Role of nucleophosmin in embryonic development and tumorigenesis

NPM1 inhibits tumoral antigen presentation to promote immune evasion and tumor progression

BACKGROUND

Tumor cells develop multiple mechanisms to facilitate their immune evasion. Identifying tumor-intrinsic factors that support immune evasion may provide new strategies for cancer immunotherapy. We aimed to explore the function and the mechanism of the tumor-intrinsic factor NPM1, a multifunctional nucleolar phosphoprotein, in cancer immune evasion and progression.

METHODS

The roles of NPM1 in tumor progression and tumor microenvironment (TME) reprogramming were examined by subcutaneous inoculation of Npm1-deficient tumor cells into syngeneic mice, and then explored by CyTOF, flow cytometry, immunohistochemistry staining, and RNA-seq. The in-vitro T-cell killing of OVA-presenting tumor cells by OT-1 transgenic T cells was observed. The interaction of NPM1 and IRF1 was verified by Co-IP. The regulation of NPM1 in IRF1 DNA binding to Nlrc5, Ciita promoter was determined by dual-luciferase reporter assay and ChIP-qPCR.

RESULTS

High levels of NPM1 expression predict low survival rates in various human tumors. Loss of NPM1 inhibited tumor progression and enhanced the survival of tumor-bearing mice. Npm1-deficient tumors showed increased CD8+ T cell infiltration and activation alongside the reduced presence of immunosuppressive cells. Npm1 deficiency increased MHC-I and MHC-II molecules and specific T-cell killing. Mechanistically, NPM1 associates with the transcription factor IRF1 and then sequesters IRF1 from binding to the Nlrc5 and Ciita promoters to suppress IRF1-mediated expression of MHC-I and MHC-II molecules in tumor cells.

CONCLUSIONS

Tumor-intrinsic NPM1 promotes tumor immune evasion via suppressing IRF1-mediated antigen presentation to impair tumor immunogenicity and reprogram the immunosuppressive TME. Our study identifies NPM1 as a potential target for improving cancer immunotherapy.

Chronic myelomonocytic leukemia with NPM1 mutation or acute myeloid leukemia?

The 2022 WHO revision and the ICC classification have recently modified the diagnostic criteria for chronic myelomonocytic leukemia (CMML) and acute myeloid leukemia. However, there is no consensus on whether CMML with NPM1 mutation (NPM1mut) should be diagnosed as AML. Nowadays, it is a subject of discussion because of its diagnostic and therapeutic implications. Therefore, we describe a case of a patient diagnosed with CMML NPM1mut and briefly review the literature to highlight the uncertainty about how to classify a CMML with NPM1 mutation. We emphasize the importance of a comprehensive molecular study, which is crucial to optimize the individualized treatment of patients, enabling them to access targeted therapies.

Nucleophosmin: A Nucleolar Phosphoprotein Orchestrating Cellular Stress Responses

Nucleophosmin (NPM1) is a key nucleolar protein released from the nucleolus in response to stress stimuli. NPM1 functions as a stress regulator with nucleic acid and protein chaperone activities, rapidly shuttling between the nucleus and cytoplasm. NPM1 is ubiquitously expressed in tissues and can be found in the nucleolus, nucleoplasm, cytoplasm, and extracellular environment. It plays a central role in various biological processes such as ribosome biogenesis, cell cycle regulation, cell proliferation, DNA damage repair, and apoptosis. In addition, it is highly expressed in cancer cells and solid tumors, and its mutation is a major cause of acute myeloid leukemia (AML). This review focuses on NPM1's structural features, functional diversity, subcellular distribution, and role in stress modulation.

Systematic characterization of m6A proteomics across 12 cancer types: a multi-omics integration study

The modification patterns of N6-methyladenosine (m6A) regulators and interacting genes are deeply involved in tumors. However, the effect of m6A modification patterns on human proteomics remains largely unknown. We evaluated the molecular characteristics and clinical relevance of m6A modification proteomics patterns among 1013 pan-cancer samples from the Clinical Proteomic Tumor Analysis Consortium (CPTAC). More than half of the m6A proteins were expressed at higher levels in tumor tissues and presented oncogenic characteristics. Furthermore, we performed multi-omics analyses integrating with transcriptomics data of m6A regulators and interactive coding and non-coding RNAs and developed a m6A multi-omics signature to identify potential m6A modification target proteins across global proteomics. It was significantly associated with overall survival in nine cancer types, tumor mutation burden (P = 0.01), and immune checkpoints including PD-L1 (P = 4.9 × 10-8) and PD-1 (P < 0.01). We identified 51 novel proteins associated with the multi-omics signature (PFDR < 0.05). These proteins were functional through pathway enrichment analyses. The protein with the highest hit frequency was CHORDC1, which was significantly up-regulated in tumor tissues in nine cancer types. Its higher abundance was significantly associated with a poorer prognosis in seven cancer types. The identified m6A target proteins might provide infomation for the study of molecular mechanism of cancer.

Infrequent Presentations of Chronic NPM1-Mutated Myeloid Neoplasms: Clinicopathological Features of Eight Cases from a Single Institution and Review of the Literature

Non-acute myeloid neoplasms (MNs) with NPM1 mutations (NPM1mut-MNs) pose a diagnostic and therapeutic dilemma, primarily manifesting as chronic myelomonocytic leukemia (CMML) and myelodysplastic syndromes (MDS). The classification and treatment approach for these conditions as acute myeloid leukemia (AML) are debated. We describe eight cases of atypical NPM1mut-MNs from our institution and review the literature. We include a rare case of concurrent prostate carcinoma and MN consistent with chronic eosinophilic leukemia, progressing to myeloid sarcoma of the skin. Of the remaining seven cases, five were CMML and two were MDS. NPM1 mutations occur in 3-5% of CMML and 1-6% of MDS, with an increased likelihood of rapid evolution to AML. Their influence on disease progression varies, and their prognostic significance in non-acute MNs is less established than in AML. Non-acute MNs with NPM1 mutations may display an aggressive clinical course, emphasizing the need for a comprehensive diagnosis integrating clinical and biological data. Tailoring patient management on an individualized basis, favoring intensive treatment aligned with AML protocols, is crucial, regardless of blast percentage. Research on the impact of NPM1 mutations in non-acute myeloid neoplasms is ongoing, requiring challenging prospective studies with substantial patient cohorts and extended follow-up periods for validation.

