To explore the genetic abnormalities that cooperate with AML1-ETO (AE) fusion gene to cause acute myeloid leukemia (AML) with t(8;21), we screened a number of candidate genes and identified 11 types of mutations in C-KIT gene (mC-KIT), including 6 previously undescribed ones among 26 of 54 (48.1%) cases with t(8;21). To address a possible chronological order between AE and mC-KIT, we showed that, among patients with AE and mC-KIT, most leukemic cells at disease presentation harbored both genetic alteration, whereas in three such cases investigated during complete remission, only AE, but not mC-KIT, could be detected by allele-specific PCR. Therefore, mC-KIT should be a subsequent event on the basis of t(8;21). Furthermore, induced expression of AE in U937-A͞E cells significantly up-regulated mRNA and protein levels of C-KIT. This may lead to an alternative way of C-KIT activation and may explain the significantly higher C-KIT expression in 81.3% of patients with t(8;21) than in patients with other leukemias. These data strongly suggest that t(8;21) AML follows a stepwise model in leukemogenesis, i.e., AE represents the first, fundamental genetic hit to initiate the disease, whereas activation of the C-KIT pathway may be a second but also crucial hit for the development of a full-blown leukemia. Additionally, Gleevec suppressed the C-KIT activity and induced proliferation inhibition and apoptosis in cells bearing C-KIT N822K mutation or overexpression, but not in cells with D816 mC-KIT. Gleevec also exerted a synergic effect in apoptosis induction with cytarabine, thus providing a potential therapeutic for t(8;21) leukemia.A bnormalities in genes that encode transcription factors (TFs) and tyrosine kinases (TKs) represent two classes of the most frequently detected genetic events in human leukemias (1-3). Disruptions of TFs, often as results of recurring chromosomal translocations where fusion genes are generated, may lead to inhibition of hematopoietic differentiation and subsequent apoptosis, whereas mutations or alterations of TKs may confer proliferative and͞or survival advantage to hematopoietic stem͞ progenitor cells. Recent evidence suggests that alterations in TFs and TKs are required to cooperate in causing full-blown leukemia (3, 4). However, whether a causal relationship or a chronological order exists between the two genetic events remains largely unknown in a clinical setting.The t(8;21)(q22;q22), where coding sequences of the AML1 gene on chromosome 21 are juxtaposed to coding sequences of the ETO gene on chromosome 8 generating an AML1-ETO (AE) fusion transcript, represents the most common chromosomal translocation in acute myeloid leukemia (AML) (5). The AE chimeric protein recruits the N-CoR-mSin3-HDAC complex (6) and represses wild-type AML1, which is a crucial TF for hematopoiesis, modifies intranuclear targets of AML1 (5, 7), and even represses genes that normally are not regulated by AML1 (8). At cellular level, the AE fusion protein transforms NIH 3T3 cells and activates TF AP-1 (9), maintai...

SUMMARY Rapidly proliferating leukemic progenitor cells consume substantial glucose that may lead to glucose insufficiency in bone marrow. We show that acute myeloid leukemia (AML) cells are prone to fructose utilization with an upregulated fructose transporter GLUT5, compensating for glucose deficiency. Notably, AML patients with upregulated transcription of GLUT5-encoding gene SLC2A5 or increased fructose utilization have poor outcomes. Pharmacological blockage of fructose uptake ameliorates leukemic phenotypes and potentiates the cytotoxicity of antileukemic agent, Ara-C. In conclusion, this study highlights enhanced fructose utilization as a metabolic feature of AML and a potential therapeutic target.

Acquisition of additional genetic and/or epigenetic abnormalities other than the BCR/ABL fusion gene is believed to cause disease progression in chronic myeloid leukemia (CML) from chronic phase to blast crisis (BC). To gain insights into the underlying mechanisms of progression to BC, we screened DNA samples from CML patients during blast transformation for mutations in a number of transcription factor genes that are critical for myeloid-lymphoid development. In 85 cases of CML blast transformation, we identified two new mutations in the coding region of GATA-2, a negative regulator of hematopoietic stem/progenitor cell differentiation. A L359V substitution within zinc finger domain (ZF) 2 of GATA-2 was found in eight cases with myelomonoblastic features, whereas an in-frame deletion of 6 aa (⌬341-346) spanning the C-terminal border of ZF1 was detected in one patient at myeloid BC with eosinophilia. Further studies indicated that L359V not only increased transactivation activity of GATA-2 but also enhanced its inhibitory effects on the activity of PU.1, a major regulator of myelopoiesis. Consistent with the myelomonoblastic features of CML transformation with the GATA-2 L359V mutant, transduction of the GATA-2 L359V mutant into HL-60 cells or BCR/ABL-harboring murine cells disturbed myelomonocytic differentiation/proliferation in vitro and in vivo, respectively. These data strongly suggest that GATA-2 mutations may play a role in acute myeloid transformation in a subset of CML patients.blast crisis ͉ chronic phase ͉ genetic alteration ͉ transcriptional regulation

