Dactinomycin induces complete remission associated with nucleolar stress response in relapsed/refractory NPM1-mutated AML

Conventional chemotherapy: millions of cures, unresolved therapeutic index

In recent decades, millions of patients with cancer have been cured by chemotherapy alone. By 'cure', we mean that patients with cancers that would be fatal if left untreated receive a time-limited course of chemotherapy and their cancer disappears, never to return. In an era when hundreds of thousands of cancer genomes have been sequenced, a remarkable fact persists: in most patients who have been cured, we still do not fully understand the mechanisms underlying the therapeutic index by which the tumour cells are killed, but normal cells are somehow spared. In contrast, in more recent years, patients with cancer have benefited from targeted therapies that usually do not cure but whose mechanisms of therapeutic index are, at least superficially, understood. In this Perspective, we will explore the various and sometimes contradictory models that have attempted to explain why chemotherapy can cure some patients with cancer, and what gaps in our understanding of the therapeutic index of chemotherapy remain to be filled. We will summarize principles which have benefited curative conventional chemotherapy regimens in the past, principles which might be deployed in constructing combinations that include modern targeted therapies.

Preclinical Assessment of Dactinomycin in KMT2A-Rearranged Infant Acute Lymphoblastic Leukemia

Background/Objectives: Infants with KMT2A-rearranged B-cell acute lymphoblastic leukemia (ALL) have high rates of relapse and poor survival compared with children. Few new therapies have been identified over the past twenty years. The aim of this study was to identify existing anti-cancer agents that have the potential to be repurposed for the treatment of infant ALL. Methods: Eight extensively characterized infant ALL cell lines were treated with 62 anti-neoplastic drugs in vitro to identify agents that exhibit significant cytotoxicity. From this screen, we selected the most effective and clinically translatable agent for further in vitro and in vivo assessment to determine the potential for use in the clinical setting. Results: Our anti-cancer drug screen revealed significant activity of dactinomycin across all infant ALL cell lines. Further in vitro testing identified low half-maximal inhibitory concentrations (IC50) across our infant ALL cell lines in the nanomolar range. Combination testing with the conventional chemotherapeutic agents currently used to treat infants with ALL demonstrated additivity with cytarabine. In vivo assessment of dactinomycin identified 36 μg/kg as the maximum tolerated dose, with unacceptable toxicities at higher dose treatment. Treatment using doses of 18 μg/kg administered either once or twice a week derived a small but significant survival benefit in patient-derived xenografts. Conclusions: Dactinomycin is extensively used for the treatment of solid tumors in children and has an acceptable safety profile when used to treat infants in this context. However, despite being readily translational and exhibiting promising in vitro cytotoxicity, dactinomycin showed limited efficacy in vivo and therefore does not represent a priority candidate for integrating into therapy for infants with ALL.

Functions of the native NPM1 protein and its leukemic mutant

The nucleophosmin (NPM1) gene encodes for the most abundant nucleolar protein. Thanks to its property to act as histone chaperone and to shuttle between the nucleus and cytoplasm, the NPM1 protein is involved in multiple cellular function that are here extensively reviewed and include the formation of the nucleolus through liquid-liquid phase separation, regulation of ribosome biogenesis and transport, control of DNA repair and centrosome duplication as well as response to nucleolar stress. NPM1 is mutated in about 30-35% of adult acute myeloid leukemia (AML). Due to its unique biological and clinical features, NPM1-mutated AML is regarded as a distinct leukemia entity in the WHO 5th edition and ICC classifications of myeloid malignancies. The NPM1 mutant undergoes changes at the C-terminus of the protein that leads to its delocalization in the cytoplasm of the leukemic cells. Here, we focus also on its biological functions discussing the murine models of NPM1 mutations and the various mechanisms that occur at cytoplasmic and nuclear levels to promote and maintain NPM1-mutated AML.

Ziftomenib in relapsed or refractory acute myeloid leukaemia (KOMET-001): a multicentre, open-label, multi-cohort, phase 1 trial

BACKGROUND

Ziftomenib (KO-539) is an oral selective menin inhibitor with known preclinical activity in menin-dependent acute myeloid leukaemia models. The primary objective of this study was to determine the recommended phase 2 dose in patients with relapsed or refractory acute myeloid leukaemia based on safety, pharmacokinetics, pharmacodynamics, and preliminary activity.

