Chronic myeloid leukemia (CML) is a heterogeneous disease, initiated by reciprocal translocation ... more Chronic myeloid leukemia (CML) is a heterogeneous disease, initiated by reciprocal translocation of chromosome 9 and 22, resulting in the generation of a BCR-ABL fusion protein and constitutive activation of the ABL kinase. ABL tyrosine kinase inhibitors (TKIs) have been very successful in suppressing CML disease. However, TKIs may not eliminate leukemia stem cells (LSCs), as evidenced by the frequent re-emergence of the disease upon TKI discontinuation. Moreover, blast phase CML (bpCML) remains a formidable challenge in disease management. Recent clinical evidence suggests that the BCL2 inhibitor venetoclax (Ven) in combination with ABL-targeting tyrosine kinase inhibitors (TKI) can eradicate bpCML LSCs. However, the exact mechanism by which this combination may targets LSCs is not known. In this report, we confirm the efficacy and LSC-targeting capacity of Ven/TKI combination in preclinical models of bpCML and we further identify that inhibition of free fatty acid (FFA) mobilizati...
First-generation, large-scale functional genomic screens have revealed hundreds of potential gene... more First-generation, large-scale functional genomic screens have revealed hundreds of potential genetic vulnerabilities in acute myeloid leukemia (AML), a devastating hematologic malignancy with poor overall survival. Because these large-scale genetic screens were primarily performed in vitro in established AML cell lines, their translational relevance has been debated. Therefore, we established a protocol for CRISPR screening in orthotopic xenograft models of human AML, including patient-derived-xenograft (PDX) models that are tractable for CRISPR-editing. We first defined experimental conditions necessary for an optimal in vivo screen via barcoding experiments. We determined that sub-lethal irradiation was necessary for improved barcode representation in bone marrow and to reduce mouse-to-mouse variation. Moreover, it was critical to combine samples from multiple mice to achieve complete in vivo library representation. Next, using the Broad DepMap and other publicly available functio...
Highlights d The E3 ligase TRIM8 is an exquisitely selective dependency in Ewing sarcoma d TRIM8 ... more Highlights d The E3 ligase TRIM8 is an exquisitely selective dependency in Ewing sarcoma d TRIM8 regulates EWS/FLI expression but not its wild-type counterparts d K334 is critical for TRIM8-mediated degradation of EWS/FLI d Increased EWS/FLI levels induce cell death in Ewing sarcoma cells
The core cohesin subunit STAG2 is recurrently mutated in Ewing sarcoma but its biological role is... more The core cohesin subunit STAG2 is recurrently mutated in Ewing sarcoma but its biological role is less clear. Here, we demonstrate that cohesin complexes containing STAG2 occupy enhancer and polycomb repressive complex (PRC2)-marked regulatory regions. Genetic suppression of STAG2 leads to a compensatory increase in cohesin-STAG1 complexes, but not in enhancer-rich regions, and results in reprogramming of cis-chromatin interactions. Strikingly, in STAG2 knockout cells the oncogenic genetic program driven by the fusion transcription factor EWS/FLI1 was highly perturbed, in part due to altered enhancer-promoter contacts. Moreover, loss of STAG2 also disrupted PRC2-mediated regulation of gene expression. Combined, these transcriptional changes converged to modulate EWS/FLI1, migratory, and neurodevelopmental programs. Finally, consistent with clinical observations, functional studies revealed that loss of STAG2 enhances the metastatic potential of Ewing sarcoma xenografts. Our findings demonstrate that STAG2 mutations can alter chromatin architecture and transcriptional programs to promote an aggressive cancer phenotype.
CRISPR-Cas9-based genetic screens have successfully identified cell type-dependent liabilities in... more CRISPR-Cas9-based genetic screens have successfully identified cell type-dependent liabilities in cancers, including acute myeloid leukemia (AML), a devastating hematologic malignancy with poor overall survival. Because most of these screens have been performed in vitro, evaluating the physiological relevance of these targets is critical. We have established a CRISPR screening approach using orthotopic xenograft models to prioritize AML-enriched dependencies in vivo, complemented by the validation in CRISPR-competent AML patient-derived xenograft (PDX) models tractable for genome editing. Our integrated pipeline has revealed several targets with translational value, including SLC5A3 as a metabolic vulnerability for AML addicted to exogenous myo-inositol and MARCH5 as a critical guardian to prevent apoptosis in AML. MARCH5 repression enhanced the efficacy of BCL2 inhibitors such as venetoclax, highlighting the clinical potential of targeting MARCH5 in AML. Our study provides a valuab...
