A 4-gene prognostic index for enhancing acute myeloid leukaemia survival prediction.

Despite advancements in utilizing genetic markers to enhance acute myeloid leukaemia (AML) outcome prediction, significant disease heterogeneity persists, hindering clinical management. To refine survival predictions, we assessed the transcriptome of non-acute promyelocytic leukaemia chemotherapy-treated AML patients from five cohorts (n = 975). This led to the identification of a 4-gene prognostic index (4-PI) comprising CYP2E1, DHCR7, IL2RA and SQLE. The 4-PI effectively stratified patients into risk categories, with the high 4-PI group exhibiting TP53 mutations and cholesterol biosynthesis signatures. Single-cell RNA sequencing revealed enrichment for leukaemia stem cell signatures in high 4-PI cells. Validation across three cohorts (n = 671), including one with childhood AML, demonstrated the reproducibility and clinical utility of the 4-PI, even using cost-effective techniques like real-time quantitative polymerase chain reaction. Comparative analysis with 56 established prognostic indexes revealed the superior performance of the 4-PI, highlighting its potential to enhance AML risk stratification. Finally, the 4-PI demonstrated to be potential marker to reclassified patients from the intermediate ELN2017 category to the adverse category. In conclusion, the 4-PI emerges as a robust and straightforward prognostic tool to improve survival prediction in AML patients.

VISTA drives macrophages towards a pro-tumoral phenotype that promotes cancer cell phagocytosis yet down-regulates T cell responses.

BACKGROUND: VISTA is a well-known immune checkpoint in T cell biology, but its role in innate immunity is less established. Here, we investigated the role of VISTA on anticancer macrophage immunity, with a focus on phagocytosis, macrophage polarization and concomitant T cell activation. METHODS: Macrophages, differentiated from VISTA overexpressed THP-1 cells and cord blood CD34+ cell-derived monocytes, were used in phagocytosis assay using B lymphoma target cells opsonized with Rituximab. PBMC-derived macrophages were used to assess the correlation between phagocytosis and VISTA expression. qRT-PCR, flow cytometry, and enzyme-linked immunosorbent assay were performed to analyze the impact of VISTA on other checkpoints and M1/M2-like macrophage biology. Additionally, flow cytometry was used to assess the frequency of CD14+ monocytes expressing VISTA in PBMCs from 65 lymphoma patients and 37 healthy donors. RESULTS: Ectopic expression of VISTA in the monocytic model cell line THP-1 or in primary monocytes triggered differentiation towards the macrophage lineage, with a marked increase in M2-like macrophage-related gene expression and decrease in M1-like macrophage-related gene expression. VISTA expression in THP-1 and monocyte-derived macrophages strongly downregulated expression of SIRPα, a prominent 'don't eat me' signal, and augmented phagocytic activity of macrophages against cancer cells. Intriguingly, expression of VISTA's extracellular domain alone sufficed to trigger phagocytosis in ∼ 50% of cell lines, with those cell lines also directly binding to recombinant human VISTA, indicating ligand-dependent and -independent mechanisms. Endogenous VISTA expression was predominantly higher in M2-like macrophages compared to M0- or M1-like macrophages, with a positive correlation observed between VISTA expression in M2c macrophages and their phagocytic activity. VISTA-expressing macrophages demonstrated a unique cytokine profile, characterized by reduced IL-1ß and elevated IL-10 secretion. Furthermore, VISTA interacted with MHC-I and downregulated its surface expression, leading to diminished T cell activation. Notably, VISTA surface expression was identified in monocytes from all lymphoma patients but was less prevalent in healthy donors. CONCLUSIONS: Collectively, VISTA expression associates with and drives M2-like activation of macrophages with a high phagocytic capacity yet a decrease in antigen presentation capability to T cells. Therefore, VISTA is a negative immune checkpoint regulator in macrophage-mediated immune suppression.

Unraveling Hematotoxicity of α-Amanitin in Cultured Hematopoietic Cells.

