Induction of numerical chromosome changes and neoplastic transformation by radiations.

以Gloden仓鼠胚胎(Ghe)细胞为研究对象，研究了X射线和紫外线对细胞染色体变化和肿瘤转化的诱导作用。经X射线或紫外线照射后的细胞在传代后出现形态变化，并在软琼脂中形成集落。与这些变化相反的是，在裸鼠体内观察到致瘤性的获得要晚得多(照射后11代)。当在X射线照射后的不同传代制备甲烷染色体时，根据传代次数的不同，在细胞中可以检测到一到两条额外的染色体。例如，第5代有45条染色体的细胞几乎都含有7号染色体的三体，13代细胞在第6、9和/或20号染色体上有进一步的染色体数目变化。在锚定非依赖细胞和紫外线诱导的致瘤细胞中也观察到了类似的染色体变化。将不同转化的GHE细胞的DNA导入小鼠NIH3T3细胞后，发现NIH3T3细胞呈现恶性表型。Southern印迹分析发现，所有肿瘤来源的恶性NIH3T3细胞均含有一定量的金黄地鼠DNA，提示GHE细胞的辐射转化是一个多步骤的过程，特定染色体的数目变化和某些癌基因的激活可能在每种转化表型的表达中起重要作用。

Using gloden hamster embryo (GHE) cells, we examined the induction of chromosome changes and neoplastic transformation by X-rays or ultraviolet litht (UV).Unirradiated cells were grown at a constant growth rate for 7 passages but later ceased to divide. X-ray- or UV-irradiated cells escaped from senescence ans showed morphological transformation accompanying with the expression of the ability to form colonies in soft agar medium at later passages. In contrast to these changes, the aquisition of tumorigenicity in nude mice was observed much later (11 passages after the irradiation). When methaphese chromosomes were prepared at various passages after X-irradiation, one or two additional chromosomes were detected in the cells depending on passage numbers. For example, almost all the cells showing 45 chromosomes at passage 5 contained trisomy of chromosome 7 and the cells transferred for 13 passages had futher numerical chromosome changes on chromosome 6,9 and/or 20. Similar chromosome changes were observed in anchorage-independent and tumorigenic cells induced by UV. Mouse NIH3T3 cells transfected with DNA from various transformed GHE cells expressed malignant phenotypes. From Southern blot analysis, all malignant NIH3T3 cells derived from tumors after transfection were found to contain some amount of golden hamster DNA.These results suggest that radiation induced transformation is a multistep in GHE cells, and that the numerical change of specific chromosomes and the activation of some oncogenes may play an important role for the expression of each transformed phenotypes.