Erythropoietin as an angiogenic factor in gastric carcinoma

Anemia management in cancer patients with chronic kidney disease

Cancer and kidney disease are linked by causality and comorbidities. Observational data show an increased risk of malignancy as renal function declines. Erythropoietin stimulating agents (ESAs), which are the cornerstone therapy for anemia patients with chronic kidney disease and cancer, are associated with increased risks for cancer, cancer-related mortality, progression of disease, and thromboembolic events. This article examines the recently published guidelines for ESA use in cancer patients from the American Society of Clinical Oncology and American Society of Hematology and attempts to contextualize them to the care of patients with coexistent CKD, cancer, and anemia.

Hematopoietic growth factors and tumor angiogenesis

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

Erythropoietin and Its Angiogenic Activity

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

Correlation of adrenomedullin with the erythropoietin receptor and microvessel density in hepatocellular carcinoma

INTRODUCTION

Uncontrolled angiogenesis plays an essential role in the occurrence, metastasis and malignant progression of hepatocellular carcinoma (HCC). This study aimed to investigate the expression of adrenomedullin (ADM) in human HCC and its correlation with the expression of erythropoietin receptor (EPOR), microvessel density (MVD) and the tumor pathological characteristics.

MATERIAL AND METHODS

Fresh tumor tissues were obtained from 30 HCC patients after hepatectomy. Ten cirrhotic and 10 normal liver tissues were included as controls. Expression of ADM and EPOR was determined by real-time PCR. The MVD was determined by counting the number of microvessels.

RESULTS

The MVD and the mRNA levels of ADM and EPOR in cancer tissues were significantly higher than those in the non-cancer tissues (p < 0.05). Expression of ADM was significantly correlated with the MVD and EPOR (r = 0.68 and 0.74, p < 0.01). Adrenomedullin and EPOR mRNA levels in HCC tissues were correlated with capsule invasion, pathological differentiation and tumor metastasis (p < 0.05).

CONCLUSIONS

Our findings suggest that ADM and EPOR may serve as new regulatory factors involved in angiogenesis of HCC and represent novel targets for the treatment of HCC.

Expression and functional significance of the erythropoietin receptor in hepatocellular carcinoma

BACKGROUND

Erythropoietin, through its specific receptor (EpoR), may induce responses in a variety of non-haematopoietic tissues including malignant cells. The purpose of this study was to examine the expression of EpoR in hepatocellular carcinoma (HCC) and to correlate the levels of EpoR expression with the clinicopathological properties of HCC and tumour recurrence.

METHODS

The study included 134 patients who underwent curative hepatectomy for hepatitis B virus (HBV)-related primary HCC. The clinical, laboratory and pathological data from these patients were retrospectively collected. The expression of EpoR mRNA and protein were evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively.

RESULTS

Expression of EpoR mRNA in the cirrhotic liver was positively correlated with tumour cell differentiation and 1-year disease-free survival (74.8% in the high expression group versus 46.9% in the low expression group; P = 0.001), as it was for EpoR mRNA expression in HCC (64.4% in the high expression group versus 52.7% in the low expression group; P = 0.044). Tumour recurrence showed stronger dependence on the expression of EpoR protein in non-malignant cirrhotic livers than in HCC.

CONCLUSION

In HBV-related HCC, the levels of EpoR mRNA and protein in non-tumour cirrhotic livers were positively correlated with tumour cell differentiation, which is a favourable predictor of disease-specific survival.

Transcriptome sequencing reveals differences between primary and secondary hair follicle-derived dermal papilla cells of the Cashmere goat (Capra hircus)

The dermal papilla is thought to establish the character and control the size of hair follicles. Inner Mongolia Cashmere goats (Capra hircus) have a double coat comprising the primary and secondary hair follicles, which have dramatically different sizes and textures. The Cashmere goat is rapidly becoming a potent model for hair follicle morphogenesis research. In this study, we established two dermal papilla cell lines during the anagen phase of the hair growth cycle from the primary and secondary hair follicles and clarified the similarities and differences in their morphology and growth characteristics. High-throughput transcriptome sequencing was used to identify gene expression differences between the two dermal papilla cell lines. Many of the differentially expressed genes are involved in vascularization, ECM-receptor interaction and Wnt/β-catenin/Lef1 signaling pathways, which intimately associated with hair follicle morphogenesis. These findings provide valuable information for research on postnatal morphogenesis of hair follicles.

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

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

In vivo angiogenic activity of erythropoietin

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

Long-term and stable correction of uremic anemia by intramuscular injection of plasmids containing hypoxia-regulated system of erythropoietin expression

Relative deficiency in production of glycoprotein hormone erythropoietin (Epo) is a major cause of renal anemia. This study planned to investigate whether the hypoxia-regulated system of Epo expression, constructed by fusing Epo gene to the chimeric phosphoglycerate kinase (PGK) hypoxia response elements (HRE) in combination with cytomegalovirus immediate-early (CMV IE) basal gene promoter and delivered by plasmid intramuscular injection, might provide a long-term physiologically regulated Epo secretion expression to correct the anemia in adenine-induced uremic rats. Plasmid vectors (pHRE-Epo) were synthesized by fusing human Epo cDNA to the HRE/CMV promoter. Hypoxia-inducible activity of this promoter was evaluated first in vitro and then in vivo in healthy and uremic rats (n = 30 per group). The vectors (pCMV-Epo) in which Epo expression was directed by a constitutive CMV gene promoter served as control. ANOVA and Student's t-test were used to analyze between-group differences. A high-level expression of Epo was induced by hypoxia in vitro and in vivo. Though both pHRE-Epo and pCMV-Epo corrected anemia, the hematocrit of the pCMV-Epo-treated rats exceeded the normal (P < 0.05), but that of the pHRE-Epo-treated rats didn't. Hypoxia-regulated system of Epo gene expression constructed by fusing Epo to the HRE/CMV promoter and delivered by plasmid intramuscular injection may provide a long-term and stable Epo expression and secretion in vivo to correct the anemia in adenine-induced uremic rats.

