Biology and relevance of human acute myeloid leukemia stem cells. Blood. 2017;129:1577-1585. [PMID: 28159741 DOI: 10.1182/blood-2016-10-696054]

Metabolic landscape and rewiring in normal hematopoiesis, leukemia and aging

Recent advancements in metabolism research have demonstrated its critical roles in a lot of critical biological processes, including stemness maintenance, cell differentiation, proliferation, and function. Hematopoiesis is the fundamental cell differentiation process with the production of millions of red blood cells per second in carrying oxygen and white blood cells in fighting infection and cancers. The differentiation processes of hematopoietic stem and progenitor cells (HSPCs) are accompanied by significant metabolic reprogramming. In hematological malignancy, metabolic reprogramming is also essential to the malignant hematopoiesis processes. The metabolic rewiring is driven by distinct molecular mechanisms that meet the specific demands of different target cells. Leukemic cells, for instance, adopt unique metabolic profiles to support their heightened energy needs for survival and proliferation. Moreover, aging HSPCs exhibit altered energy consumption compared to their younger counterparts, often triggering protective mechanisms at the cellular level. In this review, we provide a comprehensive analysis of the metabolic processes involved in hematopoiesis and the metabolic rewiring that occurs under adverse conditions. In addition, we highlight current research directions and discuss the potential of targeting metabolic pathways for the management of hematological malignancies and aging.

Molecular, clinical, and prognostic implications of RAS pathway alterations in adult acute myeloid leukemia

Alterations in the RAS pathway underscore the pathogenic complexity of acute myeloid leukemia (AML), yet the full spectrum, including CBL, NF1, PTPN11, KRAS, and NRAS, remains to be fully elucidated. In this retrospective study of 735 adult AML patients, the incidence of RAS pathway alterations was 32.4%, each with distinct clinical characteristics. Venetoclax combined with hypomethylating agents (VEN + HMA) did not significantly improve response rates compared to intensive chemotherapy (IC) group. In the IC group, PTPN11 mutations in the N-SH2 domain showed a trend toward poorer prognosis, though not statistically significant in multivariate analysis, while NRAS mutations correlated with improved outcomes. In the VEN + HMA group, PTPN11 mutations in the N-SH2 domain emerged as an independent adverse prognostic marker. NRAS or KRAS mutations showed no survival advantage compared to wild-type, aligning with their intermediate-risk classification in the 2024 ELN guidelines. These findings emphasize the need for treatment-specific risk stratification for RAS pathway mutations in AML.

MicroRNA-126: From biology to therapeutics

MicroRNA-126 (miR-126) has emerged as one of the most extensively studied microRNAs in the context of human diseases, particularly in vascular disorders and cancer. Its high degree of conservation across vertebrates underscores its evolutionary significance and essential functional roles. Extensive research has been devoted to elucidating the molecular mechanisms through which miR-126 modulates key physiological and pathological processes, including angiogenesis, immune response, inflammation, tumor growth, and metastasis. Furthermore, miR-126 plays a causal role in the pathogenesis of various diseases, serving as potential biomarkers for disease prediction, diagnosis, prognosis and drug response, as well as a promising therapeutic target. In this review, we synthesize findings from 283 articles, focusing on the roles of miR-126 in critical biological processes such as cell development, survival, cycle regulation, proliferation, migration, invasion, communication, and metabolism. Additionally, miR-126 represents a promising candidate for miRNA-based therapeutic strategies. A comprehensive understanding and evaluation of miR-126 are crucial for advancing its clinical applications and therapeutic potential.

Distinct leukemogenic mechanism of acute promyelocytic leukemia based on genomic structure of PML::RARα

Leukemic stem cells (LSCs) of acute myeloid leukemia (AML) can be enriched in the CD34+CD38- fraction and reconstitute human AML in vivo. However, in acute promyelocytic leukemia (APL), which constitutes 10% of all AML cases and is driven by promyelocytic leukemia-retinoic acid receptor alpha (PML::RARα) fusion genes, the presence of LSCs has long been unidentified because of the difficulty in efficient reconstitution of human APL in vivo. Herein, we show that LSCs of the short-type isoform APL, a subtype of APL defined by different breakpoints of the PML gene, concentrate in the CD34+CD38- fraction and express T cell immunoglobulin mucin-3 (TIM-3). Short-type APL cells exhibited distinct gene expression signatures, including LSC-related genes, compared to the other types of APL. Moreover, CD34+CD38-TIM-3+ short-type APL cells efficiently reconstituted human APL in xenograft models with high penetration, whereas CD34- differentiated APL cells did not. Furthermore, CD34+CD38-TIM-3+ short-type APL cells reconstituted leukemia cells after serial transplantation. Thus, short-type APL was hierarchically organized by self-renewing APL-LSCs. The identification of LSCs in a subset of APL and establishment of an efficient patient-derived xenograft model may contribute to further understanding the APL leukemogenesis and devise individual treatments for the eradication of APL LSCs.

A quiescence-like/TGF-β1-specific CRISPRi screen reveals drug uptake transporters as secondary targets of kinase inhibitors in AML

Relapse in acute myeloid leukemia (AML) is driven by resistant subclones that survive chemotherapy. It is assumed that these resilient leukemic cells can modify their proliferative behavior by entering a quiescent-like state, similar to healthy hematopoietic stem cells (HSCs). These dormant cells can evade the effects of cytostatic drugs that primarily target actively dividing cells. Although quiescence has been extensively studied in healthy hematopoiesis and various solid cancers, its role in AML has remained unexplored. In this study, we applied an HSC-derived quiescence-associated gene signature to an AML patient cohort and found it to be strongly correlated with poor prognosis and active TGF-β signaling. In vitro treatment with TGF-β1 induces a quiescence-like phenotype, resulting in a G0 shift and reduced sensitivity to cytarabine. To find potential therapeutic targets that prevent AML-associated quiescence and improve response to cytarabine, we conducted a comprehensive CRISPR interference (CRISPRi) screen combined with TGF-β1 stimulation. This approach identified TGFBR1 inhibitors, like vactosertib, as effective agents for preventing the G0 shift in AML cell models. However, pretreatment with vactosertib unexpectedly induced complete resistance to cytarabine. To elucidate the underlying mechanism, we performed a multi-faceted approach combining a second CRISPRi screen, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and in silico analysis. Our findings revealed that TGFBR1 inhibitors unintentionally target the nucleoside transporter SLC29A1 (ENT1), leading to reduced intracellular cytarabine levels. Importantly, we found that this drug interaction is not unique to TGFBR1 inhibitors, but extends to other clinically significant kinase inhibitors, such as the FLT3 inhibitor midostaurin. These findings may have important implications for optimizing combination therapies in AML treatment.

Prognostic value of circular RNAs expression and their correlation with clinicopathological features in acute myeloid leukemia: a systematic review and meta-analysis

Acute myeloid leukemia (AML) prognosis is affected by unique factors to each individual and studies have indicated that dysregulated expression of circRNAs may serve as prognostic biomarkers for AML. Therefore, we conducted this study to assess the prognostic value of circRNAs expression and it's correlation with clinicopathological features. Comprehensive search was conducted in WOS, Scopus, PubMed, Google Scholar, ProQuest, and grey literature. The certainty of evidence was assessed using the modified GRADE approach for prognostic and clinicopathological meta-analysis. The hazard ratio (HR) was employed to assess the prognostic value of dysregulated expression of circRNAs in patient survival, while the risk ratio (RR) was utilized to analyze the correlation between circRNAs and clinicopathological features. Our results demonstrated that dysregulation of circRNAs expression was associated with poor prognosis related to overall survival (OS) indicator (HR:2.05; 95%CI: 1.75-2.40) and also related to non-OS indicators such as (EFS, LFS, RFS, and DFS) (HR:2.09, 95%CI: 1.47-2.97). Priori and post-hoc subgroup analysis was conducted to describe variables that potentially affected heterogeneity and effect size. We also evaluated the association between dysregulated expression of circRNAs and 19 clinicopathological parameters. Our results show that there is significant relationship between the dysregulated expression of circRNAs and the mentioned parameters: type M6 vs. other types (RR:1.51, 95% CI:1.12-2.03), FLT3-ITD mutation (RR:1.17, 95%CI: 1.00-1.36), and risk status (RR:1.35, 95% CI: 1.13-1.60). This systematic review and meta-analysis suggest that the investigation of circRNAs expression changes can serve as valuable biomarkers for the assessment of prognosis in AML patients.

