Isodicentric X chromosomes involving the Xq13 breakpoint in myelodysplasia and acute nonlymphocytic leukemia

Many nonrandom chromosome abnormalities, usually autosomal in nature, have been found to be associated with specific types of acute nonlymphocytic leukemia (ANLL) and myelodysplastic syndromes (MDS). Specific abnormalities involving the sex chromosomes are rare. We have recently identified a structural abnormality of the X chromosome, for example, idic(X)(q13) in three patients: two with MDS progressing to ANLL and one with ANLL de novo. All three patients were elderly females with a very aggressive form of ANLL. Six other patients with a similar abnormality have been discovered in the literature; all having either MDS or ANLL and a short survival. It is suggested that the abnormality identifies a subset of MDS and ANLL occurring in elderly females.     

Partial chromosome 21 amplification in a child with acute lymphoblastic leukemia

Monosomy 21 and metacentric markers corresponding in size to chromosomes 8 to 12 were found as the only clonal chromosomal changes in a child with acute lymphoblastic leukemia (ALL). Chromosome painting with a whole chromosome 21-specific probe showed that the marker originated from chromosome 21. Fluorescence in situ hybridization with yeast artificial chromosome (YAC) probes to chromosome 21 showed genomic amplification with two, four, or more copies of the probed DNA sequences present on the marker. The most amplified regions of chromosome 21 were centromeric and telomeric to the Down's syndrome region. This observation supports the notion that amplification of only parts of chromosome 21 may be important in the leukemogenic process in spite of the high incidence of complete trisomy 21 in ALL.     

Therapy-related acute myeloid leukemia/myelodysplasia with balanced 21q22 translocations

The morphologic and immunophenotypic findings of 36 cases of 21q22 acute myeloid leukemia (AML) and myelodysplasia (MDS) were compared, including 14 de novo t(8;21) AMLs, 11 t(8;21) therapy-related AML/MDS cases, and 11 therapy-related AML/MDS cases with other 21q22 balanced translocations [t(n;21)]. Cases were evaluated for the presence of Auer rods, distinct chunky cytoplasmic blast cell granules, promyelocyte increase, cytoplasmic perinuclear clearing (hofs) of blast cells, eosinophil increase, andfeatures of associated trilineage dysplasia. Results of immunophenotyping studies for CD19, CD34, and CD56 expression were compared. Cases of de novo and therapy-related t(8;21) disease shared common morphologic features of chunky cytoplasmic granules, perinuclear hofs, and promyelocyte increases that were not seen consistently in the t(n;21) group of t-AML/MDS cases. Immunophenotypic similarities also were observed between the 2 t(8;21) groups. De novo and therapy-related t(8;21) disease, however, differed by the frequent presence of associated dysplasia in both t-AML/MDS groups, which was infrequent in the de novo t(8;21) group. Therapy-related AMI/MDS with t(8;21) shares characteristic morphologic and immunophenotypic features with de novo t(8;21) AML, but frequently also occurs with associated myelodysplastic changes, similar to other therapy-related acute leukemias.     

Partial deletion of chromosome 1 in a case of acute myelocytic leukemia

Acute myelocytic leukemia (AML) is a malignant disease characterized by the proliferation of immature myelocytic precursor cells causing the disruption of normal bone marrow function. Many chromosomal aberrations have been described in AML including translocations, inversions, deletions, and additions. Here we describe a novel deletion of chromosome 1, del(1)(p34p36) in a case of AML, French-American-British classification M1, in a previously healthy 33-year-old male. This isolated cytogenetic abnormality occurred in 33% of the myeloblasts examined at diagnosis. Subsequent cytogenetic analyses conducted on marrow following induction and consolidation therapy demonstrated a normal male karyotype in all cells examined. The patient remains in clinical and hematological remission 22 months following diagnosis. The presence of 1p abnormalities in AML and other malignancies is reviewed, as are candidate tumor suppressor genes in the 1p34 approximately p36 region. The implications of chromosome 1p abnormalities on clinical outcome are also discussed.     

c-myc gene amplification and N-ras transforming gene in two cases of acute myelocytic leukemia with double minute chromosomes

We report two leukemia patients with double minutes (DMs) chromosomes. Both patients were diagnosed as having acute myelocytic leukemia (AML) FAB M2. Cytogenetic analysis showed normal chromosome karyotype with 1-53 DMs chromosomes in the first patient, and complex chromosome aberrations including deletion of chromosome 8 at 8q24 region and 1-84 DMs chromosomes in the second patient who had a history of extensive radiotherapy for laryngeal cancer 8 years prior to the development of leukemia. Analysis of DNA from the two patients revealed that oncogene of c-myc was amplified about 5 to 10 folds in the leukemic cells. The other fourteen oncogene of c-myc was c-myb, c-abl and N-myc, showed no increases of gene content. Furthermore, a transforming gene, N-ras was detected in the first patient by in vivo selection assay method. This is the second report on AML patients with c-myc gene amplification and DMs chromosomes.     