Amanita phalloides poisonings account for the majority of fatal mushroom poisonings. Recently, we identified hematotoxicity as a relevant aspect of Amanita poisonings. In this study, we investigated the effects of the main toxins of Amanita phalloides, α- and ß-amanitin, on hematopoietic cell viability in vitro. Hematopoietic cell lines were exposed to α-amanitin or ß-amanitin for up to 72 h with or without the pan-caspase inhibitor Z-VAD(OH)-FMK, antidotes N-acetylcysteine, silibinin, and benzylpenicillin, and organic anion-transporting polypeptide 1B3 (OATP1B3) inhibitors rifampicin and cyclosporin. Cell viability was established by trypan blue exclusion, annexin V staining, and a MTS assay. Caspase-3/7 activity was determined with Caspase-Glo assay, and cleaved caspase-3 was quantified by Western analysis. Cell number and colony-forming units were quantified after exposure to α-amanitin in primary CD34+ hematopoietic stem cells. In all cell lines, α-amanitin concentration-dependently decreased viability and mitochondrial activity. ß-Amanitin was less toxic, but still significantly reduced viability. α-Amanitin increased caspase-3/7 activity by 2.8-fold and cleaved caspase-3 by 2.3-fold. Z-VAD(OH)-FMK significantly reduced α-amanitin-induced toxicity. In CD34+ stem cells, α-amanitin decreased the number of colonies and cells. The antidotes and OATP1B3 inhibitors did not reverse α-amanitin-induced toxicity. In conclusion, α-amanitin induces apoptosis in hematopoietic cells via a caspase-dependent mechanism.

The nonessential amino acid cysteine is required to prevent ferroptosis in acute myeloid leukemia.

ABSTRACT: Cysteine is a nonessential amino acid required for protein synthesis, the generation of the antioxidant glutathione, and for synthesizing the nonproteinogenic amino acid taurine. Here, we highlight the broad sensitivity of leukemic stem and progenitor cells to cysteine depletion. By CRISPR/CRISPR-associated protein 9-mediated knockout of cystathionine-γ-lyase, the cystathionine-to-cysteine converting enzyme, and by metabolite supplementation studies upstream of cysteine, we functionally prove that cysteine is not synthesized from methionine in acute myeloid leukemia (AML) cells. Therefore, although perhaps nutritionally nonessential, cysteine must be imported for survival of these specific cell types. Depletion of cyst(e)ine increased reactive oxygen species (ROS) levels, and cell death was induced predominantly as a consequence of glutathione deprivation. nicotinamide adenine dinucleotide phosphate hydrogen oxidase inhibition strongly rescued viability after cysteine depletion, highlighting this as an important source of ROS in AML. ROS-induced cell death was mediated via ferroptosis, and inhibition of glutathione peroxidase 4 (GPX4), which functions in reducing lipid peroxides, was also highly toxic. We therefore propose that GPX4 is likely key in mediating the antioxidant activity of glutathione. In line, inhibition of the ROS scavenger thioredoxin reductase with auranofin also impaired cell viability, whereby we find that oxidative phosphorylation-driven AML subtypes, in particular, are highly dependent on thioredoxin-mediated protection against ferroptosis. Although inhibition of the cystine-glutamine antiporter by sulfasalazine was ineffective as a monotherapy, its combination with L-buthionine-sulfoximine (BSO) further improved AML ferroptosis induction. We propose the combination of either sulfasalazine or antioxidant machinery inhibitors along with ROS inducers such as BSO or chemotherapy for further preclinical testing.

Pharmacological Inhibition of PIP4K2 Potentiates Venetoclax-Induced Apoptosis in Acute Myeloid Leukemia.