CD73: a new immune checkpoint for leukemia treatment

Recent studies on the pathogenesis of leukemia have led to remarkable advances in disease treatment. Numerous studies have shown the potential and viability of immune responses against leukemia. In the classical pathway, this process is often initiated by the upstream activity of CD39, which hydrolyzes extracellular adenosine triphosphate (ATP) and adenosine diphosphate (ADP) to AMP. Subsequently, CD73 acts on AMP to generate adenosine, contributing to an immunosuppressive microenvironment. However, CD73 can also utilize substrates derived from other molecules through the non-canonical NAD+ pathway, specifically via the CD38/CD203a/CD73 axis, further enhancing adenosine production and facilitating immune escape. Targeting CD73 has shown potential in disrupting these immunosuppressive pathways, thereby enhancing anti-leukemic immune responses and improving patient outcomes. Inhibiting CD73 not only reduces the levels of immunosuppressive adenosine but also increases the efficacy of existing immunotherapies, such as PD-1/PD-L1 inhibitors, making it a versatile therapeutic target in leukemia treatment. This review discusses the potential of CD73 as a therapeutic target and emphasizes its unique position in the immune escape mechanism of leukemia. Moreover, this review provides an overview of the current research progress and future trends, emphasizing the clinical significance of targeting CD73 and other potential therapeutic strategies in leukemia.

Sonidegib Inhibits the Adhesion of Acute Myeloid Leukemia to the Bone Marrow in Hypoxia: An Optical Tweezer Study

Background: Acute myeloid leukemia (AML) is a heterogeneous disease highly resistant to chemotherapeutic agents. Leukemia stem cells (LSCs) can enter a dormant state and avoid apoptosis in the protective niche of the bone marrow (BM) microenvironment. Moreover, bone marrow stromal cells protect leukemia cells by promoting pro-survival signaling pathways and drug resistance. Therefore, attenuating interactions between leukemia cells and BM cells may have a positive therapeutic effect. Objectives: In this work, we hypothesized that sondages may inhibit the adhesion of leukemia cells to the bone marrow by inhibiting the Hedgehog (Hh) signaling pathway. The Hedgehog pathway is a key therapeutic target in AML due to its role in leukemic cell growth and survival. Methods: We investigated the effects of sonidegib on the adhesion of individual OCI-AML3 cells to a bone marrow stromal spheroid derived from the HS-5 cell line. For this purpose, we precisely determined the minimum cell-to-cell adhesion time using optical tweezers under normoxic (21% of O2) and hypoxic (1% of O2) conditions. Results: Our results demonstrated that sonidegib significantly increased the minimum cell-to-cell adhesion time necessary for leukemic cells to establish adhesive bonds with bone marrow stromal cells, thereby indicating a reduction in their adhesive properties. Additionally, we showed that sonidegib is particularly effective at hypoxic oxygen concentrations. Conclusions: The results obtained in this study suggest that sonidegib, through its modulation of the Hedgehog signaling pathway, holds promise as a potential therapeutic approach to target leukemic cell adhesion within the bone marrow microenvironment.

Single-cell multiomics reveals a gene regulatory circuit driving leukemia cell differentiation

Cancer differentiation therapy aims to induce the maturation of neoplastic cells, but the mechanisms regulating cell fate decisions in oncogenic contexts remain unclear. In this study, we integrated single-cell chromatin accessibility and single-cell transcriptome analyses to explore the regulatory trajectories of a classical PML/RARα+ acute promyeloid leukemia (APL) cell line (NB4) post treatment by all-trans-retinoid acid (ATRA). Our findings indicated that ATRA activated specific PML/RARα-target enhancers to trigger a regulatory circuit composed of a positive feedforward gene regulatory circuit involving two transcription factors, SPI1 and CEBPE. This regulatory circuit was both necessary and sufficient to drive NB4 cells through an intermediate cell fate decision point to initiate terminal granulopoiesis. Moreover, ectopic expression of SPI1 and CEBPE promoted granulocytic differentiation in non-APL leukemia cell lines HL60 and K562. Our study sheds mechanistic insights into the differentiation trajectories induced by ATRA and illustrates a gene regulatory circuit that could be widely applied to promote differentiation of leukemia cells.

Potential value of immunogenic cell death related-genes in refining European leukemiaNet guidelines classification and predicting the immune infiltration landscape in acute myeloid leukemia

Immunogenic cell death (ICD) is the kind of cell death that triggers the immune system. It affects several tumors, whereas its significance for prognosis in acute myeloid leukemia (AML) remains uncertain. AML categorization by cytogenetic variables is inaccurate. In addition, risk stratification of AML based on cytogenetics is imprecise. The data of AML patients were extracted from 4 databases, a total of 1,537 patients. Univariate and LASSO Cox regression analyses were conducted to construct an ICD risk signature (ICDRS). The ICDRS showed strong prognostic value for AML through Kaplan-Meier, Cox, ROC analyses and nomogram. Combining the ICDRS with the European LeukemiaNet (ELN) classification to redefine the risk stratification can better predict the prognosis of AML. Moreover, the ICDRS was examined to identify gene functional enrichment, immunological characteristics, drug susceptibility, and somatic mutation, which revealed considerable variations among different risk categories. We further validated the expression of ICDRS in the AML bone marrow microenvironment by single-cell RNA (scRNA) analysis. Ultimately, the functional role of CASP1 was proven in AML by a series of in-vitro experiments. Our study highlights the significant impact of ICDRS on AML, which may improve ELN risk classification, predict immune landscapes, and guide personalized therapy.

Cell Marker Accordion: interpretable single-cell and spatial omics annotation in health and disease

Single-cell technologies offer a unique opportunity to explore cellular heterogeneity in health and disease. However, reliable identification of cell types and states represents a bottleneck. Available databases and analysis tools employ dissimilar markers, leading to inconsistent annotations and poor interpretability. Furthermore, current tools focus mostly on physiological cell types, limiting their applicability to disease. We developed the Cell Marker Accordion, a user-friendly platform providing automatic annotation and unmatched biological interpretation of single-cell populations, based on consistency weighted markers. We validated our approach on multiple single-cell and spatial datasets from different human and murine tissues, improving annotation accuracy in all cases. Moreover, we show that the Cell Marker Accordion can identify disease-critical cells and pathological processes, extracting potential biomarkers in a wide variety of disease contexts. The breadth of these applications elevates the Cell Marker Accordion as a fast, flexible, faithful and standardized tool to annotate and interpret single-cell and spatial populations in studying physiology and disease.

Co-occurrence of hydatid cyst liver with acute myeloid leukaemia: A rare case report

The term "hydatid disease" refers to echinococcosis. Echinococcosis is a zoonotic disease caused by the larval stage of the Echinococcus parasite. The disease is widespread in regions where the parasite is endemic, particularly in developing nations like India. However, there are only a couple of documented case studies of echinococcosis associated with hematological malignancy in the literature. We present an extremely uncommon case of a 36-year-old male who had liver hydatidosis and was diagnosed with acute myeloid leukemia (AML)-M1. The patient received treatment for acute myeloid leukemia (daunomycin, cytarabine, and 5-azacytidine), followed by management of hydatid disease after complete remission of acute leukemia. The patient underwent periodic evaluations for one year and exhibited satisfactory improvement.

IRE1α-XBP1 safeguards hematopoietic stem and progenitor cells by restricting pro-leukemogenic gene programs

Hematopoietic stem cells must mitigate myriad stressors throughout their lifetime to ensure normal blood cell generation. Here, we uncover unfolded protein response stress sensor inositol-requiring enzyme-1α (IRE1α) signaling in hematopoietic stem and progenitor cells (HSPCs) as a safeguard against myeloid leukemogenesis. Activated in part by an NADPH oxidase-2 mechanism, IRE1α-induced X-box binding protein-1 (XBP1) mediated repression of pro-leukemogenic programs exemplified by the Wnt-β-catenin pathway. Transcriptome analysis and genome-wide mapping of XBP1 targets in HSPCs identified an '18-gene signature' of XBP1-repressed β-catenin targets that were highly expressed in acute myeloid leukemia (AML) cases with worse prognosis. Accordingly, IRE1α deficiency cooperated with a myeloproliferative oncogene in HSPCs to cause a lethal AML in mice, while genetic induction of XBP1 suppressed the leukemia stem cell program and activity of patient-derived AML cells. Thus, IRE1α-XBP1 signaling safeguards the integrity of the blood system by restricting pro-leukemogenic programs in HSPCs.