METHODS

KOMET-001 is a multicentre, open-label, multi-cohort, phase 1/2 clinical trial of ziftomenib in adults with relapsed or refractory acute myeloid leukaemia. Results of the phase 1 study, conducted at 22 hospitals in France, Italy, Spain, and the USA, are presented here and comprise the dose-escalation (phase 1a) and dose-validation and expansion (phase 1b) phases. Eligible patients were aged 18 years or older, had relapsed or refractory acute myeloid leukaemia, and had an Eastern Cooperative Oncology Group performance status of 2 or less. For phase 1a, patients (all molecular subtypes) received ziftomenib (50-1000 mg) orally once daily in 28-day cycles. For phase 1b, patients with NPM1 mutations or with KMT2A rearrangements were randomly assigned (1:1) using third-party interactive response technology to two parallel dose cohorts (200 mg and 600 mg ziftomenib). Primary endpoints were maximum tolerated dose or recommended phase 2 dose in phase 1a, and safety, remission rates, and pharmacokinetics supporting recommended phase 2 dose determination in phase 1b. Analyses were performed in all patients who received at least one dose of ziftomenib (modified intention-to-treat population). Phase 1a/1b is complete. This trial is registered with ClinicalTrials.gov, NCT04067336, and the EU Clinical Trials register, EudraCT 2019-001545-41.

FINDINGS

From Sept 12, 2019, to Aug 19, 2022, 83 patients received 50-1000 mg ziftomenib (39 [47%] were male and 44 [53%] were female). Median follow-up was 22·3 months (IQR 15·4-30·2). Of 83 patients, the most common grade 3 or worse treatment-emergent adverse events were anaemia (20 [24%]), febrile neutropenia (18 [22%]), pneumonia (16 [19%]), differentiation syndrome (12 [15%]), thrombocytopenia (11 [13%]), and sepsis (ten [12%]). Overall, 68 of 83 patients had serious adverse events, with two reported treatment-related deaths (one differentiation syndrome and one cardiac arrest). Differentiation syndrome rate and severity influenced the decision to halt enrolment of patients with KMT2A rearrangements. In Phase 1b, no responses were reported in patients treated at the 200 mg dose level. At the recommended phase 2 dose of 600 mg, nine (25%) of 36 patients with KMT2A rearrangement or NPM1 mutation had complete remission or complete remission with partial haematologic recovery. Seven (35%) of 20 patients with NPM1 mutation treated at the recommended phase 2 dose had a complete remission.

INTERPRETATION

Ziftomenib showed promising clinical activity with manageable toxicity in heavily pretreated patients with relapsed or refractory acute myeloid leukaemia. Phase 2 assessment of ziftomenib combination therapy in the upfront and relapsed or refractory setting is ongoing.

FUNDING

Kura Oncology.

Ferroptosis-Related Gene Signature for Prognosis Prediction in Acute Myeloid Leukemia and Potential Therapeutic Options

Background

Limited data were available to understand the significance of ferroptosis in leukemia prognosis, regardless of the genomic background.

Methods

RNA-seq data from 151 AML patients were analyzed from The Cancer Genome Atlas (TCGA) database, along with 70 healthy samples from the Genotype-Tissue Expression (GTEx) database. Ferroptosis-related genes (FRGs) features were constructed by multivariate COX regression analysis and risk scores were calculated for each sample and a novel prediction model was identified. The validation was carried out using data from 35 AML patients and 13 healthy controls in our cohort. Drug sensitivity analysis was conducted on various chemotherapeutic drugs.

Results

A signature of 10 FRGs was identified, as prognostic predictors for AML, and the risk scores were calculated to constructed the prognostic features of FRGs. Significantly lower overall survival was observed in the high-risk group. The predictive ability of these features for AML prognosis was confirmed using Cox regression analysis, ROC curves, and DCA. The prediction model performed well in our clinical practices, and had its potential superiority when comparing to classical NCCN risk stratification. Multiple chemotherapy drugs, including paclitaxel, dactinomycin, cisplatin, etc. had a lower IC50 in FRGs high-risk group than low-risk group.

Conclusion

The AML prognosis model based on FRGs accurately predicts AML prognosis and drug sensitivity, and the drugs identified worthy further investigation.

Gilteritinib in combination with venetoclax, low-dose cytarabine and actinomycin D for relapsed or refractory FLT3-mutated acute myeloid leukaemia

We have conducted a retrospective, single-centre analysis of 20 patients with relapsed or refractory FLT3-mutated acute myeloid leukaemia (FLT3m AML) who received a salvage quadruplet regimen consisting of gilteritinib, venetoclax, low-dose cytarabine and actinomycin D (G-ACTIVE). G-ACTIVE resulted in a 95% (19/20) overall response rate and 75% (15/20) complete remission and complete remission with an incomplete platelet recovery (CR + CRp) rate. Out of 13 transplant-eligible patients, 11 (86%) proceeded to an allogeneic stem cell transplantation. The median overall survival and relapse-free survival after G-ACTIVE were 32 and 12.9 months respectively. The Day 60 mortality rate was 15%.

Could Targeting NPM1c+ Misfolding Be a Promising Strategy for Combating Acute Myeloid Leukemia?

