Lactate Utilization Enables Metabolic Escape to Confer Resistance to BET Inhibition in Acute Myeloid Leukemia.

Impairing the BET family coactivator BRD4 with small-molecule inhibitors (BETi) showed encouraging preclinical activity in treating acute myeloid leukemia (AML). However, dose-limiting toxicities and limited clinical activity dampened the enthusiasm for BETi as a single agent. BETi resistance in AML myeloblasts was found to correlate with maintaining mitochondrial respiration, suggesting that identifying the metabolic pathway sustaining mitochondrial integrity could help develop approaches to improve BETi efficacy. Herein, we demonstrated that mitochondria-associated lactate dehydrogenase allows AML myeloblasts to utilize lactate as a metabolic bypass to fuel mitochondrial respiration and maintain cellular viability. Pharmacologically and genetically impairing lactate utilization rendered resistant myeloblasts susceptible to BET inhibition. Low-dose combinations of BETi and oxamate, a lactate dehydrogenase inhibitor, reduced in vivo expansion of BETi-resistant AML in cell line and patient-derived murine models. These results elucidate how AML myeloblasts metabolically adapt to BETi by consuming lactate and demonstrate that combining BETi with inhibitors of lactate utilization may be useful in AML treatment. SIGNIFICANCE: Lactate utilization allows AML myeloblasts to maintain metabolic integrity and circumvent antileukemic therapy, which supports testing of lactate utilization inhibitors in clinical settings to overcome BET inhibitor resistance in AML. See related commentary by Boët and Sarry, p. 950.

TLR3 agonism augments CD47 inhibition in acute myeloid leukemia.

CD47-SIRPa is a myeloid check point pathway that promotes phagocytosis of cells lacking markers for self-recognition. Tumor cells can overexpress CD47 and bind to SIRPa on macrophages, preventing phagocytosis. CD47 expression is enhanced and correlated with a negative prognosis in acute myeloid leukemia (AML), with its blockade leading to cell clearance. ALX90 is an engineered fusion protein with high affinity for CD47. Composed of the N-terminal D1 domain of SIRPα genetically linked to an inactive Fc domain from human immunoglobulin (Ig) G, ALX90 is designed to avoid potential toxicity of CD47-expressing red blood cells. Venetoclax (VEN) is a specific B-cell lymphoma-2 (BCL-2) inhibitor that can restore apoptosis in malignant cells. In AML, VEN is combined with azanucleosides to induce superior remission rates, however treatment for refractory/relapse is an unmet need. We questioned whether the anti-tumor activity of a VENbased regimen can be augmented through CD47 inhibition (CD47i) in AML and how this triplet may be enhanced. Human AML cell lines were sensitive to ALX90 and its addition increased efficacy of a VEN plus azacitidin (VEN+AZA) regimen in vivo. However, CD47i failed to clear bone marrow tumor burden in PDX models. We hypothesized that the loss of resident macrophages in the bone marrow in AML reduced efficiency of CD47i. Therefore, we attempted to enhance this medullary macrophage population with agonism of TLR3 via polyinosinic:polycytidylic acid (poly(I:C)), which led to expansion and activation of medullary macrophages in in vivo AML PDX models and potentiated CD47i. In summary, the addition of poly(I:C) can enhance medullary macrophage populations to potentiate the phagocytosis merited by therapeutic inhibition of CD47.

Selective inhibition of MCL1 overcomes venetoclax resistance in a murine model of myelodysplastic syndromes.

Treatment for myelodysplastic syndromes (MDS) remains insufficient due to clonal heterogeneity and lack of effective clinical therapies. Dysregulation of apoptosis is observed across MDS subtypes regardless of mutations and represents an attractive therapeutic opportunity. Venetoclax (VEN), a selective inhibitor of anti-apoptotic protein B-cell lymphoma- 2 (BCL2), has yielded impressive responses in older patients with acute myeloid leukemia (AML) and high risk MDS. BCL2 family anti-apoptotic proteins BCL-XL and induced myeloid cell leukemia 1 (MCL1) are implicated in leukemia survival, and upregulation of MCL1 is seen in VEN-resistant AML and MDS. We determined in vitro sensitivity of MDS patient samples to selective inhibitors of BCL2, BCL-XL and MCL1. While VEN response positively correlated with MDS with excess blasts, all MDS subtypes responded to MCL1 inhibition. Treatment with combined VEN + MCL1 inhibtion was synergistic in all MDS subtypes without significant injury to normal hematopoiesis and reduced MDS engraftment in MISTRG6 mice, supporting the pursuit of clinical trials with combined BCL2 + MCL1 inhibition in MDS.