Phosphatidylinositol-5-phosphate 4-kinase type 2 (PIP4K2) protein family members (PIP4K2A, PIP4K2B, and PIP4K2C) participate in the generation of PIP4,5P2, which acts as a secondary messenger in signal transduction, a substrate for metabolic processes, and has structural functions. In patients with acute myeloid leukemia (AML), high PIP4K2A and PIP4K2C levels are independent markers of a worse prognosis. Recently, our research group reported that THZ-P1-2 (PIP4K2 pan-inhibitor) exhibits anti-leukemic activity by disrupting mitochondrial homeostasis and autophagy in AML models. In the present study, we characterized the expression of PIP4K2 in the myeloid compartment of hematopoietic cells, as well as in AML cell lines and clinical samples with different genetic abnormalities. In ex vivo assays, PIP4K2 expression levels were related to sensitivity and resistance to several antileukemia drugs and highlighted the association between high PIP4K2A levels and resistance to venetoclax. The combination of THZ-P1-2 and venetoclax showed potentiating effects in reducing viability and inducing apoptosis in AML cells. A combined treatment differentially modulated multiple genes, including TAp73, BCL2, MCL1, and BCL2A1. In summary, our study identified the correlation between the expression of PIP4K2 and the response to antineoplastic agents in ex vivo assays in AML and exposed vulnerabilities that may be exploited in combined therapies, which could result in better therapeutic responses.

Signal regulatory protein beta 2 is a novel positive regulator of innate anticancer immunity.

In recent years, the therapeutic (re)activation of innate anticancer immunity has gained prominence, with therapeutic blocking of the interaction of Signal Regulatory Protein (SIRP)-α with its ligand CD47 yielding complete responses in refractory and relapsed B cell lymphoma patients. SIRP-α has as crucial inhibitory role on phagocytes, with e.g., its aberrant activation enabling the escape of cancer cells from immune surveillance. SIRP-α belongs to a family of paired receptors comprised of not only immune-inhibitory, but also putative immune-stimulatory receptors. Here, we report that an as yet uninvestigated SIRP family member, SIRP-beta 2 (SIRP-ß2), is strongly expressed under normal physiological conditions in macrophages and granulocytes at protein level. Endogenous expression of SIRP-ß2 on granulocytes correlated with trogocytosis of cancer cells. Further, ectopic expression of SIRP-ß2 stimulated macrophage adhesion, differentiation and cancer cell phagocytosis as well as potentiated macrophage-mediated activation of T cell Receptor-specific T cell activation. SIRP-ß2 recruited the immune activating adaptor protein DAP12 to positively regulate innate immunity, with the charged lysine 202 of SIRP-ß2 being responsible for interaction with DAP12. Mutation of lysine 202 to leucine lead to a complete loss of the increased adhesion and phagocytosis. In conclusion, SIRP-ß2 is a novel positive regulator of innate anticancer immunity and a potential costimulatory target for innate immunotherapy.

PDP1 is a key metabolic gatekeeper and modulator of drug resistance in FLT3-ITD-positive acute myeloid leukemia.

High metabolic flexibility is pivotal for the persistence and therapy resistance of acute myeloid leukemia (AML). In 20-30% of AML patients, activating mutations of FLT3, specifically FLT3-ITD, are key therapeutic targets. Here, we investigated the influence of FLT3-ITD on AML metabolism. Nuclear Magnetic Resonance (NMR) profiling showed enhanced reshuffling of pyruvate towards the tricarboxylic acid (TCA) cycle, suggesting an increased activity of the pyruvate dehydrogenase complex (PDC). Consistently, FLT3-ITD-positive cells expressed high levels of PDP1, an activator of the PDC. Combining endogenous tagging of PDP1 with genome-wide CRISPR screens revealed that FLT3-ITD induces PDP1 expression through the RAS signaling axis. PDP1 knockdown resulted in reduced cellular respiration thereby impairing the proliferation of only FLT3-ITD cells. These cells continued to depend on PDP1, even in hypoxic conditions, and unlike FLT3-ITD-negative cells, they exhibited a rapid, PDP1-dependent revival of their respiratory capacity during reoxygenation. Moreover, we show that PDP1 modifies the response to FLT3 inhibition. Upon incubation with the FLT3 tyrosine kinase inhibitor quizartinib (AC220), PDP1 persisted or was upregulated, resulting in a further shift of glucose/pyruvate metabolism towards the TCA cycle. Overexpression of PDP1 enhanced, while PDP1 depletion diminished AC220 resistance in cell lines and peripheral blasts from an AC220-resistant AML patient in vivo. In conclusion, FLT3-ITD assures the expression of PDP1, a pivotal metabolic regulator that enhances oxidative glucose metabolism and drug resistance. Hence, PDP1 emerges as a potentially targetable vulnerability in the management of AML.

