vincristine and etoposide in MSN cells. HEK 293 cells were not affected by erythropoietin. Erythropoietin showed an anti-apoptotic effect which was dependent on the activation of ERK1/2 and AKT. HEK 293 cells presented constitutively phosphorylated AKT, and showed no activation of ERK1/2 upon erythropoietin stimulation.

SIGNIFICANCE

These results indicate that erythropoietin induces proliferation of MSN cells, and that it can ameliorate vincristine- and etoposide-induced apoptosis of these cells. Erythropoietin-mediated neuroprotection was regulated by the combined effect of the ERK1/2 and AKT signalling pathways. Our findings provide further insights into the potential effect of erythropoietin on neuroblastoma cells.

Ruta graveolens L. induces death of glioblastoma cells and neural progenitors, but not of neurons, via ERK 1/2 and AKT activation

Glioblastoma multiforme is a highly aggressive brain tumor whose prognosis is very poor. Due to early invasion of brain parenchyma, its complete surgical removal is nearly impossible, and even after aggressive combined treatment (association of surgery and chemo- and radio-therapy) five-year survival is only about 10%. Natural products are sources of novel compounds endowed with therapeutic properties in many human diseases, including cancer. Here, we report that the water extract of Ruta graveolens L., commonly known as rue, induces death in different glioblastoma cell lines (U87MG, C6 and U138) widely used to test novel drugs in preclinical studies. Ruta graveolens’ effect was mediated by ERK1/2 and AKT activation, and the inhibition of these pathways, via PD98058 and wortmannin, reverted its antiproliferative activity. Rue extract also affects survival of neural precursor cells (A1) obtained from embryonic mouse CNS. As in the case of glioma cells, rue stimulates the activation of ERK1/2 and AKT in A1 cells, whereas their blockade by pharmacological inhibitors prevents cell death. Interestingly, upon induction of differentiation and cell cycle exit, A1 cells become resistant to rue’s noxious effects but not to those of temozolomide and cisplatin, two alkylating agents widely used in glioblastoma therapy. Finally, rutin, a major component of the Ruta graveolens water extract, failed to cause cell death, suggesting that rutin by itself is not responsible for the observed effects. In conclusion, we report that rue extracts induce glioma cell death, discriminating between proliferating/undifferentiated and non-proliferating/differentiated neurons. Thus, it can be a promising tool to isolate novel drugs and also to discover targets for therapeutic intervention.

Germ-line PHD1 and PHD2 mutations detected in patients with pheochromocytoma/paraganglioma-polycythemia

We have investigated genetic/pathogenetic factors associated with a new clinical entity in patients presenting with pheochromocytoma/paraganglioma (PHEO/PGL) and polycythemia. Two patients without hypoxia-inducible factor 2α (HIF2A) mutations, who presented with similar clinical manifestations, were analyzed for other gene mutations, including prolyl hydroxylase (PHD) mutations. We have found for the first time a germ-line mutation in PHD1 in one patient and a novel germ-line PHD2 mutation in a second patient. Both mutants exhibited reduced protein stability with substantial quantitative protein loss and thus compromised catalytic activities. Due to the unique association of patients' polycythemia with borderline or mildly elevated erythropoietin (EPO) levels, we also performed an in vitro sensitivity assay of erythroid progenitors to EPO and for EPO receptor (EPOR) expression. The results show inappropriate hypersensitivity of erythroid progenitors to EPO in these patients, indicating increased EPOR expression/activity. In addition, the present study indicates that HIF dysregulation due to PHD mutations plays an important role in the pathogenesis of these tumors and associated polycythemia. The PHD1 mutation appears to be a new member contributing to the genetic landscape of this novel clinical entity. Our results support the existence of a specific PHD1- and PHD2-associated PHEO/PGL-polycythemia disorder.

KEY MESSAGE

• A novel germ-l i n e PHD1 mutation causing heochromocytoma/paraganglioma and polycythemia. • Increased EPOR activity and inappropriate hypersensitivity of erythroid progenitors to EPO.

