title: Absence of functional EpoR expression in human tumor cell lines.
abstract: Certain oncology trials showed worse clinical outcomes in the erythropoiesis-stimulating agent (ESA) arm. A potential explanation was that ESA-activated erythropoietin (Epo) receptors (EpoRs) promoted tumor cell growth. Although there were supportive data from preclinical studies, those findings often used 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 with ESA-responsive positive controls. EpoR protein production was evaluated in a subset of 66 cell lines using a novel anti-EpoR antibody. EpoR(+) control cells had an estimated 10 000 to 100 000 EpoR dimers/cell. In contrast, 54 of 61 lines had EpoR protein levels lower than 100 dimers/cell. Cell lines with the highest EpoR protein levels (400-3200 dimers/cell) were studied further, and, although one line, NCI-H661, bound detectable levels of [(125)I]-recombinant human Epo (rHuEpo), none showed evidence of ESA-induced EpoR activation. There was no increased phosphorylation of STAT5, AKT, ERK, or S6RP with rHuEpo. In addition, EpoR knockdown with siRNAs did not affect viability in 2 cell lines previously reported to express functional EpoR (A2780 and SK-OV-3). These results conflict with the hypothesis that EpoR is functionally expressed in tumors.
authors.affiliation: Department of Hematology, Medical Sciences, Amgen Inc, Thousand Oaks, CA 91320, USA. sswift@amgen.com
authors.forename: Susan
authors.initials: S
authors.lastname: Swift
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Ellison
authors.forename: Paul
authors.initials: P
authors.lastname: Kassner
authors.forename: Ian
authors.initials: I
authors.lastname: McCaffery
authors.forename: John
authors.initials: J
authors.lastname: Rossi
authors.forename: Angus M
authors.initials: AM
authors.lastname: Sinclair
authors.forename: C Glenn
authors.initials: CG
authors.lastname: Begley
authors.forename: Steven
authors.initials: S
authors.lastname: Elliott
mesh_terms: D001483:Base Sequence; D045744:Cell Line, Tumor; D002470:Cell Survival; D017931:DNA Primers / Q000235:genetics; D004921:Erythropoietin / Q000494:pharmacology; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006397:Hematinics / Q000494:pharmacology; D006801:Humans; D008297:Male; D008954:Models, Biological; D009369:Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D017467:Receptors, Erythropoietin / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins; D015398:Signal Transduction
chemical_list: D017931:DNA Primers; D006397:Hematinics; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; D017467:Receptors, Erythropoietin; D011994:Recombinant Proteins; D004921:Erythropoietin