Venetoclax-based therapy can induce responses in approximately 70% of older previously untreated ... more Venetoclax-based therapy can induce responses in approximately 70% of older previously untreated patients with acute myeloid leukemia (AML). However, up-front resistance as well as relapse following initial response demonstrates the need for a deeper understanding of resistance mechanisms. In the present study, we report that responses to venetoclax +azacitidine in patients with AML correlate closely with developmental stage, where phenotypically primitive AML is sensitive, but monocytic AML is more resistant. Mechanistically, resistant monocytic AML has a distinct transcriptomic profile, loses expression of venetoclax target BCL2, and relies on MCL1 to mediate oxidative phosphorylation and survival. This differential sensitivity drives a selective process in patients which favors the outgrowth of monocytic subpopulations at relapse. Based on these findings, we conclude that resistance to venetoclax + azacitidine can arise due to biological properties intrinsic to monocytic differen...
Recent clinical trials have reported that in combination with hypomethylating agents, the BCL-2 i... more Recent clinical trials have reported that in combination with hypomethylating agents, the BCL-2 inhibitor venetoclax can induce responses in over 70% of older previously untreated AML patients who are unfit for conventional chemotherapy. These findings led to the recent United States Food and Drug Administration approval of this regimen for this population, and it is now considered to be the standard care. However, a significant minority of patients do not achieve a remission and are refractory. In addition, the majority of patients who do achieve a remission ultimately relapse. It is therefore critical to identify AML patients who are likely to be resistant to venetoclax-based therapy. To initially address this question, we retrospectively reviewed 75 newly diagnosed AML patients who received venetoclax + azacitidine (VEN+AZA) at our institution and analyzed several baseline clinical features to determine the ability of each to predict disease that was refractory to treatment (defi...
Rheumatoid arthritis (RA) is a debilitating autoimmune disease resulting from autoantibodies that... more Rheumatoid arthritis (RA) is a debilitating autoimmune disease resulting from autoantibodies that cause damage to synovial joints. Joint damage causes increased systemic inflammatory cytokines which may lead to aberrant hematopoiesis. Indeed, RA is accompanied by many hematological complications including anemia, cytopenias, and suppressed bone marrow function. Hematopoietic stem cells (HSC) at root of the blood system can respond to inflammatory signals by activating the cell cycle and preferentially generating myeloid cells. However, chronic inflammation can also lead to HSC dysfunction. Previous studies using genetic mouse models of RA have identified myeloid overproduction in this context; however, HSC long-term reconstitution activity was maintained. To better understand hematopoietic alterations in RA, our group used the collagen induced arthritis (CIA) mouse model, which is inducible in adult mice and recapitulates many immunological features of the human disease, including e...
Adipose tissue (AT) serves as a storage site for lipids as well as an endocrine organ. In the con... more Adipose tissue (AT) serves as a storage site for lipids as well as an endocrine organ. In the context of cancer, AT can function to facilitate the progression of tumors. Interestingly, recent studies have shown that AT acts as an extramedullary reservoir of hematopoietic stem cells (HSCs), suggesting the presence of a HSC niche in AT. The fact that leukemia stem cells (LSCs) co-opt the HSC marrow and the supportive effect of AT on cancer cells led us to hypothesize that AT functions as a reservoir for LSCs. To test this hypothesis, we first examined whether there were LSCs residing in AT. Using a murine model of primary blast crisis CML, we found enrichment of phenotypically primitive leukemia cells (PLCs) in the gonadal adipose tissue (GAT) relative to bone marrow, spleen and peripheral blood (Figure 1). The high percentage of PLCs in GAT led us to postulate that PLCs are preferentially reliant on fatty acids as an energy source since GAT was found to be lipolytic in leukemic mice....
Studies from normal cell biology have demonstrated that mitochondria can switch between fission-a... more Studies from normal cell biology have demonstrated that mitochondria can switch between fission-active and fusion-active states to dramatically change their morphology during important developmental events such as lineage differentiation and cell division. Further, very recent research has revealed intriguing interactions between mitochondrial morphology regulation and oncogenic signals in cancer. To date however, whether mitochondrial morphology regulation plays a role in cancer stem cell function remains largely unknown. We report, in acute myelogenous leukemia (AML), leukemia stem cells (LSCs), characterized by a low level of reactive oxygen species (ROS), have hyper-active mitochondrial fission regulators as evidenced by higher levels of mitochondrial fission 1 (FIS1) and activating phosphorylation of dynamin-related protein 1 (DRP1), compared to non-LSCs. To directly compare the mitochondrial morphology in LSCs versus non-LSCs, we imaged mitochondrial morphology using transmiss...
