伴有t(3;5)(q25;q34)的骨髓增生异常综合征急性髓系白血病变患者的分子特征

Molecular characterization of t(3;5)(q25;q34) in a case of acute myeloid leukemia secondary to myelodysplastic syndromes

目的研究t(3;5)(q25;q34)的分子特征。方法R显带染色体核型分析和染色体涂染分析确定t(3;5)(q25;q34)存在。RT-PCR法检测患者NPM-MLF1融合基因、MLF1基因表达。PCR联合序列分析检测NPM基因突变。实时定量RT-PCR(Real-time PCR)检测Evi-1,MDS1／Evi-1表达。免疫组化染色确定MLF1和NPM-MLF1蛋白细胞定位分布。Western blot法检测bcl-2蛋白表达。结果染色体核型分析和涂染分析均证实存在染色体t(3;5)(q25;q34),NPM-MLF1融合基因阳性,经诱导治疗获得完全缓解后转为阴性。患者白血病细胞仅表达MLF1基因非编码蛋白剪接体,不表达Evi-1基因,弱表达MDS1／Evi-1。无NPM基因突变,未检出bcl-2蛋白表达。MLF1蛋白定位于细胞质,而NPM-MLF1则主要定位于胞核。结论t(3;5)(q25;q34)是髓系肿瘤的一种少见的染色体易位,该染色体易位导致形成NPM-MLF1融合基因是其发病的分子学基础。

Objective To identify the molecular characteristics of t（3;5） （q25;q34） chromosome translocation in a case of acute myeloid leukemia（AML） secondary to myelodysplastic syndromes （MDS）. Methods Karyotype analysis was performed by R banding technique and chromosome painting with whole chromosome 3 and 5 painting probes. The expression of NPM-MLF1 fusion gene and MLF1 gene were detected by reverse transcription polymerase chain reaction （RT-PCR）. NPM gene mutation was analyzed by PCR combined with sequencing. The Evi-1 and MDS1/ Evi-1 genes expression were examined by fluorescent Realtime PCR. The subcellular localizations of wild type MLF1 and NPM-MLF1 proteins were determined by immunohistochemistry, and bcl-2 proteins by Western blot. Results t （3 ;5 ） （ q5 ; q34） was confirmed by both R banding and chromosome painting, NPM-MLF1 fusion gene was positive and became negative in chemotherapy induced CR. The non-coding alternative splicing transcript of MLF1 gene were detected in the patient＇ s leukemic cells. Evi-1 gene was negative and MDS1/Evi-1 expression was dim. No mutation was found in NPM gene, and bcl-2 protein was negative. The wild type MLF1 protein was localized in the cytoplasm, whereas the NPM-MLF1 fusion protein mainly in the nucleus. Condusion t（3 ;5 ） （ q5 ; q34） is a rare nonrandom chromosome abnormality in myeloid malignancies, NPM-MLF1 fusion gene is the molecular basis in the pathogenesis of this type malignancies.