EPO and breast carcinoma: Three EPOR isoforms are listed in the UniProt database (http://www.uniprot.org/uniprot/P19235): a full-length functional (EPOR-F), a truncated isoform (EPOR-T) lacking the cytoplasmic region 11 and a soluble (EPOR-S) receptor that is missing the trans-membrane and cytoplasmic domains.12 EPOR-S is secreted from the cell where it competes with EPOR-F for EPO binding.13 The EPOR-T and EPOR-S isoforms most probably act as antagonists of EPOR-mediated signaling.14 All three isoforms were confirmed in breast cancer.15