Targeting MCL1-driven anti-apoptotic pathways overcomes blast progression after hypomethylating agent failure in chronic myelomonocytic leukemia.

RAS pathway mutations, which are present in 30% of patients with chronic myelomonocytic leukemia (CMML) at diagnosis, confer a high risk of resistance to and progression after hypomethylating agent (HMA) therapy, the current standard of care for the disease. Here, using single-cell, multi-omics technologies, we seek to dissect the biological mechanisms underlying the initiation and progression of RAS pathway-mutated CMML. We identify that RAS pathway mutations induce transcriptional reprogramming of hematopoietic stem and progenitor cells (HSPCs) and downstream monocytic populations in response to cell-intrinsic and -extrinsic inflammatory signaling that also impair the functions of immune cells. HSPCs expand at disease progression after therapy with HMA or the BCL2 inhibitor venetoclax and rely on the NF-κB pathway effector MCL1 to maintain survival. Our study has implications for the development of therapies to improve the survival of patients with RAS pathway-mutated CMML.

Hematopoietic stem cells with granulo-monocytic differentiation state overcome venetoclax sensitivity in patients with myelodysplastic syndromes.

The molecular mechanisms of venetoclax-based therapy failure in patients with acute myeloid leukemia were recently clarified, but the mechanisms by which patients with myelodysplastic syndromes (MDS) acquire secondary resistance to venetoclax after an initial response remain to be elucidated. Here, we show an expansion of MDS hematopoietic stem cells (HSCs) with a granulo-monocytic-biased transcriptional differentiation state in MDS patients who initially responded to venetoclax but eventually relapsed. While MDS HSCs in an undifferentiated cellular state are sensitive to venetoclax treatment, differentiation towards a granulo-monocytic-biased transcriptional state, through the acquisition or expansion of clones with STAG2 or RUNX1 mutations, affects HSCs' survival dependence from BCL2-mediated anti-apoptotic pathways to TNFα-induced pro-survival NF-κB signaling and drives resistance to venetoclax-mediated cytotoxicity. Our findings reveal how hematopoietic stem and progenitor cell (HSPC) can eventually overcome therapy-induced depletion and underscore the importance of using close molecular monitoring to prevent HSPC hierarchical change in MDS patients enrolled in clinical trials of venetoclax.

Targeting DNA2 overcomes metabolic reprogramming in multiple myeloma.

DNA damage resistance is a major barrier to effective DNA-damaging therapy in multiple myeloma (MM). To discover mechanisms through which MM cells overcome DNA damage, we investigate how MM cells become resistant to antisense oligonucleotide (ASO) therapy targeting Interleukin enhancer binding factor 2 (ILF2), a DNA damage regulator that is overexpressed in 70% of MM patients whose disease has progressed after standard therapies have failed. Here, we show that MM cells undergo adaptive metabolic rewiring to restore energy balance and promote survival in response to DNA damage activation. Using a CRISPR/Cas9 screening strategy, we identify the mitochondrial DNA repair protein DNA2, whose loss of function suppresses MM cells' ability to overcome ILF2 ASO-induced DNA damage, as being essential to counteracting oxidative DNA damage. Our study reveals a mechanism of vulnerability of MM cells that have an increased demand for mitochondrial metabolism upon DNA damage activation.

Cytogenetic and Molecular Associations with Outcomes in Higher-Risk Myelodysplastic Syndromes Treated with Hypomethylating Agents plus Venetoclax.