A diminutive chromosome 21 centromere in acute lymphoblastic leukemia

A chance observation of a tiny constitutional variant for the centromere of chromosome 21 in two patients with acute lymphoblastic leukemia (ALL), suggested a possible correlation with the cytogenetic findings in their leukemic cells. Interphase FISH revealed three 13/21 centromeric signals and a single MLL signal in the blast cells of each patient. Metaphase FISH with dual-color application of whole-chromosome paint (wcp) and centromeric probes for chromosome 21 showed two copies of chromosome 21, one with a tiny centromeric signal which corresponded to the invisible centromere in the interphase cells. Patient 2700 had a normal karyotype in his bone marrow at diagnosis. All metaphases from his stimulated peripheral blood also had the tiny chromosome 21 centromere, proving it to be a constitutional variant. Patient 3314 showed the abnormal karyotype 46,XY,inv(1)(p?q?),del(11)(q?),del(12)(p?),inc in his bone marrow. Interphase FISH revealed only one copy each of the ABL and ETV6 genes, in addition to the loss of the MLL signal. The question arises, is there an association between the diminutive centromeric signals for chromosome 21 and the chromosomal instability demonstrated by the deletions of key genes from the leukemic blasts of these two patients?     

Multiple genetic events involving rbi gene deletion and amplification of chromosome 21 in a case of acute lymphocytic leukemia

A patient with acute lymphocytic leukemia was found to have a hyperdiploid karyotype, characterized by hexasomy 21 and del(7)(p15). It was shown that the four extra copies of chromosome 21 were all derived from only one of the homologous chromosomes. Molecular analysis showed that the patient had a deletion of both alleles of the retinoblastoma (RBI) gene. These results suggest that multiple events, including loss of RBI gene function and amplification of a key gene(s) on chromosome 21, have contributed to the leukemic transformation. Genes Chrom Cancer 9:72-75 (1994). © 1994 Wiley-Liss, Inc.     

Chromosome 21 abnormalities with AML1 amplification in acute lymphoblastic leukemia

Fluorescence in situ hybridization (FISH) studies were performed in three cases of acute lymphoblastic leukemia (ALL) with marker chromosomes to analyze the contribution of chromosome 21 in these markers. FISH with a chromosome 21 painting probe confirmed that chromosome 21 was involved in all three cases. FISH with YAC probes showed that the number of extra copies varied according to their location on chromosome 21. Attention was focused on the AML1 gene, which was present as five copies in most of the cells exhibiting the marker chromosomes. As controls, 11 cases of childhood ALL were studied with PAC probes covering AML1. The results agreed with the banded karyotypes in 10 patients. FISH uncovered a clone with four copies of AML1 which were only observed by FISH analysis of interphase nuclei in one patient. No point mutation was detected in exons 3-5, encoding the runt domain of AML1, in the three cases, suggesting an oncogenic role of wild-type AML1 amplification.     

Novel translocations in acute nonlymphocytic leukemia. Two cases involving chromosome 21, band q22

We present two cases in which translocations involving 21q22 were found at presentation in acute nonlymphocytic leukemia (ANLL). The first of these translocations, t(3;21)(q26-q27;q22), is previously unknown in ANLL, but appears indistinguishable from that reportedly associated with Philadelphia-positive chronic myelogenous leukemia. The second case involves t(15;21)(q21-q22;q22), a translocation previously undescribed in ANLL. Both of these exchanges involve 21q22 plus another chromosome region associated with leukemogenesis. We attempted to interrelate these cytogenetic data with the oncogenic significance of 21q22.     

Normal bone marrow karyotype in acute leukemia or myelodysplasia following rheumatoid arthritis?

Cytogenetic analyses by means of trypsin-Giemsa banding technique were performed on bone marrow cells from a total of 12 patients--nine with acute nonlymphocytic leukemia and three with myelodysplastic syndrome--and a history of rheumatoid arthritis. Clonal chromosomal abnormalities were identified in two patients with previous exposure to petroleum products, and radiation therapy for a malignant tumor, respectively; one additional patient had a loss of the Y chromosome as the sole aberration. All the remaining nine patients had completely normal karyotypes. Seven patients had received treatment for rheumatoid arthritis with mutagenic drugs. Acute nonlymphocytic leukemia or myelodysplastic syndrome secondary to cytotoxic treatment for a previous malignancy display multiple, usually complex, structural and numerical chromosomal abnormalities in the majority of cases. The contrasting findings in the present patient series suggest other pathogenetic mechanisms in acute nonlymphocytic leukemia and myelodysplastic syndrome following rheumatoid arthritis.     

BCR/ABL amplification in chronic myelocytic leukemia blast crisis following imatinib mesylate administration

The onset of accelerated phase or blast crisis of chronic myelocytic leukemia (CML) is usually associated with the acquisition of new chromosome abnormalities in addition to the t(9;22)(q34;q11) that is characteristic of the chronic phase CML. We describe the cytogenetic and molecular genetic findings in two cases of myelocytic blast crisis of CML, one occurring 6 months after commencing treatment with the ABL-specific tyrosine kinase inhibitor imatinib mesylate (STI571, Glivec, or Gleevec) and the second treated with imatinib mesylate for established blast crisis. In both cases, multiple secondary cytogenetic abnormalities were observed at transformation, with homogeneously staining regions that were shown to contain BCR/ABL amplification by fluorescence in situ hybridization appearing after imatinib mesylate administration. BCR/ABL amplification is emerging as an important mechanism of acquired resistance to imatinib mesylate.     

Development and progression of a Philadelphia-chromosome-negative acute myelocytic leukemia clone in a patient with Philadelphia-chromosome-positive chronic myelocytic leukemia

We report a patient with typical Philadelphia-chromosome-positive chronic myelocytic leukemia who developed Philadelphia-chromosome-negative acute myelocytic leukemia following autologous stem cell transplantation. The implications of this observation for disease monitoring and treatment are discussed.