Acute myeloid leukemia (AML) is a heterogeneous group of diseases classified into various types on the basis of distinct features concerning the morphology, cytochemistry and cytogenesis of leukemic cells. Among the different subtypes, the group "AML with gene mutations" includes the variations of the gene of the multifunctional protein nucleophosmin 1 (NPM1). These mutations are the most frequent (~30-35% of AML adult patients and less in pediatric ones) and occur predominantly in the C-terminal domain (CTD) of NPM1. The most important mutation is the insertion at W288, which determines the frame shift W288Cfs12/Ffs12/Lfs*12 and leads to the addition of 2-12 amino acids, which hamper the correct folding of NPM1. This mutation leads to the loss of the nuclear localization signal (NoLS) and to aberrant cytoplasmic localization, denoted as NPM1c+. Many investigations demonstrated that interfering with the cellular location and oligomerization status of NPM1 can influence its biological functions, including the proper buildup of the nucleolus, and therapeutic strategies have been proposed to target NPM1c+, particularly the use of drugs able to re-direct NPM1 localization. Our studies unveiled a direct link between AML mutations and the neat amyloidogenic character of the CTDs of NPM1c+. Herein, with the aim of exploiting these conformational features, novel therapeutic strategies are proposed that rely on the induction of the selective self-cytotoxicity of leukemic blasts by focusing on agents such as peptides, peptoids or small molecules able to enhance amyloid aggregation and targeting selectively AML-NPM1c+ mutations.

Precision and strategic targeting of novel mutation-specific vulnerabilities in acute myeloid leukemia: the semi-centennial of 7 + 3

The year 2023 marks the semi-centennial of the introduction of classic '7 + 3' chemotherapy for acute myeloid leukemia (AML) in 1973. It also marks the decennial of the first comprehensive sequencing efforts from The Cancer Genome Atlas (TCGA), which revealed that dozens of unique genes are recurrently mutated in AML genomes. Although more than 30 distinct genes have been implicated in AML pathogenesis, the current therapeutic armamentarium that is commercially available only targets FLT3 and IDH1/2 mutations, with olutasidenib as the most recent addition. This focused review spotlights management approaches that exploit the exquisite molecular dependencies of specific subsets of AML, with an emphasis on emerging therapies in the pipeline, including agents targeting TP53-mutant cells. We summarize precision and strategic targeting of AML based on leveraging functional dependencies and explore how mechanisms involving critical gene products can inform rational therapeutic design in 2024.

The PML hub: An emerging actor of leukemia therapies

PML assembles into nuclear domains that have attracted considerable attention from cell and cancer biologists. Upon stress, PML nuclear bodies modulate sumoylation and other post-translational modifications, providing an integrated molecular framework for the multiple roles of PML in apoptosis, senescence, or metabolism. PML is both a sensor and an effector of oxidative stress. Emerging data has demonstrated its key role in promoting therapy response in several hematological malignancies. While these membrane-less nuclear hubs can enforce efficient cancer cell clearance, their downstream pathways deserve better characterization. PML NBs are druggable and their known modulators may have broader clinical utilities than initially thought.

Potentiality of Actinomycetia Prevalent in Selected Forest Ecosystems in Assam, India to Combat Multi-Drug-Resistant Microbial Pathogens

Actinomycetia are known for their ability to produce a wide range of bioactive secondary metabolites having significant therapeutic importance. This study aimed to explore the potential of actinomycetia as a source of bioactive compounds with antimicrobial properties against multi-drug-resistant (MDR) clinical pathogens. A total of 65 actinomycetia were isolated from two unexplored forest ecosystems, namely the Pobitora Wildlife Sanctuary (PWS) and the Deepor Beel Wildlife Sanctuary (DBWS), located in the Indo-Burma mega-biodiversity hotspots of northeast India, out of which 19 isolates exhibited significant antimicrobial activity. 16S rRNA gene sequencing was used for the identification and phylogenetic analysis of the 19 potent actinomycetia isolates. The results reveal that the most dominant genus among the isolates was Streptomyces (84.21%), followed by rare actinomycetia genera such as Nocardia, Actinomadura, and Nonomuraea. Furthermore, seventeen of the isolates tested positive for at least one antibiotic biosynthetic gene, specifically type II polyketide synthase (PKS-II) and nonribosomal peptide synthetases (NRPSs). These genes are associated with the production of bioactive compounds with antimicrobial properties. Among the isolated strains, three actinomycetia strains, namely Streptomyces sp. PBR1, Streptomyces sp. PBR36, and Streptomyces sp. DBR11, demonstrated the most potent antimicrobial activity against seven test pathogens. This was determined through in vitro antimicrobial bioassays and the minimum inhibitory concentration (MIC) values of ethyl acetate extracts. Gas chromatography-mass spectrometry (GS-MS) and whole-genome sequencing (WGS) of the three strains revealed a diverse group of bioactive compounds and secondary metabolite biosynthetic gene clusters (smBGCs), respectively, indicating their high therapeutic potential. These findings highlight the potential of these microorganisms to serve as a valuable resource for the discovery and development of novel antibiotics and other therapeutics with high therapeutic potential.

Biomolecular Condensates in Myeloid Leukemia: What Do They Tell Us?

