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Leukemia Cell of Origin Influences Apoptotic Priming and Sensitivity to LSD1 Inhibition.

ABSTRACT: The cell of origin of oncogenic transformation is a determinant of therapeutic sensitivity, but the mechanisms governing cell-of-origin-driven differences in therapeutic response have not been delineated. Leukemias initiating in hematopoietic stem cells (HSC) are less sensitive to chemotherapy and highly express the transcription factor MECOM (EVI1) compared with leukemias derived from myeloid progenitors. Here, we compared leukemias initiated in either HSCs or myeloid progenitors to reveal a novel function for EVI1 in modulating p53 protein abundance and activity. HSC-derived leukemias exhibit decreased apoptotic priming, attenuated p53 transcriptional output, and resistance to lysine-specific demethylase 1 (LSD1) inhibitors in addition to classical genotoxic stresses. p53 loss of function in Evi1 ^lo progenitor-derived leukemias induces resistance to LSD1 inhibition, and EVI1^hi leukemias are sensitized to LSD1 inhibition by venetoclax. Our findings demonstrate a role for EVI1 in p53 wild-type cancers in reducing p53 function and provide a strategy to circumvent drug resistance in chemoresistant EVI1 ^hi acute myeloid leukemia. SIGNIFICANCE: We demonstrate that the cell of origin of leukemia initiation influences p53 activity and dictates therapeutic sensitivity to pharmacologic LSD1 inhibitors via the transcription factor EVI1. We show that drug resistance could be overcome in HSC-derived leukemias by combining LSD1 inhibition with venetoclax.See related commentary by Gu et al., p. 1445.This article is highlighted in the In This Issue feature, p. 1426.

SUBMITTER: Cai SF

PROVIDER: S-EPMC7584353 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Leukemia cell of origin influences apoptotic priming and sensitivity to LSD1 inhibition

Project description:Previous studies have established that the cell of origin of oncogenic transformation is a determinant of therapeutic sensitivity. However, the mechanisms governing cell-of-origin-driven differences in therapeutic response have not been delineated. Leukemias initiating in hematopoietic stem cells (HSC) are less sensitive to cytotoxic chemotherapy and express high levels of the transcription factor Evi1 compared to leukemias derived from myeloid progenitors. Here, we compared drug sensitivity and expression profiles of murine and human leukemias initiated in either HSCs or myeloid progenitors to reveal a novel function for Evi1 in modulating p53 protein stability and activity. HSC-derived leukemias exhibit decreased apoptotic priming, attenuated p53 transcriptional output, and resistance to lysine-specific demethylase 1 inhibitors in addition to classical genotoxic stresses. p53 loss-of-function in Evi1low progenitor-derived leukemias induces resistance to LSD1 inhibition. By contrast, Evi1high leukemias are sensitized to LSD1 inhibition by the BH3 mimetic venetoclax, resulting in enhanced apoptosis and greater reductions in disease burden. Our findings demonstrate a cell-of-origin determined novel role for EVI1 in p53 wild-type cancers in reducing p53 function and provide a strategy to circumvent drug resistance in high-risk, chemoresistant EVI1high AML.

2020-07-29 | GSE153025 | GEO

Leukemia cell of origin influences apoptotic priming and sensitivity to LSD1 inhibition

Project description:Leukemia cell of origin influences apoptotic priming and sensitivity to LSD1 inhibition

| PRJNA641376 | ENA

Eradication of Central Nervous System Leukemia of T-Cell Origin with a Brain-Permeable LSD1 Inhibitor.

Project description:PurposeLysine-specific demethylase 1 (LSD1) regulates several biological processes via the bifunctional modulation of enhancer functions. Recently, we reported that LSD1 overexpression is a founder abnormality of T-cell leukemogenesis and is maintained in fully transformed T-cell acute lymphoblastic leukemia (T-ALL) cells. On the basis of this finding, we attempted to develop novel LSD1 inhibitors effective for T-ALL with central nervous system (CNS) involvement.Experimental designWe chemically modified the prototype LSD inhibitor tranylcypromine (TCP) and screened for cytotoxicity against TCP-resistant T-ALL cell lines. In vivo efficacy of novel LSD1 inhibitors was examined in immunodeficient mice transplanted with luciferase-expressing T-ALL cell lines, which faithfully reproduce human T-ALL with CNS involvement.ResultsWe found robust cytotoxicity against T-ALL cells, but not normal bone marrow progenitors, for two N-alkylated TCP derivatives, S2116 and S2157. The two compounds induced apoptosis in TCP-resistant T-ALL cells in vitro and in vivo by repressing transcription of the NOTCH3 and TAL1 genes through increased H3K9 methylation and reciprocal H3K27 deacetylation at superenhancer regions. Both S2116 and S2157 significantly retarded the growth of T-ALL cells in xenotransplanted mice and prolonged the survival of recipients as monotherapy and in combination with dexamethasone. Notably, S2157 could almost completely eradicate CNS leukemia because of its ability to efficiently pass through the blood-brain barrier.ConclusionsThese findings provide a molecular basis and rationale for the inclusion of a brain-permeable LSD1 inhibitor, S2157, in treatment strategies for T-ALL with CNS involvement.

| S-EPMC6397674 | biostudies-literature

Oncogenic ZEB2 activation drives sensitivity towards LSD1 inhibition in T-cell acute lymphoblastic leukemia

Project description:This SuperSeries is composed of the SubSeries listed below.

