FLT3 internal tandem duplication associates with adverse outcome and gene- and microRNA-expression signatures in patients 60 years of age or older with primary cytogenetically normal acute myeloid leukemia: a Cancer and Leukemia Group B study. Blood. 2010;116:3622-3626. [PMID: 20656931 DOI: 10.1182/blood-2010-05-283648]

Detection of internal tandem duplications in the FLT3 gene by different electrophoretic methods

BACKGROUND

In acute myeloid leukemia (AML), the internal tandem duplication (ITD) in the juxtamembrane domain of the FLT3 (Fms-like tyrosine kinase 3) gene is one of the most frequent genetic alterations associated with poor prognosis.

METHODS

A complex evaluation of the analytical properties of the three most frequently used detection methods--PCR followed by agarose (AGE), polyacrylamide (PAGE) or capillary electrophoresis (CE)--was performed on 95 DNA samples obtained from 73 AML patients.

RESULTS

All the three methods verified the presence of a mutant allele in 20 samples from 18 patients. AGE and PAGE could detect the presence of 1%-2% mutant allele, while the detection limit of CE was 0.28%. However, acceptable reproducibility (inter-assay CV <25%) of the mutant allele rate determination was only achievable above 1.5% mutant/total allele rate. The reproducibility of the ITD size determination by CE was much better, but the ITD size calculated by PeakScanner or GeneScan analysis was 7% lower as compared to values obtained by DNA sequencing. The presence of multiple ITD was over-estimated by PAGE and AGE due to the formation of heteroduplexes.

CONCLUSIONS

This study suggests the use of PCR+CE in the diagnostics and the follow-up of AML patients. The data further supports the importance of proper analytical evaluation of home-made molecular biological diagnostic tests.

ASXL1 mutations identify a high-risk subgroup of older patients with primary cytogenetically normal AML within the ELN Favorable genetic category

The associations of mutations in the enhancer of trithorax and polycomb family gene ASXL1 with pretreatment patient characteristics, outcomes, and gene-/microRNA-expression profiles in primary cytogenetically normal acute myeloid leukemia (CN-AML) are unknown. We analyzed 423 adult patients for ASXL1 mutations, other prognostic gene mutations, and gene-/microRNA-expression profiles. ASXL1 mutations were 5 times more common in older (≥ 60 years) patients (16.2%) than those younger than 60 years (3.2%; P < .001). Among older patients, ASXL1 mutations associated with wild-type NPM1 (P < .001), absence of FLT3-internal tandem duplications (P = .002), mutated CEBPA (P = .01), and with inferior complete remission (CR) rate (P = .04), disease-free survival (DFS; P = .03), overall survival (OS; P = .006), and event-free survival (EFS; P = .002). Within the European LeukemiaNet (ELN) genetic categories of older CN-AML, ASXL1 mutations associated with inferior CR rate (P = .02), OS (P < .001), and EFS (P < .001) among ELN Favorable, but not among ELN Intermediate-I patients. Multivariable analyses confirmed associations of ASXL1 mutations with unfavorable CR rate (P = .03), DFS (P < .001), OS (P < .001), and EFS (P < .001) among ELN Favorable patients. We identified an ASXL1 mutation-associated gene-expression signature, but no microRNA-expression signature. This first study of ASXL1 mutations in primary CN-AML demonstrates that ASXL1-mutated older patients, particularly within the ELN Favorable group, have unfavorable outcomes and may be candidates for experimental treatment approaches.

Clinical outcome and gene- and microRNA-expression profiling according to the Wilms tumor 1 (WT1) single nucleotide polymorphism rs16754 in adult de novo cytogenetically normal acute myeloid leukemia: a Cancer and Leukemia Group B study

BACKGROUND

The alleles of the Wilms tumor 1 (WT1) polymorphism rs16754 harbor adenine (A) or guanine (G). Recently, rs16754 has been reported to affect the outcome of patients with cytogenetically normal acute myeloid leukemia. To validate this finding, we investigated pretreatment features and outcome associated with rs16754 in a large cohort of patients with cytogenetically normal acute myeloid leukemia.