Expression profile as predictor of relapse after adjuvant treatment in gastric cancer

INTRODUCTION

TNM and histological subtype are the most important prognostic criteria in gastric cancer. In this study, we have tried to identify an immunohistochemical protein profile involved in gastric recurrence after a radical surgery.

MATERIALS AND METHODS

In this paper, protein panels involved in gastric carcinogenesis and progression was analyzed by immunohistochemistry expression: p53, Ki-67, Bcl-2, COX-2, c-erb-B2, EPO-R, E-cadherin, and β-catenin in 44 gastrectomy samples coming from gastrectomy pieces of patients diagnosed and operated on adenocarcinoma of the stomach followed by adjuvant treatment based on MacDonald chemoradiation regimen. An immunostaining profile that could predict the relapse after the end of adjuvant treatment was tried to find. These results have shown that the expression of the adverse prognostic protein profile based on positive p53 immunohistochemical expression and non-conserved E-cadherin/B-catenin staining is associated with tumor recurrence and a poor disease-free survival in operated gastric cancer patients with curative intent followed by adjuvant chemoradiation according to MacDonald's regimen. A protein profile based on immunohistochemical expression of p53 and E-cadherin-B-catenin that has a significant correlation to disease-free survival was identified in gastric cancer samples.

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.

Clinical significance of erythropoietin receptor expression in oral squamous cell carcinoma

BACKGROUND

Hypoxic tumors are refractory to radiation and chemotherapy. High expression of biomarkers related to hypoxia in head and neck cancer is associated with a poorer prognosis. The present study aimed to evaluate the clinicopathological significance of erythropoietin receptor (EPOR) expression in oral squamous cell carcinoma (OSCC).

METHODS

The study included 256 patients who underwent primary surgical resection between October 1996 and August 2005 for treatment of OSCC without previous radiotherapy and/or chemotherapy. Clinicopathological information including gender, age, T classification, N classification, and TNM stage was obtained from clinical records and pathology reports. The mRNA and protein expression levels of EPOR in OSCC specimens were evaluated by Q-RT-PCR, Western blotting and immunohistochemistry assays.

RESULTS

We found that EPOR were overexpressed in OSCC tissues. The study included 17 women and 239 men with an average age of 50.9 years (range, 26-87 years). The mean follow-up period was 67 months (range, 2-171 months). High EPOR expression was significantly correlated with advanced T classification (p < 0.001), advanced TNM stage (p < 0.001), and positive N classification (p = 0.001). Furthermore, the univariate analysis revealed that patients with high tumor EPOR expression had a lower 5-year overall survival rate (p = 0.0011) and 5-year disease-specific survival rate (p = 0.0017) than patients who had low tumor levels of EPOR. However, the multivariate analysis using Cox's regression model revealed that only the T and N classifications were independent prognostic factors for the 5-year overall survival and 5-year disease-specific survival rates.

CONCLUSIONS

High EPOR expression in OSCC is associated with an aggressive tumor behavior and poorer prognosis in the univariate analysis among patients with OSCC. Thus, EPOR expression may serve as a treatment target for OSCC in the future.

Can local Erythropoietin administration enhance bone regeneration in osteonecrosis of femoral head?

Osteonecrosis of femoral head (ONFH) is a challenging disease. Regardless of underlying causes, the ultimate result in all cases is disruption of femoral head blood supply. Once the disease starts, it is progressive in 80% of cases. Since the majority of the affected individuals are young, every effort should be focused on preserving the patients own femoral head. These years, the role of angiogenic growth factors has been investigated with promising results in animal models of ONFH. Erythropoietin (EPO) is a well known hormone that has been used in treatment of chronic anemia for many years with few side effects. Considering the angiogenic properties of EPO, we hypothesize that local delivery of recombinant human EPO during core decompression will enhance bone regeneration in ONFH. In this way we also can avoid systemic side effects of EPO.

Impact of increased erythropoietin receptor expression and elevated serum erythropoietin levels on clinicopathological features and prognosis in renal cell carcinoma

Erythropoietin (EPO) expression and EPO receptor (EpoR) expression have been demonstrated in various malignant tumors. EPO-EpoR signaling can activate several downstream signal transduction pathways that enhance tumor aggressiveness. The present study was undertaken to evaluate the impact of overexpression of EpoR and elevated serum EPO (sEPO) levels on the clinicopathological features and prognosis of patients with renal cell carcinoma (RCC). EpoR expression was evaluated immunohistochemically in 56 patients. Tumors with a staining intensity greater than that of surrounding proximal tubules were defined as tumors with high EpoR expression. The association between EpoR expression levels and various clinicopathological factors was analyzed. sEPO levels were determined in 138 patients and its correlation to clinicopathological factors was also analyzed, and EpoR expression was determined in surgical specimens removed from 47 of those 138 patients. Patients with high EpoR expression and patients with sEPO elevation had clinicopathological features less favorable than those of other patients. Tumors demonstrating high EpoR expression had a significantly higher number of Ki-67-positive cells compared to those with low EpoR expression. Tumor assemblies in microvessels demonstrated high EpoR expression. Patients whose tumors demonstrated high EpoR expression and those with sEPO elevation had a significantly lower survival rate compared to other patients, and patients with both high EpoR expression and sEPO elevation had an extremely poor prognosis. Microvascular invasion was an independent factor associated with sEPO elevation, suggesting that EPO-EpoR signaling might be important in RCC metastasis. EPO-EpoR signaling may be involved in tumor growth and progression in RCC and the combination of EpoR expression and sEPO levels may effectively predict clinical outcome.

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

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

Prognostic significance of erythropoietin and erythropoietin receptor in gastric adenocarcinoma

AIM: To investigate the expression of Erythropoietin (Epo) and its receptor (EpoR) in gastric adenocarcinoma (GAC) and the correlation with angiogenesis and clinicopathological features.

