[Study on clinical and biological characteristics of childhood acute leukemia with MLL gene rearrangements].

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

Methods: Sixteen 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.

Results: Sixteen 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.

Conclusion: Multiplex 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.