Erythropoietin inhibits apoptosis in breast cancer cells via an Akt-dependent pathway without modulating in vivo chemosensitivity

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.

RETRACTED: Effects of rehabilitation training on apoptosis of nerve cells and the recovery of neural and motor functions in rats with ischemic stroke through the PI3K/Akt and Nrf2/ARE signaling pathways

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and Academic Committee of Jiangsu Normal University (ACJSNU). ACJSNU informed the journal that they were aware of PubPeer comments of data fabrication and manipulation in Fig 4A, Fig 5A, Fig 7A + C as detailed here [https://pubpeer.com/publications/D732FA0F313382B58DD725C25A8AB9#3]. ACJSNU launched an investigation and invited two independent referees to review the issues raised on PubPeer and they agreed the paper displays signs of scientific fraud. An investigation made by Tangshan People's Hospital, concluded there are no researchers called Jun-Chang Wu and Gao-Zhou Tang in the hospital. ACJSNU requested that the corresponding authors of the paper provide the original experimental records and data for verification. However, the authors have been unable to address the above concerns, and have stated that the data were obtained from a third party which was not disclosed in the article. The National Natural Science Foundation of China has also investigated this paper and others by the corresponding authors [https://www.nsfc.gov.cn/publish/portal0/tab442/info85495.htm]. The Editor-in-Chief therefore no longer has confidence in the data presented and the conclusions of the article.

Erythropoietin suppresses the activation of pro-apoptotic genes in head and neck squamous cell carcinoma xenografts exposed to surgical trauma

Background

Several studies on the use of erythropoietin (Epo) to treat anaemia in patients undergoing cancer treatment have shown adverse effects on tumour control and survival. Experimental studies indicate that this could be linked to an interaction with wound healing processes and not an effect on tumour cells per se. We have previously shown that erythropoietin in combination with surgical trauma stimulates tumour growth. In the present study, we investigated the effect of surgery and Epo on gene expression.

Methods

Human tumours from oral squamous cell cancer were xenotransplanted to nude mice treated with Epo. The tumours were then transected in a standardised procedure to mimic surgical trauma and the change in gene expression of the tumours was investigated by microarray analysis. qRT-PCR was used to measure the levels of mRNAs of pro-apoptotic genes. The frequency of apoptosis in the tumours was assessed using immunohistochemistry for caspase-3.

Results

There was little change in the expression of genes involved in tumour growth and angiogenesis but a significant down-regulation of the expression of genes involved in apoptosis. This effect on apoptosis was confirmed by a general decrease in the expression of mRNA for selected pro-apoptotic genes. Epo-treated tumours had a significantly lower frequency of apoptosis as measured by immunohistochemistry for caspase 3.

Conclusions

Our results suggest that the increased tumour growth during erythropoietin treatment might be due to inhibition of apoptosis, an effect that becomes significant during tissue damage such as surgery.

This further suggests that the decreased survival during erythropoietin treatment might be due to inhibition of apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-648) contains supplementary material, which is available to authorized users.

Erythropoietin promotes breast tumorigenesis through tumor-initiating cell self-renewal

Erythropoietin (EPO) is a hormone that induces red blood cell production. In its recombinant form, EPO is the one of most prescribed drugs to treat anemia, including that arising in cancer patients. In randomized trials, EPO administration to cancer patients has been associated with decreased survival. Here, we investigated the impact of EPO modulation on tumorigenesis. Using genetically engineered mouse models of breast cancer, we found that EPO promoted tumorigenesis by activating JAK/STAT signaling in breast tumor-initiating cells (TICs) and promoted TIC self renewal. We determined that EPO was induced by hypoxia in breast cancer cell lines, but not in human mammary epithelial cells. Additionally, we demonstrated that high levels of endogenous EPO gene expression correlated with shortened relapse-free survival and that pharmacologic JAK2 inhibition was synergistic with chemotherapy for tumor growth inhibition in vivo. These data define an active role for endogenous EPO in breast cancer progression and breast TIC self-renewal and reveal a potential application of EPO pathway inhibition in breast cancer therapy.

Autocrine/paracrine erythropoietin regulates migration and invasion potential and the stemness of human breast cancer cells

Recent studies suggest that erythropoietin (EPO) has pleiotropic effects in several cell types in addition to hematopoietic cells; however, the role of EPO-mediated cell signaling in nonhematopoietic cells, including in cancer cells, remains controversial. Here, we report our findings of autocrine/paracrine production of EPO by breast cancer cells and its functional significance. We detected a significant level of autocrine/paracrine EPO in the conditioned medium from the culture of SKBR3 breast cancer cells, particularly when the cells were cultured in hypoxia. Through knockdown of EPO and EPO receptor expression and experimental elevation of EPO receptor expression in SKBR3 breast cancer cells, we demonstrated novel roles of autocrine/paracrine EPO-mediated cell signaling in regulating migration and invasion potential and stemness-like properties of breast cancer cells.