METHODS: The expressions of Epo, EpoR and vascular endothelial growth factor (VEGF), as well as microvessel density were evaluated in 172 GAC biopsies by immunohistochemical staining. The correlations between these parameters and patient’s clinicopathological features were analyzed statistically.

RESULTS: The proportion of Epo and EpoR alterations in GAC was higher than that in adjacent normal mucosa (P = 0.035 and 0.030). Epo high-expression was associated with EpoR high-expression, Lauren type, extensive lymph node metastasis and advanced stage of GAC (P = 0.018, 0.018, 0.004 and 0), while EpoR expression was linked with older age, World Health Organization type, extensive lymph node metastasis and advanced stage (P = 0.001, 0.013, 0.008 and 0.001). VEGF high expression was significantly correlated with EpoR low-expression, Lauren type, extensive lymph node metastasis and advanced stage (P = 0.001, 0.001, 0.001 and 0.007). The expression of Epo or EpoR was associated with microvessel density (P = 0.004 and 0.046). On multivariate analysis, only lymph node metastasis, abnormal Epo expression and tumor nodes metastases stage were independently associated with survival. In addition, a strong association with the immunohistochemical expression of EpoR and the angiogenic protein, VEGF, was noted.

CONCLUSION: Increased expression of Epo and EpoR may play a significant role in the carcinogenesis, angiogenesis and progression of GAC. Epo may be an independent prognostic factor.

Erythropoietin is involved in angiogenesis in human primary melanoma

In this study, the extent of angiogenesis, evaluated as microvascular volume density, immunoreactivity of tumour cells to erythropoietin (Epo) and of endothelial cells to Epo receptor (EpoR) have been correlated in human primary melanoma specimens. Results showed that Epo/EpoR expression correlate with angiogenesis and tumour thickness. These findings suggest that Epo is secreted by tumour cells and it affects vascular endothelial cells via its receptor and promotes angiogenesis in a paracrine manner, playing an important role in melanoma angiogenesis.

Mast cells and angiogenesis in gastric carcinoma

Previous studies have shown that increased vascularity is associated with haematogenous metastasis and poor prognosis in gastric cancer. The role of mast cells in gastric cancer angiogenesis has not been clarified completely. In this study, we correlated microvascular density and tryptase- and chymase-positive mast cells with histopathological type in gastric cancer. Specimens of primary gastric adenocarcinomas obtained from 30 patients who had undergone curative gastrectomy were investigated immunohistochemically by using anti-CD31 antibody to stain endothelial cells and anti-tryptase and anti-chymase antibodies to stain mast cells. The results showed that stage IV gastric carcinoma has a higher degree of vascularization than other stages and that both tryptase- and chymase-positive mast cells increase in parallel with malignancy grade even if the density of chymase-positive mast cells was significantly lower than the density of tryptase-positive mast cells and is highly correlated with the extent of angiogenesis. This study has demonstrated that mast cell density correlates with angiogenesis and progression of patients with gastric carcinoma. Understanding the mechanisms of gastric cancer angiogenesis provides a basis for a rational approach to the development of an antiangiogenic therapy in patients with this malignancy.

The role of erythropoietin and its receptor in growth, survival and therapeutic response of human tumor cells From clinic to bench - a critical review

Recombinant human erythropoietin (rhEPO) has been used clinically to alleviate cancer- and chemotherapy-related anemia. However, recent clinical trials have reported that rhEPO also may adversely impact disease progression and survival. The expression of functional EPO receptors (EPOR) has been demonstrated in many human cancer cells where, at least in vitro, rhEPO can stimulate cell growth and survival and may induce resistance to selected therapies. Responses to rhEPO measured by alterations in tumor cell growth or survival, activation of signaling pathways or modulation of sensitivity to anticancer agents are variable. Both methodological and inherent biological issues underlie the differential cell responses, including reported difficulties in EPOR protein detection, potential involvement of EPOR isoforms or of cytoplasmic EPOR, possible differential structure and/or binding affinities of hematopoietic versus non-hematopoietic cell EPOR, possible aberrant regulation of EPOR activity, and a functional EPO/EPOR autocrine/paracrine loop. The modulation by rhEPO of tumor cell response to anticancer agents is coincident with modulation of multiple signaling pathways, BCL-2 family proteins, caspases and NFkB. The molecular interplay of pro-survival and pro-death signals, triggered by EPO and/or by anticancer agents, is multifactorial and tightly coordinated. Expression microarray analysis may prove critical for deciphering this potentially novel network and its broad spectrum of genes and proteins.

Erythropoietin and tumor angiogenesis

Erythropoietin (Epo) may be considered as an endogenous stimulator of vessel growth during tumor progression through an autocrine and/or paracrine loop. The vascular effects of Epo would be relevant in tumor angiogenesis and the negative effect of Epo on tumor growth may be aggravated by its angiogenic activity. The mechanism of tumor growth in the context of Epo is not completely clarified, and it is still not clear whether there is a direct effect of Epo in tumor cells as opposed to exogenous effect on angiogenesis. It is also possible that the effect of Epo is multifactorial depending on the type of tumor and level of functionality of Epo receptor expression in tumor cells, as well other variables such as hypoxic stress, degree of anemia, chemotherapy, radiotherapy of surgical intervention.

EPO-R expression patterns in resected gastric adenocarcinoma followed by adjuvant chemoradiation treatment

The primary aim was to determine whether Epo-R immunohistochemical expression is related to disease free survival (DFS) in specimens of GC from patients who underwent adjuvant chemoradiation. Specimens of gastric adenocarcinomas obtained from 44 patients who had undergone curative gastrectomy and adjuvant treatment were investigated immunohistochemically expression of Epo-R. Three patterns for Epo-R staining were defined: Pattern A (secretory cells-like staining), Pattern B (parietal-like staining) and Pattern C (chief-like staining). Median DFS was 38 months (CI 95%: 33-43) and 15 months (IC 95%: 3-27) in the pattern B and C, respectively, but it was not reached in the pattern A (p = 0.06). Our findings suggest that there may be a relationship between Epo-R expression and DFS in the patients with GC resected.

