In acute myeloid leukemia (AML), aberrant expression and mutations of transcription factors have been correlated with disease outcome. In the present study, we performed expression and mutation ...screening of GATA2, which is an essential transcription factor for regulation of myeloid lineage determination, in de novo pediatric AML patients. GATA2 mutations were detected in 5 of 230 patients, representing a frequency of 2.2% overall and 9.8% in cytogenetically normal AML. GATA2 expression analysis demonstrated that in 155 of 237 diagnostic samples (65%), GATA2 expression was higher than in normal BM. In complete remission, normalization of GATA2 expression was observed, whereas GATA2 expression levels stayed high in patients with resistant disease. High GATA2 expression at diagnosis was an independent poor prognostic factor for overall survival (hazard ratio HR = 1.7, P = .045), event-free survival (HR = 2.1, P = .002), and disease-free survival (HR = 2.3, P = .004). The prognostic impact of GATA2 was particularly evident in specific AML subgroups. In patients with French-American-British M5 morphology, inv(16), or high WT1 expression, significant differences in survival were observed between patients with high versus normal GATA2 expression. We conclude that high GATA2 expression is a novel poor prognostic marker in pediatric AML, which may contribute to better risk-group stratification and risk-adapted therapy in the future.
In myelodysplastic syndromes (MDS), deletions of chromosome 7 or 7q are common and correlate with a poor prognosis. The relevant genes on chromosome 7 are unknown. We report here that EZH2, located ...at 7q36.1, is frequently targeted in MDS. Analysis of EZH2 deletions, missense and frameshift mutations strongly suggests that EZH2 is a tumor suppressor. As EZH2 functions as a histone methyltransferase, abnormal histone modification may contribute to epigenetic deregulation in MDS.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Cancer development is a dynamic process during which the successive accumulation of mutations results in cells with increasingly malignant characteristics. Here, we show the clonal evolution pattern ...in myelodysplastic syndrome (MDS) patients receiving supportive care, with or without lenalidomide (follow-up 2.5-11 years). Whole-exome and targeted deep sequencing at multiple time points during the disease course reveals that both linear and branched evolutionary patterns occur with and without disease-modifying treatment. The application of disease-modifying therapy may create an evolutionary bottleneck after which more complex MDS, but also unrelated clones of haematopoietic cells, may emerge. In addition, subclones that acquired an additional mutation associated with treatment resistance (TP53) or disease progression (NRAS, KRAS) may be detected months before clinical changes become apparent. Monitoring the genetic landscape during the disease may help to guide treatment decisions.
Myelodysplastic syndromes (MDS) represent a heterogeneous group of neoplastic hematopoietic disorders. Several recurrent chromosomal aberrations have been associated with MDS, but the genes affected ...have remained largely unknown. To identify relevant genetic lesions involved in the pathogenesis of MDS, we conducted SNP array-based genomic profiling and genomic sequencing in 102 individuals with MDS and identified acquired deletions and missense and nonsense mutations in the TET2 gene in 26% of these individuals. Using allele-specific assays, we detected TET2 mutations in most of the bone marrow cells (median 96%). In addition, the mutations were encountered in various lineages of differentiation including CD34+ progenitor cells, suggesting that TET2 mutations occur early during disease evolution. In healthy tissues, TET2 expression was shown to be elevated in hematopoietic cells with highest expression in granulocytes, in line with a function in myelopoiesis. We conclude that TET2 is the most frequently mutated gene in MDS known so far.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Although the vast majority of patients with a myelodysplastic syndrome (MDS) suffer from cytopenias, the bone marrow is usually normocellular or hypercellular. Apoptosis of hematopoietic cells in the ...bone marrow has been implicated in this phenomenon. However, in MDS it remains only partially elucidated which genes are involved in this process and which hematopoietic cells are mainly affected. We employed sensitive real-time PCR technology to study 93 apoptosis-related genes and gene families in sorted immature CD34+ and the differentiating erythroid (CD71+) and monomyeloid (CD13/33+) bone marrow cells. Unsupervised cluster analysis of the expression signature readily distinguished the different cellular bone marrow fractions (CD34+, CD71+ and CD13/33+) from each other, but did not discriminate patients from healthy controls. When individual genes were regarded, several were found to be differentially expressed between patients and controls. Particularly, strong over-expression of BIK (BCL2-interacting killer) was observed in erythroid progenitor cells of low- and high-risk MDS patients (both p = 0.001) and TNFRSF4 (tumor necrosis factor receptor superfamily 4) was down-regulated in immature hematopoietic cells (p = 0.0023) of low-risk MDS patients compared to healthy bone marrow.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Amino acid dropout screen reveals that AML cells highly depend on methionine, cysteine, arginine, glutamine, and lysine.•Dietary methionine removal impacts on the proteome, metabolome and epigenome, ...perturbing AML progression in vivo.