DESIGN AND METHODS

Four-hundred and thirty-three intensively treated and molecularly characterized cytogenetically normal patients with de novo acute myeloid leukemia (18-83 years old) were analyzed for rs16754. To gain biological insights, we studied the gene- and microRNA-expression profiles for associations with rs16754.

RESULTS

Three-hundred and nine (71%) patients were homozygous for A (WT1(AA)), 112 (26%) were heterozygous (WT1(AG)) and 12 (3%) were homozygous for G (WT1(GG)). For comparison with previous studies, we grouped WT1(AG) and WT1(GG) patients and compared them with WT1(AA) patients divided into younger (<60 years) and older (≥60 years) adults. We found no independent prognostic impact of WT1(AA). However, WT1(GG) patients, who were less often Caucasian than WT1(AG) (P=0.001) or WT1(AA) (P=0.008) patients, and had TET2 mutations more often than WT1(AG) (P=0.02) patients, had, among patients with FLT3-internal tandem duplication and/or NPM1 wild-type, better disease-free (P=0.02) and overall survival (P=0.04) than WT1(AA) and WT1(AG) patients combined. Unsupervised and supervised analyses of the gene- and microRNA-expression profiles suggested that there were no distinct expression patterns associated with any rs16754 genotype.

CONCLUSIONS

We did not observe the previously reported adverse impact of WT1(AA) but found favorable outcomes associated with the homozygous WT1(GG). Considering its low frequency, confirmatory studies are necessary. The biological significance of rs16754 remains questionable as no distinct expression profiles were associated with the genotypes.

Micro RNAs as a new therapeutic target towards leukaemia signalling

Micro RNAs (miRNAs) have emerged as potentially useful and specific agents to regulate transcriptional control of many cellular genes. There is a real prospect that miRNA and other short-length RNA reagents could be useful in a therapeutic setting. Here we outline the control of miRNAs in acute myeloid leukaemia (AML) subtype of human leukaemia, and ask whether miRNA could be important either in the generation of an AML phenotype, or as a variety of agents to combat the disease in the clinic. The use of miRNAs as potential biomarkers of aberrant signalling pathways involved in AML oncogenesis is also discussed.

High expression of IGFBP2 is associated with chemoresistance in adult acute myeloid leukemia

Insulin-like growth factor (IGF) signaling plays an important role in many tumors and overexpression of IGF Binding Protein (IGFBP) 2 has been associated with adverse outcome in childhood leukemia. Here, we evaluated IGFBP2 mRNA expression and its prognostic implications in 99 adult acute myeloid leukemia (AML) patients by quantitative real-time RT-PCR. High IGFBP2 was associated with a high incidence of primary resistant disease (IGFBP2 high 65%, IGFBP2 low 32%; P=0.02) and was independently predictive for therapy resistance [OR 3.6 (95% CI 1.2-11); P=0.02] in multivariate analyses. Gene-expression profiling revealed an up-regulation of genes implicated in leukemogenesis (MYB, MEIS1, HOXB3, HOXA9) and genes associated with adverse outcome (ERG, WT1) in patients with high IGFBP2 expression. Thus, our data suggest a role of IGFBP2 and IGF signaling in chemoresistance of AML. Patients with high IGFBP2 expression might benefit from molecular therapies targeting the IGF pathway.