Erythropoietin and cancer, a double-edged sword

This editorial is focused on the double controversial action of erythropoietin, acting as anticancer agent and as a promoting cancer agent.

Unraveling the Mystery of Erythropoietin-Stimulating Agents in Cancer Promotion

Erythropoietin-stimulating agents (ESA) are approved for use in treating chemotherapy-induced anemia in patients with nonmyeloid malignancies. However, recent clinical trials have shown evidence of inferior overall survival and/or locoregional control of tumors in patients receiving ESAs. Given these concerning data, current studies are focused on elucidating the biological mechanisms by which ESAs may contribute to cancer promotion. Evidence suggests that ESAs activate several signaling pathways that are important in altering tumor behavior and response to treatment. Although further research is needed to more precisely elucidate these mechanisms, caution should be exercised in the use of ESAs beyond their approved indication in cancer patients. [Cancer Res 2008;68(11):4013–7]

Erythropoietin and erythropoietin receptor in colorectal cancer

Erythropoietin via erythropoietin receptor effectively prevents anemia, giving reasons for a clinical use of erythropoietin in patients with colorectal cancers. However, erythropoietin seems to promote survival of the neoplastic cells in hypoxic environment. The aim of this study was to evaluate immunohistochemically the expression of erythropoietin and erythropoietin receptor in 136 primary colorectal cancers with a correlation to different anatomo-clinical features. Erythropoietin correlated with erythropoietin receptor in colorectal cancers (r = 0.547, P < .00001). Erythropoietin and erythropoietin receptor expressions were statistically higher in adenocarcinomas versus mucinous carcinomas (P = .05 and P = .03, respectively) and in moderately (G2) versus poorly differentiated (G3) tumors (P = .001 and P = .02, respectively). This in vivo study is the first study that provides evidences for the presence of erythropoietin and erythropoietin receptor in human colorectal cancer. The expressions of these proteins strictly depended on grading because the better histological differentiation probably comes from trophic influence of erythropoietin and erythropoietin receptor.

Effects of recombinant erythropoietin on breast cancer-initiating cells

BACKGROUND

Cancer anemia causes fatigue and correlates with poor treatment outcome. Erythropoietin has been introduced in an attempt to correct these defects. However, five recent clinical trials reported a negative impact of erythropoietin on survival and/or tumor control, indicating that experimental evaluation of a possible direct effect of erythropoietin on cancer cells is required. Cancer recurrence is thought to rely on the proliferation of cancer initiating cells (CICs). In breast cancer, CICs can be identified by phenotypic markers and their fate is controlled by the Notch pathway.

METHODS

In this study, we investigated the effect of erythropoietin on CICs in breast cancer cell lines. Levels of erythropoietin receptor (EpoR), CD24, CD44, Jagged-1 expression, and activation of Notch-1 were assessed by flow cytometry. Self-renewing capacity of CICs was investigated in sphere formation assays.

RESULTS

EpoR expression was found on the surface of CICs. Recombinant human Epo (rhEpo) increased the numbers of CICs and self-renewing capacity in a Notch-dependent fashion by induction of Jagged-1. Inhibitors of the Notch pathway and PI3-kinase blocked both effects.

CONCLUSIONS

Erythropoietin functionally affects CICs directly. Our observation may explain the negative impact of recombinant Epo on local control and survival of cancer patients with EpoR-positive tumors.

Survival and erythropoietin receptor protein in tumours from patients randomly treated with rhEPO for palliative care

BACKGROUND

Recombinant erythropoietin (rhEPOalpha) corrects anaemia, improves physical functioning and quality of life in cancer patients. However, published reports have suggested risks for tumour stimulation by provision EPO to patients with remaining tumour cells perhaps related to the presence of EPO receptor protein in tumour tissue. Therefore, the aim of the present study was to exclude a possibility that cancer patients who respond favourably to EPO treatment have mainly tumours with low EPO receptor protein expression.

METHODS

Tumour tissue was evaluated in 87 patients out of 108 randomly allocated for treatment with rhEPOalpha (n = 50) versus controls (n = 58). Tumour cell proliferation (Ki-67 index) and EPO receptor protein expression were evaluated by immunohistochemistry.

RESULTS

EPO treatment varied between 2 and 35 months, in doses between 10,000 and 40,000 Units/week. Ki-67 index did not differ between study and control patients before EPO treatment. Tumour tissue erythropoietin receptor protein was also similar between treated and untreated patients. Around 40% of tumour cells contained EPO receptors. Survival did not differ among EPO treated and control patients analysed as intention to treat, while survival was significantly improved in EPO treated patients per protocol treatment (P < 0.05). Ki-67 index and tumour tissue erythropoietin receptor protein did not predict survival, which systemic inflammation (ESR) did (P < 0.02).

CONCLUSIONS

Our results support that reported risk to accelerate disease progression by EPO treatment in palliative care is not justified in patients with solid, gastrointestinal cancer despite tumour presence of EPO receptor protein.

Human recombinant erythropoietic agents do not induce changes in circulating levels of endoglin and vascular endothelial growth factor in anemic cancer patients

The correlation of erythropoietin (EPO) receptor levels with angiogenesis and progression in some cancers has suggested that EPO could acts directly as an angiogenic factor. The purpose of this study was to assess the effect of treatment with human recombinant erythropoietic (rHuEPO) agents in cancer patients with chemotherapy-induced anaemia on endoglin and vascular endothelial growth factor (VEGF) circulating levels as a possible marker of angiogenesis. Endoglin and VEGF were measured in serum samples from 25 cancer patients with chemotherapy-induced anemia before and after 3-4 weeks of treatment with rHuEPO. A group of 28 healthy voluntaries was used as control. VEGF serum levels were significantly higher in cancer patients than in controls. For endoglin, higher levels were observed without reaching statistical significance. No statistically significant differences in endoglin and VEGF serum levels were found between samples obtained before and after treatment with rHuEPO agents. In conclusion, our result do not support that rHuEpo treatment in anaemic cancer patients induce angiogenesis.