PURPOSE: Hypomethylating agents (HMA) combined with venetoclax are an emerging therapeutic strategy for higher-risk myelodysplastic syndromes (HR-MDS). The cytogenetic and molecular factors associated with outcomes with this combination for HR-MDS are incompletely understood. EXPERIMENTAL DESIGN: We pooled patient data from 3 prospective trials evaluating HMA-venetoclax in HR-MDS to study associations between cytogenetic and molecular factors and overall response rate (ORR), overall survival (OS), and event-free survival (EFS). The Kaplan-Meier method was used to estimate time-to-event endpoints. Univariate and multivariate analyses using logistic regression (for ORR) or the Cox proportional hazards model (for OS and EFS) were used to identify associations between clinical, cytogenetic, and molecular factors and outcomes. RESULTS: A total of 80 patients (52 HMA-naïve, 28 HMA-failure) were included. ORR was 90% in HMA-naïve and 57% in HMA-failure. Median OS was 28.2 and 8.3 months in HMA-naïve and HMA-failure, respectively. Median EFS was 17.9 and 5.5 months in HMA-naïve and HMA-failure, respectively. In addition, 24/52 (46%) of the HMA-naïve and 3/28 (11%) of the HMA-failure patients proceeded to allogeneic stem cell transplantation (SCT). Factors associated with inferior outcomes were prior HMA failure, complex cytogenetics, trisomy 8, TP53 mutations, and RAS pathway mutations. Mutations in RNA splicing, DNA methylation, and ASXL1 appeared favorable. Blast percentage was not predictive of outcomes. CONCLUSIONS: Knowledge of cytogenetic and molecular alterations may help identify which patients with HR-MDS benefit the most from venetoclax.

IL-1ß-mediated inflammatory signaling drives ineffective erythropoiesis in early-stage myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) are a group of incurable hematopoietic stem cell (HSC) neoplasms characterized by peripheral blood cytopenias and a high risk of progression to acute myeloid leukemia. MDS represent the final stage in a continuum of HSCs' genetic and functional alterations and are preceded by a premalignant phase, clonal cytopenia of undetermined significance (CCUS). Dissecting the mechanisms of CCUS maintenance may uncover therapeutic targets to delay or prevent malignant transformation. Here, we demonstrate that DNMT3A and TET2 mutations, the most frequent mutations in CCUS, induce aberrant HSCs' differentiation towards the myeloid lineage at the expense of erythropoiesis by upregulating IL-1ß-mediated inflammatory signaling and that canakinumab rescues red blood cell transfusion dependence in early-stage MDS patients with driver mutations in DNMT3A and TET2 . This study illuminates the biological landscape of CCUS and offers an unprecedented opportunity for MDS intervention during its initial phase, when expected survival is prolonged.

Targeting DNA2 Overcomes Metabolic Reprogramming in Multiple Myeloma.

DNA damage resistance is a major barrier to effective DNA-damaging therapy in multiple myeloma (MM). To discover novel mechanisms through which MM cells overcome DNA damage, we investigated how MM cells become resistant to antisense oligonucleotide (ASO) therapy targeting ILF2, a DNA damage regulator that is overexpressed in 70% of MM patients whose disease has progressed after standard therapies have failed. Here, we show that MM cells undergo an adaptive metabolic rewiring and rely on oxidative phosphorylation to restore energy balance and promote survival in response to DNA damage activation. Using a CRISPR/Cas9 screening strategy, we identified the mitochondrial DNA repair protein DNA2, whose loss of function suppresses MM cells' ability to overcome ILF2 ASO-induced DNA damage, as being essential to counteracting oxidative DNA damage and maintaining mitochondrial respiration. Our study revealed a novel vulnerability of MM cells that have an increased demand for mitochondrial metabolism upon DNA damage activation. STATEMENT OF SIGNIFICANCE: Metabolic reprogramming is a mechanism through which cancer cells maintain survival and become resistant to DNA-damaging therapy. Here, we show that targeting DNA2 is synthetically lethal in myeloma cells that undergo metabolic adaptation and rely on oxidative phosphorylation to maintain survival after DNA damage activation.

Isolation, culture, and immunophenotypic analysis of bone marrow HSPCs from patients with myelodysplastic syndromes.

Drug testing assays in hematopoietic stem and progenitor cells (HSPCs) are fundamental in biological studies of myelodysplastic syndromes (MDS) but have historically entailed a technical challenge. This protocol allows the efficient isolation of MDS HSPCs from bone marrow mononuclear cell fractions and their culturing with the support of stromal cells for improved maintenance during drug testing. Lastly, specific steps are given to quantify surviving cells and assess changes in the HSPC hierarchies. For complete details on the use and execution of this protocol, please refer to Ganan-Gomez et al. (2022).

