Immune microenvironment dysfunctions enable malignification at the onset of myelodysplastic syndromes

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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

Targeting DNA2 Overcomes Metabolic Reprogramming in 1q21 Multiple Myeloma

View full abstracthttps://openworks.mdanderson.org/leading-edge/1018/thumbnail.jp

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

View full abstracthttps://openworks.mdanderson.org/leading-edge/1025/thumbnail.jp

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

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 to 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 1g/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 non-responders (−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 indicates that RIPK1/ RIPK3/MLKL are potential therapeutic targets in MDS