Dietary Modulation of Fatty Acid Oxidation Imparts Stem Cell Protection in Bone Marrow

Hematopoietic stem cells (HSCs) maintain production of all functional blood cells and are located within the bone marrow. In pathological conditions, such as obesity or leukemia, changes in these cells contribute to disease pathophysiology. In this study, we examined the impact of metabolic modulation of stem and progenitor cells within the bone marrow during diet-induced obesity (DIO) and leukemia relapse. Avocatin B (Avo), an inhibitor of fatty acid oxidation (FAO), was provided in the diet and its impact on stem cells using two disease models was tested. In DIO, high fat diet(HFD)-induced alterations in HSC number and function were attenuated with Avo (HFD: 46.9% decrease compared to control; p < 0.001; whereas DIO + Avo: 58.8% recovery; p < 0.05). In leukemia relapse, dietary Avo delayed disease reoccurrence. Taken together, addition of Avo into the diet imparts protection in the bone marrow.

Stem cell status and prognostic applications of cuproptosis-associated lncRNAs in acute myeloid leukemia

Introduction

Acute myeloid leukemia (AML), a highly heterogeneous hematological malignancy, remains a major challenge in adult oncology. Stem cell research has highlighted the crucial role of long noncoding RNA (lncRNA) in regulating cellular differentiation and self-renewal processes, which are pivotal in AML pathogenesis and therapy resistance.

Methods

This study explores the relationship between cuproptosis-related lncRNAs and AML prognosis, providing novel insights into their impact on hematopoietic stem and progenitor cells.

Results

We collected clinical information from 214 AML patients in our center and analyzed the association between granulocyte recovery after chemotherapy, cuproptosis, and prognosis. Additionally, we developed a prognostic model-the cuproptosis-associated long noncoding RNA prognostic model (CRLPM)-y analyzing data from The Cancer Genome Atlas (TCGA). Patients were stratified into high- and low-risk groups based on CRLPM, revealing significant survival differences. High-risk patients demonstrated lower sensitivity to chemotherapeutic agents such as Axitinib, GSK429286A, Navitoclax, and ZM-447439, underscoring the need for alternative therapeutic strategies.

Discussion

CRLPM offers a promising framework for integrating stem cell-focused approaches into personalized treatment regimens, paving the way for precision medicine in AML management.

ONC213: a novel strategy to resensitize resistant AML cells to venetoclax through induction of mitochondrial stress

BACKGROUND

Venetoclax + azacitidine is a frontline treatment for older adult acute myeloid leukemia (AML) patients and a salvage therapy for relapsed/refractory patients who have been treated with intensive chemotherapy. While this is an important treatment option, many patients fail to achieve complete remission and of those that do, majority relapse. Leukemia stem cells (LSCs) are believed to be responsible for AML relapse and can be targeted through oxidative phosphorylation reduction. We previously reported that ONC213 disrupts oxidative phosphorylation and decreases Mcl-1 protein, which play a key role in venetoclax resistance. Here we investigated the antileukemic activity and underlying molecular mechanism of the combination of ONC213 + venetoclax against AML cells.

METHODS

Flow cytometry was used to determine drug-induced apoptosis. Protein level changes were determined by western blot. An AML cell line-derived xenograft mouse model was used to determine the effects of ONC213 + venetoclax on survival. A patient-derived xenograft (PDX) mouse model was used to determine drug effects on CD45+/CD34+/CD38-/CD123 + cells. Colony formation assays were used to assess drug effects on AML progenitor cells. Mcl-1 and Bax/Bak knockdown and Mcl-1 overexpression were used to confirm their role in the mechanism of action. The effect of ONC213 + venetoclax on mitochondrial respiration was determined using a Seahorse bioanalyzer.

RESULTS

ONC213 + venetoclax synergistically kills AML cells, including those resistant to venetoclax alone as well as venetoclax + azacitidine. The combination significantly reduced colony formation capacity of primary AML progenitors compared to the control and either treatment alone. Further, the combination prolonged survival in an AML cell line-derived xenograft model and significantly decreased LSCs in an AML PDX model.

CONCLUSIONS

ONC213 can resensitize VEN + AZA-resistant AML cells to venetoclax therapy and target LSCs ex vivo and in vivo.

Reprogramming of Fatty Acid Metabolism in Acute Leukemia

Fatty acids are essential biomolecules that support several cellular processes, such as membrane structures, energy storage and production, as well as signal transduction. Accordingly, changes in fatty acid metabolism can have a significant impact on cell behavior, such as growth, survival, proliferation, differentiation, and motility. Therefore, it is not surprising that many aspects of fatty acid metabolism are frequently dysregulated in human cancer, including in highly aggressive blood cancers such as acute leukemia. The aims of this review are to summarize the aspects of fatty acid metabolism that are specifically coopted in acute leukemia as well as current preclinical strategies for targeting fatty acid metabolism in these cancers.

Cellular automata modelling of leukaemic stem cell dynamics in acute myeloid leukaemia: insights into predictive outcomes and targeted therapies

Acute myeloid leukaemia (AML) is a haematologic malignancy with high relapse rates in both adults and children. Leukaemic stem cells (LSCs) are central to leukaemopoiesis, treatment response and relapse and frequently associated with measurable residual disease (MRD). However, the dynamics of LSCs within the AML microenvironment is not fully understood. This study utilized three-dimensional cellular automata (CA) modelling to simulate LSC behaviour and treatment response under induction chemotherapy. Our study revealed: (i) a correlation between LSC persistence post-induction chemotherapy and risk of AML relapse; (ii) MRD negativity based on LSC count may not reliably predict outcomes, supporting clinical evidence that patients with MRD-negative status can still be at risk of relapse; (iii) prolonged persistence of LSCs post-chemotherapy without disruption of normal haematopoiesis, aligning with clinical observations of dormant AML clones; (iv) early LSC dynamics post-induction chemotherapy, characterized by stochastic behaviours and movement velocities, are insufficient predictors of long-term prognosis; and (v) a distinct spatiotemporal organization of LSCs in later phases post-induction chemotherapy is correlated with long-term outcomes. Our modelling results provide a theoretical and clinical framework for AML research, and future clinical data validation could refine the utility of CA modelling for oncological studies.

Advances in DNA/RNA Sequencing and Their Applications in Acute Myeloid Leukemia (AML)

Acute myeloid leukemia (AML) is an aggressive malignancy that poses significant challenges due to high rates of relapse and resistance to treatment, particularly in older populations. While therapeutic advances have been made, survival outcomes remain suboptimal. The evolution of DNA and RNA sequencing technologies, including whole-genome sequencing (WGS), whole-exome sequencing (WES), and RNA sequencing (RNA-Seq), has significantly enhanced our understanding of AML at the molecular level. These technologies have led to the discovery of driver mutations and transcriptomic alterations critical for improving diagnosis, prognosis, and personalized therapy development. Furthermore, single-cell RNA sequencing (scRNA-Seq) has uncovered rare subpopulations of leukemia stem cells (LSCs) contributing to disease progression and relapse. However, widespread clinical integration of these tools remains limited by costs, data complexity, and ethical challenges. This review explores recent advancements in DNA/RNA sequencing in AML and highlights both the potential and limitations of these techniques in clinical practice.

Siglec15 in blood system diseases: from bench to bedside

Inhibiting the PD-1/PD-L1 pathway using immunomodulators has demonstrated promising outcomes in clinics. Immunomodulators can effectively target immune checkpoints with a strong preference for the tumor microenvironment (TME). Besides, immunomodulators specifically target the recently discovered inhibitory immune checkpoint, sialic acid-binding immunoglobulin-like lectin (Siglec-15). Distinctive in its molecular composition, Siglec-15 has a unique molecular composition and been shown to be highly prevalent in numerous solid tumor tissues and tumor-associated macrophages (TAMs) in human subjects. Notably, Siglec-15 is up-regulated across various cancer types. As a result, Siglec-15 has attracted significant attention due to its exclusive nature concerning PD-L1 expression, suggesting its role in immune evasion in patients lacking PD-L1. Siglec-15 predominantly appears in certain populations and can promote tumor development by repressing T lymphocyte activation and proliferation, thereby facilitating tumor cell immune escape. Furthermore, Siglec-15 is implicated in osteoclast differentiation and bone remodeling, indicating that it is a promising target for next-generation cancer immunotherapies. Additionally, Siglec-15 can modulate immune responses to microbial infections. The current treatment strategies for hematological conditions predominantly include conventional intensive chemotherapy and transplantation methods. However, emerging immunotherapeutic approaches are increasingly recognized for their overall effectiveness, indicating that specific molecular targets should be identified. The expression of Siglec-15 within tumor cells may indicate a novel pathway for treating hematological malignancies. In this study, the biological attributes, expression patterns, and pathogenic mechanisms of Siglec-15 across various diseases were reviewed. The role of Siglec-15 in the pathogenesis and laboratory diagnosis of hematological disorders was also evaluated.

