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

Abstract

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. © 1999 Wiley‐Liss, Inc.

Amplification or duplication of chromosome band 21q22 with multiple copies of the AML1 gene and mutation of the TP53 gene in therapy-related MDS and AML

“…[10][11][12][13][14][15] Patient characteristics, karyotypes, results of FISH, and mutation status of TP53 and AML1 of the three cases are shown in Table 1.…”

“…This phenomenon has been observed in approximately 2% of patients with childhood acute lymphoblastic leukemia (ALL), [6][7][8][9] but to our knowledge only in seven cases of de novo MDS and AML. [10][11][12][13][14][15] In these seven patients the mutational status of TP53 was not examined. In t-MDS and t-AML a similar amplification or duplication of chromosome band 11q23 including the unrearranged MLL gene has been observed in 17% of the patients closely associated with mutations of the TP53 gene.…”

Fluorescence in situ hybridization improves the detection of 5q31 deletion in myelodysplastic syndromes without cytogenetic evidence of 5q-

“…[24][25][26][27][28][29] These studies demonstrate that FISH analysis can provide additional information about chromosome 5 abnormalities. It would, therefore, be recommendable to use FISH techniques to study those cases with monosomy 5 and/or marker chromosomes in order to identify translocations with a breakpoint in 5q or possible 5q-chromosomes.…”

New mechanisms of AML1 gene alteration in hematological malignancies

“…16 It has also been shown that the coiled-coil region of ETO could oligomerize with AML1-ETO protein, thus recruiting the nuclear corepressor N-CoR responsible for transcriptional repression of AML1 target genes and resulting in impaired differentiation of primary hematopoietic precursors. 17,18 Recently, we and others have reported other mechanisms of inactivation of AML1 in hematological malignancies, through point mutations of the gene in AML and in MDS [19][20][21][22][23][24][25] or through gene amplification, [26][27][28][29][30][31][32] a rare event mainly observed in acute lymphoblastic leukemia (ALL). In this review, we focused on those two other mechanisms of AML1 deregulation in hematological malignancies.…”