IDH1 mutations are common in low-grade gliomas and secondary glioblastomas and cause overproduction of (R)-2HG. (R)-2HG modulates the activity of many enzymes, including some that are linked to ...transformation and some that are probably bystanders. Although prior work on (R)-2HG targets focused on 2OG-dependent dioxygenases, we found that (R)-2HG potently inhibits the 2OG-dependent transaminases BCAT1 and BCAT2, likely as a bystander effect, thereby decreasing glutamate levels and increasing dependence on glutaminase for the biosynthesis of glutamate and one of its products, glutathione. Inhibiting glutaminase specifically sensitized IDH mutant glioma cells to oxidative stress in vitro and to radiation in vitro and in vivo. These findings highlight the complementary roles for BCATs and glutaminase in glutamate biosynthesis, explain the sensitivity of IDH mutant cells to glutaminase inhibitors, and suggest a strategy for maximizing the effectiveness of such inhibitors against IDH mutant gliomas.
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•(R)-2-hydroxyglutarate, produced by IDH1/2 mutants, inhibits the BCAT transaminases•IDH mutant gliomas display a transamination-dependent glutamate biosynthesis defect•BCAT loss increases reliance on glutaminase for glutamate and glutathione synthesis•Mutant IDH and glutaminase inhibition are synthetic lethal under oxidative stress
Gliomas with IDH mutations show increased sensitivity to radiation in concert with glutaminase inhibition, offering a new approach to treating these tumors.
The clinical success of the BCL-2-selective BH3-mimetic venetoclax in patients with poor prognosis chronic lymphocytic leukemia (CLL) highlights the potential of targeting the BCL-2-regulated ...apoptotic pathway in previously untreatable lymphoid malignancies. By selectively inhibiting BCL-2, venetoclax circumvents the dose-limiting, BCL-XL-mediated thrombocytopenia of its less selective predecessor navitoclax, while enhancing efficacy in CLL. We have previously reported the potent sensitivity of many high-risk childhood acute lymphoblastic leukemia (ALL) xenografts to navitoclax. Given the superior tolerability of venetoclax, here we have investigated its efficacy in childhood ALL. We demonstrate that in contrast to the clear dependence of CLL on BCL-2 alone, effective antileukemic activity in the majority of ALL xenografts requires concurrent inhibition of both BCL-2 and BCL-XL. We identify BCL-XL expression as a key predictor of poor response to venetoclax and demonstrate that concurrent inhibition of both BCL-2 and BCL-XL results in synergistic killing in the majority of ALL xenografts. A notable exception is mixed lineage leukemia–rearranged infant ALL, where venetoclax largely recapitulates the activity of navitoclax, identifying this subgroup of patients as potential candidates for clinical trials of venetoclax in childhood ALL. Conversely, our findings provide a clear basis for progressing navitoclax into trials ahead of venetoclax in other subgroups.
•Venetoclax demonstrates potent in vitro and in vivo single-agent activity in MLL-rearranged ALL xenografts.•Clinically efficacious BH3-mimetic therapy for other high-risk ALL subtypes is likely to require concurrent BCL-2 and BCL-XL inhibition.
Unhealthy alcohol use (UAU) is a leading cause of morbidity and mortality in the United States, contributing to 95,000 deaths annually. When offered in primary care, screening, brief intervention, ...referral to treatment (SBIRT), and medication-assisted treatment for alcohol use disorder (MAUD) can effectively address UAU. However, these interventions are not yet routine in primary care clinics. Therefore, our study evaluates tailored implementation support to increase SBIRT and MAUD in primary care. ANTECEDENT is a pragmatic implementation study designed to support 150 primary care clinics in Oregon adopting and optimizing SBIRT and MAUD workflows to address UAU. The study is a partnership between the Oregon Health Authority Transformation Center-state leaders in Medicaid health system transformation-SBIRT Oregon and the Oregon Rural Practice-based Research Network. We recruited clinics providing primary care in Oregon and prioritized reaching clinics that were small to medium in size (<10 providers). All participating clinics receive foundational support (i.e., a baseline assessment, exit assessment, and access to the online SBIRT Oregon materials) and may opt to receive tailored implementation support delivered by a practice facilitator over 12 months. Tailored implementation support is designed to address identified needs and may include health information technology support, peer-to-peer learning, workflow mapping, or expert consultation via academic detailing. The study aims are to 1) engage, recruit, and conduct needs assessments with 150 primary care clinics and their regional Medicaid health plans called Coordinated Care Organizations within the state of Oregon, 2) implement and evaluate the impact of foundational and supplemental implementation support on clinic change in SBIRT and MAUD, and 3) describe how practice facilitators tailor implementation support based on context and personal expertise. Our convergent parallel mixed-methods analysis uses RE-AIM (reach, effectiveness, adoption, implementation, maintenance). It is informed by a hybrid of the i-PARIHS (integrated Promoting Action on Research Implementation in Health Services) and the Dynamic Sustainability Framework. This study will explore how primary care clinics implement SBIRT and MAUD in routine practice and how practice facilitators vary implementation support across diverse clinic settings. Findings will inform how to effectively align implementation support to context, advance our understanding of practice facilitator skill development over time, and ultimately improve detection and treatment of UAU across diverse primary care clinics.