CX43-mediated mitochondrial transfer maintains stemness of KG-1a leukemia stem cells through metabolic remodeling

BACKGROUND

Acute myeloid leukemia (AML) is characterized by abundant immature myeloid cells, relapse and refractory due to leukemia stem cells (LSCs). Bone marrow mesenchymal stem/ stromal cells (BMSCs) supported LSCs survival, meanwhile, chemotherapy improved connexin43 (CX43) expression. CX43, as the most intercellular gap junction, facilitated transmit mitochondria from BMSCs into AML. We hypothesized that increased mitochondria transferred from BMSCs supported metabolic remodeling in LSCs to sustain their stemness.

METHODS

Primary BMSCs from AML patients were isolated. CX43-BMSCs, overexpressing CX43, were cocultured with KG-1a cells. Fluorescence and confocal microscopy observed mitochondrial transfer. Flow cytometry, EdU assay, and clonogenicity evaluated cell cycle, proliferation, and clonogenic potential. Xenograft mouse models were used to evaluate the tumorigenicity of KG-1a in vivo. Seahorse, RNA-seq, and LC-MS assessed mitochondrial function, transcriptomes, and metabolites post-coculture.

RESULTS

CX43-BMSCs promoted unidirectional mitochondrial transfer, enhancing KG-1a adhesion and proliferation to maintain LSCs stemness in vitro and vivo. RNA-seq revealed coculture with CX43-BMSCs upregulated genes related to adhesion, proliferation, and migration in KG-1a cells. Elevated CX43 expression strengthened BMSCs-KG-1a interaction, facilitating mitochondrial transfer and nucleoside metabolism, fueling KG-1a cells. This enhanced mitochondrial energy metabolism, promoting metabolic reprogramming and clonogenicity.

CONCLUSION

CX43-mediated mitochondrial transfer from BMSCs to KG-1a enhances LSCs adhesion, proliferation, clonogenicity, and metabolic reprogramming. CX43 emerges as a potential therapeutic target for AML by sustaining LSCs stemness through metabolic remodeling.

NAT10-mediated mRNA N4-acetylcytidine reprograms serine metabolism to drive leukaemogenesis and stemness in acute myeloid leukaemia

RNA modification has emerged as an important epigenetic mechanism that controls abnormal metabolism and growth in acute myeloid leukaemia (AML). However, the roles of RNA N4-acetylcytidine (ac4C) modification in AML remain elusive. Here, we report that ac4C and its catalytic enzyme NAT10 drive leukaemogenesis and sustain self-renewal of leukaemic stem cells/leukaemia-initiating cells through reprogramming serine metabolism. Mechanistically, NAT10 facilitates exogenous serine uptake and de novo biosynthesis through ac4C-mediated translation enhancement of the serine transporter SLC1A4 and the transcription regulators HOXA9 and MENIN that activate transcription of serine synthesis pathway genes. We further characterize fludarabine as an inhibitor of NAT10 and demonstrate that pharmacological inhibition of NAT10 targets serine metabolic vulnerability, triggering substantial anti-leukaemia effects both in vitro and in vivo. Collectively, our study demonstrates the functional importance of ac4C and NAT10 in metabolism control and leukaemogenesis, providing insights into the potential of targeting NAT10 for AML therapy.

Retracted article: MYCN contributes to the sensitization of acute myelogenous leukemia cells to cisplatin by targeting SRY-box transcription factor 4

Xianbao Huang, Ling Qi, Wei Lu, Ziye Li, Wuping Li and Fei Li. MYCN contributes to the sensitization of acute myelogenous leukemia cells to cisplatin by targeting SRY-box transcription factor 4. Bioengineered. 2021 Oct. doi: 10.1080/21655979.2021.1997697.Since publication, significant concerns have been raised about the compliance with ethical policies for human research and the integrity of the data reported in the article.When approached for an explanation, the authors provided some original data but were not able to provide all the necessary supporting information. As verifying the validity of published work is core to the scholarly record's integrity, we are retracting the article. All authors listed in this publication have been informed.We have been informed in our decision-making by our editorial policies and the COPE guidelines.The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as 'Retracted.'

A new era of functional experimentation in human hematopoiesis and leukemia research

Functional experimentation has laid the foundation for our understanding of hematopoietic and leukemic stem cells. Yet, most recently, a flurry of descriptive studies of primary human cells, fueled by rapid technological advances in sequencing technologies, have emerged. These increasing opportunities to describe at great detail have taken precedence over rigorously interrogating functional mediators of biology, particularly in primary human cells. Here, we argue that an improved toolset of gene editing and stem cell biology technologies will allow the field to expand beyond extensive descriptive studies to more functional studies.

IL-21/IL-21R signaling renders acute myeloid leukemia stem cells more susceptible to cytarabine treatment and CAR T cell therapy

Self-renewal programs in leukemia stem cells (LSCs) predict poor prognosis in patients with acute myeloid leukemia (AML). We identify CD4+ T cell-derived interleukin (IL)-21 as an important negative regulator of self-renewal of LSCs. IL-21/IL-21R signaling favors asymmetric cell division and differentiation in LSCs through the activation of p38-MAPK signaling, resulting in reduced LSC numbers and significantly prolonged survival in murine AML models. In human AML, serum IL-21 at diagnosis is identified as an independent positive prognostic biomarker for outcome and correlates with improved survival and higher complete remission rates in patients that underwent high-dose chemotherapy. IL-21 treatment inhibits primary LSC function and enhances the effect of cytarabine and CD70 CAR T cell treatment on LSCs in vitro. Low-dose IL-21 treatment prolongs the survival of AML mice in syngeneic and xenograft experiments. Therefore, promoting IL-21/IL-21R signaling on LSCs may be an approach to reduce stemness and increase differentiation in AML.

Single-cell transcriptional mapping reveals genetic and non-genetic determinants of aberrant differentiation in AML

In acute myeloid leukemia (AML), genetic mutations distort hematopoietic differentiation, resulting in the accumulation of leukemic blasts. Yet, it remains unclear how these mutations intersect with cellular origins and whether they converge upon similar differentiation patterns. Single-cell RNA sequencing (scRNA-seq) has enabled high-resolution mapping of the relationship between leukemia and normal cell states, yet this application is hampered by imprecise reference maps of normal hematopoiesis and small sample sizes among patient cohorts. As a first step we constructed a reference atlas of human bone marrow hematopoiesis from 263,519 single-cell transcriptomes spanning 55 cellular states, that was benchmarked against independent datasets of immunophenotypically pure hematopoietic stem and progenitor cells. Using this reference atlas, we mapped over 1.2 million single-cell transcriptomes spanning 318 AML, mixed phenotype acute leukemia (MPAL), and acute erythroid leukemia (AEL) samples. This large-scale analysis, together with systematic mapping of genotype-to-phenotype associations between driver mutations and differentiation landscapes, revealed convergence of diverse genetic alterations on twelve recurrent patterns of aberrant differentiation in AML. This included unconventional lymphoid and erythroid priming linked to RUNX1 and TP53 mutations, respectively. We also identified non-genetic determinants of AML differentiation such as two subgroups of KMT2A-rearranged AML that differ in the identity of their leukemic stem cells (LSCs), likely reflecting distinct cellular origins. Furthermore, distinct LSC-driven hierarchies can co-exist within individual patients, providing insights into AML evolution. Together, precise mapping of normal and malignant cell states provides a framework for advancing the study and disease classification of hematologic malignancies thereby informing therapy development.