Epo receptors are not detectable in primary human tumor tissue samples

Erythropoietin (Epo) is a cytokine that binds and activates an Epo receptor (EpoR) expressed on the surface of erythroid progenitor cells to promote erythropoiesis. While early studies suggested EpoR transcripts were expressed exclusively in the erythroid compartment, low-level EpoR transcripts were detected in nonhematopoietic tissues and tumor cell lines using sensitive RT-PCR methods. However due to the widespread use of nonspecific anti-EpoR antibodies there are conflicting data on EpoR protein expression. In tumor cell lines and normal human tissues examined with a specific and sensitive monoclonal antibody to human EpoR (A82), little/no EpoR protein was detected and it was not functional. In contrast, EpoR protein was reportedly detectable in a breast tumor cell line (MCF-7) and breast cancer tissues with an anti-EpoR polyclonal antibody (M-20), and functional responses to rHuEpo were reported with MCF-7 cells. In another study, a functional response was reported with the lung tumor cell line (NCI-H838) at physiological levels of rHuEpo. However, the specificity of M-20 is in question and the absence of appropriate negative controls raise questions about possible false-positive effects. Here we show that with A82, no EpoR protein was detectable in normal human and matching cancer tissues from breast, lung, colon, ovary and skin with little/no EpoR in MCF-7 and most other breast and lung tumor cell lines. We show further that M-20 provides false positive staining with tissues and it binds to a non-EpoR protein that migrates at the same size as EpoR with MCF-7 lysates. EpoR protein was detectable with NCI-H838 cells, but no rHuEpo-induced phosphorylation of AKT, STAT3, pS6RP or STAT5 was observed suggesting the EpoR was not functional. Taken together these results raise questions about the hypothesis that most tumors express high levels of functional EpoR protein.

Treating patients with schizophrenia deficit with erythropoietin?

This systematic review summarizes and critically appraises the literature on the effect of erythropoietin (EPO) in schizophrenia patients and the pathophysiological mechanisms that may explain the potential of its use in this disease. EPO is mainly known for its regulatory activity in the synthesis of erythrocytes and is frequently used in treatment of chronic anemia. This cytokine, however, has many other properties, some of which may improve the symptoms of psychiatric illness. The review follows the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement guidelines. Three databases (Medline, Web of Science, and Cochrane) were searched combining the search terms 'erythropoietin AND (psychotic disorders OR schizophrenia)'. Seventy-eight studies were included in qualitative synthesis, a meta-analytic approach being prohibited. The findings suggest that several EPO cerebral potential properties may be relevant for schizophrenia treatment, such as neurotransmission regulation, neuroprotection, modulation of inflammation, effects on blood-brain barrier permeability, effects on oxidative stress and neurogenesis. Several potentially detrimental side-effects of EPO therapy, such as increased risk of thrombosis, cancer, increased metabolic rate and mean arterial blood pressure leading to cerebral ischemia could severely limit or halt the use of EPO. Overall, because the available data are inconclusive, further efforts in this field are warranted.

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.

Prognostic significance of erythropoietin in pancreatic adenocarcinoma

BACKGROUND

Erythropoietin (Epo) administration has been reported to have tumor-promoting effects in anemic cancer patients. We investigated the prognostic impact of endogenous Epo in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODOLOGY

The clinico-pathological relevance of hemoglobin (Hb, n = 150), serum Epo (sEpo, n = 87) and tissue expression of Epo/Epo receptor (EpoR, n = 104) was analyzed in patients with PDAC. Epo/EpoR expression, signaling, growth, invasion and chemoresistance were studied in Epo-exposed PDAC cell lines.

RESULTS

Compared to donors, median preoperative Hb levels were reduced by 15% in both chronic pancreatitis (CP, p<0.05) and PDAC (p<0.001), reaching anemic grade in one third of patients. While inversely correlating to Hb (r = -0.46), 95% of sEPO values lay within the normal range. The individual levels of compensation were adequate in CP (observed to predicted ratio, O/P = 0.99) but not in PDAC (O/P = 0.85). Strikingly, lower sEPO values yielding inadequate Epo responses were prominent in non-metastatic M0-patients, whereas these parameters were restored in metastatic M1-group (8 vs. 13 mU/mL; O/P = 0.82 vs. 0.96; p<0.01)--although Hb levels and the prevalence of anemia were comparable. Higher sEpo values (upper quartile ≥ 16 mU/ml) were not significantly different in M0 (20%) and M1 (30%) groups, but were an independent prognostic factor for shorter survival (HR 2.20, 10 vs. 17 months, p<0.05). The pattern of Epo expression in pancreas and liver suggested ectopic release of Epo by capillaries/vasa vasorum and hepatocytes, regulated by but not emanating from tumor cells. Epo could initiate PI3K/Akt signaling via EpoR in PDAC cells but failed to alter their functions, probably due to co-expression of the soluble EpoR isoform, known to antagonize Epo.