Pumilio1 regulates NPM3/NPM1 axis to promote PD-L1-mediated immune escape in gastric cancer

Abnormal regulation of RNA binding proteins (RBPs) plays an essential role in tumorigenesis and progression, but their functions and mechanisms remain largely elusive. Previously, we reported that Pumilio 1 (PUM1), a RBP, could regulate glycolysis metabolism and promote the progression of gastric cancer (GC). However, the role of PUM1 in tumor immune regulation remains largely elusive. In this study, we report that PUM1 induces immune escape through posttranscriptional regulation of PD-L1 in GC. We used multiplexed immunohistochemistry to analyze the correlation between PUM1 expression and immune microenvironment in GC. The effect of PUM1 deficiency on tumor killing of T cells was examined in vitro and in vivo. The molecular mechanism of PUM1 was evaluated via RNA immunoprecipitation, chromatin immunoprecipitation, Western blot, co-immunoprecipitation, and RNA stability assays. Clinically, elevated PUM1 expression is associated with high-expression of PD-L1, lack of CD8+ T cell infiltration and poor prognosis in GC patients. PUM1 positively regulates PD-L1 expression and PUM1 reduction enhances T cell killing of tumors. Mechanistically, PUM1 directly binds to nucleophosmin/nucleoplasmin 3 (NPM3) mRNA and stabilizes NPM3. NPM3 interacts with NPM1 to promote NPM1 translocation into the nucleus and increase the transcription of PD-L1. PUM1 inhibits the anti-tumor activity of T cells through the PUM1/NPM3/PD-L1 axis. In summary, this study reveals the critical post-transcriptional effect of PUM1 in the modulation of PD-L1-dependent GC immune escape, thus provides a novel indicator and potential therapeutic target for cancer immunotherapy.

Pluripotency state transition of embryonic stem cells requires the turnover of histone chaperone FACT on chromatin

The differentiation of embryonic stem cells (ESCs) begins with the transition from the naive to the primed state. The formative state was recently established as a critical intermediate between the two states. Here, we demonstrate the role of the histone chaperone FACT in regulating the naive-to-formative transition. We found that the Q265K mutation in the FACT subunit SSRP1 increased the binding of FACT to histone H3-H4, impaired nucleosome disassembly in vitro, and reduced the turnover of FACT on chromatin in vivo. Strikingly, mouse ESCs harboring this mutation showed elevated naive-to-formative transition. Mechanistically, the SSRP1-Q265K mutation enriched FACT at the enhancers of formative-specific genes to increase targeted gene expression. Together, these findings suggest that the turnover of FACT on chromatin is crucial for regulating the enhancers of formative-specific genes, thereby mediating the naive-to-formative transition. This study highlights the significance of FACT in fine-tuning cell fate transition during early development.

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.

Chemical-genetics refines transcription factor regulatory circuits

Transcriptional dysregulation is a key step in oncogenesis, but our understanding of transcriptional control has relied on genetic approaches that are slow and allow for compensation. Chemical-genetic approaches have shortened the time frame for the analysis of transcription factors from days or weeks to minutes. These studies show that while DNA-binding proteins bind to thousands of sites, they are directly required to regulate only a small cadre of genes. Moreover, these transcriptional control networks are far more distinct, with much less overlap and interconnectivity than predicted from DNA binding. The identified direct targets can then be used to dissect the mechanism of action of these factors, which could identify ways to therapeutically manipulate these oncogenic transcriptional control networks.

Proteomics analysis identifies the ribosome associated coiled-coil domain-containing protein-124 as a novel interaction partner of nucleophosmin-1

BACKGROUND INFORMATION

Coiled-coil domain-containing protein-124 (Ccdc124) is a conserved eukaryotic ribosome-associated RNA-binding protein which is involved in resuming ribosome activity after stress-related translational shutdown. Ccdc124 protein is also detected at cellular localizations devoid of ribosomes, such as the centrosome, or the cytokinetic midbody, but its translation-independent cellular function is currently unknown.

RESULTS

By using an unbiased LC-MS/MS-based proteomics approach in human embryonic kidney (HEK293) cells, we identified novel Ccdc124 partners and mapped the cellular organization of interacting proteins, a subset of which are known to be involved in nucleoli biogenesis and function. We then identified a novel interaction between the cancer-associated multifunctional nucleolar marker nucleophosmin (Npm1) and Ccdc124, and we characterized this interaction both in HEK293 (human embryonic kidney) and U2OS (osteosarcoma) cells. As expected, in both types of cells, Npm1 and Ccdc124 proteins colocalized within the nucleolus when assayed by immunocytochemical methods, or by monitoring the localization of green fluorescent protein-tagged Ccdc124.

CONCLUSIONS

The nucleolar localization of Ccdc124 was impaired when Npm1 translocates from the nucleolus to the nucleoplasm in response to treatment with the DNA-intercalator and Topo2 inhibitor chemotherapeutic drug doxorubicin. Npm1 is critically involved in maintaining genomic stability by mediating various DNA-repair pathways, and over-expression of Npm1 or specific NPM1 mutations have been previously associated with proliferative diseases, such as acute myelogenous leukemia, anaplastic large-cell lymphoma, and solid cancers originating from different tissues.

SIGNIFICANCE

Identification of Ccdc124 as a novel interaction partner of Nmp1 within the frame of molecular mechanisms involving nucleolar stress-sensing and DNA-damage response is expected to provide novel insights into the biology of cancers associated with aberrations in NPM1.

Temporal recording of mammalian development and precancer

Key to understanding many biological phenomena is knowing the temporal ordering of cellular events, which often require continuous direct observations [1, 2]. An alternative solution involves the utilization of irreversible genetic changes, such as naturally occurring mutations, to create indelible markers that enables retrospective temporal ordering [3-8]. Using NSC-seq, a newly designed and validated multi-purpose single-cell CRISPR platform, we developed a molecular clock approach to record the timing of cellular events and clonality in vivo , while incorporating assigned cell state and lineage information. Using this approach, we uncovered precise timing of tissue-specific cell expansion during murine embryonic development and identified new intestinal epithelial progenitor states by their unique genetic histories. NSC-seq analysis of murine adenomas and single-cell multi-omic profiling of human precancers as part of the Human Tumor Atlas Network (HTAN), including 116 scRNA-seq datasets and clonal analysis of 418 human polyps, demonstrated the occurrence of polyancestral initiation in 15-30% of colonic precancers, revealing their origins from multiple normal founders. Thus, our multimodal framework augments existing single-cell analyses and lays the foundation for in vivo multimodal recording, enabling the tracking of lineage and temporal events during development and tumorigenesis.

Phosphoproteome analysis of the crosstalk between sumoylation and phosphorylation in mouse spermatocytes

Spermatogenesis is supported by various posttranslational modifications. There is growing evidence supporting a crosstalk between sumoylation and phosphorylation in different cell types. We have recently shown that inhibition of global sumoylation with a sumoylation inhibitor (Ginkgolic acid, GA) arrested purified mouse spermatocytes in vitro; the spermatocytes could not condense chromatin and disassemble the synaptonemal complex. Our data have also revealed that some kinases regulating the meiotic prophase (PLK1 and AURKB) were inhibited upon the inhibition of sumoylation. Nevertheless, specific phosphorylated targets affected by the inhibition of sumoylation have not been identified. To address this gap, in this study, we performed a comparative phospho-proteome analysis of the control spermatocytes and spermatocytes treated with the GA. Our analysis has narrowed down to several proteins implicated in the regulation of cell cycle and/or meiosis. Two of these targets, NPM1 and hnRNPH1, were studied further using western blotting in both cell lines and primary cells. Decrease in sumoylaion-dependend phosphorylation of NPM1 on Ser125 regulated by AURKB can be a contributing factor to the inability of spermatocytes to condense chromatin by the end of the prophase and should be studied further.