We recently reported that adipose tissue functions as a reservoir for leukemia stem cells (LSCs) ... more We recently reported that adipose tissue functions as a reservoir for leukemia stem cells (LSCs) using a murine model of leukemia (Ye et al., Cell Stem Cell, 2016). Intriguingly, the presence of leukemic cells in adipose tissue induces increased lipolysis and the release of free fatty acids (FFA) which in turn fuels the growth of LSCs. Further, adipose tissue protects resident LSCs from chemotherapy. These findings indicate that the unique characteristics of adipose tissue may provide key insights on the growth and survival of leukemic cells. Thus, in the present study we focus on the endocrine function of adipose tissue and explore its role in leukemia development. First, to evaluate secreted factors, we applied adipokine arrays which detect 38 adipokines to leukemia serum collected at different stages of leukemia pathogenesis. Interestingly, we observed a significantly elevated level of serum IGFBP1 as soon as leukemic disease became evident at low levels (~0.5%) in marrow. IGFBP1...
Mitochondrial dynamics describes the ability of mitochondria to switch between fission and fusion... more Mitochondrial dynamics describes the ability of mitochondria to switch between fission and fusion-active states to change morphology. Although it has long been thought that mitochondrial dynamics is downstream of various growth/differentiation signals and metabolic cues, recent studies have shown that mitochondrial morphology can also actively regulate cellular metabolism and the cell fate of normal stem cells including hematopoietic stem cells. In the present studies, we examined the role of mitochondrial dynamics in the biology of human leukemia stem cells (LSCs). We observe that LSCs are highly sensitive to the perturbation of mitochondrial morphology and that defined signal transduction pathways are involved in this process. We therefore propose that maintenance of the LSC state is critically linked to mitochondrial dynamics. Our data show that LSC enriched populations derived from primary human acute myeloid leukemia (AML) specimens have hyper-active mitochondrial fission regul...
Aberrant function of adipose tissue (AT) is seen in several diseases including cancer. Studies sh... more Aberrant function of adipose tissue (AT) is seen in several diseases including cancer. Studies show that AT facilitates the progression of tumors through paracrine signaling of adipokines as well as regulation of cancer cell metabolism. However, the mechanism by which cancer cells corrupt the normal function of AT to gain proliferative and survival advantages is unknown. Using a murine model of blast crisis CML, we have shown enrichment of phenotypically primitive leukemia cells (Sca+/lin- leukemia cells, termed…
Acute myeloid leukemia (AML) is a hematological malignancy characterized by the accumulation of i... more Acute myeloid leukemia (AML) is a hematological malignancy characterized by the accumulation of immature myeloid precursor cells. AML is poorly responsive to conventional genotoxic chemotherapy and a diagnosis of AML is usually fatal. More effective and less toxic forms of therapy are desperately needed. AML cells are known to be highly dependent on the amino acid glutamine for their survival. Here, we show that blocking glutamine metabolism through the use of a glutaminase inhibitor (CB-839) significantly impairs antioxidant glutathione production in multiple types of AML, resulting in accretion of mitochondrial reactive oxygen species (mitoROS) and apoptotic cell death. Moreover, glutaminase inhibition makes AML cells susceptible to adjuvant drugs that further perturb mitochondrial redox state, such as arsenic trioxide (ATO) and homoharringtonine (HHT). Indeed, the combination of ATO or HHT with CB-839 exacerbates mitoROS and apoptosis, and leads to more complete cell death in AML...
In this study we interrogated the metabolome of human acute myeloid leukemia (AML) stem cells to ... more In this study we interrogated the metabolome of human acute myeloid leukemia (AML) stem cells to elucidate properties relevant to therapeutic intervention. We demonstrate that amino acid uptake, steady-state levels, and catabolism are all elevated in the leukemia stem cell (LSC) population. Furthermore, LSCs isolated from de novo AML patients are uniquely reliant on amino acid metabolism for oxidative phosphorylation and survival. Pharmacological inhibition of amino acid metabolism reduces oxidative phosphorylation and induces cell death. In contrast, LSCs obtained from relapsed AML patients are not reliant on amino acid metabolism due to their ability to compensate through increased fatty acid metabolism. These findings indicate that clinically relevant eradication of LSCs can be achieved with drugs that target LSC metabolic vulnerabilities.
