Li Zhu

All Publications

• CBP modulates sensitivity to dasatinib in pre-BCR+ acute lymphoblastic leukemia. Cancer research Duque-Afonso, J., Lin, C., Han, K., Morgens, D. W., Jeng, E. E., Weng, Z., Jeong, J., Wong, S. H., Zhu, L., Wei, M. C., Chae, H., Schrappe, M., Cario, G., Duyster, J., Sakamoto, K. M., Bassik, M. C., Cleary, M. L. 2018

  Abstract

  Dasatinib is a multi-tyrosine kinase inhibitor approved for treatment of Ph+ acute lymphoblastic leukemia (ALL), but its efficacy is limited by resistance. Recent preclinical studies suggest that dasatinib may be a candidate therapy in additional ALL subtypes including pre-BCR+ ALL. Here we utilized shRNA library screening and global transcriptomic analysis to identify several novel genes and pathways that may enhance dasatinib efficacy or mitigate potential resistance in human pre-BCR+ ALL. Depletion of the transcriptional co-activator CBP increased dasatinib sensitivity by activating transcription of the pre-BCR signaling pathway previously associated with dasatinib sensitivity. Acquired resistance was due in part to upregulation of alternative pathways including WNT through a mechanism suggesting transcriptional plasticity. Small molecules that disrupt CBP interactions with the CREB KID domain or beta-catenin showed promising preclinical efficacy in combination with dasatinib. These findings highlight novel modulators of sensitivity to targeted therapies in human pre-BCR+ ALL, which can be reversed by small molecules inhibitors. They also identify promising therapeutic approaches to ameliorate dasatinib sensitivity and prevent resistance in ALL.

  View details for PubMedID 30262461

• Brd4 regulates the expression of essential autophagy genes and Keap1 in AML cells. Oncotarget Huang, M., Zhu, L., Garcia, J. S., Li, M. X., Gentles, A. J., Mitchell, B. S. 2018; 9 (14): 11665–76

  Abstract

  We have recently reported that activation of Brd4 is associated with the presence of autophagy in NPMc+ and MLL AML cells. In order to determine the mechanisms underlying this relationship, we have examined the role of Brd4 in regulating the expression of several genes that are central to the process of autophagy. We found that Brd4 binds to the promoters of ATG 3, 7 and CEBPbeta, and expression of these genes is markedly reduced by inhibitors of Brd4, as well as by Brd4-shRNA and depletion of CEBPbeta. Inhibitors of Brd4 also dramatically suppress the transcription of Keap1, thereby increasing the expression of anti-oxidant genes through the Nrf2 pathway and reducing the cytotoxicity induced by Brd4 inhibitors. Elimination of ATG3 or KEAP1 expression using CRISPR-cas9 mediated genomic editing markedly reduced autophagy. We conclude that Brd4 plays a significant role in autophagy activation through the direct transcriptional regulation of genes essential for it, as well as through the Keap1-Nrf2 axis in NPMc+ and MLL-fusion AML cells.

  View details for PubMedID 29545928

• Autophagy mediates proteolysis of NPM1 and HEXIM1 and sensitivity to BET inhibition in AML cells. Oncotarget Huang, M., Garcia, J. S., Thomas, D., Zhu, L., Nguyen, L. X., Chan, S. M., Majeti, R., Medeiros, B. C., Mitchell, B. S. 2016

  Abstract

  The mechanisms underlying activation of the BET pathway in AML cells remain poorly understood. We have discovered that autophagy is activated in acute leukemia cells expressing mutant nucleophosmin 1 (NPMc+) or MLL-fusion proteins. Autophagy activation results in the degradation of NPM1 and HEXIM1, two negative regulators of BET pathway activation. Inhibition of autophagy with pharmacologic inhibitors or through knocking down autophagy-related gene 5 (Atg5) expression increases the expression of both NPM1 and HEXIM1. The Brd4 inhibitors JQ1 and I-BET-151 also inhibit autophagy and increase NPM1 and HEXIM1 expression. We conclude that the degradation of NPM1 and HEXIM1 through autophagy in certain AML subsets contributes to the activation of the BET pathway in these cells.

