Expression of erythropoietin and erythropoietin receptor in non-small cell lung carcinomas.
ABSTRACT Expression of erythropoietin (Epo) and its receptor (Epo-R) has been shown in various normal and neoplastic nonhematopoietic tissues. This study, in non-small cell lung carcinoma, was designed to investigate the previously unreported expression of Epo and Epo-R as well as hypoxia-inducible factor-1alpha (HIF-1alpha), which is known to control Epo expression.
Samples from lung squamous cell carcinomas (n = 17) and adenocarcinomas (n = 12) were obtained from patients undergoing curative surgery. mRNA transcripts of Epo, Epo-R, soluble Epo-R (sEpo-R), HIF-1alpha, and factor inhibiting HIF-1 (FIH-1) were evaluated by reverse transcription-PCR, whereas localization of Epo, Epo-R, and HIF-1alpha was assessed by immunohistochemistry.
Epo, Epo-R, sEpo-R, HIF-1alpha, and FIH-1 transcripts were detected by reverse transcription-PCR in all samples tested, but with heterogeneous levels of expression for Epo, Epo-R, and sEpo-R. Coordinated levels of mRNA were observed for HIF-1alpha and FIH-1.Epo was detected in carcinomatous cells by immunohistochemistry in 50% of samples and Epo-R was detected in 96% of samples. Co-expression of Epo and Epo-R was observed on contiguous sections from 50% of tumors. HIF-1alpha was immunolocalized in 80% of non-small cell lung carcinomas.
Epo-R was expressed in almost all samples and Epo was expressed in one half of samples on immunohistochemistry and in 100% of samples by mRNA detection, suggesting a potential paracrine and/or autocrine role of endogenous Epo in non-small cell lung carcinoma. The detection of stabilized HIF-1alpha suggests a possible role in Epo expression. Moreover, in the light of these results, the potential interactions between therapeutic recombinant Epo and the putative neoplastic Epo/Epo-R signaling pathways must be considered.
- SourceAvailable from: Naihong Yan[Show abstract] [Hide abstract]
ABSTRACT: Hypoxia-inducible transcription factor-1alpha (HIF-1alpha), which plays an important role in controlling the hypoxia-induced glycolysis pathway, is a "master" gene in the tissue hypoxia response during tumor development. However, its role in the apoptosis of non-small cell lung cancer remains unknown. Here, we have studied the effects of HIF-1alpha on apoptosis by modulating HIF-1alpha gene expression in A549 cells through both siRNA knock-down and over-expression. A549 cells were transfected with a HIF-1alpha siRNA plasmid or a HIF-1alpha expression vector. Transfected cells were exposed to a normoxic or hypoxic environment in the presence or absence of 25 mM HEPES and 2-deoxyglucose (2-DG) (5 mM). The expression of three key genes of the glycolysis pathway, glucose transporter type 1(GLUT1), phosphoglycerate kinase 1(PGK1), and hexokinase 1(HK1), were measured using real-time RT-PCR. Glycolysis was monitored by measuring changes of pH and lactate concentration in the culture medium. Apoptosis was detected by TUNEL assay and flow cytometry. Knocking down expression of HIF-1alpha inhibited the glycolysis pathway, increased the pH of the culture medium, and protected the cells from hypoxia-induced apoptosis. In contrast, over-expression of HIF-1alpha accelerated glycolysis in A549 cells, decreased the pH of the culture medium, and enhanced hypoxia-induced apoptosis. These effects of HIF-1alpha on glycolysis, pH of the medium, and apoptosis were reversed by treatment with the glycolytic inhibitor, 2-DG. Apoptosis induced by HIF-1alpha over-expression was partially inhibited by increasing the buffering capacity of the culture medium by adding HEPES. During hypoxia in A549 cells, HIF-1alpha promotes activity of the glycolysis pathway and decreases the pH of the culture medium, resulting in increased cellular apoptosis.BMC Cancer 02/2006; 6(1):26. DOI:10.1186/1471-2407-6-26 · 3.32 Impact Factor
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ABSTRACT: EPO is known as an inducer of maturation and proliferation of erythrocytes. Moreover, it favours angiogenesis. In several studies it was encountered that EPO is a trophic agent that mediates survival and inhibits apoptosis of hypoxia affected cells, particularly those which build masses of irregularly vascularized cancers. The main task concerning EPO for oncologists is the choice to give or not to give recombinant EPO to anemia endangered cancer patients. EPO can do the quality of life better and cause recovery from anemia post chemotherapy and radiation of cancer patients. Nevertheless, EPO therapy shortens survival of patients in some cancers, in which antiapoptotic effect of EPO predominates directly in malignant cells. Thus, separately in every type of cancer, therapeutic use of recombinant EPO calls for prior investigations, if EPO signaling causes proliferation of cancer cells by direct stimulation of EPOR positive malignant cells. Unless the proliferative effect of EPO on cancer cells is excluded, its use in the therapy of anemia in cancer patients is not quite safe.Prague medical report 02/2006; 107(3):281-9.
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ABSTRACT: We investigated the significance of erythropoietin receptor (EPOR) expression following treatment with recombinant human erythropoietin (rHuEPO; epoetin alpha) and the effect of recombinant epoetins (epoetin alpha, epoetin beta, and darbepoetin alpha) alone or in combination with anticancer therapy on tumor growth in two well-established preclinical models of breast carcinoma (MDA-MB-231 and MCF-7 cell lines). Expression and localization of EPOR under hypoxic and normoxic conditions in MDA-MB-231 and MCF-7 cells were evaluated by immunoblotting, flow cytometry, and immunohistochemistry. EPOR binding was evaluated using [125I]rHuEPO. Proliferation, migration, and signaling in MDA-MB-231 and MCF-7 cells following treatment with rHuEPO were evaluated. Tumor growth was assessed following administration of recombinant epoetins alone and in combination with paclitaxel (anticancer therapy) in orthotopically implanted MDA-MB-231 and MCF-7 breast carcinoma xenograft models in athymic mice. EPOR expression was detected in both tumor cell lines. EPOR localization was found to be exclusively cytosolic and no specific [125I]rHuEPO binding was observed. There was no stimulated migration, proliferation, or activation of mitogen-activated protein kinase and AKT following rHuEPO treatment. In mice, treatment with recombinant epoetins alone and in combination with paclitaxel resulted in equivalent tumor burdens compared with vehicle-treated controls. Results from our study suggest that although EPOR expression was observed in two well-established breast carcinoma cell lines, it was localized to a cytosolic distribution and did not transduce a signaling cascade in tumors that leads to tumor growth. The addition of recombinant epoetins to paclitaxel did not affect the outcome of paclitaxel therapy in breast carcinoma xenograft models. These results show that recombinant epoetins do not evoke a physiologic response on EPOR-bearing tumor cells as assessed by numerous variables, including growth, migration, and cytotoxic challenge in preclinical in vivo tumor models.Molecular Cancer Therapeutics 03/2006; 5(2):347-55. DOI:10.1158/1535-7163.MCT-05-0203 · 6.11 Impact Factor