Clinical relevance of mutations and gene-expression changes in adult acute myeloid leukemia with normal cytogenetics: are we ready for a prognostically prioritized molecular classification?

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.

Single nucleotide polymorphism of Wilms' tumor 1 gene rs16754 in Korean patients with cytogenetically normal acute myeloid leukemia

A recent study from Germany showed that WT1 single nucleotide polymorphism (SNP) rs16754 was an independent prognostic factor in cytogenetically normal acute myeloid leukemia (CN-AML). We analyzed clinical impact of the WT1 rs16754 genotype on disease characteristics and outcomes in Korean patients with CN-AML. A total of 73 patients with CN-AML were included in the study. All patients received standard induction chemotherapy and their bone marrow or peripheral blood samples were cryopreserved at the time of diagnosis. WT1 exons 7 and 9 were amplified using polymerase chain reaction and directly sequenced. The genotype frequency for WT1 rs16754 was 6.8% for AA, 39.7% for GA, and 53.4% for GG. G was a minor allele in German population, whereas it was a major allele in Korean (13.7% vs. 73.3%, P < 0.001). Complete remission was induced in 85.3% of patients with GA/AA and 84.6% of those with GG (P = 0.936). Survival rates were also similar between patients with GG and those with GA/AA. Asian and Western populations exhibited significant differences in allele and genotype frequencies of WT1 rs16754. In Korean patients with CN-AML, WT1 SNP rs16754 had no significant impact on clinical outcomes and further investigations are needed to define prognostic implication of WT1 SNP rs16754 in CN-AML.

Chemosensitivity of nonleukemic clonogenic precursors in AML patients in complete remission: association with CD34(+) mobilization and with disease-free survival

A high number of CD34(+) cells in the peripheral blood during mobilization in patients with acute myeloid leukemia (AML) in complete remission (CR) is associated with a high relapse rate. The variability in chemoresistance of normal bone marrow precursors has been hypothesized as explanation for the variable CD34 mobilization in AML. In 37 patients with AML in CR, we determined the chemosensitivity of bone marrow clonogenic precursors to maphosphamide and etoposide, which was then correlated with the degree of CD34(+) mobilization. In an enlarged set of 49 patients, we also studied the importance of chemosensitivity of marrow precursors for disease-free survival and relapse incidence. Significant correlations were demonstrated between the peak number of CD34(+) cells and residual growth of colony-forming unit granulocyte-macrophage (CFU-GM) after maphosphamide (R = 0.550; p = 0.0003) and after etoposide (R = 0.793; p = 0.0003). It was possible to identify three groups of AML patients based on chemosensitivity. The mean CD34(+) peak was 33 × 10(6)/L in the hyperchemosensitive group, 141 × 10(6)/L in the normochemosensitive (p = 0.03), and 379 × 10(6)/L in the chemoresistant group (p = 0.002). Failed CD34(+) mobilization was observed in 72% of the hyperchemosensitive group, 23% of the normochemosensitive group, and 0% of the chemoresistant group (p = 0.001). Hyperchemosensitivity of CFU-GM, together with a low platelet count, were independent factors important in the failure of CD34(+) cell mobilization. A disease-free survival significantly inferior to that of all other patients was associated with chemoresistance of CFU-GM (log rank, p = 0.030) and with chemoresistance of burst-forming unit erythroid (BFU-E) (log rank, p = 0.033). Chemoresistance of CFU-GM (p = 0.048) and BFU-E (p = 0.017) was also associated with increase relapse incidence. Nonleukemic nature of these precursors was demonstrated studying minimal residual disease from single colony cells. In conclusion, we found that hyperchemosensitivity of normal nonleukemic CFU-GM is associated with a high risk of CD34(+) cell mobilization failure, while a chemoresistant pattern in CFU-GM and BFU-E is associated with poor disease-free survival and increased cumulative incidence of relapse.

Stem cell gene expression programs influence clinical outcome in human leukemia

Xenograft studies indicate that some solid tumors and leukemias are organized as cellular hierarchies sustained by cancer stem cells (CSCs). Despite the promise of the CSC model, its relevance in humans remains uncertain. Here we show that acute myeloid leukemia (AML) follows a CSC model on the basis of sorting multiple populations from each of 16 primary human AML samples and identifying which contain leukemia stem cells (LSCs) using a sensitive xenograft assay. Analysis of gene expression from all functionally validated populations yielded an LSC-specific signature. Similarly, a hematopoietic stem cell (HSC) gene signature was established. Bioinformatic analysis identified a core transcriptional program shared by LSCs and HSCs, revealing the molecular machinery underlying 'stemness' properties. Both stem cell programs were highly significant independent predictors of patient survival and were found in existing prognostic signatures. Thus, determinants of stemness influence the clinical outcome of AML, establishing that LSCs are clinically relevant and not artifacts of xenotransplantation.

NPM1 mutation is a stable marker for minimal residual disease monitoring in acute myeloid leukaemia patients with increased sensitivity compared to WT1 expression

Mutation in the NPM1 gene occurs in 60% of acute myeloid leukaemia (AML) patients with normal karyotype. NPM1 mutation is potentially a superior minimal residual disease (MRD) marker compared to WT1 gene overexpression by being specific to the malignant clone, although experimental evidence published so far includes very limited numbers of relapsed cases. Also, the stability of the NPM1 mutation has been questioned by reports of the mutation being lost at relapse. In the present study we compared NPM1 mutation and WT1 overexpression as MRD markers in 20 cases of relapsed AML. The 20 patients experienced a total of 28 morphological relapses. Karyotypic evolution was detected in 56% of relapses. All relapses were accompanied by high levels of NPM1 mutation, along with high WT1 mRNA levels, thus demonstrating complete stability of both markers during relapse. Detectable NPM1 mutation following a period of morphological remission was accompanied by a morphological relapse in all cases. In contrast, WT1 expression was detected in 33% of the NPM1 mutation negative samples. This background WT1 expression produced by non-leukaemia cells was highly variable, both between and within patients, and limited the de facto sensitivity of the WT1 expression analysis. The present study therefore provides important experimental evidence demonstrating that NPM1 mutation is superior to WT1 overexpression as marker of MRD in NPM1-mutated AML, even in the presence of extensive karyotypic evolution.

