| 16446383 |
Radomska HS, Basseres DS, Zheng R, Zhang P, Dayaram T, Yamamoto Y, Sternberg DW, Lokker N, Giese NA, Bohlander SK, Schnittger S, Delmotte MH, Davis RJ, Small D, Hiddemann W, Gilliland DG, Tenen DG: Block of C/EBP alpha function by phosphorylation in acute myeloid leukemia with FLT3 activating mutations. J Exp Med. 2006 Feb 20;203(2):371-81. Epub 2006 Jan 30.
Mutations constitutively activating FLT3 kinase are detected in approximately 30% of acute myelogenous leukemia (AML) patients and affect downstream pathways such as extracellular signal-regulated kinase (ERK) 1/2. We found that activation of FLT3 in human AML inhibits CCAAT/enhancer binding protein alpha (C/EBPalpha) function by ERK1/2-mediated phosphorylation, which may explain the differentiation block of leukemic blasts. In MV4;11 cells, pharmacological inhibition of either FLT3 or MEK1 leads to granulocytic differentiation. Differentiation of MV4;11 cells was also observed when C/EBPalpha mutated at serine 21 to alanine (S21A) was stably expressed. In contrast, there was no effect when serine 21 was mutated to aspartate (S21D), which mimics phosphorylation of C/EBPalpha. Thus, our results suggest that therapies targeting the MEK/ERK cascade or development of protein therapies based on transduction of constitutively active C/EBPalpha may prove effective in treatment of FLT3 mutant leukemias resistant to the FLT3 inhibitor therapies. |
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