| Myelodysplastic syndrome (MDS) is an acquired clonal hematologic disorder, characterized by peripheral blood cytopenia, dysplastic changes in several hemopoietic cell lines at bone marrow and peripheral blood and the high risk of transforming to acute leukemia. About 40% to 70% of patients with MDS have nonrandom chromosome abnormalities detected by conventional cytogentics (CC), especially trisomy 8, monosomy 7/7q-, monosomy 5/5q- and 20q-. Recently, a consensus of International Prognostic Scoring System (IPSS) has ranked the percentage of bone marrow blasts, karyotypes, and the degree of cytopenias as the major risk factors for evaluating the prognosis in MDS. In 2000, the World Health Organization Classification of MDS brought forward chromosomes as an important diagnostic indicator. Therefore, karyotype analysis is very useful for diagnosis, differentiating diagnosis, prognostic evaluation and monitoring aberration clone in MDS. Whereas, only metaphases can be analyzed by CC, and some samples fail to produce a successful result or leave out the minor aberrant clone because of a low mitotic index or poor chromosome morphology. Fluorescence in situ hybridization (FISH), a newly developed technique which based on cytogenetics, molecular biology and immunology, is to use nucleic acid sequences labeled by a variety of fluorescein as specific probes to hybridize cellular DNA targets. Because FISH is more sensitive and specific than CC, it is becoming a powerful tool of molecularcytogenetics and an important complement to CC . Thus, FISH provides a new effective way for diagnosis, differentiating diagnosis, prognostic evaluation, and studying cell lineages involved in MDS.1. Detection of -5/5q->-7/7q-N+8 and 20q- chromosomal abnormalities in MDS by single color interphase fluorescence in situ hybridizationSingle color interphase FISH was used to detect the chromosome abnormalities in 48, 48, 52 and 67 MDS patients respectively by SpectrumRed or SpectrumGreen labeled yeast artificial chromosome(YAC) clone 248F5 (spans the breakpoint cluster region in band 5q31),/938G5 ( spans the breakpoint cluster region in 7q32), 912C3 (spans the breakpoint cluster region in 20ql2) and chromosome 8-specific centromeric a -satellite DNA probes. Results: (1). -5/5q-: Among 48 patients of MDS, 13 cases were positive by interphaseTISH, however, of whom, 7 cases were positive and another 6 cases were negative by CC. (2). -7/7q-: Among 48 patients with MDS, three cases displayed -7/7q- by CC and confirmed by interphase FISH. Six out of 45 cases who did not show -7/7q- by CC displayed 7q- by interphase FISH. (3). 20q-: Among 52 cases of MDS, 7 cases were positive by FISH, however, of whom, 4 cases were positive and another 3 cases were negative by CC. (4). Trisomy 8: Of 67 cases of MDS studied, 15 displayed trisomy 8 by interphase FISH and CC; 52 did not show trisomy 8 by CC, but interphase FISH revealed trisomy 8 in 8 of them. Conclusions: Interphase FISH is a very useful molecular cytogenetic tool in detecting common chromosome abnormalities such as -5/5q-, -7/7q-, +8 and 20q-in MDS. It is more sensitive than CC and is an important complement to CC.2. Demonstration of the constitution and origin of the centromere of the derivative chromosome resulting from the unbalanced translocation involving chromosome Iq in MDS by dual-color FISHThe rearrangements involving chromosome Iq is infrequently seen in MDS. Several types have been reported such as t(l;7), t(Y;l) and t(l;16). From January 1992 to May 2001, six cases of MDS patients with rearrangements involving Iq have been found in our hospital, including five t(l;7) (three cases have a long history of exposure to benzene), one t(l;ll). With the conventional banding technique, it is very difficult to identify which chromosome provides the centromere for the derivative chromosome. In order to confirm the constitution and origin of the centromere of the derivative chromosome, dual-color FISH using SpectrumRed and SpectrumGreen directly labeled...
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