Molecular biological study on new gene amplification mechanism, SJT, for malignant transformation in hematological malignancie.

应用FISH方法对135例白血病、淋巴瘤患者进行精确分析。我们发现了一种新的基因扩增机制——染色体片段跳跃易位（SJT），即染色体片段易位到染色体末端的几个部分。除了8个SJT区域（8q24、9q34、11q13、11q22-23、14q32-34、21q22、22q11）外，SKY-FISH分析还鉴定了另外7个区域，分别为1q22-23、2q22-25、3q24-27、5q22-32、7q23-25、16q22-23、20q21-22。FISH利用约10个cosmid和YAC探针鉴定了4个sjt的共同区域。8q24SJT和11q13SJT分别含有MYC和Cyclin D基因。位于SJT内的高表达基因将成为与恶性转化相关的候选基因。MYC基因在所有8q24SJT淋巴瘤中表达，但在部分白血病中不表达。Cyclin D1基因在所有白血病和淋巴瘤中表达。从髓系白血病细胞系OHN-GM中分离20个中期，用dopp - pcr扩增提取的dna。纯化后的dna作为FISH探针，应用FISH对2例患者进行间期细胞核预后观察。从SJT中分离的DNA片段与从同一细胞系中建立的c-DNA文库进行杂交。目前已鉴定出5-8个阳性克隆。在染色体进化过程中，SJT似乎是人类染色体形成的共同单位，在肿瘤转化后，它获得了几个染色体末端的转位。在化学和辐射引起的白血病中也发现了SJT。SJT将成为病原学试剂的靶区。

135 leukemia and lymphoma patients were precisely analyzed by FISH method. We found a new mechanism for gene amplification, chromosome segmental jumping translocation(SJT), in which chromosomal segment translocates to several portions of chromosomal end. Seven more regions, 1q22-23, 2q22-25, 3q24-27, 5q22-32, 7q23-25, 16q22-23, 20q21-22, were identified by present SKY-FISH analysis, in addition to eight SJT regions(8q24, 9q34, 11q13, 11q22-23, 14q32-34, 21q22, 22q11). Common regions within four SJTs were identified by FISH using about 10 cosmid and YAC probes. 8q24SJT and 11q13SJT contained MYC and Cyclin D gene, respectively. Highly expressed gene, locating within a SJT will be candidate genes for associating with malignant transformation. MYC gene expressed in all lymphoma with 8q24SJT, but not in some leukemias. Cyclin D1 gene expressed in all leukemias and lymphomas. Twenty metaphases obtained from a myeloid leukemia cell line, OHN-GM, were microdissected and extracted DNAs were amplified by DOP-PCR.These purified DNAs were used as FISH probes and FISH was applied to two patients for following observation of prognosis on interphase nucleus. DNA fragments microdissected from SJT were hybridized with c-DNA libraries established from same cell line. So far, 5-8 positive clones were identified. A SJT seemed to be a common unit for formation of human chromosome in chromosomal evolution and after neoplastic transformation it acquires transpotition to several chromosomal ends. Also SJT are found in chemical-and radiation-induced leukemias. SJT will be a target region for etiological agents.