Low expression of MN1 associates with better treatment response in older patients with de novo cytogenetically normal acute myeloid leukemia

Low MN1 expression bestows favorable prognosis in younger adults with cytogenetically normal acute myeloid leukemia (CN-AML), but its prognostic significance in older patients is unknown. We analyzed pretherapy MN1 expression in 140 older (≥ 60 years) de novo CN-AML patients treated on cytarabine/daunorubicin-based protocols. Low MN1 expressers had higher complete remission (CR) rates (P = .001), and longer overall survival (P = .03) and event-free survival (EFS; P = .004). In multivariable models, low MN1 expression was associated with better CR rates and EFS. The impact of MN1 expression on overall survival and EFS was predominantly in patients 70 years of age or older, with low MN1 expressers with mutated NPM1 having the best outcome. The impact of MN1 expression was also observed in the Intermediate-I, but not the Favorable group of the European LeukemiaNet classification, where low MN1 expressers had CR rates and EFS similar to those of Favorable group patients. MN1 expresser-status-associated gene- and microRNA-expression signatures revealed underexpression of drug resistance and adverse outcome predictors, and overexpression of HOX genes and HOX-gene-embedded microRNAs in low MN1 expressers. We conclude that low MN1 expression confers better prognosis in older CN-AML patients and may refine the European LeukemiaNet classification. Biologic features associated with MN1 expression may help identify new treatment targets.

Outcome of older adults with cytogenetically normal AML (CN-AML) and FLT3 mutations

AML patients under the age of 60 whose blasts harbor a FLT3 internal tandem duplication (ITD) mutation have a higher relapse rate and inferior survival compared to those without this mutation. To determine if FLT3ITD also carries a negative prognostic impact in older adults receiving therapies commonly used in this age group, we retrospectively analyzed outcomes of patients ≥60 years with CN-AML according to FLT3 mutation status. We identified 91 newly diagnosed CN-AML patients, 55 with wild-type FLT3 and 36 with FLT3ITD. Of the 91 patients, 36 received supportive care and/or experimental therapies while the remaining 55 received induction chemotherapy, followed by allogeneic SCT in 17 of these patients. Based on univariate analysis, advanced age at diagnosis was significantly associated with shorter overall survival (OS) (p<.0001) while intensive therapies were associated with improved OS (p<.0001). In a multivariate analysis that accounted for type of treatment, patient age, gender, and WBC count, FLT3ITD was significantly associated with shorter OS compared to wtFLT3 [p=.001; hazard ratio (HR)=2.23; 95% CI: 1.35-3.70]. Our data support the negative prognostic impact of FLT3ITD in older adults with CN-AML.

miR-29a and miR-142-3p downregulation and diagnostic implication in human acute myeloid leukemia

Expression profiling of microRNAs (miRNAs) in most diseases might be popular and provide the possibility for diagnostic implication, but few studies have accurately quantified the expression level of dysregulated miRNAs in acute myeloid leukemia (AML). In this study, we analyzed the peripheral blood mononuclear cells (PBMCs) from 10 AML patients (subtypes M1 to M5) and six normal controls by miRNA microarray and identified several differentially expressed miRNAs. Among them miR-29a and miR-142-3p were selectively encountered in Northern blot analysis and their significantly decreased expression in AML was further confirmed. Quantitative real-time PCR in 52 primarily diagnosed AML patients and 100 normal controls not only verified the expression properties of these 2 miRNAs, but also established that the expression level of miR-142-3p and miR-29a in PBMCs could be used as novel diagnostic markers. A better diagnostic outcome was achieved by combining miR-29a and miR-142-3p with about 90% sensitivity, 100% specificity, and an area under the ROC curve (AUC) of 0.97. Our results provide insights into the involvement of miRNAs in leukemogenesis, and offer candidates for AML diagnosis and therapeutic strategy.

An integrated genomic approach to the assessment and treatment of acute myeloid leukemia

Traditionally, new scientific advances have been applied quickly to the leukemias based on the ease with which relatively pure samples of malignant cells can be obtained. Currently, our arsenal of approaches used to characterize an individual's acute myeloid leukemia (AML) combines hematopathologic evaluation, flow cytometry, cytogenetic analysis, and molecular studies focused on a few key genes. The advent of high-throughput methods capable of full-genome evaluation presents new options for a revolutionary change in the way we diagnose, characterize, and treat AML. Next-generation DNA sequencing techniques allow full sequencing of a cancer genome or transcriptome, with the hope that this will be affordable for routine clinical care within the decade. Microarray-based testing will define gene and miRNA expression, DNA methylation patterns, chromosomal imbalances, and predisposition to disease and chemosensitivity. The vision for the future entails an integrated and automated approach to these analyses, bringing the possibility of formulating an individualized treatment plan within days of a patient's initial presentation. With these expectations comes the hope that such an approach will lead to decreased toxicities and prolonged survival for patients.