Co-stimulation with stem cell factor and erythropoietin enhances migration of c-Kit expressing cervical cancer cells through the sustained activation of ERK1/2

The cytokines erythropoietin (Epo) and stem cell factor (SCF), coupled with the cooperation between their receptors (EpoR and c-Kit), are essential components of normal physiological erythropoiesis. In earlier studies, we demonstrated the expression of c-Kit and EpoR in cervical cancer cells. It was identified that SCF is a survival factor, whereas Epo promotes cell proliferation. Cooperation between EpoR and SCF in cervical cancer has rarely been studied, despite the fact that cell migration and anchorage independent growth are considered initial steps in metastasis. Thus, the aim of this study was to analyse the effect of SCF and Epo alone, or in combination, on the migration and anchorage independent growth of two cervical cancer-derived cell lines. First, we demonstrated the expression of EpoR and c-Kit in the cell lines. Next, we evaluated anchorage independent growth, and identified that Epo and SCF produced a modest number of colonies, whereas the combination Epo/SCF induced a significantly higher number of colonies. Migration was then evaluated in Boyden chambers. Co-stimulation with Epo/SCF induced a significantly higher number of migrating cells than either cytokine alone. SCF-, Epo- and Epo/SCF-induced migration was inhibited by blocking phosphorylation of Janus kinase 2 (JAK2). Accordingly, western blot analysis demonstrated that the JAK2/signal transducer and activator of transcription-5 (STAT5) axis was activated in all cases. By contrast, inhibition of extracellular signal-related kinase (ERK) 1/2 abrogated migration induced by SCF and Epo/SCF only. Concurrently, Epo induced a modest, transient activation of ERK1/2, whereas SCF and Epo/SCF prompted a strong, sustained phosphorylation of ERK1/2. The results from this study have revealed that co-stimulation with Epo/SCF promotes migration and anchorage independent cell growth, and that co-signalling from EpoR and c-Kit converge on JAK2/STAT5 activation. Furthermore, SCF- and Epo/SCF-induced migration depends on the sustained activation of ERK1/2. These results indicate that co-signalling from different cytokine receptors induces migration, and this suggests that migratory behaviour may be regulated by the cooperative activity of Epo and SCF in cells expressing their cognate receptors.

miR-223 is a coordinator of breast cancer progression as revealed by bioinformatics predictions

MicroRNAs are single-stranded non-coding RNAs that simultaneously down-modulate the expression of multiple genes post-transcriptionally by binding to the 3'UTRs of target mRNAs. Here we used computational methods to predict microRNAs relevant in breast cancer progression. Specifically, we applied different microRNA target prediction algorithms to various groups of differentially expressed protein-coding genes obtained from four breast cancer datasets. Six potential candidates were identified, among them miR-223, previously described to be highly expressed in the tumor microenvironment and known to be actively transferred into breast cancer cells. To investigate the function of miR-223 in tumorigenesis and to define its molecular mechanism, we overexpressed miR-223 in breast cancer cells in a transient or stable manner. Alternatively we overexpressed miR-223 in mouse embryonic fibroblasts or HEK293 cells and used their conditioned medium to treat tumor cells. With both approaches, we obtained elevated levels of miR-223 in tumor cells and observed decreased migration, increased cell death in anoikis conditions and augmented sensitivity to chemotherapy but no effect on adhesion and proliferation. The analysis of miR-223 predicted targets revealed enrichment in cell death and survival-related genes and in pathways frequently altered in breast cancer. Among these genes, we showed that protein levels for STAT5A, ITGA3 and NRAS were modulated by miR-223. In addition, we proved that STAT5A is a direct miR-223 target and highlighted a possible correlation between miR-223 and STAT5A in migration and chemotherapy response. Our investigation revealed that a computational analysis of cancer gene expression datasets can be a relevant tool to identify microRNAs involved in cancer progression and that miR-223 has a prominent role in breast malignancy that could potentially be exploited therapeutically.

