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    Isocitrate dehydrogenase 1 and 2 mutations induce BCL-2 dependence in acute myeloid leukemia. Chan Steven M,Thomas Daniel,Corces-Zimmerman M Ryan,Xavy Seethu,Rastogi Suchita,Hong Wan-Jen,Zhao Feifei,Medeiros Bruno C,Tyvoll David A,Majeti Ravindra Nature medicine Mutant isocitrate dehydrogenase (IDH) 1 and 2 proteins alter the epigenetic landscape in acute myeloid leukemia (AML) cells through production of the oncometabolite (R)-2-hydroxyglutarate (2-HG). Here we performed a large-scale RNA interference (RNAi) screen to identify genes that are synthetic lethal to the IDH1(R132H) mutation in AML and identified the anti-apoptotic gene BCL-2. IDH1- and IDH2-mutant primary human AML cells were more sensitive than IDH1/2 wild-type cells to ABT-199, a highly specific BCL-2 inhibitor that is currently in clinical trials for hematologic malignancies, both ex vivo and in xenotransplant models. This sensitization effect was induced by (R)-2-HG-mediated inhibition of the activity of cytochrome c oxidase (COX) in the mitochondrial electron transport chain (ETC); suppression of COX activity lowered the mitochondrial threshold to trigger apoptosis upon BCL-2 inhibition. Our findings indicate that IDH1/2 mutation status may identify patients that are likely to respond to pharmacologic BCL-2 inhibition and form the rational basis for combining agents that disrupt ETC activity with ABT-199 in future clinical studies. 10.1038/nm.3788
    Genetic characterization of ABT-199 sensitivity in human AML. Bisaillon Richard,Moison Céline,Thiollier Clarisse,Krosl Jana,Bordeleau Marie-Eve,Lehnertz Bernhard,Lavallée Vincent-Philippe,MacRae Tara,Mayotte Nadine,Labelle Caroline,Boucher Geneviève,Spinella Jean-François,Boivin Isabel,D'Angelo Giovanni,Lavallée Sylvie,Marinier Anne,Lemieux Sébastien,Hébert Josée,Sauvageau Guy Leukemia Acute myeloid leukemias (AML) with mutations in the NPM1 gene (NPM1c+) represent a large AML subgroup with varying response to conventional treatment, highlighting the need to develop targeted therapeutic strategies for this disease. We screened a library of clinical drugs on a cohort of primary human AML specimens and identified the BCL2 inhibitor ABT-199 as a selective agent against NPM1c+ AML. Mutational analysis of ABT-199-sensitive and -resistant specimens identified mutations in NPM1, RAD21, and IDH1/IDH2 as predictors of ABT-199 sensitivity. Comparative transcriptome analysis further uncovered BCL2A1 as a potential mediator of ABT-199 resistance in AML. In line with our observation that RAD21 mutation confers sensitivity to ABT-199, we provide functional evidence that reducing RAD21 levels can sensitize AML cells to BCL2 inhibition. Moreover, we demonstrate that ABT-199 is able to produce selective anti-AML activity in vivo toward AML with mutations associated with compound sensitivity in PDX models. Overall, this study delineates the contribution of several genetic events to the response to ABT-199 and provides a rationale for the development of targeted therapies for NPM1c+ AML. 10.1038/s41375-019-0485-x
    Inhibition of Mcl-1 enhances cell death induced by the Bcl-2-selective inhibitor ABT-199 in acute myeloid leukemia cells. Luedtke Daniel A,Niu Xiaojia,Pan Yihang,Zhao Jianyun,Liu Shuang,Edwards Holly,Chen Kang,Lin Hai,Taub Jeffrey W,Ge Yubin Signal transduction and targeted therapy Acute myeloid leukemia (AML) is a serious disease. The 5-year survival rates remain frustratingly low (65% for children and 26% for adults). Resistance to frontline chemotherapy (usually cytarabine) often develops; therefore a new treatment modality is needed. Bcl-2 family proteins play an important role in balancing cell survival and apoptosis. The antiapoptotic Bcl-2 family proteins have been found to be dysregulated in AML. ABT-199, a BH3 mimetic, was developed to target antiapoptotic protein Bcl-2. Although ABT-199 has demonstrated promising results, resistance occurs. Previous studies in AML show that ABT-199 alone decreases the association of proapoptotic protein Bim with Bcl-2, but this is compensated by increased association of Bim with prosurvival protein Mcl-1, stabilizing Mcl-1, resulting in resistance to ABT-199. In this study, we investigated the antileukemic activity of the Mcl-1-selective inhibitor A-1210477 in combination with ABT-199 in AML cells. We found that A-1210477 synergistically induced apoptosis with ABT-199 in AML cell lines and primary patient samples. The synergistic induction of apoptosis was decreased upon Bak, Bax and Bim knockdown. While A-1210477 treatment alone also increased Mcl-1 protein levels, combination with ABT-199 reduced binding of Bim to Mcl-1. Our results demonstrate that sequestration of Bim by Mcl-1, a mechanism of ABT-199 resistance, can be abrogated by combined treatment with the Mcl-1 inhibitor A-1201477. 10.1038/sigtrans.2017.12
