[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.
Lin
Dong
D
Institute of Hematology and Blood Diseases Hospital, CAMS and PUMC, Tianjin 300020, China.
Liu
Shi-he
SH
Zhu
Xiao-fan
XF
Bo
Li-jin
LJ
Li
Cheng-wen
CW
Chen
Yu-mei
YM
Liu
Xu-ping
XP
Qin
Shuang
S
Dai
Yun
Y
Wang
Jian-xiang
JX
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