2017-02-03 | GSE83128 | GEO

Pharmacological inhibition of LSD1 for the treatment of MLL-rearranged leukemia.

Project description:BACKGROUND:Mixed lineage leukemia (MLL) gene translocations are found in ~75% infant and 10% adult acute leukemia, showing a poor prognosis. Lysine-specific demethylase 1 (LSD1) has recently been implicated to be a drug target for this subtype of leukemia. More studies using potent LSD1 inhibitors against MLL-rearranged leukemia are needed. METHODS:LSD1 inhibitors were examined for their biochemical and biological activities against LSD1 and MLL-rearranged leukemia as well as other cancer cells. RESULTS:Potent LSD1 inhibitors with biochemical IC50 values of 9.8-77 nM were found to strongly inhibit proliferation of MLL-rearranged leukemia cells with EC50 of 10-320 nM, while these compounds are generally non-cytotoxic to several other tumor cells. LSD1 inhibition increased histone H3 lysine 4 (H3K4) methylation, downregulated expression of several leukemia-relevant genes, induced apoptosis and differentiation, and inhibited self-renewal of stem-like leukemia cells. Moreover, LSD1 inhibitors worked synergistically with inhibition of DOT1L, a histone H3 lysine 79 (H3K79) methyltransferase, against MLL-rearranged leukemia. The most potent LSD1 inhibitor showed significant in vivo activity in a systemic mouse model of MLL-rearranged leukemia without overt toxicities. Mechanistically, LSD1 inhibitors caused significant upregulation of several pathways that promote hematopoietic differentiation and apoptosis. CONCLUSIONS:LSD1 is a drug target for MLL-rearranged leukemia, and LSD1 inhibitors are potential therapeutics for the malignancy.

| S-EPMC4789278 | biostudies-literature

PARP inhibition restores extrinsic apoptotic sensitivity in glioblastoma.

Project description:BackgroundResistance to apoptosis is a paramount issue in the treatment of Glioblastoma (GBM). We show that targeting PARP by the small molecule inhibitors, Olaparib (AZD-2281) or PJ34, reduces proliferation and lowers the apoptotic threshold of GBM cells in vitro and in vivo.MethodsThe sensitizing effects of PARP inhibition on TRAIL-mediated apoptosis and potential toxicity were analyzed using viability assays and flow cytometry in established GBM cell lines, low-passage neurospheres and astrocytes in vitro. Molecular analyses included western blots and gene silencing. In vivo, effects on tumor growth were examined in a murine subcutaneous xenograft model.ResultsThe combination treatment of PARP inhibitors and TRAIL led to an increased cell death with activation of caspases and inhibition of formation of neurospheres when compared to single-agent treatment. Mechanistically, pharmacological PARP inhibition elicited a nuclear stress response with up-regulation of down-stream DNA-stress response proteins, e.g., CCAAT enhancer binding protein (C/EBP) homology protein (CHOP). Furthermore, Olaparib and PJ34 increased protein levels of DR5 in a concentration and time-dependent manner. In turn, siRNA-mediated suppression of DR5 mitigated the effects of TRAIL/PARP inhibitor-mediated apoptosis. In addition, suppression of PARP-1 levels enhanced TRAIL-mediated apoptosis in malignant glioma cells. Treatment of human astrocytes with the combination of TRAIL/PARP inhibitors did not cause toxicity. Finally, the combination treatment of TRAIL and PJ34 significantly reduced tumor growth in vivo when compared to treatment with each agent alone.ConclusionsPARP inhibition represents a promising avenue to overcome apoptotic resistance in GBM.

| S-EPMC4273972 | biostudies-literature

Decreased mitochondrial apoptotic priming underlies stroma-mediated treatment resistance in chronic lymphocytic leukemia.

