The human nucleophosmin 1 mutation A inhibits myeloid differentiation of leukemia cells by modulating miR-10b

Utilizing exosomes as sparking clinical biomarkers and therapeutic response in acute myeloid leukemia

Acute myeloid leukemia (AML) is a malignant clonal tumor originating from immature myeloid hematopoietic cells in the bone marrow with rapid progression and poor prognosis. Therefore, an in-depth exploration of the pathogenesis of AML can provide new ideas for the treatment of AML. In recent years, it has been found that exosomes play an important role in the pathogenesis of AML. Exosomes are membrane-bound extracellular vesicles (EVs) that transfer signaling molecules and have attracted a large amount of attention, which are key mediators of intercellular communication. Extracellular vesicles not only affect AML cells and normal hematopoietic cells but also have an impact on the bone marrow microenvironment and immune escape, thereby promoting the progression of AML and leading to refractory relapse. It is worth noting that exosomes and the various molecules they contain are expected to become the new markers for disease monitoring and prognosis of AML, and may also function as drug carriers and vaccines to enhance the treatment of leukemia. In this review, we mainly summarize to reveal the role of exosomes in AML pathogenesis, which helps us elucidate the application of exosomes in AML diagnosis and treatment.

Human VDAC pseudogenes: an emerging role for VDAC1P8 pseudogene in acute myeloid leukemia

BACKGROUND

Voltage-dependent anion selective channels (VDACs) are the most abundant mitochondrial outer membrane proteins, encoded in mammals by three genes, VDAC1, 2 and 3, mostly ubiquitously expressed. As 'mitochondrial gatekeepers', VDACs control organelle and cell metabolism and are involved in many diseases. Despite the presence of numerous VDAC pseudogenes in the human genome, their significance and possible role in VDAC protein expression has not yet been considered.

RESULTS

We investigated the relevance of processed pseudogenes of human VDAC genes, both in physiological and in pathological contexts. Using high-throughput tools and querying many genomic and transcriptomic databases, we show that some VDAC pseudogenes are transcribed in specific tissues and pathological contexts. The obtained experimental data confirm an association of the VDAC1P8 pseudogene with acute myeloid leukemia (AML).

CONCLUSIONS

Our in-silico comparative analysis between the VDAC1 gene and its VDAC1P8 pseudogene, together with experimental data produced in AML cellular models, indicate a specific over-expression of the VDAC1P8 pseudogene in AML, correlated with a downregulation of the parental VDAC1 gene.

Type F mutation of nucleophosmin 1 Acute Myeloid Leukemia: A tale of disorder and aggregation

Protein aggregation is suggested as a reversible, wide-spread physiological process used by cells to regulate their growth and adapt to different stress conditions. Nucleophosmin 1(NPM1) protein is an abundant multifunctional nucleolar chaperone and its gene is the most frequently mutated in Acute Myeloid Leukemia (AML) patients. So far, the role of NPM1 mutations in leukemogenesis has remained largely elusive considering that they have the double effect of unfolding the C-terminal domain (CTD) and delocalizing the protein in the cytosol (NPM1c+). This mislocalization heavily impacts on cell cycle regulation. Our recent investigations unequivocally demonstrated an amyloid aggregation propensity introduced by AML mutations. Herein, employing complementary biophysical assays, we have characterized a N-terminal extended version of type F AML mutation of CTD and proved that it is able to form assemblies with amyloid character and fibrillar morphology. The present study represents an additional phase of knowledge to deepen the roles exerted by different types of cytoplasmatic NPM1c+ forms to develop in the future potential therapeutics for their selective targeting.

Nucleophosmin, a multifunctional nucleolar organizer with a role in DNA repair

Nucleophosmin (NPM1) is a mostly nucleolar protein with crucial functions in cell growth and homeostasis, including regulation of ribosome biogenesis and stress response. Such multiple activities rely on its ability to interact with nucleic acids and with hundreds of proteins, as well as on a dynamic subcellular distribution. NPM1 is thus regulated by a complex interplay between localization and interactions, further modulated by post-translational modifications. NPM1 is a homopentamer, with globular domains connected by long, intrinsically disordered linkers. This configuration allows NPM1 to engage in liquid-liquid phase separation phenomena, which could underlie a key role in nucleolar organization. Here, we will discuss NPM1 conformational and functional versatility, emphasizing its emerging, and still largely unexplored, role in DNA damage repair. Since NPM1 is altered in a subtype of acute myeloid leukaemia (AML), we will also present ongoing research on the molecular mechanisms underlying its pathogenic role and potential NPM1-targeting therapeutic strategies.

