Nucleophosmin regulates the stability and transcriptional activity of p53

Nucleophosmin 1 overexpression enhances neuroprotection by attenuating cellular stress in traumatic brain injury

BACKGROUND

Traumatic Brain Injury (TBI) is a multifaceted injury that can cause a wide range of symptoms and impairments, leading to significant effects on brain function. Nucleophosmin 1 (NPM1), a versatile phosphoprotein located in the nucleolus, is being recognized as a possible controller of cellular stress reactions and could be important in reducing neuro dysfunction caused by TBI. However the critical roles of NPM1 in cellular stress in TBI remains unclear.

METHODS

We employed a control cortical impact mouse model and a scratch-induced primary neuronal culture model. Hematoxylin and eosin staining was used to evaluate tissue damage and cellular changes, with NPM1 expression in the cortical area assessed through immunofluorescence staining and Western blot analysis. Neuronal morphology was assessed using Nissl staining. Behavioral assessments were performed to evaluate the impact of NPM1 overexpression on neurobehavioral results in TBI mice. Mitochondrial function was assessed using an Extracellular Flux Analyzer.

RESULTS

Following TBI, an increase in NPM1 expression was observed, with a peak at 72 h post-injury. Increased levels of NPM1 resulted in decreased neuronal cell death, as shown by Nissl staining, and lower levels of Caspase 8, APE1, H2AX, and 8-OHDG expression, indicating a reduction in DNA damage. NPM1 overexpression also resulted in improved neurobehavioral outcomes, characterized by decreased neurological deficits and enhanced motor function post-TBI. Additionally, in vitro, scratch-induction experiments revealed that NPM1 overexpression mitigated mitochondrial damage, as evidenced by the downregulation of P53, BCL2, and Cyto C expression levels and improvements in mitochondrial respiratory function.

CONCLUSION

These findings suggest NPM1 as a promising target for developing interventions to alleviate TBI-related cellular stress and promote neuronal survival.

New advances in the role of JAK2 V617F mutation in myeloproliferative neoplasms

The JAK2 V617F mutation is the most common driver gene in myeloproliferative neoplasm (MPN), which means that the JAK/STAT signaling pathway is persistently activated independent of cytokines, and plays an important part in the onset and development of MPN. The JAK inhibitors, although widely used in the clinical practice, are unable to eradicate MPN. Therefore, the unavoidable long-term treatment poses a serious burden for patients with MPN. It is established that the JAK2 V617F mutation, in addition its role in the JAK/STAT pathway, can promote cell proliferation, differentiation, anti-apoptosis, DNA damage accumulation, and other key biologic processes through multiple pathways. Other than that, the JAK2 V617F mutation affects the cardiovascular system through multiple mechanisms. Although JAK inhibitors cannot eradicate MPN cells, the combined use of JAK inhibitors and other drugs may have surprising effects. This requires an in-depth understanding of the mechanism of action of the JAK2 V617F mutation. In this review, the authors explored the role of the JAK2 V617F mutation in MPN from multiple aspects, including the mechanisms of non-JAK/STAT pathways, the regulation of cellular methylation, the induction of cellular DNA damage accumulation, and effects on the cardiovascular system, with the objective of providing valuable insights into multidrug combination therapy for MPN.

Aurora-B: a novel biomarker in the invasion and metastasis of osteosarcoma

Osteosarcoma (OS), a primary human malignant tumor that affects the bones, mostly arises in children and adolescents. Even though surgical resection followed by radiotherapy and chemotherapy has improved the survival rate up to 60%, the long-term positive effect for most patients with OS is not satisfactory. Hence, elucidating the specific mechanisms involved in the pathogenesis of OS is particularly important. Aurora-B, a serine/threonine kinase, plays a crucial role in centrosome regulation, spindle formation and chromosomal separation during mitosis. It has been found that Aurora-B overexpression is related to the occurrence and development of several malignant tumors, including OS. This article summarizes the role of Aurora-B in the invasion and metastasis of OS.

Nucleolar stress caused by arginine-rich peptides triggers a ribosomopathy and accelerates aging in mice

Nucleolar stress (NS) has been associated with age-related diseases such as cancer or neurodegeneration. To investigate how NS triggers toxicity, we used (PR)n arginine-rich peptides present in some neurodegenerative diseases as inducers of this perturbation. We here reveal that whereas (PR)n expression leads to a decrease in translation, this occurs concomitant with an accumulation of free ribosomal (r) proteins. Conversely, (PR)n-resistant cells have lower rates of r-protein synthesis, and targeting ribosome biogenesis by mTOR inhibition or MYC depletion alleviates (PR)n toxicity in vitro. In mice, systemic expression of (PR)97 drives widespread NS and accelerated aging, which is alleviated by rapamycin. Notably, the generalized accumulation of orphan r-proteins is a common outcome of chemical or genetic perturbations that induce NS. Together, our study presents a general model to explain how NS induces cellular toxicity and provides in vivo evidence supporting a role for NS as a driver of aging in mammals.

Elucidation of pericholangitis and periductal fibrosis in cholestatic liver diseases via extracellular vesicles released by polarized biliary epithelial cells

Cholestatic liver diseases causes inflammation and fibrosis around bile ducts. However, the pathological mechanism has not been elucidated. Extracellular vesicles (EVs) are released from both the basolateral and apical sides of polarized biliary epithelial cells. We aimed to investigate the possibility that EVs released from the basolateral sides of biliary epithelial cells by bile acid stimulation induce inflammatory cells and fibrosis around bile ducts, and they may be involved in the pathogenesis of cholestatic liver disease. Human biliary epithelial cells (H69) were grown on cell culture inserts and stimulated with chenodeoxycholic acid + IFN-γ. Human THP-1-derived M1-macrophages, LX-2 cells, and KMST-6 cells were treated with the extracted basolateral EVs, and inflammatory cytokines and fibrosis markers were detected by RT-PCR. Highly expressed proteins from stimulated EVs were identified, and M1-macrophages, LX-2, KMST-6 were treated with these recombinant proteins. Stimulated EVs increased the expression of TNF, IL-1β, and IL-6 in M1-macrophages, TGF-β in LX-2 and KMST-6 compared with the corresponding expression levels in unstimulated EVs. Nucleophosmin, nucleolin, and midkine levels were increased in EVs from stimulated cells compared with protein expression in EVs from unstimulated cells. Leukocyte cell-derived chemotaxin-2 (LECT2) is highly expressed only in EVs from stimulated cells. Stimulation of M1-macrophages with recombinant nucleophosmin, nucleolin, and midkine significantly increased the expression of inflammatory cytokines. Stimulation of LX-2 and KMST-6 with recombinant LECT2 significantly increased the expression of fibrotic markers. These results suggest that basolateral EVs are related to the development of pericholangitis and periductal fibrosis in cholestatic liver diseases.NEW & NOTEWORTHY Our research elucidated that the composition of basolateral EVs from the biliary epithelial cells changed under bile acid exposure and the basolateral EVs contained the novel inflammation-inducing proteins NPM, NCL, and MK and the fibrosis-inducing protein LECT2. We report that these new results are possible to lead to the potential therapeutic target of cholestatic liver diseases in the future.

