Targeting CDK1 promotes FLT3-activated acute myeloid leukemia differentiation through C/EBPα
Hanna S. Radomska, Meritxell Alberich-Jordà, Britta Will, David Gonzalez, Ruud Delwel, Daniel G. Tenen
Hanna S. Radomska, Meritxell Alberich-Jordà, Britta Will, David Gonzalez, Ruud Delwel, Daniel G. Tenen
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Research Article Oncology

Targeting CDK1 promotes FLT3-activated acute myeloid leukemia differentiation through C/EBPα

Abstract

Mutations that activate the fms-like tyrosine kinase 3 (FLT3) receptor are among the most prevalent mutations in acute myeloid leukemias. The oncogenic role of FLT3 mutants has been attributed to the abnormal activation of several downstream signaling pathways, such as STAT3, STAT5, ERK1/2, and AKT. Here, we discovered that the cyclin-dependent kinase 1 (CDK1) pathway is also affected by internal tandem duplication mutations in FLT3. Moreover, we also identified C/EBPα, a granulopoiesis-promoting transcription factor, as a substrate for CDK1. We further demonstrated that CDK1 phosphorylates C/EBPα on serine 21, which inhibits its differentiation-inducing function. Importantly, we found that inhibition of CDK1 activity relieves the differentiation block in cell lines with mutated FLT3 as well as in primary patient–derived peripheral blood samples. Clinical trials with CDK1 inhibitors are currently under way for various malignancies. Our data strongly suggest that targeting the CDK1 pathway might be applied in the treatment of FLT3ITD mutant leukemias, especially those resistant to FLT3 inhibitor therapies.

Authors

Hanna S. Radomska, Meritxell Alberich-Jordà, Britta Will, David Gonzalez, Ruud Delwel, Daniel G. Tenen

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Figure 4

Granulocytic differentiation of FLT3ITD cells after CDK1 inhibition.

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Granulocytic differentiation of FLT3ITD cells after CDK1 inhibition. (A)...
(A) Inhibition of CDK1 but not CDK2/CDK5 leads to hypophosphorylation of C/EBPα on serine 21. MOLM-14 cells were treated with CDK1 inhibitors NU6102 (lane 3), flavopiridol (flavo; lanes 6–7), or roscovitine (rosco; lanes 8–9) for 18 hours at the concentrations indicated. For control, cells were treated with DMSO (lanes 1 and 5). Treatment with the FLT3 inhibitor MLN518 (lane 2) was used for a positive control. Lane 4 shows cells cultured in the presence of CDK2/CDK5 inhibitor PNU 112455A (PNU). Shown is a Western blot stained with antibodies indicated. (B) Morphological differentiation of MOLM-14 cells treated with CDK1 inhibitors. Cells were either untreated or treated with 0.1% DMSO for 3 days (DMSO), 10 mM PNU112455A for 3 days (PNU112455A), 10 mM NU6102 for 3 days (NU6102), 12.5 mM roscovitine for 2 days, or 100 nM flavopiridol for 2 days (flavo). Cytospin was stained with Wright-Giemsa. Red arrowheads point to the cells displaying granulocytic maturation. Original magnification, ×40. (C) Downregulation of c-myc expression in response to CDK1 inhibition. MOLM-14 cells were grown in the presence of the indicated drugs for 18 hours and analyzed by Western blot. (D) Increase in CD11b surface expression on MOLM-14 cells treated with CDK1 inhibitor. Cells were treated with CDK1 inhibitor NU6102 or vehicle control (0.1% DMSO) for up to 4 days and analyzed daily for the expression of CD11b by flow cytometry. Left panel: histograms obtained on day 3. Right panel: y axis indicates the percentages of CD11b+ cells during the time course.