Submicroscopic deletions in 5q- associated malignancies.

BACKGROUND AND OBJECTIVES The deletion of the long arm of chromosome 5 is common in myelodysplastic syndromes (MDS) but is not limited to the 5q- syndrome as it is also seen in acute myeloid leukemia (AML), where it is often associated with other karyotypic aberrations. The aim of this study was to investigate whether deletions of known suppressor sequences occur in myeloid malignancies associated with 5q-. DESIGN AND METHODS Thirty patients with MDS or AML were selected for the presence of a 5q karyotypic deletion, either isolated (19 cases) or associated with other chromosome changes (11 cases). Multiple fluorescent in situ hybridization (FISH) in interphase nuclei was applied in all cases using a panel of eleven probes for known suppressor genes or loci deleted in MDS/AML. Metaphase FISH was also performed to clarify discrepancies between conventional and molecular cytogenetics. RESULTS No additional deletions were found in nineteen cases with an isolated 5q-. Mono-allelic deletions where found in 9/11 cases, 3 of which were related to monosomies by conventional cytogenetics. Interphase-FISH showed p53, AML1, D13S25, NF1, or Ikaros in six out of nine (66%) patients with 5q- and additional karyotypic changes. Metaphase FISH was helpful in assigning some of these cryptic events to non-proliferating cells. INTERPRETATION AND CONCLUSIONS Our study emphasizes that isolated 5q- is the marker of a highly stable clone in both MDS and AML. AML with isolated 5q- are molecularly closer to 5q- syndrome than to AML with complex changes. Interphase-FISH data strongly support a mutator phenotype underlying complex karyotypes with a 5q deletion.