Fiona Watkins

Gene expression profiling in the myelodysplastic syndromes using cDNA microarray technology

The myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal disorders of the haematopoietic stem cell and primarily involve cells of the myeloid lineage. Using cDNA microarrays comprising 6000 human genes, we studied the gene expression profiles in the neutrophils of 21 MDS patients, seven of which had the 5q‐ syndrome, and two acute myeloid leukaemia (AML) patients when compared with the neutrophils from pooled healthy controls. Data analysis showed a high level of heterogeneity of gene expression between MDS patients, most probably reflecting the underlying karyotypic and genetic heterogeneity. Nevertheless, several genes were commonly up or down‐regulated in MDS. The most up‐regulated genes included RAB20, ARG1, ZNF183 and ACPL. The RAB20 gene is a member of the Ras gene superfamily and ARG1 promotes cellular proliferation. The most down‐regulated genes include COX2, CD18, FOS and IL7R. COX2 is anti‐apoptotic and promotes cell survival. Many genes were identified that are differentially expressed in the different MDS subtypes and AML. A subset of genes was able to discriminate patients with the 5q‐ syndrome from patients with refractory anaemia and a normal karyotype. The microarray expression results for several genes were confirmed by real‐time quantitative polymerase chain reaction. The MDS‐specific expression changes identified are likely to be biologically important in the pathophysiology of this disorder.

Telomere length shortening is associated with disease evolution in chronic myelogenous leukemia.

We studied telomere length in the peripheral blood leukocyte samples of a large group of patients with chronic myelogenous leukemia (CML) by Southern blot hybridization using the (TTAGGG)4 probe. The average telomere length expressed as the peak telomere repeat array (TRA) of the peripheral blood samples obtained from a group of 34 healthy age‐matched controls ranged between 7.6 and 10.0 kb and the mean peak TRA was 8.7 kb. Forty‐one patients in the chronic phase of CML were studied; 32/41 (78%) showed telomere reduction (<7.6 kb) relative to age‐matched controls and the mean peak TRA was 6.4 kb (range 4.0–10.6 kb). Serial samples were analysed from 12 patients at both chronic phase and during disease progression. The leukocyte DNA of all 12 patients in accelerated phase and/or blast crisis showed telomere reduction relative to age‐matched controls and the mean peak TRA was 4.1 kb (range 3.0–5.4 kb). The peak TRA in the accelerated or blast phase was reduced compared with the corresponding paired sample in the chronic phase in all cases studied. These data show that a marked reduction in telomere length is associated with disease progression in CML. Am. J. Hematol. 61:5–9, 1999.

Low expression of the putative tumour suppressor gene gravin in chronic myeloid leukaemia, myelodysplastic syndromes and acute myeloid leukaemia.

The putative tumour suppressor gene gravin is down‐regulated in several solid tumours and is implicated in tumorigenesis. We have evaluated the expression levels of the gravin gene in the CD34+/blast cells of a range of myeloid malignancies as compared with controls using real‐time quantitative polymerase chain reaction (PCR). Gravin was markedly down‐regulated in 41 of 41 patients with acute myeloid leukaemia (AML), nine of 10 patients with myelodysplastic syndromes (MDS) and 33 of 33 patients with chronic myeloid leukaemia (CML), of whom 24 were in blast crisis (BC). We have shown that gravin is consistently down‐regulated in the CD34+/blast cells of myeloid malignancies and may play a role in the molecular pathogenesis of these disorders.