  View details for DOI 10.18632/oncotarget.12493

  View details for PubMedID 27732946

• Expression and Role of the ErbB3-Binding Protein 1 in Acute Myelogenous Leukemic Cells CLINICAL CANCER RESEARCH Le Xuan Truong Nguyen, L. X., Zhu, L., Lee, Y., Ta, L., Mitchell, B. S. 2016; 22 (13): 3320-3327

  Abstract

  The ErbB3 binding protein 1 (Ebp1) has been implicated in diverse cancers as having either oncogenic or tumor suppressor activities. The present study was undertaken to determine the effects of Ebp1 expression in AML cells and to determine the mechanisms by which Ebp1 promotes cell proliferation in these cells.The expression of Ebp1 was studied in mononuclear cells obtained from the peripheral blood of 54 patients with AML by Western blot. The effects of Ebp1 expression on Proliferating Cell Nuclear Antigen (PCNA) expression and cell proliferation was measured using Western Blot, immunoprecipitation, in vitro ubiquitination, and colony forming assays. The role of Ebp1 in promoting rRNA synthesis and cell proliferation was evaluated by measuring the level of pre-rRNA and the recruitment of Pol I to rDNA.Ebp1 is highly expressed in acute myeloid leukemia (AML) cells and regulates the level of ribosomal RNA (rRNA) synthesis by binding to RNA Polymerase I (Pol I) and enhancing the formation of the Pol I initiation complex. Ebp1 also increases the stability of proliferating cell nuclear antigen (PCNA) protein by preventing its interaction with Mdm2, for which it is a substrate.These results demonstrate an important role of Ebp1 in promoting cell proliferation in AML cells through the regulation of both rRNA synthesis and PCNA expression.

  View details for DOI 10.1158/1078-0432.CCR-15-2282

  View details for Web of Science ID 000380933900024

• ASH1L Links Histone H3 Lysine 36 Dimethylation to MLL Leukemia. Cancer discovery Zhu, L., Li, Q., Wong, S. H., Huang, M., Klein, B. J., Shen, J., Ikenouye, L., Onishi, M., Schneidawind, D., Buechele, C., Hansen, L., Duque-Afonso, J., Zhu, F., Martin, G. M., Gozani, O., Majeti, R., Kutateladze, T. G., Cleary, M. L. 2016; 6 (7): 770-783

  Abstract

  Numerous studies in multiple systems support that histone H3 lysine 36 dimethylation (H3K36me2) is associated with transcriptional activation; however, the underlying mechanisms are not well defined. Here, we show that the H3K36me2 chromatin mark written by the ASH1L histone methyltransferase is preferentially bound in vivo by LEDGF, a mixed-lineage leukemia (MLL)-associated protein that colocalizes with MLL, ASH1L, and H3K36me2 on chromatin genome wide. Furthermore, ASH1L facilitates recruitment of LEDGF and wild-type MLL proteins to chromatin at key leukemia target genes and is a crucial regulator of MLL-dependent transcription and leukemic transformation. Conversely, KDM2A, an H3K36me2 demethylase and Polycomb group silencing protein, antagonizes MLL-associated leukemogenesis. Our studies are the first to provide a basic mechanistic insight into epigenetic interactions wherein placement, interpretation, and removal of H3K36me2 contribute to the regulation of gene expression and MLL leukemia, and suggest ASH1L as a novel target for therapeutic intervention.Epigenetic regulators play vital roles in cancer pathogenesis and represent a new frontier in therapeutic targeting. Our studies provide basic mechanistic insight into the role of H3K36me2 in transcription activation and MLL leukemia pathogenesis and implicate ASH1L histone methyltransferase as a promising target for novel molecular therapy. Cancer Discov; 6(7); 770-83. ©2016 AACR.See related commentary by Balbach and Orkin, p. 700This article is highlighted in the In This Issue feature, p. 681.

  View details for DOI 10.1158/2159-8290.CD-16-0058

  View details for PubMedID 27154821

  View details for PubMedCentralID PMC4930721

• Expression and Role of the ErbB3-Binding Protein 1 in Acute Myelogenous Leukemic Cells. Clinical cancer research Nguyen, L. X., Zhu, L., Lee, Y., Ta, L., Mitchell, B. S. 2016; 22 (13): 3320-3327