Pevonedistat and azacitidine upregulate NOXA (PMAIP1) to increase sensitivity to venetoclax in preclinical models of acute myeloid leukemia.

Dysregulation of apoptotic machinery is one mechanism by which acute myeloid leukemia (AML) acquires a clonal survival advantage. B-cell lymphoma protein-2 (BCL2) overexpression is a common feature in hematologic malignancies. The selective BCL2 inhibitor, venetoclax (VEN) is used in combination with azacitidine (AZA), a DNAmethyltransferase inhibitor (DNMTi), to treat patients with AML. Despite promising response rates to VEN/AZA, resistance to the agent is common. One identified mechanism of resistance is the upregulation of myeloid cell leukemia-1 protein (MCL1). Pevonedistat (PEV), a novel agent that inhibits NEDD8-activating enzyme, and AZA both upregulate NOXA (PMAIP1), a BCL2 family protein that competes with effector molecules at the BH3 binding site of MCL1. We demonstrate that PEV/AZA combination induces NOXA to a greater degree than either PEV or AZA alone, which enhances VEN-mediated apoptosis. Herein, using AML cell lines and primary AML patient samples ex vivo, including in cells with genetic alterations linked to treatment resistance, we demonstrate robust activity of the PEV/VEN/AZA triplet. These findings were corroborated in preclinical systemic engrafted models of AML. Collectively, these results provide rational for combining PEV/VEN/AZA as a novel therapeutic approach in overcoming AML resistance in current therapies.

BET Inhibition Enhances the Antileukemic Activity of Low-dose Venetoclax in Acute Myeloid Leukemia.

PURPOSE: The BCL2 inhibitor, venetoclax, has transformed clinical care in acute myeloid leukemia (AML). However, subsets of patients do not respond or eventually acquire resistance. Venetoclax-based regimens can lead to considerable marrow suppression in some patients. Bromodomain and extraterminal inhibitors (BETi) are potential treatments for AML, as regulators of critical AML oncogenes. We tested the efficacy of novel BET inhibitor INCB054329, and its synergy with venetoclax to reduce AML without induction of hematopoietic toxicity. EXPERIMENTAL DESIGN: INCB054329 efficacy was assessed by changes in cell cycle and apoptosis in treated AML cell lines. In vivo efficacy was assessed by tumor reduction in MV-4-11 cell line-derived xenografts. Precision run-on and sequencing (PRO-seq) evaluated effects of INCB054329. Synergy between low-dose BETi and venetoclax was assessed in cell lines and patient samples in vitro and in vivo while efficacy and toxicity was assessed in patient-derived xenograft (PDX) models. RESULTS: INCB054329 induced dose-dependent apoptosis and quiescence in AML cell lines. PRO-seq analysis evaluated the effects of INCB054329 on transcription and confirmed reduced transcriptional elongation of key oncogenes, MYC and BCL2, and genes involved in the cell cycle and metabolism. Combinations of BETi and venetoclax led to reduced cell viability in cell lines and patient samples. Low-dose combinations of INCB054329 and venetoclax in cell line and PDX models reduced AML burden, regardless of the sensitivity to monotherapy without development of toxicity. CONCLUSIONS: Our findings suggest low dose combinations of venetoclax and BETi may be more efficacious for patients with AML than either monotherapy, potentially providing a longer, more tolerable dosing regimen.

Nascent transcript and single-cell RNA-seq analysis defines the mechanism of action of the LSD1 inhibitor INCB059872 in myeloid leukemia.

Drugs targeting chromatin-modifying enzymes have entered clinical trials for myeloid malignancies, including INCB059872, a selective irreversible inhibitor of Lysine-Specific Demethylase 1 (LSD1). While initial studies of LSD1 inhibitors suggested these compounds may be used to induce differentiation of acute myeloid leukemia (AML), the mechanisms underlying this effect and dose-limiting toxicities are not well understood. Here, we used precision nuclear run-on sequencing (PRO-seq) and ChIP-seq in AML cell lines to probe for the earliest regulatory events associated with INCB059872 treatment. The changes in nascent transcription could be traced back to a loss of CoREST activity and activation of GFI1-regulated genes. INCB059872 is in phase I clinical trials, and we evaluated a pre-treatment bone marrow sample of a patient who showed a clinical response to INCB059872 while being treated with azacitidine. We used single-cell RNA-sequencing (scRNA-seq) to show that INCB059872 caused a shift in gene expression that was again associated with GFI1/GFI1B regulation. Finally, we treated mice with INCB059872 and performed scRNA-seq of lineage-negative bone marrow cells, which showed that INCB059872 triggered accumulation of megakaryocyte early progenitor cells with gene expression hallmarks of stem cells. Accumulation of these stem/progenitor cells may contribute to the thrombocytopenia observed in patients treated with LSD1 inhibitors.