Relationship between adipocytes and hematological tumors in the bone marrow microenvironment: a literature review

Background and Objective

The bone marrow microenvironment is closely related to normal hematopoiesis and hematologic tumors. Adipocytes are an important part of the bone marrow microenvironment, in which they can release free fatty acids (FFAs) through lipolysis and secrete adipocytokines, etc., and participate in normal hematopoiesis, which is closely related to the occurrence and treatment of hematological tumors. In this review, we aim to discuss how bone marrow adipocytes (BMAs) can influence the proliferation, apoptosis, and chemotherapy resistance of cancer cells by reprogramming lipid metabolism and the secretion of various adipocytokines.

Methods

Studies from 2000 to July 2024 were reviewed from PubMed, Springer Link, and the Web of Science using the keywords bone marrow microenvironment, adipocytes, lipid metabolism, adipocytokines, hematological tumor, cancer, and their combinations. Unreliable articles such as those that are old and have a low impact factor are excluded, and there is no restriction on language.

Key Content and Findings

Adipocytes can regulate the proliferation and differentiation of hematopoietic stem cells (HSCs) by secreting inflammatory factors and adipocytokines to maintain hematopoietic homeostasis. Adipocytes can also stimulate and accelerate the occurrence and progression of hematological tumors by secreting adipocytokines and mediating the reprogramming of lipid metabolism. Moreover, abundant adipocytes in bone marrow can protect tumor cells by physically blocking and/or secreting cytokines, leading to chemotherapy resistance.

Conclusions

Therefore, the targeted inhibition of related lipid metabolism pathways and adipocytokines might be a potential therapeutic target for hematological tumors, which would be helpful to inhibit tumor growth and correct chemotherapy resistance.

DNMT3AR882H Is Not Required for Disease Maintenance in Primary Human AML, but Is Associated With Increased Leukemia Stem Cell Frequency

Genetic mutations are being thoroughly mapped in human cancers, yet a fundamental question in cancer biology is whether such mutations are functionally required for cancer initiation, maintenance of established cancer, or both. Here, we study this question in the context of human acute myeloid leukemia (AML), where DNMT3A R882 missense mutations often arise early, in pre-leukemic clonal hematopoiesis, and corrupt the DNA methylation landscape to initiate leukemia. We developed CRISPR-based methods to directly correct DNMT3A R882 mutations in leukemic cells obtained from patients. Surprisingly, DNMT3A R882 mutations were largely dispensable for disease maintenance. Replacing DNMT3A R882 mutants with wild-type DNMT3A did not impair the ability of AML cells to engraft in vivo, and minimally altered DNA methylation. Taken together, DNMT3A R882 mutations are initially necessary for AML initiation, but are largely dispensable for disease maintenance. The notion that initiating oncogenes differ from those that maintain cancer has important implications for cancer evolution and therapy.

Single-cell dissection reveals promotive role of ENO1 in leukemia stem cell self-renewal and chemoresistance in acute myeloid leukemia

BACKGROUND

Quiescent self-renewal of leukemia stem cells (LSCs) and resistance to conventional chemotherapy are the main factors leading to relapse of acute myeloid leukemia (AML). Alpha-enolase (ENO1), a key glycolytic enzyme, has been shown to regulate embryonic stem cell differentiation and promote self-renewal and malignant phenotypes in various cancer stem cells. Here, we sought to test whether and how ENO1 influences LSCs renewal and chemoresistance within the context of AML.

METHODS

We analyzed single-cell RNA sequencing data from bone marrow samples of 8 relapsed/refractory AML patients and 4 healthy controls using bioinformatics and machine learning algorithms. In addition, we compared ENO1 expression levels in the AML cohort with those in 37 control subjects and conducted survival analyses to correlate ENO1 expression with clinical outcomes. Furthermore, we performed functional studies involving ENO1 knockdown and inhibition in AML cell line.

RESULTS

We used machine learning to model and infer malignant cells in AML, finding more primitive malignant cells in the non-response (NR) group. The differentiation capacity of LSCs and progenitor malignant cells exhibited an inverse correlation with glycolysis levels. Trajectory analysis indicated delayed myeloid cell differentiation in NR group, with high ENO1-expressing LSCs at the initial stages of differentiation being preserved post-treatment. Simultaneously, ENO1 and stemness-related genes were upregulated and co-expressed in malignant cells during early differentiation. ENO1 level in our AML cohort was significantly higher than the controls, with higher levels in NR compared to those in complete remission. Knockdown of ENO1 in AML cell line resulted in the activation of LSCs, promoting cell differentiation and apoptosis, and inhibited proliferation. ENO1 inhibitor can impede the proliferation of AML cells. Furthermore, survival analyses associated higher ENO1 expression with poorer outcome in AML patients.

CONCLUSIONS

Our findings underscore the critical role of ENO1 as a plausible driver of LSC self-renewal, a potential target for AML target therapy and a biomarker for AML prognosis.

Identification of leukemia stem cell subsets with distinct transcriptional, epigenetic and functional properties

The leukemia stem cell (LSC) compartment is a complex reservoir fueling disease progression in acute myeloid leukemia (AML). The existence of heterogeneity within this compartment is well documented but prior studies have focused on genetic heterogeneity without being able to address functional heterogeneity. Understanding this heterogeneity is critical for the informed design of therapies targeting LSC, but has been hampered by LSC scarcity and the lack of reliable cell surface markers for viable LSC isolation. To overcome these challenges, we turned to the patient-derived OCI-AML22 cell model. This model includes functionally, transcriptionally and epigenetically characterized LSC broadly representative of LSC found in primary AML samples. Focusing on the pool of LSC, we used an integrated approach combining xenograft assays with single-cell analysis to identify two LSC subtypes with distinct transcriptional, epigenetic and functional properties. These LSC subtypes differed in depth of quiescence, differentiation potential, repopulation capacity, sensitivity to chemotherapy and could be isolated based on CD112 expression. A majority of AML patient samples had transcriptional signatures reflective of either LSC subtype, and some even showed coexistence within an individual sample. This work provides a framework for investigating the LSC compartment and designing combinatorial therapeutic strategies in AML.

Sphingosine-1 phosphate receptor 1 (S1PR1) expression maintains stemness of acute myeloid leukemia stem cells

Acute myeloid leukemia (AML) arises from leukemia stem cells (LSCs) and is maintained by cells which have acquired features of stemness. We compared transcription profiles of AML cells with/without stem cell features defined as in vitro clonogenicity and serial engraftment in immune-deficient mice xenograft model. We used multi-parameter flow cytometry (MPFC) to separate CD34+ bone marrow-derived leukemia cells into sphingosine-1 phosphate receptor 1 (S1PR1)+ and S1PR1- fractions. Cells in the S1PR1+ fraction demonstrated significantly higher clonogenicity and higher engraftment potential compared with those in the S1PR1- fraction. In contrast, CD34+ bone marrow cells from normal samples showed reduced clonogenicity in the S1PR1+ fraction compared with the S1PR1- fraction. Inhibition of S1PR1 expression in an AML cell line reduced the colony-forming potential of KG1 cells. Transcriptomic analyses and rescue experiments indicated PI3K/AKT pathway and MYBL2 are downstream mediators of S1PR1-associated stemness. These findings implicate S1PR1 as a functional biomarker of LSCs and suggest its potential as a therapeutic target in AML treatment.

DOGMA-seq and multimodal, single-cell analysis in acute myeloid leukemia

Acute myeloid leukemia (AML) is a complex cancer, yet advances in recent years from integrated genomics methods have helped improve diagnosis, treatment, and means of patient stratification. A recent example of a powerful, multimodal method is DOGMA-seq, which can measure chromatin accessibility, gene expression, and cell-surface protein levels from the same individual cell simultaneously. Previous bimodal single-cell techniques, such as CITE-seq (Cellular indexing of transcriptomes and epitopes), have only permitted the transcriptome and cell-surface protein expression measurement. DOGMA-seq, however, builds on this foundation and has implications for examining epigenomic, transcriptomic, and proteomic interactions between various cell types. This technique has the potential to be particularly useful in the study of cancers such as AML. This is because the cellular mechanisms that drive AML are rather heterogeneous and require a more complete understanding of the interplay between the genetic mutations, disruptions in RNA transcription and translation, and surface protein expression that cause these cancers to develop and evolve. This technique will hopefully contribute to a more clear and complete understanding of the growth and progression of complex cancers.

