IDH1 and IDH2 gene mutations identify novel molecular subsets within de novo cytogenetically normal acute myeloid leukemia: a Cancer and Leukemia Group B study

IDH mutations in glioma and acute myeloid leukemia

The systematic sequencing of glioblastoma multiforme (GBM) genomes has identified the recurrent mutation of IDH1, a gene encoding NADP(+)-dependent isocitrate dehydrogenase 1 (IDH1) that catalyzes the oxidative decarboxylation of isocitrate yielding alpha-ketoglutarate (alpha-KG). Subsequent studies have confirmed recurrent IDH1 and IDH2 mutations in up to 70% of low-grade glioma and secondary GBM, as well as in 10% of acute myeloid leukemia (AML) cases. The heterozygous somatic mutations at arginine R132 (IDH1) and at R140 or R172 (IDH2) in the enzyme active site confer a gain of function to the enzymes, which can both produce the metabolite 2-hydroxyglutarate. This review surveys the prevalence of IDH mutations in cancer and explores current mechanistic understanding of IDH mutations with implications for diagnostic and therapeutic development for the treatment of gliomas and AML.

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.

The prognostic significance of IDH1 mutations in younger adult patients with acute myeloid leukemia is dependent on FLT3/ITD status

Mutations in the isocitrate dehydrogenase gene (IDH1) were recently described in patients with acute myeloid leukemia (AML). To investigate their prognostic significance we determined IDH1 status in 1333 young adult patients, excluding acute promyelocytic leukemia, treated in the United Kingdom MRC AML10 and 12 trials. A mutation was detected in 107 patients (8%). Most IDH1(+) patients (91%) had intermediate-risk cytogenetics. Mutations correlated significantly with an NPM1 mutation (P < .0001) but not a FLT3/ITD (P = .9). No difference in outcome between IDH1(+) and IDH1(-) patients was found in univariate or multivariate analysis, or if the results were stratified by NPM1 mutation status. However, when stratified by FLT3/ITD status, an IDH1 mutation was an independent adverse factor for relapse in FLT3/ITD(-) patients (P = .008) and a favorable factor in FLT3/ITD(+) patients (P = .02). These results suggest that metabolic changes induced by an IDH1 mutation may influence chemoresistance in a manner that is context-dependent.

IDH1 and IDH2 mutation studies in 1473 patients with chronic-, fibrotic- or blast-phase essential thrombocythemia, polycythemia vera or myelofibrosis

In a multi-institutional collaborative project, 1473 patients with myeloproliferative neoplasms (MPN) were screened for isocitrate dehydrogenase 1 (IDH1)/IDH2 mutations: 594 essential thrombocythemia (ET), 421 polycythemia vera (PV), 312 primary myelofibrosis (PMF), 95 post-PV/ET MF and 51 blast-phase MPN. A total of 38 IDH mutations (18 IDH1-R132, 19 IDH2-R140 and 1 IDH2-R172) were detected: 5 (0.8%) ET, 8 (1.9%) PV, 13 (4.2%) PMF, 1 (1%) post-PV/ET MF and 11 (21.6%) blast-phase MPN (P<0.01). Mutant IDH was documented in the presence or absence of JAK2, MPL and TET2 mutations, with similar mutational frequencies. However, IDH-mutated patients were more likely to be nullizygous for JAK2 46/1 haplotype, especially in PMF (P=0.04), and less likely to display complex karyotype, in blast-phase disease (P<0.01). In chronic-phase PMF, JAK2 46/1 haplotype nullizygosity (P<0.01; hazard ratio (HR) 2.9, 95% confidence interval (CI) 1.7-5.2), but not IDH mutational status (P=0.55; HR 1.3, 95% CI 0.5-3.4), had an adverse effect on survival. This was confirmed by multivariable analysis. In contrast, in both blast-phase PMF (P=0.04) and blast-phase MPN (P=0.01), the presence of an IDH mutation predicted worse survival. The current study clarifies disease- and stage-specific IDH mutation incidence and prognostic relevance in MPN and provides additional evidence for the biological effect of distinct JAK2 haplotypes.

High cytogenetic or molecular genetic risk acute myeloid leukemia

Resistance, manifested as failure to enter remission despite living long enough to do so or as relapse from remission, is the principal cause of therapeutic failure in acute myeloid leukemia, even in patients age ≥ 75. Recently, a "monosomal karyotype" in acute myeloid leukemia blasts has been found to be a principal predictor of resistance. It is also clear that patients with a normal karyotype, and other intermediate prognosis karyotypes, can be placed into a high-risk group based on the absence of a mutation in the NPM1 gene or the presence of an internal tandem duplication (ITD) of the Fms-like tyrosine kinase 3 gene (FLT3) gene, particularly if there is loss of the wild-type FLT3 allele. The effects of other genetic abnormalities have been inconsistent, perhaps reflecting differences in expression of the abnormality and its translation into protein. Several reports have shown the prognostic potential of profiling global gene expression, micro-RNA expression, DNA methylation, and proteomics. Although routine application of these approaches is still premature, pretreatment assessment of the nucleophosmin 1 (NPM1) mutation and FLT3 ITD status, as well as cytogenetics, should be routine. These results can be used to guide the choice of remission induction therapy, for example, by placing patients with monosomal karyotype or FLT3 ITDs on clinical trials. Allogeneic hematopoietic cell transplant in first complete remission is generally indicated for high-risk patients. However, new approaches are needed to reduce the high rates of relapse, even after hematopoietic cell transplant.