CONCLUSION/SIGNIFICANCE

Higher sEPO levels counteract anemia but worsen outcome in PDAC patients. Further trials are required to clarify how overcoming a sEPO threshold ≥16 mU/ml by endogenous or exogenous means may predispose to or promote metastatic progression.

Recombinant human erythropoietin suppresses endothelial cell apoptosis and reduces the ratio of Bax to Bcl-2 proteins in the aortas of apolipoprotein E-deficient mice

Recent clinical trials have raised concern that therapy with recombinant human erythropoietin (EPO) may increase cardiovascular disease risk, event rate, and mortality. Endothelial cell apoptosis has been implicated in both atherogenesis and in the destabilization and rupture of atheromatous plaques. In the current study, we observed that EPO and the EPO-mimetic peptide EMP-1 markedly suppressed lipopolysaccharide-induced apoptosis in endothelial cell monolayers. Therapeutic concentrations of EPO upregulated Bcl-2 expression and concurrently diminished expression of Bax, resulting in a net decrease in the ratio of Bax to Bcl-2 protein concentrations. In vivo studies demonstrated that EPO receptor is abundantly expressed in murine aorta and that EPO treatment for 10 weeks markedly decreased the ratio of Bax to Bcl-2 protein in the aortas of apolipoprotein E-deficient mice fed a high-fat diet. To our knowledge, these data are the first to reveal a modulation of regulators of the apoptotic pathway in murine aorta by chronic EPO treatment. These observations imply that long-term administration of EPO may have the potential to affect plaque stability.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

Long-term prognostic impact of the use of erythropoietic-stimulating agents in patients with chronic myeloid leukemia in chronic phase treated with imatinib

BACKGROUND

Anemia is a frequent side effect of imatinib in patients with chronic myeloid leukemia (CML). Erythropoietic-stimulating agents have been used for treatment of imatinib-induced anemia. There are no data on long-term safety of erythropoietic-stimulating agents in CML patients.

METHODS

The records of chronic phase CML patients who received treatment with imatinib were reviewed for use of erythropoietic-stimulating agents and occurrence of thrombotic events. Data on cytogenetic response and survival were analyzed by use of erythropoietic-stimulating agent.

RESULTS

A total of 608 patients were included, and 217 patients received erythropoietic-stimulating agents. There were 30 thrombotic episodes. Patients who received erythropoietic-stimulating agents had a higher rate of thrombosis (8.5% vs 2.6%, P = .0025). There was no difference in cytogenetic response rate and survival by use of erythropoietic-stimulating agent. Development of grade 3-4 anemia occurred in 62 (10%) patients and was associated with significantly worse response and survival in patients in late chronic phase. By multivariate analysis, use of erythropoietic-stimulating agents was not a risk factor for event-free survival.

CONCLUSIONS

In our cohort of chronic phase CML patients, use of erythropoietic-stimulating agents did not impact survival or cytogenetic response rate, but was associated with a higher thrombosis rate. Severe anemia is associated with worse survival and response.

Association between pharmaceutical support and basic science research on erythropoiesis-stimulating agents

BACKGROUND

To our knowledge, no prior research has evaluated the association between pharmaceutical industry funding and basic science research results. When erythropoiesis-stimulating agents (ESAs) were licensed to treat chemotherapy-associated anemia, basic science concerns related to potential cancer stimulation were raised. We evaluated associations between pharmaceutical industry support and reported findings evaluating ESA effects on cancer cells.

METHODS

Articles identified in MEDLINE and EMBASE databases (1988-2008) investigating basic science findings related to ESA administration in the solid tumor setting were reviewed. Outcomes included information on erythropoietin receptors (EpoRs), Epo-induced signaling events, cellular function, and qualitative conclusions. Information on study funding (academic investigators with no reported funding from ESA manufacturers [64 studies], academic investigators with grant funding from ESA manufacturers [7 studies], and investigators employed by the ESA manufacturers [3 studies]) was evaluated. Some studies did not include information on each outcome.

RESULTS

Investigators without funding from ESA manufacturers were more likely than academic investigators with such funding or investigators employed by ESA manufacturers to identify EpoRs on solid tumor cells (100%, 60%, and 67%, respectively; P = .009), Epo-induced signaling events (94%, 0%, and 0%, respectively; P = .001), or changes in cellular function (57%, 0%, and 0%, respectively; P = .007) and to conclude that ESAs had potentially harmful effects on cancer cells (57%, 0%, and 0%, respectively; P = .008).

CONCLUSIONS

Researchers who do not have pharmaceutical industry support are more likely than those with pharmaceutical support to identify detrimental in vitro effects of ESAs. The potential for conflicts of interest to affect basic science research should be considered.

