Protein Kinase CK2 (
Casein Kinase 2 or CK2) is a constitutively active
serine-threonine kinase overactive in human
malignancies. Increased expression and activity of CK2 in
Acute Myeloid Leukemia (AML) is associated with a poor outcome. CK2 promotes AML cell survival by impinging on multiple oncogenic signaling pathways. The selective small-molecule CK2 inhibitor
CX-4945 has shown in vitro cytotoxicity in AML. Here, we report that
CX-4945 has a strong in vivo
therapeutic effect in preclinical models of AML. The analysis of genome-wide
DNA-binding and gene expression in
CX-4945 treated AML cells shows that one mechanism, by which CK2 inhibition exerts a
therapeutic effect in AML, involves the revival of IKAROS
tumor suppressor function. CK2 phosphorylates IKAROS and disrupts IKAROS' transcriptional activity by impairing
DNA-binding and association with
chromatin modifiers. Here, we demonstrate that CK2 inhibition decreases IKAROS phosphorylation and restores IKAROS binding to
DNA. Further functional experiments show that IKAROS negatively regulates the transcription of anti-apoptotic genes, including BCL-XL (
B cell Lymphoma like-2 like 1, BCL2L1).
CX-4945 restitutes the IKAROS-mediated repression of BCL-XL in vivo and sensitizes AML cells to apoptosis. Using
CX-4945, alongside the cytotoxic chemotherapeutic drug
daunorubicin, augments BCL-XL suppression and AML cell apoptosis. Overall, these results establish the in vivo therapeutic efficacy of
CX-4945 in AML preclinical models and determine the role of CK2 and IKAROS in regulating apoptosis in AML. Furthermore, our study provides functional and mechanistic bases for the addition of CK2 inhibitors to AML
therapy.