Expression of constitutively active Nuclear-κB RelA transcription factor in blasts of acute myeloid leukemia

Abstract

The nuclear transcription factor NF-κB regulates cell survival, proliferation, and differentiation. Little is known about NF-κB in myeloid malignancies. In this report, we assessed NF-κB in a group of myeloid neoplasms by using an electrophoretic mobility shift assay (EMSA) and immunofluorescence methods in freshly isolated leukemia cells. We analyzed 30 cases of acute myeloid leukemia (AML), 5 cases of myelodysplastic syndrome (MDS), 3 cases of chronic myelomonocytic leukemia (CMML), 15 cases of chronic myeloid leukemia in chronic phase (CML-CP), and 2 cases of chronic myeloid leukemia in blast crisis (CML-BC). Unstimulated cells (bone marrow and peripheral blood) from 17 normal donors and apheresis samples from 6 peripheral blood stem cell donors treated with granulocyte colony-stimulating factor (G-CSF) were used as controls. When EMSA was used, NF-κB was elevated in 14 of 30 (47%) cases of AML, in both cases of CML-BC, and in all reference donors treated with G-CSF, but it was at basal levels in all cases of MDS and CML-CP and in normal donors ( P = < .01). Immunofluorescence analysis confirmed strong nuclear RelA/NF-κB immunoreactivity in AML blasts but not in normal bone marrow. Bcl-2, a downstream molecule, was expressed in cases with elevated NF-κB, but not in cases with basal levels of NF-κB, suggesting that NF-κB is active and provides the cells with survival advantages in vivo. These results suggest that suppression of NF-κB may be a useful therapeutic strategy for a subset of patients with AML.