Oxidative stress: Biomarkers and novel therapeutic pathways

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO) and members of the mammalian forkhead transcription factors of the O class (FoxOs) may offer the greatest promise for new treatment regimens since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. However, biological outcome with EPO and FoxOs may sometimes be both unexpected and undesirable that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as complicated role EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

Erythropoietin, forkhead proteins, and oxidative injury: biomarkers and biology

Oxidative stress significantly impacts multiple cellular pathways that can lead to the initiation and progression of varied disorders throughout the body. It therefore becomes imperative to elucidate the components and function of novel therapeutic strategies against oxidative stress to further clinical diagnosis and care. In particular, both the growth factor and cytokine erythropoietin (EPO), and members of the mammalian forkhead transcription factors of the O class (FoxOs), may offer the greatest promise for new treatment regimens, since these agents and the cellular pathways they oversee cover a range of critical functions that directly influence progenitor cell development, cell survival and degeneration, metabolism, immune function, and cancer cell invasion. Furthermore, both EPO and FoxOs function not only as therapeutic targets, but also as biomarkers of disease onset and progression, since their cellular pathways are closely linked and overlap with several unique signal transduction pathways. Yet, EPO and FoxOs may sometimes have unexpected and undesirable effects that can raise caution for these agents and warrant further investigations. Here we present the exciting as well as the complex role that EPO and FoxOs possess to uncover the benefits as well as the risks of these agents for cell biology and clinical care in processes that range from stem cell development to uncontrolled cellular proliferation.

Erythroid-Stimulating Agents in Cancer Therapy: Potential Dangers and Biologic Mechanisms

Erythropoietin-stimulating agents (ESAs) were originally designed to replace endogenous erythropoietin in patients with anemia secondary to renal failure. Their use has subsequently been expanded to include patients with anemia of other causes, including cancer patients, in whom deficiency of erythropoietin, per se, is not the primary cause of anemia. Although early studies showed promise of ESA administration in reducing the need for transfusions and improving the quality of life in cancer patients, several large randomized clinical trials have recently shown a potential detrimental effect of ESA administration on tumor progression and survival in these patients. These studies have called into question the safety of ESAs as supportive therapy in patients being treated for oncologic conditions. However, numerous questions remain to be addressed regarding the design of these studies, the effect of various targeted hemoglobin levels, and the potential biologic mechanisms proposed to explain promotion of tumor progression and reduced survival.

An erythropoietin autocrine/paracrine axis modulates the growth and survival of human prostate cancer cells

Erythropoietin receptors have been identified on a variety of cancer-derived cell lines and primary cancer cells, including those of prostate cancer. The functional status of these extrahematopoietic erythropoietin receptors remains a matter of some dispute. The publication of several important clinical trials suggesting a direct effect of erythropoietin on the growth and survival of primary tumors adds further importance to the question of whether erythropoietin receptors on cancer cells are functional. We have reported previously that human prostate cancer cell lines and primary prostate cancer cells express functional erythropoietin receptors that respond to exogenous erythropoietin by increased cell proliferation and STAT5 phosphorylation. We now show that prostate cancer cell lines express both the EPO gene and the biologically active erythropoietin. The coexpression of functional receptor and biologically active ligand in the cells has led us to hypothesize an autocrine/paracrine mechanism, driven by endogenous erythropoietin, which may modulate the growth and progression of prostate cancer. To test our hypothesis, we have knocked down, independently, erythropoietin receptor and erythropoietin on prostate cancer cells by transfection with short hairpin RNAs. Erythropoietin receptor knockdown cells grow significantly more slowly than their erythropoietin receptor-bearing counterparts in monolayer culture, produce fewer, smaller colonies in soft agar, and do not exhibit erythropoietin-induced signaling. Erythropoietin knockdown cells exhibit dramatically slower rates of growth, which could be restored by transfecting the cells with a murine erythropoietin gene. Taken together, our data suggest that the coordinated regulation of a functional erythropoietin/erythropoietin receptor axis in prostate cancer cells may be integral to the growth and progression of prostate cancer.

Constitutively active erythropoietin receptor expression in breast cancer cells promotes cellular proliferation and migration through a MAP-kinase dependent pathway

The role of erythropoietin receptor (EpoR) expression in tumor cells and the potential of EpoR-mediated signaling to contribute to cellular proliferation and invasiveness require further characterization. To determine whether EpoR expression and activation in tumor cells modulates intracellular signal transduction to promote cellular proliferation and migration, we employed a novel experimental model using human breast cancer cells engineered to stably express a constitutively active EpoR-R129C variant. EpoR-R129C expression resulted in increased cellular proliferation and migration of breast cancer cells and these effects were associated with significantly increased Epo-induced phosphorylation of ERK1/2, AKT and c-Jun-NH2-kinase (SAPK/JNK) proteins. Expression of the constitutively active EpoR-R129C receptor promoted the proliferation and migration of breast cancer cells via activation of ERK- and SAPK/JNK-dependent signaling pathways, respectively. These findings suggest that EpoR over-expression and activation in breast cancer cells has the potential to contribute to tumor progression by promoting the proliferation and invasiveness of the neoplastic cells.

