Schwartz Jeffrey L, Jordan Robert, Evans Helen H, Lenarczyk Marek, Liber Howard L
Department of Radiation Oncology, University of Washington, 1959 NE Pacific, Box 356069, Seattle, WA 98195, USA.
Mutagenesis. 2004 Nov;19(6):477-82. doi: 10.1093/mutage/geh060.
Induced genomic instability in the human B lymphoblastoid cell line TK6 manifests itself as increases in end-to-end chromosome fusions and non-reciprocal chromosome translocations. It is not associated with elevated frequencies of specific locus mutations or other cytogenetic alterations. Previous studies on a limited number of cells and end-points suggested that induced instability in TK6 mirrors spontaneous instability in terms of the types of alterations observed. In the present study we expanded on our previous analysis to include more cells and more end-points in order to derive a more precise measure of spontaneous instability in TK6 cells. The frequency of normal growth rate thymidine kinase mutants (TK(-/-)), measured in 44 independently isolated clones, was 2.73 +/- 0.78 x 10(-6)/cell, while that for slow growth mutants was 2.39 +/- 0.52 x 10(-6)/cell. These are similar to the frequencies observed for HPRT mutants in primary human cells. There was wide variation in chromatid break frequencies, but the average break frequency, at 0.04+/-0.01 breaks/cell, was only slightly higher than that reported for primary human cells. In contrast, the dicentric frequency of 0.006/cell was more than 10-fold higher for TK6 cells than that reported for normal primary human cells. Furthermore, the dicentrics in TK6 cells are unusual in that they are the result of end-to-end chromosome fusions. TK6 cells also show much higher levels of non-reciprocal chromosome translocations than are usually observed in primary human cells. The results suggest an inherent instability in TK6 cells that differs from what is observed in primary cells in that it affects the frequency of end-to-end chromosome fusions and non-reciprocal chromosome translocations, but not TK gene mutations or other cytogenetic alterations.
在人B淋巴母细胞系TK6中诱导产生的基因组不稳定表现为端到端染色体融合和非相互染色体易位增加。它与特定基因座突变或其他细胞遗传学改变的频率升高无关。先前对有限数量的细胞和终点的研究表明，TK6中诱导的不稳定性在观察到的改变类型方面反映了自发不稳定性。在本研究中，我们扩展了先前的分析，纳入了更多的细胞和更多的终点，以便更精确地测量TK6细胞中的自发不稳定性。在44个独立分离的克隆中测量的正常生长速率胸苷激酶突变体（TK(-/-)）的频率为2.73 +/- 0.78 x 10(-6)/细胞，而慢生长突变体的频率为2.39 +/- 0.52 x 10(-6)/细胞。这些与原代人细胞中HPRT突变体观察到的频率相似。染色单体断裂频率存在广泛差异，但平均断裂频率为0.04 +/- 0.01断裂/细胞，仅略高于原代人细胞报道的频率。相比之下，TK6细胞的双着丝粒频率为0.006/细胞，比正常原代人细胞报道的频率高10倍以上。此外，TK6细胞中的双着丝粒不同寻常，因为它们是端到端染色体融合的结果。TK6细胞还表现出比原代人细胞中通常观察到的更高水平的非相互染色体易位。结果表明，TK6细胞中存在一种固有的不稳定性，与原代细胞中观察到的不同，它影响端到端染色体融合和非相互染色体易位的频率，但不影响TK基因突变或其他细胞遗传学改变。
