Modulation of Navitoclax Sensitivity by Dihydroarteminisin-Mediated MCL-1 Repression
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ABSTRACT: Poor prognosis BCR-ABL+ B-ALL leukemic cells are highly dependent on the expression of endogenous anti-apoptotic MCL-1. However, the survival of most normal blood cells (e.g. progenitors, lymphocytes, and granulocytes) and other normal cell types (e.g. cardiomyocytes and neurons) are also exquisitely dependent on Mcl-1 gene expression, suggesting that effective therapeutic inhibition of MCL-1 could be acutely toxic, especially when combined with standard chemotherapy. Therefore, as an alternative to MCL-1 inhibition, we have identified dihydroarteminisin (DHA), a water-soluble metabolite of the anti-malarial arteminisin, which induces the down-modulation of MCL-1 protein expression by triggering an endoplasmic reticulum stress response. The DHA induced repression of MCL-1 expression renders leukemic cells highly sensitive to synergistic cell death induced by BH3-mimetic agents such as navitoclax (ABT-263) in a mouse model of BCR-ABL+ B-ALL. Furthermore, DHA also synergizes with navitoclax in human Ph+ ALL cell lines, and primary patient derived xenografts of Ph+ ALL. These data demonstrate that combining DHA with BH3-mimetic agents can improve therapeutic response in poor prognosis leukemia.
Project description:Precursor B-lineage acute lymphoblastic leukemia (pre-B ALL) can be subdivided into different categories based on genetic abnormalities. One type of pre-B ALL is characterized by the presence of the Philadelphia (Ph) chromosome, the derivative chromosome 22 that is one product of a reciprocal translocation between chromosomes 22 and 9. The 22/9 translocation fuses the 5’ part of the BCR gene to the 3’ end of the c-ABL gene. The resulting BCR/ABL fusion encodes a Bcr/Abl protein with deregulated Abl kinase activity. Two major fusion proteins are found in Ph-positive leukemias which differ in molecular weight and the size of the Bcr moiety. The P190 Bcr/Abl protein is common in Ph-positive ALL. Targeted tyrosine kinase inhibitors such as nilotinib are used therapeutically to treat this type of leukemia. The 22/9 translocation fuses the 5’ part of the BCR gene to the 3’ end of the c-ABL gene. The resulting BCR/ABL fusion encodes a Bcr/Abl protein with deregulated Abl kinase activity. Two major fusion proteins are found in Ph-positive leukemias which differ in molecular weight and the size of the Bcr moiety. The P190 Bcr/Abl protein is common in Ph-positive ALL. Targeted tyrosine kinase inhibitors such as nilotinib are used therapeutically to treat this type of leukemia.
Project description:One of the main objective of this study is to characterize Imatinib induced MSCs-mediated resistance evolution in BCR-ABL+ ALL. Tyrosine kinase inhibitor (TKI) Imatinib (IM) is used as a frontline therapy for BCR-ABL–positive (BCR-ABL+) acute lymphoblastic leukemia (ALL). However, resistance to IM therapy develops rapidly in a substantial proportion of treated patients, and the molecular mechanisms underlying the resistance are poorly understood. In this study, we identified a novel cascade of consequential events that are initiated by IM, which traverse through mesenchymal stem/stromal cells (MSCs) to leukemic cells, and lead to IM resistance. Our data showed that MSCs exposed to IM were decreased in their stemness and acquired a new functional status that enabled the formation of leukemic cell niches. These MSCs had increased expression of genes encoding chemo-attractants, adhesion molecules, and pro-survival stimulant growth factors. We found that BCR-ABL+ leukemic cells persistently exposed to IM were able to switch from BCR-ABL–driven signaling to growth factor–driven signaling for survival, and this switch was reversible. Blocking both the BCR-ABL–driven pathway and the growth factor–driven JAK pathway effectively eradicated the leukemic cell niches. Our findings illustrate TKI-induced, MSC-mediated drug resistance, suggesting an effective way to eliminate this type of drug resistance in patients with BCR-ABL+ ALL.