FOXP3
regulatory T (Treg) cells are essential for maintaining immunological tolerance. Given their importance in immune-related diseases, cancer and obesity, there is increasing interest in targeting ...the Treg cell compartment therapeutically. New pharmacological inhibitors that specifically target the prosurvival protein MCL-1 may provide this opportunity, as Treg cells are particularly reliant upon this protein. However, there are two distinct isoforms of MCL-1; one located at the outer mitochondrial membrane (OMM) that is required to antagonize apoptosis, and another at the inner mitochondrial membrane (IMM) that is reported to maintain IMM structure and metabolism via ATP production during oxidative phosphorylation. We set out to elucidate the relative importance of these distinct biological functions of MCL-1 in Treg cells to assess whether MCL-1 inhibition might impact upon the metabolism of cells able to resist apoptosis. Conditional deletion of Mcl1 in FOXP3
Treg cells resulted in a lethal multiorgan autoimmunity due to the depletion of the Treg cell compartment. This striking phenotype was completely rescued by concomitant deletion of the apoptotic effector proteins BAK and BAX, indicating that apoptosis plays a pivotal role in the homeostasis of Treg cells. Notably, MCL-1-deficient Treg cells rescued from apoptosis displayed normal metabolic capacity. Moreover, pharmacological inhibition of MCL-1 in Treg cells resistant to apoptosis did not perturb their metabolic function. We conclude that Treg cells require MCL-1 only to antagonize apoptosis and not for metabolism. Therefore, MCL-1 inhibition could be used to manipulate Treg cell survival for clinical benefit without affecting the metabolic fitness of cells resisting apoptosis.
Although the overall cure rate for pediatric acute lymphoblastic leukemia (ALL) approaches 90%, infants with ALL harboring translocations in the mixed-lineage leukemia (MLL) oncogene (infant MLL-ALL) ...experience shorter remission duration and lower survival rates (∼50%). Mutations in the p53 tumor-suppressor gene are uncommon in infant MLL-ALL, and drugs that release p53 from inhibitory mechanisms may be beneficial. The purpose of this study was to assess the efficacy of the orally available nutlin, RG7112, against patient-derived MLL-ALL xenografts.
Eight MLL-ALL patient-derived xenografts were established in immune-deficient mice, and their molecular features compared with B-lineage ALL and T-ALL xenografts. The sensitivity of MLL-ALL xenografts to RG7112 was assessed in vitro and in vivo, and the ability of RG7112 to induce p53, cell-cycle arrest, and apoptosis in vivo was evaluated.
Gene-expression analysis revealed that MLL-ALL, B-lineage ALL, and T-ALL xenografts clustered according to subtype. Moreover, genes previously reported to be overexpressed in MLL-ALL, including MEIS1, CCNA1, and members of the HOXA family, were significantly upregulated in MLL-ALL xenografts, confirming their ability to recapitulate the clinical disease. Exposure of MLL-ALL xenografts to RG7112 in vivo caused p53 upregulation, cell-cycle arrest, and apoptosis. RG7112 as a single agent induced significant regressions in infant MLL-ALL xenografts. Therapeutic enhancement was observed when RG7112 was assessed using combination treatment with an induction-type regimen (vincristine/dexamethasone/L-asparaginase) against an MLL-ALL xenograft.
The utility of targeting the p53-MDM2 axis in combination with established drugs for the management of infant MLL-ALL warrants further investigation.
Inactivation of the retinoblastoma gene (RB1) product, pRB, is common in many human cancers. Targeting downstream effectors of pRB that are central to tumorigenesis is a promising strategy to block ...the growth of tumors harboring loss-of-function RB1 mutations. One such effector is retinoblastoma-binding protein 2 (RBP2, also called JARID1A or KDM5A), which encodes an H3K4 demethylase. Binding of pRB to RBP2 has been linked to the ability of pRB to promote senescence and differentiation. Importantly, genetic ablation of RBP2 is sufficient to phenocopy pRB’s ability to induce these cellular changes in cell culture experiments. Moreover, germline Rbp2 deletion significantly impedes tumorigenesis in Rb1
+/− mice. The value of RBP2 as a therapeutic target in cancer, however, hinges on whether loss of RBP2 could block the growth of established tumors as opposed to simply delaying their onset. Here we show that conditional, systemic ablation of RBP2 in tumor-bearing Rb1
+/− mice is sufficient to slow tumor growth and significantly extend survival without causing obvious toxicity to the host. These findings show that established Rb1-null tumors require RBP2 for growth and further credential RBP2 as a therapeutic target in human cancers driven by RB1 inactivation.