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.

Immunophenotype distinction between acute promyelocytic leukaemia and CD15- CD34- HLA-DR- acute myeloid leukaemia with nucleophosmin mutations

Acute promyelocytic leukaemia (APL) is a unique clinicobiologic entity that can be successfully treated with All-trans Retinoic Acid ATRA-based regimens. Some cases of acute myeloid leukaemia (AML) with nucleophosmin (NPM) mutations have an immunophenotype that is similar to APL. The objective of the study is to compare antigenic expression in a group of APL patients with that in AML patients with NPM mutations and an APL-like immunophenotype (CD15- CD34- HLA-DR-). A consecutive series of 40 APL and 12 NPM patients with an APL-like phenotype were included in the study. Immunophenotypic patterns were investigated by multiparametric flow cytometry. Promyelocytic leukaemia-retinoic acid receptor-α transcript type, NPM and FLT3 mutations were investigated using conventional methods. Statistically significant differences were found between APL and NPM-mutated AML in CD33, CD13, CD2 and CD110 reactivity. CD2 expression was absent in every patient with NPM-mutated AML. In addition, mean fluorescence intensity and the coefficient of variation (cv) of CD33 and CD13 showed statistical differences between the two groups for CD33 (p = 0.007) and a trend to significance for CD13 (p = 0.05). Furthermore, among 45 evaluable patients, CD110 expression statistically differentiates between the two groups: [2/33 (6%) in the APL group and 8/12 (66.6%) in the NPM-mutated AML (p = 0.014)]. However, these traits were subtle, raising the possibility of practical diagnostic challenges. In conclusion, CD110 and CD33 reactivity may be useful to distinguish APL from NPM-mutated AML with CD15, CD34 and HLA-DR negativity. Nevertheless, cytogenetic and molecular characterization is necessary to establish the accurate diagnosis of AML.

miR-10a overexpression is associated with NPM1 mutations and MDM4 downregulation in intermediate-risk acute myeloid leukemia

OBJECTIVE

The study investigated differential microRNA (miRNA) expression patterns in acute myeloid leukemia (AML) patients with intermediate-risk (IR) characteristics. After characterization and validation of miR-10a, which was specifically upregulated in nucleophosmin 1 (NPM1) mutant AML samples, functional consequences of miR-10a overexpression were further delineated in vitro.

MATERIALS AND METHODS

Microarray analysis of miRNAs in bone marrow samples from AML (IR) patients with NPM1 mutations and healthy donors was performed to detect differential expression patterns. After validation of miRNA expression specific for NPM1 mutation in AML patients by quantitative reverse transcription polymerase chain reaction, a functional target gene search was conducted using complementary DNA microarray data from samples transfected with miR-10a. Potential target gene validation was done using transient transfection of K562 cells followed by Western blotting and luciferase reporter assay.

RESULTS

In comparison with wild-type samples, NPM1 mutant AML samples were shown to markedly overexpress miR-10a. Subsequent in vitro miR-10a overexpression induced differential gene expression as determined by microarray analysis. Here the murine double minute 4 (MDM4) gene turned out as a candidate gene for miR-10a. Validation of MDM4 in leukemic cells revealed a robust negative relationship between miR-10a overexpression and MDM4 downregulation. Furthermore, we determined an inverse association between miR-10a and MDM4 expression in AML (IR) samples with respect to their NPM1 mutational status.

CONCLUSIONS

miR-10a expression is highly characteristic for AML (IR) patients with NPM1 mutations and may influence its biological properties in AML by interfering with the p53 machinery partly regulated by MDM4.

Tipifarnib in the treatment of newly diagnosed acute myelogenous leukemia

Farnesyltransferase inhibitors (FTIs) represent a new class of signal transduction inhibitors that block the processing of cellular polypeptides that have cysteine terminal residues and, by so doing, interdict multiple pathways involved in proliferation and survival of diverse malignant cell types. Tipifarnib is an orally bioavailable, nonpeptidomimetic methylquinolone FTI that has exhibited clinical activity in patients with myeloid malignancies including elderly adults with acute myelogenous leukemia (AML) who are not candidates for traditional cytotoxic chemotherapy, patients with high-risk myelodysplasia, myeloproliferative disorders, and imatinib-resistant chronic myelogenous leukemia. Because of its relatively low toxicity profile, tipifarnib provides an important alternative to traditional cytotoxic approaches for elderly patients who are not likely to tolerate or even benefit from aggressive chemotherapy. In this review, we will focus on the clinical development of tipifarnib for treatment of newly diagnosed AML, both as induction therapy for elderly adults with poor-risk AML and as maintenance therapy following achievement of first complete remission following induction and consolidation therapies for poor-risk AML. As with all other malignancies, the optimal approach is likely to lie in rational combinations of tipifarnib with cytotoxic, biologic and/or immunomodulatory agents with non-cross-resistant mechanisms of action. Gene expression profiling has identified networks of differentially expressed genes and gene combinations capable of predicting response to single agent tipifarnib. The clinical and correlative laboratory trials in progress and under development will provide the critical foundations for defining the optimal roles of tipifarnib and in patients with AMl and other hematologic malignancies.

Epigenetic regulation of cellular adhesion in cancer

Epigenetics describes the development and maintenance of stable heritable gene expression patterns, which allow cells to show different phenotypes despite of a commonly shared genetic code. The increasing knowledge in this field during the last decades reveals its importance for many physiological processes like differentiation, embryogenesis and parental imprinting, but also for some diseases such as cancer. Recent data have shown that the complexity of carcinogenesis can no longer be explained solely on the basis of genetic changes, but epigenomic alterations such as changes of the DNA methylation pattern and/or post-translational histone modifications and changes of microRNA expression need to be equally considered. Such epigenetic alterations may cause permanent changes in gene expression patterns and may therefore essentially contribute to some of the known phenotypic characteristics of cancer cells like the loss of growth control, altered intercellular communication and enhanced motility. The two latter may essentially be associated with the downregulation of cellular adhesion molecules, which may therefore be relevant in the context of cancer invasiveness and prognosis. The targeted modification of the epigenome may therefore open new horizons within the increasingly important field of epigenetic therapeutics-particularly in view of the regulation of cellular adhesion with particular attention to tumor cell invasion and metastasis.

