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Are Erythropoietin Receptors Expressed in Tumors? Facts and Fiction--More Careful Studies Are Needed

Journal of Clinical Oncology (Impact Factor: 18.43). 06/2007; 25(13):1813-4; author reply 1815. DOI: 10.1200/JCO.2006.09.7253
Source: PubMed

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    • "Those studies that reportedly detected EpoR protein in nonhematopoietic cells were performed with anti-EpoR antibodies using a range of techniques including western blot, immunohistochemistry (IHC) and flow cytometry. However, a recent analysis of commonly used anti-EpoR antibodies revealed that they detected multiple non-EpoR proteins in western blots and stained both EpoR positive and EpoR negative cells similarly in IHC experiments thereby giving false-positive signals (Elliott et al., 2006a; Brown et al., 2007; Della Ragione et al., 2007; Kirkeby et al., 2007; Sturiale et al., 2007; Laugsch et al., 2008; Agarwal et al., 2007). One antibody used in many of those studies was an anti-peptide polyclonal, C20 (Santa Cruz Inc) that stained a 66 kDa protein, shown to be heat shock protein 70 but misidentified as EpoR (Elliott et al., 2006a) raising questions about the significance of positive western and IHC data generated with that antibody. "
    [Show abstract] [Hide abstract] ABSTRACT: Erythropoietin (Epo) binds and activates the Epo receptor (EpoR) on the surface of erythroid progenitor cells resulting in formation of erythrocytes. Recently, EpoR was reported to be expressed on non-erythroid cells suggesting a role for Epo outside of erythropoiesis. However those studies employed antibodies with questionable specificity and the significance of the observations are controversial. In order to accurately determine the expression of EpoR proteins in cells, we have generated a panel of novel anti-human EpoR monoclonal antibodies. One of these antibodies (A82) was particularly sensitive and it detected the EpoR protein on intact cells by flow cytometry and by western blot analysis with cell lysates. Both methods were optimized and using them, EpoR protein was detected by western immunoblotting with lysates from fewer than 200 EpoR positive control cells and the positive signals were proportional to EpoR protein expression level with a minimal signal in EpoR negative cells. The proteins detected by western blot analysis using A82 included full-length EpoR ( approximately 59kDa) as well as smaller EpoR fragments derived from the EPOR gene. These results indicate that A82 can be used to examine low level EpoR expression in cells by western and flow cytometry allowing an improved understanding of EpoR expression and metabolism.
    Full-text · Article · Nov 2009 · Journal of immunological methods
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    [Show abstract] [Hide abstract] ABSTRACT: 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.
    Full-text · Article · Sep 2007 · Cancer
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