Oxidative Phosphorylation Fueled by Fatty Acid Oxidation Sensitizes Leukemic Stem Cells to Cold.

Dependency on mitochondrial oxidative phosphorylation (OxPhos) is a potential weakness for leukemic stem cells (LSC) that can be exploited for therapeutic purposes. Fatty acid oxidation (FAO) is a crucial OxPhos-fueling catabolic pathway for some acute myeloid leukemia (AML) cells, particularly chemotherapy-resistant AML cells. Here, we identified cold sensitivity at 4°C (cold killing challenge; CKC4), commonly used for sample storage, as a novel vulnerability that selectively kills AML LSCs with active FAO-supported OxPhos while sparing normal hematopoietic stem cells. Cell death of OxPhos-positive leukemic cells was induced by membrane permeabilization at 4°C; by sharp contrast, leukemic cells relying on glycolysis were resistant. Forcing glycolytic cells to activate OxPhos metabolism sensitized them to CKC4. Lipidomic and proteomic analyses showed that OxPhos shapes the composition of the plasma membrane and introduces variation of 22 lipid subfamilies between cold-sensitive and cold-resistant cells. Together, these findings indicate that steady-state energy metabolism at body temperature predetermines the sensitivity of AML LSCs to cold temperature, suggesting that cold sensitivity could be a potential OxPhos biomarker. These results could have important implications for designing experiments for AML research to avoid cell storage at 4°C. SIGNIFICANCE: Mitochondrial metabolism fueled by FAO alters the membrane composition and introduces membrane fragility upon cold exposure in OxPhos-driven AML and in LSCs. See related commentary by Jones, p. 2441.

Evolutionary landscape of clonal hematopoiesis in 3,359 individuals from the general population.

Knowledge about evolution of clonal hematopoiesis, which may drive malignant progression, is crucial for clinical decision-making. We investigated the landscape of clonal evolution by error-corrected sequencing on 7,045 sequential samples from 3,359 individuals in the prospective population-based Lifelines cohort, with a special focus on cytosis and cytopenia. Spliceosome (SRSF2/U2AF1/SF3B1) and JAK2 mutated clones show highest growth rates over a median 3.6-year period, while clone sizes for DNMT3A and TP53 increase only marginally, independent of cytosis or cytopenia. Nevertheless, large differences are observed between individuals carrying the same mutation, indicative of modulation by non-mutation-related factors. Clonal expansion is not dependent on classical cancer risk factors (e.g., smoking). Risk for incident myeloid malignancy diagnosis is highest for JAK2, spliceosome, or TP53 mutations and absent for DNMT3A, and it is mostly preceded by cytosis or cytopenia. The results provide important insight into high-risk evolutionary patterns to guide monitoring of "CHIP" and "CCUS."

M2 macrophages drive leukemic transformation by imposing resistance to phagocytosis and improving mitochondrial metabolism.

It is increasingly becoming clear that cancers are a symbiosis of diverse cell types and tumor clones. Combined single-cell RNA sequencing, flow cytometry, and immunohistochemistry studies of the innate immune compartment in the bone marrow of patients with acute myeloid leukemia (AML) reveal a shift toward a tumor-supportive M2-polarized macrophage landscape with an altered transcriptional program, with enhanced fatty acid oxidation and NAD+ generation. Functionally, these AML-associated macrophages display decreased phagocytic activity and intra-bone marrow coinjection of M2 macrophages together with leukemic blasts strongly enhances in vivo transformation potential. A 2-day in vitro exposure to M2 macrophages results in the accumulation of CALRlow leukemic blast cells, which are now protected against phagocytosis. Moreover, M2-exposed "trained" leukemic blasts display increased mitochondrial metabolism, in part mediated via mitochondrial transfer. Our study provides insight into the mechanisms by which the immune landscape contributes to aggressive leukemia development and provides alternatives for targeting strategies aimed at the tumor microenvironment.