Recent studies have suggested that several oncogenic and tumor-suppressive proteins carry out their functions in the context of specific membrane-less cellular compartments. As these compartments, generally referred to as onco-condensates, are specific to tumor cells and are tightly linked to disease development, the mechanisms of their formation and maintenance have been intensively studied. Here we review the proposed leukemogenic and tumor-suppressive activities of nuclear biomolecular condensates in acute myeloid leukemia (AML). We focus on condensates formed by oncogenic fusion proteins including nucleoporin 98 (NUP98), mixed-lineage leukemia 1 (MLL1, also known as KMT2A), mutated nucleophosmin (NPM1c) and others. We also discuss how altered condensate formation contributes to malignant transformation of hematopoietic cells, as described for promyelocytic leukemia protein (PML) in PML::RARA-driven acute promyelocytic leukemia (APL) and other myeloid malignancies. Finally, we discuss potential strategies for interfering with the molecular mechanisms related to AML-associated biomolecular condensates, as well as current limitations of the field.

Preclinical Validation of an Advanced Therapy Medicinal Product Based on Cytotoxic T Lymphocytes Specific for Mutated Nucleophosmin (NPM1mut) for the Treatment of NPM1mut-Acute Myeloid Leukemia

Acute myeloid leukemia (AML) with nucleophosmin (NPM1) genetic mutations is the most common subtype in adult patients. Refractory or relapsed disease in unfit patients or after allogeneic hematopoietic stem cell transplantation (allo-HSCT) has a poor prognosis. NPM1-mutated protein, stably expressed on tumor cells but not on normal tissues, may serve as an ideal target for NPM1-mutated AML immunotherapy. The study aim was to investigate the feasibility of producing mutated-NPM1-specific cytotoxic T cells (CTLs) suitable for somatic cell therapy to prevent or treat hematologic relapse in patients with NPM1-mutated AML. T cells were expanded or primed from patient or donor peripheral blood mononuclear cells by NPM1-mutated protein-derived peptides, and tested for leukemia antigen-targeted cytotoxic activity, cytokine production and hematopoietic precursor inhibitory effect. We found that mutated-NPM1-specific CTLs, displaying specific cytokine production and high-level cytotoxicity against patients' leukemia blasts, and limited inhibitory activity in clonogenic assays, could be obtained from both patients and donors. The polyfunctional mutated-NPM1-specific CTLs included both CD8+ and CD4+ T cells endowed with strong lytic capacity. Our results suggest that mutated-NPM1-targeted CTLs may be a useful therapeutic option to control low-tumor burden relapse following conventional chemotherapy in older NPM1-mutated AML patients or eradicate persistent MRD after HSCT.

Npm1 haploinsufficiency in collaboration with MEIS1 is sufficient to induce AML in mice

NPM1 is among the most frequently mutated genes in acute myeloid leukemia (AML). Mutations in the NPM1 gene result in the increased export of NPM1 to the cytoplasm (NPM1c) and are associated with multiple transforming events including the aberrant upregulation of MEIS1 that maintains stem cell and cell cycle-associated pathways in NPM1c AML. However, another consequence of the NPM1c mutation is the inadequate levels of NPM1 wild-type in the nucleus and nucleolus, caused by the loss of one wild-type allele in addition to enforced NPM1 nuclear export. The contribution of NPM1 haploinsufficiency independently of the NPM1 mutation to AML development and its relationship with MEIS1 function is poorly understood. Using mouse models, our study shows that NPM1 haploinsufficiency paired with MEIS1 overexpression is sufficient to induce a fully penetrant AML in mice that transcriptionally resembles human NPM1c AML. NPM1 haploinsufficiency alters MEIS1-binding occupancies such that it binds the promoter of the oncogene structural maintenance of chromosome protein 4 (SMC4) in NPM1 haploinsufficient AML cells but not in NPM1 wild-type-harboring Hoxa9/Meis1-transformed cells. SMC4 is higher expressed in haploinsufficient and NPM1c+ AML cells, which are more vulnerable to the disruption of the MEIS1-SMC4 axis compared with AML cells with nonmutated NPM1. Taken together, our study underlines that NPM1 haploinsufficiency on its own is a key factor of myeloid leukemogenesis and characterizes the MEIS1-SMC4 axis as a potential therapeutic target in this AML subtype.