Repression of tumor suppressor miR-451 is essential for NOTCH1-induced oncogenesis in T-ALL

miR-451 represses expression of Myc and acts as a tumor suppressor in murine and human T cell acute lymphoblastic leukemia.

The NOTCH1 signaling pathway is a critical determinant of cell fate decisions and drives oncogenesis through mechanisms that are incompletely understood. Using an established mouse model of T cell acute lymphoblastic leukemia (T-ALL), here we report that induction of intracellular Notch1 (ICN1) leads to repression of miR-451 and miR-709. ICN1 decreases expression of these miRNAs by inducing degradation of the E2a tumor suppressor, which transcriptionally activates the genes encoding miR-451 and miR-709. Both miR-451 and miR-709 directly repress Myc expression. In addition, miR-709 directly represses expression of the Akt and Ras-GRF1 oncogenes. We also show that repression of miR-451 and miR-709 expression is required for initiation and maintenance of mouse T-ALL. miR-451 but not miR-709 is conserved in humans, and human T-ALLs with activating NOTCH1 mutations have decreased miR-451 and increased MYC levels compared with T-ALLs with wild-type NOTCH1. Thus, miR-451 and miR-709 function as potent suppressors of oncogenesis in NOTCH1-induced mouse T-ALL, and miR-451 influences MYC expression in human T-ALL bearing NOTCH1 mutations.

Emerging FMS-like tyrosine kinase 3 inhibitors for the treatment of acute myelogenous leukemia

INTRODUCTION

The FMS-like tyrosine kinase 3 (FLT3) is highly expressed in acute leukemias. Mutations involving FLT3 are among the most common molecular abnormalities in acute myelogenous leukemia (AML). Available evidence suggests that these molecular lesions confer a shorter disease-free survival and overall survival in patients with intermediate-risk cytogenetics. Therefore, substantial interest in FLT3 as a therapeutic target has led to the development of several promising inhibitors that target this tyrosine kinase.

AREAS COVERED

This review covers the molecular pathways associated with FLT3 activation in patients with AML, the biological rationale for inhibiting FLT3 and recent clinical progress with FLT3 inhibitors for the treatment of AML. Six FLT3 inhibitors undergoing clinical evaluation are discussed. A review of selected published manuscripts on the subject of FLT3 inhibition in AML and a search of the English language manuscripts in PubMed using the index words FLT3 and AML were conducted and articles of interest selected.

EXPERT OPINION

Mutated forms of FLT3, specifically FLT3-internal tandem duplication, have a significant impact on the prognosis of AML patients, particularly those with a normal karyotype. Inhibiting FLT3 may lead to clinical benefit for patients with AML. Newly developed FLT3 inhibitors have shown encouraging activity as monotherapy and in combination with other therapeutic agents.

Circulating MicroRNAs as Minimally Invasive Biomarkers for Cancer Theragnosis and Prognosis

Novel cancer biomarker discovery is urgently needed for cancer theragnosis and prognosis, and among the many possible types of samples, blood is regarded to be ideal for this discovery as it can be collected easily in a minimally invasive manner. Results of the past few years have ascertained the quantification of microRNA (miRNA) as a promising approach for the detection and prognostication of cancer. Indeed, an increasing number of studies have shown that circulating cancer-associated miRNAs are readily measured in plasma or serum and they can robustly discriminate cancer patients from healthy controls, as well as distinguishing between good-prognosis and poor-prognosis patients. Furthermore, recent findings also suggest the potential of circulating miRNAs in the screening, monitoring, and treatment of cancer. This article summarizes the most significant and latest discoveries of original researches on circulating miRNAs involvement in cancer, focusing on the potential of circulating miRNAs as minimally invasive biomarkers for cancer theragnosis and prognosis.

