Xu F, Taki T, Yang H W, Hanada R, Hongo T, Ohnishi H, Kobayashi M, Bessho F, Yanagisawa M, Hayashi Y
Department of Paediatrics, Faculty of Medicine, University of Tokyo, Japan.
Br J Haematol. 1999 Apr;105(1):155-62.
We examined mRNA expression and internal tandem duplication of the Fms-like tyrosine kinase 3 (FLT3) gene in haematological malignancies by reverse transcriptase-polymerase chain reaction (RT-PCR) and genomic PCR followed by sequencing. By RT-PCR, expression of FLT3 was detected in 45/74 (61%) leukaemia cell lines and the frequency of expression of FLT3 was significantly higher in undifferentiated type (B-precursor acute lymphoblastic leukaemia; ALL) than in differentiated type cell lines (B-ALL) (P = 0.0076). Using the genomic PCR method, 194 fresh samples including 87 acute myeloid leukaemias, 60 ALLs, 32 myelodysplastic syndromes (MDSs) and 15 juvenile chronic myelogenous leukaemias (JCMLs) were examined. Tandem duplication was found in 12 (13.8%) AMLs and two (3.3%) ALLs. Sequence analyses of the 14 samples with the duplication revealed that eight showed a simple tandem duplication and six a tandem duplication with insertion. Most of these tandem duplications occurred within exon 11, and two duplications occurred from exon 11 to intron 11 and exon 12. No tandem duplications of FLT3 gene were detected in MDS or JCML. The frequency of tandem duplication of FLT3 gene in childhood AML was lower than that in adult AML so far reported. All of the 12 AML patients with the duplication died within 47 months after diagnosis, whereas two ALL patients with the duplication have survived 44 and 72 months, respectively. These two ALL patients expressed both lymphoid and myeloid antigens and were considered to have biphenotypic leukaemia. These results suggest that tandem duplication is involved in ALL in addition to AML, but not in childhood MDS or JCML, and that childhood AML patients with the tandem duplication have a poor prognosis.
我们通过逆转录聚合酶链反应（RT-PCR）和基因组PCR随后测序，检测血液系统恶性肿瘤中Fms样酪氨酸激酶3（FLT3）基因的mRNA表达和内部串联重复。通过RT-PCR，在45/74（61%）白血病细胞系中检测到FLT3表达，FLT3在未分化型（B前体急性淋巴细胞白血病；ALL）中的表达频率显著高于分化型细胞系（B-ALL）（P = 0.0076）。使用基因组PCR方法，检测了194份新鲜样本，包括87例急性髓系白血病、60例ALL、32例骨髓增生异常综合征（MDS）和15例幼年型慢性粒细胞白血病（JCML）。在12例（13.8%）急性髓系白血病和2例（3.3%）ALL中发现串联重复。对14份有重复的样本进行序列分析，发现8例为简单串联重复，6例为插入型串联重复。这些串联重复大多发生在外显子11内，2例重复发生在外显子11至内含子11和外显子12。在MDS或JCML中未检测到FLT3基因的串联重复。儿童急性髓系白血病中FLT3基因串联重复的频率低于迄今报道的成人急性髓系白血病。12例有重复的急性髓系白血病患者在诊断后47个月内全部死亡，而2例有重复的ALL患者分别存活了44个月和72个月。这2例ALL患者同时表达淋巴和髓系抗原，被认为患有双表型白血病。这些结果表明，串联重复除了在急性髓系白血病中起作用外，在ALL中也有涉及，但在儿童MDS或JCML中没有，并且有串联重复的儿童急性髓系白血病患者预后不良。
