Cytoplasmic expression of nucleophosmin accurately predicts mutation in the nucleophosmin gene in patients with acute myeloid leukemia and normal karyotype

Frequency of Nucleophosmin 1 Expression by Immunohistochemistry in Acute Myeloid Leukemia

Nucleophosmin (NPM1) mutation is one of the most common recurring genetic abnormalities seen in acute myeloid leukemia (AML). Immunohistochemistry serves as a cost effective and simple surrogate testing method for detection of NPM1 mutation. This study was conducted to evaluate the frequency of aberrant cytoplasmic nucleophosmin 1 expression in leukemic blast cells on formalin fixed bone marrow trephine biopsy (BMB) sections and also to correlate this data with the reference molecular method (reverse transcriptase-polymerase chain reaction; RT-PCR and gene sequencing), where available. Immunostains were performed using mouse anti-NPM1 monoclonal antibody on 71 paraffin embedded bone marrow biopsies (BMB) of patients with AML of any French-American-British (FAB) subtype. Results of immunohistochemistry (IHC) were then compared with the reference molecular method. The proportion of NPM1 expression by immunostaining in AML cases was found to be 17%. Twelve of the total 71 cases demonstrated cytoplasmic nucleophosmin (NPMc+) on immunostaining. Eleven of the positive cases that were correlated with the molecular standard demonstrated mutation in exon 12 of NPM1 gene. Cytoplasmic nucleophosmin expression by immunostaining was found to be in complete agreement with the standard molecular method. In a resource restricted setup, the information from this study might help in providing an inexpensive and accurate detection method to facilitate introduction of this marker in diagnostic and prognostic workup of AML especially in patients showing normal karyotype and no common recurrent translocations.

Nucleophosmin1 (NPM1) abnormality in hematologic malignancies, and therapeutic targeting of mutant NPM1 in acute myeloid leukemia

Nucleophosmin (NPM1) is an abundant nucleolar protein that is implicated in a variety of biological processes and in the pathogenesis of several human malignancies. For hematologic malignancies, approximately one-third of anaplastic large-cell non-Hodgkin’s lymphomas were found to express a fusion between NPM1 and the catalytic domain of anaplastic lymphoma receptor tyrosine kinase. About 50–60% of acute myeloid leukemia patients with normal karyotype carry NPM1 mutations, which are characterized by cytoplasmic dislocation of the NPM1 protein. Nevertheless, NPM1 is overexpressed in various hematologic and solid tumor malignancies. NPM1 overexpression is considered a prognostic marker of recurrence and progression of cancer. Thus, NPM1 abnormalities play a critical role in several types of hematologic malignancies. This has led to intense interest in the development of an NPM1 targeting strategy for cancer therapy. The aim of this review is to summarize present knowledge on NPM1 origin, pathogenesis, and therapeutic interventions in hematologic malignancies.

The past, present, and future of CRM1/XPO1 inhibitors

Therapies targeted at inhibiting nucleo-cytoplasmic transport have found broad applications in the field of oncology. Chromosome region maintenance 1 (CRM1), better known as exportin 1 (XPO1), is the protein transporter responsible for the nucleo-cytoplasmic shuttling of most of the tumor suppressor proteins (TSP) and growth regulatory factors. XPO1 is also upregulated in many malignancies and associated with a poor prognosis. Its inhibition has been a target of therapy, and hence, the selective inhibitors of nuclear transport (SINE) compounds were developed as a novel class of anti-cancer agents. The most well-known SINE agent is selinexor (KPT-330) and has been widely tested in phase I and II clinical trials in both solid tumors and hematologic malignancies. This review discusses how dysregulation of XPO1 promotes tumorigenesis, the historical considerations in the development of SINE compounds, and their role in current clinical therapies.

