Kennedy A R, Fox M, Murphy G, Little J B
Proc Natl Acad Sci U S A. 1980 Dec;77(12):7262-6. doi: 10.1073/pnas.77.12.7262.
The appearance of transformed foci after x-irradiation of the C3H 10T1/2 line of murine cells requires extensive proliferation followed by prolonged incubation under conditions of confluence. When the progeny of irradiated cells are resuspended and plated to determine the number of potential transformed foci, the absolute yield is constant over a wide range of dilutions and is similar to that observed in cultures that have not been resuspended. In addition, for cells exposed to a given x-ray dose, the number of transformed foci per dish is independent of the number of irradiated cells. These observations suggest that few, if any, of the transformed clones occur as a direct consequence of the x-ray exposure and challenge the hypothesis that transformed foci are the clonal products of occasional cells that have experienced an x-ray-induced mutational change. Rather, it appears that at least two steps are involved. We suggest that exposure to x-rays result in a change, for example, the induction or expression of some cell function, in many or all of the cells and that this change is transmitted to the progeny of the surviving cells; a consequence of this change is an enhanced probability of the occurrence of a second step, transformation, when these cells are maintained under conditions of confluence.
对小鼠C3H 10T1/2细胞系进行X射线照射后，转化灶的出现需要细胞大量增殖，随后在汇合条件下长时间孵育。当照射后细胞的子代重悬并接种以确定潜在转化灶的数量时，在很宽的稀释范围内绝对产量是恒定的，并且与未重悬的培养物中观察到的产量相似。此外，对于接受给定X射线剂量的细胞，每皿转化灶的数量与照射细胞的数量无关。这些观察结果表明，即使有，也很少有转化克隆是X射线照射的直接结果，这对转化灶是偶尔经历X射线诱导突变变化的细胞的克隆产物这一假设提出了挑战。相反，似乎至少涉及两个步骤。我们认为，X射线照射导致许多或所有细胞发生变化，例如某些细胞功能的诱导或表达，并且这种变化传递给存活细胞的子代；当这些细胞在汇合条件下维持时，这种变化的一个结果是发生第二步即转化的可能性增加。
