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Article . 2015 . Peer-reviewed
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Clinical Significance of High C-MYC and Low MYCBP2 Expression and Their Association with Ikaros Dysfunction in Adult Acute Lymphoblastic Leukemia

Authors: Zheng, Ge; Xing, Guo; Jianyong, Li; Melanie, Hartman; Yuka Imamura, Kawasawa; Sinisa, Dovat; Chunhua, Song;

Clinical Significance of High C-MYC and Low MYCBP2 Expression and Their Association with Ikaros Dysfunction in Adult Acute Lymphoblastic Leukemia

Abstract

Abstract Objective: The Myc proteins are transcription factors with essential roles in cell growth and proliferation through their ability to regulate gene expression. MYC binding protein 2(MYCBP2) is probable E3 ubiquitin-protein ligase and its function in leukemia is undetermined. IKZF1 encodes a kruppel-like zinc finger protein Ikaros that is essential for normal hematopoiesis and acts as a tumor suppressor in acute lymphoblastic leukemia(ALL). IKZF1 deletion is associated with the development of ALL and poor clinical outcome. This study aimed to explore the expression of c-MYC and MYCBP2 and their correlation with clinical features in adult ALL, as well as the mechanism by which Ikaros directly regulates c-MYC/MYCBP2 expression in ALL. Methods: Quantitative PCR (qPCR) was performed to explore the expression of c-MYC and MYCBP2 in 151 newly diagnosed adult patients with ALL. The correlations of c-MYC/MYCBP2 expression with clinical parameters and survival status were analyzed. In addition, luciferase assay, quantitative Chromatin Immunoprecipitation (qChIP) and Ikaros shRNA knockdown were performed to further explore the mechanism underlying regulation of c-MYC/MYCBP2 expression. Results: Expression of c-MYC is significantly higher and MYCBP2 is significantly lower in both B-ALL and T-ALL patients compared with that in normal controls. C-MYC expression is also negatively co-related with the MYCBP2 in ALL cohorts. The patients with c-MYC high and MYCBP2 low expression (c-MYChigh +MYCBP2low) showed higher median white blood cell counts (WBC) (101.5×109/L vs 29.4×109/L, P =0.007), incidence of splenomegaly and liver infiltration (75.0% vs 33.3%, P =0.004;75.0% vs19.4%, P =0.000), percentage of CD34(+) and CD33(+) cells (90.0% vs 61.3%, P =0.025; 80.0% vs 25.8%, P =0.000) and a lower percentage of complete remission (CR) rate (60.0% vs 92.0%,P =0.027) compared with that of patients with c-MYC low and MYCBP2 high expression (c-MYClow +MYCBP2high). Notably, our Ikaros ChIP-seq data showed strong Ikaros binding peaks in the promoter region of both c-MYC and MYCBP2. The qChIP assay showed that Ikaros significantly binds to c-MYC and MYCBP2 promoter regions in both Nalm6 B-ALL and Molt4 T-ALL cells. Moreover, expression of Ikaros suppressed c-MYC but increased MYCBP2 expression in both Nalm6 and CEM T-ALL cells. Conversely, Ikaros knockdown induced the increase of c-MYC but decrease of MYCBP2 in Nalm6 and CEM cells. Ikaros activator,Ck2 inhibitor TBB suppress c-MYC and increase MYCBP2 expression in a dose-dependent manner in Nalm6 and CEM cells. Ikaros knockdown with shRNA could block the TBB-induced suppression of c-MYC and increase of MYCBP2 expression. These data indicated that both c-MYC and MYCBP2 are direct Ikaros targets in ALL and Ikaros regulates their expression. Importantly, we also observed Ikaros binding to c-MYC and MYCBP2 promoters in primary B-All and T-ALL. The expression of c-MYC significantly increased and MYCBP2 decreased in patients with Ikaros deletion compared to that of Ikaros wild type. These data indicated Ikaros regulatory effect on c-MYC and MYCBP2 in ALL patients and Ikaros deletion is one of the reasons for expression change of c-MYC and MYCBP2 in the patients. Conclusion: We observed the expression of c-MYC significantly increased and MYCBP2 decreased in adult ALL patients. C-MYC high and MYCBP2 low expression is correlated with high-risk leukemia. Ikaros dysfunction is one of the reasons underlying c-MYC high and MYCBP2 low expression in the patients. Our data revealed the oncogenic effect of Ikaros/MYCBP2/c-MYC on oncogenesis in adult ALL, also suggested CK2 inhibitor exert its anti-leukemia effect through Ikaros-mediated regulation on c-MYC and MYCBP2 expression in leukemia. Disclosures No relevant conflicts of interest to declare.

Related Organizations
Keywords

Adult, Male, Adolescent, Gene Expression Regulation, Leukemic, Reverse Transcriptase Polymerase Chain Reaction, Ubiquitin-Protein Ligases, Blotting, Western, Middle Aged, Precursor Cell Lymphoblastic Leukemia-Lymphoma, Proto-Oncogene Proteins c-myc, Ikaros Transcription Factor, HEK293 Cells, Cell Line, Tumor, Humans, Female, RNA Interference, Promoter Regions, Genetic, Adaptor Proteins, Signal Transducing, Aged, Protein Binding

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    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
48
Top 10%
Top 10%
Top 10%
gold