Architecture of The Human Ape1 Interactome Defines Novel Cancers Signatures

APE1 is essential in cancer cells due to its central role in the Base Excision Repair pathway of DNA lesions and in the transcriptional regulation of genes involved in tumor progression/chemoresistance. Indeed, APE1 overexpression correlates with chemoresistance in more aggressive cancers, and APE1 protein-protein interactions (PPIs) specifically modulate different protein functions in cancer cells. Although important, a detailed investigation on the nature and function of protein interactors regulating APE1 role in tumor progression and chemoresistance is still lacking. The present work was aimed at analyzing the APE1-PPI network with the goal of defining bad prognosis signatures through systematic bioinformatics analysis. By using a well-characterized HeLa cell model stably expressing a flagged APE1 form, which was subjected to extensive proteomics analyses for immunocaptured complexes from different subcellular compartments, we here demonstrate that APE1 is a central hub connecting different subnetworks largely composed of proteins belonging to cancer-associated communities and/or involved in RNA- and DNA-metabolism. When we performed survival analysis in real cancer datasets, we observed that more than 80% of these APE1-PPI network elements is associated with bad prognosis. Our findings, which are hypothesis generating, strongly support the possibility to infer APE1-interactomic signatures associated with bad prognosis of different cancers; they will be of general interest for the future definition of novel predictive disease biomarkers. Future studies will be needed to assess the function of APE1 in the protein complexes we discovered. Data are available via ProteomeXchange with identifier PXD013368.

High serum extracellular vesicle miR-10b expression predicts poor prognosis in patients with acute myeloid leukemia

BACKGROUND

Increasing evidence have demonstrated that serum extracellular vesicle microRNAs (EV-miRNAs) are promising noninvasive biomarkers for various cancer types.

OBJECTIVE

In this study, we aimed to investigate and evaluate the potential clinical significance of serum EV-miR-10b for acute myeloid leukemia (AML).

METHODS

Blood samples were collected from a cohort of 95 de novo AML patients and 80 healthy individuals. Of all AML patients, 51 patients were considered as cytogenetic normal AML (CN-AML). Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was performed to measure the expression levels of serum EV-miR-10b.

RESULTS

The extracellular vesicles we extracted from the serum samples were positive for EV/exosome markers including TSG101, CD63, Flotillin-1 and CD9. The expression levels of serum EV-miR-10b were significantly higher in AML/CN-AML patients than healthy controls. In addition, serum EV-miR-10b expression was strongly correlated with aggressive clinical characteristics. Moreover, receiver operating characteristic analysis showed serum EV-miR-10b yielded an area under the curve of 0.875, with 77.89% specificity and 82.50% sensitivity in identifying AML patients from normal controls. Furthermore, AML patients with higher serum EV-miR-10b expression had significantly shorter survival and serum EV-miR-10b was demonstrated to be an independent prognostic marker for overall survival in AML.

CONCLUSIONS

Taken together, serum EV-miR-10b might serve as a promising biomarker for predicting the prognosis of AML.

Concise Review: Regulation of Self-Renewal in Normal and Malignant Hematopoietic Stem Cells by Krüppel-Like Factor 4

Pluripotent and tissue‐specific stem cells, such as blood‐forming stem cells, are maintained through a balance of quiescence, self‐renewal, and differentiation. Self‐renewal is a specialized cell division that generates daughter cells with the same features as the parental stem cell. Although many factors are involved in the regulation of self‐renewal, perhaps the most well‐known factors are members of the Krüppel‐like factor (KLF) family, especially KLF4, because of the landmark discovery that this protein is required to reprogram somatic cells into induced pluripotent stem cells. Because KLF4 regulates gene expression through transcriptional activation or repression via either DNA binding or protein‐to‐protein interactions, the outcome of KLF4‐mediated regulation largely depends on the cellular context, cell cycle regulation, chromatin structure, and the presence of oncogenic drivers. This study first summarizes the current understanding of the regulation of self‐renewal by KLF proteins in embryonic stem cells through a KLF circuitry and then delves into the potential function of KLF4 in normal hematopoietic stem cells and its emerging role in leukemia‐initiating cells from pediatric patients with T‐cell acute lymphoblastic leukemia via repression of the mitogen‐activated protein kinase 7 pathway. stem cells translational medicine2019;8:568–574

NPM1A in Plasma is a Potential Prognostic Biomarker in Acute Myeloid Leukemia

Objective

The aim of the study was to investigate whether nucleophosmin type A mutation (NPM1A) in plasma was associated with the prognosis of patients with acute myeloid leukemia (AML).

Methods

Plasma NPM1A levels were investigated in 80 AML patients, 22 patients with benign hematopathy and 12 healthy donors by qRT-PCR. Additionally, the relationship between NPM1A levels and clinic characteristics were evaluated by Chi-square test. Kaplan-Meier method was used to analyze overall survival (OS) and relapse-free survival (RFS), and univariate and multivariate analyses were performed with Cox proportional hazard model.

Results

Plasma levels of NPM1A in AML patients were significantly higher than those in benign hematopathy patients and healthy controls, respectively (both P<0.001). Additionally, high NPM1A level was significantly associated with higher WBC and platelet count (both, P<0.05). Moreover, survival analysis revealed that patients with high NPM1A levels had worse OS (P<0.001) and RFS (P<0.001). Multivariate analysis identified NPM1A as an independent prognostic predictor for AML (OS: HR=8.214, 95% CI: 2.974-22.688, P<0.001; RFS: HR=4.640, 95%CI: 1.825-11.795, P=0.001).

