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Chromosomal Aberration of the 11q23 Locus in Acute Leukemia and Frequency of MLL Gene Translocation
Results in 378 Adult Patients

M. Christina Cox MD, PhD, Paola Panetta, Francesco Lo-Coco MD, Giovanni Del Poeta MD, Adriano Venditti MD, PhD, Luca Maurillo MD, PhD, M. Ilaria Del Principe MD, PhD, Alessandro Mauriello MD, Lucia Anemona MD, PhD, Antonio Bruno, Carla Mazzone MD, Paolo Palombo MD, Sergio Amadori MD, PhD
DOI: http://dx.doi.org/10.1309/RX27R8GJQM330C22 298-306 First published online: 1 August 2004

Abstract

Structural abnormality of the 11q23 band (11q23+) bearing the MLL gene translocation (MLL+) is a recurrent chromosome change observed in 3% to 7% of acute lymphoblastic leukemias and in 3% to 4% of acute myeloblastic leukemias. The resolution of conventional cytogenetics (CC) in detecting 11q23 rearrangement is limited when the translocative partner has a telomeric location; furthermore, CC can barely discriminate between true 11q23+/MLL+ and rearrangements clustering within the 11q22~25 region without MLL involvement (MLL–). We characterized a series of 378 consecutive patients with adult acute leukemia by using CC, fluorescence in situ hybridization (FISH), and multiplex karyotyping (M-FISH) analysis. Our aim was to define the frequency of cryptic MLL+ cases and the frequency of MLL+ within 11q22~25+ cases. As expected, FISH was more sensitive than CC in detecting MLL+ cases, but rather unexpectedly, 9 (45%) of 20 patients with 11q22~25+ were MLL–. A better characterization of 11q22~25+/MLL– leukemias is relevant for the identification of new, recurrent translocations. Moreover, these cases should be readily distinguishable from 11q23+/MLL+ cases. We recommend that karyotypic analysis always be complemented by molecular or FISH methods to unravel MLL rearrangements.

Key Words:
  • MLL
  • 11q23
  • AML
  • Acute myeloblastic leukemia
  • ALL
  • Acute lymphoblastic leukemia
  • AL
  • Acute leukemia
  • Chromosomal aberrations
  • FISH
  • Fluorescence in situ hybridization
  • 11q22~25