Prognostically important molecular markers in cytogenetically normal acute myeloid leukemia

Cytogenetically normal acute myeloid leukemia (CN-AML) is a heterogeneous disease with variable clinical outcomes. Emerging data has identified molecular markers that provide additional prognostic information to better classify these patients into those with a more favorable prognosis and those with an unfavorable prognosis who may require more aggressive or investigational therapies. Markers such as mutations in nucleophosmin 1 gene and CCAAT/enhancer binding protein alpha gene have been associated with a more favorable prognosis in CN-AML. In contrast, FMS-related tyrosine kinase 3 mutations, partial tandem duplication of mixed-lineage leukemia gene and overexpression of brain and acute leukemia, cytoplasmic gene are associated with inferior clinical outcomes. In this article, the authors discuss the classical clinical features of AML and the importance of cytogenetics that predict prognosis in AML. They review the best-described molecular markers in CN-AML and their significance to clinical decision making in CN-AML.

A comparative analysis of molecular genetic and conventional cytogenetic detection of diagnostically important translocations in more than 400 cases of acute leukemia, highlighting the frequency of false-negative conventional cytogenetics

In this study, we correlated the results of concurrent molecular and cytogenetic detection of entity-defining translocations in adults with acute leukemia to determine the frequency of cryptic translocations missed by conventional cytogenetics (CC) and of recurrent, prognostically relevant translocations not detectable by multiplex reverse transcriptase-polymerase chain reaction (MRP). During a 5.5-year period, 442 diagnostic acute leukemia specimens were submitted for MRP-based detection of 7 common recurrent translocations: t(8;21), t(15;17), inv(16), t(9;22), t(12;21), t(4;11), and t(1;19), with a detection rate of 15.2% (67/442). CC was performed in 330 (74.7%) of 442 cases. In 7 of these 330 cases, CC missed the translocation detected by MRP. In 50 additional cases, CC revealed 1 of the MRP-detectable translocations (all were also MRP positive), yielding a false-negative rate of 12% (7/57) for the CC assay. The remaining 140 of 190 cases with clonal cytogenetic changes harbored abnormalities that were not targeted by the MRP assay, including 8 that define specific acute myeloid leukemia entities. This study revealed the frequent occurrence of false-negative, entity-defining CC analysis and highlighted the complementary nature of MRP and CC approaches in detecting genetic abnormalities in acute leukemia.

Prospective separation of normal and leukemic stem cells based on differential expression of TIM3, a human acute myeloid leukemia stem cell marker

Hematopoietic tissues in acute myeloid leukemia (AML) patients contain both leukemia stem cells (LSC) and residual normal hematopoietic stem cells (HSC). The ability to prospectively separate residual HSC from LSC would enable important scientific and clinical investigation including the possibility of purged autologous hematopoietic cell transplants. We report here the identification of TIM3 as an AML stem cell surface marker more highly expressed on multiple specimens of AML LSC than on normal bone marrow HSC. TIM3 expression was detected in all cytogenetic subgroups of AML, but was significantly higher in AML-associated with core binding factor translocations or mutations in CEBPA. By assessing engraftment in NOD/SCID/IL2Rγ-null mice, we determined that HSC function resides predominantly in the TIM3-negative fraction of normal bone marrow, whereas LSC function from multiple AML specimens resides predominantly in the TIM3-positive compartment. Significantly, differential TIM3 expression enabled the prospective separation of HSC from LSC in the majority of AML specimens with detectable residual HSC function.

Identification of recurring tumor-specific somatic mutations in acute myeloid leukemia by transcriptome sequencing

Genetic lesions are crucial for cancer initiation. Recently, whole genome sequencing, using next generation technology, was used as a systematic approach to identify mutations in genomes of various types of tumors including melanoma, lung and breast cancer, as well as acute myeloid leukemia (AML). Here, we identify tumor-specific somatic mutations by sequencing transcriptionally active genes. Mutations were detected by comparing the transcriptome sequence of an AML sample with the corresponding remission sample. Using this approach, we found five non-synonymous mutations specific to the tumor sample. They include a nonsense mutation affecting the RUNX1 gene, which is a known mutational target in AML, and a missense mutation in the putative tumor suppressor gene TLE4, which encodes a RUNX1 interacting protein. Another missense mutation was identified in SHKBP1, which acts downstream of FLT3, a receptor tyrosine kinase mutated in about 30% of AML cases. The frequency of mutations in TLE4 and SHKBP1 in 95 cytogenetically normal AML patients was 2%. Our study demonstrates that whole transcriptome sequencing leads to the rapid detection of recurring point mutations in the coding regions of genes relevant to malignant transformation.

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.

RUNX1 mutations in acute myeloid leukemia: results from a comprehensive genetic and clinical analysis from the AML study group

PURPOSE

To evaluate frequency, biologic features, and clinical relevance of RUNX1 mutations in acute myeloid leukemia (AML).

PATIENTS AND METHODS

Diagnostic samples from 945 patients (age 18 to 60 years) were analyzed for RUNX1 mutations. In a subset of cases (n = 269), microarray gene expression analysis was performed.

RESULTS

Fifty-nine RUNX1 mutations were identified in 53 (5.6%) of 945 cases, predominantly in exons 3 (n = 11), 4 (n = 10), and 8 (n = 23). RUNX1 mutations clustered in the intermediate-risk cytogenetic group (46 of 640, 7.2%; cytogenetically normal, 34 of 538, 6.3%), whereas they were less frequent in adverse-risk cytogenetics (five of 109, 4.6%) and absent in core-binding-factor AML (0 of 77) and acute promyelocytic leukemia (0 of 61). RUNX1 mutations were associated with MLL-partial tandem duplications (P = .0007) and IDH1/IDH2 mutations (P = .03), inversely correlated with NPM1 (P < .0001), and in trend with CEBPA (P = .10) mutations. RUNX1 mutations were characterized by a distinct gene expression pattern; this RUNX1 mutation-derived signature was not exclusive for the mutation, but also included mostly adverse-risk AML [eg, 7q-, -7, inv(3), or t(3;3)]. RUNX1 mutations predicted for resistance to chemotherapy (rates of refractory disease 30% and 19%, P = .047, for RUNX1-mutated and wild-type patients, respectively), as well as inferior event-free survival (EFS; P < .0001), relapse-free survival (RFS, P = .022), and overall survival (P = .051). In multivariable analysis, RUNX1 mutations were an independent prognostic marker for shorter EFS (P = .007). Explorative subgroup analysis revealed that allogeneic hematopoietic stem-cell transplantation had a favorable impact on RFS in RUNX1-mutated patients (P < .0001).

