title: Epo receptors are not detectable in primary human tumor tissue samples.
abstract: Erythropoietin (Epo) is a cytokine that binds and activates an Epo receptor (EpoR) expressed on the surface of erythroid progenitor cells to promote erythropoiesis. While early studies suggested EpoR transcripts were expressed exclusively in the erythroid compartment, low-level EpoR transcripts were detected in nonhematopoietic tissues and tumor cell lines using sensitive RT-PCR methods. However due to the widespread use of nonspecific anti-EpoR antibodies there are conflicting data on EpoR protein expression. In tumor cell lines and normal human tissues examined with a specific and sensitive monoclonal antibody to human EpoR (A82), little/no EpoR protein was detected and it was not functional. In contrast, EpoR protein was reportedly detectable in a breast tumor cell line (MCF-7) and breast cancer tissues with an anti-EpoR polyclonal antibody (M-20), and functional responses to rHuEpo were reported with MCF-7 cells. In another study, a functional response was reported with the lung tumor cell line (NCI-H838) at physiological levels of rHuEpo. However, the specificity of M-20 is in question and the absence of appropriate negative controls raise questions about possible false-positive effects. Here we show that with A82, no EpoR protein was detectable in normal human and matching cancer tissues from breast, lung, colon, ovary and skin with little/no EpoR in MCF-7 and most other breast and lung tumor cell lines. We show further that M-20 provides false positive staining with tissues and it binds to a non-EpoR protein that migrates at the same size as EpoR with MCF-7 lysates. EpoR protein was detectable with NCI-H838 cells, but no rHuEpo-induced phosphorylation of AKT, STAT3, pS6RP or STAT5 was observed suggesting the EpoR was not functional. Taken together these results raise questions about the hypothesis that most tumors express high levels of functional EpoR protein.
authors.affiliation: Amgen Inc, Thousand Oaks, California, United States of America. selliott@amgen.com
authors.forename: Steve
authors.initials: S
authors.lastname: Elliott
authors.forename: Susan
authors.initials: S
authors.lastname: Swift
authors.forename: Leigh
authors.initials: L
authors.lastname: Busse
authors.forename: Sheila
authors.initials: S
authors.lastname: Scully
authors.forename: Gwyneth
authors.initials: G
authors.lastname: Van
authors.forename: John
authors.initials: J
authors.lastname: Rossi
authors.forename: Carol
authors.initials: C
authors.lastname: Johnson
mesh_terms: D000818:Animals; D001706:Biopsy; D045744:Cell Line, Tumor; D005189:False Positive Reactions; D005260:Female; D015870:Gene Expression; D006801:Humans; D007118:Immunoassay; D008297:Male; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D017467:Receptors, Erythropoietin / Q000032:analysis* / Q000172:deficiency / Q000235:genetics; D012680:Sensitivity and Specificity; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D009363:Neoplasm Proteins; D017467:Receptors, Erythropoietin; D014157:Transcription Factors