Clinical and molecular biologic characteristics of childhood acute leukemia with mixed lineage leukemia gene rearrangement

Objective To analyze the frequency of mixed lineage leukemia (MLL) gene rearrangement, the frequent types of fusion genes and clinical characteristics of childhood acute leukemia (AL) with MLL gene rearrangement. Methods Morphological and molecular characteristics of 87 AL patients with MLL gene rearrangement were studied and analyzed.MLL fusion gene was detected by way of reverse transcription polymerase chain reaction (RT-PCR). Results Eighty-seven cases with MLL gene rearrangement were found in 1209 AL patients with incidence of 6.41% and 9.36% respectively in ALL and in acute myelocytic leukemia (AML) respectively.Fifty-eight cases of ALL were all B-ALL, 28 cases of AML included 17 cases of M5, 5 cases of M4, 4 cases of M2, 1 case of M3 and 1 case of M6.While there was 1 case of mixed of lineage leukemia and myeloid and T-lymphoblastic antigen presentation.The clonal chromosomal aberration was detected in 45 out of 76 cases(59.21%), and chromosome 11q23 aberration were observed in 28 cases(36.84%). There were 7 different kinds of fusion genes, including MLL-AF9 in 25 cases, dupMLL in 25 cases, MLL-AF4 in 17 cases, MLL-AF10 in 9 cases, MLL-ENL in 8 cases, MLL-AF1q in 2 cases, and MLL-AF6 in 1 case.Among the cases of MLL-AF4, MLL-AF9, MLL-AF10, MLL-ENL and dupMLL, there were statistical differences in lineage, age and initial white blood cell count (WBC) (all P<0.05). Conclusions In childhood AL with MLL gene rearrangement, B-ALL is more common in ALL, whereas M5 and M4 are more common in AML.The common types of fusion genes are dupMLL, MLL-AF9 and MLL-AF4.Patients with the different kinds of MLL fusion gene may present different clinical characteristics. The most common ALL cases are those with MLL/AF4 and MLL/ENL who may be younger with higher WBC than the others. Key words: Leukemia, acute; Mixed lingeage leukemia; Fusion gene; Nested reverse transcription polymerase chain reaction; Child