Erythropoietin and its receptor in breast cancer: correlation with steroid receptors and outcome.

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.