Expression of erythropoietin receptor and in vitro functional effects of epoetins in B-cell malignancies.
OBJECTIVE
Erythropoietin (EPO) and EPO receptor (EPO-R) expression have been reported in solid tumors and are claimed to regulate tumor growth; however, no data have been published on this issue in B-cell malignancies or normal lymphoid cells. This report describes genomic/protein EPO-R expression and in vitro effects of recombinant human EPO (epoetin) in B-cell chronic lymphocytic leukemia (B-CLL), mantle-cell lymphoma (MCL), and multiple myeloma (MM).


METHODS
Blood samples were obtained from patients with B-CLL, MCL, and healthy volunteers, and bone marrow was obtained from MM patients. EPO-R mRNA was detected by reverse transcription-PCR. EPO-R surface expression was investigated by flow cytometry using digoxigenin-labeled epoetin and polyclonal rabbit anti-EPO-R antibody for intracellular receptor. Tumor cell stimulation was determined in vitro using [(3)H]thymidine incorporation and CD69 expression after exposure to epoetin alpha or beta or darbepoetin alpha.


RESULTS
EPO-R mRNA was detected in mononuclear cells from 32 of 41 (78%) B-CLL and 5 of 7 (71%) MCL patients, and 21 of 21 (100%) MM samples. Expression was also detected in highly purified T cells from six of eight B-CLL patients, four of four MM patients, and normal donor B and T cells. Surface EPO-R protein was not detected. Intracellular EPO-R staining with anti-EPO-R antibodies was unspecific. No tumor-stimulatory effect was observed with high epoetin concentrations.


CONCLUSIONS
EPO-R gene is frequently expressed in lymphoid malignancies and normal B and T cells. However, there was no surface protein expression and no epoetin-induced in vitro stimulation of tumor B cells, indicating that epoetin therapy in vivo is likely to be safe in patients with lymphoid malignancies.
Kokhaei
Parviz
P
Department of Oncology, Karolinska Institutet, Stockholm, Sweden.
Abdalla
Amir Osman
AO
Hansson
Lotta
L
Mikaelsson
Eva
E
Kubbies
Manfred
M
Haselbeck
Anton
A
Jernberg-Wiklund
Helena
H
Mellstedt
Håkan
H
Osterborg
Anders
A
D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000096:biosynthesis; D004921:Erythropoietin / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D037181:Lectins, C-Type; D015448:Leukemia, B-Cell / Q000378:metabolism*; D020522:Lymphoma, Mantle-Cell / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D017467:Receptors, Erythropoietin / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099192:CD69 Antigens
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D004921:Erythropoietin; D037181:Lectins, C-Type; D012333:RNA, Messenger; D017467:Receptors, Erythropoietin; D000099192:CD69 Antigens