OBJECTIVETo study the clinical and laboratory features of childhood acute leukemia (AL) with MLL gene rearrangements.

METHODSSixteen of 298 cases of childhood AL with MLL rearrangements were studied by using MLL dual-color FISH, multiplex RT-PCR with 13 pairs of primers in combination with R banding karyotype analysis and cell immunophenotyping by flow cytometry.

RESULTSSixteen cases of childhood AL with MLL rearrangements accounted for 5.4% of 298 AL patients, and 56.3% of infant ALs. Among 106 cases analyzed by multiplex RT-PCR, MLL gene rearrangements were found in 11 cases, including MLL/AF4 fusion gene in 2, MLL/AF6 fusion gene in 1, MLL/AF6 and MLL/ELL combined with MLL/ AFX or HOX11 in one case each, MLL/AF9 in 2, MLL/AF10 in 1, MLL/ELL in 2. MLL partial tandem duplication in 1 and activated HOX11 in 1. In 27 cases assayed by FISH, 9 cases (36.0%) were demonstrated MLL gene rearrangements. In 16 patients with MLL gene rearrangements, 14 (87.5%) exhibited clonal chromosome abnormalities involved chromosome 11 in 11 cases: being t(4;11) in 2, t(6;11), t(8;11), t(7;8;11), t(9;11) in each trisomy 11 in 2 and 11q--in 3 cases. Among these 16 patients, 11 were B-ALL, and 5 AML-M5, 3 of the latter were CD7+ and CD2+. Of these 16 patients, 8 received chemotherapy and 7 of them achieved complete remission, while the other 8 patients gave up treatment.

CONCLUSIONMultiplex RT-PCR combined with FISH provided a more accurate and sensitive method for detection of MLL gene rearrangements. Finding out MLL gene rearrangement is of most importance in guiding therapy and predicting prognosis in childhood AL.