Targeting the redox vulnerability of acute myeloid leukaemia cells with a combination of auranofin and vitamin C

Acute myeloid leukaemia (AML) is a heterogeneous disease characterized by complex molecular and cytogenetic abnormalities. Pro-oxidant cellular redox status is a common hallmark of AML cells, providing a rationale for redox-based anticancer strategy. We previously discovered that auranofin (AUF), initially used for the treatment of rheumatoid arthritis and repositioned for its anticancer activity, can synergize with a pharmacological concentration of vitamin C (VC) against breast cancer cell line models. In this study, we observed that this drug combination synergistically and efficiently killed cells of leukaemic cell lines established from different myeloid subtypes. In addition to an induced elevation of reactive oxygen species and ATP depletion, a rapid dephosphorylation of 4E-BP1 and p70S6K, together with a strong inhibition of protein synthesis were early events in response to AUF/VC treatment, suggesting their implication in AUF/VC-induced cytotoxicity. Importantly, a study on 22 primary AML specimens from various AML subtypes showed that AUF/VC combinations at pharmacologically achievable concentrations were effective to eradicate primary leukaemic CD34+ cells from the majority of these samples, while being less toxic to normal cord blood CD34+ cells. Our findings indicate that targeting the redox vulnerability of AML with AUF/VC combinations could present a potential anti-AML therapeutic approach.

SMARCA5 reprograms AKR1B1-mediated fructose metabolism to control leukemogenesis

A significant variation in chromatin accessibility is an epigenetic feature of leukemia. The cause of this variation in leukemia, however, remains elusive. Here, we identify SMARCA5, a core ATPase of the imitation switch (ISWI) chromatin remodeling complex, as being responsible for aberrant chromatin accessibility in leukemia cells. We find that SMARCA5 is required to maintain aberrant chromatin accessibility for leukemogenesis and then promotes transcriptional activation of AKR1B1, an aldo/keto reductase, by recruiting transcription co-activator DDX5 and transcription factor SP1. Higher levels of AKR1B1 are associated with a poor prognosis in leukemia patients and promote leukemogenesis by reprogramming fructose metabolism. Moreover, pharmacological inhibition of AKR1B1 has been shown to have significant therapeutic effects in leukemia mice and leukemia patient cells. Thus, our findings link the aberrant chromatin state mediated by SMARCA5 to AKR1B1-mediated endogenous fructose metabolism reprogramming and shed light on the essential role of AKR1B1 in leukemogenesis, which may provide therapeutic strategies for leukemia.

Activation of non-classical Wnt signaling pathway effectively enhances HLA-A presentation in acute myeloid leukemia

Objective

The escape from T cell-mediated immune surveillance is an important cause of death for patients with acute myeloid leukemia (AML). This study aims to identify clonal heterogeneity in leukemia progenitor cells and explore molecular or signaling pathways associated with AML immune escape.

Methods

Single-cell RNA sequencing (scRNA-seq) was performed to identified AML-related cellular subsets, and intercellular communication was analyzed to investigate molecular mechanisms associated with AML immune escape. Bulk RNA sequencing (RNA-seq) was performed to screen differentially expressed genes (DEGs) related to hematopoietic stem cell progenitors (HSC-Prog) in AML, and critical ore signaling pathways and hub genes were found by Gene Set Enrichment Analysis (GSEA), Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. The mRNA level of the hub gene was verified using quantitative real-time PCR (qRT-PCR) and the protein level of human leukocyte antigen A (HLA-A) using enzyme-linked immuno sorbent assay (ELISA).

Results

scRNA-seq analysis revealed a large heterogeneity of HSC-Prog across samples, and the intercellular communication analysis indicated a strong association between HSC-Prog and CD8+-T cells, and HSC-Prog also had an association with HLA-A. Transcriptome analysis identified 1748 DEGs, enrichment analysis results showed that non-classical wnt signaling pathway was associated with AML, and 4 pathway-related genes (RHOA, RYK, CSNK1D, NLK) were obtained. After qRT-PCR and ELISA validation, hub genes and HLA-A were found to be down-regulated in AML and up-regulated after activation of the non-classical Wnt signaling pathway.

Conclusion

In this study, clonal heterogeneity of HSC-Prog cells in AML was identified, non-classical wnt signaling pathways associated with AML were identified, and it was verified that HLA-A could be upregulated by activation of non-classical wnt signaling, thereby increasing antigen presentation.

CD37 is a safe chimeric antigen receptor target to treat acute myeloid leukemia

Acute myeloid leukemia (AML) is characterized by the accumulation of immature myeloid cells in the bone marrow and the peripheral blood. Nearly half of the AML patients relapse after standard induction therapy, and new forms of therapy are urgently needed. Chimeric antigen receptor (CAR) T therapy has so far not been successful in AML due to lack of efficacy and safety. Indeed, the most attractive antigen targets are stem cell markers such as CD33 or CD123. We demonstrate that CD37, a mature B cell marker, is expressed in AML samples, and its presence correlates with the European LeukemiaNet (ELN) 2017 risk stratification. We repurpose the anti-lymphoma CD37CAR for the treatment of AML and show that CD37CAR T cells specifically kill AML cells, secrete proinflammatory cytokines, and control cancer progression in vivo. Importantly, CD37CAR T cells display no toxicity toward hematopoietic stem cells. Thus, CD37 is a promising and safe CAR T cell AML target.

The Study of SRSF1 Regulates Abnormal Alternative Splicing of BCL2L11 and the Role in Refractory Acute Myeloid Leukemia

INTRODUCTION

Abnormalities in splicing factors, such as mutations or deregulated expression, can lead to aberrant splicing of target genes, potentially contributing to the pathogenesis of acute myeloid leukemia (AML). Despite this, the precise mechanism underlying the abnormal alternative splicing (AS) induced by SRSF1, a splicing factor associated with poor AML prognosis, remains elusive.

METHODS

Using strict splicing criteria, we globally screened for AS events in NPMc-positive and NPMc-negative AML samples from TCGA. An AS network associated with AML prognosis was then established. Functional assays, including CCK-8, flow cytometry, and Western blot, were conducted on K562 and THP-1 cells overexpressing SRSF1. Cell viability following 72-h Omipalisib treatment was also assessed. To explore the mechanism of SRSF1-induced AS, we created a BCL2L11 miniGene with a site-specific mutation at its branch point. The AS patterns of both wild-type and mutant miniGenes were analyzed following SRSF1 overexpression in HEK-293T, along with the subcellular localization of different spliceosomes.

RESULTS

SRSF1 was significantly associated with AML prognosis. Notably, its expression was markedly upregulated in refractory AML patients compared to those with a favorable chemotherapy response. Overexpression of SRSF1 promoted THP-1 cell proliferation, suppressed apoptosis, and reduced sensitivity to Omipalisib. Mechanistically, SRSF1 recognized an aberrant branch point within the BCL2L11 intron, promoting the inclusion of a cryptic exon 3, which in turn led to apoptosis arrest.

CONCLUSION

Overexpression of SRSF1 and the resulting abnormal splicing of BCL2L11 are associated with drug resistance and poor prognosis in AML.

Venetoclax therapy and emerging resistance mechanisms in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a highly aggressive and devastating malignancy of the bone marrow and blood. For decades, intensive chemotherapy has been the frontline treatment for AML but has yielded only poor patient outcomes as exemplified by a 5-year survival rate of < 30%, even in younger adults. As knowledge of the molecular underpinnings of AML has advanced, so too has the development new strategies with potential to improve the treatment of AML patients. To date the most promising of these targeted agents is the BH3-mimetic venetoclax which in combination with standard of care therapies, has manageable non-haematological toxicity and exhibits impressive efficacy. However, approximately 30% of AML patients fail to respond to venetoclax-based regimens and almost all treatment responders eventually relapse. Here, we review the emerging mechanisms of intrinsic and acquired venetoclax resistance in AML and highlight recent efforts to identify novel strategies to overcome resistance to venetoclax.

