Role of the erythropoietin receptor in ETV6/RUNX1-positive acute lymphoblastic leukemia.
OBJECTIVE
We explored the mechanisms leading to the distinct overexpression of EPOR as well as the effects of EPO signaling on ETV6/RUNX1-positive acute lymphoblastic leukemias.


METHODS
ETV6/RUNX1-expressing model cell lines and leukemic cells were used for real-time PCR of EPOR expression. Proliferation, viability, and apoptosis were analyzed on cells exposed to EPO, prednisone, or inhibitors of EPOR pathways by [3H]thymidine incorporation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and Annexin V/propidium iodide staining. Western blot analysis was done to detect activation of signaling proteins. Serum EPO levels and sequences of the EPOR (n = 53) as well as hemoglobin levels were taken from children with acute lymphoblastic leukemia enrolled in Austrian protocols.


RESULTS
We show here that ectopic expression of ETV6/RUNX1 induced EPOR up-regulation. Anemia, however, did not appear to influence EPOR expression on leukemic cells, although children with ETV6/RUNX1-positive leukemias had a lower median hemoglobin than controls. Exposure to EPO increased proliferation and survival of ETV6/RUNX1-positive leukemias in vitro, whereas blocking its binding site did not alter cell survival. The latter was not caused by activating mutations in the EPOR but might be triggered by constitutive activation of phosphatidylinositol 3-kinase/Akt, the major signaling pathway of EPOR in these cells. Moreover, prednisone-induced apoptosis was attenuated in the presence of EPO in this genetic subgroup.


CONCLUSIONS
Our data suggest that ETV6/RUNX1 leads to EPOR up-regulation and that activation by EPO might be of relevance to the biology of this leukemia subtype. Further studies are, however, needed to assess the clinical implications of its apoptosis-modulating properties.
Inthal
Andrea
A
Children's Cancer Research Institute, St. Anna Kinderkrebsforschung, Vienna, Austria.
Krapf
Gerd
G
Beck
Dominik
D
Joas
Ruth
R
Kauer
Max O
MO
Orel
Lukas
L
Fuka
Gerhard
G
Mann
Georg
G
Panzer-Grümayer
E Renate
ER
D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002648:Child; D050676:Core Binding Factor Alpha 2 Subunit / Q000378:metabolism*; D004921:Erythropoietin / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics / Q000378:metabolism*; D011241:Prednisone / Q000494:pharmacology; D017467:Receptors, Erythropoietin / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000097764:ETS Translocation Variant 6 Protein
D018931:Antineoplastic Agents, Hormonal; D050676:Core Binding Factor Alpha 2 Subunit; D004921:Erythropoietin; D015514:Oncogene Proteins, Fusion; D011241:Prednisone; D017467:Receptors, Erythropoietin; C102421:TEL-AML1 fusion protein; D000097764:ETS Translocation Variant 6 Protein