Predictors of response to erythropoiesis-stimulating agents (ESA) in cancer patients: the role of baseline serum epoetin level

Anemia is the most frequent hematologic abnormality among cancer patients. Its pathophysiology comprises reduction in erythrocyte half-life, poor iron reutilization by the bone marrow, and inadequate response to erythropoietin (EPO), with reduced endogenous EPO (eEPO) levels. Current treatment implies the use of erythropoiesis- stimulating agents (ESA), to which 35-48% of patients show primary resistance. The search for predictors of response to ESA treatment has been inconclusive. Iron or vitamin deficiency, the recent need for transfusion, or a lack of hemoglobin increase within the first 2-4 weeks usually predict resistance to ESA. High serum eEPO levels at treatment initiation (>100-150 mU/ml) may also predict resistance, especially in hematologic malignancies, but the results in solid tumors are not consistent. Although patients with cancer-related anemia show higher eEPO levels than patients without anemia, there is extreme variability among individuals. Future studies are needed to clarify eEPO usefulness in predicting response to ESA treatment.

Erythropoietin inhibits apoptosis induced by photodynamic therapy in ovarian cancer cells

Recombinant human erythropoietin is widely used to treat anemia associated with cancer and with the myelosuppressive effects of chemotherapy, particularly platinum-based regimens. Erythropoietin is the principal regulator of erythroid cell proliferation, differentiation, and apoptosis. Recently, the antiapoptotic and proliferative effects of erythropoietin on nonhematopoietic cells were also established. We now show the effect of erythropoietin treatment on the response of A2780 and SKOV3 ovarian carcinoma cell lines to photodynamic therapy (PDT) using hypericin. SKOV3 exhibited an increased resistance to hypericin when cells were treated with erythropoietin. This resistance was reversed by treatment of SKOV3 cells with the specific Janus kinase 2 kinase inhibitor AG490 or the tyrosine kinase inhibitor genistein. These results support a role for the specific erythropoietin-induced Janus kinase 2/STAT signal transduction pathway in PDT resistance. Evidence of erythropoietin signaling was obtained by the demonstration of Akt phosphorylation in both A2780 and SKOV3 cells. Erythropoietin-treated SKOV3 cells exhibited decreased apoptosis induced by hypericin, an effect that was blocked by the phosphoinositide 3-kinase/Akt inhibitor wortmannin. These results may have important implications for ovarian cancer patients undergoing PDT and receiving erythropoietin.

Erythropoietin enhancement of rat pancreatic tumor cell proliferation requires the activation of ERK and JNK signals

Erythropoietin (EPO) regulates the proliferation and differentiation of erythroid cells by binding to its specific transmembrane receptor EPOR. Recent studies, however, have shown that the EPOR is additionally present in various cancer cells and EPO induces the proliferation of these cells, suggesting a different function for EPO other than erythropoiesis. Therefore, the purpose of the present study was to examine EPOR expression and the role of EPO in the proliferation and signaling cascades involved in this process, using the rat pancreatic tumor cell line AR42J. Our results showed that AR42J cells expressed EPOR, and EPO significantly enhanced their proliferation. Cell cycle analysis of EPO-treated cells indicated an increased percentage of cells in the S phase, whereas cell numbers in G0/G1 phase were significantly reduced. Phosphorylation of extracellular regulatory kinase 1/2 (ERK1/2) and c-Jun NH2terminal kinase 1/2 (JNK1/2) was rapidly stimulated and sustained after EPO addition. Treatment of cells with mitogen-activated protein/ERK kinase (MEK) inhibitor PD98059 or JNK inhibitor SP600125 significantly inhibited EPO-enhanced proliferation and also increased the fraction of cells in G0/G1 phase. Furthermore, the inhibition of JNK using small interference RNA (siRNA) suppressed EPO-enhanced proliferation of AR42J cells. Taken together, our results indicate that AR42J cells express EPOR and that the activation of both ERK1/2 and JNK1/2 by EPO is essential in regulating proliferation and the cell cycle. Thus both appear to play a key role in EPO-enhanced proliferation and suggest that the presence of both is required for EPO-mediated proliferation of AR42J cells.

Erythropoietin: elucidating new cellular targets that broaden therapeutic strategies

Given that erythropoietin (EPO) is no longer believed to have exclusive biological activity in the hematopoietic system, EPO is now considered to have applicability in a variety of nervous system disorders that can overlap with vascular disease, metabolic impairments, and immune system function. As a result, EPO may offer efficacy for a broad number of disorders that involve Alzheimer's disease, cardiac insufficiency, stroke, trauma, and diabetic complications. During a number of clinical conditions, EPO is robust and can prevent metabolic compromise, neuronal and vascular degeneration, and inflammatory cell activation. Yet, use of EPO is not without its considerations especially in light of frequent concerns that may compromise clinical care. Recent work has elucidated a number of novel cellular pathways governed by EPO that can open new avenues to avert deleterious effects of this agent and offer previously unrecognized perspectives for therapeutic strategies. Obtaining greater insight into the role of EPO in the nervous system and elucidating its unique cellular pathways may provide greater cellular viability not only in the nervous system but also throughout the body.