CONCLUSION

AML with RUNX1 mutations are characterized by distinct genetic properties and are associated with resistance to therapy and inferior outcome.

Immunophenotypic features of acute myeloid leukaemia patients exhibiting high FLT3 expression not associated with mutations

FMS-related tyrosine kinase 3 (FLT3) mutations are found in 30% of cases of acute myeloid leukaemia (AML). In addition, recent studies have lead to the identification of about 10-15% of AML patients displaying high expression of FLT3, not associated with mutations of the receptor (FLT3 Wild-type High, FLT3WTH). These AMLs, as well as those displaying internal tandem duplication (ITD) are associated with an unfavourable prognosis. However, the biological features of these AMLs are poorly characterized. The present study explored the immunophenotypic features of FLT3WTH AMLs in 94 de novo cases of AML. The levels of FLT3 expression, as assessed by flow cytometry and FLT3 mutational status, was used to identify four AML subgroups: FLT3WTH (14/94); FLT3 Wild-type low (FLT3WTL, 48/94); FLT3 internal tandem duplication (FLT3ITD 26/94); FLT3 aspartic acid 835 (FLT3D835, 6/94). FLT3WTH and FLT3ITD were characterized by: high white blast cell counts; predominance of M4 and M5 French-American-British classification subtypes and associated expression of myelo-monocytic markers; high expression of CD123 and TRAIL-Rs; high expression of receptors for angiogenic growth factors. Addition of FLT3 Ligand to human CD34(+) or monocytic cells stimulated CD123 and TRAIL-R expression. These findings are of potential value for the development of new therapeutic strategies.

Monitoring of minimal residual disease in patients with core binding factor acute myeloid leukemia and the impact of C-KIT, FLT3, and JAK2 mutations on clinical outcome

Mutational analysis of C-KIT, fms-like tyrosine kinase 3 (FLT3), and JAK2 genes was performed in 60 patients with core binding factor acute myeloid leukemia (CBF-AML). Patients reaching molecular remission had lower incidence of relapse and better overall survival (OS) than those not achieving molecular remission (p = 0.008 and 0.044, respectively). The overall incidence of C-KIT mutations was 33.3%, FLT3/internal tandem duplication (ITD) 6.6%, FLT3(D835) 10.0% and JAK2(V617F) mutations 3.3%. C-KIT mutations did not predict for clinical/molecular relapse (p = 0.33). OS of patients with C-KIT mutations was identical to patients without them when all patients with CBF-AML were analyzed together (p = 0.58). When AML1/ETO-positive patients were evaluated separately, OS in C-KIT-mutated patients was slightly inferior to unmutated ones (p = 0.14). Patients with CBF-AML with a mutated C-KIT gene were also more prone to extramedullary disease (p = 0.08). Of six patients harboring various FLT3(D835) mutations, four (66.7%) relapsed, whereas among 43 cases without these mutations, 16 relapses (37%) were observed (p = 0.08). Our results on minimal residual disease, C-KIT, and FLT3/ITDs are in line with previous studies. Surprisingly, a possible role for FLT3(D835) mutations was noted in addition. These results need validation in even larger patient cohorts than ours. For routine clinical practice, it may be meaningful to screen for C-KIT mutations in AML1/ETO-positive patients, as well as for FLT3(D835) mutations in CBF-AML.

FLT3 inhibitors in the treatment of acute myeloid leukemia: the start of an era?

Despite recent modest improvements in the chemotherapy regimens used to treat acute myeloid leukemia (AML), many patients diagnosed with AML ultimately die of the disease. Commonly occurring genetic alterations have been identified that strongly affect the prognosis for patients with AML. These alterations represent possible targets for investigational therapies that could act to specifically halt the aberrant growth of AML cells while limiting damage to normal cells. One such gene is the Fms-like tyrosine kinase 3 (FLT3) gene, which is mutated in approximately 30% of adult patients with AML and has a significant impact on prognosis. In particular, internal tandem duplications in FLT3 confer a poor prognosis to this large subgroup of patients with AML. Agents that target FLT3 are in development for the treatment of patients who have AML and offer a potential paradigm change in the current standard treatment of AML. For this report, the authors reviewed the prognostic significance of genetic alterations observed in AML with a focus on the therapeutic implications of targeting FLT3. The introduction of such agents may be the next major step toward the era of personalized therapy in AML.

Prognostic factors in pediatric acute myeloid leukemia

Acute myeloid leukemia (AML), a heterogeneous group of diseases with variable responses to the same therapy, comprises nearly a quarter of childhood acute leukemias. Although historically very few prognostic markers have been incorporated into therapeutic decision making in AML, recent advances in technology have enabled identification of numerous factors associated with disease outcome. This review provides a detailed analysis of most clinically relevant factors associated with disease outcome in childhood AML.

Molecular genetics of adult acute myeloid leukemia: prognostic and therapeutic implications

Molecular analyses of leukemic blasts from patients with acute myeloid leukemia (AML) have revealed a striking heterogeneity with regard to the presence of acquired gene mutations and changes in gene and microRNA expression. Multiple submicroscopic genetic alterations with prognostic significance have been discovered. Application of gene- and microRNA profiling has identified genome-wide expression signatures that separate cytogenetic and molecular subsets of patients with AML into previously unrecognized biologic and/or prognostic subgroups. These and similar future findings are likely to have a major impact on the clinical management of AML because many of the identified genetic alterations not only represent independent prognosticators, but also may constitute targets for specific therapeutic intervention. In this report, we review genetic findings in AML and discuss their clinical implications.

