Shigeo Horiike

Tandem duplications of the FLT3 receptor gene are associated with leukemic transformation of myelodysplasia.

We recently reported an internal tandem duplication of the human flt3 receptor gene (FLT3) as a somatic mutation in 17% of acute myelogenous leukemia (AML). The present study revealed the duplication at the juxtamembrane and the first tyrosine kinase domains of FLT3 in seven of 92 (8%) patients with myelodysplastic syndrome (MDS) and AML with trilineage myelodysplasia (AML/TMDS), the diseases which may represent neoplastic changes of pluripotent stem cells. A tandem duplication of exon 11 of FLT3 was harbored by two of 58 (3%) patients with MDS and five of 34 (15%) with overt leukemia, including MDS-derived leukemia, AML/TMDS and therapy-related leukemia. Although the duplicated regions varied within exon 11 in each case, they occurred in-frame, and altered mRNA expressions were demonstrated by reverse-transcription polymerase chain reaction. Two cases of MDS with a FLT3 duplication transformed to overt leukemia within a few months. Longitudinal analyses in two other patients with leukemia revealed that the duplication was a late genetic event during the disease course; one of whom showed two independent duplications of FLT3 at the terminal therapy-resistant phase. Of seven patients with the FLT3 duplication, six had abnormal karyotypes, and four harbored a point mutation of the N-RAS and/or TP53 genes. Patients with FLT3 mutations have poor prognoses. This study uncovered the fact that the accumulation of genetic events, including FLT3 duplication, correlates with leukemic transformation from antecedent myelodysplasia and with subsequent disease progression.

Chromosome abnormalities and karyotypic evolution in 83 patients with myelodysplastic syndrome and predictive value for prognosis.

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.

Combined spectral karyotyping and DAPI banding analysis of chromosome abnormalities in myelodysplastic syndrome.

Spectral karyotyping (SKY) is a new molecular cytogenetic technique that allows simultaneous visualization of each chromosome in a different color. We have used SKY for comprehensive analysis of 20 myelodysplastic syndromes (MDSs) (13 primary MDSs, 3 therapy‐related MDSs, and 4 acute leukemias developed from MDS, including 1 cell line established from a secondary leukemia), previously analyzed by G‐banding. To locate the chromosomal breakpoints, DAPI‐counterstained band images from all metaphases were transformed to G‐band–like patterns. By using SKY, it was possible to identify the origin and organization of all clonal marker chromosomes (mar), as well as the origin of all abnormalities defined as additional material of unknown origin (add) or homogeneously staining regions (hsr) by G‐banding. In total, SKY identified the chromosomal basis of 38 mar, add, and hsr, corrected 8 abnormalities misidentified by G‐banding, and revealed 6 cryptic translocations in 5 cases. Total or partial chromosomal loss (mainly of ‐5/5q‐ and ‐7/7q‐) is the most frequent cytogenetic abnormality in MDS. In 3 of 11 cases with ‐5/5q‐ and in 4 of 8 with ‐7/7q‐, lost material was detected by SKY in unbalanced translocations. A total of 60 chromosomal losses were identified by G‐banding in 16 cases with multiple chromosome abnormalities involving at least 3 chromosomes. For 26 of these losses (43%), SKY analysis suggested that the losses were not complete, but had been translocated to a variety of partner chromosomes. Moreover, SKY analysis revealed that a ring chromosome in a case of acute leukemia developed from MDS contained three to six segments that originated from chromosome 21 material. Fluorescence in situ hybridization showed the amplification of the AML1 gene on regions derived from chromosome 21, providing the first evidence of amplification involving this gene in MDS. Genes Chromosomes Cancer 26:336–345, 1999.

International prognostic scoring system and TP53 mutations are independent prognostic indicators for patients with myelodysplastic syndrome

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.

Distinct genetic involvement of the TP53 gene in therapy-related leukemia and myelodysplasia with chromosomal losses of Nos 5 and/or 7 and its possible relationship to replication error phenotype

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.

Genotype of glutathione S-transferase and other genetic configurations in myelodysplasia

We examined polymorphisms of glutathione S-transferase (GST) genes in 159 Japanese patients with myelodysplasia and compared the incidence with that in 43 normal individuals to clarify their pathogenetic significance in myelodysplasia. In individuals with the GSTT1 null genotype, the odds ratios for disease risk were elevated to 2.65 (95%CI; 1.27-5.52) in de novo MDS, 4.62 (1.48-14.4) in therapy-related AML, and 2.94 (1.07-8.07) in AML with triliniage dysplasia. Other representative polymorphisms of GSTs had a similar incidence among patients with myelodysplasia, and those of the controls and other hematological disorders. To further investigate the genetic pathway of myelodysplasia, the association between GST genotype and karyotype or configurations of TP53 and NRAS was evaluated, but no relationship was noted. These results suggest that the GSTT1 null genotype may play a role in an increased risk of myelodysplasia unrelated to other mechanisms of myelodysplasia, such as chromosomal alterations or mutation of TP53 or NRAS.

