Paquette B, Little J B
Harvard School of Public Health, Laboratory of Radiobiology, Boston, Massachusetts 02115.
Cancer Res. 1994 Jun 15;54(12):3173-8.
The level of genomic instability was determined during tumor development in vivo. Genomic rearrangements, a marker of genomic instability, was measured in mouse C3H/10T1/2 cells transformed in vitro by X-rays with a DNA fingerprinting assay. Three transformed clones isolated from type III foci were divided into two groups. Cells from the first group were injected s.c. into syngeneic and nonimmunosuppressed C3H mice. After 3 to 5 months, the tumors were excised, and the neoplastic cells were isolated and subcloned. Cells from the second group were incubated in vitro for 25 passages (about 6 months) to approximate the number of cell divisions occurring in the tumor, and then they were subcloned. DNA was extracted from subclones grown in vitro and in vivo and analyzed with the DNA fingerprinting assay. A high frequency of genomic rearrangements (50-100%) was found in subclones derived from tumors that arose in vivo, whereas the frequency was very low (< 10%) among subclones passaged in vitro, suggesting that genetic instability may be enhanced by factors present in the C3H mouse. In one clone (F-17) genomic instability appeared to be activated and down regulated. The high frequency of instability found in tumor cell subclones did not appear to result from an in vivo selection of a more tumorigenic subpopulation of cells present in the original clone prior to injection in the animal. This enhancement of genomic instability occurring in vivo could be required to complete the process of transformation to tumorigenicity and allow the neoplastic cells to adapt to a new environment.
在体内肿瘤发生过程中测定基因组不稳定性水平。基因组重排是基因组不稳定性的一个标志物，通过DNA指纹分析测定经X射线体外转化的小鼠C3H/10T1/2细胞中的基因组重排。从III型灶分离出的三个转化克隆分为两组。第一组细胞皮下注射到同基因且未免疫抑制的C3H小鼠体内。3至5个月后，切除肿瘤，分离肿瘤细胞并进行亚克隆。第二组细胞在体外培养25代（约6个月）以接近肿瘤中发生的细胞分裂次数，然后进行亚克隆。从体外和体内生长的亚克隆中提取DNA，并用DNA指纹分析进行分析。在源自体内产生的肿瘤的亚克隆中发现高频率的基因组重排（50 - 100%），而在体外传代的亚克隆中频率非常低（<10%），这表明C3H小鼠中存在的因素可能会增强遗传不稳定性。在一个克隆（F - 17）中，基因组不稳定性似乎被激活并下调。在肿瘤细胞亚克隆中发现的高频率不稳定性似乎不是由于在将原始克隆中的细胞注射到动物体内之前对更具致瘤性的亚群进行体内选择所致。体内发生的这种基因组不稳定性增强可能是完成向致瘤性转化过程并使肿瘤细胞适应新环境所必需的。