Project description:Stroma induces treatment resistance in chronic lymphocytic leukemia (CLL), possibly because of alterations in the BCL-2 family of proteins, which are key regulators of apoptosis. We previously developed BH3 profiling, a functional assay that assesses mitochondrial depolarization in response to BH3-only peptides, to measure "apoptotic priming," the proximity of a cell to the apoptotic threshold. In the present study, we use BH3 profiling to show that CLL cells from the PB are highly primed. Increased priming is associated with improved clinical response and, unexpectedly, with unmutated IGHV status. Coculturing CLL cells in vitro with stroma decreases priming. Using matched PB, BM, and lymph node compartment samples, we found in vivo that BM-derived CLL cells are the least primed. CLL cells cocultured with stroma were treated with the PI3K δ-isoform inhibitor CAL-101 (GS1101). CAL-101 caused CLL cell de-adhesion, leading to increased CLL cell priming. Stimulation of CLL cells with anti-IgM or CXCL12 caused decreased priming that could be reversed by CAL-101. Our results show that inhibition of stromal interactions leading to displacement of CLL cells into the blood by CAL-101 in vivo may increase CLL cell priming, suggesting a mechanism by which agents inducing lymphocyte redistribution might facilitate improved clinical response when used in combination with other therapies.

| S-EPMC3482860 | biostudies-literature

Reduced Mitochondrial Apoptotic Priming Drives Resistance to BH3 Mimetics in Acute Myeloid Leukemia.

Project description:Acquired resistance to BH3 mimetic antagonists of BCL-2 and MCL-1 is an important clinical problem. Using acute myelogenous leukemia (AML) patient-derived xenograft (PDX) models of acquired resistance to BCL-2 (venetoclax) and MCL-1 (S63845) antagonists, we identify common principles of resistance and persistent vulnerabilities to overcome resistance. BH3 mimetic resistance is characterized by decreased mitochondrial apoptotic priming as measured by BH3 profiling, both in PDX models and human clinical samples, due to alterations in BCL-2 family proteins that vary among cases, but not to acquired mutations in leukemia genes. BCL-2 inhibition drives sequestered pro-apoptotic proteins to MCL-1 and vice versa, explaining why in vivo combinations of BCL-2 and MCL-1 antagonists are more effective when concurrent rather than sequential. Finally, drug-induced mitochondrial priming measured by dynamic BH3 profiling (DBP) identifies drugs that are persistently active in BH3 mimetic-resistant myeloblasts, including FLT-3 inhibitors and SMAC mimetics.

| S-EPMC7988687 | biostudies-literature

LSD1 inhibition induces differentiation and cell death in Merkel cell carcinoma.

Project description:Merkel cell carcinoma (MCC) is a highly aggressive, neuroendocrine skin cancer that lacks actionable mutations, which could be utilized for targeted therapies. Epigenetic regulators governing cell identity may represent unexplored therapeutic entry points. Here, we targeted epigenetic regulators in a pharmacological screen and discovered that the lysine-specific histone demethylase 1A (LSD1/KDM1A) is required for MCC growth in vitro and in vivo. We show that LSD1 inhibition in MCC disrupts the LSD1-CoREST complex leading to displacement and degradation of HMG20B (BRAF35), a poorly characterized complex member that is essential for MCC proliferation. Inhibition of LSD1 causes derepression of transcriptional master regulators of the neuronal lineage, activates a gene expression signature resembling normal Merkel cells, and induces cell cycle arrest and cell death. Our study unveils the importance of LSD1 for maintaining cellular plasticity and proliferation in MCC. There is also growing evidence that cancer cells exploit cellular plasticity and dedifferentiation programs to evade destruction by the immune system. The combination of LSD1 inhibitors with checkpoint inhibitors may thus represent a promising treatment strategy for MCC patients.

| S-EPMC7645387 | biostudies-literature

LSD1 inhibition induces differentiation and cell death in Merkel cell carcinoma

Project description:Merkel cell carcinoma (MCC) is a highly aggressive, neuroendocrine skin cancer that lacks actionable mutations, which could be utilized for targeted therapies. Epigenetic regulators governing cell identity may represent unexplored therapeutic entry points. Here, we targeted epigenetic regulators in a pharmacological screen and discovered that the lysine-specific histone demethylase 1A (LSD1/KDM1A) is required for MCC growth in vitro and in vivo. We show that LSD1 inhibition in MCC disrupts the LSD1-CoREST complex leading to displacement and degradation of HMG20B (BRAF35), a poorly characterized complex member that is essential for MCC proliferation. Inhibition of LSD1 causes derepression of transcriptional master regulators of the neuronal lineage, activates a gene expression signature resembling normal Merkel cells, and induces cell cycle arrest and cell death. Our study unveils the importance of LSD1 for maintaining cellular plasticity and proliferation in MCC. There is growing evidence that cancer cells exploit cellular plasticity and dedifferentiation programs to evade destruction by the immune system. The combination of LSD1 inhibitors with checkpoint inhibitors may thus represent a promising treatment strategy for MCC patients.

| S-SCDT-EMM-2020-12525 | biostudies-other

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