PARP1 at the crossroad of cellular senescence and nucleolar processes

Senescent cells that occur in response to telomere shortening, oncogenes, extracellular and intracellular stress factors are characterized by permanent cell cycle arrest, the morphological and structural changes of the cell that include the senescence-associated secretory phenotype (SASP) and nucleoli rearrangement. The associated DNA lesions induce DNA damage response (DDR), which activates the DNA repair protein - poly-ADP-ribose polymerase 1 (PARP1). This protein consumes NAD+ to synthesize ADP-ribose polymer (PAR) on its own protein chain and on other interacting proteins. The involvement of PARP1 in nucleoli processes, such as rRNA transcription and ribosome biogenesis, the maintenance of heterochromatin and nucleoli structure, as well as controlling the crucial DDR protein release from the nucleoli to nucleus, links PARP1 with cellular senescence and nucleoli functioning. In this review we describe and discuss the impact of PARP1-mediated ADP-ribosylation on early cell commitment to senescence with the possible role of senescence-induced PARP1 transcriptional repression and protein degradation on nucleoli structure and function. The cause-effect interplay between PARP1 activation/decline and nucleoli functioning during senescence needs to be studied in detail.

SIRT7: the seventh key to unlocking the mystery of aging

Aging is a chronic yet natural physiological decline of the body. Throughout life, humans are continuously exposed to a variety of exogenous and endogenous stresses, which engender various counteractive responses at the cellular, tissue, organ, as well as organismal levels. The compromised cellular and tissue functions that occur because of genetic factors or prolonged stress (or even the stress response) may accelerate aging. Over the last two decades, the sirtuin (SIRT) family of lysine deacylases has emerged as a key regulator of longevity in a variety of organisms. SIRT7, the most recently identified member of the SIRTs, maintains physiological homeostasis and provides protection against aging by functioning as a watchdog of genomic integrity, a dynamic sensor and modulator of stresses. SIRT7 decline disrupts metabolic homeostasis, accelerates aging, and increases the risk of age-related pathologies including cardiovascular and neurodegenerative diseases, pulmonary and renal disorders, inflammatory diseases, and cancer, etc. Here, we present SIRT7 as the seventh key to unlock the mystery of aging, and its specific manipulation holds great potential to ensure healthiness and longevity.

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.

Nucleolar phosphoprotein modifications as a marker of apoptosis induced by RITA treatment

Reactivating p53 and Inducing Tumor Apoptosis (RITA) has been reported to increase the p53 activity and to trigger p53-dependent apoptosis in cancer cells with wild-type p53. Tumor suppressor p53 interacts with nucleolar phosphoproteins nucleophosmin (NPM) and nucleolin (NCL), which have crucial role in many cellular processes. Specific NPM mutations associated with acute myeloid leukemia (AML) cause aberrant localization of NPM and p53 in the cytoplasm with possible impact on the p53 function. We tested an effect of RITA on primary cells, and we found significant RITA-induced changes in NPM and NCL phosphorylation associated with apoptosis in cells of AML patients, but not that of healthy donors. Subsequent screening of several AML cell lines revealed heterogeneous response to RITA, and confirmed an association of the specific phosphorylation with apoptosis. While decreased NCL phosphorylation at Threonines T76 and T84 could be attributed to RITA-induced cell cycle arrest, enhanced NPM phosphorylation at Threonine T199 was not accompanied by the cell cycle changes and it correlated with sensitivity to RITA. Simultaneously, inverse changes occurred at Serine S4 of the NPM. These new findings of RITA mechanism of action could establish the NPM pT199/pS4 ratio as a marker for suitability of RITA treatment of AML cells.

Cytoplasmic localization of Mdm2 in cells expressing mutated NPM is mediated by p53

Specific C-terminal nucleophosmin (NPM) mutations are related to the acute myeloid leukaemia and cause mistargeting of mutated NPM (NPMmut) to the cytoplasm. Consequently, multiple NPM-interacting partners, e.g., the tumour suppressor p53, become also mislocalized. We found that ubiquitin ligase Mdm2 mislocalizes to the cytoplasm in the presence of NPMmut as well. Since p53 interacts with Mdm2, we searched for the NPMmut-p53-Mdm2 complex and interactions of its constituents in live cells and cell lysates using fluorescently tagged proteins, fluorescence lifetime imaging and immunoprecipitation. We proved existence of the ternary complex, which likely adopts a chain-like configuration. Interaction between Mdm2 and NPMmut was not detected, even under conditions of upregulated Mdm2 and p53 induced by Actinomycin D. We assume that p53 serves in the complex as a bridging link between Mdm2 and NPMmut. This conclusion was supported by disruption of the Mdm2-p53 interaction by Nutlin-3A, which resulted in relocalization of Mdm2 to the nucleus, while both NPMmut and p53 remained in the cytoplasm. Importantly, silencing of p53 also prevented mislocalization of Mdm2 in the presence of NPMmut.

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.

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.

Long noncoding RNA LINC01088 inhibits esophageal squamous cell carcinoma progression by targeting the NPM1-HDM2-p53 axis

Esophageal squamous cell carcinoma (ESCC) is characterized by extensive metastasis and poor prognosis. Long noncoding RNAs (lncRNAs) have been shown to play important roles in ESCC. However, the specific roles of lncRNAs in ESCC tumorigenesis and metastasis remain largely unknown. Here, we investigate LINC01088 in ESCC. Differentially expressed LINC01088 levels are screened from the GEO database. We find that LINC01088 is expressed at low level in collected clinical samples and is correlated with vascular tumor emboli and poor overall survival time of patients after surgery. LINC01088 inhibits not only ESCC cell migration and invasion in vitro, but also tumorigenesis and metastasis in vivo. Mechanistically, LINC01088 directly interacts with nucleophosmin (NPM1) and increases the expression of NPM1 in the nucleoplasm compared to that in the nucleolar region. LINC01088 decreases mutant p53 (mut-p53) expression and rescues the transcriptional activity of p53 by targeting the NPM1-HDM2-p53 axis. LINC01088 may also interfere with the DNA repair function of NPM1 by affecting its translocation. Our results highlight the potential of LINC01088 as a prognostic biomarker and therapeutic target of ESCC.

Mutant NPM1 Directly Regulates Oncogenic Transcription in Acute Myeloid Leukemia

The dysregulation of developmental and stem cell-associated genes is a common phenomenon during cancer development. Around half of patients with acute myeloid leukemia (AML) express high levels of HOXA cluster genes and MEIS1. Most of these AML cases harbor an NPM1 mutation (NPM1c), which encodes for an oncoprotein mislocalized from the nucleolus to the cytoplasm. How NPM1c expression in hematopoietic cells leads to its characteristic gene-expression pattern remains unclear. Here, we show that NPM1c directly binds to specific chromatin targets, which are co-occupied by the histone methyltransferase KMT2A (MLL1). Targeted degradation of NPM1c leads to a rapid decrease in gene expression and loss of RNA polymerase II, as well as activating histone modifications at its targets. We demonstrate that NPM1c directly regulates oncogenic gene expression in collaboration with the MLL1 complex and define the mechanism by which MLL1-Menin small-molecule inhibitors produce clinical responses in patients with NPM1-mutated AML.