From an organismal perspective, cancer cell populations can be considered analogous to parasites ... more From an organismal perspective, cancer cell populations can be considered analogous to parasites that compete with the host for essential systemic resources such as glucose. Here, we employed leukemia models and human leukemia samples to document a form of adaptive homeostasis, where malignant cells alter systemic physiology through impairment of both host insulin sensitivity and insulin secretion to provide tumors with increased glucose. Mechanistically, tumor cells induce high-level production of IGFBP1 from adipose tissue to mediate insulin sensitivity. Further, leukemia-induced gut dysbiosis, serotonin loss, and incretin inactivation combine to suppress insulin secretion. Importantly, attenuated disease progression and prolonged survival are achieved through disruption of the leukemia-induced adaptive homeostasis. Our studies provide a paradigm for systemic management of leukemic disease.
Leukemia stem cells (LSCs) are thought to drive the genesis of acute myeloid leukemia (AML) as we... more Leukemia stem cells (LSCs) are thought to drive the genesis of acute myeloid leukemia (AML) as well as relapse following chemotherapy. Because of their unique biology, developing effective methods to eradicate LSCs has been a significant challenge. In the present study, we demonstrate that intrinsic overexpression of the mitochondrial dynamics regulator FIS1 mediates mitophagy activity that is essential for primitive AML cells. Depletion of FIS1 attenuates mitophagy and leads to inactivation of GSK3, myeloid differentiation, cell cycle arrest, and a profound loss of LSC self-renewal potential. Further, we report that the central metabolic stress regulator AMPK is also intrinsically activated in LSC populations and is upstream of FIS1. Inhibition of AMPK signaling recapitulates the biological effect of FIS1 loss. These data suggest a model in which LSCs co-opt AMPK/FIS1-mediated mitophagy as a means to maintain stem cell properties that may be otherwise compromised by the stresses in...
Chronic myeloid leukemia (CML) is a heterogeneous disease, initiated by reciprocal translocation ... more Chronic myeloid leukemia (CML) is a heterogeneous disease, initiated by reciprocal translocation of chromosome 9 and 22, resulting in the generation of a BCR-ABL fusion protein and constitutive activation of the ABL kinase. ABL tyrosine kinase inhibitors (TKIs) have been very successful in suppressing CML disease. However, TKIs may not eliminate leukemia stem cells (LSCs), as evidenced by the frequent re-emergence of the disease upon TKI discontinuation. Moreover, blast phase CML (bpCML) remains a formidable challenge in disease management. Recent clinical evidence suggests that the BCL2 inhibitor venetoclax (Ven) in combination with ABL-targeting tyrosine kinase inhibitors (TKI) can eradicate bpCML LSCs. However, the exact mechanism by which this combination may targets LSCs is not known. In this report, we confirm the efficacy and LSC-targeting capacity of Ven/TKI combination in preclinical models of bpCML and we further identify that inhibition of free fatty acid (FFA) mobilizati...
First-generation, large-scale functional genomic screens have revealed hundreds of potential gene... more First-generation, large-scale functional genomic screens have revealed hundreds of potential genetic vulnerabilities in acute myeloid leukemia (AML), a devastating hematologic malignancy with poor overall survival. Because these large-scale genetic screens were primarily performed in vitro in established AML cell lines, their translational relevance has been debated. Therefore, we established a protocol for CRISPR screening in orthotopic xenograft models of human AML, including patient-derived-xenograft (PDX) models that are tractable for CRISPR-editing. We first defined experimental conditions necessary for an optimal in vivo screen via barcoding experiments. We determined that sub-lethal irradiation was necessary for improved barcode representation in bone marrow and to reduce mouse-to-mouse variation. Moreover, it was critical to combine samples from multiple mice to achieve complete in vivo library representation. Next, using the Broad DepMap and other publicly available functio...