The stability of NPM1 oligomers regulated by acidic disordered regions controls the quality of liquid droplets

The nucleolus is a membrane-less nuclear body that typically forms through the process of liquid-liquid phase separation (LLPS) involving its components. NPM1 drives LLPS within the nucleolus and its oligomer formation and inter-oligomer interactions play a cooperative role in inducing LLPS. However, the molecular mechanism underlaying the regulation of liquid droplet quality formed by NPM1 remains poorly understood. In this study, we demonstrate that the N-terminal and central acidic residues within the intrinsically disordered regions (IDR) of NPM1 contribute to attenuating oligomer stability, although differences in the oligomer stability were observed only under stringent conditions. Furthermore, the impact of the IDRs is augmented by an increase in net negative charges resulting from phosphorylation within the IDRs. Significantly, we observed an increase in fluidity of liquid droplets formed by NPM1 with decreased oligomer stability. These results indicate that the difference in oligomer stability only observed biochemically under stringent conditions has a significant impact on liquid droplet quality formed by NPM1. Our findings provide new mechanistic insights into the regulation of nucleolar dynamics during the cell cycle.

Lineage skewing and genome instability underlie marrow failure in a zebrafish model of GATA2 deficiency

Inherited bone marrow failure associated with heterozygous mutations in GATA2 predisposes toward hematological malignancies, but the mechanisms remain poorly understood. Here, we investigate the mechanistic basis of marrow failure in a zebrafish model of GATA2 deficiency. Single-cell transcriptomics and chromatin accessibility assays reveal that loss of gata2a leads to skewing toward the erythroid lineage at the expense of myeloid cells, associated with loss of cebpa expression and decreased PU.1 and CEBPA transcription factor accessibility in hematopoietic stem and progenitor cells (HSPCs). Furthermore, gata2a mutants show impaired expression of npm1a, the zebrafish NPM1 ortholog. Progressive loss of npm1a in HSPCs is associated with elevated levels of DNA damage in gata2a mutants. Thus, Gata2a maintains myeloid lineage priming through cebpa and protects against genome instability and marrow failure by maintaining expression of npm1a. Our results establish a potential mechanism underlying bone marrow failure in GATA2 deficiency.

Single-Cell RNA Sequencing of Sox17-Expressing Lineages Reveals Distinct Gene Regulatory Networks and Dynamic Developmental Trajectories

During early embryogenesis, the transcription factor SOX17 contributes to hepato-pancreato-biliary system formation and vascular-hematopoietic emergence. To better understand Sox17 function in the developing endoderm and endothelium, we developed a dual-color temporal lineage-tracing strategy in mice combined with single-cell RNA sequencing to analyze 6934 cells from Sox17-expressing lineages at embryonic days 9.0-9.5. Our analyses showed 19 distinct cellular clusters combined from all 3 germ layers. Differential gene expression, trajectory and RNA-velocity analyses of endothelial cells revealed a heterogenous population of uncommitted and specialized endothelial subtypes, including 2 hemogenic populations that arise from different origins. Similarly, analyses of posterior foregut endoderm revealed subsets of hepatic, pancreatic, and biliary progenitors with overlapping developmental potency. Calculated gene-regulatory networks predict gene regulons that are dominated by cell type-specific transcription factors unique to each lineage. Vastly different Sox17 regulons found in endoderm versus endothelial cells support the differential interactions of SOX17 with other regulatory factors thereby enabling lineage-specific regulatory actions.

NPM3 as a novel oncogenic factor and poor prognostic marker contributes to cell proliferation and migration in lung adenocarcinoma

BACKGROUND

Lung cancer is the leading cause of cancer-related deaths worldwide, and despite recent advances in targeted therapies and immunotherapies, the clinical benefit remains limited. Therefore, there is an urgent need to further investigate the molecular mechanisms underlying lung cancer. The aim of this study was to investigate the expression and function of NPM3 in the tumor microenvironment of lung adenocarcinoma (LUAD).

METHODS

We utilized bioinformatics tools and databases, including UALCAN, GEPIA2, HPA, and Sangerbox, to analyze NPM3 expression in LUAD samples and its association with prognosis and mutational landscape. NPM3 expression in various cell types was assessed at the single cell level using the TISCH database. We also used algorithms such as TIMER and EPIC to explore the crosstalk between NPM3 expression and immune features. KEGG enrichment analysis was performed to identify potential signaling pathways of NPM3. Finally, we employed siRNA knockdown strategy to investigate the effect of NPM3 on LUAD cell proliferation and migration in vitro.

RESULTS

NPM3 was significantly upregulated in LUAD tissues and was strongly associated with poor prognosis and TP53 gene mutations. Single-cell sequencing analysis revealed that NPM3 was expressed in immune cells (dendritic cells and monocytes/macrophages) in the tumor microenvironment. Moreover, NPM3 expression was negatively associated with immune B cell and CD4 T cell infiltration, as well as with several immune-related genes (including CCL22, CXCR2, CX3CR1, CCR6, HLA-DOA, HLA-DQA2). KEGG enrichment analysis indicated that NPM3 expression was associated with cell cycle, CAMs, and NSCLC pathway genes. Finally, in vitro experiments showed that NPM3 knockdown inhibited LUAD cell proliferation and migration in NCI-H1299 and SPC-A1 cells, and suppressed the expression of CCNA2 and MAD2L1.

CONCLUSION

Elevated NPM3 expression predicts poor clinical outcome and an immunosuppressive microenvironment in LUAD tissues. NPM3 promotes LUAD progression by promoting cell proliferation and migration, and targeting NPM3 may represent a novel therapeutic strategy for LUAD.

Updates in molecular genetics of acute myeloid leukemia

Acute myeloid leukemia (AML) is a type of cancer caused by aggressive neoplastic proliferations of immature myeloid cells that is fatal if untreated. AML accounts for 1.0% of all new cancer cases in the United States, with a 5-year relative survival rate of 30.5%. Once defined primarily morphologically, advances in next generational sequencing have expanded the role of molecular genetics in categorizing the disease. As such, both the World Health Organization Classification of Haematopoietic Neoplasms and The International Consensus Classification System now define a variety of AML subsets based on mutations in driver genes such as NPM1, CEBPA, TP53, ASXL1, BCOR, EZH2, RUNX1, SF3B1, SRSF2, STAG2, U2AF1, and ZRSR2. This article provides an overview of some of the genetic mutations associated with AML and compares how the new classification systems incorporate molecular genetics into the definition of AML.