SIGNIFICANCE

We uncovered an important functional role of mutant NPM1 as a crucial direct driver of oncogenic gene expression in AML. NPM1c can bind to chromatin and cooperate with the MLL complex, providing the first functional insight into the mechanism of Menin-MLL inhibition in NPM1c leukemias. See related article by Wang et al., p. 724. This article is highlighted in the In This Issue feature, p. 517.

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.

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.

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.

Mechanisms of myeloid leukemogenesis: Current perspectives and therapeutic objectives

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic neoplasm which results in clonal proliferation of abnormally differentiated hematopoietic cells. In this review, mechanisms contributing to myeloid leukemogenesis are summarized, highlighting aberrations of epigenetics, transcription factors, signal transduction, cell cycling, and the bone marrow microenvironment. The mechanisms contributing to AML are detailed to spotlight recent findings that convey clinical impact. The applications of current and prospective therapeutic targets are accentuated in addition to reviews of treatment paradigms stratified for each characteristic molecular lesion - with a focus on exploring novel treatment approaches and combinations to improve outcomes in AML.

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.

Insights into Network of Hot Spots of Aggregation in Nucleophosmin 1

In a protein, point mutations associated with diseases can alter the native structure and provide loss or alteration of functional levels, and an internal structural network defines the connectivity among domains, as well as aggregate/soluble states' equilibria. Nucleophosmin (NPM)1 is an abundant nucleolar protein, which becomes mutated in acute myeloid leukemia (AML) patients. NPM1-dependent leukemogenesis, which leads to its aggregation in the cytoplasm (NPMc+), is still obscure, but the investigations have outlined a direct link between AML mutations and amyloid aggregation. Protein aggregation can be due to the cooperation among several hot spots located within the aggregation-prone regions (APR), often predictable with bioinformatic tools. In the present study, we investigated potential APRs in the entire NPM1 not yet investigated. On the basis of bioinformatic predictions and experimental structures, we designed several protein fragments and analyzed them through typical aggrsegation experiments, such as Thioflavin T (ThT), fluorescence and scanning electron microscopy (SEM) experiments, carried out at different times; in addition, their biocompatibility in SHSY5 cells was also evaluated. The presented data clearly demonstrate the existence of hot spots of aggregation located in different regions, mostly in the N-terminal domain (NTD) of the entire NPM1 protein, and provide a more comprehensive view of the molecular details potentially at the basis of NPMc+-dependent AML.

Nucleolus and Nucleolar Stress: From Cell Fate Decision to Disease Development

Besides the canonical function in ribosome biogenesis, there have been significant recent advances towards the fascinating roles of the nucleolus in stress response, cell destiny decision and disease progression. Nucleolar stress, an emerging concept describing aberrant nucleolar structure and function as a result of impaired rRNA synthesis and ribosome biogenesis under stress conditions, has been linked to a variety of signaling transductions, including but not limited to Mdm2-p53, NF-κB and HIF-1α pathways. Studies have uncovered that nucleolus is a stress sensor and signaling hub when cells encounter various stress conditions, such as nutrient deprivation, DNA damage and oxidative and thermal stress. Consequently, nucleolar stress plays a pivotal role in the determination of cell fate, such as apoptosis, senescence, autophagy and differentiation, in response to stress-induced damage. Nucleolar homeostasis has been involved in the pathogenesis of various chronic diseases, particularly tumorigenesis, neurodegenerative diseases and metabolic disorders. Mechanistic insights have revealed the indispensable role of nucleolus-initiated signaling in the progression of these diseases. Accordingly, the intervention of nucleolar stress may pave the path for developing novel therapies against these diseases. In this review, we systemically summarize recent findings linking the nucleolus to stress responses, signaling transduction and cell-fate decision, set the spotlight on the mechanisms by which nucleolar stress drives disease progression, and highlight the merit of the intervening nucleolus in disease treatment.

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.

The role of dual-specificity phosphatase 3 in melanocytic oncogenesis

Dual-specificity phosphatase 3 (DUSP3), also known as Vaccinia H1-related phosphatase, is a protein tyrosine phosphatase that typically performs its major role in the regulation of multiple cellular functions through the dephosphorylation of its diverse and constantly expanding range of substrates. Many of the substrates described so far as well as alterations in the expression or the activity of DUSP3 itself are associated with the development and progression of various types of neoplasms, indicating that DUSP3 may be an important player in oncogenesis and a promising therapeutic target. This review focuses exclusively on DUSP3's contribution to either benign or malignant melanocytic oncogenesis, as many of the established culprit pathways and mechanisms constitute DUSP3's regulatory targets, attempting to synthesize the current knowledge on the matter. The spectrum of the DUSP3 interactions analyzed in this review covers substrates implicated in cellular growth, cell cycle, proliferation, survival, apoptosis, genomic stability/repair, adhesion and migration of tumor melanocytes. Furthermore, the speculations raised, based on the evidence to date, may be considered a fundament for potential research regarding the oncogenesis, evolution, management and therapeutics of melanocytic tumors.

Molecular Classification and Overcoming Therapy Resistance for Acute Myeloid Leukemia with Adverse Genetic Factors

The European LeukemiaNet (ELN) criteria define the adverse genetic factors of acute myeloid leukemia (AML). AML with adverse genetic factors uniformly shows resistance to standard chemotherapy and is associated with poor prognosis. Here, we focus on the biological background and real-world etiology of these adverse genetic factors and then describe a strategy to overcome the clinical disadvantages in terms of targeting pivotal molecular mechanisms. Different adverse genetic factors often rely on common pathways. KMT2A rearrangement, DEK-NUP214 fusion, and NPM1 mutation are associated with the upregulation of HOX genes. The dominant tyrosine kinase activity of the mutant FLT3 or BCR-ABL1 fusion proteins is transduced by the AKT-mTOR, MAPK-ERK, and STAT5 pathways. Concurrent mutations of ASXL1 and RUNX1 are associated with activated AKT. Both TP53 mutation and mis-expressed MECOM are related to impaired apoptosis. Clinical data suggest that adverse genetic factors can be found in at least one in eight AML patients and appear to accumulate in relapsed/refractory cases. TP53 mutation is associated with particularly poor prognosis. Molecular-targeted therapies focusing on specific genomic abnormalities, such as FLT3, KMT2A, and TP53, have been developed and have demonstrated promising results.

