Qian L, Gong J, Liu J, Broome J D, Koduru P R
Department of Laboratories, North Shore University Hospital, Manhasset, N.Y., USA.
Br J Haematol. 1999 Aug;106(2):477-85. doi: 10.1046/j.1365-2141.1999.01549.x.
In a unique case of chronic lymphocytic leukaemia (CLL) we performed a longitudinal cytogenetic and molecular genetic study of tumour cells from diagnosis through progression and transformation to non-Hodgkin's lymphoma (NHL) and lymphomatous meningitis. CLL cells at diagnosis had trisomy 12 and a t(14;19)(q32;q13.3). At relapse, the leukaemic cells had a subclone carrying a t(12;22)(p13;q11.2) in addition to the initial changes. We cloned reciprocal translocation junctions at the 22q11.2- chromosome and the 12p13+ chromosome and the corresponding germline DNA fragments. Restriction map analysis and nucleotide sequence analysis of the cloned DNA fragment from the 22q11.2- chromosome mapped the translocation break within the immunoglobulin (Ig)-lambda-C complex at the nt3889; nts 3890, 3891 were lost from the translocation site. A probe from the 3'-end of the clone derived from the 22q11.2- chromosome showed single copy hybridization which was different from the Ig-lambda probe. Nucleotide sequence analysis of the exact junction region and the corresponding germline DNA showed that the translocation at 12p13 occurred in the negative regulatory region of the cyclin D2 gene at the nt -1602, and a pentamer consisting of nts -1603 to -1599 was lost at the break site. We sequenced another 227 bp upstream of the known 5'-end of the promoter and did not find any open reading frame. From these results we hypothesize that, in this patient, the t(12;22) disrupted the negative regulator in the promoter of cyclin D2 which in turn might have deregulated cyclin D2.
在一例独特的慢性淋巴细胞白血病（CLL）病例中，我们对肿瘤细胞进行了纵向细胞遗传学和分子遗传学研究，研究范围从诊断开始，贯穿疾病进展、转化为非霍奇金淋巴瘤（NHL）以及淋巴瘤性脑膜炎阶段。诊断时的CLL细胞存在12号染色体三体以及t(14;19)(q32;q13.3)。复发时，白血病细胞除了最初的变化外，还出现了一个携带t(12;22)(p13;q11.2)的亚克隆。我们克隆了22号染色体q11.2-区域和12号染色体p13+区域的相互易位连接点以及相应的种系DNA片段。对来自22号染色体q11.2-区域的克隆DNA片段进行限制性图谱分析和核苷酸序列分析，将易位断点定位在免疫球蛋白（Ig）-λ-C复合体的nt3889处；nt3890、3891在易位位点处缺失。来自22号染色体q11.2-区域克隆的3'-末端探针显示单拷贝杂交，这与Ig-λ探针不同。对精确连接区域和相应种系DNA的核苷酸序列分析表明，12号染色体p13处的易位发生在细胞周期蛋白D2基因的负调控区域的nt -1602处，一个由nt -1603至-1599组成的五聚体在断点处缺失。我们对启动子已知5'-末端上游另外227 bp进行了测序，未发现任何开放阅读框。根据这些结果，我们推测，在该患者中，t(12;22)破坏了细胞周期蛋白D2启动子中的负调控因子，进而可能导致细胞周期蛋白D2失调。