    Targeting Apoptosis in Acute Myeloid Leukemia: Current Status and Future Directions of BCL-2 Inhibition with Venetoclax and Beyond. Choi Jun H,Bogenberger James M,Tibes Raoul Targeted oncology Acute myeloid leukemia (AML) is a disease of the hematopoietic system that remains a therapeutic challenge despite advances in our understanding of the underlying cancer biology over the past decade. Recent developments in molecular targeting have shown promising results in treating leukemia, paving the way for novel treatment strategies. The discovery of drugs that promote apoptosis in leukemic cells has translated to encouraging activity in clinical trials. B-cell lymphoma (BCL)-2 inhibition has been at the center of drug development efforts to target apoptosis in AML. Remarkable clinical success with venetoclax has revolutionized the ways we treat hematological malignancies. Several landmark trials have demonstrated the potent antitumor activity of venetoclax, and it is now frequently combined with traditional cytotoxic agents to treat AML. However, resistance to BCL-2 inhibition is emerging, and alternative strategies to address resistance mechanisms have become an important focus of research. A number of clinical trials are now underway to investigate a plurality of novel agents that were shown to overcome resistance to BCL-2 inhibition in preclinical models. Some of the most promising data come from studies on drugs that downregulate myeloid cell leukemia (MCL)-1, such as cyclin-dependent kinases (CDK) inhibitors. Furthermore, innovative approaches to target apoptosis via extrinsic pathways and p53 regulation have added new cytotoxic agents to the arsenal, including drugs that inhibit inhibitor of apoptosis protein (IAP) family proteins and murine double minute 2 (MDM2). This review provides a perspective on past and current treatment strategies harnessing various mechanisms of apoptosis to target AML and highlights some important promising treatment combinations in development. 10.1007/s11523-020-00711-3
    Shutting Down Acute Myeloid Leukemia and Myelodysplastic Syndrome with BCL-2 Family Protein Inhibition. Sharma Prashant,Pollyea Daniel A Current hematologic malignancy reports PURPOSE OF REVIEW:Apoptosis results from the interaction between pro- and anti-apoptotic proteins, mediated by BCL-2 homology 3 (BH3) proteins. B cell lymphoma-2 (BCL-2) is an inhibitor of apoptosis which stabilizes the mitochondria, resulting in the prevention of activation of the pro-apoptotic proteins. In addition, BCL-2 is overexpressed in the leukemic stem cell (LSC) population, and its inhibition may lead to selective LSC eradication. Herein, we will discuss the mechanism and rationale of BCL-2 inhibition in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) with an overview of the selective BCL-2 inhibitor venetoclax. RECENT FINDINGS:Venetoclax has activity against AML and has displayed synergistic activity with hypomethylating agents in the preclinical setting. In the clinical setting, although it has only modest activity as a single agent in relapsed and refractory AML, in the older, treatment-naïve population, in combination with either a hypomethylator or low-dose cytarabine, it is well tolerated with impressive efficacy. In addition, BCL-2 inhibition may also have activity in MDS, and although clinical trials are in their early phases, this may be an effective strategy in both the up-front and relapsed setting. BCL-2 inhibition with venetoclax is well tolerated and active in older patients with newly diagnosed AML and in the relapsed setting has activity that may be improved in combination with other therapies. It may prove to be effective in MDS and is an exciting treatment strategy for myeloid malignancies. 10.1007/s11899-018-0464-8
    A concise review of BCL-2 inhibition in acute myeloid leukemia. Yogarajah Meera,Stone Richard M Expert review of hematology INTRODUCTION:Acute myeloid leukemia (AML) is a heterogeneous disease characterized by clonal proliferation of myeloid precursors with impaired ability to differentiate to mature cells causing accumulation of leukemic blasts in bone marrow, peripheral blood, and extramedullary tissue. Our understanding of the genomic landscape of AML has improved prognostic accuracy and lead to the development of targeted therapies. In 2017 the Food and Drug Administration (FDA) approved midostaurin, gemtuzumab ozogamicin, CPX-351 and enasidenib for the treatment of AML. There are many novel agents under investigation for treatment of AML, but those that inhibit the anti-apoptotic molecule BCL-2 are of particular interest due to strong pre-clinical data and early promising clinical results. Areas covered: This article provides an overview of the pathophysiology of BCL-2 inhibition in AML, biomarkers and resistance mechanisms to BCL-2 inhibition and an update of results of the preclinical and clinical trials. Expert commentary: Venetoclax-based combination treatment for newly diagnosed elderly patients for whom intense chemotherapy is not an option may be the first setting in which this agent may be employed in AML. Based on pre-clinical evidence, BCL-2 inhibition may be useful in relapsed/refractory disease in conjunction with cytotoxic therapy, but has modest single agent activity. 10.1080/17474086.2018.1420474