Project description:Chronic myelogenous leukemia (CML) is a malignant disease of the hematopoietic stem cell, characterized by the expression of the Bcr-Abl oncogene by leukemic cells. In order to analyze the molecular pathways modulated by Bcr-Abl, we have previously generated an inducible model of Bcr-Abl expression in the murine Ba/F3 cell line based on the Tet-OFF system. In the present study, through a microarray approach applied to cells grown with (Bcr-Abl-expression OFF) or without (Bcr-Abl-expression ON) doxycycline, a tetracycline analogue, we analyzed the gene expression variations upon Bcr-Abl expression. Keywords: repeat sample
Project description:One of the main objective of this study is to characterize Imatinib induced MSCs-mediated resistance evolution in BCR-ABL+ ALL. Tyrosine kinase inhibitor (TKI) Imatinib (IM) is used as a frontline therapy for BCR-ABL–positive (BCR-ABL+) acute lymphoblastic leukemia (ALL). However, resistance to IM therapy develops rapidly in a substantial proportion of treated patients, and the molecular mechanisms underlying the resistance are poorly understood. In this study, we identified a novel cascade of consequential events that are initiated by IM, which traverse through mesenchymal stem/stromal cells (MSCs) to leukemic cells, and lead to IM resistance. Our data showed that MSCs exposed to IM were decreased in their stemness and acquired a new functional status that enabled the formation of leukemic cell niches. These MSCs had increased expression of genes encoding chemo-attractants, adhesion molecules, and pro-survival stimulant growth factors. We found that BCR-ABL+ leukemic cells persistently exposed to IM were able to switch from BCR-ABL–driven signaling to growth factor–driven signaling for survival, and this switch was reversible. Blocking both the BCR-ABL–driven pathway and the growth factor–driven JAK pathway effectively eradicated the leukemic cell niches. Our findings illustrate TKI-induced, MSC-mediated drug resistance, suggesting an effective way to eliminate this type of drug resistance in patients with BCR-ABL+ ALL. Gene expression signatures were compared from triplicate samples of MSCs that were either treated with vehicle or imatinib for 32, 64 and 96 hours.
Project description:Chronic myelogenous leukemia (CML) is a malignant disease of the hematopoietic stem cell, characterized by the expression of the Bcr-Abl oncogene by leukemic cells. In order to analyze the molecular pathways modulated by Bcr-Abl, we have previously generated an inducible model of Bcr-Abl expression in the murine Ba/F3 cell line based on the Tet-OFF system. In the present study, through a microarray approach applied to cells grown with (Bcr-Abl-expression OFF) or without (Bcr-Abl-expression ON) doxycycline, a tetracycline analogue, we analyzed the gene expression variations upon Bcr-Abl expression.
Project description:BCR-Abl is a driver oncogene that causes chronic myeloid leukemia and a subset of acute lymphoid leukemias. Although tyrosine kinase inhibitors provide an effective treatment for these diseases, they generally do not kill leukemic stem cells. Leukemic stem cells are cancer-initiating cells that compete with normal hematopoietic stem cells for the bone marrow niche. Using BCR-Abl as a model oncogene, we performed a drug screen based on competition between isogenic untransformed cells and BCR-Abl-transformed cells, and identified several compounds that selectively target BCR-Abl-transformed cells. Systems-level analysis of one of these novel compounds, DJ34, revealed that it induced depletion of c-Myc and activation of p53. c-Myc depletion occurred in a wide range of tumor types, including leukemia, lymphoma, lung, glioblastoma and breast cancer. Further analyses revealed that DJ34 interferes with c-Myc synthesis at the level of transcription, and we provide data showing that DJ34 is a DNA intercalator and topoisomerase II inhibitor. Physiologically, DJ34 induced apoptosis, cell cycle arrest and cell differentiation, and primary leukemic stem cells were particularly sensitive to DJ34. Taken together, we have identified a novel compound that dually targets c-Myc and p53 in a wide variety of cancers, and with particularly strong activity against leukemic stem cells.
Project description:The BCR-ABL oncogene, generated by Philadelphia chromosome, is present in about 95% human Chronic myeloid leukemia (CML) and 20~30% acute lymphoblastic leukemia (ALL). One of BCR-ABL isoforms, P210, is more often detected in CML and ALL patients. Although BCR-ABL kinase inhibitors are effective in controlling the diseases, they do not provide cure due to the development of drug resistance and the insensitivity of leukemia stem cells to these drugs. Identification of new therapeutic targets is critical. To identify potential target against leukemia stem cells, we studied gene expression in leukemia stem cells, which were identified in mice in our lab (Hu Y, Swerdlow S, Duffy TM, Weinmann R, Lee FY, Li S. 2006. Targeting multiple kinase pathways in leukemic progenitors and stem cells is essential for improved treatment of Ph+ leukemia. Proc Natl Acad Sci USA 103(45):16870-16875.). The sorted leukemia stem cells that expressed BCR-ABL were used for isolation of RNA, followed by the analysis of gene expression using the DNA microarray. The same lineage of non-BCR-ABL-expressing normal hematopoietic stem cells was used as control. We have identified some interesting genes that are up- or down-regulated by BCR-ABL in these leukemia stem cells. We are currently studying the functions of these identified genes. Keywords: Genetic modification
