STUDIES OF ONCOGENE EXPRESSION DURING CELLULAR GROWTH AND DIFFERENTIATION

在BALB-MK上皮细胞系中研究原癌基因表达 表皮生长因子（EGF）刺激细胞增殖。 的 获得以下结果： C-fos表达：在静止期的细胞总RNA中检测不到C-fos 加入EGF之前 加入EGF后，c-fos表达 在刺激后一小时急剧上升到尖峰。 然后下降 在接下来的几个小时内迅速降低到低但可检测的水平。 C-myc表达：这些细胞表达组成性高水平的c-myc 当静止时。 当加入EGF时，c-myc的表达增加了4 - 10倍。 从两小时开始到八小时结束 后刺激。 然后，它稳步下降到稳态水平， 加入EGF之前 TPA的作用：发现肿瘤促进剂TPA模拟促有丝分裂因子， EGF的作用，并像EGF一样，刺激c-fos的一小时高峰 当在不存在EGF的情况下给予BALB-MK细胞时。 Ca++和c-fos表达：Ca++是终末信号， 分化的BALB-MK细胞，发现引起c-fos的下降， 表情

Proto-oncogene expression was studied in the BALB-MK epithelial cell line following mitogenic stimulation with epidermal growth factor (EGF). The following results were obtained: C-fos expression: C-fos is undetectable in total cellular RNA of quiescent cells prior to addition of EGF. After addition of EGF, c-fos expression rises sharply to a sharp peak, one hour post-stimulation. It then drops off rapidly to low but detectable levels within the next few hours. C-myc expression: These cells express constitutively high levels of c-myc when quiescent. When EGF is added, c-myc expression rises four- to eight-fold to a plateau beginning at two hours and ending at eight hours post-stimulation. It then steadily declines to steady-state levels higher than prior to addition of EGF. Effects of TPA: The tumor promoter TPA was found to mimic the mitogenic effects of EGF and, like EGF, to stimulate a sharp one-hour peak of c-fos when given to BALB-MK cells in the absence of EGF. Ca++ and c-fos expression: Ca++, which is a signal for terminal differentiation in BALB-MK cells, was found to cause a decline in c-fos expression.