Galectin-3 and Blood Group: Binding Properties, Effects on Plasma Levels, and Consequences for Prognostic Performance.

Previous studies have reported an association between ABO type blood group and cardiovascular (CV) events and outcomes. The precise mechanisms underpinning this striking observation remain unknown, although differences in von Willebrand factor (VWF) plasma levels have been proposed as an explanation. Recently, galectin-3 was identified as an endogenous ligand of VWF and red blood cells (RBCs) and, therefore, we aimed to explore the role of galectin-3 in different blood groups. Two in vitro assays were used to assess the binding capacity of galectin-3 to RBCs and VWF in different blood groups. Additionally, plasma levels of galectin-3 were measured in different blood groups in the Ludwigshafen Risk and Cardiovascular Health (LURIC) study (2571 patients hospitalized for coronary angiography) and validated in a community-based cohort of the Prevention of Renal and Vascular End-stage Disease (PREVEND) study (3552 participants). To determine the prognostic value of galectin-3 in different blood groups, logistic regression and cox regression models were used with all-cause mortality as the primary outcome. First, we demonstrated that galectin-3 has a higher binding capacity for RBCs and VWF in non-O blood groups, compared to blood group O. Additionally, LURIC patients with non-O blood groups had substantially lower plasma levels of galectin-3 (15.0, 14.9, and 14.0 µg/L in blood groups A, B, and AB, respectively, compared to 17.1 µg/L in blood group O, p < 0.0001). Finally, the independent prognostic value of galectin-3 for all-cause mortality showed a non-significant trend towards higher mortality in non-O blood groups. Although plasma galectin-3 levels are lower in non-O blood groups, the prognostic value of galectin-3 is also present in subjects with a non-O blood group. We conclude that physical interaction between galectin-3 and blood group epitopes may modulate galectin-3, which may affect its performance as a biomarker and its biological activity.

Abnormal Platelet Counts and Clonal Hematopoiesis in the General Population.

Clonal hematopoiesis (CH) is defined by the presence of somatic mutations that may cause clonal expansion of hematopoietic cells. Here, we investigated the association between platelet count abnormalities, CH and consequences on overall survival and the development of hematological malignancies. Individuals with thrombocytopenia (n = 631) or thrombocytosis (n = 178) ≥60 years, and their age- and sex-matched controls, were selected within the population-based Lifelines cohort (n = 167,729). Although the prevalence of CH was not increased in thrombocytopenia cases compared with their controls (37.9% vs 39.3%; P = 0.639), mutations in spliceosome genes (SF3B1, SRSF2, U2AF1) were significantly enriched in thrombocytopenia cases (P = 0.007). Overall, CH in combination with thrombocytopenia did not impact on survival, but thrombocytopenia in combination with multiple mutated genes (hazard ratio [HR] = 2.08, 95% confidence interval [CI], 1.24-3.50; P = 0.006), mutations in TP53 (HR = 5.83, 95% CI, 2.49-13.64; P < 0.001) or spliceosome genes (HR = 2.69, 95% CI, 1.29-5.63; P = 0.009) increased the risk of death. The prevalence of CH in thrombocytosis cases was higher compared with controls (55.8% vs 37.7%; P < 0.001). Especially mutations in JAK2 (P < 0.001) and CALR (P = 0.003) were enriched in individuals with thrombocytosis. The presence of CH in individuals with thrombocytosis did not impact on overall survival. However, during follow-up of 11 years 23% of the individuals with thrombocytosis and CH were diagnosed with hematological malignancies. From these, 81% were diagnosed with myeloproliferative disease and 76% carried driver mutations JAK2, CALR, or MPL.