Highlights d The E3 ligase TRIM8 is an exquisitely selective dependency in Ewing sarcoma d TRIM8 ... more Highlights d The E3 ligase TRIM8 is an exquisitely selective dependency in Ewing sarcoma d TRIM8 regulates EWS/FLI expression but not its wild-type counterparts d K334 is critical for TRIM8-mediated degradation of EWS/FLI d Increased EWS/FLI levels induce cell death in Ewing sarcoma cells
The core cohesin subunit STAG2 is recurrently mutated in Ewing sarcoma but its biological role is... more The core cohesin subunit STAG2 is recurrently mutated in Ewing sarcoma but its biological role is less clear. Here, we demonstrate that cohesin complexes containing STAG2 occupy enhancer and polycomb repressive complex (PRC2)-marked regulatory regions. Genetic suppression of STAG2 leads to a compensatory increase in cohesin-STAG1 complexes, but not in enhancer-rich regions, and results in reprogramming of cis-chromatin interactions. Strikingly, in STAG2 knockout cells the oncogenic genetic program driven by the fusion transcription factor EWS/FLI1 was highly perturbed, in part due to altered enhancer-promoter contacts. Moreover, loss of STAG2 also disrupted PRC2-mediated regulation of gene expression. Combined, these transcriptional changes converged to modulate EWS/FLI1, migratory, and neurodevelopmental programs. Finally, consistent with clinical observations, functional studies revealed that loss of STAG2 enhances the metastatic potential of Ewing sarcoma xenografts. Our findings demonstrate that STAG2 mutations can alter chromatin architecture and transcriptional programs to promote an aggressive cancer phenotype.
CRISPR-Cas9-based genetic screens have successfully identified cell type-dependent liabilities in... more CRISPR-Cas9-based genetic screens have successfully identified cell type-dependent liabilities in cancers, including acute myeloid leukemia (AML), a devastating hematologic malignancy with poor overall survival. Because most of these screens have been performed in vitro, evaluating the physiological relevance of these targets is critical. We have established a CRISPR screening approach using orthotopic xenograft models to prioritize AML-enriched dependencies in vivo, complemented by the validation in CRISPR-competent AML patient-derived xenograft (PDX) models tractable for genome editing. Our integrated pipeline has revealed several targets with translational value, including SLC5A3 as a metabolic vulnerability for AML addicted to exogenous myo-inositol and MARCH5 as a critical guardian to prevent apoptosis in AML. MARCH5 repression enhanced the efficacy of BCL2 inhibitors such as venetoclax, highlighting the clinical potential of targeting MARCH5 in AML. Our study provides a valuab...
Venetoclax-based therapy can induce responses in approximately 70% of older previously untreated ... more Venetoclax-based therapy can induce responses in approximately 70% of older previously untreated patients with acute myeloid leukemia (AML). However, up-front resistance as well as relapse following initial response demonstrates the need for a deeper understanding of resistance mechanisms. In the present study, we report that responses to venetoclax +azacitidine in patients with AML correlate closely with developmental stage, where phenotypically primitive AML is sensitive, but monocytic AML is more resistant. Mechanistically, resistant monocytic AML has a distinct transcriptomic profile, loses expression of venetoclax target BCL2, and relies on MCL1 to mediate oxidative phosphorylation and survival. This differential sensitivity drives a selective process in patients which favors the outgrowth of monocytic subpopulations at relapse. Based on these findings, we conclude that resistance to venetoclax + azacitidine can arise due to biological properties intrinsic to monocytic differen...
Recent clinical trials have reported that in combination with hypomethylating agents, the BCL-2 i... more Recent clinical trials have reported that in combination with hypomethylating agents, the BCL-2 inhibitor venetoclax can induce responses in over 70% of older previously untreated AML patients who are unfit for conventional chemotherapy. These findings led to the recent United States Food and Drug Administration approval of this regimen for this population, and it is now considered to be the standard care. However, a significant minority of patients do not achieve a remission and are refractory. In addition, the majority of patients who do achieve a remission ultimately relapse. It is therefore critical to identify AML patients who are likely to be resistant to venetoclax-based therapy. To initially address this question, we retrospectively reviewed 75 newly diagnosed AML patients who received venetoclax + azacitidine (VEN+AZA) at our institution and analyzed several baseline clinical features to determine the ability of each to predict disease that was refractory to treatment (defi...