NPM1-Mutated Acute Myeloid Leukemia: Recent Developments and Open Questions

Somatic mutations in the nucleophosmin (NPM1) gene occur in approximately 30% of de novo acute myeloid leukemias (AMLs) and are relatively enriched in normal karyotype AMLs. Earlier World Health Organization (WHO) classification schema recognized NPM1-mutated AMLs as a unique subtype of AML, while the latest WHO and International Consensus Classification (ICC) now consider NPM1 mutations as AML-defining, albeit at different blast count thresholds. NPM1 mutational load correlates closely with disease status, particularly in the post-therapy setting, and therefore high sensitivity-based methods for detection of the mutant allele have proven useful for minimal/measurable residual disease (MRD) monitoring. MRD status has been conventionally measured by either multiparameter flow cytometry (MFC) and/or molecular diagnostic techniques, although recent data suggest that MFC data may be potentially more challenging to interpret in this AML subtype. Of note, MRD status does not predict patient outcome in all cases, and therefore a deeper understanding of the biological significance of MRD may be required. Recent studies have confirmed that NPM1-mutated cells rely on overexpression of HOX/MEIS1, which is dependent on the presence of the aberrant cytoplasmic localization of mutant NPM1 protein (NPM1c); this biology may explain the promising response to novel agents, including menin inhibitors and second-generation XPO1 inhibitors. In this review, these and other recent developments around NPM1-mutated AML, in addition to open questions warranting further investigation, will be discussed.

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.

NPM 1 Mutations in AML-The Landscape in 2023

Acute myeloid leukemia (AML) represents 80% of acute leukemia in adults and is characterized by clonal expansion of hematopoietic stem cells secondary to genomic mutations, rendering a selective growth advantage to the mutant clones. NPM1mut is found in around 30% of AML and clinically presents with leukocytosis, high blast percentage and extramedullary involvement. Considered as a "gate-keeper" mutation, NPM1mut appears to be a "first hit" in the process of leukemogenesis and development of overt leukemia. Commonly associated with other mutations (e.g., FLT 3, DNMT3A, TET2, SF3B1), NPM1 mutation in AML has an important role in diagnosis, prognosis, treatment and post-treatment monitoring. Several novel therapies targeting NPM1 are being developed in various clinical phases with demonstration of efficacy. In this review, we summarize the pathophysiology of the NPM1 gene mutation in AML, clinical implications and the novel targeted therapies to date.

Titanium dioxide nanoparticles affect osteoblast-derived exosome cargos and impair osteogenic differentiation of human mesenchymal stem cells

Titanium (Ti) and its alloys are the most widely used metallic biomaterials in total joint replacement; however, increasing evidence supports the degradation of its surface due to corrosion and wear processes releasing debris (ions, and micro and nanoparticles) and contribute to particle-induced osteolysis and implant loosening. Cell-to-cell communication involving several cell types is one of the major biological processes occurring during bone healing and regeneration at the implant-bone interface. In addition to the internal response of cells to the uptake and intracellular localization of wear debris, a red flag is the ability of titanium dioxide nanoparticles (mimicking wear debris) to alter cellular communication with the tissue background, disturbing the balance between osseous tissue integrity and bone regenerative processes. This study aims to understand whether titanium dioxide nanoparticles (TiO₂ NPs) alter osteoblast-derived exosome (Exo) biogenesis and whether exosomal protein cargos affect the communication of osteoblasts with human mesenchymal stem/stromal cells (HMSCs). Osteoblasts are derived from mesenchymal stem cells coexisting in the bone microenvironment during development and remodelling. We observed that TiO₂ NPs stimulate immature osteoblast- and mature osteoblast-derived Exo secretion that present a distinct proteomic cargo. Functional tests confirmed that Exos derived from both osteoblasts decrease the osteogenic differentiation of HMSCs. These findings are clinically relevant since wear debris alter extracellular communication in the bone periprosthetic niche, contributing to particle-induced osteolysis and consequent prosthetic joint failure.

Update on current treatments for adult acute myeloid leukemia: to treat acute myeloid leukemia intensively or non-intensively? That is the question

For several decades, the treatment for acute myeloid leukemia (AML) has been a dichotomous choice between intensive chemotherapy strategies with curative intent and non-intensive options including supportive care. Patients' age and fitness, as well as comorbidities, primarily influenced this choice. However, the therapeutic armamentarium is evolving, so that there are highly effective and increasingly specific drugs, fitting the mutational profile of a patient's leukemia. There is now a spectrum of treatment options that are less intense and can be administered in an outpatient setting and to a substantial extent are equally or even more effective than standard intensive therapy. We are, therefore, witnessing a radical change in the treatment landscape of AML. In this review, we examine the current treatment options for patients with AML, considering the molecular spectrum of the disease on the background of patient-related factors.

Alterations of cohesin complex genes in acute myeloid leukemia: differential co-mutations, clinical presentation and impact on outcome

Functional perturbations of the cohesin complex with subsequent changes in chromatin structure and replication are reported in a multitude of cancers including acute myeloid leukemia (AML). Mutations of its STAG2 subunit may predict unfavorable risk as recognized by the 2022 European Leukemia Net recommendations, but the underlying evidence is limited by small sample sizes and conflicting observations regarding clinical outcomes, as well as scarce information on other cohesion complex subunits. We retrospectively analyzed data from a multi-center cohort of 1615 intensively treated AML patients and identified distinct co-mutational patters for mutations of STAG2, which were associated with normal karyotypes (NK) and concomitant mutations in IDH2, RUNX1, BCOR, ASXL1, and SRSF2. Mutated RAD21 was associated with NK, mutated EZH2, KRAS, CBL, and NPM1. Patients harboring mutated STAG2 were older and presented with decreased white blood cell, bone marrow and peripheral blood blast counts. Overall, neither mutated STAG2, RAD21, SMC1A nor SMC3 displayed any significant, independent effect on clinical outcomes defined as complete remission, event-free, relapse-free or overall survival. However, we found almost complete mutual exclusivity of genetic alterations of individual cohesin subunits. This mutual exclusivity may be the basis for therapeutic strategies via synthetic lethality in cohesin mutated AML.

Cytoplasmic Expression of TP53INP2 Modulated by Demethylase FTO and Mutant NPM1 Promotes Autophagy in Leukemia Cells

Acute myeloid leukemia (AML) with a nucleophosmin 1 (NPM1) mutation is a unique subtype of adult leukemia. Recent studies show that NPM1-mutated AML has high autophagy activity. However, the mechanism for upholding the high autophagic level is still not fully elucidated. In this study, we first identified that tumor protein p53 inducible nuclear protein 2 (TP53INP2) was highly expressed and cytoplasmically localized in NPM1-mutated AML cells. Subsequent data showed that the expression of TP53INP2 was upregulated by fat mass and obesity-associated protein (FTO)-mediated m⁶A modification. Meanwhile, TP53INP2 was delocalized to the cytoplasm by interacting with NPM1 mutants. Functionally, cytoplasmic TP53INP2 enhanced autophagy activity by promoting the interaction of microtubule-associated protein 1 light chain 3 (LC3) - autophagy-related 7 (ATG7) and further facilitated the survival of leukemia cells. Taken together, our study indicates that TP53INP2 plays an oncogenic role in maintaining the high autophagy activity of NPM1-mutated AML and provides further insight into autophagy-targeted therapy of this leukemia subtype.