Triple play: promoting neurovascular longevity with nicotinamide, WNT, and erythropoietin in diabetes mellitus

Oxidative stress is a principal pathway for the dysfunction and ultimate destruction of cells in the neuronal and vascular systems for several disease entities, not promoting the ravages of oxidative stress to any less of a degree than diabetes mellitus. Diabetes mellitus is increasing in incidence as a result of changes in human behavior that relate to diet and daily exercise and is predicted to affect almost 400 million individuals worldwide in another two decades. Furthermore, both type 1 and type 2 diabetes mellitus can lead to significant disability in the nervous and cardiovascular systems, such as cognitive loss and cardiac insufficiency. As a result, innovative strategies that directly target oxidative stress to preserve neuronal and vascular longevity could offer viable therapeutic options to diabetic patients in addition to more conventional treatments that are designed to control serum glucose levels. Here we discuss the novel application of nicotinamide, Wnt signaling, and erythropoietin that modulate cellular oxidative stress and offer significant promise for the prevention of diabetic complications in the nervous and vascular systems. Essential to this process is the precise focus upon diverse as well as common cellular pathways governed by nicotinamide, Wnt signaling, and erythropoietin to outline not only the potential benefits, but also the challenges and possible detriments of these therapies. In this way, new avenues of investigation can hopefully bypass toxic complications, or at the very least, avoid contraindications that may limit care and offer both safe and robust clinical treatment for patients.

Erythropoietin receptor transcription is neither elevated nor predictive of surface expression in human tumour cells

Erythropoietin receptor (EpoR) has been reported to be overexpressed in tumours and has raised safety concerns regarding the use of erythropoiesis-stimulating agents (ESAs) to treat anaemia in cancer patients. To investigate the potential for EpoR to be overexpressed in tumours, we have evaluated human tumours for amplification of the EPOR locus, levels of EPOR transcripts, and expression of surface EpoR protein. Gene amplification analysis of 1083 solid tumours found that amplification of the EPOR locus was rare with frequencies similar to other non-oncogenes. EPOR transcript levels in tumours and tumour cell lines were low in comparison with bone marrow and were equivalent to, or lower than, levels in normal tissues of tumour origin. Although EpoR mRNA was detected in some tumour lines, no EpoR could be detected on the cell surface using (125)I-Epo binding studies. This may be due to the lack of EpoR protein expression or lack of cell-surface-trafficking factors, such as Jak2. Taken together, we have found no evidence that EpoR is overexpressed in tumours or gets to the surface of tumour cells. This suggests that there is no selective advantage for tumours to overexpress EpoR and questions the functional relevance of EpoR gene transcription in tumours.

Erythropoietin stimulates cancer cell migration and activates RhoA protein through a mitogen-activated protein kinase/extracellular signal-regulated kinase-dependent mechanism

Erythropoietin (Epo) receptor (EpoR) is expressed in several cancer cell lines, and the functional consequence of this expression is under extensive study. In this study, we used a cervical cancer cell line in which EpoR was first found to be expressed and to correlate with the severity of the disease. We demonstrate that Epo is a chemoattractant for these cancer cells, enhancing their migration under serum-starved conditions. Using a Transwell migration system, we show that Epo enhances cancer cell migration in a dose- and time-dependent manner. The effect of Epo is dependent on the activity of two signaling pathways: the mitogen-activated protein kinase (MAPK) pathway and the RhoA GTPase pathway. We show that Epo activates both pathways in a Janus kinase-dependent manner and that this activation is required for Epo effects on cell migration. Furthermore, we use both pharmacological and genetic inhibitors to demonstrate that the activation of RhoA GTPase is dependent on the activity of the MAPK pathway, providing the first evidence for interaction between these two signaling cascades.

Erythropoietin and erythropoietin receptor coexpression is associated with poor survival in stage I non-small cell lung cancer

PURPOSE

This study was designed to evaluate the prognostic effect of erythropoietin (EPO) and EPO receptor (EPO-R) expression in stage I non-small cell lung cancer (NSCLC) patients.

EXPERIMENTAL DESIGN

EPO and EPO-R expression in 158 tumor samples from resected stage I NSCLC was evaluated using immunohistochemistry and tissue array technology.