Targeting and Monitoring Acute Myeloid Leukaemia with Nucleophosmin-1 (NPM1) Mutation

Mutations in NPM1, also known as nucleophosmin-1, B23, NO38, or numatrin, are seen in approximately one-third of patients with acute myeloid leukaemia (AML). A plethora of treatment strategies have been studied to determine the best possible approach to curing NPM1-mutated AML. Here, we introduce the structure and function of NPM1 and describe the application of minimal residual disease (MRD) monitoring using molecular methods by means of quantitative polymerase chain reaction (qPCR), droplet digital PCR (ddPCR), next-generation sequencing (NGS), and cytometry by time of flight (CyTOF) to target NPM1-mutated AML. Current drugs, now regarded as the standard of care for AML, as well as potential drugs still under development, will also be explored. This review will focus on the role of targeting aberrant NPM1 pathways such as BCL-2 and SYK; as well as epigenetic regulators (RNA polymerase), DNA intercalators (topoisomerase II), menin inhibitors, and hypomethylating agents. Aside from medication, the effects of stress on AML presentation have been reported, and some possible mechanisms outlined. Moreover, targeted strategies will be briefly discussed, not only for the prevention of abnormal trafficking and localisation of cytoplasmic NPM1 but also for the elimination of mutant NPM1 proteins. Lastly, the advancement of immunotherapy such as targeting CD33, CD123, and PD-1 will be mentioned.

Apoptotic Induction in Human Cancer Cell Lines by Antimicrobial Compounds from Antarctic Streptomyces fildesensis (INACH3013)

The Antarctic Streptomyces fildesensis has been recognized for its production of antimicrobial compounds with interesting biological activities against foodborne bacteria and multi-resistant strains, but not for its potential antiproliferative activity and mechanisms involved. Two bioactive ethyl acetate extract (EAE) fractions were purified via thin-layer chromatography and High-Performance Liquid Chromatography (HPLC), showing that orange-colored compounds displayed antimicrobial activity against pathogenic bacteria even after shock thermal treatment. The UV–VIS features of the active compounds, the TLC assay with actinomycin-D pure standard, Fourier transform infrared (FTIR) spectra and the ANTISMASH analysis support the presence of actinomycin-like compounds. We demonstrated that S. fildesensis displays antiproliferative activity against human tumor cell lines, including human breast cancer (MCF-7), prostate cancer (PC-3), colon cancer (HT-29) and non-tumoral colon epithelial cells (CoN). The half-maximal effective concentrations (EC50) ranged from 3.98 µg/mL to 0.1 µg/mL. Our results reveal that actinomycin-like compounds of S. fildesensis induced apoptosis mediated by caspase activation, decreasing the mitochondrial membrane potential and altering the cell morphology in all tumoral and non-tumoral cell lines analyzed. These findings confirm the potential of the psychrotolerant Antarctic S. fildesensis species as a promising source for obtaining potential novel anticancer compounds.

Heightened apoptotic priming of vascular cells across tissues and life span predisposes them to cancer therapy-induced toxicities

Although major organ toxicities frequently arise in patients treated with cytotoxic or targeted cancer therapies, the mechanisms that drive them are poorly understood. Here, we report that vascular endothelial cells (ECs) are more highly primed for apoptosis than parenchymal cells across many adult tissues. Consequently, ECs readily undergo apoptosis in response to many commonly used anticancer agents including cytotoxic and targeted drugs and are more sensitive to ionizing radiation and BH3 mimetics than parenchymal cells in vivo. Further, using differentiated isogenic human induced pluripotent stem cell models of ECs and vascular smooth muscle cells (VSMCs), we find that these vascular cells exhibit distinct drug toxicity patterns, which are linked to divergent therapy-induced vascular toxicities in patients. Collectively, our results demonstrate that vascular cells are highly sensitive to apoptosis-inducing stress across life span and may represent a "weakest link" vulnerability in multiple tissues for development of toxicities.

From Serendipity to Rational Identification of the 5,6,7,8-Tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4(3H)-one Core as a New Chemotype of AKT1 Inhibitors for Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic malignancy whose prognosis is globally poor. In more than 60% of AML patients, the PI3K/AKTs/mTOR signaling pathway is aberrantly activated because of oncogenic driver alterations and further enhanced by chemotherapy as a mechanism of drug resistance. Against this backdrop, very recently we have started a multidisciplinary research project focused on AKT1 as a pharmacological target to identify novel anti-AML agents. Indeed, the serendipitous finding of the in-house compound T187 as an AKT1 inhibitor has paved the way to the rational identification of new active small molecules, among which T126 has emerged as the most interesting compound with IC₅₀ = 1.99 ± 0.11 μM, ligand efficiency of 0.35, and a clear effect at low micromolar concentrations on growth inhibition and induction of apoptosis in AML cells. The collected results together with preliminary SAR data strongly indicate that the 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4(3H)-one derivative T126 is worthy of future biological experiments and medicinal chemistry efforts aimed at developing a novel chemical class of AKT1 inhibitors as anti-AML agents.

Targeted therapy in NPM1-mutated AML: Knowns and unknowns

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by malignant proliferation of myeloid hematopoietic stem/progenitor cells. NPM1 represents the most frequently mutated gene in AML and approximately 30% of AML cases carry NPM1 mutations. Mutated NPM1 result in the cytoplasmic localization of NPM1 (NPM1c). NPM1c interacts with other proteins to block myeloid differentiation, promote cell proliferation and impair DNA damage repair. NPM1 is a good prognostic marker, but some patients ultimately relapse or fail to respond to therapy. It is urgent for us to find optimal therapies for NPM1-mutated AML. Efficacy of multiple drugs is under investigation in NPM1-mutated AML, and several clinical trials have been registered. In this review, we summarize the present knowledge of therapy and focus on the possible therapeutic interventions for NPM1-mutated AML.

