In this study, we examined a large number of patients to clarify FLT3 gene has some structural similarities including the the distribution and frequency of a recently described FLT3 tannumber of exons, size of exons and exon/intron boundaries dem duplication among hematopoietic malignancies, including with genes RTKs, FMS, KIT, and platelet-derived growth-factor of 24 showed internal tandem duplication with or withoutWe recently demonstrated internal tandem duplication insertion of nucleotides. In one AML, insertion and deletion within JM/TK-I domains as a somatic mutation of FLT3 found without duplication was determined. All 24 lengthened in 17% of patients with acute myelogenous leukemia (AML). 14 sequences were in-frame. Duplication takes place in the Since this mutation was not found in any patients with acute sequence coding for the JM domain and leaves the TK domain lymphocytic leukemia, we described that this mutation could intact. In conclusion, we emphasize that the length mutation of FLT3 at JM/TK-I domains were restricted to AML and MDS.be specific in myeloid malignancies. To clarify the incidence Since all these mutations resulted in in-frame, this abnormality and distribution of the FLT3 mutation among hematological might function for the proliferation of leukemic cells.malignancies, we examined a large number of patients with

We recently reported an internal tandem duplication of the receptor-type tyrosine kinases (RTKs), 8,9 ses were also performed to reveal the time when the mutation duplication transformed to overt leukemia within a few months.emerged. Together with the FLT3 mutation, chromosome fin-

By the addition of specific chemical agents to the culture medium, the HL-60 leukemia cell line, derived from a patient with acute promyelocytic leukemia (1), can be induced to mature to cells with many of the functional, morphological, and biochemical features of either neutrophils or macrophages (2, 3). Two recent studies strongly suggested that HL-60 cells also differentiated to eosinophils when cultured in soft agar (4, 5); the colonies from soft agar stained with Luxolfast-blue, a stain specific (among hematopoietic cells) for eosinophilic granules (6). Unfortunately, few cells differentiated to eosinophils, and it was technically difficult to harvest cells from semi-solid medium. These factors limit the usefulness of that system as a model for eosinophilopoiesis. Furthermore, the two reports disagreed on the role of added colony-stimulating factors. The recent description of increased numbers of morphologically abnormal eosinophils in the bone marrow of patients with FAB type M4 leukemia (AMMoL) 1 who have abnormalities of chromosome 16, del(16)(q22) (7) and inv(16)(p 13q22) (8), has further focused attention on the phenomenon of eosinophilic differentiation of leukemia cells. We observed that HL-60 cells cultured in slightly alkaline liquid medium develop granules typical in appearance to those found in eosinophils and eosinophilic precursors. Our higher induction efficiency and ease in harvesting cells from liquid culture permitted a more complete characterization of the differentiated cells. To determine whether HL-60 cells might serve as a model system for eosinophilopoiesis in general, or eosinophilic differentiation of leukemia cells in particular, the HL-60-derived eosinophils were characterized morphologically, histochemically, and cytogenetically.

We examined chromosomes and molecular aberrations in 21 patients with therapy-related leukemias (t-AML) or myelodysplastic syndromes (t-MDS). All patients showed abnormal karyotypes, and chromosomal losses of No. 5 and/or No. 7 (−5/5q− and/or −7/7q−) were identified in 12 patients. Among these 12, six patients (50%) harbored a TP53 mutation, and two of five examined showed microsatellite instability, suggesting replication error (RER ؉ ) phenotype. Meanwhile, among the other nine patients without −5/5q− and/or −7/7q−, none harbored a TP53 mutation, and none of five examined showed RER ؉ phenotype. Thus, TP53 mutations and RER ؉ phenotype were preferentially associated with specific chromosomal losses in t-AML/MDS. We then screened for mutational events in representative DNA mismatch repair genes; exons 5-7 and 12-15 of the hMSH2 gene and exon 9 of hMLH1. Notably, two unrelated patients showing RER ؉ phenotype had an identical missense alteration at codon 419 of hMSH2 in their marrow cells and fibroblasts, which were not found in 120 DNA samples from healthy volunteers or patients with other hematological disorders. Consequently, this study revealed a possible relationship of RER ؉ phenotype accompanying an hMSH2 alteration to the development of therapy-related AML/MDS in association with TP53 mutations and specific chromosomal losses, and suggests that some patients may be predisposed to myelodysplasia after chemotherapy for their primary tumor.

Summary. We applied the International Prognostic Scoring System (IPSS) to our series of 118 patients with myelodysplastic syndrome (MDS) to determine its validity, and also used univariate and multivariate analyses to evaluate the prognostic significance of TP53 configurations. Sixteen patients with the mutation had a strikingly worse prognosis and the multivariate analysis demonstrated that this alteration was the most significant factor. The prognostic comparison between patients with and without the mutation within each IPSS subgroup showed a significant difference in the intermediate subgroups. A combination of clinical manifestations and genetic configurations provided us with more accurate prognostic information in MDS patients.

We examined TP53 mutation in 57 patients with myelodysplastic syndrome (MDS) at either the MDS phase or at the terminal leukemic phase using polymerase chain reaction-mediated single-strand conformation polymorphism (PCR-SSCP) analysis. TP53 mutations within exons 5 through 8 were found in seven patients. All these mutations were detected at the presentation of MDS whether these patients showed leukemic transformation or not. TP53 mutations were frequently found in patients with loss of the short arm of chromosome 17 (17p-) (three of seven patients with 17p-, 43%) and complex karyotypic abnormalities (five of 14, 38%). Among the seven patients with the TP53 mutation, four patients progressed to acute leukemia within 7 months from the diagnosis of MDS, and the remaining three died within 7 months without leukemic transformation. These findings suggest that mutations of the TP53 can be implicated in leukemic transformation and a poor prognosis in MDS.

In a chromosome study of 83 patients with myelodysplastic syndrome (MDS), 50 showed a clonally abnormal karyotype. The most frequent abnormalities were the whole or a partial loss of the long arm of chromosome 7 (-7 or 7q-) (14 patients) and a partial loss of the long arm of chromosome 5 (5q-) (11 patients). Twenty patients with 5q- and/or -7 or 7q- had a shorter survival (median, 5 months) than those with other abnormal karyotypes (22 months) or those with a normal karyotype (28 months). In this series 30 patients were examined cytogenetically on two or more occasions during the course of their illness. Ten patients showed a further karyotypic alteration from the initial findings, and, concomitantly, their disease progressed in severity including overt leukemia. These patients had a shorter survival (median, 2 months) after the chromosome reanalysis than the other 20 patients who did not have further karyotypic changes (21 months). Thus, the prognosis of patients with MDS can be predicted more accurately by reanalyzing the chromosomes after the initial analysis.

We describe a patient who had aggressive natural killer cell leukemia with profound hemophagocytosis. This combination must be underscored as one of several hemophagocytic syndromes. Activated phagocytes in the bone marrow appeared morphologically normal and could possibly be proliferating in response to some cytokine(s) such as interferon-gamma produced by leukemic cells, whose serum level was found to be extremely elevated in this case.