A research review of experimental animal models with myelodysplastic syndrome

Myelodysplastic syndrome (MDS) consists of a group of hematologic tumors that are derived from the clonal proliferation of hematopoietic stem cells, featuring abnormal hematopoietic cell development and ineffective hematopoiesis. Animal models are an important scientific research platform that has been widely applied in the research of human diseases, especially tumors. Animal models with MDS can simulate characteristic human genetic variations and tumor phenotypes. They also provide a reliable platform for the exploration of the pathogenesis and diagnostic markers of MDS as well as for a drug efficacy evaluation. This paper reviews the research status of three animal models and a new spontaneous mouse model with MDS.

The role of the nucleolus in regulating the cell cycle and the DNA damage response

The nucleolus has long been perceived as the site for ribosome biogenesis, but numerous studies suggest that the nucleolus carefully sequesters crucial proteins involved in multiple cellular functions. Among these, the role of nucleolus in cell cycle regulation is the most evident. The nucleolus is the first responder of growth-related signals to mediate normal cell cycle progression. The nucleolus also senses different cellular stress insults by activating diverse pathways that arrest the cell cycle, promote DNA repair, or initiate apoptosis. Here, we review the emerging concepts on how the ribosomal and nonribosomal nucleolar proteins mediate such cellular effects.

Loss of NPM2 expression is a potential immunohistochemical marker for malignant peritoneal mesothelioma: a single-center study of 92 cases

Background

Malignant peritoneal mesothelioma (MPM) is a rare malignant tumor with a high mortality rate and extremely poor prognosis. In-depth pathological analysis is essential to assess tumor biological behaviors and explore potential therapeutic targets of MPM. Nucleoplasmin 2 (NPM2) is a molecular chaperone that binds histones and may play a key role in the development and progression of tumors. This study aimed to analyze the correlation between the expression level of NPM2 and the main clinicopathological characteristics and prognosis of MPM.

Methods

Ninety-two postoperative specimens from MPM patients following cytoreductive surgery were collected. Postoperative specimens were stained with immunohistochemistry. The expression level of NPM2 was quantitatively analyzed by QuPath-0.3.2 software. Univariate and multivariate analyses were conducted to investigate the correlation between NPM2 expression and other conventional clinicopathological characteristics.

Results

Among the 92 MPM patients, there were 47 males (48.9%) and 45 females (51.1%), with a median age of 56 (range: 24–73). There were 70 (76.0%) cases with loss of NPM2 protein expression, 11 (12.0%) cases with low expression, and 11 (12.0%) cases with high expression. Univariate analysis showed that NPM2 protein expression level (negative vs. low expression vs. high expression) was negatively correlated with the following three clinicopathological factors: completeness of cytoreduction (CC) score, vascular tumor emboli, and serious adverse events (SAEs) (all P < 0.05). Multivariate analysis showed that NPM2 protein expression level (negative vs. low expression vs. high expression) was independently negatively correlated with the following two clinicopathological factors: CC score [odds ratio (OR) = 0.317, 95% CI: 0.317–0.959, P = 0.042] and vascular tumor emboli (OR = 0.092, 95% CI = 0.011–0.770, P = 0.028). Survival analysis showed that loss of NPM2 protein expression (negative vs. positive) was associated with poor prognosis of MPM.

Conclusions

Loss of NPM2 expression is a potential immunohistochemical marker for MPM.

NPM1 promotes cell proliferation by targeting PRDX6 in colorectal cancer

Colorectal cancer is a malignant tumor that begins in the colorectal mucosal epithelium. NPM1 is a nucleolar phosphoprotein that has been linked to tumor progression in humans. NPM1 is significantly overexpressed in a variety of tumors, including colorectal cancer, but its role and mechanism in colorectal cancer remain unknown. Therefore, the purpose of this study was to discover the role of NPM1 in promoting colorectal cancer proliferation via PRDX6 and its molecular mechanism. NPM1 knockdown or overexpression inhibited or promoted the proliferation and cell cycle progression of HCT-116 and HT-29 colorectal cancer cells, respectively, according to our findings. Furthermore, NPM1 knockdown or overexpression increased or decreased intracellular ROS levels. Animal experiments revealed that NPM1 knockdown or overexpression inhibited or promoted the growth of colorectal cancer cells transplanted subcutaneously. NPM1 knockdown or overexpression reduced or increased PRDX6 expression and related enzyme activities, respectively, according to our findings. NPM1 formed a complex with CBX3 as evidenced by immunoprecipitation, and the double luciferase reporter gene assay confirmed that the CBX3-NPM1 complex promoted PRDX6 transcription. Our data support the role of NPM1 in promoting the proliferation of colorectal cancer, which may be accomplished by CBX3 promoting the expression of the antioxidant protein PRDX6 and thus inhibiting intracellular ROS levels. NPM1 and PRDX6 are potential colorectal cancer therapeutic targets.

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.

Inheritance of repressed chromatin domains during S phase requires the histone chaperone NPM1

The epigenetic process safeguards cell identity during cell division through the inheritance of appropriate gene expression profiles. We demonstrated previously that parental nucleosomes are inherited by the same chromatin domains during DNA replication only in the case of repressed chromatin. We now show that this specificity is conveyed by NPM1, a histone H3/H4 chaperone. Proteomic analyses of late S-phase chromatin revealed NPM1 in association with both H3K27me3, an integral component of facultative heterochromatin, and MCM2, an integral component of the DNA replication machinery; moreover, NPM1 interacts directly with PRC2 and with MCM2. Given that NPM1 is essential, the inheritance of repressed chromatin domains was examined anew using mESCs expressing an auxin-degradable version of endogenous NPM1. Upon NPM1 degradation, cells accumulated in the G₁-S phase of the cell cycle and parental nucleosome inheritance from repressed chromatin domains was markedly compromised. NPM1 chaperone activity may contribute to the integrity of this process as appropriate inheritance required the NPM1 acidic patches.

The Coming of Age of Preclinical Models of MDS

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal bone-marrow diseases with ineffective hematopoiesis resulting in cytopenias and morphologic dysplasia of hematopoietic cells. MDS carry a wide spectrum of genetic abnormalities, ranging from chromosomal abnormalities such as deletions/additions, to recurrent mutations affecting the spliceosome, epigenetic modifiers, or transcription factors. As opposed to AML, research in MDS has been hindered by the lack of preclinical models that faithfully replicate the complexity of the disease and capture the heterogeneity. The complex molecular landscape of the disease poses a unique challenge when creating transgenic mouse-models. In addition, primary MDS cells are difficult to manipulate ex vivo limiting in vitro studies and resulting in a paucity of cell lines and patient derived xenograft models. In recent years, progress has been made in the development of both transgenic and xenograft murine models advancing our understanding of individual contributors to MDS pathology as well as the complex primary interplay of genetic and microenvironment aberrations. We here present a comprehensive review of these transgenic and xenograft models for MDS and future directions.

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.