Energy-sensitive regulation of Na+/K+-ATPase by Janus kinase 2

Janus kinase 2 (JAK2) contributes to intracellular signaling of leptin and erythropoietin, hormones protecting cells during energy depletion. The present study explores whether JAK2 is activated by energy depletion and regulates Na(+)/K(+)-ATPase, the major energy-consuming pump. In Jurkat cells, JAK2 activity was determined by radioactive kinase assay, phosphorylated JAK2 detected by Western blotting, ATP levels measured by luciferase assay, as well as Na(+)/K(+)-ATPase α1-subunit transcript and protein abundance determined by real-time PCR and Western blotting, respectively. Ouabain-sensitive K(+)-induced currents (Ipump) were measured by whole cell patch clamp. Ipump was further determined by dual-electrode voltage clamp in Xenopus oocytes injected with cRNA-encoding JAK2, active (V617F)JAK2, or inactive (K882E)JAK2. As a result, in Jurkat T cells, JAK2 activity significantly increased following energy depletion by sodium azide (NaN3) or 2,4- dinitro phenol (DNP). DNP- and NaN3-induced decrease of cellular ATP was significantly augmented by JAK2 inhibitor AG490 and blunted by Na(+)/K(+)-ATPase inhibitor ouabain. DNP decreased and AG490 enhanced Ipump as well as Na(+)/K(+)-ATPase α1-subunit transcript and protein abundance. The α1-subunit transcript levels were also enhanced by signal transducer and activator of transcription-5 inhibitor CAS 285986-31-4. In Xenopus oocytes, Ipump was significantly decreased by expression of JAK2 and (V617F)JAK2 but not of (K882E)JAK2, effects again reversed by AG490. In (V617F)JAK2-expressing Xenopus oocytes, neither DNP nor NaN3 resulted in further decline of Ipump. In Xenopus oocytes, the effect of (V617F)JAK2 on Ipump was not prevented by inhibition of transcription with actinomycin. In conclusion, JAK2 is a novel energy-sensing kinase that curtails energy consumption by downregulating Na(+)/K(+)-ATPase expression and activity.

CCL2 at the crossroad of cancer metastasis

Primary tumors can affect organ functions, either mechanically when they grow to a considerable size or via production of hormones. However, mortality of cancer patients is in most cases due to formation of secondary growths.(1) (,) (2) Consequently, various drugs are currently employed in clinical trials to impair specific steps of cancer metastasis such as mesenchymal or amoeboid cell migration, intravasation and/or colonization.(2) From the clinical point of view, targeting late metastatic processes such as extravasation or colonization might be required for cancer patients that bear already dormant micrometastases in their capillaries which have left behind earlier metastatic steps. Development of such drugs needs characterization of molecular targets implicated in distinct steps of cancer metastasis.

Role of arachidonic acid metabolism in Stat5 activation induced by oleic acid in MDA-MB-231 breast cancer cells

Epidemiological studies and animal models suggest an association between high levels of dietary fat intake and an increased risk of breast cancer. In breast cancer cells, the free fatty acid oleic acid (OLA) induces proliferation, migration, invasion and an increase of MMP-9 secretion. However, the role of OLA on Stat5 activation and the participation of COX-2 and LOXs activity in Stat5 activation induced by OLA remain to be investigated. We demonstrate here that stimulation of MDA-MB-231 breast cancer cells with 100 μM OLA induces Stat5 phosphorylation at Tyr-694 and an increase of Stat5-DNA complex formation. The Stat5 DNA-binding activity requires COX-2, LOXs, metalloproteinases and Src activities. In addition, OLA induces cell migration through a Stat5-dependent pathway. In summary, our findings establish that OLA induces cell migration through a Stat5-dependent pathway and that Stat5 activation requires AA metabolites in MDA-MB-231 breast cancer cells.