Oral Azacitidine and Cedazuridine Approximate Parenteral Azacitidine Efficacy in Murine Model.

BACKGROUND: DNA methyltransferase inhibitors (DNMTis) improve survival for patients with myelodysplastic syndromes (MDS) and those with acute myeloid leukemia (AML) unable to receive standard cytotoxic chemotherapy and are, accordingly, the backbone of standard-of-care treatment for these conditions. Standard regimens with DNMTIs, decitabine (DEC) or azacitidine (AZA) include daily subcutaneous (s.c.) or intravenous (i.v.) administration for 5-7 consecutive days. Attempts to provide the therapy orally have been limited given rapid clearance of the agents by the enzyme cytidine deaminase (CDA), which is ubiquitous in the gut and liver as part of first-pass metabolism. Recently, cedazuridine (CDZ), an oral inhibitor of CDA, was successfully combined with DEC to approximate the pharmacokinetics of i.v. DEC in patients. OBJECTIVE: To determine if an oral dosing strategy might be feasible in the clinic with AZA, we attempted to increase the bioavailability of oral AZA through the use of CDZ, in a murine model. METHODS: Following pharmacokinetic and pharmacodynamic assessment of oral AZA dosed with CDZ in murine and monkey models, we tested this regimen in vivo with a human cell line-derived xenograft transplantation experiment (CDX). Following this we combined the regimen with venetoclax (VEN) to test the efficacy of an all-oral regimen in a patient-derived xenograft (PDX) model. RESULTS: Parenteral AZA and oral AZA + CDZ exhibited similar pharmacokinetic profiles, and efficacy against human AML cells. Tumor regression was seen with AZA + CDZ in MOLM-13 CDX and PDX models. CONCLUSIONS: We conclude that oral AZA when combined with CDZ achieves successful tumor regression in both CDX and PDX models. Furthermore, the combination of AZA + CDZ with VEN in a PDX model emulated responses seen with VEN + AZA in the clinic, implying a potential all-oral VEN-based therapy opportunity in myeloid diseases.

Venetoclax response is enhanced by selective inhibitor of nuclear export compounds in hematologic malignancies.

The selective inhibitor of nuclear export (SINE) compounds selinexor (KPT-330) and eltanexor (KPT-8602) are from a novel class of small molecules that target exportin-1 (XPO1 [CRM1]), an essential nucleo-cytoplasmic transport protein responsible for the nuclear export of major tumor suppressor proteins and growth regulators such as p53, p21, and p27. XPO1 also affects the translation of messenger RNAs for critical oncogenes, including MYC, BCL2, MCL1, and BCL6, by blocking the export of the translation initiation factor eIF4E. Early trials with venetoclax (ABT-199), a potent, selective inhibitor of BCL2, have revealed responses across a variety of hematologic malignancies. However, many tumors are not responsive to venetoclax. We used models of acute myeloid leukemia (AML) and diffuse large B-cell lymphoma (DLBCL) to determine in vitro and in vivo responses to treatment with venetoclax and SINE compounds combined. Cotreatment with venetoclax and SINE compounds demonstrated loss of viability in multiple cell lines. Further in vitro analyses showed that this enhanced cell death was the result of an increase in apoptosis that led to a loss of clonogenicity in methylcellulose assays, coinciding with activation of p53 and loss of MCL1. Treatment with SINE compounds and venetoclax combined led to a reduction in tumor growth in both AML and DLBCL xenografts. Immunohistochemical analysis of tissue sections revealed that the reduction in tumor cells was partly the result of an induction of apoptosis. The enhanced effects of this combination were validated in primary AML and DLBCL patient cells. Our studies reveal synergy with SINE compounds and venetoclax in aggressive hematologic malignancies and provide a rationale for pursuing this approach in a clinical trial.

A Novel MCL1 Inhibitor Combined with Venetoclax Rescues Venetoclax-Resistant Acute Myelogenous Leukemia.