Azacitidine plus venetoclax in patients with high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia: phase 1 results of a single-centre, dose-escalation, dose-expansion, phase 1-2 study.

BACKGROUND: Therapies beyond hypomethylating agents such as azacitidine are needed in high-risk myelodysplastic syndromes. Venetoclax is an orally bioavailable small molecule BCL-2 inhibitor that is synergistic with hypomethylating agents. We therefore aimed to evaluate the safety, tolerability, and preliminary activity of azacitidine combined with venetoclax for treatment-naive and relapsed or refractory high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia. METHODS: We did a single centre, dose-escalation, dose-expansion, phase 1-2 trial at the University of Texas MD Anderson Cancer Center (Houston, TX, USA). This Article details the phase 1 results. We enrolled patients (≥18 years) with treatment-naive or relapsed or refractory high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia and bone marrow blasts of more than 5%. No specific Eastern Cooperative Oncology Group status restriction was used. Patients were treated with intravenous or subcutaneous azacitidine (75 mg/m2) for 5 days and oral venetoclax (100-400 mg) for 7-14 days. The primary outcome was safety and tolerability as well as determination of the maximum tolerated dose and recommended phase 2 dose of the azacitidine and venetoclax combination using a 3 + 3 study design. All patients who received one dose of study drug were included in the analyses. This study is registered with ClinicalTrials.gov, number NCT04160052. The phase 2 dose-expansion part of the trial is ongoing. FINDINGS: Between Nov 12, 2019, and Dec 17, 2021, a total of 23 patients were enrolled in the phase 1 portion of this study (17 [74%] hypomethylating agent naive and six [26%] post-hypomethylating agent failure). 18 (78%) patients were male and five (22%) were female; 21 (91%) were white and two (9%) were Asian. Median follow-up was 13·2 months (IQR 6·8-18·3). The maximum tolerated dose was not reached and the recommended phase 2 dose was established as azacitidine 75 mg/m2 for 5 days plus venetoclax 400 mg for 14 days. The most common grade 3-4 treatment-emergent adverse events were neutropenia (nine [39%] of 23), thrombocytopenia (nine [39%]), lung infection (seven [30%]), and febrile neutropenia (four [17%]). Three deaths due to sepsis, which were not deemed treatment-related, occurred on the study drugs. The overall response rate was 87% (95% CI 66-97; 20 of 23 patients). INTERPRETATION: Azacitidine with venetoclax is safe and shows encouraging activity in patients with high-risk myelodysplastic syndromes or chronic myelomonocytic leukaemia. FUNDING: MD Anderson Cancer Center.

MDM2 antagonist improves therapeutic activity of azacitidine in myelodysplastic syndromes and chronic myelomonocytic leukemia.

Failure of hypomethylation agent (HMA) treatments is an important issue in myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML). Recent studies indicated that function of wildtype TP53 positively impacts outcome of HMA treatments. We investigated the combination of the HMA azacitidine (AZA) with DS-3032b and DS-5272, novel antagonists of the TP53 negative regulator MDM2, in cellular and animal models of MDS and CMML. In TP53 wildtype myeloid cell line, combinational effects of DS-3032b or DS-5272 with AZA were observed. In Tet2-knockout mouse model of MDS and CMML, DS-5272 and AZA combination ameliorated disease-like phenotype. RNA-Seq analysis in mouse bone marrow hematopoietic stem and progenitors indicated that DS-5272 and AZA combination caused down-regulation of leukemia stem cell marker genes and activation of pathways of TP53 function and stability. These findings demonstrate that combining an MDM2 antagonist with AZA has potential to improve AZA treatment in TP53 wildtype MDS and CMML.

Transcriptomic Signatures of Hypomethylating Agent Failure in Myelodysplastic Syndromes and Chronic Myelomonocytic Leukemia.