Upregulation of erythropoietin receptor in human prostate carcinoma and high-grade prostatic intraepithelial neoplasia

The aim of the present study was to investigate the differential expression of erythropoietin receptor (EPOR) in prostate carcinoma (PCa), high-grade prostatic intraepithelial neoplasia (PIN), prostatic hyperplasia (BPH) lesions and normal prostatic tissues by immunohistochemistry; and to test the hypothesis that upregulation of EPOR is a specific event for prostate carcinogenesis. An immunohistochemical analysis of EPOR was performed on 30 PCa, 50 BPH with/without inflammation lesions and 30 normal prostatic tissue samples. EPOR staining was quantitated and classified into normal expression and overexpression. Totally 16 high-grade PIN lesions were found in this study. Overexpression of EPOR was shown only in PCa and high-grade PIN. Statistical analysis demonstrated that higher median EPOR staining score of PCa and high-grade PIN in comparison with BPH (P < 0.05) and higher median EPOR staining score of PCa compared with high-grade PIN (P < 0.05). Our data demonstrate that upregulation of EPOR is not uncommon for PCa and upregulated EPOR in high-grade PIN suggests upregulation of EPOR is an early event for prostate carcinogenesis. The role of upregulated EPOR and possibly enhanced EPOR signaling in prostate carcinogenesis warrants further studying.

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.

Do erythropoietin receptors on cancer cells explain unexpected clinical findings?

PURPOSE

Recent reports suggest that cancer control may worsen if erythropoietin is administered. We investigated whether erythropoietin receptor expression on cancer cells may correlate with this unexpected finding.

PATIENTS AND METHODS

Cancer tissue from patients with advanced carcinoma of the head and neck (T3, T4, or nodal involvement) and scheduled for radiotherapy was assayed retrospectively for erythropoietin receptor expression by immunohistochemistry. Patients were anemic and randomized to receive epoetin beta (300 U/kg) or placebo under double-blind conditions, given three times weekly starting 10 to 14 days before and continuing throughout radiotherapy. We administered 60 Gy following complete resection or 64 Gy subsequent to microscopically incomplete resection; 70 Gy were given following macroscopically incomplete resection or for definitive radiotherapy alone. We determined if the effect of epoetin beta on locoregional progression-free survival was correlated with the expression of erythropoietin receptors on cancer cells using a Cox proportional hazards regression model.

RESULTS

We studied 154 of 157 randomly assigned patients; 104 samples were positive, and 50 were negative for receptor expression. Locoregional progression-free survival was substantially poorer if epoetin beta was administered to patients positive for receptor expression compared with placebo (adjusted relative risk, 2.07; 95% CI, 1.27 to 3.36; P < .01). In contrast, epoetin beta did not impair outcome in receptor-negative patients (adjusted relative risk, 0.94; 95% CI, 0.47 to 1.90; P = .86). The difference in treatment associated relative risks (2.07 v 0.94) was borderline statistically significant (P = .08).

CONCLUSION

Erythropoietin might adversely affect prognosis of head and neck cancer patients if cancer cells express erythropoietin receptors.

Erythropoietin biology in cancer

Erythropoietin (Epo) has long been known to be the principal hematopoietic growth factor that regulates cellular proliferation and differentiation along the erythroid lineage. Recent studies have shown that Epo is a pleiotropic cytokine that is proangiogenic and exerts broad tissue-protective effects in diverse nonhematopoietic organs. Recombinant Epo (rEpo) has been widely used in the clinic to prevent or treat malignancy-associated anemia. A series of clinical trials have documented the efficacy of rEpo in reducing RBC transfusion requirements and improving quality of life in cancer patients, and a recent meta-analysis suggested a positive effect on survival. However, two randomized trials reported negative outcomes with rEpo, as patients in the rEpo arm fared worse than their placebo-treated counterparts with respect to progression-free survival. The expression of Epo receptor (EpoR) in cancer cells has raised the possibility that exogenous rEpo may exert direct effects on tumor cells associated with the potential for stimulation of proliferation, inhibition of apoptosis, or modulation of sensitivity to chemoradiation therapy. The presence of an autocrine-paracrine Epo-EpoR system in tumors and potential effects of Epo on tumor microenvironment and angiogenesis are consistent with a complex biology for Epo-EpoR signaling in cancer that requires further research. This review describes Epo and EpoR biology, focusing on the pleiotropic effects of Epo on nonhematopoietic tissues as well as the expression and function of EpoR in cancer cells.

Is the hypoxia-inducible factor pathway important in gastric cancer?

Tumour hypoxia is well recognised in oncology to be a key factor resulting in treatment resistance and poor prognosis. Hypoxia leads to the expression of a number of gene products that are involved in tumour progression, invasion and metastasis formation. The most important of these proteins is thought to be hypoxia-inducible factor-1alpha (HIF-1alpha), which appears to be a master regulator of the cellular response to hypoxia. HIF-1alpha expression is associated with a poor prognosis and treatment response in a number of tumour sites. There is some evidence that the HIF-1alpha pathway might be involved in gastric carcinogenesis. Studies have shown reactive oxygen species from Helicobacter pylori, associated with the development of gastric cancer, stabilise HIF-1alpha. Non-steroidal anti-inflammatory drugs, shown to reduce the risk of gastric cancer, can decrease HIF-1alpha expression. Although a large study correlating HIF-1alpha expression with prognosis is lacking in gastric cancer, the immunohistochemical expression of HIF-1alpha target genes (Glut-1, VEGF, CA9, iNOS) is associated with a poor prognosis. In addition, the targeted inhibition of HIF-1alpha has been shown to inhibit the growth of gastric tumours in animals. Increased understanding of the importance of hypoxia and the HIF-1alpha pathways may therefore hold the key to prevention strategies, improved selection of patients for adjuvant therapy and new treatments for the disease.