Extracellular Nucleophosmin Is Increased in Psoriasis and Correlates With the Determinants of Cardiovascular Diseases

We previously showed that genotoxic stress induced an active extracellular release of nucleophosmin (NPM) in human cardiac mesenchymal progenitor cells, and that serum deprivation provokes NPM secretion from human endothelial cells, eliciting inflammation via nuclear factor kappa B (NF-kB) transcriptional activation. In this study, we wanted to determine whether NPM was similarly modulated in the skin and plasma of psoriatic patients (Pso). We found that NPM was induced in 6 skin biopsies compared to 6 normal skin biopsies and was markedly increased in lesional (LS) vs. non-lesional skin (NLS) biopsies. Moreover, NPM was also increased at the transcriptional levels in LS vs. NLS. Both the innate stimuli, such as lipopolysaccharides and Poly inositol–cytosine and adaptive stimuli, that is, cytokine mix, were able to induce the extracellular release of NPM in immortalized keratinocytes and human skin fibroblasts in the absence of cytotoxicity. Interestingly, NPM interacts with Toll-like receptor (TLR)4 in these cells and activates an NF-kB-dependent inflammatory pathway upregulating interleukin IL-6 and COX-2 gene expression. Finally, circulating NPM was increased in the plasma of 29 Pso compared to 29 healthy controls, and positively correlates with psoriasis area severity index (PASI) and with determinants of cardiovascular diseases (CVDs), such as pulse wave velocity, systolic pressure, and left ventricular mass. Furthermore, NPM positively correlates with miR-200c circulating levels, which we previously showed to increase in Pso and correlate with CVD progression. Our data show that circulating miR-200c is physically associated with extracellular NPM, which most probably is responsible for its extracellular release and protection upon cytokine mix via a TLR4-mechanism. In conclusion, NPM is increased in psoriasis both in the skin and plasma and might be considered a novel biologic target to counteract chronic inflammation associated with CVD risk.

Straight to the Point-The Novel Strategies to Cure Pediatric AML

Although the outcome has improved over the past decades, due to improved supportive care, a better understanding of risk factors, and intensified chemotherapy, pediatric acute myeloid leukemia remains a life-threatening disease, and overall survival (OS) remains near 70%. According to French-American-British (FAB) classification, AML is divided into eight subtypes (M0-M7), and each is characterized by a different pathogenesis and response to treatment. However, the curability of AML is due to the intensification of standard chemotherapy, more precise risk classification, improvements in supportive care, and the use of minimal residual disease to monitor response to therapy. The treatment of childhood AML continues to be based primarily on intensive, conventional chemotherapy. Therefore, it is essential to identify new, more precise molecules that are targeted to the specific abnormalities of each leukemia subtype. Here, we review abnormalities that are potential therapeutic targets for the treatment of AML in the pediatric population.

A role for the NPM1/PTPN14/YAP axis in mediating hypoxia-induced chemoresistance to sorafenib in hepatocellular carcinoma

Background

Tumor microenvironments are characterized by resistance to chemotherapeutic agents and radiotherapy. Hypoxia plays an important role in the development of tumor resistance, as well as the generation of metastatic potential. YAP also participates in the regulation of hypoxia-mediated chemoresistance, and is negatively regulated by protein tyrosine phosphatase non-receptor type 14 (PTPN14).

Methods

The PTPN14 expression in hepatocellular carcinoma (HCC) tissues were evaluated by qRT-PCR, western blot and tissue microarrays. The effect of PTPN14 on HCC progression was investigated in vitro and in vivo.

Results

Here, we report that PTPN14 expression was downregulated in HCC tissues and cell lines. Silencing PTPN14 significantly enhanced proliferation, migration, invasion of HepG2 cells in vitro and tumor growth and metastasis in vivo, whereas overexpression of PTPN14 significantly inhibited these abilities in SK-Hep1 cells. We also found that hypoxia-induced nuclear translocation and accumulation of PTPN14 led to resistance to sorafenib in HCC cells. Further mechanistic studies suggested that NPM1 regulates PTPN14 localization, and that NPM1 regulates YAP by retaining PTPN14 in the nucleus under hypoxic conditions.

Conclusions

These data suggest that a therapeutic strategy against chemoresistant HCC may involve disruption of NPM1-mediated regulation of YAP by retaining PTPN14 in the nucleus under hypoxic conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02479-0.

Mechanisms of nucleophosmin (NPM)-mediated regulated cell death elucidated by Hsp70 during renal ischemia

Nucleophosmin (NPM), a nucleolar-based protein chaperone, promotes Bax-mediated mitochondrial injury and regulates cell death during acute kidney injury. However, the steps that transform NPM from an essential to a toxic protein during stress are unknown. To localize NPM-mediated events causing regulated cell death during ischemia, wild type (WT) and Hsp70 mutant proteins with characterized intracellular trafficking defects that restrict movement to either the nucleolar region (M45) or cytosol (985A) were expressed in primary murine proximal tubule epithelial cells (PTEC) harvested from Hsp70 null mice. After ischemia in vitro, PTEC survival was significantly improved and apoptosis reduced in rank order by selectively overexpressing WT > M45 > 985A Hsp70 proteins. Only Hsp70 with nuclear access (WT and M45) inhibited T95 NPM phosphorylation responsible for NPM translocation and also reduced cytosolic NPM accumulation. In contrast, WT or 985A > M45 significantly improved survival in Hsp70 null PTEC that expressed a cytosol-restricted NPM mutant, more effectively bound NPM, and also reduced NPM-Bax complex formation required for mitochondrial injury and cell death. Hsp70 knockout prevented the cytoprotective effect of suppressing NPM in ischemic PTEC and also increased cytosolic NPM accumulation after acute renal ischemia in vivo, emphasizing the inhibitory effect of Hsp70 on NPM-mediated toxicity. Distinct cytoprotective mechanisms by wild type and mutant Hsp70 proteins identify dual nuclear and cytosolic events that mediate NPM toxicity during stress-induced apoptosis and are rational targets for therapeutic AKI interventions. Antagonizing these early events in regulated cell death promotes renal cell survival during experimental AKI.

Histone chaperone Nucleophosmin regulates transcription of key genes involved in oral tumorigenesis

Nucleophosmin (NPM1) is a multifunctional histone chaperone that can activate acetylation-dependent transcription from chromatin templates in vitro. Acetylation of NPM1 by p300 has been shown to further enhance its transcription activation potential. Moreover, its total and acetylated pools are increased in oral squamous cell carcinoma. However, the role of NPM1 or its acetylated form (AcNPM1) in transcriptional regulation in cells and oral tumorigenesis is not fully elucidated. Using ChIP-seq analyses, we provide the first genome-wide profile of AcNPM1 and show that AcNPM1 is enriched at transcriptional regulatory elements. AcNPM1 co-occupies marks of active transcription at promoters and DNase I hypersensitive sites at enhancers. In addition, using a high-throughput protein interaction profiling approach, we show that NPM1 interacts with RNA Pol II, general transcription factors, mediator subunits, histone acetyltransferase complexes, and chromatin remodelers. NPM1 histone chaperone activity also contributes to its transcription activation potential. Further, NPM1 depletion leads to decreased AcNPM1 occupancy and reduced expression of genes required for proliferative, migratory and invasive potential of oral cancer cells. NPM1 depletion also abrogates the growth of orthotopic tumors in mice. Collectively, these results establish that AcNPM1 functions as a coactivator during during RNA polymerase II-driven transcription and regulates the expression of genes that promote oral tumorigenesis.