    The TP53 Apoptotic Network Is a Primary Mediator of Resistance to BCL2 Inhibition in AML Cells. Nechiporuk Tamilla,Kurtz Stephen E,Nikolova Olga,Liu Tingting,Jones Courtney L,D'Alessandro Angelo,Culp-Hill Rachel,d'Almeida Amanda,Joshi Sunil K,Rosenberg Mara,Tognon Cristina E,Danilov Alexey V,Druker Brian J,Chang Bill H,McWeeney Shannon K,Tyner Jeffrey W Cancer discovery To study mechanisms underlying resistance to the BCL2 inhibitor venetoclax in acute myeloid leukemia (AML), we used a genome-wide CRISPR/Cas9 screen to identify gene knockouts resulting in drug resistance. We validated , , and as genes whose inactivation results in venetoclax resistance in AML cell lines. Resistance to venetoclax resulted from an inability to execute apoptosis driven by BAX loss, decreased expression of BCL2, and/or reliance on alternative BCL2 family members such as BCL2L1. The resistance was accompanied by changes in mitochondrial homeostasis and cellular metabolism. Evaluation of knockout cells for sensitivities to a panel of small-molecule inhibitors revealed a gain of sensitivity to TRK inhibitors. We relate these observations to patient drug responses and gene expression in the Beat AML dataset. Our results implicate , the apoptotic network, and mitochondrial functionality as drivers of venetoclax response in AML and suggest strategies to overcome resistance. SIGNIFICANCE: AML is challenging to treat due to its heterogeneity, and single-agent therapies have universally failed, prompting a need for innovative drug combinations. We used a genetic approach to identify genes whose inactivation contributes to drug resistance as a means of forming preferred drug combinations to improve AML treatment... 10.1158/2159-8290.CD-19-0125
    BH3 mimetic ABT-737 induces apoptosis in CD34 acute myeloid leukemia cells and shows synergistic effect with conventional chemotherapeutic drugs. Rao Jia,Li Fei,Zhang Rong-Yan,Zhou Huan-Huan,Chen Guo-An Asia-Pacific journal of clinical oncology AIMS:Acute myeloid leukemia (AML) is an immunophenotypically heterogenous malignant disease. The early immature CD34 AML cell subpopulation is frequently impervious to intensive chemotherapy, making them largely responsible for relapse of AML. CD34 AML cells have higher level of Bcl-2 protein expression than the CD34 subpopulation. As such, development of drugs that specifically target the Bcl-2 may have the potential to eliminate immature CD34 AML progenitor cells and provide therapeutic benefit. In this work, we made an attempt to investigate the cytotoxic effect of a novel Bcl-2 family inhibitor, ABT-737, on CD34 AML cell lines (KG1a and Kasumi-1) as well as CD34 primary AML cells. METHODS:Primary human CD34 cells were isolated from bone marrow mononuclear cells using CD34 MicroBead kit. The growth inhibitory effect was measured by cell counting kit-8. Apoptosis was analyzed by annexin V/PI assays. Protein expression was determined by Western blotting analysis. RESULTS:Inhibition of Bcl-2 by ABT-737 effectively inhibited growth and induced apoptosis in CD34 AML cell lines and CD34 primary AML cells without affecting CD34 normal hematopoietic cells. Furthermore, Western blot analysis showed that ABT-737 induced apoptosis associated with caspase-3 activation and poly ADP-ribose polymerase (PARP) degradation. Finally, ABT-737 synergistically enhanced the cytotoxic effect of cytarabine and daunorubicin in CD34 AML cells. CONCLUSION:Taken together, these findings indicate that ABT-737 may offer as a promising molecular targeting agent in CD34 AML. 10.1111/ajco.12420
    Synthetic Lethality of Combined Bcl-2 Inhibition and p53 Activation in AML: Mechanisms and Superior Antileukemic Efficacy. Pan Rongqing,Ruvolo Vivian,Mu Hong,Leverson Joel D,Nichols Gwen,Reed John C,Konopleva Marina,Andreeff Michael Cancer cell Evasion of apoptosis is a hallmark of cancer. Bcl-2 and p53 represent two important nodes in apoptosis signaling pathways. We find that concomitant p53 activation and Bcl-2 inhibition overcome apoptosis resistance and markedly prolong survival in three mouse models of resistant acute myeloid leukemia (AML). Mechanistically, p53 activation negatively regulates the Ras/Raf/MEK/ERK pathway and activates GSK3 to modulate Mcl-1 phosphorylation and promote its degradation, thus overcoming AML resistance to Bcl-2 inhibition. Moreover, Bcl-2 inhibition reciprocally overcomes apoptosis resistance to p53 activation by switching cellular response from G arrest to apoptosis. The efficacy, together with the mechanistic findings, reveals the potential of simultaneously targeting these two apoptosis regulators and provides a rational basis for clinical testing of this therapeutic approach. 10.1016/j.ccell.2017.11.003