Nucleophosmin modulates the alleviation of atopic dermatitis caused by the marine-derived compound dihydroaustrasulfone alcohol

Atopic dermatitis (AD) is a chronic inflammatory skin disease, and its prevalence is increasing. AD usually elicits skin barrier dysfunction, dry skin and itching. As the mechanisms of AD remain unknown, there is an urgent need to find effective therapies. Because of the diversity and complexity of marine environments, the discovery of drugs from marine organisms as novel therapeutic agents for human diseases has seen renewed interest. Dihydroaustrasulfone alcohol (WA-25), the synthetic precursor of austrasulfone, which is a natural product isolated from a Formosan soft coral, has been shown to possess many therapeutic effects in our previous studies. However, the detailed mechanisms and therapeutic effects of WA-25 on AD are incompletely understood. We performed in vitro and in vivo studies to examine the effects of WA-25 on AD. We showed that WA-25 blocks inflammation and oxidative stress. Simultaneously, we also found that WA-25 reduces the AD scores and AD-induced transepidermal water loss (TEWL), scratching behavior, and alloknesis. WA-25 is more effective in cases of AD than are the drugs that are currently used clinically. Importantly, we also found that when nucleophosmin (NPM) was inhibited or when its expression was reduced, the anti-inflammatory and anti-AD effects of WA-25 were blocked. These data suggest that NPM plays dual roles in inflammation and AD. Overall, these results suggest that WA-25 is a potential anti-inflammatory and AD therapeutic agent that is modulated by NPM.

Nucleophosmin mutation analysis in acute myeloid leukaemia: Immunohistochemistry as a surrogate for molecular techniques

Background & objectives:

Mutation of nucleophosmin (NPM1) gene in the absence of FLT3-ITD (FMS related tyrosine kinase 3 - internal tandem duplications) mutation carries a good prognosis in cytogenetically normal acute myeloid leukaemia (AML). NPM1, a multifunctional nucleolar phosphoprotein that shuttles between nucleus and cytoplasm, gets trapped in the cytoplasm when mutated. Immunohistochemical (IHC) demonstration of its aberrant cytoplasmic location (NPMc+) has been suggested as a simple substitute for the standard screening molecular method. This study was aimed to assess the diagnostic utility of IHC on formalin fixed bone marrow biopsies in comparison with the reference molecular method (allele specific oligonucleotide - polymerase chain reaction; ASO-PCR) to predict NPM1 mutation status in AML patients.

Methods:

NPM protein IHC was performed using mouse anti-NPM monoclonal antibody on 35 paraffin-embedded bone marrow biopsies of patients with primary AML of any French-American-British (FAB) subtype. Results of IHC were compared with those of ASO-PCR.

Results:

Of the 35 AML patients, 21 (60%) were positive for NPM1 exon 12 gene mutation by ASO-PCR, 19 (90.47%) of these 21 were NPMc+. Thirteen of the 35 patients were negative by both the methods. One NPMc+ patient was not detected by ASO-PCR. IHC had a sensitivity and specificity of 90 and 93 per cent, respectively, compared to the molecular screening gold standard.

Interpretation & conclusions:

Mutation of NPM1 determined by the widely available and inexpensive IHC agrees closely with results of the standard molecular methods. Thus, technically and financially not well endowed laboratories can provide the prognostically and potentially therapeutically important information on NPM1 mutation using IHC.

Immunohistochemical detection of cytoplasmic nucleophosmin in formalin-fixed paraffin-embedded marrow trephine biopsies in acute myeloid leukaemia

AIMS

Nucleophosmin (NPM1) gene mutations resulting in cytoplasmic delocalisation of nucleophosmin (NPMc+) are the most common genetic abnormality in acute myeloid leukaemia (AML). In this study, we tested whether immunohistochemical (IHC) detection of cytoplasmic NPM1 (cNPM1) in formalin-fixed bone marrow trephine biopsies correlated with NPM1 mutations and the prognostic impact of NPM1 and fms-related tyrosine kinase 3-internal tandem duplication (FLT3-ITD) gene mutations was also assessed.

