Increased Levels of Erythropoietin in Nipple Aspirate Fluid and in Ductal Cells from Breast Cancer Patients

BACKGROUND Erythropoietin (Epo) is an important regulator of erythropoiesis, and controls proliferation and differentiation of both erythroid and non-erythroid tissues. Epo is actively synthesized by breast cells during lactation, and also plays a role in breast tissues promoting hypoxia-induced cancer initiation. Our aims are to perform an exploratory investigation on the Epo accumulation in breast secretions from healthy and cancer patients and its localization in breast cancer cells. METHODS Epo was determined by ELISA, immunoprecipitation, western blot and immunocytochemical analyses in 130 Nipple Aspirate Fluids (NAF) from 102 NoCancer and 28 Breast Cancer (BC) patients, comparing results with those found in 10 milk, 45 serum samples and breast cancer cell lines. RESULTS Epo levels in NAFs were significantly higher than those in milk and serum. No difference in Epo electrophoretic mobility was found among NAF, milk and serum samples, and conditioned cell culture medium. Immunolocalization of intracellular Epo in ductal cells floating in BC NAFs was similar to those of cancer cell lines. No significant correlation between TNM classification and Epo in NAFs from BC patients was found. Significantly higher Epo concentration was found in NAF from BC patients compared to NoCancer. CONCLUSION We demonstrate that breast epithelial cells are a source of Epo in breast microenvironment, suggesting the presence of a paracrine/autocrine Epo function in NAFs, triggering off intracellular signaling cascade with subsequent BC initiation.