Phosphoinositide 3-kinase signalling in the nucleolus

The phosphoinositide 3-kinase (PI3K) signalling pathway plays key roles in many cellular processes and is altered in many diseases. The function and mode of action of the pathway have mostly been elucidated in the cytoplasm. However, many of the components of the PI3K pathway are also present in the nucleus at specific sub-nuclear sites including nuclear speckles, nuclear lipid islets and the nucleolus. Nucleoli are membrane-less subnuclear structures where ribosome biogenesis occurs. Processes leading to ribosome biogenesis are tightly regulated to maintain protein translation capacity of cells. This review focuses on nucleolar PI3K signalling and how it regulates rRNA synthesis, as well as on the identification of downstream phosphatidylinositol (3,4,5)trisphosphate effector proteins.

CYCLON and NPM1 Cooperate within an Oncogenic Network Predictive of R-CHOP Response in DLBCL

Simple Summary

CYCLON is a nuclear protein, which has been associated with disease progression and treatment resistance in DLBCL, the most common form of aggressive B-cell lymphoma, but also represents a predictive factor of refractory disease and relapse for immuno-chemotherapy-treated DLBCL patients. The molecular mechanisms related to this unstructured protein remain largely uncharacterized. Here, we performed a mass-spectrometry-based identification of the CYCLON protein interactome that suggested it could exert nucleolar functions related to cell proliferation. Among the CYCLON oncogenic network, we performed an immunohistochemical evaluation of the multi-functional nucleolar protein NPM1 in a DLBCL cohort and showed that CYCLON/NPM1 concomitant expression delineates a poor prognosis subgroup of patients. Multivariate survival analyses demonstrated that specific sub-cellular localizations of CYCLON and NPM1 represent independent novel predictors specifically associated with refractory DLBCL.

Abstract

R-CHOP immuno-chemotherapy significantly improved clinical management of diffuse large B-cell lymphoma (DLBCL). However, 30–40% of DLBCL patients still present a refractory disease or relapse. Most of the prognostic markers identified to date fail to accurately stratify high-risk DLBCL patients. We have previously shown that the nuclear protein CYCLON is associated with DLBCL disease progression and resistance to anti-CD20 immunotherapy in preclinical models. We also recently reported that it also represents a potent predictor of refractory disease and relapse in a retrospective DLBCL cohort. However, only sparse data are available to predict the potential biological role of CYCLON and how it might exert its adverse effects on lymphoma cells. Here, we characterized the protein interaction network of CYCLON, connecting this protein to the nucleolus, RNA processing, MYC signaling and cell cycle progression. Among this network, NPM1, a nucleolar multi-functional protein frequently deregulated in cancer, emerged as another potential target related to treatment resistance in DLBCL. Immunohistochemistry evaluation of CYCLON and NPM1 revealed that their co-expression is strongly related to inferior prognosis in DLBCL. More specifically, alternative sub-cellular localizations of the proteins (extra-nucleolar CYCLON and pan-cellular NPM1) represent independent predictive factors specifically associated to R-CHOP refractory DLBCL patients, which could allow them to be orientated towards risk-adapted or novel targeted therapies.

Biomarkers in Acute Myeloid Leukemia: Leveraging Next Generation Sequencing Data for Optimal Therapeutic Strategies

Next generation sequencing (NGS) is routinely used for mutation profiling of acute myeloid leukemia. The extensive application of NGS in hematologic malignancies, and its significant association with the outcomes in multiple large cohorts constituted a proof of concept that AML phenotype is driven by underlying mutational signature and is amenable for targeted therapies. These findings urged incorporation of molecular results into the latest World Health Organization (WHO) sub-classification and integration into risk-stratification and treatment guidelines by the European Leukemia Net. NGS mutation profiling provides a large amount of information that guides diagnosis and management, dependent on the type and number of gene mutations, variant allele frequency and amenability to targeted therapeutics. Hence, molecular mutational profiling is an integral component for work-up of AML and multiple leukemic entities. In addition, there is a vast amount of informative data that can be obtained from routine clinical NGS sequencing beyond diagnosis, prognostication and therapeutic targeting. These include identification of evidence regarding the ontogeny of the disease, underlying germline predisposition and clonal hematopoiesis, serial monitoring to assess the effectiveness of therapy and resistance mutations, which have broader implications for management. In this review, using a few prototypic genes in AML, we will summarize the clinical applications of NGS generated data for optimal AML management, with emphasis on the recently described entities and Food and Drug Administration approved target therapies.

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.

HO-1 nuclear accumulation and interaction with NPM1 protect against stress-induced endothelial senescence independent of its enzymatic activity

Heme oxygenase-1 (HO-1) has attracted accumulating attention for its antioxidant enzymatic activity. However, the exact regulatory role of its non-enzymatic activity in the cardiovascular system remains unaddressed. Here, we show that HO-1 was accumulated in the nuclei of stress-induced senescent endothelial cells, and conferred protection against endothelial senescence independent of its enzymatic activity. Overexpression of ΔHO-1, a truncated HO-1 without transmembrane segment (TMS), inhibited H2O2-induced endothelial senescence. Overexpression of ΔHO-1H25A, the catalytically inactive form of ΔHO-1, also exhibited anti-senescent effect. In addition, infection of recombinant adenovirus encoding ΔHO-1 with three nuclear localization sequences (NLS), alleviated endothelial senescence induced by knockdown of endogenous HO-1 by CRISPR/Cas9. Moreover, repression of HO-1 nuclear translocation by silencing of signal peptide peptidase (SPP), which is responsible for enzymatic cleavage of the TMS of HO-1, exacerbated endothelial senescence. Mechanistically, nuclear HO-1 interacted with NPM1 N-terminal portion, prevented NPM1 translocation from nucleolus to nucleoplasm, thus disrupted NPM1/p53/MDM2 interactions and inhibited p53 activation by NPM1, finally resisted endothelial senescence. This study provides a novel understanding of HO-1 as a promising therapeutic strategy for vascular senescence-related cardiovascular diseases.

MEScan: a powerful statistical framework for genome-scale mutual exclusivity analysis of cancer mutations

MOTIVATION

Cancer somatic driver mutations associated with genes within a pathway often show a mutually exclusive pattern across a cohort of patients. This mutually exclusive mutational signal has been frequently used to distinguish driver from passenger mutations and to investigate relationships among driver mutations. Current methods for de novo discovery of mutually exclusive mutational patterns are limited because the heterogeneity in background mutation rate can confound mutational patterns, and the presence of highly mutated genes can lead to spurious patterns. In addition, most methods only focus on a limited number of pre-selected genes and are unable to perform genome-wide analysis due to computational inefficiency.

RESULTS

We introduce a statistical framework, MEScan, for accurate and efficient mutual exclusivity analysis at the genomic scale. Our framework contains a fast and powerful statistical test for mutual exclusivity with adjustment of the background mutation rate and impact of highly mutated genes, and a multi-step procedure for genome-wide screening with the control of false discovery rate. We demonstrate that MEScan more accurately identifies mutually exclusive gene sets than existing methods and is at least two orders of magnitude faster than most methods. By applying MEScan to data from four different cancer types and pan-cancer, we have identified several biologically meaningful mutually exclusive gene sets.