RESULTS

EPO-R and EPO were highly expressed in 20.9% and 35.4% of tumors, respectively. High EPO-R expression compared with negative or low-level expression was associated with a poor 5-year disease-specific survival (60.6% versus 80.8%; P = 0.01, log-rank test). High EPO expression compared with negative and low-level expression was associated with a trend toward a poor 5-year disease-specific survival (69.6% versus 80.4%; P = 0.13, log-rank test). A high level of EPO-R and EPO coexpression was associated with a poor 5-year disease-specific survival compared with other groups of patients (50.0% versus 80.0% survival at the end of follow-up; P = 0.005, log-rank test). In multivariate analysis for disease-specific survival, high-level EPO-R and EPO coexpression was an independent prognostic factor for disease-specific survival (hazard ratio, 2.214; 95% confidence interval, 1.012-4.848; P = 0.046).

CONCLUSION

These results establish the pejorative prognostic value of EPO and EPO-R expression in early-stage resected NSCLC and suggest a potential paracrine and/or autocrine role of endogenous EPO in NSCLC aggressiveness.

The Src homology 2 domain tyrosine phosphatases SHP-1 and SHP-2: diversified control of cell growth, inflammation, and injury

Interest in the diverse biology of protein tyrosine phosphatases that are encoded by more than 100 genes in the human genome continues to grow at an accelerated pace. In particular, two cytoplasmic protein tyrosine phosphatases composed of two Src homology 2 (SH2) NH2-terminal domains and a C-terminal protein-tyrosine phosphatase domain referred to as SHP-1 and SHP-2 are known to govern a host of cellular functions. SHP-1 and SHP-2 modulate progenitor cell development, cellular growth, tissue inflammation, and cellular chemotaxis, but more recently the role of SHP-1 and SHP-2 to directly control cell survival involving oxidative stress pathways has come to light. SHP-1 and SHP-2 are fundamental for the function of several growth factor and metabolic pathways yielding far reaching implications for disease pathways and disorders such as diabetes, neurodegeneration, and cancer. Although SHP-1 and SHP-2 can employ similar or parallel cellular pathways, these proteins also clearly exert opposing effects upon downstream cellular cascades that affect early and late apoptotic programs. SHP-1 and SHP-2 modulate cellular signals that involve phosphatidylinositol 3-kinase, Akt, Janus kinase 2, signal transducer and activator of transcription proteins, mitogen-activating protein kinases, extracellular signal-related kinases, c-Jun-amino terminal kinases, and nuclear factor-kappaB. Our progressive understanding of the impact of SHP-1 and SHP-2 upon multiple cellular environments and organ systems should continue to facilitate the targeted development of treatments for a variety of disease entities.

Erythropoietin blockade inhibits the induction of tumor angiogenesis and progression

Background

The induction of tumor angiogenesis, a pathologic process critical for tumor progression, is mediated by multiple regulatory factors released by tumor and host cells. We investigated the role of the hematopoietic cytokine erythropoietin as an angiogenic factor that modulates tumor progression.

Methodology/Principal Findings

Fluorescently-labeled rodent mammary carcinoma cells were injected into dorsal skin-fold window chambers in mice, an angiogenesis model that allows direct, non-invasive, serial visualization and real-time assessment of tumor cells and neovascularization simultaneously using intravital microscopy and computerized image analysis during the initial stages of tumorigenesis. Erythropoietin or its antagonist proteins were co-injected with tumor cells into window chambers. In vivo growth of cells engineered to stably express a constitutively active erythropoietin receptor EPOR-R129C or the erythropoietin antagonist R103A-EPO were analyzed in window chambers and in the mammary fat pads of athymic nude mice. Co-injection of erythropoietin with tumor cells or expression of EPOR-R129C in tumor cells significantly stimulated tumor neovascularization and growth in window chambers. Co-injection of erythropoietin antagonist proteins (soluble EPOR or anti-EPO antibody) with tumor cells or stable expression of antagonist R103A-EPO protein secreted from tumor cells inhibited angiogenesis and impaired tumor growth. In orthotopic tumor xenograft studies, EPOR-R129C expression significantly promoted tumor growth associated with increased expression of Ki67 proliferation antigen, enhanced microvessel density, decreased tumor hypoxia, and increased phosphorylation of extracellular-regulated kinases ERK1/2. R103A-EPO antagonist expression in mammary carcinoma cells was associated with near-complete disruption of primary tumor formation in the mammary fat pad.

Conclusions/Significance

These data indicate that erythropoietin is an important angiogenic factor that regulates the induction of tumor cell-induced neovascularization and growth during the initial stages of tumorigenesis. The suppression of tumor angiogenesis and progression by erythropoietin blockade suggests that erythropoietin may constitute a potential target for the therapeutic modulation of angiogenesis in cancer.

Erythropoietin in cancer: presumption of innocence?