Recombinant human erythropoietin preconditioning attenuates liver ischemia reperfusion injury through the phosphatidylinositol-3 kinase/AKT/endothelial nitric oxide synthase pathway

BACKGROUND

The exact mechanism by which erythropoietin protects the liver from ischemia reperfusion (I/R) injury is not yet known. In the present study, we examined the role of protein kinase B (PKB/AKT) and endothelial nitric oxide synthase (eNOS) in the protective effect of recombinant human erythropoietin (rHuEPO) on I/R injury of the liver.

MATERIALS AND METHODS

We used a liver in situ I/R model. One hundred twenty adult male Sprague-Dawley rats were divided randomly into six groups. rHuEPO and (or) LY294002 were injected in the tail vein before the operation, and its effect was assessed by measuring the serum levels of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, nitric oxide (NO), and endothelin-1 (ET-1) and by histologic analysis. The expression of erythropoietin receptor (EPOR) and eNOS was measured by real-time polymerase chain reaction. Total AKT and eNOS and phosphorylated AKT and eNOS were examined by western blot.

RESULTS

rHuEPO dramatically attenuated the functional and morphologic injuries. The serum levels of alanine aminotransferase and lactate dehydrogenase were significantly decreased, but the amount of NO in the serum was increased in the I/R + rHuEPO group. Accordingly, rHuEPO administration significantly ameliorated the histologic damages at 6 h after reperfusion. rHuEPO significantly stimulated the phosphorylation of AKT and eNOS in the rats after liver I/R.

CONCLUSIONS

The protective effect of rHuEPO in I/R injury is mediated via the activation of the phosphatidylinositol-3 kinase/AKT/eNOS signaling pathway, at least in part, by increasing p-AKT and p-eNOS and leads to the maintenance of an elevated level of NO.

Erythropoietin receptor expression and its relationship with trastuzumab response and resistance in HER2-positive breast cancer cells

Resistance to trastuzumab is a major issue in the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Several potential resistance mechanisms have been investigated, but the results are controversial and no conclusion has been reached. Erythropoietin receptor (EPOR) may function in cell growth, and expressed in various cancer cells. Because the downstream signaling pathways for EPOR and HER2 partially overlapped, we hypothesized that EPOR may play a role in the inhibition effect of trastuzumab and resistance to trastuzumab. Here, we detected the expression of EPOR mRNA and protein in HER2-positive breast cancer cell lines and tissues. EPOR expressed in SKBR3, MDA-MB-453, and UACC-812 cell lines, but not in BT474. Of the 55 HER2-positive cancer tissues, EPOR was positive in 42 samples and highly expressed (H-score ≥ 25) in 24 by immunohistochemistry. The difference between EPOR expression and Ki67 index was significant (P = 0.033), and EPOR expression also positively correlated with higher pathological stage (Spearman correlation coefficient = 0.359; P = 0.007). Exogenous EPO antagonized trastuzumab-induced inhibition of cell proliferation in HER2/EPOR dual-positive breast cancer cells. We then exposed SKBR3 cells to trastuzumab for 4 months to obtain trastuzumab-resistant SKBR3 cell line, which demonstrated higher phosphorylated EPOR level, higher EPO expression and more extracellular secretion than non-resistant parental SKBR3 cells. Downregulation EPOR expression using short hairpin RNA resensitized trastuzumab-resistant cells to this drug, and SKBR3 cells with EPOR downregulation demonstrated attenuated trastuzumab resistance after the same resistance induction. EPOR downregulation plus trastuzumab produced a synergetic action in the inhibition of cell proliferation and invasion in SKBR3 and MDA-MB-453 cell lines. Therefore, EPOR expression may be involved in tumor progression and proliferation in HER2-positive breast cancer. EPO/EPOR contributes to the mechanism of trastuzumab resistance in SKBR3 cell lines, and EPOR downregulation can reverse the resistance to trastuzumab and increase the inhibition effect of this drug.

