[Study of the childhood acute lymphoblastic leukemia with t(12;21)].
OBJECTIVE
To explore the incidence, clinical characteristics and prognosis of childhood acute lymphoblastic leukemia (ALL) with t(12;21).


METHODS
t(12;21)/TEL-AML1 fusion gene was examined in bone marrow or peripheral blood mononuclear cells from 51 newly diagnosed childhood ALL patients by conventional cytogenetic R-banding analysis (CCA), dual colour interphase fluorescence in situ hybridization (I-FISH), and nested reverse transcriptase-polymerase chain reaction (RT-PCR).


RESULTS
t(12; 21)/TEL-AML1 fusion gene was found in 11 cases by FISH or PCR, accounting for 21.6% and 26.9% in childhood ALLs and in non-T lineage ALL cases, respectively. The median age at diagnosis was 6.8 (2.9 to 12) years. All of the t(12;21) patients expressed non-T lineage immunophenotype, and most of them were common-ALL. High myeloid antigen coexpression was not found. In 11 CCA cases, normal karyotype was found in 7, and a dubious t(12;21) in one. TEL allele deletion was found in 8 (72.7%) of t(12;21) positive cases by FISH. By comparison, no statistic difference was found in sex, anemia, hemorrhage, organ enlargement, and initial WBC count between the positive and negative non-T lineage ALLs, but the platelet count and the frequency of IgH gene rearrangement were much lower in positive cases (P = 0.008 and 0.007, respectively). Moreover, no difference was found in overall CR rate, CR rate within 4 weeks, CR duration and relapse rate between the two groups.


CONCLUSIONS
t(12;21) was the most common chromosomal translocation in childhood ALL, but not all of them could be detected by CCA. t(12;21) cases showed non-T cell immunotypes, most of them were CD(10)(+) ALL. TEL allele deletion was common in these cases. There was no significant difference in clinical characteristics and short term outcome between the t(12;21) and the TEL-AML1 negative cases. In our data, Chinese t(12;21) ALL showed older in age, lower BPC, lower IgH rearrangement frequency and more of normal karyotype as compared with the reports abroad.
Institute of Hematology and Blood Diseases Hospital, CAMS and PUMC, Tianjin 300020, China.
Dong
D
Lin
Shi-he
SH
Liu
Xiao-fan
XF
Zhu
Li-jin
LJ
Bo
Cheng-wen
CW
Li
Yu-mei
YM
Chen
Xu-ping
XP
Liu
Shuang
S
Qin
Yun
Y
Dai
Jian-xiang
JX
Wang
D002648:Child; D002675:Child, Preschool; D002881:Chromosomes, Human, Pair 12; D002891:Chromosomes, Human, Pair 21; D050676:Core Binding Factor Alpha 2 Subunit; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014178:Translocation, Genetic; D000097764:ETS Translocation Variant 6 Protein
D050676:Core Binding Factor Alpha 2 Subunit; D015514:Oncogene Proteins, Fusion; C102421:TEL-AML1 fusion protein; D000097764:ETS Translocation Variant 6 Protein