AVAILABILITY AND IMPLEMENTATION

MEScan is available as an R package at https://github.com/MarkeyBBSRF/MEScan.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

AML-Related NPM Mutations Drive p53 Delocalization into the Cytoplasm with Possible Impact on p53-Dependent Stress Response

Simple Summary

Nucleophosmin (NPM) is one of the most abundant nucleolar proteins and its mutations frequently occur in acute myeloid leukemia (AML). The mutations cause aberrant cytoplasmic localization of mutated protein (NPMmut) and often mediate dislocation of NPM interaction partners. Tumor suppressor p53 is known to interact with NPM in response to genotoxic stress and its cytoplasmic localization is an unfavorable prognostic factor in cancers. This study aims to characterize the NPM-p53 interaction and to elucidate the effect of the NPM mutations on p53 localization and expression in live cells. In addition, the cellular dynamics of NPMmut and p53 after treatment with nuclear export inhibitor Selinexor is described and the mechanism of the Selinexor action proposed. Our results contribute to a better understanding of the oncogenic potential of NPM mutations.

Abstract

Nucleophosmin (NPM) interaction with tumor suppressor p53 is a part of a complex interaction network and considerably affects cellular stress response. The impact of NPM1 mutations on its interaction with p53 has not been investigated yet, although consequences of NPMmut-induced p53 export to the cytoplasm are important for understanding the oncogenic potential of these mutations. We investigated p53-NPM interaction in live HEK-293T cells by FLIM-FRET and in cell lysates by immunoprecipitation. eGFP lifetime-photoconversion was used to follow redistribution dynamics of NPMmut and p53 in Selinexor-treated cells. We confirmed the p53-NPMwt interaction in intact cells and newly documented that this interaction is not compromised by the NPM mutation causing displacement of p53 to the cytoplasm. Moreover, the interaction was not abolished for non-oligomerizing NPM variants with truncated oligomerization domain, suggesting that oligomerization is not essential for interaction of NPM forms with p53. Inhibition of the nuclear exporter XPO1 by Selinexor caused expected nuclear relocalization of both NPMmut and p53. However, significantly different return rates of these proteins indicate nontrivial mechanism of p53 and NPMmut cellular trafficking. The altered p53 regulation in cells expressing NPMmut offers improved understanding to help investigational strategies targeting these mutations.

Doxorubicin induces an alarmin-like TLR4-dependent autocrine/paracrine action of Nucleophosmin in human cardiac mesenchymal progenitor cells

Background

Doxorubicin (Dox) is an anti-cancer anthracycline drug that causes double-stranded DNA breaks. It is highly effective against several types of tumours; however, it also has adverse effects on regenerative populations of normal cells, such as human cardiac mesenchymal progenitor cells (hCmPCs), and its clinical use is limited by cardiotoxicity. Another known effect of Dox is nucleolar disruption, which triggers the ubiquitously expressed nucleolar phosphoprotein Nucleophosmin (NPM) to be released from the nucleolus into the cell, where it participates in the orchestration of cellular stress responses. NPM has also been observed in the extracellular space in response to different stress stimuli; however, the mechanism behind this and its functional implications are as yet largely unexplored. The aim of this study was to establish whether Dox could elicit NPM secretion in the extracellular space and to elucidate the mechanism of secretion and the effect of extracellular NPM on hCmPCs.

Results

We found that following the double-strand break formation in hCmPCs caused by Dox, NPM was rapidly secreted in the extracellular space by an active mechanism, in the absence of either apoptosis or necrosis. Extracellular release of NPM was similarly seen in response to ultraviolet radiation (UV). Furthermore, we observed an increase of NPM levels in the plasma of Dox-treated mice; thus, NPM release also occurred in vivo. The treatment of hCmPCs with extracellular recombinant NPM induced a decrease of cell proliferation and a response mediated through the Toll-like receptor (TLR)4. We demonstrated that NPM binds to TLR4, and via TLR4, and nuclear factor kappa B (NFkB) activation/nuclear translocation, exerts proinflammatory functions by inducing IL-6 and COX-2 gene expression. Finally, we found that in hCmPCs, NPM secretion could be driven by an autophagy-dependent unconventional mechanism that requires TLR4, since TLR4 inhibition dramatically reduced Dox-induced secretion.

Conclusions

We hypothesise that the extracellular release of NPM could be a general response to DNA damage since it can be elicited by either a chemical agent such as Dox or a physical genotoxic stressor such as UV radiation. Following genotoxic stress, NPM acts similarly to an alarmin in hCmPCs, being rapidly secreted and promoting cell cycle arrest and a TLR4/NFκB-dependent inflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01058-5.

SIRT7-dependent deacetylation of NPM promotes p53 stabilization following UV-induced genotoxic stress

Adaptation to different forms of environmental stress is crucial for maintaining essential cellular functions and survival. The nucleolus plays a decisive role as a signaling hub for coordinating cellular responses to various extrinsic and intrinsic cues. p53 levels are normally kept low in unstressed cells, mainly due to E3 ubiquitin ligase MDM2-mediated degradation. Under stress, nucleophosmin (NPM) relocates from the nucleolus to the nucleoplasm and binds MDM2, thereby preventing degradation of p53 and allowing cell-cycle arrest and DNA repair. Here, we demonstrate that the mammalian sirtuin SIRT7 is an essential component for the regulation of p53 stability during stress responses induced by ultraviolet (UV) irradiation. The catalytic activity of SIRT7 is substantially increased upon UV irradiation through ataxia telangiectasia mutated and Rad3 related (ATR)-mediated phosphorylation, which promotes efficient deacetylation of the SIRT7 target NPM. Deacetylation is required for stress-dependent relocation of NPM into the nucleoplasm and MDM2 binding, thereby preventing ubiquitination and degradation of p53. In the absence of SIRT7, stress-dependent stabilization of p53 is abrogated, both in vitro and in vivo, impairing cellular stress responses. The study uncovers an essential SIRT7-dependent mechanism for stabilization of the tumor suppressor p53 in response to genotoxic stress.

Doxorubicin/Nucleophosmin Binding Protein-Conjugated Nanoparticle Enhances Anti-leukemia Activity in Acute Lymphoblastic Leukemia Cells in vitro and in vivo

Acute lymphoblastic leukemia (ALL) is an aggressive malignancy. Adults with ALL have more than 50% relapse rates. We have previously validated that overexpression of nucleophosmin (NPM) is involved in the multidrug resistance (MDR) development during ALL; and a synthetically engineered recombinant NPM binding protein (NPMBP) has been developed in our group; NPMBP and doxorubicin (DOX) can be conjugated in a nanoparticle-based drug delivery system named DOX-PMs-NPMBP to counteract MDR during ALL. Here, we evaluated the antileukemia potential of DOX-PMs-NPMBP in resistant ALL cells. This study demonstrates that DOX-PMs-NPMBP significantly enhances chemosensitivity to DOX in ALL cells. Despite at variable concentrations, both resistant and primary ALL cells from relapsed patients were sensitive to DOX-PMs-NPMBP. In detail, the half maximal inhibitory concentration (IC50) values of DOX-PMs-NPMBP were between 1.6- and 7.0-fold lower than those of DOX in cell lines and primary ALL cells, respectively; and apoptotic cells ratio was over 2-fold higher in DOX-PMs-NPMBP than DOX. Mechanistically, p53-driven apoptosis induction and cell cycle arrest played essential role in DOX-PMs-NPMBP-induced anti-leukemia effects. Moreover, DOX-PMs-NPMBP significantly inhibited tumor growth and prolonged mouse survival of ALL xenograft models; and no systemic toxicity occurrence was observed after treatment during follow-up. In conclusion, these data indicate that DOX-PMs-NPMBP may significantly exert growth inhibition and apoptosis induction, and markedly improve DOX antileukemia activity in resistant ALL cells. This novel drug delivery system may be valuable to develop as a new therapeutic strategy against multidrug resistant ALL.