NPM1 ablation induces HSC aging and inflammation to develop myelodysplastic syndrome exacerbated by p53 loss

Myelodysplastic syndrome (MDS) is characterized by ineffective hematopoiesis with morphologic dysplasia and a propensity to transform into overt acute myeloid leukemia (AML). Our analysis of two cohorts of 20 MDS and 49 AML with multi-lineage dysplasia patients shows a reduction in Nucleophosmin 1 (NPM1) expression in 70% and 90% of cases, respectively. A mouse model of Npm1 conditional knockout (cKO) in hematopoietic cells reveals that Npm1 loss causes premature aging of hematopoietic stem cells (HSCs). Mitochondrial activation in Npm1-deficient HSCs leads to aberrant activation of the NLRP3 inflammasome, which correlates with a developing MDS-like phenotype. Npm1 cKO mice exhibit shortened survival times, and expansion of both the intra- and extra-medullary myeloid populations, while evoking a p53-dependent response. After transfer into a p53 mutant background, the resulting Npm1/p53 double KO mice develop fatal leukemia within 6 months. Our findings identify NPM1 as a regulator of HSC aging and inflammation and highlight the role of p53 in MDS progression to leukemia.

The Role of Nucleophosmin 1 (NPM1) Mutation in the Diagnosis and Management of Myeloid Neoplasms

Nucleophosmin (NPM1) is a multifunctional protein with both proliferative and growth-suppressive roles in the cell. In humans, NPM1 is involved in tumorigenesis via chromosomal translocations, deletions, or mutation. Acute myeloid leukemia (AML) with mutated NPM1, a distinct diagnostic entity by the current WHO Classification of myeloid neoplasm, represents the most common diagnostic subtype in AML and is associated with a favorable prognosis. The persistence of NPM1 mutation in AML at relapse makes this mutation an ideal target for minimal measurable disease (MRD) detection. The clinical implication of this is far-reaching because NPM1-mutated AML is currently classified as being of standard risk, with the best treatment strategy (transplantation versus chemotherapy) yet undefined. Myeloid neoplasms with NPM1 mutations and <20% blasts are characterized by an aggressive clinical course and a rapid progression to AML. The pathological classification of these cases remains controversial. Future studies will determine whether NPM1 gene mutation may be sufficient for diagnosing NPM1-mutated AML independent of the blast count. This review aims to summarize the role of NPM1 in normal cells and in human cancer and discusses its current role in clinical management of AML and related myeloid neoplasms.

Mouse Models of Frequently Mutated Genes in Acute Myeloid Leukemia

Acute myeloid leukemia is a clinically and biologically heterogeneous blood cancer with variable prognosis and response to conventional therapies. Comprehensive sequencing enabled the discovery of recurrent mutations and chromosomal aberrations in AML. Mouse models are essential to study the biological function of these genes and to identify relevant drug targets. This comprehensive review describes the evidence currently available from mouse models for the leukemogenic function of mutations in seven functional gene groups: cell signaling genes, epigenetic modifier genes, nucleophosmin 1 (NPM1), transcription factors, tumor suppressors, spliceosome genes, and cohesin complex genes. Additionally, we provide a synergy map of frequently cooperating mutations in AML development and correlate prognosis of these mutations with leukemogenicity in mouse models to better understand the co-dependence of mutations in AML.

Biological Effects of BET Inhibition by OTX015 (MK-8628) and JQ1 in NPM1-Mutated (NPM1c) Acute Myeloid Leukemia (AML)

BET inhibitors (BETi) including OTX015 (MK-8628) and JQ1 demonstrated antileukemic activity including NPM1c AML cells. Nevertheless, the biological consequences of BETi in NPM1c AML were not fully investigated. Even if of better prognosis AML patients with NPM1c may relapse and treatment remains difficult. Differentiation-based therapy by all trans retinoic acid (ATRA) combined with arsenic trioxide (ATO) demonstrated activity in NPM1c AML. We found that BETi, similar to ATO + ATRA, induced differentiation and apoptosis which was TP53 independent in the NPM1c cell line OCI-AML3 and primary cells. Furthermore, BETi induced proteasome-dependent degradation of NPM1c. BETi degraded NPM1c in the cytosol while BRD4 is degraded in the nucleus which suggests that restoration of the NPM1/BRD4 equilibrium in the nucleus of NPM1c cells is essential for the efficacy of BETi. While ATO + ATRA had significant biological activity in NPM1c IMS-M2 cell line, those cells were resistant to BETi. Gene profiling revealed that IMS-M2 cells probably resist to BETi by upregulation of LSC pathways independently of the downregulation of a core BET-responsive transcriptional program. ATO + ATRA downregulated a NPM1c specific HOX gene signature while anti-leukemic effects of BETi appear HOX gene independent. Our preclinical results encourage clinical testing of BETi in NPM1c AML patients.

Zebrafish models of acute leukemias: Current models and future directions

Acute myeloid leukemias (AML) and acute lymphoid leukemias (ALL) are heterogenous diseases encompassing a wide array of genetic mutations with both loss and gain of function phenotypes. Ultimately, these both result in the clonal overgrowth of blast cells in the bone marrow, peripheral blood, and other tissues. As a consequence of this, normal hematopoietic stem cell function is severely hampered. Technologies allowing for the early detection of genetic alterations and understanding of these varied molecular pathologies have helped to advance our treatment regimens toward personalized targeted therapies. In spite of this, both AML and ALL continue to be a major cause of morbidity and mortality worldwide, in part because molecular therapies for the plethora of genetic abnormalities have not been developed. This underscores the current need for better model systems for therapy development. This article reviews the current zebrafish models of AML and ALL and discusses how novel gene editing tools can be implemented to generate better models of acute leukemias. This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Stem Cells and Disease Technologies > Perturbing Genes and Generating Modified Animals.

Single-beam multimodal nonlinear-optical imaging of structurally complex events in cell-cycle dynamics

We demonstrate a multimodal nonlinear-optical imaging that combines second- and third-harmonic generation (SHG and THG) with three-photon-excited fluorescence (3PEF) as a means to resolve fine details of the cell structure and trace its transformations throughout structurally complex episodes of cell-cycle dynamics, including the key stages and signatures in cell division. When zoomed in on cell mitosis, this technique enables a high-contrast multimodal imaging of intra- and extracellular signatures of cell division, detecting, via a multiplex, 3PEF/SHG/THG readout, a remarkable diversity of shapes, sizes, and symmetries in a truly single-beam setting, with no need for beam refocusing or field-waveform re-adjustment.

Significance of NPM1 Gene Mutations in AML

The aim of this literature review is to examine the significance of the nucleophosmin 1 (NPM1) gene in acute myeloid leukaemia (AML). This will include analysis of the structure and normal cellular function of NPM1, the type of mutations commonly witnessed in NPM1, and the mechanism by which this influences the development and progression of AML. The importance of NPM1 mutation on prognosis and the treatment options available to patients will also be reviewed along with current guidelines recommending the rapid return of NPM1 mutational screening results and the importance of employing a suitable laboratory assay to achieve this. Finally, future developments in the field including research into new therapies targeting NPM1 mutated AML are considered.