Characterization of the erythropoietin/erythropoietin receptor axis in a rat model of liver damage and cholangiocarcinoma development

It has been recently shown that the biological effects of erythropoietin (EPO) are not limited to the hematopoietic compartment but, as pleiotropic glycoprotein, this hormone can exert pro-angiogenic and tissue-protective functions also in a wide range of non-hematopoietic organs. The role of EPO and the effective functionality of its receptor in solid tumors are still a controversial point of debate. In the present work we analyzed the gene expression of EPO and its cognate receptor (EpoR) in a rat model of thioacetamide-induced damage and tumor. An analysis of the EPO/EpoR axis was also performed on human cholangiocarcinoma (CC) cell lines. A progressive increase of EPO and EpoR mRNA can already be observed during the fibrotic–cirrhotic development with a peak of expression rising at tumor formation (24.7 ± 9.9-fold increase and 15.5 ± 1.1-fold increase, respectively, for the two genes). Co-localization studies by immunofluorescence revealed hepatocytes in the regenerative cirrhotic nodules (Hep Par-1⁺) and in the dysplastic bile duct cells (CK19⁺) as the major EPO producers in this specific condition. The same cell populations, together with endothelial cells, exhibited an increased expression of EpoR, although all the non-parenchymal cell populations in the liver exhibited modest basal mRNA levels. Challenging human CC cells, Mz-Cha-2, with a combination of EPO and SCF resulted in a synergistic effect on the gene expression of EPO, CyclinD1 and PCNA. This study suggests that the autocrine and paracrine release of endogenous EPO in the microenvironment may contribute to the development and maintenance of the CC possibly in cooperation with other signaling pathways.

Erythropoietin-driven signalling and cell migration mediated by polyADP-ribosylation

Background:

Recombinant human erythropoietin (EPO) is the leading biotechnology engineered hormone for treatment of anaemia associated with chronic conditions including kidney failure and cancer. The finding of EPO receptors on cancer cells has raised the concern that in addition to its action in erythropoiesis, EPO may promote tumour cell growth. We questioned whether EPO-induced signalling and consequent malignant cell manifestation is mediated by polyADP-ribosylation.

Methods:

Erythropoietin-mediated PARP (polyADP-ribose polymerase-1) activation, gene expression and core histone H4 acetylation were examined in UT7 cells, using western blot analysis, RT–PCR and immunofluorescence. Erythropoietin-driven migration of the human breast epithelial cell line MDA-MB-435 was determined by the scratch assay and in migration chambers.

Results:

We have found that EPO treatment induced PARP activation. Moreover, EPO-driven c-fos and Egr-1 gene expression as well as histone H4 acetylation were mediated via polyADP-ribosylation. Erythropoietin-induced cell migration was blocked by the PARP inhibitor, ABT-888, indicating an essential role for polyADP-ribosylation in this process.

Conclusions:

We have identified a novel pathway by which EPO-induced gene expression and breast cancer cell migration are regulated by polyADP-ribosylation. This study introduces new possibilities regarding EPO treatment for cancer-associated anaemia where combining systemic EPO treatment with targeted administration of PARP inhibitors to the tumour may allow safe treatment with EPO, minimising its possible undesirable proliferative effects on the tumour.

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.

Contrasting effect of recombinant human erythropoietin on breast cancer cell response to cisplatin induced cytotoxicity

Background

Human recombinant erythropoietin (rHuEpo) that is used for the treatment of the chemotherapy-induced anaemia in cancer patients was shown to cause detrimental effects on the course of disease due to increased adverse events inflicting patient’s survival, potentially related to rHuEpo-induced cancer progression. In this study, we elucidate the effect of rHuEpo administration on breast cancer cell proliferation and gene expression after cisplatin (cDDP) induced cytotoxicity.

Materials and methods

Two breast carcinoma models, MCF-7 and MDA-MB-231 cell lines, were used differing in oestrogen (ER) and progesterone (PR) receptors and p53 status. Cells were cultured with or without rHuEpo for 24 h or 9 weeks and their growth characteristics after cDDP treatment were assessed together with expression of genes involved in the p53-signaling pathway.