Anti-Epo receptor antibodies do not predict Epo receptor expression

Investigators using anti-EpoR antibodies for immunoblotting and immunostaining have reported erythropoietin receptor (EpoR) expression in nonhematopoietic tissues including human tumors. However, these antibodies detected proteins of 66 to 78 kDa, significantly larger than the predicted molecular weight of EpoR (56-57 kDa). We investigated the specificity of these antibodies and showed that they all detected non-EpoR proteins. C-20 detected 3 proteins in tumor cell lines (35, 66, and 100 kDa). Sequences obtained from preparative gels had similarity to the C-20-immunizing peptide. The 66-kDa protein was a heat shock protein (HSP70) to which antibody binding was abrogated in peptide competition experiments. Antibody M-20 readily identified a 59-kDa EpoR protein. However, neither M-20 nor C-20 was suitable for detection of EpoR using immunohistochemical methods. We concluded that these antibodies have limited utility for detecting EpoR. Thus, reports of EpoR expression in tumor cells using these antibodies should be viewed with caution.

Erythropoietin promotes MCF-7 breast cancer cell migration by an ERK/mitogen-activated protein kinase-dependent pathway and is primarily responsible for the increase in migration observed in hypoxia

Recent studies indicate that cancer cells express erythropoietin receptor (EpoR). In this study, we have shown that erythropoietin (Epo) activates the mitogen-activated protein kinase, extracellular signal-regulated kinase (ERK), and promotes migration in MCF-7 breast cancer cells. Epo-stimulated MCF-7 cell migration was blocked by the MEK inhibitor PD098059 and by dominant negative MEK-1, indicating an essential role for ERK. When MCF-7 cells were exposed to hypoxia (1.0% O(2)) for 3 h, the Epo mRNA level increased 2.4 +/- 0.5-fold, the basal level of ERK activation increased, and cell migration increased 2.0 +/- 0.1-fold. Soluble EpoR and Epo-neutralizing antibody significantly inhibited hypoxia-induced MCF-7 cell migration, suggesting a major role for autocrine EpoR cell signaling. MCF-7 cell migration under hypoxic conditions was also inhibited by PD098059. These experiments identify a novel pathway by which exogenously administered Epo, and Epo that is produced locally by cancer cells under hypoxic conditions, may stimulate cancer cell migration.

Erythropoietin signaling promotes invasiveness of human head and neck squamous cell carcinoma

Erythropoietin (Epo) is used for managing anemia in cancer patients. However, recent studies have raised concerns for this practice. We investigated the expression and function of Epo and the erythropoietin receptor (EpoR) in tumor biopsies and cell lines from human head and neck cancer. Epo responsiveness of the cell lines was assessed by Epoetin-alpha-induced tyrosine phosphorylation of the Janus kinase 2 (JAK2) protein kinase. Transmigration assays across Matrigel-coated filters were used to examine the effects of Epoetin-alpha on cell invasiveness. In 32 biopsies, we observed a significant association between disease progression and expression of Epo and its receptor, EpoR. Expression was highest in malignant cells, particularly within hypoxic and infiltrating tumor regions. Although both Epo and EpoR were expressed in human head and neck carcinoma cell lines, only EpoR was upregulated by hypoxia. Epoetin-alpha treatment induced prominent JAK2 phosphorylation and enhanced cell invasion. Inhibition of JAK2 phosphorylation reduced both basal and Epo-induced invasiveness. Our findings support a role for autocrine or paracrine Epo signaling in the malignant progression and local invasiveness of head and neck cancer. This mechanism may also be activated by recombinant Epo therapy and could potentially produce detrimental effects in rhEpo-treated cancer patients.

An association between preoperative anemia and decreased survival in early-stage non–small-cell lung cancer patients treated with surgery alone

PURPOSE

Surgical resection is the mainstay of therapy for patients presenting with Stage I and II non-small-cell lung cancer (NSCLC). Despite optimal staging and surgery, these patients are still at significant risk for failure. The purpose of this study is to report a retrospective analysis of the outcome of patients treated with surgery alone, as well as to analyze prognostic factors associated with survival.

MATERIALS AND METHODS

From May 2000 to November 2002, there was a total of 125 patients who were treated with surgery for NSCLC at University of Maryland Medical Center. Of these, 82 Stage I and II patients who received surgery alone as the definitive therapy were identified. The median age of the entire cohort was 68 years (range, 43-88 years). There were 48 males and 34 females. Sixty-three patients (76.8%) underwent lobectomies whereas 19 patients (23.2%) underwent nonlobectomy (wedge resection or segmentectomy) procedures. Patients who received neoadjuvant or adjuvant radiation therapy or chemotherapy were excluded from the study. Factors included in univariate and multivariate analyses were age, sex, tumor histology, pathologic stage, p53 status, preoperative hemoglobin (Hgb), and type of surgery performed. Endpoints of the study were relapse-free survival (RFS) and overall survival (OS).