Targeting the potent immunosuppressive properties of FOXP3
regulatory T cells (T
) has substantial therapeutic potential for treating autoimmune and inflammatory diseases. Yet, the molecular ...mechanisms controlling T
homeostasis, particularly during inflammation, remain unclear. We report that caspase-8 is a central regulator of T
homeostasis in a context-specific manner that is decisive during immune responses. In mouse genetic models, targeting caspase-8 in T
led to accumulation of effector T
resistant to apoptotic cell death. Conversely, inflammation induced the MLKL-dependent necroptosis of caspase-8-deficient lymphoid and tissue T
, which enhanced immunity to a variety of chronic infections to promote clearance of viral or parasitic pathogens. However, improved immunity came at the risk of lethal inflammation in overwhelming infections. Caspase-8 inhibition using a clinical-stage compound revealed that human T
have heightened sensitivity to necroptosis compared with conventional T cells. These findings reveal a fundamental mechanism in T
that could be targeted to manipulate the balance between immune tolerance versus response for therapeutic benefit.
Immunological tolerance is established and maintained by a diverse array of safeguards that work together to protect against autoimmunity. Despite the identification of numerous tolerogenic ...processes, the basis for cooperation among them remains poorly understood. We sought to identify synergy among several well-defined tolerance mediators that alone provide protection only from mild autoimmune symptoms in C57BL/6 mice: BIM, AIRE, CBL-B, and PD-1. Survey of a range of compound mutant mice revealed that the combined loss of the autoimmune regulator, AIRE, with PD-1 unleashed a spontaneous, lethal autoimmune disease. Pdcd1−/−Aire−/− mice succumbed to cachexia before adulthood, with near-complete destruction of the exocrine pancreas. Such fatal autoimmunity was not observed in Pdcd1−/−Bim−/−, Bim−/−Aire−/−, or Cblb−/−Bim−/− mice, suggesting that the cooperation between AIRE-mediated and PD-1–mediated tolerance was particularly potent. Immune profiling revealed largely normal development of FOXP3+ regulatory T (Treg) cells in Pdcd1−/−Aire−/− mice, yet excessive, early activation of effector T cells. Adoptive transfer experiments demonstrated that autoimmune exocrine pancreatitis was driven by conventional CD4+ T cells and could not be prevented by the cotransfer of Treg cells from wild-type mice. The development of autoimmunity in mixed bone marrow chimeras supported these observations, indicating that failure of recessive tolerance was responsible for disease. These findings reveal a potent tolerogenic axis between AIRE and PD-1 that has implications for our understanding of how immune checkpoint blockade might synergize with subclinical defects in central tolerance to elicit autoimmune disease.
Early T-cell precursor (ETP) acute lymphoblastic leukemia (ALL) is a recently described subtype of T-ALL characterized by a unique immunophenotype and genomic profile, as well as a high rate of ...induction failure. Frequent mutations in cytokine receptor and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathways led us to hypothesize that ETP-ALL is dependent on JAK/STAT signaling. Here we demonstrate aberrant activation of the JAK/STAT pathway in ETP-ALL blasts relative to non-ETP T-ALL. Moreover, ETP-ALL showed hyperactivation of STAT5 in response to interleukin-7, an effect that was abrogated by the JAK1/2 inhibitor ruxolitinib. In vivo, ruxolitinib displayed activity in 6 of 6 patient-derived murine xenograft models of ETP-ALL, with profound single-agent efficacy in 5 models. Ruxolitinib treatment decreased peripheral blast counts relative to pretreatment levels and compared with control (P < .01) in 5 of 6 ETP-ALL xenografts, with marked reduction in mean splenic blast counts (P < .01) in 6 of 6 samples. Surprisingly, both JAK/STAT pathway activation and ruxolitinib efficacy were independent of the presence of JAK/STAT pathway mutations, raising the possibility that the therapeutic potential of ruxolitinib in ETP-ALL extends beyond those cases with JAK mutations. These findings establish the preclinical in vivo efficacy of ruxolitinib in ETP-ALL, a biologically distinct subtype for which novel therapies are needed.
•ETP-ALL, a high-risk subtype of T-ALL, is characterized by aberrant activation of the JAK/STAT signaling pathway.•The JAK1/2 inhibitor ruxolitinib demonstrates robust activity in patient-derived xenograft models of ETP-ALL.
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