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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    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.
    Cancer 09/2007; 110(3):477-88. DOI:10.1002/cncr.22832 · 4.89 Impact Factor
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    ABSTRACT: Autocrine/paracrine erythropoietin (EPO) action, promoting cell survival and mediated by its receptor (EPOR) in various solid tumors, including breast carcinoma, questions about the prognostic and therapeutic interest of this system. The expression of EPO/EPOR is steroid dependent in some tissues; however, a clear relationship of EPO/EPOR and steroid receptors in breast cancer has not been established thus far. Recently, the field of steroid receptors has expanded, including rapid effects mediated by membrane-associated receptors, regulating cell survival or apoptosis. The aim of this study was to evaluate EPO/EPOR and membrane-associated steroid receptor expression in breast carcinoma, in view of their prognostic significance, compared with other established markers [estrogen receptor (ER)-progesterone receptor (PR) status and Her2 expression] and hypoxia-induced factor 1 nuclear localization in 61 breast cancer specimens followed for <or=90 months. We report that EPO-EPOR were expressed in 80% and 84% of samples, although 8% and 2% of nontumoral fields expressed EPO/EPOR too. Membrane-associated receptors for estrogen (mER), progesterone (mPR), and androgen (mAR) were expressed in 96%, 94%, and 93% of cases. Significant correlations between EPO-hypoxia-induced factor 1alpha, mER-ER, mER-EPO, mAR-EPOR, and mER-mPR-Her2 were found. Finally, EPO, EPOR, and mAR are inversely related to disease-free and overall survival. However, in view of the above correlations, we conclude that EPO/EPOR and membrane steroid receptors are not independent prognostic markers as they are closely related to other established markers. In contrast, they may represent possible new therapeutic targets.
    Cancer Epidemiology Biomarkers & Prevention 10/2007; 16(10):2016-23. DOI:10.1158/1055-9965.EPI-06-1023 · 4.13 Impact Factor
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    Journal of Clinical Oncology 10/2007; 25(27):4326; author reply 4326-7. DOI:10.1200/JCO.2007.13.0419 · 18.43 Impact Factor
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