Rheumatoid arthritis (RA) is a debilitating autoimmune disease resulting from autoantibodies that... more Rheumatoid arthritis (RA) is a debilitating autoimmune disease resulting from autoantibodies that cause damage to synovial joints. Joint damage causes increased systemic inflammatory cytokines which may lead to aberrant hematopoiesis. Indeed, RA is accompanied by many hematological complications including anemia, cytopenias, and suppressed bone marrow function. Hematopoietic stem cells (HSC) at root of the blood system can respond to inflammatory signals by activating the cell cycle and preferentially generating myeloid cells. However, chronic inflammation can also lead to HSC dysfunction. Previous studies using genetic mouse models of RA have identified myeloid overproduction in this context; however, HSC long-term reconstitution activity was maintained. To better understand hematopoietic alterations in RA, our group used the collagen induced arthritis (CIA) mouse model, which is inducible in adult mice and recapitulates many immunological features of the human disease, including e...
Adipose tissue (AT) serves as a storage site for lipids as well as an endocrine organ. In the con... more Adipose tissue (AT) serves as a storage site for lipids as well as an endocrine organ. In the context of cancer, AT can function to facilitate the progression of tumors. Interestingly, recent studies have shown that AT acts as an extramedullary reservoir of hematopoietic stem cells (HSCs), suggesting the presence of a HSC niche in AT. The fact that leukemia stem cells (LSCs) co-opt the HSC marrow and the supportive effect of AT on cancer cells led us to hypothesize that AT functions as a reservoir for LSCs. To test this hypothesis, we first examined whether there were LSCs residing in AT. Using a murine model of primary blast crisis CML, we found enrichment of phenotypically primitive leukemia cells (PLCs) in the gonadal adipose tissue (GAT) relative to bone marrow, spleen and peripheral blood (Figure 1). The high percentage of PLCs in GAT led us to postulate that PLCs are preferentially reliant on fatty acids as an energy source since GAT was found to be lipolytic in leukemic mice....
Studies from normal cell biology have demonstrated that mitochondria can switch between fission-a... more Studies from normal cell biology have demonstrated that mitochondria can switch between fission-active and fusion-active states to dramatically change their morphology during important developmental events such as lineage differentiation and cell division. Further, very recent research has revealed intriguing interactions between mitochondrial morphology regulation and oncogenic signals in cancer. To date however, whether mitochondrial morphology regulation plays a role in cancer stem cell function remains largely unknown. We report, in acute myelogenous leukemia (AML), leukemia stem cells (LSCs), characterized by a low level of reactive oxygen species (ROS), have hyper-active mitochondrial fission regulators as evidenced by higher levels of mitochondrial fission 1 (FIS1) and activating phosphorylation of dynamin-related protein 1 (DRP1), compared to non-LSCs. To directly compare the mitochondrial morphology in LSCs versus non-LSCs, we imaged mitochondrial morphology using transmiss...
We recently reported that adipose tissue functions as a reservoir for leukemia stem cells (LSCs) ... more We recently reported that adipose tissue functions as a reservoir for leukemia stem cells (LSCs) using a murine model of leukemia (Ye et al., Cell Stem Cell, 2016). Intriguingly, the presence of leukemic cells in adipose tissue induces increased lipolysis and the release of free fatty acids (FFA) which in turn fuels the growth of LSCs. Further, adipose tissue protects resident LSCs from chemotherapy. These findings indicate that the unique characteristics of adipose tissue may provide key insights on the growth and survival of leukemic cells. Thus, in the present study we focus on the endocrine function of adipose tissue and explore its role in leukemia development. First, to evaluate secreted factors, we applied adipokine arrays which detect 38 adipokines to leukemia serum collected at different stages of leukemia pathogenesis. Interestingly, we observed a significantly elevated level of serum IGFBP1 as soon as leukemic disease became evident at low levels (~0.5%) in marrow. IGFBP1...
Mitochondrial dynamics describes the ability of mitochondria to switch between fission and fusion... more Mitochondrial dynamics describes the ability of mitochondria to switch between fission and fusion-active states to change morphology. Although it has long been thought that mitochondrial dynamics is downstream of various growth/differentiation signals and metabolic cues, recent studies have shown that mitochondrial morphology can also actively regulate cellular metabolism and the cell fate of normal stem cells including hematopoietic stem cells. In the present studies, we examined the role of mitochondrial dynamics in the biology of human leukemia stem cells (LSCs). We observe that LSCs are highly sensitive to the perturbation of mitochondrial morphology and that defined signal transduction pathways are involved in this process. We therefore propose that maintenance of the LSC state is critically linked to mitochondrial dynamics. Our data show that LSC enriched populations derived from primary human acute myeloid leukemia (AML) specimens have hyper-active mitochondrial fission regul...