Hypomethylating agents (HMAs) are the standard of care for myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML). HMA treatment failure is a major clinical problem and its mechanisms are poorly characterized. We performed RNA sequencing in CD34+ bone marrow stem hematopoietic stem and progenitor cells (BM-HSPCs) from 51 patients with CMML and MDS before HMA treatment and compared transcriptomic signatures between responders and nonresponders. We observed very few genes with significant differential expression in HMA non-responders versus responders, and the commonly altered genes in non-responders to both azacitidine (AZA) and decitabine (DAC) treatments were immunoglobulin genes. Gene set analysis identified 78 biological pathways commonly altered in non-responders to both treatments. Among these, we determined that the γ-aminobutyric acid (GABA) receptor signaling significantly affected hematopoiesis in both human BM-HSPCs and mice, indicating that the transcriptomic signatures identified here could serve as candidate biomarkers and therapeutic targets for HMA failure in MDS and CMML.

A machine learning-based method for automatically identifying novel cells in annotating single-cell RNA-seq data.

MOTIVATION: Single-cell RNA sequencing (scRNA-seq) has been widely used to decompose complex tissues into functionally distinct cell types. The first and usually the most important step of scRNA-seq data analysis is to accurately annotate the cell labels. In recent years, many supervised annotation methods have been developed and shown to be more convenient and accurate than unsupervised cell clustering. One challenge faced by all the supervised annotation methods is the identification of the novel cell type, which is defined as the cell type that is not present in the training data, only exists in the testing data. Existing methods usually label the cells simply based on the correlation coefficients or confidence scores, which sometimes results in an excessive number of unlabeled cells. RESULTS: We developed a straightforward yet effective method combining autoencoder with iterative feature selection to automatically identify novel cells from scRNA-seq data. Our method trains an autoencoder with the labeled training data and applies the autoencoder to the testing data to obtain reconstruction errors. By iteratively selecting features that demonstrate a bi-modal pattern and reclustering the cells using the selected feature, our method can accurately identify novel cells that are not present in the training data. We further combined this approach with a support vector machine to provide a complete solution for annotating the full range of cell types. Extensive numerical experiments using five real scRNA-seq datasets demonstrated favorable performance of the proposed method over existing methods serving similar purposes. AVAILABILITY AND IMPLEMENTATION: Our R software package CAMLU is publicly available through the Zenodo repository (https://doi.org/10.5281/zenodo.7054422) or GitHub repository (https://github.com/ziyili20/CAMLU). SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Targeting the EIF2AK1 Signaling Pathway Rescues Red Blood Cell Production in SF3B1-Mutant Myelodysplastic Syndromes With Ringed Sideroblasts.

SF3B1 mutations, which occur in 20% of patients with myelodysplastic syndromes (MDS), are the hallmarks of a specific MDS subtype, MDS with ringed sideroblasts (MDS-RS), which is characterized by the accumulation of erythroid precursors in the bone marrow and primarily affects the elderly population. Here, using single-cell technologies and functional validation studies of primary SF3B1-mutant MDS-RS samples, we show that SF3B1 mutations lead to the activation of the EIF2AK1 pathway in response to heme deficiency and that targeting this pathway rescues aberrant erythroid differentiation and enables the red blood cell maturation of MDS-RS erythroblasts. These data support the development of EIF2AK1 inhibitors to overcome transfusion dependency in patients with SF3B1-mutant MDS-RS with impaired red blood cell production. SIGNIFICANCE: MDS-RS are characterized by significant anemia. Patients with MDS-RS die from a shortage of red blood cells and the side effects of iron overload due to their constant need for transfusions. Our study has implications for the development of therapies to achieve long-lasting hematologic responses. This article is highlighted in the In This Issue feature, p. 476.

Cooperation between KDM6B overexpression and TET2 deficiency in the pathogenesis of chronic myelomonocytic leukemia.