Current status and future perspectives in targeted therapy of NPM1-mutated AML

Nucleophosmin 1 (NPM1) is a nucleus-cytoplasmic shuttling protein which is predominantly located in the nucleolus and exerts multiple functions, including regulation of centrosome duplication, ribosome biogenesis and export, histone assembly, maintenance of genomic stability and response to nucleolar stress. NPM1 mutations are the most common genetic alteration in acute myeloid leukemia (AML), detected in about 30–35% of adult AML and more than 50% of AML with normal karyotype. Because of its peculiar molecular and clinico-pathological features, including aberrant cytoplasmic dislocation of the NPM1 mutant and wild-type proteins, lack of involvement in driving clonal hematopoiesis, mutual exclusion with recurrent cytogenetic abnormalities, association with unique gene expression and micro-RNA profiles and high stability at relapse, NPM1-mutated AML is regarded as a distinct genetic entity in the World Health Organization (WHO) classification of hematopoietic malignancies. Starting from the structure and functions of NPM1, we provide an overview of the potential targeted therapies against NPM1-mutated AML and discuss strategies aimed at interfering with the oligomerization (compound NSC348884) and the abnormal traffic of NPM1 (avrainvillamide, XPO1 inhibitors) as well as at inducing selective NPM1-mutant protein degradation (ATRA/ATO, deguelin, (-)-epigallocatechin-3-gallate, imidazoquinoxaline derivatives) and at targeting the integrity of nucleolar structure (actinomycin D). We also discuss the current therapeutic results obtained in NPM1-mutated AML with the BCL-2 inhibitor venetoclax and the preliminary clinical results using menin inhibitors targeting HOX/MEIS1 expression. Finally, we review various immunotherapeutic approaches in NPM1-mutated AML, including immune check-point inhibitors, CAR and TCR T-cell-based therapies against neoantigens created by the NPM1 mutations.

Advances in Nanomaterial-Based Platforms to Combat COVID-19: Diagnostics, Preventions, Therapeutics, and Vaccine Developments

The COVID-19 pandemic caused by the SARS-CoV-2, a ribonucleic acid (RNA) virus that emerged less than two years ago but has caused nearly 6.1 million deaths to date. Recently developed variants of the SARS-CoV-2 virus have been shown to be more potent and expanded at a faster rate. Until now, there is no specific and effective treatment for SARS-CoV-2 in terms of reliable and sustainable recovery. Precaution, prevention, and vaccinations are the only ways to keep the pandemic situation under control. Medical and scientific professionals are now focusing on the repurposing of previous technology and trying to develop more fruitful methodologies to detect the presence of viruses, treat the patients, precautionary items, and vaccine developments. Nanomedicine or nanobased platforms can play a crucial role in these fronts. Researchers are working on many effective approaches by nanosized particles to combat SARS-CoV-2. The role of a nanobased platform to combat SARS-CoV-2 is extremely diverse (i.e., mark to personal protective suit, rapid diagnostic tool to targeted treatment, and vaccine developments). Although there are many theoretical possibilities of a nanobased platform to combat SARS-CoV-2, until now there is an inadequate number of research targeting SARS-CoV-2 to explore such scenarios. This unique mini-review aims to compile and elaborate on the recent advances of nanobased approaches from prevention, diagnostics, treatment to vaccine developments against SARS-CoV-2, and associated challenges.

Nucleophosmin 1: from its pathogenic role to a tantalizing therapeutic target in acute myeloid leukemia

Nucleophosmin 1 (NPM1, also known as B23) is a multifunctional protein involved in a variety of cellular processes, including ribosomal maturation, centrosome replication, maintenance of genomic stability, cell cycle control, and apoptosis. NPM1 is the most commonly mutated gene in adult acute myeloid leukemia (AML) and is present in approximately 40% of all AML cases. The underlying mechanisms of mutant NPM1 (NPM1^mut) in leukemogenesis remain unclear. This review summarizes the structure and physiological function of NPM1, mechanisms underlying the pathogenesis of NPM1-mutated AML, and the potential role of NPM1 as a therapeutic target. It is reported that dysfunctional NPM1 might cause AML pathogenesis via its role as a protein chaperone, inhibiting differentiation of leukemia stem cells and regulation of non-coding RNAs. Besides conventional chemotherapies, NPM1 is a promising therapeutic target against AML that warrants further investigation. NPM1-based therapeutic strategies include inducing nucleolar relocalisation of NPM1 mutants, interfering with NPM1 oligomerization, and NPM1 as an immune response target.