RESULTS

Median follow-up was 20.8 months (range, 0.4-43.2 months). For the entire cohort, the 2-year RFS was 66.0% and 2-year OS was 76.3%. Median survival for the entire cohort has not been achieved. In univariate analysis, the only factor that achieved statistical significance was preoperative Hgb level. Patients who had preoperative Hgb <12 mg/dL experienced significantly worse RFS (mean RFS: 26.6 months vs. 34.9 months, p = 0.043) and OS (median OS: 27 months vs. 42.5 months, p = 0.011). For Stage I patients (n = 72), the 2-year RFS and OS were 66.4% and 77.1%, respectively. In the subgroup of stage IA patients (n = 37), there was a trend toward decreased overall survival in the anemic patients (2-year OS of 65.6% vs. 90.9%, p = 0.07). For Stage II patients (n = 10), the 2-year RFS and OS were 60.0% and 66.7%. In the Cox multivariate regression analysis, the only factor that achieved statistical significance was preoperative Hgb, with patients with Hgb <12 mg/dL having decreased RFS (RR 4.1, p = 0.020) and OS (RR 2.9, p = 0.026). There was a trend toward worse RFS (p = 0.056) and OS (p = 0.068) in p53-negative patients (n = 39). Stage, histologic type, type of surgery performed, age, and sex did not affect outcome.

CONCLUSIONS

In our cohort of mostly Stage I NSCLC patients treated with surgery only, preoperative Hgb <12 mg/dL predicted for worse outcome. This effect was observed even in the traditionally low-risk subgroup of completely resected stage IA patients. Much has been written in the literature about anemia causing possible worsening of tumor hypoxia within solid tumors, thereby increasing radio-resistance. This has been a popular argument to explain poorer outcomes of anemic patients with solid tumors who undergo radiotherapy. However, our data suggest that anemia may be a sign of a more aggressive tumor that is at an increased risk of failure independent of the treatment modality.

Erythropoietin and erythropoietin receptor expression in human prostate cancer

Erythropoietin is a hematopoietic cytokine that regulates the production of red blood cells. Erythropoietin is normally produced in the adult kidney in a hypoxia-inducible manner. The recombinant form of human erythropoietin is in clinical use for the prevention and treatment of anemia that is associated with cancer and its treatment with chemoradiation therapy. A series of recent studies from our laboratory and others have reported the expression of receptors for erythropoietin in several different types of human cancer cells. In the present study, we investigated the expression of erythropoietin receptor and its ligand erythropoietin in human prostate cancer. In clinical specimens of prostate cancer, we found abundant expression of erythropoietin receptor protein in all primary tumors examined using immunohistochemistry. Furthermore, we observed erythropoietin coexpression in prostate cancer cells by immunohistochemical analysis. To determine whether monolayer cultures of continuous cell lines derived from prostate cancer also express erythropoietin receptor and erythropoietin, we studied well-characterized hormone-responsive (LNCaP) and hormone-refractory (PC-3) prostate cancer cell lines. We performed reverse-transcription and polymerase chain reaction assays to detect erythropoietin receptor and erythropoietin mRNA transcripts, and also immunoprecipitation and immunoblotting to detect erythropoietin receptor protein expression in prostate cancer cells. These experiments revealed the expression of both erythropoietin receptor and erythropoietin in LNCaP and PC-3 cells suggesting that these prostate cancer cell lines may serve as useful experimental models for further studies of erythropoietin and erythropoietin receptor function in prostate cancer. The coexpression of erythropoietin receptor and its ligand erythropoietin in human prostate cancer cells suggests the potential for growth regulation by erythropoietin-erythropoietin receptor in an autocrine or paracrine manner.

Erythropoietin and Erythropoietin Receptor Expression in Head and Neck Cancer: Relationship to Tumor Hypoxia

Purpose: Erythropoietin, an oxygen-regulated glycoprotein hormone, is a hematopoietic cytokine that stimulates erythropoiesis by binding to its cellular receptor [erythropoietin receptor (EPOR)]. The recombinant form of human erythropoietin is used to prevent or treat anemia in cancer patients. However, in a recent randomized, placebo-controlled trial involving patients receiving curative radiotherapy for squamous cell carcinoma of the head and neck, erythropoietin treatment was associated with poorer locoregional progression-free survival. The purpose of our study was to determine whether EPOR and its ligand erythropoietin are expressed in primary head and neck cancer. We also investigated the hypothesis that erythropoietin expression in malignant cells may be associated with the presence of tumor hypoxia, an important factor involved in resistance to radiation treatment, tumor aggressiveness, and poor prognosis.

Experimental Design: Twenty-one patients received an i.v. infusion of the hypoxia marker pimonidazole hydrochloride before multiple tumor biopsies. Contiguous sections from 74 biopsies were analyzed by immunohistochemistry for EPOR and erythropoietin expression and pimonidazole binding.

Results: EPOR expression was present in tumor cells in 97% of the biopsies. Coexpression of erythropoietin was observed in 90% of biopsies. Erythropoietin and pimonidazole adduct staining did not always colocalize within tumors, but there was a significant positive correlation between levels of microregional erythropoietin expression and pimonidazole binding.

Conclusions: The coexpression of erythropoietin and EPOR in tumor cells suggests that erythropoietin may potentially function as an autocrine or paracrine factor in head and neck cancer. The expression of the hypoxia-inducible protein erythropoietin in tumor cells correlates with levels of tumor hypoxia.

The erythropoietin-receptor pathway modulates survival of cancer cells

Anemia in cancer patients is associated with reduced quality of life and local failure after radiation treatment. However, the use of erythropoietin to correct cancer anemia and to improve radiation efficacy was disappointing. Erythropoietin-receptor signaling mainly acts via activation of STAT 5, but also crossactivates the antiapoptotic transcription factor NF-kappaB. This causes neuroprotection against oxidative stress and implies radioprotection. In order to investigate possible radioprotective effects of erythropoietin-receptor signaling, we used an in vitro model system employing HeLa TetOff cells, stably transfected with an expression vector for the erythropoietin-receptor gene. Using electrophoretic mobility shift assays, we could demonstrate strong activation of NF-kappaB by erythropoietin-receptor signaling in HeLa cells. Activation of NF-kappaB did not require degradation of IkappaBalpha and was not prevented by proteasome inhibition. Furthermore, stimulation with erythropoietin resulted in a 50% increased clonogenicity of erythropoietin-receptor-expressing cells but did not alter radiation sensitivity itself. As most human tumors express erythropoietin receptor, we advocate a restricted use erythropoietin to patients suffering from erythropoietin-receptor-expressing cancers.