Results

Short-term exposure of breast cancer cells to rHuEpo lowers their proliferation and reduces cDDP cytotoxic potency. In contrast, long-term exposure of MCF-7 cells to rHuEpo increases proliferation and predisposes MCF-7 cells to cDDP cytotoxicity, but has no effect on MDA-MB-231 cells. MDA-MB-231 cells show altered level of ERK phosphorylation, indicating involvement of MAPK signalling pathway. Gene expression analysis of p53-dependent genes and bcl-2 gene family members confirmed differences between long and short-term rHuEpo effects, indicating the most prominent changes in BCL2 and BAD expression.

Conclusions

Proliferation and survival characteristics of MCF-7 cells are reversely modulated by the length of the rHuEpo exposure. On the other hand, MDA-MB-231 cells are almost irresponsive to long-term rHuEpo, supposedly due to the mutated p53 and ER(+)/PR(−) status. The p53 and ER/PR status may predict tumour response on rHuEpo and cDDP treatment.

Evaluation of functional erythropoietin receptor status in skeletal muscle in vivo: acute and prolonged studies in healthy human subjects

BACKGROUND

Erythropoietin receptors have been identified in human skeletal muscle tissue, but downstream signal transduction has not been investigated. We therefore studied in vivo effects of systemic erythropoietin exposure in human skeletal muscle.

METHODOLOGY/PRINCIPAL FINDINGS

The protocols involved 1) acute effects of a single bolus injection of erythropoietin followed by consecutive muscle biopsies for 1-10 hours, and 2) a separate study with prolonged administration for 16 days with biopsies obtained before and after. The presence of erythropoietin receptors in muscle tissue as well as activation of Epo signalling pathways (STAT5, MAPK, Akt, IKK) were analysed by western blotting. Changes in muscle protein profiles after prolonged erythropoietin treatment were evaluated by 2D gel-electrophoresis and mass spectrometry. The presence of the erythropoietin receptor in skeletal muscle was confirmed, by the M20 but not the C20 antibody. However, no significant changes in phosphorylation of the Epo-R, STAT5, MAPK, Akt, Lyn, IKK, and p70S6K after erythropoietin administration were detected. The level of 8 protein spots were significantly altered after 16 days of rHuEpo treatment; one isoform of myosin light chain 3 and one of desmin/actin were decreased, while three isoforms of creatine kinase and two of glyceraldehyd-3-phosphate dehydrogenase were increased.

CONCLUSIONS/SIGNIFICANCE

Acute exposure to recombinant human erythropoietin is not associated by detectable activation of the Epo-R or downstream signalling targets in human skeletal muscle in the resting situation, whereas more prolonged exposure induces significant changes in the skeletal muscle proteome. The absence of functional Epo receptor activity in human skeletal muscle indicates that the long-term effects are indirect and probably related to an increased oxidative capacity in this tissue.

Darbepoetin-α promotes neovascularization and cell proliferation in established colorectal liver metastases

BACKGROUND

The erythropoietin-analogue darbepoetin-α (DPO) improves liver function and regeneration after hepatectomy (Phx), however, also enhances Phx-induced tumor cell engraftment and neovascularization. Because it is unknown whether DPO also enhances the growth of established tumors, we herein studied the effect of DPO on established colorectal liver metastases after Phx.

METHODS

CT26.WT cells were implanted into the liver of BALB/c mice. Five days after tumor establishment, animals underwent 50% Phx and received 10 μg/kgBW DPO or saline. Non-Phx animals with DPO or saline-treatment served as controls. Seven days after Phx tumors were analyzed regarding blood vessel formation, leukocyte adhesion, cell proliferation, apoptotic cell death, and growth using intravital fluorescence microscopy, histology, and immunohistochemistry.

