Deletion of 5q31 is observed in megakaryocytic cells in patients with myelodysplastic syndromes and a del(5q), including the 5q- syndrome

Clonal origin and evolution of myelodysplastic syndrome analyzed by dysplastic morphology and fluorescence in situ hybridization

Myelodysplastic syndromes (MDS) are clonal disorders of hematopoietic stem/progenitor cells. As bone marrow cells are extremely diverse in these disorders, the origin and evolution of MDS clones are difficult to identify and trace. Cellular dysplasia is a distinct morphologic feature; however, whether the dysplastic cells represent abnormal clones or only nonspecific superficial phenomena remains to be clarified. To address this question, 97 patients were examined for dysplasia features, among them bone marrow slides of 16 patients with chromosomal abnormalities were subjected to fluorescence in situ hybridization (FISH) to determine the karyotype of these dysplastic cells. Furthermore, the emerging frequencies of abnormal karyotypes in various differentiated stages of each lineage were also evaluated by a combination of morphological evaluation and FISH karyotyping. Our results indicate that the overall percentage of dysplastic cells does not differ significantly among the WHO subtypes, while the megakaryoid lineage presents the most frequent dysplasia in all subtypes. A positive correlation between dysplastic cells and FISH-detectable abnormal clones was observed, but the dysplastic morphology was not a specific feature of FISH-detectable abnormal clones. FISH-detectable abnormal clones can differentiate into mature granulocytes and erythrocytes, in coexistence with cells originating from the normal clones.

Clinical management of myelodysplastic syndromes with interstitial deletion of chromosome 5q

Deletions of the long (q) arm of chromosome 5 [del(5q)]occur in patients with myelodysplastic syndromes (MDS) including, but not limited to, those who meet the WHO definition of the 5q- syndrome. Del(5q) MDS patients frequently have symptomatic anemia, and its treatment has traditionally consisted of RBC transfusions and, for some, iron chelation therapy. Erythropoietin, darbepoetin, hypomethylating agents, and lenalidomide can enhance erythropoiesis in MDS patients with anemia, increasing hemoglobin levels and abrogating RBC transfusion requirements. Lenalidomide is particularly active in treating the anemia of del(5q) MDS, which is especially relevant given the low response rate to erythropoietin in this group of patients. In a recent study of 43 MDS patients, 10 of 12 patients (83%) with del(5q) MDS achieved sustained RBC transfusion independence (or a > 2 g/dL increase in hemoglobin), compared with 57% of those with a normal karyotype and 12% of those with other karyotypic abnormalities. Complete cytogenetic remissions were achieved in 75% (nine of 12) of the del(5q) MDS patients, suggesting that lenalidomide targets a fundamental pathogenetic feature of MDS that is more pronounced in the presence of chromosomal 5q deletions. This review highlights some issues about the classification and treatment of del(5q) MDS.

Fluorescence in situ hybridization for the study of cell lineage involvement in myelodysplastic syndromes with chromosome 5 anomalies

Fluorescence in situ hybridization (FISH) with a locus-specific dual DNA probe (LSI EGR-1SO/D5S23SG) for chromosome 5 was used in combination with morphology to study bone marrow cell lineage involvement of the abnormal chromosomal clone in 13 patients with deletion 5q [del(5q)], either as a sole aberration or as part of a complex karyotype, and in six cases with monosomy 5 by metaphase cytogenetics, all with complex karyotypes including 2-6 marker chromosomes. In the monosomy 5 group, only one case displayed the expected one orange and one green (1O + 1G) FISH pattern in a majority of the cells. The other five patients instead showed 1O + 2G FISH signals in 17-86% of the bone marrow cells, which is the typical pattern for del(5q). In the del(5q) group, 26-98% of the bone marrow cells exhibited 1O + 2G FISH signals. All patients showed clonal involvement of the myeloid cell lineages, including the megakaryocytes in a few cases, whereas lymphoid cells generally exhibited the normal 2O + 2G FISH pattern. No difference was seen between patients with 5q- syndrome, those with del(5q) and a complex karyotype, and the monosomy 5 group. We were thus unable to confirm the recent suggestion that B-cells are a part of the abnormal clone in MDS with del(5q). Furthermore, true monosomy 5 seems to be rare in MDS.

Molecular cytogenetics

Refinements in cytogenetic techniques over the past 30 years have allowed the increasingly sensitive detection of chromosome abnormalities in haematological malignancies. In particular, the advent of fluorescence in situ hybridization techniques has provided significant advances in both diagnosis and research of leukaemias. The application of new multicolour karyotyping techniques has allowed the complete dissection of complex chromosome rearrangements and provides the prospect of identifying new recurrent chromosome rearrangements. Both comparative genomic hybridization and interphase fluorescence in situ hybridization avoid the use of metaphase chromosomes altogether and have allowed the genetic analysis of previously intractable targets. Recent developments in comparative genomic hybridization to DNA microarrays provide the promise of high resolution and automated screening for chromosomal imbalances. Rather than replacing conventional cytogenetics, however, these techniques have extended the range of cytogenetic analyses when applied in a complementary fashion.