title: Recombinant human erythropoietin alters gene expression and stimulates proliferation of MCF-7 breast cancer cells.
abstract: BACKGROUND
  Functional erythropoietin (EPO) signaling is not specific only to erythroid lineages and has been confirmed in several solid tumors, including breast. Three different isoforms of erythropoietin receptor (EPOR) have been reported, the soluble (EPOR-S) and truncated (EPOR-T) forms acting antagonistically to the functional EPOR. In this study, we investigated the effect of human recombinant erythropoietin (rHuEPO) on cell proliferation, early gene response and the expression of EPOR isoforms in the MCF-7 breast cancer cell line.
  
  
  METHODS
  The MCF-7 cells were cultured with or without rHuEPO for 72 h or 10 weeks and assessed for their growth characteristics, expression of early response genes and different EPOR isoforms. The expression profile of EPOR and EPOR-T was determined in a range of breast cancer cell lines and compared with their invasive properties.
  
  
  RESULTS
  MCF-7 cell proliferation after rHuEPO treatment was dependent on the time of treatment and the concentration used. High rHuEPO concentrations (40 U/ml) stimulated cell proliferation independently of a preceding long-term exposure of MCF-7 cells to rHuEPO, while lower concentrations increased MCF-7 proliferation only after 10 weeks of treatment. Gene expression analysis showed activation of EGR1 and FOS, confirming the functionality of EPOR. rHuEPO treatment also slightly increased the expression of the functional EPOR isoform, which, however, persisted throughout the 10 weeks of treatment. The expression levels of EPOR-T were not influenced. There were no correlations between EPOR expression and the invasiveness of MCF-7, MDA-MB-231, Hs578T, Hs578Bst, SKBR3, T-47D and MCF-10A cell lines.
  
  
  CONCLUSIONS
  rHuEPO modulates MCF-7 cell proliferation in time- and concentration-dependent manner. We confirmed EGR1, FOS and EPOR as transcription targets of the EPO-EPOR signaling loop, but could not correlate the expression of different EPOR isoforms with the invasiveness of breast cancer cell lines.
authors.affiliation: Center for Functional Genomics and Bio-chips, Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Slovenia.
authors.forename: Nina
authors.initials: N
authors.lastname: Trost
authors.forename: Tina
authors.initials: T
authors.lastname: Stepisnik
authors.forename: Sabina
authors.initials: S
authors.lastname: Berne
authors.forename: Anja
authors.initials: A
authors.lastname: Pucer
authors.forename: Toni
authors.initials: T
authors.lastname: Petan
authors.forename: Radovan
authors.initials: R
authors.lastname: Komel
authors.forename: Natasa
authors.initials: N
authors.lastname: Debeljak
keywords: breast cancer; erythropoietin; erythropoietin receptor isoforms; gene expression; proliferation