Aberrant function of adipose tissue (AT) is seen in several diseases including cancer. Studies sh... more Aberrant function of adipose tissue (AT) is seen in several diseases including cancer. Studies show that AT facilitates the progression of tumors through paracrine signaling of adipokines as well as regulation of cancer cell metabolism. However, the mechanism by which cancer cells corrupt the normal function of AT to gain proliferative and survival advantages is unknown. Using a murine model of blast crisis CML, we have shown enrichment of phenotypically primitive leukemia cells (Sca+/lin- leukemia cells, termed…
Acute myeloid leukemia (AML) is a hematological malignancy characterized by the accumulation of i... more Acute myeloid leukemia (AML) is a hematological malignancy characterized by the accumulation of immature myeloid precursor cells. AML is poorly responsive to conventional genotoxic chemotherapy and a diagnosis of AML is usually fatal. More effective and less toxic forms of therapy are desperately needed. AML cells are known to be highly dependent on the amino acid glutamine for their survival. Here, we show that blocking glutamine metabolism through the use of a glutaminase inhibitor (CB-839) significantly impairs antioxidant glutathione production in multiple types of AML, resulting in accretion of mitochondrial reactive oxygen species (mitoROS) and apoptotic cell death. Moreover, glutaminase inhibition makes AML cells susceptible to adjuvant drugs that further perturb mitochondrial redox state, such as arsenic trioxide (ATO) and homoharringtonine (HHT). Indeed, the combination of ATO or HHT with CB-839 exacerbates mitoROS and apoptosis, and leads to more complete cell death in AML...
In this study we interrogated the metabolome of human acute myeloid leukemia (AML) stem cells to ... more In this study we interrogated the metabolome of human acute myeloid leukemia (AML) stem cells to elucidate properties relevant to therapeutic intervention. We demonstrate that amino acid uptake, steady-state levels, and catabolism are all elevated in the leukemia stem cell (LSC) population. Furthermore, LSCs isolated from de novo AML patients are uniquely reliant on amino acid metabolism for oxidative phosphorylation and survival. Pharmacological inhibition of amino acid metabolism reduces oxidative phosphorylation and induces cell death. In contrast, LSCs obtained from relapsed AML patients are not reliant on amino acid metabolism due to their ability to compensate through increased fatty acid metabolism. These findings indicate that clinically relevant eradication of LSCs can be achieved with drugs that target LSC metabolic vulnerabilities.
From an organismal perspective, cancer cell populations can be considered analogous to parasites ... more From an organismal perspective, cancer cell populations can be considered analogous to parasites that compete with the host for essential systemic resources such as glucose. Here, we employed leukemia models and human leukemia samples to document a form of adaptive homeostasis, where malignant cells alter systemic physiology through impairment of both host insulin sensitivity and insulin secretion to provide tumors with increased glucose. Mechanistically, tumor cells induce high-level production of IGFBP1 from adipose tissue to mediate insulin sensitivity. Further, leukemia-induced gut dysbiosis, serotonin loss, and incretin inactivation combine to suppress insulin secretion. Importantly, attenuated disease progression and prolonged survival are achieved through disruption of the leukemia-induced adaptive homeostasis. Our studies provide a paradigm for systemic management of leukemic disease.
Leukemia stem cells (LSCs) are thought to drive the genesis of acute myeloid leukemia (AML) as we... more Leukemia stem cells (LSCs) are thought to drive the genesis of acute myeloid leukemia (AML) as well as relapse following chemotherapy. Because of their unique biology, developing effective methods to eradicate LSCs has been a significant challenge. In the present study, we demonstrate that intrinsic overexpression of the mitochondrial dynamics regulator FIS1 mediates mitophagy activity that is essential for primitive AML cells. Depletion of FIS1 attenuates mitophagy and leads to inactivation of GSK3, myeloid differentiation, cell cycle arrest, and a profound loss of LSC self-renewal potential. Further, we report that the central metabolic stress regulator AMPK is also intrinsically activated in LSC populations and is upstream of FIS1. Inhibition of AMPK signaling recapitulates the biological effect of FIS1 loss. These data suggest a model in which LSCs co-opt AMPK/FIS1-mediated mitophagy as a means to maintain stem cell properties that may be otherwise compromised by the stresses in...
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