Blood Journal
Leading the way in experimental and clinical research in hematology

Absence of functional EpoR expression in human tumor cell lines

  1. Susan Swift1,*,
  2. Aaron R. Ellison2,
  3. Paul Kassner3,
  4. Ian McCaffery4,
  5. John Rossi4,
  6. Angus M. Sinclair1,
  7. C. Glenn Begley1, and
  8. Steven Elliott1
  1. 1 Department of Hematology and Oncology, Amgen, Inc, Thousand Oaks, CA, United States;
  2. 2 Department of Protein Science, Amgen, Inc, Thousand Oaks, CA, United States;
  3. 3 Department of Chemistry Research & Discovery, Amgen, Inc, Thousand Oaks, CA, United States;
  4. 4 Department of Medical Sciences, Amgen, Inc, Thousand Oaks, CA, United States
  1. * Corresponding author; email: sswift{at}amgen.com

Abstract

Certain oncology trials showed worse clinical outcomes in the erythropoiesis-stimulating agent (ESA) arm. A potential explanation was that ESA-activated Epo receptors (EpoR) promoted tumor cell growth. While there was supportive data from preclinical studies, those findings often employed invalidated reagents and methodologies and were in conflict with other studies. Here, we further investigate the expression and function of EpoR in tumor cell lines. EpoR mRNA levels in 209 human cell lines representing 16 tumor types were low compared to ESA-responsive positive controls. EpoR protein production was evaluated in a subset of 66 cell lines using a novel anti- EpoR antibody. EpoR positive control cells had an estimated 10,000-100,000 EpoR dimers/cell. In contrast, 54 of 61 lines had EpoR protein levels below 100 dimers/cell. Cell lines with the highest EpoR protein levels (400-3200 dimers/cell) were studied further and though one line, NCI-H661, bound detectable levels of [125I]-rHuEpo, none showed evidence of ESA-induced EpoR activation. There was no increased phosphorylation of STAT5, AKT, ERK, or S6RP with rHuEpo. Additionally, EpoR knockdown with siRNAs did not affect viability in two cell lines previously reported to express functional EpoR (A2780, SK-OV-3). These results conflict with the hypothesis that EpoR is functionally expressed in tumors.

  • Submitted October 19, 2009.
  • Accepted January 11, 2010.