EAPB0503, an Imidazoquinoxaline Derivative Modulates SENP3/ARF Mediated SUMOylation, and Induces NPM1c Degradation in NPM1 Mutant AML

Nucleophosmin-1 (NPM1) is a pleiotropic protein involved in numerous cellular processes. NPM1 shuttles between the nucleus and the cytoplasm, but exhibits a predominant nucleolar localization, where its fate and functions are exquisitely controlled by dynamic post-translational modifications (PTM). Sentrin/SUMO Specific Peptidase 3 (SENP3) and ARF are two nucleolar proteins involved in NPM1 PTMs. SENP3 antagonizes ARF-mediated NPM1 SUMOylation, to promote ribosomal biogenesis. In Acute Myeloid Leukemia (AML), NPM1 is frequently mutated, and exhibits an aberrant cytoplasmic localization (NPM1c). NPM1c mutations define a separate AML entity with good prognosis in some AML patients, rendering NPM1c as a potential therapeutic target. SENP3-mediated NPM1 de-SUMOylation induces resistance to therapy in NPM1c AML. Here, we demonstrate that the imidazoquinoxaline EAPB0503 prolongs the survival and results in selective reduction in the leukemia burden of NPM1c AML xenograft mice. Indeed, EAPB0503 selectively downregulates HDM2 expression and activates the p53 pathway in NPM1c expressing cells, resulting in apoptosis. Importantly, we unraveled that NPM1c expressing cells exhibit low basal levels of SUMOylation paralleled with high SENP3 and low ARF basal levels. EAPB0503 reverted these molecular players by inducing NPM1c SUMOylation and ubiquitylation, leading to its proteasomal degradation. EAPB0503-induced NPM1c SUMOylation is concurrent with SENP3 downregulation and ARF upregulation in NPM1c expressing cells. Collectively, these results provide a strong rationale for testing therapies modulating NPM1c post-translational modifications in the management of NPM1c AML.

Novel NPM1 exon 5 mutations and gene fusions leading to aberrant cytoplasmic nucleophosmin in AML

Nucleophosmin (NPM1) mutations in acute myeloid leukemia (AML) affect exon 12, but also sporadically affect exons 9 and 11, causing changes at the protein C-terminal end (tryptophan loss, nuclear export signal [NES] motif creation) that lead to aberrant cytoplasmic NPM1 (NPM1c+), detectable by immunohistochemistry. Combining immunohistochemistry and molecular analyses in 929 patients with AML, we found non-exon 12 NPM1 mutations in 5 (1.3%) of 387 NPM1c+ cases. Besides mutations in exons 9 (n = 1) and 11 (n = 1), novel exon 5 mutations were discovered (n = 3). Another exon 5 mutation was identified in an additional 141 patients with AML selected for wild-type NPM1 exon 12. Three NPM1 rearrangements (NPM1/RPP30, NPM1/SETBP1, NPM1/CCDC28A) were detected and characterized among 13 979 AML samples screened by cytogenetic/fluorescence in situ hybridization and RNA sequencing. Functional studies demonstrated that in AML cases, new NPM1 proteins harbored an efficient extra NES, either newly created or already present in the fusion partner, ensuring its cytoplasmic accumulation. Our findings support NPM1 cytoplasmic relocation as critical for leukemogenesis and reinforce the role of immunohistochemistry in predicting AML-associated NPM1 genetic lesions. This study highlights the need to develop new assays for molecular diagnosis and monitoring of NPM1-mutated AML.

Actinomycin D Targets NPM1c-Primed Mitochondria to Restore PML-Driven Senescence in AML Therapy

Acute myeloid leukemia (AML) pathogenesis often involves a mutation in the NPM1 nucleolar chaperone, but the bases for its transforming properties and overall association with favorable therapeutic responses remain incompletely understood. Here we demonstrate that an oncogenic mutant form of NPM1 (NPM1c) impairs mitochondrial function. NPM1c also hampers formation of promyelocytic leukemia (PML) nuclear bodies (NB), which are regulators of mitochondrial fitness and key senescence effectors. Actinomycin D (ActD), an antibiotic with unambiguous clinical efficacy in relapsed/refractory NPM1c-AMLs, targets these primed mitochondria, releasing mitochondrial DNA, activating cyclic GMP-AMP synthase signaling, and boosting reactive oxygen species (ROS) production. The latter restore PML NB formation to drive TP53 activation and senescence of NPM1c-AML cells. In several models, dual targeting of mitochondria by venetoclax and ActD synergized to clear AML and prolong survival through targeting of PML. Our studies reveal an unexpected role for mitochondria downstream of NPM1c and implicate a mitochondrial/ROS/PML/TP53 senescence pathway as an effector of ActD-based therapies.