Acute myeloid leukemia with IDH1 or IDH2 mutation: frequency and clinicopathologic features

Mutations in the isocitrate dehydrogenase 1 (IDH1) and IDH2 genes are reported in acute myeloid leukemia (AML). We studied the frequency and the clinicopathologic features of IDH1 and IDH2 mutations in AML. Mutations in IDH1 (IDH1(R)¹³²) and IDH2 (IDH2(R)¹⁷²) were assessed by Sanger sequencing in 199 AML cases. Point mutations in IDH1(R)¹³² were detected in 12 (6.0%) of 199 cases and in IDH2(R)¹⁷² in 4 (2.0%) of 196 cases. Of the 16 mutated cases, 15 (94%) were cytogenetically normal, for an overall frequency in this group of 11.8%. IDH1(R)¹³² and IDH2(R)¹⁷² mutations were mutually exclusive. Concurrent mutations in NPM1, FLT3, CEBPA, and NRAS were detected only in AML with the IDH1(R)¹³² mutation. The clinical and laboratory variables of patients with AML with IDH mutations showed no significant differences compared with patients with wild-type IDH. We conclude that IDH1(R)¹³² and IDH2(R)¹⁷² mutations occur most often in cytogenetically normal AML cases with an overall frequency of approximately 11.8%.

Association of a leukemic stem cell gene expression signature with clinical outcomes in acute myeloid leukemia

CONTEXT

In many cancers, specific subpopulations of cells appear to be uniquely capable of initiating and maintaining tumors. The strongest support for this cancer stem cell model comes from transplantation assays in immunodeficient mice, which indicate that human acute myeloid leukemia (AML) is driven by self-renewing leukemic stem cells (LSCs). This model has significant implications for the development of novel therapies, but its clinical relevance has yet to be determined.

OBJECTIVE

To identify an LSC gene expression signature and test its association with clinical outcomes in AML.

DESIGN, SETTING, AND PATIENTS

Retrospective study of global gene expression (microarray) profiles of LSC-enriched subpopulations from primary AML and normal patient samples, which were obtained at a US medical center between April 2005 and July 2007, and validation data sets of global transcriptional profiles of AML tumors from 4 independent cohorts (n = 1047).

MAIN OUTCOME MEASURES

Identification of genes discriminating LSC-enriched populations from other subpopulations in AML tumors; and association of LSC-specific genes with overall, event-free, and relapse-free survival and with therapeutic response.

RESULTS

Expression levels of 52 genes distinguished LSC-enriched populations from other subpopulations in cell-sorted AML samples. An LSC score summarizing expression of these genes in bulk primary AML tumor samples was associated with clinical outcomes in the 4 independent patient cohorts. High LSC scores were associated with worse overall, event-free, and relapse-free survival among patients with either normal karyotypes or chromosomal abnormalities. For the largest cohort of patients with normal karyotypes (n = 163), the LSC score was significantly associated with overall survival as a continuous variable (hazard ratio [HR], 1.15; 95% confidence interval [CI], 1.08-1.22; log-likelihood P <.001). The absolute risk of death by 3 years was 57% (95% CI, 43%-67%) for the low LSC score group compared with 78% (95% CI, 66%-86%) for the high LSC score group (HR, 1.9 [95% CI, 1.3-2.7]; log-rank P = .002). In another cohort with available data on event-free survival for 70 patients with normal karyotypes, the risk of an event by 3 years was 48% (95% CI, 27%-63%) in the low LSC score group vs 81% (95% CI, 60%-91%) in the high LSC score group (HR, 2.4 [95% CI, 1.3-4.5]; log-rank P = .006). In multivariate Cox regression including age, mutations in FLT3 and NPM1, and cytogenetic abnormalities, the HRs for LSC score in the 3 cohorts with data on all variables were 1.07 (95% CI, 1.01-1.13; P = .02), 1.10 (95% CI, 1.03-1.17; P = .005), and 1.17 (95% CI, 1.05-1.30; P = .005).

CONCLUSION

High expression of an LSC gene signature is independently associated with adverse outcomes in patients with AML.

Hypoxia-inducible factor-1α protein expression is associated with poor survival in normal karyotype adult acute myeloid leukemia

We examined the predictive impact of HIF-1α protein expression on clinical outcome of 84 normal karyotype acute myeloid leukemia (NK-AML) patients (median age 66.5 years) at our institute. Thirty percent of NK-AML cells expressed cytoplasmic HIF-1α. In univariate analysis, low HIF-1α (≤ 5%, n = 66) was associated with improved event-free survival (p = 0.0453, HR = 0.22). Multivariate analysis incorporating age, complete remission, FLT3-ITD mutation, and marrow blast percentage demonstrated that HIF-1α was independently associated with poorer overall and event-free survival. HIF-1α expression correlated with VEGF-C but not VEGF-A, marrow angiogenesis, FLT3 ITD or NPM1 mutations. These results support HIF-1α as an outcome marker for NK-AML.

Allogeneic hematopoietic cell transplantation for adults with acute myeloid leukemia: myths, controversies, and unknowns

Progress in the last decade has improved the understanding of leukemia biology. Molecular markers in combinations with cytogenetics have improved the risk stratification of acute myeloid leukemia (AML) and informed decision-making. In parallel, several important advances in the transplant field, such as better supportive care, improved transplant technology, increased availability of alternative donors, and reduced-intensity conditioning have improved the safety as well as access of allogeneic hematopoietic cell transplantation (HCT) for a larger number of patients. In this review, the positioning of HCT in the management of patients with AML is evaluated in view of changing risk/benefit ratios associated with both conventional treatments and transplantation, and some of the controversies are addressed in light of emerging data. Increasing data demonstrate outcomes of alternative donor transplantation approaching HLA-identical sibling donors in high-risk AML supporting the inclusion of alternative donors in trials of prospective studies evaluating post remission strategies for high-risk AML. The use of reduced-intensity conditioning has expanded the eligibility of HCT to older patients with AML, and outcome data are encouraging. Continued study of HCT versus alternative therapies is required to optimize patients' outcomes in AML.

Prognostic significance of expression of a single microRNA, miR-181a, in cytogenetically normal acute myeloid leukemia: a Cancer and Leukemia Group B study

PURPOSE

To evaluate the prognostic significance of expression levels of a single microRNA, miR-181a, in the context of established molecular markers in cytogenetically normal acute myeloid leukemia (CN-AML), and to gain insight into the leukemogenic role of miR-181a.

