The kinases IKBKE and TBK1 regulate MYC-dependent survival pathways through YB-1 in AML and are targets for therapy

To identify novel therapeutic targets in acute myeloid leukemia (AML), we examined kinase expression patterns in primary AML samples. We found that the serine/threonine kinase IKBKE, a noncanonical IkB kinase, is expressed at higher levels in myeloid leukemia cells compared with normal hematopoietic cells. Inhibiting IKBKE, or its close homolog TANK-binding kinase 1 (TBK1), by either short hairpin RNA knockdown or pharmacological compounds, induces apoptosis and reduces the viability of AML cells. Using gene expression profiling and gene set enrichment analysis, we found that IKBKE/TBK1-sensitive AML cells typically possess an MYC oncogenic signature. Consistent with this finding, the MYC oncoprotein was significantly downregulated upon IKBKE/TBK1 inhibition. Using proteomic analysis, we found that the oncogenic gene regulator YB-1 was activated by IKBKE/TBK1 through phosphorylation, and that YB-1 binds to the MYC promoter to enhance MYC gene transcription. Momelotinib (CYT387), a pharmacological inhibitor of IKBKE/TBK1, inhibits MYC expression, reduces viability and clonogenicity of primary AML cells, and demonstrates efficacy in a murine model of AML. Together, these data identify IKBKE/TBK1 as a promising therapeutic target in AML.