Imaging Flow Cytometry and Convolutional Neural Network-Based Classification Enable Discrimination of Hematopoietic and Leukemic Stem Cells in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogenous blood cancer with a dismal prognosis. It emanates from leukemic stem cells (LSCs) arising from the genetic transformation of hematopoietic stem cells (HSCs). LSCs hold prognostic value, but their molecular and immunophenotypic heterogeneity poses challenges: there is no single marker for identifying all LSCs across AML samples. We hypothesized that imaging flow cytometry (IFC) paired with artificial intelligence-driven image analysis could visually distinguish LSCs from HSCs based solely on morphology. Initially, a seven-color IFC panel was employed to immunophenotypically identify LSCs and HSCs in bone marrow samples from five AML patients and ten healthy donors, respectively. Next, we developed convolutional neural network (CNN) models for HSC-LSC discrimination using brightfield (BF), side scatter (SSC), and DNA images. Classification using only BF images achieved 86.96% accuracy, indicating significant morphological differences. Accuracy increased to 93.42% when combining BF with DNA images, highlighting differences in nuclear morphology, although DNA images alone were inadequate for accurate HSC-LSC discrimination. Model development using SSC images revealed minor granularity differences. Performance metrics varied substantially between AML patients, indicating considerable morphologic variations among LSCs. Overall, we demonstrate proof-of-concept results for accurate CNN-based HSC-LSC differentiation, instigating the development of a novel technique within AML monitoring.

Immunophenotypic clustering in paediatric acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a highly heterogeneous disease, exhibiting diverse subtypes according to the characteristics of tumour cells. The immunophenotype is one of the aspects acquired routinely through flow cytometry in the diagnosis of AML. Here, we characterized the antigen expression in paediatric AML cases across both morphological and molecular genetic subgroups. We discovered a subgroup of patients with unfavourable prognosis that can be immunologically characterized, irrespective of morphological FAB results or genetic aberrations. Cox regression analysis unveiled key antigens influencing the prognosis of AML patients. In terms of underlying genotypes, we observed that the antigenic profiles and outcomes of one specific group, primarily composed of CBFA2T3::GLIS2 and FUS::ERG, were analogous to the reported RAM phenotype. Overall, our data highlight the significance of immunophenotype to tailor treatment for paediatric AML.

Chimeric antigen receptor T-cell therapy in childhood acute myeloid leukemia: how far are we from a clinical application?

Recurrent and/or refractory (R/R) pediatric acute myeloid leukemia (AML) remains a recalcitrant disease with poor outcomes. Cell therapy with genetically modified immune effector cells holds the promise to improve outcomes for R/R AML since it relies on cytotoxic mechanisms that are distinct from chemotherapeutic agents. While T cells expressing chimeric antigen receptors (CAR T cells) showed significant anti-AML activity in preclinical models, early phase clinical studies have demonstrated limited activity, irrespective of the targeted AML antigen. Lack of efficacy is most likely multifactorial, including: (i) a limited array of AML-specific targets and target antigen heterogeneity; (ii) the aggressive nature of R/R AML and heavy pretreatment of patients; (iii) T-cell product manufacturing, and (iv) limited expansion and persistence of the CAR T cells, which is in part driven by the immunosuppressive AML microenvironment. Here we review the results of early phase clinical studies with AML-specific CAR T cells, and avenues investigators are exploring to improve their effector function.

BRG1/BRM inhibitor targets AML stem cells and exerts superior preclinical efficacy combined with BET or menin inhibitor

ABSTRACT

BRG1 (SMARCA4) and BRM (SMARCA2) are the mutually exclusive core ATPases of the chromatin remodeling BAF (BRG1/BRM-associated factor) complexes. They enable transcription factors/cofactors to access enhancers/promoter and modulate gene expressions responsible for cell growth and differentiation of acute myeloid leukemia (AML) stem/progenitor cells. In AML with MLL1 rearrangement (MLL1r) or mutant NPM1 (mtNPM1), although menin inhibitor (MI) treatment induces clinical remissions, most patients either fail to respond or relapse, some harboring menin mutations. FHD-286 is an orally bioavailable, selective inhibitor of BRG1/BRM under clinical development in AML. Present studies show that FHD-286 induces differentiation and lethality in AML cells with MLL1r or mtNPM1, concomitantly causing perturbed chromatin accessibility and repression of c-Myc, PU.1, and CDK4/6. Cotreatment with FHD-286 and decitabine, BET inhibitor (BETi) or MI, or venetoclax synergistically induced in vitro lethality in AML cells with MLL1r or mtNPM1. In models of xenografts derived from patients with AML with MLL1r or mtNPM1, FHD-286 treatment reduced AML burden, improved survival, and attenuated AML-initiating potential of stem-progenitor cells. Compared with each drug, cotreatment with FHD-286 and BETi, MI, decitabine, or venetoclax significantly reduced AML burden and improved survival, without inducing significant toxicity. These findings highlight the FHD-286-based combinations as a promising therapy for AML with MLL1r or mtNPM1.

PI3Kγ maintains the self-renewal of acute myeloid leukemia stem cells by regulating the pentose phosphate pathway

ABSTRACT

Acute myeloid leukemia (AML) is an aggressive hematological malignancy originating from transformed hematopoietic stem or progenitor cells. AML prognosis remains poor owing to resistance and relapse driven by leukemia stem cells (LSCs). Targeting molecules essential for LSC function is a promising therapeutic approach. The phosphatidylinositol 3-kinase (PI3K)/AKT pathway is often dysregulated in AML. We found that although PI3Kγ is highly enriched in LSCs and critical for self-renewal, it was dispensable for normal hematopoietic stem cells. Mechanistically, PI3Kγ-AKT signaling promotes nuclear factor erythroid 2-related factor 2 (NRF2) nuclear accumulation, which induces 6-phosphogluconate dehydrogenase (PGD) and the pentose phosphate pathway, thereby maintaining LSC stemness. Importantly, genetic or pharmacological inhibition of PI3Kγ impaired expansion and stemness of murine and human AML cells in vitro and in vivo. Together, our findings reveal a key role for PI3Kγ in selectively maintaining LSC function by regulating AKT-NRF2-PGD metabolic pathway. Targeting the PI3Kγ pathway may, therefore, eliminate LSCs without damaging normal hematopoiesis, providing a promising therapeutic strategy for AML.

Pyrimidine depletion enhances targeted and immune therapy combinations in acute myeloid leukemia

Acute myeloid leukemia (AML) is a fatal disease characterized by the accumulation of undifferentiated myeloblasts, and agents that promote differentiation have been effective in this disease but are not curative. Dihydroorotate dehydrogenase inhibitors (DHODHi) have the ability to promote AML differentiation and target aberrant malignant myelopoiesis. We introduce HOSU-53, a DHODHi with significant monotherapy activity, which is further enhanced when combined with other standard-of-care therapeutics. We further discovered that DHODHi modulated surface expression of CD38 and CD47, prompting the evaluation of HOSU-53 combined with anti-CD38 and anti-CD47 therapies, where we identified a compelling curative potential in an aggressive AML model with CD47 targeting. Finally, we explored using plasma dihydroorotate (DHO) levels to monitor HOSU-53 safety and found that the level of DHO accumulation could predict HOSU-53 intolerability, suggesting the clinical use of plasma DHO to determine safe DHODHi doses. Collectively, our data support the clinical translation of HOSU-53 in AML, particularly to augment immune therapies. Potent DHODHi to date have been limited by their therapeutic index; however, we introduce pharmacodynamic monitoring to predict tolerability while preserving antitumor activity. We additionally suggest that DHODHi is effective at lower doses with select immune therapies, widening the therapeutic index.

Convergent epigenetic evolution drives relapse in acute myeloid leukemia

Relapse of acute myeloid leukemia (AML) is highly aggressive and often treatment refractory. We analyzed previously published AML relapse cohorts and found that 40% of relapses occur without changes in driver mutations, suggesting that non-genetic mechanisms drive relapse in a large proportion of cases. We therefore characterized epigenetic patterns of AML relapse using 26 matched diagnosis-relapse samples with ATAC-seq. This analysis identified a relapse-specific chromatin accessibility signature for mutationally stable AML, suggesting that AML undergoes epigenetic evolution at relapse independent of mutational changes. Analysis of leukemia stem cell (LSC) chromatin changes at relapse indicated that this leukemic compartment underwent significantly less epigenetic evolution than non-LSCs, while epigenetic changes in non-LSCs reflected overall evolution of the bulk leukemia. Finally, we used single-cell ATAC-seq paired with mitochondrial sequencing (mtscATAC) to map clones from diagnosis into relapse along with their epigenetic features. We found that distinct mitochondrially-defined clones exhibit more similar chromatin accessibility at relapse relative to diagnosis, demonstrating convergent epigenetic evolution in relapsed AML. These results demonstrate that epigenetic evolution is a feature of relapsed AML and that convergent epigenetic evolution can occur following treatment with induction chemotherapy.