Suppression of apoptosis by expression of antiapoptotic BCL2 family members is a hallmark of acute myeloblastic leukemia (AML). Induced myeloid leukemia cell differentiation protein (MCL1), an antiapoptotic BCL2 family member, is commonly upregulated in AML cells and is often a primary mode of resistance to treatment with the BCL2 inhibitor venetoclax. Here, we describe VU661013, a novel, potent, selective MCL1 inhibitor that destabilizes BIM/MCL1 association, leads to apoptosis in AML, and is active in venetoclax-resistant cells and patient-derived xenografts. In addition, VU661013 was safely combined with venetoclax for synergy in murine models of AML. Importantly, BH3 profiling of patient samples and drug-sensitivity testing ex vivo accurately predicted cellular responses to selective inhibitors of MCL1 or BCL2 and showed benefit of the combination. Taken together, these data suggest a strategy of rationally using BCL2 and MCL1 inhibitors in sequence or in combination in AML clinical trials. SIGNIFICANCE: Targeting antiapoptotic proteins in AML is a key therapeutic strategy, and MCL1 is a critical antiapoptotic oncoprotein. Armed with novel MCL1 inhibitors and the potent BCL2 inhibitor venetoclax, it may be possible to selectively induce apoptosis by combining or thoughtfully sequencing these inhibitors based on a rational evaluation of AML.See related commentary by Leber et al., p. 1511.This article is highlighted in the In This Issue feature, p. 1494.

MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer.

MicroRNA (miR) are important regulators of gene expression, and aberrant miR expression has been linked to oncogenesis; however, little is understood about their contribution to lung tumorigenesis. Here, we determined that miR-31 is overexpressed in human lung adenocarcinoma and this overexpression independently correlates with decreased patient survival. We developed a transgenic mouse model that allows for lung-specific expression of miR-31 to test the oncogenic potential of miR-31 in the lung. Using this model, we observed that miR-31 induction results in lung hyperplasia, followed by adenoma formation and later adenocarcinoma development. Moreover, induced expression of miR-31 in mice cooperated with mutant KRAS to accelerate lung tumorigenesis. We determined that miR-31 regulates lung epithelial cell growth and identified 6 negative regulators of RAS/MAPK signaling as direct targets of miR-31. Our study distinguishes miR-31 as a driver of lung tumorigenesis that promotes mutant KRAS-mediated oncogenesis and reveals that miR-31 directly targets and reduces expression of negative regulators of RAS/MAPK signaling.

Oncogenic protein MTBP interacts with MYC to promote tumorigenesis.

Despite its involvement in most human cancers, MYC continues to pose a challenge as a readily tractable therapeutic target. Here we identify the MYC transcriptional cofactors TIP48 and TIP49 and MYC as novel binding partners of Mdm2-binding protein (MTBP), a functionally undefined protein that we show is oncogenic and overexpressed in many human cancers. MTBP associated with MYC at promoters and increased MYC-mediated transcription, proliferation, neoplastic transformation, and tumor development. In breast cancer specimens, we determined overexpression of both MYC and MTBP was associated with a reduction in 10-year patient survival compared with MYC overexpression alone. MTBP was also frequently co-amplified with MYC in many human cancers. Mechanistic investigations implicated associations with TIP48/TIP49 as well as MYC in MTBP function in cellular transformation and the growth of human breast cancer cells. Taken together, our findings show MTBP functions with MYC to promote malignancy, identifying this protein as a novel general therapeutic target in human cancer.

Psychometrical assessment and item analysis of the General Health Questionnaire in victims of terrorism.

There is a need to assess the psychiatric morbidity that appears as a consequence of terrorist attacks. The General Health Questionnaire (GHQ) has been used to this end, but its psychometric properties have never been evaluated in a population affected by terrorism. A sample of 891 participants included 162 direct victims of terrorist attacks and 729 relatives of the victims. All participants were evaluated using the 28-item version of the GHQ (GHQ-28). We examined the reliability and external validity of scores on the scale using Cronbach's alpha and Pearson correlation with the State-Trait Anxiety Inventory (STAI), respectively. The factor structure of the scale was analyzed with varimax rotation. Samejima's (1969) graded response model was used to explore the item properties. The GHQ-28 scores showed good reliability and item-scale correlations. The factor analysis identified 3 factors: anxious-somatic symptoms, social dysfunction, and depression symptoms. All factors showed good correlation with the STAI. Before rotation, the first, second, and third factor explained 44.0%, 6.4%, and 5.0% of the variance, respectively. Varimax rotation redistributed the percentages of variance accounted for to 28.4%, 13.8%, and 13.2%, respectively. Items with the highest loadings in the first factor measured anxiety symptoms, whereas items with the highest loadings in the third factor measured suicide ideation. Samejima's model found that high scores in suicide-related items were associated with severe depression. The factor structure of the GHQ-28 found in this study underscores the preeminence of anxiety symptoms among victims of terrorism and their relatives. Item response analysis identified the most difficult and significant items for each factor.