The full-length AML1-ETO (AE) fusion gene resulting from t(8;21) (q22;q22) in human acute myeloid leukemia (AML) is not sufficient to induce leukemia in animals, suggesting that additional mutations are required for leukemogenesis. We and others have identified activating mutations of C-KIT in nearly half of patients with t (8;21) AML. To test the hypothesis that activating C-KIT mutations cooperate with AE to cause overt AML, we generated a murine transduction and transplantation model with both mutated C-KIT and AE. To overcome the intracellular transport block of human C-KIT in murine cells, we engineered hybrid C-KIT (HyC-KIT) by fusing the extracellular and transmembrane domains of the murine c-Kit in-frame to the intracellular signaling domain of human C-KIT. We showed that tyrosine kinase domain mutants HyC-KIT N822K and D816V, as well as juxtamembrane mutants HyC-KIT 571+14 and 557-558Del, could transform murine 32D cells to cytokine-independent growth. The protein tyrosine kinase inhibitor dasatinib inhibited the proliferation of 32D cells expressing these C-KIT mutants, with potency in the low nanomolar range. In mice, HyC-KIT N822K induced a myeloproliferative disease, whereas HyC-KIT 571+14 induces both myeloproliferative disease and lymphocytic leukemia. Interestingly, coexpression of AE and HyC-KIT N822K led to fatal AML. Our data have further enriched the twohit model that abnormalities of both transcription factor and membrane/cytosolic signaling molecule are required in AML pathogenesis. Furthermore, dasatinib prolonged lifespan of mice bearing AE and HyC-KIT N822K-coexpressing leukemic cells and exerted synergic effects while combined with cytarabine, thus providing a potential therapeutic for t(8;21) leukemia.stem cell factor | mouse model | targeted therapy | combinatorial therapy | interleukin-3 T he t(8;21)(q22;q22) translocation, which generates AML1-ETO (AE) fusion gene, is one of the most common chromosomal abnormalities detected in acute myeloid leukemia (AML) (1, 2). A high-level expression of full-length AE can be detected in all patients with t(8;21) and is thus considered to play a fundamental role in this type of leukemia. Studies of several murine models have demonstrated, nevertheless, that AE alone is not sufficient to induce AML, in that no leukemia development was found in mice carrying an AE knockin allele (3, 4) in AE-transgenic mice (5, 6) or in wild-type (WT) mice that received a transplant of bone marrow (BM) cells transduced retrovirally with AE (7). Of note, in the presence of additional mutations [e.g., mutagen N-ethyl-N-nitrosourea (6), mutations of FLT3 (8), or the TEL-PDGFRβ fusion gene (9)], AE induces an AML phenotype. Moreover, ectopically expression of AE9a (a C-terminally truncated variant of AE) can induce AML in mice (10). These results indicate that full-length AE may need cooperation with other molecular events in initiating AML.Genetic abnormalities affecting transcription factors and mutations affecting genes involved in signal transduction represent two ...

Oridonin treats AML by generating a truncated version of the AML1-ETO oncoprotein that functions as a tumor suppressor.

No abstract

It has been generally acknowledged that the diagnosis, treatment and prognosis evaluation of leukemia largely rely on an adequate identification of genetic abnormalities. A systemic analysis of genetic aberrations was performed in a cohort of 1346 patients with newly diagnosed acute lymphoblastic leukemia (ALL) in China. The pediatric patients had higher incidence of hyperdiploidy and t(12;21) (p13;q22)/ETV6 --RUNX1 than adults (Po0.0001); in contrast, the occurrence of Ph and Ik6 variant of IKZF1 gene was much more frequent in adult patients (all Po0.0001). In B-ALL, the existence of Ik6 and that of BCR --ABL were statistically correlated (Po0.0001). In comparison with Western cohorts, the incidence of t(9;22) (q34;q11)/BCR --ABL (14.60%) in B-ALL and HOX11 expression in T-ALL (25.24%) seemed to be much higher in our group, while the incidence of t(12;21) (p13;q22)/ETV6 --RUNX1 (15.34%) seemed to be lower in Chinese pediatric patients. The occurrence of hyperdiploidy was much lower either in pediatric (10.61% vs 20 --38%) or adult patients (2.36% vs 6.77 --12%) in our study than in Western reports. In addition, the frequencies of HOX11L2 in adult patients were much higher in our cohort than in Western countries (20.69% vs 4 --11%). In general, it seems that Chinese ALL patients bear more adverse prognostic factors than their Western counterparts do.

The BCR-ABL fusion protein generated by t(9;22)(q34;q11) in chronic myeloid leukemia (CML) plays an essential role in the pathogenesis of the myeloproliferative disorder status at the chronic phase of the disease, but progression from the chronic phase to blast crisis (BC) is believed to require additional mutations. To explore the underlying mechanisms for BC, which is characterized by a blockage of blood cell differentiation, we screened several genes crucial to hematopoiesis