Uphoff C C, MacLeod R A, Denkmann S A, Golub T R, Borkhardt A, Janssen J W, Drexler H G
German Collection of Microorganisms and Cell Cultures, Department of Human and Animal Cell Cultures, Braunschweig, Germany.
Leukemia. 1997 Mar;11(3):441-7. doi: 10.1038/sj.leu.2400571.
The recurrent (12;21)(p13;q22) translocation fuses the two genes TEL and AML1 that have previously been cloned from translocation breakpoints in myeloid leukemias. Using mainly reverse transcriptase-polymerase chain reaction (RT-PCR), the TEL-AML1 chimeric transcript has been observed in 22-27% of pediatric patients with acute lymphoblastic leukemia (ALL), in particular in the early B-lineage ALL subtype, making it the most common genetic lesion in these patients. The vast majority of acute myeloid leukemias, other ALL subtypes and even adults with early B-lineage ALL were TEL-AML1-negative. We determined whether the TEL-AML1 fusion gene can also be observed in continuous human leukemia cell lines with an early B-lineage phenotype. Twenty-nine such cell lines established from children (n = 13) or adults (n = 13) with early B-lineage ALL and five cell lines derived from chronic myeloid leukemia in blast crisis or B cell non-Hodgkin's lymphoma were investigated for the occurrence of the TEL-AML1 rearrangement by RT-PCR. While all 13 adult early B-lineage ALL cell lines and the five cell lines from other leukemias or lymphomas were negative, 1/13 pediatric cell lines (cell line REH) was found to be positive for TEL-AML1; though neither reciprocal AML1-TEL, nor normal TEL, mRNA was detectable by RT-PCR in this cell line. These findings agreed with the results of conventional cytogenetic and FISH analysis of REH which was found to carry the der(21) partner only of t(12;21)(p13;q22), probably resulting from a complex translocation, t(4;12;21;16)(q32;p13;q22;q24.3). Hybridization with flanking cosmid clones (179A6 and 148B6), covering exons 1 and 8 respectively of TEL, confirmed a rearrangement accompanying the t(12;21), and showed cryptic deletion of the residual allele resulting from an apparently reciprocal t(5;12)(q31;p13). These findings in REH provide a further example of, and possible cytogenetic mechanism for, the paradigm of TEL-AML1 fusion accompanied by deletion of the residual TEL allele. The low rate of early B-lineage ALL cell lines carrying this translocation contrasts clearly with the relative high frequency of TEL-AML1-positive cases in primary material. It is possible that expression of the fusion product hampers the in vitro growth and establishment in culture of such leukemic cells. Nevertheless, the cell line REH represents a powerful tool for the further molecular characterization of this unique breakpoint and can serve as a positive control in routine PCR reactions.
复发性(12;21)(p13;q22)易位使两个基因TEL和AML1融合，这两个基因先前已从髓系白血病的易位断点处克隆得到。主要使用逆转录聚合酶链反应（RT-PCR），在22% - 27%的小儿急性淋巴细胞白血病（ALL）患者中观察到了TEL-AML1嵌合转录本，尤其是在早期B系ALL亚型中，这使其成为这些患者中最常见的基因病变。绝大多数急性髓系白血病、其他ALL亚型甚至患有早期B系ALL的成人都是TEL-AML1阴性。我们确定了在具有早期B系表型的连续人白血病细胞系中是否也能观察到TEL-AML1融合基因。通过RT-PCR研究了从患有早期B系ALL的儿童（n = 13）或成人（n = 13）建立的29个此类细胞系以及从急变期慢性髓系白血病或B细胞非霍奇金淋巴瘤衍生的5个细胞系中TEL-AML1重排的发生情况。虽然所有13个成人早期B系ALL细胞系以及来自其他白血病或淋巴瘤的5个细胞系均为阴性，但发现1/13的小儿细胞系（REH细胞系）TEL-AML1呈阳性；尽管在该细胞系中通过RT-PCR检测不到相互的AML1-TEL以及正常的TEL mRNA。这些发现与REH细胞系的传统细胞遗传学和FISH分析结果一致，发现该细胞系仅携带t(12;21)(p13;q22)的der(21)伙伴，可能是由复杂易位t(4;12;21;16)(q32;p13;q22;q24.3)导致的。与分别覆盖TEL外显子1和8的侧翼黏粒克隆（179A6和148B6）杂交，证实了伴随t(12;21)的重排，并显示出由于明显的相互t(5;12)(q31;p13)导致的残留等位基因的隐匿性缺失。REH细胞系中的这些发现为TEL-AML1融合并伴随残留TEL等位基因缺失的范例提供了进一步的实例及可能的细胞遗传学机制。携带这种易位的早期B系ALL细胞系比例较低，这与原发性材料中TEL-AML1阳性病例的相对高频率形成了鲜明对比。融合产物的表达可能会阻碍此类白血病细胞在体外的生长和培养。然而，REH细胞系是对这个独特断点进行进一步分子特征分析的有力工具，并且可作为常规PCR反应中的阳性对照。