Loss-of-function TET2 mutations are recurrent somatic lesions in chronic myelomonocytic leukemia (CMML). KDM6B encodes a histone demethylase involved in innate immune regulation that is overexpressed in CMML. We conducted genomic and transcriptomic analyses in treatment naïve CMML patients and observed that the patients carrying both TET2 mutations and KDM6B overexpression constituted 18% of the cohort and 42% of patients with TET2 mutations. We therefore hypothesized that KDM6B overexpression cooperated with TET2 deficiency in CMML pathogenesis. We developed a double-lesion mouse model with both aberrations, and discovered that the mice exhibited a more prominent CMML-like phenotype than mice with either Tet2 deficiency or KDM6B overexpression alone. The phenotype includes monocytosis, anemia, splenomegaly, and increased frequencies and repopulating activity of bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs). Significant transcriptional alterations were identified in double-lesion mice, which were associated with activation of proinflammatory signals and repression of signals maintaining genome stability. Finally, KDM6B inhibitor reduced BM repopulating activity of double-lesion mice and tumor burden in mice transplanted with BM-HSPCs from CMML patients with TET2 mutations. These data indicate that TET2 deficiency and KDM6B overexpression cooperate in CMML pathogenesis of and that KDM6B could serve as a potential therapeutic target in this disease.

Stem cell architecture drives myelodysplastic syndrome progression and predicts response to venetoclax-based therapy.

Myelodysplastic syndromes (MDS) are heterogeneous neoplastic disorders of hematopoietic stem cells (HSCs). The current standard of care for patients with MDS is hypomethylating agent (HMA)-based therapy; however, almost 50% of MDS patients fail HMA therapy and progress to acute myeloid leukemia, facing a dismal prognosis due to lack of approved second-line treatment options. As cancer stem cells are the seeds of disease progression, we investigated the biological properties of the MDS HSCs that drive disease evolution, seeking to uncover vulnerabilities that could be therapeutically exploited. Through integrative molecular profiling of HSCs and progenitor cells in large patient cohorts, we found that MDS HSCs in two distinct differentiation states are maintained throughout the clinical course of the disease, and expand at progression, depending on recurrent activation of the anti-apoptotic regulator BCL-2 or nuclear factor-kappa B-mediated survival pathways. Pharmacologically inhibiting these pathways depleted MDS HSCs and reduced tumor burden in experimental systems. Further, patients with MDS who progressed after failure to frontline HMA therapy and whose HSCs upregulated BCL-2 achieved improved clinical responses to venetoclax-based therapy in the clinical setting. Overall, our study uncovers that HSC architectures in MDS are potential predictive biomarkers to guide second-line treatments after HMA failure. These findings warrant further investigation of HSC-specific survival pathways to identify new therapeutic targets of clinical potential in MDS.

Hematopoiesis under telomere attrition at the single-cell resolution.

The molecular mechanisms that drive hematopoietic stem cell functional decline under conditions of telomere shortening are not completely understood. In light of recent advances in single-cell technologies, we sought to redefine the transcriptional and epigenetic landscape of mouse and human hematopoietic stem cells under telomere attrition, as induced by pathogenic germline variants in telomerase complex genes. Here, we show that telomere attrition maintains hematopoietic stem cells under persistent metabolic activation and differentiation towards the megakaryocytic lineage through the cell-intrinsic upregulation of the innate immune signaling response, which directly compromises hematopoietic stem cells' self-renewal capabilities and eventually leads to their exhaustion. Mechanistically, we demonstrate that targeting members of the Ifi20x/IFI16 family of cytosolic DNA sensors using the oligodeoxynucleotide A151, which comprises four repeats of the TTAGGG motif of the telomeric DNA, overcomes interferon signaling activation in telomere-dysfunctional hematopoietic stem cells and these cells' skewed differentiation towards the megakaryocytic lineage. This study challenges the historical hypothesis that telomere attrition limits the proliferative potential of hematopoietic stem cells by inducing apoptosis, autophagy, or senescence, and suggests that targeting IFI16 signaling axis might prevent hematopoietic stem cell functional decline in conditions affecting telomere maintenance.

Type I interferon upregulation and deregulation of genes involved in monopoiesis in chronic myelomonocytic leukemia.