Project description:MiR-142 is dynamically expressed and plays a regulatory role in hematopoiesis. Based on the simple observation that miR-142 levels are significantly lower in CD34+CD38- cells from blast crisis (BC) chronic myeloid leukemia (CML). CML patients compared with chronic phase (CP) CML patients (p=0.002), we hypothesized that miR-142 deficit plays a role in BC transformation. To test this hypothesis, we generated a miR-142 KO BCR-ABL (i.e., miR-142−/−BCR-ABL) mouse by crossing a miR-142−/− mouse with a miR-142+/+BCR-ABL mouse. While the miR-142+/+BCR-ABL mice developed and died of CP CML, the miR-142−/−BCR-ABL mice developed a BC-like phenotype in the absence of any other acquired gene mutations and died significantly sooner than miR-142+/+BCR-ABL CP controls (p=0.001). Leukemic stem cell (LSC)-enriched Lineage-Sca-1+c-Kit+ cells (LSKs) from diseased miR-142−/−BCR-ABL mice transplanted into congenic recipients, recapitulated the BC features thereby suggesting stable transformation of CP-LSCs into BC-LSCs in the miR-142 KO CML mouse. Single cell (sc) RNA-seq profiling showed that miR-142 deficit changed the cellular landscape of the miR-142−/−BCR-ABL LSKs compared with miR-142+/+BCR-ABL LSKs with expansion of myeloid-primed and loss of lymphoid-primed factions. Bulk RNA-seq analyses along with unbiased metabolomic profiling and functional metabolic assays demonstrated enhanced fatty acid β-oxidation (FAO) and oxidative phosphorylation (OxPhos) in miR-142−/−BCR-ABL LSKs vs miR-142+/+BCR-ABL LSKs. MiR-142 deficit enhanced FAO in miR-142−/−BCR-ABL LSKs by increasing the expression of CPT1A and CPT1B, that controls the cytosol-to-mitochondrial acyl-carnitine transport, a critical step in FAO. MiR-142 deficit also enhanced OxPhos in miR-142−/−BCR-ABL LSKs by increasing mitochondrial fusion and activity. As the homeostasis and activity of LSCs depend on higher levels of these oxidative metabolism processes, we then postulate that miR-142 deficit is a potentially druggable target for BC-LSCs. To this end, we developed a novel CpG-miR-142 mimic oligonucleotide (ODN; i.e., CpG-M-miR-142) that corrected the miR-142 deficit and alone or in combination with a tyrosine kinase inhibitor (TKI) significantly reduced LSC burden and prolonged survival of miR-142−/−BCR-ABL mice. The results from murine models were validated in BC CD34+CD38- primary blasts and patient-derived xenografts (PDXs). In conclusion, an acquired miR-142 deficit sufficed in transforming CP-LSCs into BC-LSCs, via enhancement of bioenergetic oxidative metabolism in absence of any additional gene mutations, and likely represent a novel therapeutic target in BC CML.
Project description:Intrinsic apoptosis is principally regulated by the BCL-2 family of proteins, but some non-BCL-2 proteins also serve as important regulators. To identify novel apoptosis regulators, we performed a genome-wide CRISPR-Cas9 library screen, and it identified the mitochondrial E3 ubiquitin ligase MARCHF5/MITOL/RNF153 as an important regulator of BAK apoptotic function. Deleting MARCHF5 in multiple BAX-deficient cell lines conferred profound resistance to BH3-mimetic drugs. The loss of MARCHF5 or its E3 ubiquitin ligase activity surprisingly drove BAK to adopt an active conformation, with resistance to BH3-mimetics afforded by the formation of inhibitory complexes with pro-survival proteins MCL-1 and BCL-XL. Importantly, these changes to BAK conformation and pro-survival association occurred independently of BH3-only proteins. This study identifies a mechanism by which MARCHF5 regulates apoptotic cell death and provides new insight into how cancer cells respond to BH3-mimetic drugs. These data also highlight the emerging role of ubiquitin signalling in apoptosis that may be exploited therapeutically.
Project description:Oncogene driven transformation of leukemic progenitors results in B-acute lymphoblastic leukemia. Genetic deletions at specific hotspots are driven by recombination of epigenetically repressed loci and cause B cell transformation, and epigenetically regulated transcriptional plasticity has been proposed as a mechanism of differentiation arrest and resistance to therapy. The upstream signals driving epigenetic silencing have not been elucidated. BCR-ABL leukemias are initiated by leukemic stem cells/progenitors, and their modeling in vivo represents an opportunity for the identification of the epigenetic progress contributing to lineage leukemogenesis. We have found that primary human and murine BCR-ABL+ leukemic progenitors have increased activation of Cdc42 and the downstream atypical protein kinase C (aPKC). While the isoform aPKCz behaves as a leukemic suppressor, aPKCl/i is critically required for oncogenic progenitor proliferation, survival, and B cell differentiation arrest, but not for normal B cell lineage differentiation. We found that in vitro and in vivo B cell transformation by BCR-ABL requires the downregulation of key genes in the B-cell differentiation program through an aPKCl/i-dependent Etv5/Satb2 chromatin repressive signaling complex. Thus genetic or pharmacological targeting of aPKC impairs human oncogenic addicted leukemias in vitro and in vivo. Therefore, the aPKCl/i-SATB2 signaling cascade is required for leukemic BCR-ABL+ B-cell progenitor transformation and is amenable to non-BCR-ABL kinase inhibition.