RESULTS

The growth of established colorectal liver metastases was slightly stimulated after DPO-treatment in hepatectomized and non-hepatectomized animals. However, tumor vessel formation and tumor cell proliferation were significantly enhanced after DPO-treatment in hepatectomized and non-hepatectomized mice compared with controls. Apoptotic cell death and leukocyte-endothelial cell interaction were significantly reduced after DPO-treatment.

CONCLUSION

Our study indicates that DPO-treatment promotes neovascularization and cell proliferation in established colorectal liver metastases of hepatectomized and non-hepatectomized mice. DPO-application in patients with colorectal liver metastases might promote tumor progression and should therefore be avoided.

Signal transducer and activator of transcription 5 as a key signaling pathway in normal mammary gland developmental biology and breast cancer

STAT5 consists of two proteins, STAT5A/B, that impact mammary cell differentiation, proliferation, and survival. In normal development, STAT5 expression and activity are regulated by prolactin signaling with JAK2/ELF5, EGF signaling networks that include c-Src, and growth hormone, insulin growth factor, estrogen, and progesterone signaling pathways. In cancer, erythropoietin signaling can also regulate STAT5. Activation levels are influenced by AKT, caveolin, PIKE-A, Pak1, c-Myb, Brk, beta-integrin, dystroglycan, other STATs, and STAT pathway molecules JAK1, Shp2, and SOCS. TGF-β and PTPN9 can downregulate prolactin- and EGF-mediated STAT5 activation, respectively. IGF, AKT, RANKL, cyclin D1, BCL6, and HSP90A lie downstream of STAT5.

Erythropoietin ameliorates renal ischemia and reperfusion injury via inhibiting tubulointerstitial inflammation

BACKGROUND

Tubulointerstitial inflammation is the characteristics of renal ischemia reperfusion injury (IRI) that is inevitable in kidney transplantation. Erythropoietin (EPO) has recently been shown to have protective effects on renal IRI by anti-apoptosis and anti-oxidation. Here, the effect and mechanism of EPO on renal IRI were further investigated, with a focus on tubulointerstitial inflammation.

MATERIALS AND METHODS

Male Sprague-Dawley rats were administrated with saline or EPO prior to IRI induced by bilateral renal pedicle clamping. Twenty-four hours following reperfusion, the effects of EPO on renal IRI were assessed by renal function and structure, tubulointerstitial myeloperoxidase (MPO) positive neutrophils, and proinflammatory mediator gene expression. The translocation and activity of NF-κB in renal tissues were also evaluated.

RESULTS

Compared with control groups, the EPO treated group exhibited lower serum urea and creatinine levels, limited tubular necrosis with a lower score of renal histological lesion. MPO positive cells in the tubulointerstitial area were greatly increased by IRI, but significantly reduced by the treatment of EPO. The gene expression of proinflammatory cytokines (IL-1β, IL-6, IL-10, and TNF-α) and chemokine (MCP-1) was also significantly decreased by EPO. In addition, less activation and nuclear-translocation of NF-κB was observed in the kidney treated by EPO as well.

CONCLUSION

EPO improved renal function and structure in IRI rats via reducing neutrophils in the tubulointerstitium, the production of proinflammatory cytokines and chemokine, as well as the activation and nuclear-translocation of NF-κB. EPO may have potential clinical applications as an anti-inflammation agent clinically for a wide range of injury.

Wnt-β-catenin-Tcf-4 signalling-modulated invasiveness is dependent on osteopontin expression in breast cancer

Background:

We have previously demonstrated that Tcf-4 regulates osteopontin (OPN) in rat breast epithelial cells, Rama37. In this report, we have examined the importance of this regulation in human breast cancer.

Methods:

The regulatory roles of Tcf-4 on cell invasion and OPN expression were investigated. The mRNA expression of Tcf-4 and OPN, and survival of breast cancer patients were correlated.

