casein-kinase-ii and Precursor-B-Cell-Lymphoblastic-Leukemia-Lymphoma

The proteasome inhibitor bortezomib is a new targeted treatment option for refractory or relapsed acute lymphoblastic leukemia (ALL) patients. However, a limited efficacy of bortezomib alone has been reported. A terminal pro-apoptotic endoplasmic reticulum (ER) stress/unfolded protein response (UPR) is one of the several mechanisms of bortezomib-induced apoptosis. Recently, it has been documented that UPR disruption could be considered a selective anti-leukemia therapy. CX-4945, a potent casein kinase (CK) 2 inhibitor, has been found to induce apoptotic cell death in T-ALL preclinical models, via perturbation of ER/UPR pathway. In this study, we analyzed in T- and B-ALL preclinical settings, the molecular mechanisms of synergistic apoptotic effects observed after bortezomib/CX-4945 combined treatment. We demonstrated that, adding CX-4945 after bortezomib treatment, prevented leukemic cells from engaging a functional UPR in order to buffer the bortezomib-mediated proteotoxic stress in ER lumen. We documented that the combined treatment decreased pro-survival ER chaperon BIP/Grp78 expression, via reduction of chaperoning activity of Hsp90. Bortezomib/CX-4945 treatment inhibited NF-κB signaling in T-ALL cell lines and primary cells from T-ALL patients, but, intriguingly, in B-ALL cells the drug combination activated NF-κB p65 pro-apoptotic functions. In fact in B-cells, the combined treatment induced p65-HDAC1 association with consequent repression of the anti-apoptotic target genes, Bcl-xL and XIAP. Exposure to NEMO (IKKγ)-binding domain inhibitor peptide reduced the cytotoxic effects of bortezomib/CX-4945 treatment. Overall, our findings demonstrated that CK2 inhibition could be useful in combination with bortezomib as a novel therapeutic strategy in both T- and B-ALL.

Topics: Antineoplastic Agents; Apoptosis; Blotting, Western; Bortezomib; Casein Kinase II; Cell Line, Tumor; Cell Survival; Drug Synergism; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum Stress; Heat-Shock Proteins; Humans; Jurkat Cells; Microscopy, Fluorescence; Naphthyridines; Neoplastic Stem Cells; Phenazines; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma; Transcription Factor RelA; Unfolded Protein Response

Topics: Casein Kinase II; Epigenesis, Genetic; Gene Expression Regulation, Neoplastic; Histone Deacetylase 1; Humans; Ikaros Transcription Factor; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma

Impaired function of the Ikaros (IKZF1) protein is associated with the development of high-risk B-cell precursor acute lymphoblastic leukemia (B-ALL). The mechanisms of Ikaros tumor suppressor activity in leukemia are unknown. Ikaros binds to the upstream regulatory elements of its target genes and regulates their transcription via chromatin remodeling. Here, we report that Ikaros represses transcription of the histone H3K4 demethylase, JARID1B (KDM5B). Transcriptional repression of JARID1B is associated with increased global levels of H3K4 trimethylation. Ikaros-mediated repression of JARID1B is dependent on the activity of the histone deacetylase, HDAC1, which binds to the upstream regulatory element of JARID1B in complex with Ikaros. In leukemia, JARID1B is overexpressed, and its inhibition results in cellular growth arrest. Ikaros-mediated repression of JARID1B in leukemia is impaired by pro-oncogenic casein kinase 2 (CK2). Inhibition of CK2 results in increased binding of the Ikaros-HDAC1 complex to the promoter of JARID1B, with increased formation of trimethylated histone H3 lysine 27 and decreased histone H3 Lys-9 acetylation. In cases of high-risk B-ALL that carry deletion of one Ikaros (IKZF1) allele, targeted inhibition of CK2 restores Ikaros binding to the JARID1B promoter and repression of JARID1B. In summary, the presented data suggest a mechanism through which Ikaros and HDAC1 regulate the epigenetic signature in leukemia: via regulation of JARID1B transcription. The presented data identify JARID1B as a novel therapeutic target in B-ALL and provide a rationale for the use of CK2 inhibitors in the treatment of high-risk B-ALL.