METHODS

A total of 71 Chinese adult de novo AML cases were evaluated for cNPM1 by IHC where the bone marrow trephines were fixed in 10% buffered formalin and decalcified by 5% EDTA. NPM1 and FLT3-ITD gene mutations were also investigated using PCR, fragment analysis and direct DNA sequencing.

RESULTS

IHC analysis of cNPM1 had a very good sensitivity (86.7%) and excellent specificity (96.4%) for NPM1 mutation. The positive predictive value was 86.7% and the negative predictive value was 96.4%. NPM1 mutations and FLT3-ITD were closely associated (p = 0.003). Patients with mutated NPM1 and without FLT3-ITD mutation have a longer overall survival (p = 0.042) than patients with both NPM1 and FLT3-ITD mutations.

CONCLUSIONS

Our results showed that IHC detection of cNPM1 in formalin-fixed trephine biopsies correlated well but not entirely with NPM1 mutation. Furthermore, NPM1 mutations were significantly more frequent in FLT3-ITD than FLT3-wild-type cases.

Immunohistochemical Detection of NPM1 Mutation in Acute Myeloid Leukemia and its Association With Cup-like Nuclear Morphology of Blasts

Blasts showing cup-like nuclei in acute myeloid leukemia (AML) have been identified in patients with nucleophosmin 1 gene (NPM1) mutation, that is, AML with cytoplasmic NPM (NPMc+ AML). We analyzed 100 consecutive cases of AML, and defined the cutoff percentages of cup-like blasts in peripheral blood and bone marrow aspirate smears that can predict NPMc+ AML. A lower cutoff level of ≥10% blasts in peripheral blood and ≥9% in bone marrow aspirate gave an excellent specificity for NPMc+ AML and a positive-predictive value of 90.9% and a negative-predictive value of 87.6% for NPMc+ AML. Cup-like nuclei were associated with higher total leukocyte count, higher blasts percentage, AML-M1 subtype, and human leukocyte antigen-DR region negativity. Our results suggest that cup-like nuclei represent an important morphologic clue that can predict NPMc+ AML and guide toward prioritizing the further workup of AML patients.

Selective inhibitors of nuclear export (SINE) in hematological malignancies

Regulated nucleo-cytoplasmic transport plays a major role in maintaining cellular homeostasis. CRM1 (chromosome region maintenance 1 or exportin 1 or XPO 1) is responsible for the nucleo-cytoplasmic transport of more than 200 proteins, including most of the tumor suppressor proteins (TSP). CRM1 is overexpressed in pancreatic cancer, osteosarcoma, glioma, cervical and hematological malignancies. This inspired the development of novel agents that selectively inhibit nuclear exportins (SINEs). In this review we focus on the significance of CRM1 in carcinogenesis and review the new development of SINE inhibitiors in hematological malignancies. Selinexor (KPT-330) as the first-in-human SINE agent represents this novel class of anti-cancer agents.

Prognostic involvement of nucleophosmin mutations in acute myeloid leaukemia

Nucleophosmin (NPM1) is a protein of highly conserved nature which works as a molecular chaperone and is mostly found in nucleoli. NPM also involved in the maturation of preribosomes and duplication of centrosomes. Furthermore, it is also active in control and regulation of the ARF-p53 tumor suppressor pathway. A high rate of incidence and prognostic involvement is reported by various authors in AML patients. In AML it behaves as a favorable prognostic marker. NPM mutations are more frequently associated with normal-karyotype AML and are usually absent in patients having abnormal or poor cytogenetic. NPM mutations are not frequent in other hematopoietic tumors .Two main types of mutations have been described to date. Both of these cause abnormal cytoplasmic localization of NPM1. Their high incidence rate in normal karyoptype and their favorable nature make those mutations hot spot or front face mutations which should be checked before treatment starts.

