MLL amplification in myeloid leukemias: A study of 14 cases with multiple copies of 11q23

We here report the clinical, cytogenetic, fluorescence in situ hybridizatio n (FISH), and Southern blot data on 14 patients with a myeloid malignancy a nd structural aberration of chromosome band 11q23 associated with overrepre sentation or amplification of the MLL gene. The number of copies of MLL var ied from three (two cases) to a cluster consisting of multiple hybridizatio n spots. Together with previous reports, available data indicate that ampli fication of 11q23/MLL is a recurrent genetic change in myeloid malignancy. It affects mainly elderly patients and is often associated with dysplastic bone marrow changes or with complex karyotypic aberrations, suggestive of g enotoxic exposure. It is associated with a poor prognosis. In addition, FIS H analysis of nine cases with additional 11q probes showed that the overrep resented chromosomal region is generally not restricted to MLL, and Souther n blot analysis indicated that amplification does not involve a rearranged copy of this gene. The significance of MLL amplification and the mechanisms by which it could play a role in leukemogenesis and/or disease progression remain to be elucidated. Genes Chromosomes Cancer 29:40-47, 2000. (C) 2000 Wiley-Liss, Inc.