A Curious Novel Combination of Nucleophosmin (NPM1) Gene Mutations Leading to Aberrant Cytoplasmic Dislocation of NPM1 in Acute Myeloid Leukemia (AML)

Nucleophosmin (NPM1) mutations occurring in acute myeloid leukemia (AML) (about 50 so far identified) cluster almost exclusively in exon 12 and lead to common changes at the NPM1 mutants C-terminus, i.e., loss of tryptophans 288 and 290 (or 290 alone) and creation of a new nuclear export signal (NES), at the bases of exportin-1(XPO1)-mediated aberrant cytoplasmic NPM1. Immunohistochemistry (IHC) detects cytoplasmic NPM1 and is predictive of the molecular alteration. Besides IHC and molecular sequencing, Western blotting (WB) with anti-NPM1 mutant specific antibodies is another approach to identify NPM1-mutated AML. Here, we show that among 382 AML cases with NPM1 exon 12 mutations, one was not recognized by WB, and describe the discovery of a novel combination of two mutations involving exon 12. This appeared as a conventional mutation A with the known TCTG nucleotides insertion/duplication accompanied by a second event (i.e., an 8-nucleotide deletion occurring 15 nucleotides downstream of the TCTG insertion), resulting in a new C-terminal protein sequence. Strikingly, the sequence included a functional NES ensuring cytoplasmic relocation of the new mutant supporting the role of cytoplasmic NPM1 as critical in AML leukemogenesis.

The Prevalence and Prognostic Impacts of Nucleophosmin Mutations in Adult Patients with De Novo Acute Myeloid Leukemia

BACKGROUND: Acute myeloid leukemia (AML) is known as cancer of the blood and bone marrow (BM) and is regarded as the commonest acute leukemia in adult patients. AIM: In this study, the aim to investigate the nucleophosmin mutations and their prognostic impacts in patients that were recently diagnosed with AML. METHODS: We have included patients who were newly diagnosed with AML and presented to the medical oncology clinics, National Cancer Institute, Cairo University, during the period from August 2016 to December 2018. To assess the laboratory and hematological outcomes of our patients, total RNA was extracted from BM and converted to cDNA then the expression of nucleophosmin 1 (NPM1) type A mutation was done by real-time quantitative polymerase chain reaction (PCR). Comparative analysis was also conducted to study outcomes between the gene mutation groups. RESULTS: We have included 89 AML patients in our study with a median age of 43 years (18–77). NPM1 gene mutation was detected in 37.1% of our patients by conventional PCR technique and agarose gel electrophoresis, of which 18% were NPM1 type A mutation. No significant differences were noticed between our patients based on their NPM1 gene mutation status (wild and mutant) in terms of sex, hepatomegaly, splenomegaly, and complete remission (CR). Lymphadenopathy was the only significant factor (p = 0.023). Surprisingly we found 9/33 patients had NPM1 mutation with recurrent cytogenetic abnormality. We found no statistical significance between mutation A and mutation non-A groups in any of the studied outcomes as sex, clinical and laboratory data, and CR. CONCLUSION: NPM1 gene mutation A was relatively low among our population but did not significantly affect the outcomes.

Ribosomal L1 domain-containing protein 1 coordinates with HDM2 to negatively regulate p53 in human colorectal Cancer cells

BACKGROUND

Ribosomal L1 domain-containing protein 1 (RSL1D1) is a nucleolar protein that is essential in cell proliferation. In the current opinion, RSL1D1 translocates to the nucleoplasm under nucleolar stress and inhibits the E3 ligase activity of HDM2 via direct interaction, thereby leading to stabilization of p53.

METHODS

Gene knockdown was achieved in HCT116^p53+/+, HCT116^p53-/-, and HCT-8 human colorectal cancer (CRC) cells by siRNA transfection. A lentiviral expression system was used to establish cell strains overexpressing genes of interest. The mRNA and protein levels in cells were evaluated by qRT-PCR and western blot analyses. Cell proliferation, cell cycle, and cell apoptosis were determined by MTT, PI staining, and Annexin V-FITC/PI double staining assays, respectively. The level of ubiquitinated p53 protein was assessed by IP. The protein-RNA interaction was investigated by RIP. The subcellular localization of proteins of interest was determined by IFA. Protein-protein interaction was investigated by GST-pulldown, BiFC, and co-IP assays. The therapeutic efficacy of RSL1D1 silencing on tumor growth was evaluated in HCT116 tumor-bearing nude mice.

RESULTS

RSL1D1 distributed throughout the nucleus in human CRC cells. Silencing of RSL1D1 gene induced cell cycle arrest at G1/S and cell apoptosis in a p53-dependent manner. RSL1D1 directly interacted with and recruited p53 to HDM2 to form a ternary RSL1D1/HDM2/p53 protein complex and thereby enhanced p53 ubiquitination and degradation, leading to a decrease in the protein level of p53. Destruction of the ternary complex increased the level of p53 protein. RSL1D1 also indirectly decreased the protein level of p53 by stabilizing HDM2 mRNA. Consequently, the negative regulation of p53 by RSL1D1 facilitated cell proliferation and survival and downregulation of RSL1D1 remarkably inhibited the growth of HCT116^p53+/+ tumors in a nude mouse model.

CONCLUSION

We report, for the first time, that RSL1D1 is a novel negative regulator of p53 in human CRC cells and more importantly, a potential molecular target for anticancer drug development.

Multimodal nonlinear-optical imaging of nucleoli

Multimodal nonlinear microscopy combining third-harmonic generation (THG) with two- and three-photon-excited fluorescence (2PEF and 3PEF) is shown to provide a powerful resource for high-fidelity imaging of nucleoli and nucleolar proteins. We demonstrate that, with a suitably tailored genetically encoded fluorescent stain, the 2PEF/3PEF readout from specific nucleolar proteins can be reliably detected against the extranucleolar 2PEF/3PEF signal, enabling high-contrast imaging of the key nucleolar ribosome biogenesis components, such as fibrillarin. THG is shown to provide a versatile readout for unstained nucleolus imaging in a vast class of biological systems as different as neurons in brain slices and cultured HeLa cells.

NPM1 Is a Prognostic Biomarker Involved in Immune Infiltration of Lung Adenocarcinoma and Associated With m6A Modification and Glycolysis

Background

Overexpression of NPM1 can promote the growth and proliferation of various tumor cells. However, there are few studies on the comprehensive analysis of NPM1 in lung adenocarcinoma (LUAD).

Methods

TCGA and GEO data sets were used to analyze the expression of NPM1 in LUAD and clinicopathological analysis. The GO/KEGG enrichment analysis of NPM1 co-expression and gene set enrichment analysis (GSEA) were performed using R software package. The relationship between NPM1 expression and LUAD immune infiltration was analyzed using TIMER, GEPIA database and TCGA data sets, and the relationship between NPM1 expression level and LUAD m6A modification and glycolysis was analyzed using TCGA and GEO data sets.

