In utero origin of t(8;21) AML1-ETO translocations in childhood acute myeloid leukemia

Recent reports have established the prenatal origin of leukemia translocations and resultant fusion genes in some patients, including MLL-AF4 translocations in infants and TEL-AML1 translocations in children. We now report evidence for the prenatal origin of a translocation in childhood acute myeloid leukemia (AML). The t(8;21) AML1-ETO translocations were sequenced at the genomic level in 10 diagnostic leukemia samples from children with available neonatal Guthrie blood spots. Clonotypic genomic AML1-ETO sequences were detected in the Guthrie spots for 5 individuals, providing unambiguous evidence of prenatal origin in these cases. Two of these patients were older than 10 years of age at diagnosis, indicative of a protracted postnatal latency. Three of the patients were assessed for the persistence of genomic fusion sequences in complete clinical remission samples and were found to be positive. These data indicate that t(8;21) in childhood AML can arise in utero, possibly as an initiating event in childhood AML, and may establish a long-lived or stable parental clone that requires additional secondary genetic alterations to cause leukemia.     

Treatment with a tyrosine-kinase inhibitor of for c-KIT mutation and AML1-ETO double positive refractory acute myeloid leukemia

Translocation (8;21)/AML1-ETO is considered a favorable cytogenetic abnormality in acute myeloid leukemia (AML). However, the outcomes associated with KIT mutations in AML1-ETO have not been elucidated. A 16-year-old boy was diagnosed with recurrent AML. Although he underwent hematopoietic stem cell transplantation (HSCT) twice, the leukemia relapsed and grew resistant to several chemotherapies. We began to treat him with imatinib, but stopped on the 31st day as it did not show any effects. Later, we administered dasatinib. However, we discontinued this because he showed severe nasal hemorrhage 87 days after administration of dasatinib. The therapeutic benefit of tyrosine-kinase inhibitor (TKI) was estimated by quantitative analysis of AML1-ETO and the patient's clinical impression. We did not conduct analyses to determine the effective concentration of TKI. The patient has not yet shown any major molecular response. Therefore, we conclude that TKI may be useful for slight palliation of symptoms in KIT-positive AML. However, patients with refractory AML associated KIT mutations in AML1-ETO should not be considered for TKI monotherapy.     

Identification of additional cytogenetic and molecular genetic abnormalities in acute myeloid leukaemia with t(8;21)/AML1-ETO

AML1-ETO collaborates with further genetic abnormalities to induce acute myeloid leukaemia (AML). We analysed 99 patients with an AML1-ETO rearrangement for additional aberrations. Frequent genetic abnormalities were, loss of a sex chromosome (56/99, 56.5%) and del(9)(q22) (24/99, 24.2%). The most frequent molecular aberrations were mutations of KITD816 (3/23, 13%) and NRAS (8/89, 8.9%). Further molecular abnormalities were FLT3 mutations (3/87, 3.4%), AML1 (1/26, 3.8%) and PU1 (1/14, 7.1%). MLL-PTD, KRAS and CEBPA mutations were not found. These clinical findings support the model that AML1-ETO collaborates with other genetic alterations, such as mutations of receptor tyrosine kinases, to induce AML.     

Frequency and clinical features of ASXL2 gene mutation in acute myeloid leukemia patients with AML1-ETO fusion gene positive

<正>Objective To investigate frequency and clinical features of additional sex combs-like 2(ASXL2)gene mutation in acute myeloid leukemia(AML)patients with AML1-ETO fusion gene and to analyze the relationship between ASXL2 gene mutation and c-kit gene mutation.Methods Mutation analysis of exon 11 and 12 of ASXL2     

AML1-ETO rapidly induces acute myeloblastic leukemia in cooperation with the Wilms tumor gene, WT1

AML1-ETO, a chimeric gene frequently detected in acute myelogenous leukemia (AML), inhibits the differentiation of myeloid progenitors by suppressing genes associated with myeloid differentiation and increases the replating ability of clonogenic myeloid progenitors. However, AML1-ETO alone cannot induce AML and thus additional genetic events are required for the onset of AML. The Wilms tumor gene (WT1), which has been identified as the gene responsible for Wilms tumor, is expressed at high levels in almost all human leukemias. In this study, we have generated transgenic mice (WT1-Tg) that overexpress WT1 in hematopoietic cells to investigate the effects of WT1 on AML1-ETO-associated leukemogenesis. AML1-ETO-transduced bone marrow (BM) cells from WT1-Tg mice exhibited inhibition of myeloid differentiation at more immature stages and higher in vitro colony-forming ability compared with AML1-ETO-transduced BM cells from wild-type mice. Most importantly, all of the mice that received a transplant of AML1-ETO-transduced BM cells from the WT1-Tg mice rapidly developed AML. These results demonstrate that AML1-ETO may exert its leukemogenic function in cooperation with the expression of WT1.     

Implications of somatic mutations in the AML1 gene in radiation-associated and therapy-related myelodysplastic syndrome/acute myeloid leukemia

Somatically acquired point mutations of AML1/RUNX1 gene have been recently identified in rare cases of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Moreover, germ line mutations of AML1 were found in an autosomal dominant disease, familial platelet disorder with predisposition to AML (FPD/AML), suggesting that AML1 mutants, as well as AML1 chimeras, contribute to the transformation of hematopoietic progenitors. In this report, we showed that AML1 point mutations were found in 6 (46%) of 13 MDS patients among atomic bomb (A-bomb) survivors in Hiroshima. Unlike acute or chronic leukemia patients among A-bomb survivors, MDS patients exposed relatively low-dose radiation and developed the disease after a long latency period. AML1 mutations also were found in 5 (38%) of 13 therapy-related AML/MDS patients who were treated with alkylating agents with or without local radiation therapy. In contrast, frequency of AML1 mutation in sporadic MDS patients was 2.7% (2 of 74). Among AML1 mutations identified in this study, truncated-type mutants lost DNA binding potential and trans-activation activity. All missense mutations with one exception (Gly42Arg) lacked DNA binding ability and down-regulated the trans-activation potential of wild-type AML1 in a dominant-negative fashion. The Gly42Arg mutation that was shared by 2 patients bound DNA even more avidly than wild-type AML1 and enhanced the trans-activation potential of normal AML1. These results suggest that AML1 point mutations are related to low-dose radiation or alkylating agents and play a role distinct from that of leukemogenic chimeras as a result of chromosomal translocations caused by sublethal radiation or topoisomerase II inhibitors.     

Treatment strategies in acute myeloid leukemia (AML)

Summary Chemotherapy remains the backbone of treatment in AML. Of all adult patients 65% go into remission and have a chance of longer survival and of even being cured. Among the responders, 25% can be cured by intensive and long-term chemotherapy. Since the effect of chemotherapy appears not to be limited to a special period of time, its antileukemic and curative potential could be further exploited by multiple-step chemotherapy combining double induction, intensified consolidation and long-term maintenance. Improved antimicrobial treatment and the use of hematopoietic growth factors may help making multiple-step chemotherapy practicable, thereby increasing the cure rate in AML.The studies of the AML Cooperative Group (AMLCG) are supported by grants OIZP 0123 and 8701 of the Ministry of Research and Technology of the Federal Republic of GermanyDedicated to Professor Dr. Drs. h.c. Franz Büchner on his 95th birthday