PATIENTS AND METHODS

miR-181a expression was measured in pretreatment marrow using Ohio State University Comprehensive Cancer Center version 3.0 arrays in 187 younger (<60 years) adults with CN-AML. Presence of other molecular prognosticators was assessed centrally. A gene-expression profile associated with miR-181a expression was derived using microarrays and evaluated by Gene-Ontology analysis.

RESULTS

Higher miR-181a expression associated with a higher complete remission (CR) rate (P=.04), longer overall survival (OS; P=.01) and a trend for longer disease-free survival (DFS; P=.09). The impact of miR-181a was most striking in poor molecular risk patients with FLT3-internal tandem duplication (FLT3-ITD) and/or NPM1 wild-type, where higher miR-181a expression associated with a higher CR rate (P=.009), and longer DFS (P<.001) and OS (P<.001). In multivariable analyses, higher miR-181a expression was significantly associated with better outcome, both in the whole patient cohort and in patients with FLT3-ITD and/or NPM1 wild-type. These results were also validated in an independent set of older (≥60 years) patients with CN-AML. A miR-181a-associated gene-expression profile was characterized by enrichment of genes usually involved in innate immunity.

CONCLUSION

To our knowledge, we provide the first evidence that the expression of a single microRNA, miR-181a, is associated with clinical outcome of patients with CN-AML and may refine their molecular risk classification. Targeted treatments that increase endogenous levels of miR-181a might represent novel therapeutic strategies.

Abnormal methylation of GRAF promoter Chinese patients with acute myeloid leukemia

The epigenetic disturbances are recognized as an alternative mechanism contributing to the pathogenesis of acute myeloid leukemia (AML). GTPase regulator associated with focal adhesion kinase (GRAF), a putative tumor suppressor gene, was revealed with mutations and promoter methylation in AML and myelodysplastic syndrome. In this study, we investigated the methylation status of GRAF promoter in Chinese AML patients. Aberrant methylation of GRAF promoter was detected in 66.7% (88/132) of the cases analyzed. The methylation of GRAF gene could be detected in all FAB subtypes and in all cytogenetic risk groups. There were no significant differences in clinical features, FAB subtypes and cytogenetic risk groups between patients with and without GRAF methylation. GRAF transcript was significantly lower in AML group compared to controls (3.30 vs 56.06, P<0.001). Both patients with methylated GRAF gene and those without methylated GRAF gene had significantly lower GRAF transcript than controls (P<0.001). Furthermore, GRAF transcript was significantly lower in patients with methylated GRAF than those without methylated GRAF (1.64 vs 6.42, P=0.005). These findings suggest that the hypermethylation of GRAF promoter might be one of early events in the development of AML.

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.

BAALC and ERG expression levels are associated with outcome and distinct gene and microRNA expression profiles in older patients with de novo cytogenetically normal acute myeloid leukemia: a Cancer and Leukemia Group B study

BAALC and ERG expression levels are prognostic markers in younger (< 60 years) cytogenetically normal acute myeloid leukemia (CN-AML) adults; their prognostic impact in older (≥ 60 years) patients requires further investigation. We evaluated pretreatment expression of BAALC and ERG in 158 de novo patients treated on cytarabine/daunorubicin-based protocols. The patients were also characterized for other established molecular prognosticators. Low BAALC and ERG expression levels were associated with better outcome in univariable and multivariable analyses. Expression levels of both BAALC and ERG were the only factors significantly associated with overall survival upon multivariable analysis. To gain biological insights, we derived gene expression signatures associated with BAALC and ERG expression in older CN-AML patients. Furthermore, we derived the first microRNA expression signatures associated with the expression of these 2 genes. In low BAALC expressers, genes associated with undifferentiated hematopoietic precursors and unfavorable outcome predictors were down-regulated, whereas HOX genes and HOX-gene-embedded microRNAs were up-regulated. Low ERG expressers presented with down-regulation of genes involved in the DNA-methylation machinery, and up-regulation of miR-148a, which targets DNMT3B. We conclude that in older CN-AML patients, low BAALC and ERG expression associates with better outcome and distinct gene and microRNA expression signatures that could aid in identifying new targets and novel therapeutic strategies for older patients.

The role of molecular tests in acute myelogenous leukemia treatment decisions

The prognosis for patients with acute myelogenous leukemia (AML) is dependent on age, karyotype, and the genetics of the neoplastic cell. The molecular markers with prognostic impact include mutations in FLT3, NPM1, MLL, WT1, c-KIT, and expression levels of BAALC, NM1, ERG, and CXCR4. Gene expression profiles and microRNA expression patterns in AML may prove highly useful in defining the prognosis of AML. Cytogenetic and, increasingly, molecular findings are used in determining the best therapy for AML patients, especially the choice of whether to perform allogeneic stem cell transplantation.

MicroRNA expression in acute myeloid leukemia

Acute myeloid leukemia (AML) is a group of diseases that are very heterogeneous with regard to cytogenetic aberrations, gene mutations, and changes in expression of numerous genes. A new class of genes known as microRNAs recently was found to be involved in myeloid leukemogenesis. These genes are transcribed into regulatory, noncoding RNAs that control mRNA and protein expression of target genes. Genome-wide analyses of microRNA expression have revealed signatures associated with selected cytogenetic and molecular subsets of AML and have led to the recognition of previously unreported molecular pathways involved in myeloid leukemogenesis. In cytogenetically normal AML, microRNA-expression profiling has also provided prognostic information in addition to that obtained from cytogenetics and analyses of gene mutations and aberrant gene expression. This article reviews recent studies that were focused on the alterations of microRNA expression in AML and their diagnostic and prognostic significance.

Advances in the management of acute myeloid leukemia in older adult patients

PURPOSE/OBJECTIVES

To update oncology nurses on new developments in the care of older adult patients with acute myeloid leukemia (AML).

DATA SOURCES

Clinical trial data, published guidelines, review articles, and conference proceedings.