SIGNIFICANCE

ActD induces complete remissions in NPM1-mutant AMLs. We found that NPM1c affects mitochondrial biogenesis and PML NBs. ActD targets mitochondria, yielding ROS which enforce PML NB biogenesis and restore senescence. Dual targeting of mitochondria with ActD and venetoclax sharply potentiates their anti-AML activities in vivo. This article is highlighted in the In This Issue feature, p. 2945.

Tumour-derived small extracellular vesicles suppress CD8+ T cell immune function by inhibiting SLC6A8-mediated creatine import in NPM1-mutated acute myeloid leukaemia

Acute myeloid leukaemia (AML) carrying nucleophosmin (NPM1) mutations has been defined as a distinct entity of acute leukaemia. Despite remarkable improvements in diagnosis and treatment, the long-term outcomes for this entity remain unsatisfactory. Emerging evidence suggests that leukaemia, similar to other malignant diseases, employs various mechanisms to evade killing by immune cells. However, the mechanism of immune escape in NPM1-mutated AML remains unknown. In this study, both serum and leukemic cells from patients with NPM1-mutated AML impaired the immune function of CD8+ T cells in a co-culture system. Mechanistically, leukemic cells secreted miR-19a-3p into the tumour microenvironment (TME) via small extracellular vesicles (sEVs), which was controlled by the NPM1-mutated protein/CCCTC-binding factor (CTCF)/poly (A)-binding protein cytoplasmic 1 (PABPC1) signalling axis. sEV-related miR-19a-3p was internalized by CD8+ T cells and directly repressed the expression of solute-carrier family 6 member 8 (SLC6A8; a creatine-specific transporter) to inhibit creatine import. Decreased creatine levels can reduce ATP production and impair CD8+ T cell immune function, leading to immune escape by leukemic cells. In summary, leukemic cell-derived sEV-related miR-19a-3p confers immunosuppression to CD8+ T cells by targeting SLC6A8-mediated creatine import, indicating that sEV-related miR-19a-3p might be a promising therapeutic target for NPM1-mutated AML.

Therapeutic implications of menin inhibition in acute leukemias

Menin inhibitors are novel targeted agents currently in clinical development for the treatment of genetically defined subsets of acute leukemia. Menin has a tumor suppressor function in endocrine glands. Germline mutations in the gene encoding menin cause the multiple endocrine neoplasia type 1 (MEN1) syndrome, a hereditary condition associated with tumors of the endocrine glands. However, menin is also critical for leukemogenesis in subsets driven by rearrangement of the Lysine Methyltransferase 2A (KMT2A) gene, previously known as mixed-lineage leukemia (MLL), which encodes an epigenetic modifier. These seemingly opposing functions of menin can be explained by its various roles in gene regulation. Therefore, leukemias with rearrangement of KMT2A are predicted to respond to menin inhibition with early clinical data validating this proof-of-concept. These leukemias affect infants, children and adults, and lead to adverse outcomes with current standard therapies. Recent studies have identified novel targets in acute leukemia that are susceptible to menin inhibition, such as mutated Nucleophosmin 1 (NPM1), the most common genetic alteration in adult acute myeloid leukemia (AML). In addition to these alterations, other leukemia subsets with similar transcriptional dependency could be targeted through menin inhibition. This led to rationally designed clinical studies, investigating small-molecule oral menin inhibitors in relapsed acute leukemias with promising early results. Herein, we discuss the physiologic and malignant biology of menin, the mechanisms of leukemia in these susceptible subsets, and future therapeutic strategies using these inhibitors in acute leukemia.

Neoantigen-Specific T-Cell Immune Responses: The Paradigm of NPM1-Mutated Acute Myeloid Leukemia

The C-terminal aminoacidic sequence from NPM1-mutated protein, absent in normal human tissues, may serve as a leukemia-specific antigen and can be considered an ideal target for NPM1-mutated acute myeloid leukemia (AML) immunotherapy. Different in silico instruments and in vitro/ex vivo immunological platforms have identified the most immunogenic epitopes from NPM1-mutated protein. Spontaneous development of endogenous NPM1-mutated-specific cytotoxic T cells has been observed in patients, potentially contributing to remission maintenance and prolonged survival. Genetically engineered T cells, namely CAR-T or TCR-transduced T cells, directed against NPM1-mutated peptides bound to HLA could prospectively represent a promising therapeutic approach. Although either adoptive or vaccine-based immunotherapies are unlikely to be highly effective in patients with full-blown leukemia, these strategies, potentially in combination with immune-checkpoint inhibitors, could be promising in maintaining remission or preemptively eradicating persistent measurable residual disease, mainly in patients ineligible for allogeneic hematopoietic stem cell transplant (HSCT). Alternatively, neoantigen-specific donor lymphocyte infusion derived from healthy donors and targeting NPM1-mutated protein to selectively elicit graft-versus-leukemia effect may represent an attractive option in subjects experiencing post-HSCT relapse. Future studies are warranted to further investigate dynamics of NPM1-mutated-specific immunity and explore whether novel individualized immunotherapies may have potential clinical utility in NPM1-mutated AML patients.