Erythropoietin emerged as the biggest drug in oncology despite never having demonstrated a survival benefit in patients with cancer. Two phase III clinical trials reported more than 3 years ago that erythropoietin adversely affected cancer survival rates, due mainly to tumor progression. Despite changes to the product label for erythropoietins in 2004, clinical practice remained unchanged until recent weeks when, following reports of three new phase III studies and a phase II trial, a "black box warning" for erythropoietin products was issued by the Food and Drug Administration (FDA). Whether erythropoietin products can be considered safe when used for FDA-approved indications is currently at issue; however, addressing this question will be difficult until the mechanisms of erythropoietin-stimulated tumor progression are understood. A thorough evaluation of materials from clinical trials already completed may shed new light on how erythropoietin promotes cancer progression. Until these issues are resolved, oncologists should inform their patients of erythropoietin's potential adverse impact on cancer progression and survival. Disclosure of potential conflicts of interest is found at the end of this article.

Cellular demise and inflammatory microglial activation during beta-amyloid toxicity are governed by Wnt1 and canonical signaling pathways

Initially described as a modulator of embryogenesis for a number of organ systems, Wnt1 has recently been linked to the development of several neurodegenerative disorders, none being of greater significance than Alzheimer's disease. We therefore examined the ability of Wnt1 to oversee vital pathways responsible for cell survival during beta-amyloid (Abeta1-42) exposure. Here we show that Wnt1 is critical for protection in the SH-SY5Y neuronal cell line against genomic DNA degradation, membrane phosphatidylserine (PS) exposure, and microglial activation, since these neuroprotective attributes of Wnt1 are lost during gene silencing of Wnt1 protein expression. Intimately tied to Wnt1 protection is the presence and activation of Akt1. Pharmacological inhibition of the PI 3-K pathway or gene silencing of Akt1 expression can abrogate the protective capacity of Wnt1. Closely aligned with Wnt1 and Akt1 are the integrated canonical pathways of synthase kinase-3beta (GSK-3beta) and beta-catenin. Through Akt1 dependent pathways, Wnt1 phosphorylates GSK-3beta and maintains beta-catenin integrity to insure its translocation from the cytoplasm to the nucleus to block apoptosis. Our work outlines a highly novel role for Wnt1 and its integration with Akt1, GSK-3beta, and beta-catenin to foster neuronal cell survival and repress inflammatory microglial activation that can identify new avenues of therapy against neurodegenerative disorders.

Expression and function of erythropoietin receptors in tumors

Safety concerns surrounding the use of recombinant human erythropoietin (Epo) to treat anemia in cancer patients were raised after 2 recent clinical studies reported a worse survival outcome in patients who received epoetin alpha or epoetin beta compared with patients who received placebo. Although those findings contrasted with previous clinical studies, which demonstrated no difference in survival for cancer patients who received erythropoiesis-stimulating agents (ESAs), some investigators have suggested a potential role for ESAs in promoting tumor growth through 1) stimulation of Epo receptors (EpoR) expressed in tumors, 2) stimulation and formation of tumor vessels, and/or 3) enhanced tumor oxygenation. The first and second hypotheses appeared to be supported by some EpoR expression and ESA in vitro studies. However, these conclusions have been challenged because of poor specificity of EpoR-detection methodologies, conflicting data from different groups, and the lack of correlation between in vitro data and in vivo findings in animal tumor models. For this report, the authors reviewed the biology of EpoR in erythropoiesis and compared and contrasted the reported findings on the role of ESAs and EpoR in tumors.

Microglial integrity is maintained by erythropoietin through integration of Akt and its substrates of glycogen synthase kinase-3beta, beta-catenin, and nuclear factor-kappaB

Recognized as a robust cytoprotectant for multiple tissues of the hematopoietic, vascular, cardiac, and nervous systems, erythropoietin (EPO) also is considered to be an attractive therapeutic candidate to modulate inflammatory cell function and survival during neurodegenerative disorders. To this end, microglia of the central nervous system serve a complex function not only to dispense of foreign organisms and injured cells of the brain, but also to foster tissue repair and reorganization during neuronal and vascular cell insults. We therefore examined the ability of EPO to modulate microglial cell survival and the underlying signal transduction pathways that govern microglial integrity during oxygen-glucose deprivation (OGD)--induced oxidative stress. We demonstrate in the microglial cell line EOC 2 that EPO provides direct microglial protection against early and late apoptotic programs of membrane phosphatidylserine exposure and genomic DNA degradation. Furthermore, expression and activation of Akt1 is vital to the cytoprotective capacity of EPO, since pharmacological inhibition of the PI 3-K pathway or gene silencing of Akt1 expression eliminates the ability of EPO to protect microglial cells. Through Akt1 dependent mechanisms that can be abrogated through the gene silencing of Akt1, maintenance of microglial cell integrity during OGD by EPO is closely integrated with the phosphorylation and inhibition of glycogen synthase kinase-3beta activity as well as the intracellular trafficking of beta-catenin and nuclear factor-kappaB. Further work that continues to elucidate the ability of EPO to target the intricate pathways that determine inflammatory cell function and integrity may lay the ground work for new therapeutic avenues for neurodegenerative disease.