Weise A, Liehr T, Efferth T, Kuechler A, Gebhart E
Institute of Human Genetics and Anthropology, Friedrich Schiller University, Jena, Germany.
Cytogenet Genome Res. 2002;98(2-3):118-25. doi: 10.1159/000069808.
Cell lines of human T-cell acute lymphoblastic leukemias (T-ALL) have gained high interest for study of mechanisms of cytostatic drug resistance. However, they should also be suited to examine the validity and reliability of molecular cytogenetic techniques in detecting genomic alterations in neoplastic cells. Therefore, comparative genomic hybridization (CGH) and 24-color-fluorescence-in-situ-hybridization (M-FISH) were applied to eight sublines of CCRF-CEM leukemia cells selected in vitro for drug resistance and to their drug-sensitive parental counterparts. All cell lines were characterized by altered chromosome numbers and by a variety of chromosomal structural aberrations as shown by M-FISH. The great majority of anomalies detected by this technique were confirmed by CGH. Interestingly, a considerable number of the rearrangements found were imbalanced. Amplifications of 5q13 in the six methotrexate-resistant cell lines, a del(9)(p21pter) in all lines examined, and a gain of chromosome 20 in 9 of the 10 lines examined were readily detected by both techniques. The same held true for losses of chromosomes 17 and 18 in the near tetraploid cell lines which could also be confirmed by CGH. Some imbalances of genomic material detected by CGH were, however, not observed by means of M-FISH, possibly due to the limited extension of the corresponding chromosomal segment involved or the small subpopulation of cells affected. On the other hand, reciprocal translocations, balanced isochromosomes, and small deletions remained mainly undetected by CGH. A comparison of chromosomal alterations in drug-resistant and parental cell lines showed not only amplifications of chromosomal segments harboring well-known drug resistance genes, e.g., the dihydrofolate reductase gene, but also chromosomal changes which may involve novel genes associated with drug resistance. Thus, the present study has clearly unveiled the strengths and weaknesses of both techniques which can excellently complement each other. Their combination allowed a distinct improvement of the definition of the complex karyotypes of drug-resistant cell lines.
人类T细胞急性淋巴细胞白血病（T-ALL）细胞系在细胞生长抑制药物耐药机制研究中备受关注。然而，它们也应适用于检验分子细胞遗传学技术在检测肿瘤细胞基因组改变方面的有效性和可靠性。因此，我们将比较基因组杂交（CGH）和24色荧光原位杂交（M-FISH）应用于体外筛选出的8个CCRF-CEM白血病耐药细胞亚系及其药物敏感的亲本细胞系。如M-FISH所示，所有细胞系均表现出染色体数目改变和多种染色体结构畸变。该技术检测到的绝大多数异常均得到CGH的证实。有趣的是，发现的相当一部分重排是不平衡的。两种技术均能轻易检测到6个耐甲氨蝶呤细胞系中5q13的扩增、所有检测细胞系中的del(9)(p21pter)以及10个检测细胞系中9个细胞系的20号染色体增加。近四倍体细胞系中17号和18号染色体的缺失情况同样如此，CGH也能证实这一点。然而，CGH检测到的一些基因组物质不平衡情况，通过M-FISH未观察到，这可能是由于相关染色体片段延伸有限或受影响细胞亚群较小。另一方面，相互易位、平衡等臂染色体和小缺失主要未被CGH检测到。耐药细胞系和亲本细胞系染色体改变的比较表明，不仅存在携带已知耐药基因（如二氢叶酸还原酶基因）的染色体片段扩增，还存在可能涉及与耐药相关新基因的染色体变化。因此，本研究清楚地揭示了两种技术的优缺点，它们可相互完美补充。两者结合显著改善了耐药细胞系复杂核型的定义。