NPM1 Gene Type A Mutation in Bulgarian Adults with Acute Myeloid Leukemia: A Single-Institution Study

Objective: Mutations of the nucleophosmin (NPM1) gene are considered as the most frequent acute myeloid leukemia (AML)-associated genetic lesion, reported with various incidences in different studies, and type A (NPM1-A) is the most frequent type. However, since most series in the literature report on the features of all patients regardless of the type of mutation, NPM1-A(+) cases have not been well characterized yet. Therefore, we evaluated the prevalence of NPM1-A in Bulgarian AML patients and searched for an association with clinical and laboratory features.

Materials and Methods: One hundred and four adults (51 men, 53 women) were included in the study. NPM1-A status was determined using allele-specific reverse-transcription polymerase chain reaction with co-amplification of NPM1-A and β-actin and real-time quantitative TaqMan-based polymerase chain reaction. Patients received conventional induction chemotherapy and were followed for 13.2±16.4 months.

Results: NPM1-A was detected in 26 (24.8%) patients. NPM1-A mutation was detected in all AML categories, including in one patient with RUNX1-RUNX1T1. There were no differences associated with the NPM1-A status with respect to age, sex, hemoglobin, platelet counts, percentage of bone marrow blasts, splenomegaly, complete remission rates, and overall survival. NPM1-A(+) patients, compared to NPM1-A(-) patients, were characterized by higher leukocyte counts [(75.4±81.9)x109/L vs. (42.5±65.9)x109/L; p=0.049], higher frequency of normal karyotype [14/18 (77.8%) vs. 26/62 (41.9%); p=0.014], higher frequency of FLT3-ITD [11/26 (42.3%) vs. 8/77 (10.4%); p=0.001], and lower incidence of CD34(+) [6/21 (28.8%) vs. 28/45 (62.2%); p=0.017]. Within the FLT3-ITD(-) group, the median overall survival of NPM1-A(-) patients was 14 months, while NPM1-A(+) patients did not reach the median (p=0.10).

Conclusion: The prevalence of NPM1-A mutation in adult Bulgarian AML patients was similar to that reported in other studies. NPM1-A(+) patients were characterized by higher leukocyte counts, higher frequency of normal karyotypes and FLT3-ITD, and lower incidence of CD34(+), supporting the idea that the specific features of type A mutations might contribute to the general clinical and laboratory profile of NPM1(+) AML patients.

A surrogate marker to detect nucleophosnim (NPM1) gene mutations in the cytoplasm of acute myeloid leukemia (AML) blast cells in 30 adult Iraqi patients

BACKGROUND AND OBJECTIVES

Acute myeloid leukemia (AML) with mutated nucleophosmin (NPM) gene has distinctive clinical and molecular features, and enormous advances have been achieved in the methods of diagnosing this new entity. This prospective study was designed to detect the mutant NPM protein using immunohistochemical staining in AML patients and to evaluate its application as a surrogate marker for NPM1 gene mutation analysis.

DESIGN AND SETTINGS

This is a prospective study at a general community hospital in Baghdad (Baghdad Teaching Hospital) during the period from March 2011 to July 2011.

PATIENTS AND METHODS

Immunohistochemical staining was used to detect the mutant NPM protein in bone marrow biopsies fixed in Bouin solution from 30 adult AML patients using anti-NPM polyclonal antibody. Molecular analysis was done on bone marrow or peripheral blood samples from 16/30 (53%) patients using single strand confirmatory polymorphism-reverse transcriptase-polymerase chain reaction (SSCP-RT-PCR).

RESULTS

Using Immunohistochemical staining, 17/30 (56.7%) of AML patients were positive for the mutant NPM protein. The percentage of positive blast cells ranged from 30% to 100%. A significant relation was found between RT-PCR analysis and immunohistochemical staining (P=.009). The sensitivity of Immunohistochemical staining in detection of mutated NPM1 cases was 90%, whereas the specificity of this technique was 87.5%.