The unbalanced 1;7 translocation in de novo myelodysplastic syndrome and its clinical implication

In our chromosome study of 97 patients with myelodysplastic syndrome (MDS), six showed an unbalanced translocation between chromosomes 1 and 7 [−7, +der(1)t(1;7)(p11;p11)]. All of them had morphologic myelodysplasia in trilineage of bone marrow cells, and cytopenia was the major finding in the peripheral blood. All six patients had symptoms of infection at the time of diagnosis, and five showed immunologic abnormalities (polyclonal hypergammaglobulinemia in four and increased marrow plasma cells in three). None of the patients survived more than 11 months after the diagnosis; the median survival time was 4 months. Both of the two patients whose karyotypes were reexamined in the course of their disease showed karyotypic evolution accompanying the coincidental leukemic transformation. Six patients with MDS who had the same chromosome abnormality [t(1;7)] are described and their characteristic clinical features are presented.

Prefixation treatment with ethidium bromide for high resolution banding analysis of chromosomes from cultured human bone marrow cells

Prefixation treatment of cultured human bone marrow cells with a DNA intercalating agent, ethidium bromide (EBr), induced a dose- and time-related elongation of chromosomes. When compared with EBr-free cultures, a 2.9-fold increase in the yield of early mitotic cells with more than 400 bands per haploid set of chromosomes was achieved by simply adding 10 micrograms/ml of EBr during the last 2 hours of culture. The proportion of early mitotic cells was equal to that obtained in methotrexate synchronized cultures. Fluorescence banding methods using base composition specific agents actinomycin D/DAPI for AT base pairs and chromomycin A3/distamycin A for GC suggested that EBr does not have base specificity, because EBr did not alter the banding patterns of chromosomes obtained with these staining procedures.

Configuration of the TP53 Gene as an Independent Prognostic Parameter of Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) consists of a heterogeneous group of acquired hematopoietic stem cell disorders, characterized by bone marrow failure and leukemic transformation. Since hematological manifestations and clinical outcomes vary widely among MDS patients, a considerable number of studies have tried to identify the prognostic parameters for the stratification of patients into different risk groups. Based on reported risk-based studies, the International Prognostic Scoring System (IPSS) was proposed as a reliable risk assessment method for primary MDS patients, and several validating studies have clarified its usefulness. Critical prognostic parameters of the IPSS consist of chromosome findings, the percentage of marrow blasts, and the number of peripheral blood cytopenias. Although other laboratory findings, including several molecular alterations, have been identified as convincing prognostic factors in MDS, these molecular configurations were not selected as prognostic parameters in the IPSS, because analysis for these alterations were not routinely available for the management of patients with MDS. Because recent advances in molecular genetics may make it available as a routine work-up of MDS in the future, we discuss potential improvement of the IPSS by the addition of molecular analysis to the system, with particular reference to the configuration of the TP53 gene.

Differentiation of follicular from mucosa-associated lymphoid tissue lymphoma by detection of t(14;18) on single-cell preparations and paraffin-embedded sections.

A 57‐year‐old woman was referred to the Kyoto Prefectural University of Medicine because of multiple polypoid lesions in the duodenum. On the basis of the histopathologic findings, mucosa‐associated lymphoid tissue lymphoma had been diagnosed. The polypoid lesions did not show any improvement in spite of antimicrobial therapy for elimination of Helicobacter pylori. Because the disease remained stable during the clinical course, no other specific treatment was administered. We performed fluorescence in situ hybridization (FISH) analysis on a single‐cell preparation obtained from the duodenal lesions, to assess the specific chromosome translocation. We identified BCL2/IGH fusion at a frequency of 83%. Two‐color FISH was also performed on paraffin‐embedded tissue sections, which demonstrated BCL2/IGH fusion–positive cells in neoplastic follicles. These findings, together with the CD10+ immunophenotyping of tumor cells, led to a diagnosis of primary follicular lymphoma of the duodenum. Interphase FISH with the IGH gene and oncogene probes is a rapid and powerful tool for assessing genomic changes in gastrointestinal lymphoma on single‐cell preparations and tissue sections. This technique is particularly useful in view of the increasingly small core biopsy samples and needle aspirations obtained for diagnostic purposes.