Clinical significance of mitochondrial DNA content in acute promyelocytic leukaemia.

Although a growing body of evidence demonstrates that altered mtDNA content (mtDNAc) has clinical implications in several types of solid tumours, its prognostic relevance in acute promyelocytic leukaemia (APL) patients remains largely unknown. Here, we show that patients with higher-than-normal mtDNAc had better outcomes regardless of tumour burden. These results were more evident in patients with low-risk of relapse. The multivariate Cox proportional hazard model demonstrated that high mtDNAc was independently associated with a decreased cumulative incidence of relapse. Altogether, our data highlights the possible role of mitochondrial metabolism in APL patients treated with ATRA.

Clonal hematopoiesis in patients with stem cell mobilization failure: a nested case-control study.

Inadequate mobilization of peripheral blood progenitor cells (PBPCs) is a limiting factor to proceeding with autologous hematopoietic cell transplantation (auto-HCT). To assess the impact of clonal hematopoiesis (CH) on mobilization failure of PBPC for auto-HCT, we investigated the characteristics of poor mobilizers (with a total PBPC collection <2 × 106 CD34+ cells per kg) in a consecutive single-center cohort of 776 patients. Targeted error-corrected next-generation sequencing of 28 genes was performed in a nested case-control cohort of 90 poor mobilizers and 89 matched controls. CH was detected in 48 out of 179 patients (27%), with most patients carrying a single mutation. The presence of CH (detected at variant allele frequency [VAF] ≥ 1%) did not associate with poor mobilization potential (31% vs 22% in controls, odds ratio, 1.55; 95% confidence interval, 0.76-3.23; P = .238). PPM1D mutations were detected more often in poor mobilizers (P = .005). In addition, TP53 mutations in this cohort were detected exclusively in patients with poor mobilization potential (P = .06). The incidence of therapy-related myeloid neoplasms (t-MN) was higher among patients with mobilization failure (P = .014). Although poor mobilizers experienced worse overall survival (P = .019), this was not affected by the presence of CH. We conclude that CH at low VAF (1%-10%) is common at the time of stem cell mobilization. TP53 mutations and PPM1D mutations are associated with poor mobilization potential and their role in subsequent development of t-MN in these individuals should be established.

The PIP4K2 inhibitor THZ-P1-2 exhibits antileukemia activity by disruption of mitochondrial homeostasis and autophagy.

The treatment of acute leukemia is challenging because of the genetic heterogeneity between and within patients. Leukemic stem cells (LSCs) are relatively drug-resistant and frequently relapse. Their plasticity and capacity to adapt to extracellular stress, in which mitochondrial metabolism and autophagy play important roles, further complicates treatment. Genetic models of phosphatidylinositol-5-phosphate 4-kinase type 2 protein (PIP4K2s) inhibition have demonstrated the relevance of these enzymes in mitochondrial homeostasis and autophagic flux. Here, we uncovered the cellular and molecular effects of THZ-P1-2, a pan-inhibitor of PIP4K2s, in acute leukemia cells. THZ-P1-2 reduced cell viability and induced DNA damage, apoptosis, loss of mitochondrial membrane potential, and the accumulation of acidic vesicular organelles. Protein expression analysis revealed that THZ-P1-2 impaired autophagic flux. In addition, THZ-P1-2 induced cell differentiation and showed synergistic effects with venetoclax. In primary leukemia cells, LC-MS/MS-based proteome analysis revealed that sensitivity to THZ-P1-2 is associated with mitochondrial metabolism, cell cycle, cell-of-origin (hematopoietic stem cell and myeloid progenitor), and the TP53 pathway. The minimal effects of THZ-P1-2 observed in healthy CD34+ cells suggest a favorable therapeutic window. Our study provides insights into the pharmacological inhibition of PIP4K2s targeting mitochondrial homeostasis and autophagy, shedding light on a new class of drugs for acute leukemia.