Results

NPM1 was overexpressed in a variety of tumors including LUAD, and the ROC curve showed that NPM1 had a certain accuracy in predicting the outcome of tumors and normal samples. The expression level of NPM1 in LUAD is significantly related to tumor stage and prognosis. The GO/KEGG enrichment analysis indicated that NPM1 was closely related to translational initiation, ribosome, structural constituent of ribosome, ribosome, Parkinson disease, and RNA transport. GSEA showed that the main enrichment pathway of NPM1-related differential genes was mainly related to mTORC1 mediated signaling, p53 hypoxia pathway, signaling by EGFR in cancer, antigen activates B cell receptor BCR leading to generation of second messengers, aerobic glycolysis and methylation pathways. The analysis of TIMER, GEPIA database and TCGA data sets showed that the expression level of NPM1 was negatively correlated with B cells and NK cells. The TCGA and GEO data sets analysis indicated that the NPM1 expression was significantly correlated with one m6A modifier related gene (HNRNPC) and five glycolysis related genes (ENO1, HK2, LDHA, LDHB and SLC2A1).

Conclusion

NPM1 is a prognostic biomarker involved in immune infiltration of LUAD and associated with m6A modification and glycolysis. NPM1 can be used as an effective target for diagnosis and treatment of LUAD.

NPM1-mutated acute myeloid leukemia: from bench to bedside

The nucleophosmin (NPM1) gene encodes for a multifunctional protein with prominent nucleolar localization that shuttles between nucleus and cytoplasm. NPM1 mutations represent the most common genetic lesion in adult acute myeloid leukemia (AML; about one third of cases), and they act deterministically to cause the aberrant cytoplasmic delocalization of NPM1 mutants. Because of its unique features, NPM1-mutated AML is recognized as a distinct entity in the 2017 World Health Organization (WHO) classification of hematopoietic neoplasms. Here, we focus on recently identified functions of wild-type NPM1 in the nucleolus and address new biological and clinical issues related to NPM1-mutated AML. The relevance of the cooperation between NPM1 and other mutations in driving AML with different outcomes is presented. We also discuss the importance of eradicating NPM1-mutated clones to achieve AML cure and the impact of preleukemic clonal hematopoiesis persistence in predisposing to second AML. The contribution of HOX genes' expression to the development of NPM1-mutated AML is also highlighted. Clinically, yet unsolved diagnostic issues in the 2017 WHO classification of myeloid neoplasms and the importance of NPM1 mutations in defining the framework of European LeukemiaNet genetic-based risk stratification are discussed. Finally, we address the value and limits of NPM1-based measurable residual disease assessment for treatment guidance and present the results of promising preclinical studies with XPO1 and menin-MLL inhibitors.

Mutual dependency between lncRNA LETN and protein NPM1 in controlling the nucleolar structure and functions sustaining cell proliferation

Fundamental processes such as ribosomal RNA synthesis and chromatin remodeling take place in the nucleolus, which is hyperactive in fast-proliferating cells. The sophisticated regulatory mechanism underlying the dynamic nucleolar structure and functions is yet to be fully explored. The present study uncovers the mutual functional dependency between a previously uncharacterized human long non-coding RNA, which we renamed LETN, and a key nucleolar protein, NPM1. Specifically, being upregulated in multiple types of cancer, LETN resides in the nucleolus via direct binding with NPM1. LETN plays a critical role in facilitating the formation of NPM1 pentamers, which are essential building blocks of the nucleolar granular component and control the nucleolar functions. Repression of LETN or NPM1 led to similar and profound changes of the nucleolar morphology and arrest of the nucleolar functions, which led to proliferation inhibition of human cancer cells and neural progenitor cells. Interestingly, this inter-dependency between LETN and NPM1 is associated with the evolutionarily new variations of NPM1 and the coincidental emergence of LETN in higher primates. We propose that this human-specific protein-lncRNA axis renders an additional yet critical layer of regulation with high physiological relevance in both cancerous and normal developmental processes that require hyperactive nucleoli.

Acceleration or Brakes: Which Is Rational for Cell Cycle-Targeting Neuroblastoma Therapy?

Unrestrained proliferation is a common feature of malignant neoplasms. Targeting the cell cycle is a therapeutic strategy to prevent unlimited cell division. Recently developed rationales for these selective inhibitors can be subdivided into two categories with antithetical functionality. One applies a “brake” to the cell cycle to halt cell proliferation, such as with inhibitors of cell cycle kinases. The other “accelerates” the cell cycle to initiate replication/mitotic catastrophe, such as with inhibitors of cell cycle checkpoint kinases. The fate of cell cycle progression or arrest is tightly regulated by the presence of tolerable or excessive DNA damage, respectively. This suggests that there is compatibility between inhibitors of DNA repair kinases, such as PARP inhibitors, and inhibitors of cell cycle checkpoint kinases. In the present review, we explore alterations to the cell cycle that are concomitant with altered DNA damage repair machinery in unfavorable neuroblastomas, with respect to their unique genomic and molecular features. We highlight the vulnerabilities of these alterations that are attributable to the features of each. Based on the assessment, we offer possible therapeutic approaches for personalized medicine, which are seemingly antithetical, but both are promising strategies for targeting the altered cell cycle in unfavorable neuroblastomas.

The potential role of nucleophosmin (NPM1) in the development of cancer

Nucleophosmin (NPM1) is a well-known nucleocytoplasmic shuttling protein that performs several cellular functions such as ribosome biogenesis, chromatin remodeling, genomic stability, cell cycle progression, and apoptosis. NPM1 has been identified to be necessary for normal cellular functions, and its altered regulation by overexpression, mutation, translocation, loss of function, or sporadic deletion can lead to cancer and tumorigenesis. In this review, we focus on the gene and protein structure of NPM1 and its physiological roles. Finally, we discuss the association of NPM1 with various types of cancer including solid tumors and leukemia.

The deubiquitinase USP36 promotes snoRNP group SUMOylation and is essential for ribosome biogenesis

SUMOylation plays a crucial role in regulating diverse cellular processes including ribosome biogenesis. Proteomic analyses and experimental evidence showed that a number of nucleolar proteins involved in ribosome biogenesis are modified by SUMO. However, how these proteins are SUMOylated in cells is less understood. Here, we report that USP36, a nucleolar deubiquitinating enzyme (DUB), promotes nucleolar SUMOylation. Overexpression of USP36 enhances nucleolar SUMOylation, whereas its knockdown or genetic deletion reduces the levels of SUMOylation. USP36 interacts with SUMO2 and Ubc9 and directly mediates SUMOylation in cells and in vitro. We show that USP36 promotes the SUMOylation of the small nucleolar ribonucleoprotein (snoRNP) components Nop58 and Nhp2 in cells and in vitro and their binding to snoRNAs. It also promotes the SUMOylation of snoRNP components Nop56 and DKC1. Functionally, we show that knockdown of USP36 markedly impairs rRNA processing and translation. Thus, USP36 promotes snoRNP group SUMOylation and is critical for ribosome biogenesis and protein translation.