Results:

Tcf-4 enhanced cell invasion in both MCF10AT and MDA MB 231 breast cancer cells by transcriptionally activating OPN expression. Osteopontin was activated by Wnt signalling in MDA MB 231 cells. Paradoxical results on Tcf-4-regulated OPN expression in MCF10AT (activation) and Rama37 (repression) cells were shown to be a result of differential Wnt signalling competency in MCF10AT and Rama37 cells. High levels of OPN and Tcf-4 mRNA expression were significantly associated with survival in breast cancer patients. Most importantly, Tcf-4-positive patients had a poorer prognosis when OPN was overexpressed, while OPN-negative patients had a better prognosis when Tcf-4 was overexpressed.

Conclusion:

Our results suggest that Tcf-4 can act as a repressor or activator of breast cancer progression by regulating OPN expression in a Wnt-dependent manner and that Tcf-4 and OPN together may be a novel prognostic indicator for breast cancer progression.

Protective effect of erythropoietin on myocardial infarction in rats by inhibition of caspase-12 expression

In the present study, the myocardial protective effects of erythropoietin (EPO) by inhibition of the expression of caspase-12 were investigated in a myocardial infarction rat model. Thirty male SD rats were divided into three groups: sham-operation group, myocardial infarction group and EPO treatment group. The myocardial infarction model was created by ligating the left anterior descending coronary artery. The EPO treatment group was established by injecting rh-EPO (1,000 IU/kg) intraperitoneally every day after the operation, and the other two groups were injected with sodium chloride. Four weeks after induction of myocardial infarction, the left ventricular diastolic pressure (LVDP) was tested by Langendorff apparatus and the pathological changes were analyzed by H&E staining. Caspase-12 expression in the left ventricular myocardium was also measured by immunohistochemistry. Four weeks after induction of myocardial infarction, the improvement in heart function in the EPO treatment group was more distinct compared to that of the myocardial infarction group; LVDP was higher in the EPO treatment group compared to the myocardial infarction group, but lower compared to the control group. H&E staining showed that the myocardial cells in the normal control group were aligned in order with a clear structure and were stained equably, while the myocardial cells in the myocardial infarction model rats lined up in disorder with an augmented cell body appearing to have many granules and interstitial fibrosis. Myocardial fibrosis and disorder were improved in the EPO treatment group. The expression of caspase-12 in the myocardial infarction group was also increased compared to the EPO treatment group rats. The results suggest that EPO improves heart function in myocardial infarction rats by down-regulating the expression of caspase-12, which may protect the myocardium by abrogating endoplasmic reticulum stress-mediated cardiomyocyte apoptosis and improving heart function.

Erythropoietin induces lymph node lymphangiogenesis and lymph node tumor metastasis

Cancer therapy often produces anemia, which is treated with erthropoietin (EPO) to stimulate erythrocyte production. However, concerns have recently arisen that EPO treatment may promote later tumor metastasis and mortality. The mechanisms underlying such effects are unknown, but it is clear that EPO has pleiotropic effects in cell types other than hematopoietic cells. In this study, we investigated how EPO affects lymphangiogenesis and lymph node tumor metastasis in mouse models of breast cancer and melanoma. In these models, EPO increased lymph node lymphangiogenesis and lymph node tumor metastasis in a manner associated with increased migration, capillary-like tube formation, and dose- and time-dependent proliferation of human lymphatic endothelial cells. EPO increased sprouting of these cells in a thoracic duct lymphatic ring assay. These effects were abrogated by cotreatment with specific inhibitors of phosphoinositide 3-kinase or mitogen-activated protein kinase, under conditions in which EPO increased Akt and extracellular signal-regulated kinase 1/2 phosphorylation. Intraperitoneal administration of EPO stimulated peritoneal lymphangiogenesis, and systemic treatment of EPO increased infiltration of CD11b(+) macrophages in tumor-draining lymph nodes. Finally, EPO increased VEGF-C expression in lymph node-derived CD11b(+) macrophages as well as in bone marrow-derived macrophages in a dose- and time-dependent manner. Our results establish that EPO exerts a powerful lymphangiogenic function and can drive both lymph node lymphangiogenesis and nodal metastasis in tumor-bearing animals.