The role of erythropoietin in regulating angiogenesis

Erythropoietin (EPO) is an essential growth factor that regulates erythrocyte production in mammals. In this study, we demonstrate a novel role of EPO in regulating angiogenesis in vivo. Epo and Epo receptor (EpoR) are expressed in the vasculature during embryogenesis. Deletion of Epo or EpoR leads to angiogenic defects starting at E10.5, 2 days before ventricular hypoplasia and 3 days before the onset of the embryonic lethal phenotype. Overall, angiogenesis was severely affected in the mutant embryos: vascular anomalies included decreased complexity of the vessel networks. However, de novo vasculogenesis remained intact, consistent with the differential expression of Epo and EpoR during the early stages of embryonic development. The aforementioned angiogenesis defect can be partially rescued by expressing human EPO during embryogenesis. Moreover, Ang-1 expression is regulated by EPO/EPOR under normoxic conditions. Taken together, our results suggest important roles of EPO and EPOR in angiogenesis.

Treatment of cancer-related anemia with epoetin alfa: a review

Erythropoietin (EPO) is a hematopoietic growth hormone that regulates survival, proliferation, and differentiation of erythroid progenitor cells. A reduction in tissue oxygenation stimulates EPO production, through a complex feedback mechanism. Patients with cancer-related anemia have an inadequate EPO response that is further impaired by cancer treatments such as chemotherapy. Cancer-related anemia substantially impairs patient functioning and may contribute to poor treatment outcomes. A significant number of studies demonstrates that treatment of anemia in cancer patients using recombinant human EPO (rHuEPO, epoetin alfa) significantly increases haemoglobin (Hb) levels, reduces transfusion requirements, and improves quality of life, particularly by relieving fatigue. Recent data also show that epoetin alfa therapy may improve cognitive function in patients receiving chemotherapy. In addition, the correction of anemia may prolong survival by enhancing tumor oxygenation, thus increasing tumor sensitivity to chemotherapy or radiation. The indicated dose of epoetin alfa is 150-300 IU/kg three times per week, but it is commonly dosed at 40,000-60,000 IU once weekly based on trial data and extensive clinical use. Determining the timing of initiation of epoetin alfa is a clinical judgement; however, data suggest that patient functioning declines and the risk of transfusion increases when the Hb level falls under 12 g/dL.

Increased expression of erythropoietin receptor on blood vessels in the human epileptogenic hippocampus with sclerosis

Microvascular (capillary) proliferation is a readily observed, but largely ignored phenomenon of the mesial temporal lobe epilepsy (MTLE) hippocampus. Here, we report that the proliferated capillaries in surgically resected MTLE hippocampi were strongly immunoreactive for erythropoietin receptor (EPO-r). Further, we found that these capillaries were most prominent in areas of the MTLE hippocampus with extensive neuronal loss and gliosis, i.e. the CA3, CA1, and dentate hilus. High-resolution immunogold electron microscopy revealed that the capillary EPO-r was localized to the luminal and abluminal plasma membrane of endothelial cells, to endosome-like structures of these cells, and to pericapillary astrocytic end-feet. Previous studies have shown that systemically administered EPO appears in the cerebrospinal fluid in experimental animals, and the present results are consistent with the idea that EPO enters the brain via receptor-mediated endocytosis. The enrichment of EPO-r shown here suggests a highly efficient uptake of plasma EPO into the MTLE hippocampus and a possible role for this cytokine in epileptogenesis. Moreover, the presence of EPO-r in the MTLE hippocampus may provide a new vehicle for highly efficient delivery of hitherto impermeable drugs into the epileptic brain.

Plasma angiopoietin-1, angiopoietin-2 and Tie-2 in breast and prostate cancer: a comparison with VEGF and Flt-1

BACKGROUND

Angiogenesis is essential for tumour growth and metastasis, and is coordinated by several classes of growth factors mediating their effect through receptors linked, in turn, to tyrosine kinase. These growth factors include angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF), which act through receptors Flt-1 and Tie-2.

MATERIALS AND METHODS

In order to further determine abnormalities in levels of Ang-1, Ang-2, Tie-2, sFlt-1 and VEGF in human cancer (and their interrelationships), these molecules were measured in plasma from 30 patients with breast cancer, 30 patients with prostate cancer and 12 healthy controls per cancer group.

RESULTS

In breast cancer, levels of Ang-1 (P=0.0005), Ang-2 (P=0.0173), Tie-2 (P=0.0001), and VEGF (P=0.0001) were all significantly raised, and plasma levels of sFlt-1 (P=0.045) were significantly reduced compared with controls. However, in prostate cancer, only levels of VEGF and Tie-2 were significantly higher (both P=0.001). There were no significant differences between levels of any molecule between the two groups of cancer. The only difference between the healthy control groups was lower Ang-1 in the women compared with men. Significant correlations were found between levels of Ang-1 and Tie-2 both in breast (r=0.498, P=0.005) and prostate cancer (r=0.643, P=<0.001). Angiopoietin-1 was also positively correlated with Ang-2 in both breast (r=0.422, P=0.02) and prostate cancer (r=0.543, P=0.002).

CONCLUSIONS

Abnormal levels of Ang-1, Ang-2 and their receptor, Tie-2, are present in breast and prostate cancer, and their interrelationships may be important in the pathophysiology of these conditions.

Erythropoietin as an angiogenic factor

Erythropoietin (Epo) is produced by the fetal liver and adult kidney and is an essential stimulator of erythropoiesis. It has, however, been shown to modulate host cellular signal transduction pathway to perform many other functions. New sites of Epo production have been found, such as the female reproductive organs and central nervous system. This review summarizes the involvement of Epo in the regulation of angiogenesis in both normal and pathological conditions.