A CD38-directed, single-chain T-cell engager targets leukemia stem cells through IFN-γ-induced CD38 expression

Treatment resistance of leukemia stem cells (LSCs) and suppression of the autologous immune system represent major challenges to achieve a cure in acute myeloid leukemia (AML). Although AML blasts generally retain high levels of surface CD38 (CD38pos), LSCs are frequently enriched in the CD34posCD38neg blast fraction. Here, we report that interferon gamma (IFN-γ) reduces LSCs clonogenic activity and induces CD38 upregulation in both CD38pos and CD38neg LSC-enriched blasts. IFN-γ-induced CD38 upregulation depends on interferon regulatory factor 1 transcriptional activation of the CD38 promoter. To leverage this observation, we created a novel compact, single-chain CD38-CD3 T-cell engager (BN-CD38) designed to promote an effective immunological synapse between CD38pos AML cells and both CD8pos and CD4pos T cells. We demonstrate that BN-CD38 engages autologous CD4pos and CD8pos T cells and CD38pos AML blasts, leading to T-cell activation and expansion and to the elimination of leukemia cells in an autologous setting. Importantly, BN-CD38 engagement induces the release of high levels of IFN-γ, driving the expression of CD38 on CD34posCD38neg LSC-enriched blasts and their subsequent elimination. Critically, although BN-CD38 showed significant in vivo efficacy across multiple disseminated AML cell lines and patient-derived xenograft models, it did not affect normal hematopoietic stem cell clonogenicity and the development of multilineage human immune cells in CD34pos humanized mice. Taken together, this study provides important insights to target and eliminate AML LSCs.

Pursuing dynamics of minimal residual leukemic subclones in relapsed and refractory acute myeloid leukemia during conventional therapy

BACKGROUND

Acute myeloid leukemia (AML) is characterized by clonal heterogeneity, leading to frequent relapses and drug resistance despite intensive clinical therapy. Although AML's clonal architecture has been addressed in many studies, practical monitoring of dynamic changes in those subclones during relapse and treatment is still understudied.

METHOD

Fifteen longitudinal bone marrow (BM) samples were collected from three relapsed and refractory (R/R) AML patients. Using droplet digital polymerase chain reaction (ddPCR), the frequencies of patient's leukemic variants were assessed in seven cell populations that were isolated from each BM sample based on cellular phenotypes. By quantifying mutant clones at the diagnosis, remission, and relapse stages, the distribution of AML subclones was sequentially monitored.

RESULTS

Minimal residual (MR) leukemic subclones exhibit heterogeneous distribution among BM cell populations, including mature leukocyte populations. During AML progression, these subclones undergo active phenotypic transitions and repopulate into distinct cell population regardless of normal hematopoiesis hierarchic order. Of these, MR subclones in progenitor populations of patient BM predominantly carry MR leukemic properties, leading to more robust expansion and stubborn persistence than those in mature populations. Moreover, a minor subset of MR leukemic subclones could be sustained at an extremely low frequency without clonal expansion during relapse.

CONCLUSIONS

In this study, we observed treatment persistent MR leukemic subclones and their phenotypic changes during the treatment process of R/R AML patients. This underscores the importance of preemptive inhibition of clonal promiscuity in R/R AML, proposing a practical method for monitoring AML MR subclones.

Prognostic insights and immune microenvironment delineation in acute myeloid leukemia by ferroptosis-derived signature

Acute myeloid leukemia (AML) represents as a prevalent and formidable hematological malignancy, characterized by notably low 5-year survival rates. Ferroptosis has been found to be correlated with cancer initiation, therapeutic response, and clinical outcome. Nevertheless, the involvement of Ferroptosis-related genes (FRGs) in AML remains ambiguous. Five independent AML cohorts totaling 1,470 (GSE37642, GSE12417, GSE10358, Beat-AML, and TCGA-AML) patients with clinical information were used to systematically investigated the influence of these FRGs expression on outcome and tumor microenvironment. The integration of these datasets led to the subdivision into training and validation sets. Nineteen FRGs were identified as correlated with the overall survival (OS) of AML patients, primarily enriched in ferroptosis, fatty acid metabolism, and leukemia-related signaling pathways. The prognostic signature, consisting of 11 FRGs, was formulated using LASSO-Cox stepwise regression analysis. Patients with high-risk scores exhibited reduced survival compared to those in the low-risk group. The receiver operating characteristic (ROC) analysis underscored the signature's robust predictive accuracy. The high predictive efficacy was confirmed by both internal and external validation datasets. Leukemia and signaling related to immune regulation were mainly enriched pathways of the differentially expressed genes by comparing high- and low-risk groups. The immune composition deconvolution might indicate an immunosuppressive niche in the high-risk patients. The pRRophetic algorithm exploration unveiled chemical drugs with potentially sensitivity among patients in both groups. Collectively, our study developed a ferroptosis-derived prognostic signature that provides the OS prediction and identifies the immune microenvironment for AML patients on large-scale AML cohorts.

Metabolic instruction of the graft-versus-leukemia immunity

Allogeneic hematopoietic cell transplantation (allo-HCT) is frequently performed to cure hematological malignancies, such as acute myeloid leukemia (AML), through the graft-versus-leukemia (GVL) effect. In this immunological process, donor immune cells eliminate residual cancer cells in the patient and exert tumor control through immunosurveillance. However, GVL failure and subsequent leukemia relapse are frequent and associated with a dismal prognosis. A better understanding of the mechanisms underlying AML immune evasion is essential for developing novel therapeutic strategies to boost the GVL effect. Cellular metabolism has emerged as an essential regulator of survival and cell fate for both cancer and immune cells. Leukemia and T cells utilize specific metabolic programs, including the orchestrated use of glucose, amino acids, and fatty acids, to support their growth and function. Besides regulating cell-intrinsic processes, metabolism shapes the extracellular environment and plays an important role in cell-cell communication. This review focuses on recent advances in the understanding of how metabolism might affect the anti-leukemia immune response. First, we provide a general overview of the mechanisms of immune escape after allo-HCT and an introduction to leukemia and T cell metabolism. Further, we discuss how leukemia and myeloid cell metabolism contribute to an altered microenvironment that impairs T cell function. Next, we review the literature linking metabolic processes in AML cells with their inhibitory checkpoint ligand expression. Finally, we focus on recent findings concerning the role of systemic metabolism in sustained GVL efficacy. While the majority of evidence in the field still stems from basic and preclinical studies, we discuss translational findings and propose further avenues for bridging the gap between bench and bedside.

Efficacy of novel agents against cellular models of familial platelet disorder with myeloid malignancy (FPD-MM)

Germline, mono-allelic mutations in RUNX1 cause familial platelet disorder (RUNX1-FPD) that evolves into myeloid malignancy (FPD-MM): MDS or AML. FPD-MM commonly harbors co-mutations in the second RUNX1 allele and/or other epigenetic regulators. Here we utilized patient-derived (PD) FPD-MM cells and established the first FPD-MM AML cell line (GMR-AML1). GMR-AML1 cells exhibited active super-enhancers of MYB, MYC, BCL2 and CDK6, augmented expressions of c-Myc, c-Myb, EVI1 and PLK1 and surface markers of AML stem cells. In longitudinally studied bone marrow cells from a patient at FPD-MM vs RUNX1-FPD state, we confirmed increased chromatin accessibility and mRNA expressions of MYB, MECOM and BCL2 in FPD-MM cells. GMR-AML1 and PD FPD-MM cells were sensitive to homoharringtonine (HHT or omacetaxine) or mebendazole-induced lethality, associated with repression of c-Myc, EVI1, PLK1, CDK6 and MCL1. Co-treatment with MB and the PLK1 inhibitor volasertib exerted synergistic in vitro lethality in GMR-AML1 cells. In luciferase-expressing GMR-AML1 xenograft model, MB, omacetaxine or volasertib monotherapy, or co-treatment with MB and volasertib, significantly reduced AML burden and improved survival in the immune-depleted mice. These findings highlight the molecular features of FPD-MM progression and demonstrate HHT, MB and/or volasertib as effective agents against cellular models of FPD-MM.