DATA SYNTHESIS

Therapies for older adult patients with AML include cytarabine-based intensive-induction chemotherapy, investigational therapy, and supportive care. Nonmyeloablative allogeneic hematopoietic stem cell transplantation may provide the best opportunity for cure following remission if a human leukocyte antigen-matched hematopoietic stem cell donor is available. Careful assessment of patient- and disease-related factors is critical in determining the appropriate treatment modality for individuals. Assessment tools and algorithms may identify patients likely to be intolerant of intensive therapies. Supportive care may improve treatment tolerance and quality of life.

CONCLUSIONS

Survival outcomes have not improved significantly for older adult patients with AML. Novel therapies, coupled with better understanding of prognostic factors, may allow more highly individualized care. Performance status or comorbidity score may provide insights regarding outcome, particularly when combined with age, cytogenetic risk, or molecular markers. Efforts to improve transplantation safety may increase use in the older adult patient population.

IMPLICATIONS FOR NURSING

Nurses provide disease and treatment information, manage adverse effects, and offer emotional support. Knowledge of the key management issues for older adult patients with AML is critical in fulfilling this role.

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

The clinical impact of FLT3-internal tandem duplications (ITDs), an adverse prognostic marker in adults aged < 60 years with primary cytogenetically normal acute myeloid leukemia (CN-AML), requires further investigation in older patients. In CN-AML patients aged ≥ 60 years treated on Cancer and Leukemia Group B frontline trials, we found that FLT3-ITD remained associated with shorter disease-free survival (P < .001; hazard ratio = 2.10) and overall survival (P < .001; hazard ratio = 1.97) in multivariable analyses. This impact on shorter disease-free survival and overall survival was in patients aged 60-69 (P < .001, each) rather than in those aged ≥ 70 years. An FLT3-ITD-associated gene-expression signature revealed overexpression of FLT3, homeobox genes (MEIS1, PBX3, HOXB3), and immunotherapeutic tar-gets (WT1, CD33) and underexpression of leukemia-associated (MLLT3, TAL1) and erythropoiesis-associated (GATA3, EPOR, ANK1, HEMGN) genes. An FLT3-ITD-associated microRNA-expression signature included overexpressed miR-155 and underexpressed miR-144 and miR-451. FLT3-ITD identifies older CN-AML patients with molecular high risk and is associated with gene- and microRNA-expression signatures that provide biologic insights for novel therapeutic approaches.

Recent advances in the diagnosis and classification of myeloid neoplasms--comments on the 2008 WHO classification

The fourth edition of the World Health Organization (WHO) classification of myeloid neoplasms refined the criteria for some previously described myeloid neoplasms and recognized several new entities based on recent elucidation of molecular pathogenesis, identification of new diagnostic and prognostic markers, and progress in clinical management. Protein tyrosine kinase abnormalities, including translocations or mutations involving ABL1, JAK2, MPL, KIT, PDGFRA, PDGFRB, and FGFR1, have been used as the basis for classifying myeloproliferative neoplasms (MPN). Two new entities - refractory cytopenia with unilineage dysplasia and refractory cytopenia of childhood have been added to the group of myelodysplastic syndromes (MDS), and 'refractory anemia with excess blasts-1' has been redefined to emphasize the prognostic significance of increased blasts in the peripheral blood. A list of cytogenetic abnormalities has been introduced as presumptive evidence of MDS in cases with refractory cytopenia but without morphologic evidence of dysplasia. The subgroup 'acute myeloid leukemia (AML) with recurrent genetic abnormalities' has been expanded to include more molecular genetic aberrations. The entity 'AML with multilineage dysplasia' specified in the 2001 WHO classification has been renamed 'AML with myelodysplasia-related changes' to include not only cases with significant multilineage dysplasia but also patients with a history of MDS or myelodysplasia-related cytogenetic abnormalities. The term 'therapy-related myeloid neoplasms' is used to cover the spectrum of disorders previously known as t-AML, t-MDS, or t-MDS/MPN occurring as complications of cytotoxic chemotherapy and/or radiation therapy. In this review, we summarize many of these important changes and discuss some of the diagnostic challenges that remain.

WT1 mutation in 470 adult patients with acute myeloid leukemia: stability during disease evolution and implication of its incorporation into a survival scoring system

The impact of WT1 mutations in acute myeloid leukemia (AML) is not completely settled. We aimed to determine the clinical implication of WT1 mutation in 470 de novo non-M3 AML patients and its stability during the clinical course. WT1 mutations were identified in 6.8% of total patients and 8.3% of younger patients with normal karyotype (CN-AML). The WT1 mutation was closely associated with younger age (P < .001), French-American-British M6 subtype (P = .006), and t(7;11)(p15;p15) (P = .003). Multivariate analysis demonstrated that the WT1 mutation was an independent poor prognostic factor for overall survival and relapse-free survival among total patients and the CN-AML group. A scoring system incorporating WT1 mutation, NPM1/FLT3-ITD, CEBPA mutations, and age into survival analysis proved to be very useful to stratify CN-AML patients into different prognostic groups (P < .001). Sequential analyses were performed on 133 patients. WT1 mutations disappeared at complete remission in all WT1-mutated patients studied. At relapse, 3 of the 16 WT1-mutated patients who had paired samples lost the mutation and 2 acquired additional mutations, whereas 3 of 110 WT1-wild patients acquired novel mutations. In conclusion, WT1 mutations are correlated with poor prognosis in AML patients. The mutation status may be changed in some patients during AML progression.

The cell polarity PTK7 receptor acts as a modulator of the chemotherapeutic response in acute myeloid leukemia and impairs clinical outcome

The pseudo tyrosine kinase receptor 7 (PTK7) is an orphan tyrosine kinase receptor assigned to the planar cell polarity pathway. It plays a major role during embryogenesis and epithelial tissue organization. Here we found that PTK7 is also expressed in normal myeloid progenitors and CD34(+) CD38(-) bone marrow cells in humans. We performed an immunophenotyping screen on more than 300 patients treated for hematologic malignancies. We demonstrated that PTK7 is expressed in acute myeloid leukemia (AML) and is mostly assigned to granulocytic lineage differentiation. Patients with PTK7-positive AML are more resistant to anthracycline-based frontline therapy with a significantly reduced leukemia-free survival in a multivariate analysis model. In vitro, expression of PTK7 in cultured leukemia cells promotes cell migration, cell survival, and resistance to anthracycline-induced apoptosis. The intracellular region of PTK7 is required for these effects. Furthermore, we efficiently sensitized primary AML blasts to anthracycline-mediated cell death using a recombinant soluble PTK7-Fc protein. We conclude that PTK7 is a planar cell polarity component expressed in the myeloid progenitor compartment that conveys promigratory and antiapoptotic signals into the cell and that represents an independent prognosis factor of survival in patients treated with induction chemotherapy.