  Abstract

  The ErbB3 binding protein 1 (Ebp1) has been implicated in diverse cancers as having either oncogenic or tumor suppressor activities. The present study was undertaken to determine the effects of Ebp1 expression in AML cells and to determine the mechanisms by which Ebp1 promotes cell proliferation in these cells.The expression of Ebp1 was studied in mononuclear cells obtained from the peripheral blood of 54 patients with AML by Western blot. The effects of Ebp1 expression on Proliferating Cell Nuclear Antigen (PCNA) expression and cell proliferation was measured using Western Blot, immunoprecipitation, in vitro ubiquitination, and colony forming assays. The role of Ebp1 in promoting rRNA synthesis and cell proliferation was evaluated by measuring the level of pre-rRNA and the recruitment of Pol I to rDNA.Ebp1 is highly expressed in acute myeloid leukemia (AML) cells and regulates the level of ribosomal RNA (rRNA) synthesis by binding to RNA Polymerase I (Pol I) and enhancing the formation of the Pol I initiation complex. Ebp1 also increases the stability of proliferating cell nuclear antigen (PCNA) protein by preventing its interaction with Mdm2, for which it is a substrate.These results demonstrate an important role of Ebp1 in promoting cell proliferation in AML cells through the regulation of both rRNA synthesis and PCNA expression.

  View details for DOI 10.1158/1078-0432.CCR-15-2282

  View details for PubMedID 26813358

• The H3K4-Methyl Epigenome Regulates Leukemia Stem Cell Oncogenic Potential CANCER CELL Wong, S. H., Goode, D. L., Iwasaki, M., Wei, M. C., Kuo, H., Zhu, L., Schneidawind, D., Duque-Afonso, J., Weng, Z., Cleary, M. L. 2015; 28 (2): 198-209

  Abstract

  The genetic programs that maintain leukemia stem cell (LSC) self-renewal and oncogenic potential have been well defined; however, the comprehensive epigenetic landscape that sustains LSC cellular identity and functionality is less well established. We report that LSCs in MLL-associated leukemia reside in an epigenetic state of relative genome-wide high-level H3K4me3 and low-level H3K79me2. LSC differentiation is associated with reversal of these broad epigenetic profiles, with concomitant downregulation of crucial MLL target genes and the LSC maintenance transcriptional program that is driven by the loss of H3K4me3, but not H3K79me2. The H3K4-specific demethylase KDM5B negatively regulates leukemogenesis in murine and human MLL-rearranged AML cells, demonstrating a crucial role for the H3K4 global methylome in determining LSC fate.

  View details for DOI 10.1016/j.ccell.2015.06.003

  View details for Web of Science ID 000359509200009

  View details for PubMedID 26190263

• Binding of the MLL PHD3 Finger to Histone H3K4me3 Is Required for MLL-Dependent Gene Transcription JOURNAL OF MOLECULAR BIOLOGY Chang, P., Hom, R. A., Musselman, C. A., Zhu, L., Kuo, A., Gozani, O., Kutateladze, T. G., Cleary, M. L. 2010; 400 (2): 137-144

  Abstract

  The MLL (mixed-lineage leukemia) proto-oncogene encodes a histone methyltransferase that creates the methylated histone H3K4 epigenetic marks, commonly associated with actively transcribed genes. In addition to its canonical histone methyltransferase SET domain, the MLL protein contains three plant homeodomain (PHD) fingers that are well conserved between species but whose potential roles and requirements for MLL function are unknown. Here, we demonstrate that the third PHD domain of MLL (PHD3) binds histone H3 trimethylated at lysine 4 (H3K4me3) with high affinity and specificity and H3K4me2 with 8-fold lower affinity. Biochemical and structural analyses using NMR and fluorescence spectroscopy identified key amino acids essential for the interaction with H3K4me3. Site-directed mutations of the residues involved in recognition of H3K4me3 compromised in vitro H3K4me3 binding but not in vivo localization of full-length MLL to chromatin sites in target promoters of MEIS1 and HOXA genes. Whereas intact PHD3 finger was necessary for MLL occupancy at these promoters, H3K4me3 binding was critical for MLL transcriptional activity. These results demonstrate that MLL occupancy and target gene activation can be functionally separated. Furthermore, these findings reveal that MLL not only "writes" the H3K4me3 mark but also binds the mark, and this binding is required for the transcriptional maintenance functions of MLL.

  View details for DOI 10.1016/j.jmb.2010.05.005

  View details for Web of Science ID 000279786900003

  View details for PubMedID 20452361

  View details for PubMedCentralID PMC2886590