TET2 mutations improve the new European LeukemiaNet risk classification of acute myeloid leukemia: a Cancer and Leukemia Group B study

PURPOSE

To determine the frequency of TET2 mutations, their associations with clinical and molecular characteristics and outcome, and the associated gene- and microRNA-expression signatures in patients with primary cytogenetically normal acute myeloid leukemia (CN-AML).

PATIENTS AND METHODS

Four-hundred twenty-seven patients with CN-AML were analyzed for TET2 mutations by polymerase chain reaction and direct sequencing and for established prognostic gene mutations. Gene- and microRNA-expression profiles were derived using microarrays.

RESULTS

TET2 mutations, found in 23% of patients, were associated with older age (P < .001) and higher pretreatment WBC (P = .04) compared with wild-type TET2 (TET2-wt). In the European LeukemiaNet (ELN) favorable-risk group (patients with CN-AML who have mutated CEBPA and/or mutated NPM1 without FLT3 internal tandem duplication [FLT3-ITD]), TET2-mutated patients had shorter event-free survival (EFS; P < .001) because of a lower complete remission (CR) rate (P = .007), and shorter disease-free survival (DFS; P = .003), and also had shorter overall survival (P = .001) compared with TET2-wt patients. TET2 mutations were not associated with outcomes in the ELN intermediate-I-risk group (CN-AML with wild-type CEBPA and wild-type NPM1 and/or FLT3-ITD). In multivariable models, TET2 mutations were associated with shorter EFS (P = .004), lower CR rate (P = .03), and shorter DFS (P = .05) only among favorable-risk CN-AML patients. We identified a TET2 mutation-associated gene-expression signature in favorable-risk but not in intermediate-I-risk patients and found distinct mutation-associated microRNA signatures in both ELN groups.

CONCLUSION

TET2 mutations improve the ELN molecular-risk classification in primary CN-AML because of their adverse prognostic impact in an otherwise favorable-risk patient subset. Our data suggest that these patients may be candidates for alternative therapies.

Therapeutic advances in acute myeloid leukemia

The choice of treatment approach and outcome in acute myeloid leukemia (AML) depends on the age of the patient. In younger patients, arbitrarily defined as being younger than 60 years, 70% to 80% enter complete disease remission with several anthracycline-based chemotherapy combinations. Consolidation with high-dose cytarabine or stem-cell transplantation in high-risk patients will restrict overall relapse to approximately 50%. A number of demographic features can predict the outcome of treatment including cytogenetics and an increasing list of molecular features (ie, FLT3, NPM1, MLL, WT1, CEBPalpha, EVI1). These are increasingly being used to direct postinduction therapy, but they are also molecular targets for a new generation of small molecule inhibitors that are in early development; however, randomized data have yet to emerge. In older patients who comprise the majority, which will increase with demographic change, the initial clinical decision to be made is whether the patient should receive an intensive or nonintensive approach. If the same anthracycline/cytarabine-based approach is deployed, the remission rate will be around 50%, but the risk of subsequent relapse is approximately 85% at 3 years. This difference from younger patients is explained partly by the ability of patients to tolerate effective therapy, and also the aggregation of several poor risk factors compared with the young. There remains a substantial proportion of patients older than 60 years who do not receive intensive chemotherapy. Their survival is approximately 4 months, but there is considerable interest in developing new treatments for this patient group, including novel nucleoside analogs and several other agents.

Complete remission and early death after intensive chemotherapy in patients aged 60 years or older with acute myeloid leukaemia: a web-based application for prediction of outcomes

BACKGROUND

About 50% of patients (age ≥60 years) who have acute myeloid leukaemia and are otherwise medically healthy (ie, able to undergo intensive chemotherapy) achieve a complete remission (CR) after intensive chemotherapy, but with a substantially increased risk of early death (ED) compared with younger patients. We verified the association of standard clinical and laboratory variables with CR and ED and developed a web-based application for risk assessment of intensive chemotherapy in these patients.