Topics: Casein Kinase II; Epigenesis, Genetic; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Leukemic; Histone Deacetylase 1; Humans; Ikaros Transcription Factor; Jumonji Domain-Containing Histone Demethylases; Neoplasm Proteins; Nuclear Proteins; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Repressor Proteins; Transcription, Genetic; U937 Cells

Dynamin-2 (DNM2) is a GTPase essential for intracellular vesicle formation and trafficking, cytokinesis and receptor endocytosis. Mutations in DNM2 are common in early T-cell precursor acute lymphoblastic leukemia. However, DNM2 expression in other types of ALL are not reported. We studied DNM2 mRNA level in adults with B- and T-cell ALL. We found DNM2 is more highly expressed compared with normals in both forms of ALL. High DNM2 expression is associated with some clinical and laboratory features, inferior outcomes and with leukaemia cell proliferation. We also found Ikaros directly binds the DNM2 promoter and suppresses DNM2 expression. Consequently IKZF1 deletion is associated with high DNM2 expression. Conversely, casein kinase-2 (CK2)-inhibitor increases Ikaros function thereby inhibiting DNM2 expression. Inhibiting DNM2 suppresses proliferation of leukemia cells and synergizes with CK2 inhibition. Our data indicate high DNM2 expression is associated with Ikaros dysregulation and may be important in the development of B-ALL.

Topics: Adolescent; Adult; Aged; Casein Kinase II; Cell Line, Tumor; Cell Proliferation; Dynamin II; Dynamins; Female; Gene Deletion; Gene Expression Regulation, Neoplastic; Humans; Ikaros Transcription Factor; Male; Middle Aged; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma; Prognosis; Promoter Regions, Genetic; Survival Analysis; Up-Regulation; Young Adult

Ikaros (IKZF1) is a tumor suppressor that binds DNA and regulates expression of its target genes. The mechanism of Ikaros activity as a tumor suppressor and the regulation of Ikaros function in leukemia are unknown. Here, we demonstrate that Ikaros controls cellular proliferation by repressing expression of genes that promote cell cycle progression and the phosphatidylinositol-3 kinase (PI3K) pathway. We show that Ikaros function is impaired by the pro-oncogenic casein kinase II (CK2), and that CK2 is overexpressed in leukemia. CK2 inhibition restores Ikaros function as transcriptional repressor of cell cycle and PI3K pathway genes, resulting in an antileukemia effect. In high-risk leukemia where one IKZF1 allele has been deleted, CK2 inhibition restores the transcriptional repressor function of the remaining wild-type IKZF1 allele. CK2 inhibition demonstrated a potent therapeutic effect in a panel of patient-derived primary high-risk B-cell acute lymphoblastic leukemia xenografts as indicated by prolonged survival and a reduction of leukemia burden. We demonstrate the efficacy of a novel therapeutic approach for high-risk leukemia: restoration of Ikaros tumor suppressor activity via inhibition of CK2. These results provide a rationale for the use of CK2 inhibitors in clinical trials for high-risk leukemia, including cases with deletion of one IKZF1 allele.

Topics: Animals; Apoptosis; Casein Kinase II; Cell Proliferation; Chromatin Immunoprecipitation; Enzyme Inhibitors; Female; Genes, Tumor Suppressor; Humans; Ikaros Transcription Factor; Mice; Mice, Inbred NOD; Phosphatidylinositol 3-Kinases; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

In this issue of Blood, Song et al show that tumor suppressor activity of Ikaros is achieved though repression of cell cycle and phosphatidylinositol-3 (PI3) kinase pathway genes and can be reactivated through pharmacologic inhibition of casein kinase 2 (CK2) to eradicate disease in high-risk B-cell acute lymphoblastic leukemia (B-ALL).

Topics: Animals; Casein Kinase II; Female; Genes, Tumor Suppressor; Humans; Ikaros Transcription Factor; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma

Adult B-cell acute lymphoblastic leukemia remains a major therapeutic challenge, requiring a better characterization of the molecular determinants underlying disease progression and resistance to treatment. Here, using a phospho-flow cytometry approach we show that adult diagnostic B-cell acute lymphoblastic leukemia specimens display PI3K/Akt pathway hyperactivation, irrespective of their BCR-ABL status and despite paradoxically high basal expression of PTEN, the major negative regulator of the pathway. Protein kinase CK2 is known to phosphorylate PTEN thereby driving PTEN protein stabilization and concomitant PTEN functional inactivation. In agreement, we found that adult B-cell acute lymphoblastic leukemia samples show significantly higher CK2 kinase activity and lower PTEN lipid phosphatase activity than healthy controls. Moreover, the clinical-grade CK2 inhibitor CX-4945 (Silmitasertib) reversed PTEN levels in leukemia cells to those observed in healthy controls, and promoted leukemia cell death without significantly affecting normal bone marrow cells. Our studies indicate that CK2-mediated PTEN posttranslational inactivation, associated with PI3K/Akt pathway hyperactivation, are a common event in adult B-cell acute lymphoblastic leukemia and suggest that CK2 inhibition may constitute a valid, novel therapeutic tool in this malignancy.

Topics: Adolescent; Adult; Aged; Case-Control Studies; Casein Kinase II; Cell Line; Chromosome Aberrations; Enzyme Activation; Female; Gene Expression; Humans; Immunohistochemistry; Janus Kinases; Male; Middle Aged; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Signal Transduction; STAT Transcription Factors; Young Adult