Display omitted
Targeting altered tumor cell metabolism might provide an attractive opportunity for patients with acute myeloid leukemia (AML). An amino acid dropout screen on primary leukemic stem cells and progenitor populations revealed a number of amino acid dependencies, of which methionine was one of the strongest. By using various metabolite rescue experiments, nuclear magnetic resonance−based metabolite quantifications and 13C-tracing, polysomal profiling, and chromatin immunoprecipitation sequencing, we identified that methionine is used predominantly for protein translation and to provide methyl groups to histones via S-adenosylmethionine for epigenetic marking. H3K36me3 was consistently the most heavily impacted mark following loss of methionine. Methionine depletion also reduced total RNA levels, enhanced apoptosis, and induced a cell cycle block. Reactive oxygen species levels were not increased following methionine depletion, and replacement of methionine with glutathione or N-acetylcysteine could not rescue phenotypes, excluding a role for methionine in controlling redox balance control in AML. Although considered to be an essential amino acid, methionine can be recycled from homocysteine. We uncovered that this is primarily performed by the enzyme methionine synthase and only when methionine availability becomes limiting. In vivo, dietary methionine starvation was not only tolerated by mice, but also significantly delayed both cell line and patient-derived AML progression. Finally, we show that inhibition of the H3K36-specific methyltransferase SETD2 phenocopies much of the cytotoxic effects of methionine depletion, providing a more targeted therapeutic approach. In conclusion, we show that methionine depletion is a vulnerability in AML that can be exploited therapeutically, and we provide mechanistic insight into how cells metabolize and recycle methionine.
Cunningham and colleagues report that AML blasts and leukemic stem cells (LSCs) uniquely depend on methionine for both protein translation and as a source of methyl groups to histones. Methionine depletion induces increased apoptosis and cell-cycle blockade in AML cells and LSCs but not in normal hematopoietic stem cells, suggesting a novel metabolic pathway that can be targeted therapeutically.
Abstract 1283
Poster Board I-305
Wilms' tumor 1 (WT1) and GATA binding protein 2 (GATA2) transcription factors are highly expressed in hematopoietic stem cells and progenitors. Differentiation of ...precursor blood cells towards mature blood cells is accompanied by rapid downregulation of both transcription factors. Overexpression of WT1 has been observed in the majority of acute myeloid leukemia (AML) cases. Furthermore, in 10-15% of the AML cases mutations in the WT1 gene occur, which have been correlated with poor prognosis. Aberrant expression of GATA2 in AML has been described as well, but no mutations in this gene have been reported in AML so far. How the (aberrant) expression of WT1 and GATA2 is controlled is not completely clear. A regulatory role for microRNAs (miRNAs) has been described for several transcription factors which regulate hematopoiesis. MiRNAs negatively regulate gene expression by translational repression or degradation of target messenger RNAs (mRNAs). In the present study we investigated the interplay between miRNAs and transcription factors that are involved in myeloid development and malignant transformation towards AML. We studied the expression of 158 miRNAs in the APL cell line NB4 during induction of granulocytic differentiation with all-trans retinoic acid (ATRA). Quantitative PCR specific for mature miRNAs was performed (Applied Biosystems). Twenty out of 158 miRNAs were more than 10-fold upregulated upon differentiation induction with ATRA. MiR-132 and miR212, which are derived from the same pri-miRNA transcript, were most strongly upregulated during ATRA-induced granulocytic differentiation (1200- and 350-fold respectively at 96 hours after ATRA-stimulation). In vitro ATRA-induction of primary APL cells also resulted in upregulation of miR-132 and miR-212. Computational target prediction algorithms were used to identify transcription factors which may be targeted by miR-132 and miR-212. Subsequently, the expression pattern of the predicted targets was determined experimentally in NB4 cells before and after differentiation induction with ATRA using microarray-based mRNA profiling (Affymetrix). In addition, further verification of target gene expression during ATRA-induced differentiation was performed using quantitative PCR. The transcription factors WT1 and GATA2 were predicted as targets of miR-132 and miR-212 by two out of four different prediction programs that were used. Both transcription factors contained putative binding sites for miR-132 and miR-212 in their 3'UTR. When tested on microarray and by quantitative PCR, the expression of WT1 and GATA2 was indeed strongly downregulated during ATRA-induced granulocytic differentiation of NB4 cells (65- and 165-fold respectively at 96 hours after ATRA stimulation) as well as in primary leukemia cells derived from APL patients (30- and 10-fold respectively at 48 hours after ATRA-stimulation). During ATRA-induced differentiation the expression levels of WT1 were positively correlated with the expression levels of GATA2. In addition, WT1 expression was also strongly correlated with GATA2 expression in a cohort of 27 pre-treatment AML cases as well as in 7 healthy controls, suggesting that these genes might be co-regulated to a large extent. To directly prove that WT1 and GATA2 are indeed targeted by miR-132 and miR-212, we are currently performing lentiviral-based overexpression studies of both miRNAs to determine the effect on endogenous WT1 and GATA2 mRNA expression. MicroRNAs which target WT1 and GATA2 may be valuable tools in controlling the aberrant expression of WT1 and GATA2 observed in AML.
No relevant conflicts of interest to declare.
PDF