CONCLUSION

The findings of immunohistochemical staining of NPM protein were significantly related with the molecular findings of NPM1 gene analysis, and the immunohistochemical staining technique was both sensitive and specific. These findings might be a prime step for the future utilization of this technique as a surrogate marker for the detection of NPM1 gene mutations in under-resourced countries as Iraq. Still, a larger study recruiting a larger number of patients will be useful for the assessment of the significance of immunohistochemical staining in the detection of minimal residual disease in NPM cytoplasmic positive AML, which is a good prognostic entity.

A single center analysis of nucleophosmin in acute myeloid leukemia: value of combining immunohistochemistry with molecular mutation analysis

Mutations of nucleophosmin 1 are frequently found in acute myeloid leukemia and lead to aberrant cytoplasmic accumulation of nucleophosmin protein. Immunohistochemical staining is therefore recommended as the technique of choice in front-line screening. In this study, we assessed the sensitivity and specificity of immunohistochemistry on formalin-fixed bone marrow biopsies compared with gold standard molecular analysis to predict nucleophosmin 1 mutation status in 119 patients with acute myeloid leukemia. Discrepant cases were further characterized by gene expression analyses and fluorescence in situ hybridization. A large overlap between both methods was observed. Nevertheless, nine patients demonstrated discordant results at initial screening. Five cases demonstrated nuclear staining of nucleophosmin 1 by immunohistochemistry, but a nucleophosmin 1 mutation by molecular analysis. In two cases this could be attributed to technical issues and in three cases minor subpopulations of myeloblasts had not been discovered initially. All tested cases exhibited the characteristic nucleophosmin-mutated gene expression pattern. Four cases had cytoplasmic nucleophosmin 1 staining and a nucleophosmin-mutated gene expression pattern without a detectable nucleophosmin 1 mutation. In two of these cases we found the chromosomal translocation t(3;5)(q25;q35) encoding the NPM-MLF1 fusion protein. In the other discrepant cases the aberrant cytoplasmic nucleophosmin staining and gene expression could not be explained. In total six patients (5%) had true discordant results between immunohistochemistry and mutation analysis. We conclude that cytoplasmic nucleophosmin localization is not always caused by a conventional nucleophosmin 1 mutation and that in the screening for nucleophosmin 1 abnormalities, most information will be obtained by combining immunohistochemistry with molecular analysis.

Prognostic impact of NPM1 mutations in Serbian adult patients with acute myeloid leukemia

Based on current findings, the presence of NPM1 mutations in acute myeloid leukemia (AML) patients is associated with an increased probability of complete remission (CR) and better overall survival (OS). We determined the incidence and prognostic relevance of NPM1 mutations, their association with FLT3 and IDH mutations, and other clinical characteristics in Serbian adult AML patients. Samples from 111 adult de novo AML patients, including 73 AML cases with a normal karyotype (NK-AML), were studied. NPM1, FLT3, and IDH mutations were detected by PCR and direct sequencing. NPM1 mutations were detected in 22.5% of patients. The presence of NPM1 mutations predicted a low CR rate and shorter OS. NPM1 mutations showed an association with both FLT3 and IDH mutations. Survival analysis based on NPM1/FLT3 mutational status revealed a lower OS for NPM1(+)/FLT3(-) compared to the NPM1(-)/FLT3(-) group in NK-AML patients. The lack of impact or unfavorable prognostic effect of NPM1 mutations found in this study can be assigned to a small cohort of analyzed AML patients, as can the presence of FLT3 and IDH mutations or other genetic lesions that cooperate with NPM1 mutations influencing prognosis.

