Arita I, Fujimori A, Takebe H, Tatsumi K
Department of Molecular Oncology, Faculty of Medicine, Kyoto University, Japan.
Carcinogenesis. 1990 Oct;11(10):1733-8. doi: 10.1093/carcin/11.10.1733.
A series of human lymphoblastoid cell lines (LCLs) called Mex- were defined by Sklar and Strauss on the basis of their inability to remove O6-methylguanine from DNA. Instability of Mex- has previously been shown as a population phenotype of LCLs. We examined whether Mex- as a cellular phenotype is spontaneously convertible or not. At the population doubling number (PDN) 23 after recloning, two out of 15 independent subcultures derived from a Mex- LCL, AT1-1, were found to contain a small fraction of Mex+ cells after treatment with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU). Three Mex+ subclones were identified without exposure to ACNU among 486 subclones from replica plating of an expanded Mex- clone (PDN30). The rate of spontaneous conversion was estimated to be in the range of 10(-8)-10(-7) per cell per generation by the fluctuation analyses on two Mex- subclones. These results strongly support the hypothesis that Mex- as a cellular phenotype is spontaneously convertible to Mex+.
斯克拉和施特劳斯基于无法从DNA中去除O6-甲基鸟嘌呤这一特性定义了一系列名为Mex-的人类淋巴母细胞系（LCLs）。Mex-的不稳定性先前已被证明是LCLs的群体表型。我们研究了Mex-作为一种细胞表型是否能自发转变。在重新克隆后的群体倍增数（PDN）为23时，在用1-(4-氨基-2-甲基-5-嘧啶基)甲基-3-(2-氯乙基)-3-亚硝基脲（ACNU）处理后，从Mex-LCL AT1-1衍生的15个独立亚培养物中有两个被发现含有一小部分Mex+细胞。在一个扩增的Mex-克隆（PDN30）的复制平板培养得到的486个亚克隆中，未经ACNU处理鉴定出了三个Mex+亚克隆。通过对两个Mex-亚克隆的波动分析，估计自发转变率为每细胞每代10(-8)-10(-7)。这些结果有力地支持了以下假设：Mex-作为一种细胞表型可自发转变为Mex+。