Conclusions

Results reveal that NPM1A in plasma could serve as an ideal tool for predicting the prognosis of patients with AML.

The interplay between critical transcription factors and microRNAs in the control of normal and malignant myelopoiesis

Myelopoiesis is a complex process driven by essential transcription factors, including C/EBPα, PU.1, RUNX1, KLF4 and IRF8. Together, these factors are critical for the control of myeloid progenitor cell expansion and lineage determination in the development of granulocytes and monocytes/macrophages. MicroRNAs (miRNAs) are expressed in a cell type and lineage specific manner. There is increasing evidence that miRNAs fine-tune the expression of hematopoietic lineage-specific transcription factors and drive the lineage decisions of hematopoietic progenitor cells. In this review, we discuss recently discovered self-activating and feed-back mechanisms in which transcription factors and miRNAs interact during myeloid cell development. Furthermore, we delineate how some of these mechanisms are affected in acute myeloid leukemia (AML) and how disrupted transcription factor-miRNA interplays contribute to leukemogenesis.

INPP4B promotes cell survival via SGK3 activation in NPM1-mutated leukemia

Background

Acute myeloid leukemia (AML) with mutated nucleophosmin (NPM1) has been recognized as a distinct leukemia entity in the 2016 World Health Organization (WHO) classification. The genetic events underlying oncogenesis in NPM1-mutated AML that is characterized by a normal karyotype remain unclear. Inositol polyphosphate 4-phosphatase type II (INPP4B), a new factor in the phosphoinositide-3 kinase (PI3K) pathway-associated cancers, has been recently found a clinically relevant role in AML. However, little is known about the specific mechanistic function of INPP4B in NPM1-mutated AML.

Methods

The INPP4B expression levels in NPM1-mutated AML primary blasts and AML OCI-AML3 cell lines were determined by qRT-PCR and western blotting. The effect of INPP4B knockdown on OCI-AML3 leukemia cell proliferation was evaluated, using the Cell Counting Kit-8 and colony formation assay. After INPP4B overexpression or knockdown, the activation of serum and glucocorticoid-regulated kinase 3 (SGK3) and AKT was assessed. The effects of PI3K signaling pathway inhibitors on the levels of p-SGK3 in OCI-AML3 cells were tested. The mass of PI (3,4) P₂ and PI (3) P was analyzed by ELISA upon INPP4B overexpression. Knockdown of SGK3 by RNA interference and a rescue assay were performed to confirm the critical role of SGK3 in INPP4B-mediated cell survival. In addition, the molecular mechanism underlying INPP4B expression in NPM1-mutated leukemia cells was explored. Finally, Kaplan–Meier survival analysis was conducted on the NPM1-mutated AML cohort stratified into quartiles for INPP4B expression in The Cancer Genome Atlas (TCGA) dataset.

Results

High expression of INPP4B was observed in NPM1-mutated AML. Knockdown of INPP4B repressed cell proliferation in OCI-AML3 cells, whereas recovered INPP4B rescued this inhibitory effect in vitro. Mechanically, INPP4B enhanced phosphorylated SGK3 (p-SGK3) status, but did not affect AKT activation. SGK3 was required for INPP4B-induced cell proliferation in OCI-AML3 cells. High levels of INPP4B were at least partially caused by the NPM1 mutant via ERK/Ets-1 signaling. Finally, high expression of INPP4B showed a trend towards lower overall survival and event-free survival in NPM1-mutated AML patients.

Conclusions

Our results indicate that INPP4B promotes leukemia cell survival via SGK3 activation, and INPP4B might be a potential target in the treatment of NPM1-mutated AML.

NPM1 Mutant Mediated PML Delocalization and Stabilization Enhances Autophagy and Cell Survival in Leukemic Cells

Accumulating evidence has defined nucleophosmin 1 (NPM1) mutation as a driver genetic event in acute myeloid leukemia (AML), whereas the pathogenesis of NPM1-mutated AML remains to be fully elucidated. In this study, we showed that mutant NPM1 elevated autophagic activity and autophagic activation contributed to leukemic cell survival in vitro. Meanwhile, we also found high expression of promyelocytic leukemia gene (PML) and its cytoplasmic dislocation in primary NPM1-mutated AML blasts and NPM1-mA positive OCI-AML3 cells. Mechanically, mutant NPM1 interacted with PML and mediated it delocalization as well as stabilization. Notably, NPM1-mA knockdown impaired autophagic activity, while induced expression of PML reversed this effect. Finally, we confirmed that PML modulated autophagic activity via AKT signal. These findings suggest that aberrant PML expression and autophagy are beneficial to the leukemic transformation driven by NPM1 mutations. This indicates an attractive therapeutic avenue for PML targeting and/or autophagy inhibition in the treatment of NPM1-mutated AML.