METHODS

Multivariate regression analysis was used to develop risk scores with or without knowledge of the cytogenetic and molecular risk profiles for a cohort of 1406 patients (aged ≥60 years) with acute myeloid leukaemia, but otherwise medically healthy, who were treated with two courses of intensive induction chemotherapy (tioguanine, standard-dose cytarabine, and daunorubicin followed by high-dose cytarabine and mitoxantrone; or with high-dose cytarabine and mitoxantrone in the first and second induction courses) in the German Acute Myeloid Leukaemia Cooperative Group 1999 study. Risk prediction was validated in an independent cohort of 801 patients (aged >60 years) with acute myeloid leukaemia who were given two courses of cytarabine and daunorubicin in the Acute Myeloid Leukaemia 1996 study.

FINDINGS

Body temperature, age, de-novo leukaemia versus leukaemia secondary to cytotoxic treatment or an antecedent haematological disease, haemoglobin, platelet count, fibrinogen, and serum concentration of lactate dehydrogenase were significantly associated with CR or ED. The probability of CR with knowledge of cytogenetic and molecular risk (score 1) was from 12% to 91%, and without knowledge (score 2) from 21% to 80%. The predicted risk of ED was from 6% to 69% for score 1 and from 7% to 63% for score 2. The predictive power of the risk scores was confirmed in the independent patient cohort (CR score 1, from 10% to 91%; CR score 2, from 16% to 80%; ED score 1, from 6% to 69%; and ED score 2, from 7% to 61%).

INTERPRETATION

The scores for acute myeloid leukaemia can be used to predict the probability of CR and the risk of ED in older patients with acute myeloid leukaemia, but otherwise medically healthy, for whom intensive induction chemotherapy is planned. This information can help physicians with difficult decisions for treatment of these patients.

FUNDING

Deutsche Krebshilfe and Deutsche Forschungsgemeinschaft.

The role of microRNAs in acute myeloid leukemia

MicroRNAs (miRs) are short (18-22 nucleotides) non-coding RNAs that are important in regulating gene expression. MiR expression is deregulated in many types of cancers, including leukemias. In acute myeloid leukemia (AML), the expression of specific miRs has been linked with both prognostically and cytogenetically defined subgroups. Recent studies have shown that deregulation of miR expression is not simply a consequence of AML but a potential contributer to leukemogenesis. This commentary will focus on select findings that describe the different mechanistic roles for miRs in the development of leukemia.

The prognostic and functional role of microRNAs in acute myeloid leukemia

Expression of microRNAs, a new class of noncoding RNAs that hybridize to target messenger RNA and regulate their translation into proteins, has been recently demonstrated to be altered in acute myeloid leukemia (AML). Distinctive patterns of increased expression and/or silencing of multiple microRNAs (microRNA signatures) have been associated with specific cytogenetic and molecular subsets of AML. Changes in the expression of several microRNAs altered in AML have been shown to have functional relevance in leukemogenesis, with some microRNAs acting as oncogenes and others as tumor suppressors. Both microRNA signatures and a single microRNA (ie, miR-181a) have been shown to supply prognostic information complementing that gained from cytogenetics, gene mutations, and altered gene expression. Moreover, it has been demonstrated experimentally that antileukemic effects can be achieved by modulating microRNA expression by pharmacologic agents and/or increasing low endogenous levels of microRNAs with tumor suppressor function by synthetic microRNA oligonucleotides, or down-regulating high endogenous levels of leukemogenic microRNAs by antisense oligonucleotides (antagomirs). Therefore, it is reasonable to predict the development of novel microRNA-based therapeutic approaches in AML. We review herein results of current studies analyzing changes of microRNA expression in AML and discuss their potential biologic, diagnostic, and prognostic relevance.