Outcomes of older patients with NPM1-mutated AML: current treatments and the promise of venetoclax-based regimens

Nucleophosmin-1 mutations (NPM1+) occur in ∼30% of acute myeloid leukemia (AML) patients. Although typically associated with favorable prognosis, the beneficial impact of NPM1+ decreases with increasing age in patients treated with standard intensive chemotherapy (IC) or hypomethylating agents (HMAs). This retrospective analysis compared outcomes of NPM1+ AML patients treated with 1 of 3 induction approaches: HMA plus BCL-2 inhibitor venetoclax (VEN), HMA, or IC therapy. Composite complete response (CRc: CR + CR with incomplete count recovery) was seen in 96% (27/28), 36% (17/47), and 89% (204/228) of HMA + VEN, HMA, and IC patients, respectively (HMA + VEN vs HMA, P < .001; HMA + VEN vs IC, P = .10). Older patients (age >65 years) treated with HMA + VEN, HMA, or IC had CR rates of 88%, 28%, and 56%, respectively (HMA + VEN vs HMA, P < .001; HMA + VEN vs IC, P = .01). Significant improvement in overall survival (OS) was seen in patients age >65 years treated with HMA + VEN vs HMA (not reached [NR] vs 0.4 years; P < .001) or IC (NR vs 0.93 years; P = .001). Older patients treated with HMA + VEN had OS of 80% after median 1-year follow-up, with estimated 2-year OS of 70%. In the multivariable Cox model analysis, HMA + VEN was associated with a 69% lower risk of death compared with IC (hazard ratio, 0.31; 95% confidence interval, 0.12-0.83; type I error-adjusted P = .038). HMA + VEN combinations demonstrated impressive results compared with traditional standard-of-care regimens in older patients with NPM1+ AML.

Probing nucleus-enriched proteins in single living cells via a subcellular-resolved plasmonic immunosandwich assay

Nuclear proteins are crucial in cells and are greatly linked to various biological functions. Abnormal expression of nuclear proteins is associated with many diseases ranging from inflammation to cancer. However, it remains challenging to detect nuclear proteins in single cells because of their low abundance and complex subcellular environment. Herein, we report a subcellular-resolved plasmonic immunosandwich assay (srPISA), for probing nucleus-enriched proteins in single living cells with minimal disruption. We demonstrated the specific extraction and ultrasensitive detection capabilities of the srPISA by probing low-copy-number nuclear telomerase in single living cells and further compared the telomerase expression levels in these single cells. Additionally, we showed the subcellular resolving capability of the srPISA by probing the spatial distribution of smad2 in the nucleus and cytoplasm of single living cells. We found that smad2 was expressed both in the nucleus and the cytoplasm, but showed different expression levels. Moreover, smad2 distributed more homogeneously in the nucleus than in the cytoplasm. Finally, the srPISA of nuclear telomerase in cell division strongly verified that the subcellular analytical results obtained by the srPISA are reliable. Overall, the srPISA approach allowed specific extraction and ultrasensitive detection of target low-copy-number proteins at the subcellular level, providing a unique and powerful single cell analysis tool for cell biology studies.

Mutant p53 Drives Cancer Metastasis via RCP-Mediated Hsp90α Secretion

Mutant p53 (mutp53) loses its tumor suppressor properties but gains oncogenic functions of driving malignancy. However, it remains largely unknown how mutp53 drives cancer metastasis. Here, we show that wild-type p53 (WTp53) suppresses the secretion of heat shock protein 90-alpha (Hsp90α), whereas mutp53 enhances Hsp90α vesicular trafficking and exosome-mediated secretion. Long-term delivery of an antibody that blocks extracellular Hsp90α (eHsp90α) function extends the survival of p53^-/- mice and attenuates the invasiveness of p53 mutant tumors. Furthermore, mass spectrometry and functional analysis identified a critical role for Rab coupling protein (RCP) in mutp53-induced Hsp90α secretion. RCP knockdown decreases eHsp90α levels and inhibits malignant progression. Notably, recombinant Hsp90α re-introduction markedly rescues the impaired migration and invasion abilities caused by RCP depletion. Taken together, these findings elucidate the molecular mechanisms by which mutp53 executes oncogenic activities via its downstream RCP-mediated Hsp90α secretion and a strategy to treat human cancers expressing mutp53 proteins.

Enzymatically active apurinic/apyrimidinic endodeoxyribonuclease 1 is released by mammalian cells through exosomes

The apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1), the main AP-endonuclease of the DNA base excision repair pathway, is a key molecule of interest to researchers due to its unsuspected roles in different nonrepair activities, such as: i) adaptive cell response to genotoxic stress, ii) regulation of gene expression, and iii) processing of microRNAs, which make it an excellent drug target for cancer treatment. We and others recently demonstrated that APE1 can be secreted in the extracellular environment and that serum APE1 may represent a novel prognostic biomarker in hepatocellular and non-small-cell lung cancers. However, the mechanism by which APE1 is released extracellularly was not described before. Here, using three different approaches for exosomes isolation: commercial kit, nickel-based isolation, and ultracentrifugation methods and various mammalian cell lines, we elucidated the mechanisms responsible for APE1 secretion. We demonstrated that APE1 p37 and p33 forms are actively secreted through extracellular vesicles (EVs), including exosomes from different mammalian cell lines. We then observed that APE1 p33 form is generated by proteasomal-mediated degradation and is enzymatically active in EVs. Finally, we revealed that the p33 form of APE1 accumulates in EVs upon genotoxic treatment by cisplatin and doxorubicin, compounds commonly found in chemotherapy pharmacological treatments. Taken together, these findings provide for the first time evidence that a functional Base Excision Repair protein is delivered through exosomes in response to genotoxic stresses, shedding new light into the complex noncanonical biological functions of APE1 and opening new intriguing perspectives on its role in cancer biology.