Chronic myelomonocytic leukemia (CMML) is characterized by myelomonocytic bias and monocytic proliferation. Whether cell-intrinsic innate immune or inflammatory upregulation mediate disease pathogenesis and phenotype or whether the degree of aberrant monocytic differentiation influences outcomes remains unclear. We compared the transcriptomic features of bone marrow CD34+ cells from 19 patients with CMML and compared to healthy individuals. A total of 1495 genes had significantly differential expression in CMML (q<0.05, fold change>2), including 1271 genes that were significantly upregulated and 224 that were significantly downregulated in CMML. Top upregulated genes were associated with interferon (IFN) alpha and beta signaling, chemokine receptors, IFN gamma, G protein-coupled receptor ligand signaling, and genes involved in immunomodulatory interactions between lymphoid and non-lymphoid cells. Additionally, 6 gene sets were differentially upregulated and 139 were significantly downregulated in patients with myeloproliferative compared to myelodysplastic CMML. A total of 23 genes involved in regulation of monopoiesis were upregulated in CMML compared to healthy controls. We developed a prediction model using Cox regression including 3 of these genes, which differentiated patients into two prognostic subsets with distinct survival outcomes. This data warrants further evaluation of the roles and therapeutic potential of type I IFN signaling and monopoiesis in CMML.

LILRB4 expression in chronic myelomonocytic leukemia and myelodysplastic syndrome based on response to hypomethylating agents.

LILRB4 is expressed in AML M4/M5 cells and negatively regulates immune cell activation via T-cell suppression. Its expression and role in chronic myelomonocytic leukemia (CMML) and myelodysplastic syndrome (MDS) are unknown. We investigated LILRB4 expression in 19 CMML and 27 MDS patients and correlated it with response to subsequent hypomethylating agent (HMA) therapy. LILRB4 RNA expression was increased in CMML patients when compared to MDS patients and healthy controls (q < 0.1) and slightly increased in patients who responded to HMAs (q > 0.1). Pathway analysis revealed upregulation of PD-1 signaling, CTLA-4 signaling, and inflammatory response, and gene correlates were positively associated with CTLA-4 expression. Given current modest results with immunotherapy in myeloid malignancies, further investigation of LILRB4 as an immune checkpoint inhibitor target is needed. With the positive correlation between LILRB4 and CTLA-4 expression, combining anti-LILRB4 and anti-CTLA-4 agents may be a novel therapeutic approach in myeloid malignancies that warrants larger studies.

Transcriptomic analysis implicates necroptosis in disease progression and prognosis in myelodysplastic syndromes.

Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis and cytopenias due to uncontrolled programmed cell death. The presence of pro-inflammatory cytokines and constitutive activation of innate immunity signals in MDS cells suggest inflammatory cell death, such as necroptosis, may be responsible for disease phenotype. We evaluated 64 bone marrow samples from 55 patients with MDS or chronic myelomonocytic leukemia (CMML) obtained prior to (n = 46) or after (n = 18) therapy with hypomethylating agents (HMAs). RNA from sorted bone marrow CD34+ cells was isolated and subject to amplification and RNA-Seq. Compared with healthy controls, expression levels of MLKL (CMML: 2.09 log2FC, p = 0.0013; MDS: 1.89 log2FC, p = 0.003), but not RIPK1 or RIPK3, were significantly upregulated. Higher expression levels of MLKL were associated with lower hemoglobin levels at diagnosis (-0.19 log2FC per 1 g/dL increase of Hgb, p = 0.03). Significant reduction in MLKL levels was observed after HMA therapy (-1.06 log2FC, p = 0.05) particularly among nonresponders (-2.89 log2FC, p = 0.06). Higher RIPK1 expression was associated with shorter survival (HR 1.92, 95% CI 1.00-3.67, p = 0.049 by Cox proportional hazards). This data provides further support for a role of necroptosis in MDS, and potentially response to HMAs and prognosis. This data also indicate that RIPK1/RIPK3/MLKL are potential therapeutic targets in MDS.