Identification of NPMc+ acute myeloid leukemia in bone marrow smears

The most frequent genetic change currently known in acute myeloid leukemia (AML) is the mutation of the nucleophosmin (NPM) gene. Aberrant cytoplasmic accumulation of NPM protein (NPMc+) is the result of this mutation, and it can be demonstrated by immunohistochemistry for the identification of a favorable subgroup within "AML with normal karyotype" according to the World Health Organization classification. NPM staining pattern was defined in 71 AML and 15 control cases by the use of bone marrow smears in order to overcome limitations observed due to immunohistochemistry. In 13/71 cases (18.3%), clear cytoplasmic staining of the leukemic blast cells was detectable that was comparable with the positivity of mitotic figures physiologically lacking nuclear membrane. The biological and genetic characteristics of the NPMc+ cases determined this way were identical with the previously published results including low CD34 and HLA-DR expression and lack of recurrent karyotype abnormalities. Bone marrow smears are well applicable and therefore a real alternative for the determination of NPM with the highest accuracy for optimal risk stratification in AML.

Regulation of subcellular distribution and oncogenic potential of nucleophosmin by plakoglobin

Nucleophosmin (NPM) is a nucleolar phosphoprotein that is involved in many cellular processes and has both oncogenic and growth suppressing activities. NPM is localized primarily in nucleoli but shuttles between the nucleus and the cytoplasm, and sustained cytoplasmic distribution contributes to its tumor promoting activities. Plakoglobin (PG, γ-catenin) is a homolog of β-catenin with dual adhesive and signaling functions. These proteins interact with cadherins and mediate adhesion, while their signaling activities are regulated by association with various intracellular partners. Despite these similarities, β-catenin has a well-defined oncogenic activity, whereas PG acts as a tumor/metastasis suppressor through unknown mechanisms. Comparison of the proteomic profiles of carcinoma cell lines with low- or no PG expression with their PG-expressing transfectants has identified NPM as being upregulated upon PG expression. Here, we examined NPM subcellular distribution and in vitro tumorigenesis/metastasis in the highly invasive and very low PG expressing MDA-MB-231 (MDA-231) breast cancer cells and their transfectants expressing increased PG (MDA-231-PG) or NPM shRNA (MDA-231-NPM-KD) or both (MDA-231-NPM-KD+PG). Increased PG expression increased the levels of nucleolar NPM and coimmunoprecipitation studies showed that NPM interacts with PG. PG expression or NPM knockdown decreased the growth rate of MDA-231 cells substantially and this reduction was decreased further in MDA-231-NPM-KD+PG cells. In in vitro tumorigenesis/metastasis assays, MDA-231-PG cells showed substantially lower and MDA-231-NPM-KD cells substantially higher invasiveness relative to the MDA-231 parental cells, and the co-expression of PG and NPM shRNA led to even further reduction of the invasiveness of MDA-231-PG cells. Furthermore, examination of the levels and localization of PG and NPM in primary biopsies of metastatic infiltrating ductal carcinomas revealed coordinated expression of PG and NPM. Together, the data suggest that PG may regulate NPM subcellular distribution, which may potentially change the function of the NPM protein from oncogenic to tumor suppression.

Acute myeloid leukemia with mutated nucleophosmin (NPM1): is it a distinct entity?

After the discovery of NPM1-mutated acute myeloid leukemia (AML) in 2005 and its subsequent inclusion as a provisional entity in the 2008 World Health Organization classification of myeloid neoplasms, several controversial issues remained to be clarified. It was unclear whether the NPM1 mutation was a primary genetic lesion and whether additional chromosomal aberrations and multilineage dysplasia had any impact on the biologic and prognostic features of NPM1-mutated AML. Moreover, it was uncertain how to classify AML patients who were double-mutated for NPM1 and CEBPA. Recent studies have shown that: (1) the NPM1 mutant perturbs hemopoiesis in experimental models; (2) leukemic stem cells from NPM1-mutated AML patients carry the mutation; and (3) the NPM1 mutation is usually mutually exclusive of biallelic CEPBA mutations. Moreover, the biologic and clinical features of NPM1-mutated AML do not seem to be significantly influenced by concomitant chromosomal aberrations or multilineage dysplasia. Altogether, these pieces of evidence point to NPM1-mutated AML as a founder genetic event that defines a distinct leukemia entity accounting for approximately one-third of all AML.