Short loop functional commonality identified in leukaemia proteome highlights crucial protein sub-networks

Direct drug targeting of mutated proteins in cancer is not always possible and efficacy can be nullified by compensating protein-protein interactions (PPIs). Here, we establish an in silico pipeline to identify specific PPI sub-networks containing mutated proteins as potential targets, which we apply to mutation data of four different leukaemias. Our method is based on extracting cyclic interactions of a small number of proteins topologically and functionally linked in the Protein-Protein Interaction Network (PPIN), which we call short loop network motifs (SLM). We uncover a new property of PPINs named 'short loop commonality' to measure indirect PPIs occurring via common SLM interactions. This detects 'modules' of PPI networks enriched with annotated biological functions of proteins containing mutation hotspots, exemplified by FLT3 and other receptor tyrosine kinase proteins. We further identify functional dependency or mutual exclusivity of short loop commonality pairs in large-scale cellular CRISPR-Cas9 knockout screening data. Our pipeline provides a new strategy for identifying new therapeutic targets for drug discovery.

NSC348884 cytotoxicity is not mediated by inhibition of nucleophosmin oligomerization

Nucleophosmin (NPM) mutations causing its export from the nucleoli to the cytoplasm are frequent in acute myeloid leukemia (AML). Due to heterooligomerization of wild type NPM with the AML-related mutant, the wild-type becomes misplaced from the nucleoli and its functions are significantly altered. Dissociation of NPM heterooligomers may thus restore the proper localization and function of wild-type NPM. NSC348884 is supposed to act as a potent inhibitor of NPM oligomerization. The effect of NSC348884 on the NPM oligomerization was thoroughly examined by fluorescence lifetime imaging with utilization of FRET and by a set of immunoprecipitation and electrophoretic methods. Leukemia-derived cell lines and primary AML cells as well as cells transfected with fluorescently labeled NPM forms were investigated. Our results clearly demonstrate that NSC348884 does not inhibit formation of NPM oligomers neither in vivo nor in vitro. Instead, we document that NSC348884 cytotoxicity is rather associated with modified cell adhesion signaling. The cytotoxic mechanism of NSC348884 has therefore to be reconsidered.

Sirtuins and Their Implications in Neurodegenerative Diseases from a Drug Discovery Perspective

Sirtuins are class III histone deacetylase (HDAC) enzymes that target both histone and non-histone substrates. They are linked to different brain functions and the regulation of different isoforms of these enzymes is touted to be an emerging therapy for the treatment of neurodegenerative diseases (NDs), including Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS). The level of sirtuins affects brain health as many sirtuin-regulated pathways are responsible for the progression of NDs. Certain sirtuins are also implicated in aging, which is a risk factor for many NDs. In addition to SIRT1-3, it has been suggested that the less studied sirtuins (SIRT4-7) also play critical roles in brain health. This review delineates the role of each sirtuin isoform in NDs from a disease centric perspective and provides an up-to-date overview of sirtuin modulators and their potential use as therapeutics in these diseases. Furthermore, the future perspectives for sirtuin modulator development and their therapeutic application in neurodegeneration are outlined in detail, hence providing a research direction for future studies.

The Wnt/β-Catenin Pathway is Activated as a Novel Nucleolar Stress Response

Ribosomes are mandatory for growth and survival. The complex process of ribosome biogenesis is located in nucleoli and requires action of the RNA polymerases I-III, together with a multitude of processing factors involved in rRNA cleavage and maturation. Impaired ribosome biogenesis and loss of nucleolar integrity triggers nucleolar stress, which classically stabilizes the tumor suppressor p53 and induces cell cycle arrest and apoptosis. Nucleolar stress is implemented in modern anti-cancer therapies, however, also emerges as contributor to diverse pathological conditions. These include ribosomopathies, such as the Shwachman Bodian Diamond Syndrome (SBDS), which are not only characterized by nucleolar stress, but paradoxically also increased cancer incidence. Wnt signaling is tightly coupled to cell proliferation and is constitutively activated in various tumor types. In addition, the Wnt/β-Catenin pathway regulates ribosome formation. Here, we demonstrate that induction of nucleolar stress by different strategies stimulates the Wnt/β-Catenin pathway. We show that depletion of the key ribosomopathy factor SBDS, or the nucleolar factors Nucleophosmin (NPM), Pescadillo 1 (PES1) or Peter Pan (PPAN) by si RNA-mediated knockdown or CRISPR/Cas9 strategy activates Wnt/β-Catenin signaling in a β-Catenin-dependent manner and stabilizes β-Catenin in human cancer cells. Moreover, triggering nucleolar stress by the chemotherapeutic agents Actinomycin D or the RNA polymerase I inhibitor CX-5461 stimulates expression of Wnt/β-Catenin targets, which is followed by the p53 target CDKN1A (p21). As PPAN expression is induced by Wnt/β-Catenin signaling, our data establish a novel feedback mechanism and reveal that nucleolar stress over-activates the Wnt/β-Catenin pathway, which most likely serves as compensatory mechanism to sustain ribosome biogenesis.

Ribosome biogenesis is a downstream effector of the oncogenic U2AF1-S34F mutation

U2 Small Nuclear RNA Auxiliary Factor 1 (U2AF1) forms a heterodimeric complex with U2AF2 that is primarily responsible for 3' splice site selection. U2AF1 mutations have been identified in most cancers but are prevalent in Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML), and the most common mutation is a missense substitution of serine-34 to phenylalanine (S34F). The U2AF heterodimer also has a noncanonical function as a translational regulator. Here, we report that the U2AF1-S34F mutation results in specific misregulation of the translation initiation and ribosome biogenesis machinery. The net result is an increase in mRNA translation at the single-cell level. Among the translationally up-regulated targets of U2AF1-S34F is Nucleophosmin 1 (NPM1), which is a major driver of myeloid malignancy. Depletion of NPM1 impairs the viability of the U2AF1-S34F mutant cells and causes ribosomal RNA (rRNA) processing defects, thus indicating an unanticipated synthetic interaction between U2AF1, NPM1, and ribosome biogenesis. Our results establish a unique molecular phenotype for the U2AF1 mutation that recapitulates translational misregulation in myeloid disease.

B-cell clonogenic activity of HIV-1 p17 variants is driven by PAR1-mediated EGF transactivation

Combined antiretroviral therapy (cART) for HIV-1 dramatically slows disease progression among HIV⁺ individuals. Currently, lymphoma represents the main cause of death among HIV-1-infected patients. Detection of p17 variants (vp17s) endowed with B-cell clonogenic activity in HIV-1-seropositive patients with lymphoma suggests their possible role in lymphomagenesis. Here, we demonstrate that the clonogenic activity of vp17s is mediated by their binding to PAR1 and to PAR1-mediated EGFR transactivation through Gq protein. The entire vp17s-triggered clonogenic process is MMPs dependent. Moreover, phosphoproteomic and bioinformatic analysis highlighted the crucial role of EGFR/PI3K/Akt pathway in modulating several molecules promoting cancer progression, including RAC1, ABL1, p53, CDK1, NPM, Rb, PTP-1B, and STAT1. Finally, we show that a peptide (F1) corresponding to the vp17s functional epitope is sufficient to trigger the PAR1/EGFR/PI3K/Akt pathway and bind PAR1. Our findings suggest novel potential therapeutic targets to counteract vp17-driven lymphomagenesis in HIV⁺ patients.