Cytogenetic and molecular diagnostic characterization combined to postconsolidation minimal residual disease assessment by flow cytometry improves risk stratification in adult acute myeloid leukemia

A total of 143 adult acute myeloid leukemia (AML) patients with available karyotype (K) and FLT3 gene mutational status were assessed for minimal residual disease (MRD) by flow cytometry. Twenty-two (16%) patients had favorable, 115 (80%) intermediate, and 6 (4%) poor risk K; 19 of 129 (15%) carried FLT3-ITD mutation. Considering postconsolidation MRD status, patients with good/intermediate-risk K who were MRD(-) had 4-year relapse-free survival (RFS) of 70% and 63%, and overall survival (OS) of 84% and 67%, respectively. Patients with good- and intermediate-risk K who were MRD(+) had 4-year RFS of 15% and 17%, and OS of 38% and 23%, respectively (P < .001 for all comparisons). FLT3 wild-type patients achieving an MRD(-) status, had a better outcome than those who remained MRD(+) (4-year RFS, 54% vs 17% P < .001; OS, 60% vs 23%, P = .002). Such an approach redefined cytogenetic/genetic categories in 2 groups: (1) low-risk, including good/intermediate K-MRD(-) with 4-year RFS and OS of 58% and 73%, respectively; and (2) high risk, including poor-risk K, FLT3-ITD mutated cases, good/intermediate K-MRD(+) categories, with RFS and OS of 22% and 17%, respectively (P < .001 for all comparisons). In AML, the integrated evaluation of baseline prognosticators and MRD improves risk-assessment and optimizes postremission therapy.

Shortcomings in the clinical evaluation of new drugs: acute myeloid leukemia as paradigm

Drugs introduced over the past 25 years have benefitted many patients with acute myeloid leukemia (AML) and provided cure for some. Still, AML remains difficult to treat, and most patients will eventually die from their disease. Therefore, novel drugs and drug combinations are under intense investigation, and promising results eagerly awaited and embraced. However, drug development is lengthy and costs are staggering. While the phase 1-phase 2-phase 3 sequence of clinical drug testing has remained inviolate for decades, it appears intrinsically inefficient, and scientific flaws have been noted by many authors. Of major concern is the high frequency of false-positive results obtained in phase 2 studies. Here, we review features of phase 2 trials in AML that may contribute to this problem, particularly lack of control groups, patient heterogeneity, selection bias, and choice of end points. Recognizing these problems and challenges should provide us with opportunities to make drug development more efficient and less costly. We also suggest strategies for trial design improvement. Although our focus is on the treatment of AML, the principles that we highlight should be broadly applicable to the evaluation of new treatments for a variety of diseases.

Kit inhibitor APcK110 extends survival in an AML xenograft mouse model

BACKGROUND

Constitutive activation of kit contributes to pathogenesis of acute myeloid leukemia (AML) and targeting Kit may be of therapeutic benefit. APcK110, a novel inhibitor of Kit, has potent proapoptotic and antiproliferative activity in AML cell lines and primary AML samples. Here we extend our studies to the activity of APcK110 in a xenograft mouse model.

METHODS

After sub-lethal whole body radiation, OCI/AML3 cells were injected intravenously in NOD-SCID mice. Ten days later, either APcK110 or phosphate buffered saline (PBS) was injected intraperitoneally every other day. Kaplan-Meier estimates were used to calculate survival.

RESULTS

We show that 1) all mice injected with OCI/AML3 cells developed a clinical and histological picture consistent with myelomonocytic AML; and 2) survival of APcK110-treated mice was significantly longer compared with mice injected with PBS (p = .02).

CONCLUSIONS

APcK110 is a novel kit kinase inhibitor with anti-AML activity in vitro and in vivo. Further evaluation in toxicology and clinical studies is warranted.

Cytogenetics of Childhood Acute Myeloid Leukemia: United Kingdom Medical Research Council Treatment Trials AML 10 and 12

Purpose

Karyotype is an independent indicator of prognosis in acute myeloid leukemia (AML) that is widely applied to risk-adapted therapy. Because AML is rare in children, the true prognostic significance of individual chromosomal abnormalities in this age group remains unclear.

Patients and Methods

This cytogenetic study of 729 childhood patients classified them into 22 subgroups and evaluated their incidence and risk.

Results

Rearrangements of 11q23 were the most frequent abnormality found in approximately 16% of patients, with 50% of these in infants. The outcome for all patients with 11q23 abnormalities was intermediate; no difference was observed for those with t(9;11)(p21-22;q23). The core binding factor leukemias with the translocations t(8;21)(q22;q22) and inv(16)(p13q22) occurred at incidences of 14% and 7%, respectively, predominantly in older children, and their prognosis was favorable. An adverse outcome was observed in patients with monosomy 7, abnormalities of 5q, and t(6;9)(p23;q34). Abnormalities of 3q and complex karyotypes, in the absence of favorable-risk features, have been associated with an adverse outcome in adults, but the results were not significant in this childhood series. However, the presence of 12p abnormalities predicted a poor outcome.

Conclusion

Because the spectrum of chromosomal changes and their risk association seem to differ between children and adults with AML, biologic differences are emerging, which will contribute to the redefinition of risk stratification for different age groups in the future.

Acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous group of leukemias that result from clonal transformation of hematopoietic precursors through the acquisition of chromosomal rearrangements and multiple gene mutations. As a result of highly collaborative clinical research by pediatric cooperative cancer groups worldwide, disease-free survival has improved significantly during the past 3 decades. Further improvements in outcomes of children who have AML probably will reflect continued progress in understanding the biology of AML and the concomitant development of new molecularly targeted agents for use in combination with conventional chemotherapy drugs.