MicroRNA biogenesis is required for Myc-induced B-cell lymphoma development and survival.

Many tumor cells express globally reduced levels of microRNAs (miRNA), suggesting that decreased miRNA expression in premalignant cells contributes to their tumorigenic phenotype. In support of this, Dicer, an RNase III-like enzyme that controls the maturation of miRNA, was recently shown to function as a haploinsufficient tumor suppressor in nonhematopoietic cells. Because the Myc oncoprotein, a critical inducer of B-cell lymphomas, was reported to suppress the expression of multiple miRNAs in lymphoma cells, it was presumed that a deficiency of Dicer and subsequent loss of miRNA maturation would accelerate Myc-induced lymphoma development. We report here that, surprisingly, a haploinsufficiency of Dicer in B cells failed to promote B-cell malignancy or accelerate Myc-induced B-cell lymphomagenesis in mice. Moreover, deletion of Dicer in B cells of CD19-cre(+)/Emicro-myc mice significantly inhibited lymphomagenesis, and all lymphomas that did arise in these mice lacked functional Cre expression and retained at least one functional Dicer allele. Uncharacteristically, the lymphomas that frequently developed in the CD19-cre(+)/Dicer(fl/fl)/Emicro-myc mice were of very early precursor B-cell origin, a stage of B-cell development prior to Cre expression. Therefore, loss of Dicer function was not advantageous for lymphomagenesis, but rather, Dicer ablation was strongly selected against during Myc-induced B-cell lymphoma development. Moreover, deletion of Dicer in established B-cell lymphomas resulted in apoptosis, revealing that Dicer is required for B-cell lymphoma survival. Thus, Dicer does not function as a haploinsufficient tumor suppressor in B cells and is required for B-cell lymphoma development and survival.

Cutting edge: K63-linked polyubiquitination of NEMO modulates TLR signaling and inflammation in vivo.

Transcription factor NF-kappaB controls the expression of multiple genes involved in immunity and inflammation. The initial activation and duration of NF-kappaB signaling is regulated by posttranslational modifications to IkappaB kinase, which earmarks inhibitors of NF-kappaB for degradation. Prior studies suggest that K63-linked ubiquitination of NEMO (NF-kappaB essential modulator), an IkappaB kinase regulatory subunit, is critical for NF-kappaB and MAPK signaling following engagement of Ag receptors. We now demonstrate that NF-kappaB and MAPK pathways are largely unaffected in primary cells from mice harboring a ubiquitination-defective form of NEMO, NEMO-KR. TLR- but not Ag receptor-induced cellular responses are impaired in NEMO-KR mice, which are more resistant to LPS-induced endotoxic shock than wild-type animals. Thus, one function of NEMO ubiquitination is to fine tune innate immune responses under TLR control.

[Mental disorders in victims of terrorism and their families]. / Trastornos mentales en las víctimas de atentados terroristas y sus familiares.

BACKGROUND AND OBJECTIVE: To find out whether victims of terrorism and their relatives have higher prevalence of affective, anxiety, and alcohol abuse disorders than the general population. MATERIAL AND METHOD: Between January 1997 and January 2001, 544 families affected by terrorist violence in Spain were interviewed. Victims and their relatives (n = 1,021) were evaluated by means of the PRIME-MD. They were classified according to the degree of involvement in the attacks as: relatives of victims (RV), direct victims (DV) and direct victims who were also relatives of other victims (DVRV). Their scores were compared with those of a primary health-care sample. RESULTS: Depressive symptoms were more prevalent among victims (DVRV, 59.2%; DV, 57.6%; RV, 50.2%) than among controls (40.0%) (p = 0.036) and their prevalence was directly related to the degree of involvement in the attacks. Similar results were obtained for anxiety disorders (DVRV, 52.6%; DV, 56.5%; RV, 45.0%, and controls 26.4%) (p = 0.017). Alcohol abuse prevalence (DVRV, 6.6%; RV, 5.9%) was very close to that of the primary health-care sample (4.8%) with the exception of direct victims (DV, 15.9%) in whom it was higher (p = 0.016). CONCLUSIONS: The prevalence of psychopathology was higher among victims of terrorism than among primary health-care patients and it was directly related to the involvement in the attack. Low perceived social support, family and personal history of psychiatric disease, and type of attack (explosives) increased the risk of suffering mental disorders.