Gierthy J F, Lincoln D W, Roth K E, Bowser S S, Bennett J A, Bradley L, Dickerman H W
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
J Cell Biochem. 1991 Feb;45(2):177-87. doi: 10.1002/jcb.240450209.
Foci, nodules of cellular overgrowth, that appear after confluence are an in vitro characteristic of malignant transformation. A well-studied in vitro model of estrogen-dependent tumors is the MCF-7 cell line, derived from a pleural metastasis of a human breast adenocarcinoma. We report that cultivation of MCF-7 cells, using routine methods, results in extensive estrogen-stimulated postconfluent cell accumulation characterized by discrete three-dimensional arrays. Side view Nomarski optical sections revealed these to be principally multicellular foci with occasional domes and pseudoacinar vacuoles. This effect on MCF-7 cell growth occurs in media containing fetal bovine serum but not with calf serum or charcoal-dextran-treated fetal bovine serum unless supplemented with estrogens. Foci formation starts 5-6 days after confluence, and the number of foci generated is a function of the concentration of added estrogens. Foci formation is suppressed by the antiestrogens Tamoxifen and LY 156758. Addition of progesterone, testosterone, or dexamethasone had little or no effect, while various estrogens (ethinyl estradiol, diethylstilbestrol, and moxestrol) induced foci development. Clones derived from single cells of the initial MCF-7 population revealed a wide variance in estrogen-induced foci formation, demonstrating heterogeneity of this tumor cell line. The postconfluent cell growth of the estrogen receptor-deficient cell line, MDA-MB-231, contrasted with MCF-7 by developing an extensive multilayer morphology devoid of discrete structures. The tumorigenic potential of the MCF-7 cells used in our experiments was confirmed by their estrogen-dependent growth in immunosuppressed male BDF1 mice. These data suggest an estrogen receptor-based mechanism for the development of multicellular foci during postconfluent growth of MCF-7 cells. After confluence, foci, in contrast to the quiescent surrounding monolayer, retain proliferating cells. Focus formation, therefore, reflects the heterogeneous responsiveness of these cells to estrogens and should provide a model permitting in vitro comparisons between the progenitor cells of multicellular foci and the monolayer population.
汇合后出现的细胞过度生长灶、结节是恶性转化的体外特征。雌激素依赖性肿瘤的一个经过充分研究的体外模型是MCF-7细胞系，它源自一名人类乳腺腺癌的胸膜转移灶。我们报告，使用常规方法培养MCF-7细胞会导致广泛的雌激素刺激的汇合后细胞积累，其特征为离散的三维阵列。侧面的诺马斯基光学切片显示，这些主要是多细胞灶，偶尔有穹顶和假腺泡空泡。这种对MCF-7细胞生长的影响发生在含有胎牛血清的培养基中，但在含有小牛血清或经活性炭-葡聚糖处理的胎牛血清的培养基中不会发生，除非补充雌激素。灶形成在汇合后5-6天开始，产生的灶数量是添加雌激素浓度的函数。抗雌激素他莫昔芬和LY 156758可抑制灶形成。添加孕酮、睾酮或地塞米松几乎没有影响，而各种雌激素（炔雌醇、己烯雌酚和莫昔芬）可诱导灶形成。源自初始MCF-7群体单细胞的克隆显示，雌激素诱导的灶形成存在很大差异，表明该肿瘤细胞系具有异质性。雌激素受体缺陷细胞系MDA-MB-231的汇合后细胞生长与MCF-7形成对比，它形成了广泛的多层形态，没有离散结构。我们实验中使用的MCF-7细胞的致瘤潜力通过其在免疫抑制雄性BDF1小鼠中的雌激素依赖性生长得到证实。这些数据表明，在MCF-7细胞汇合后生长过程中，多细胞灶的形成存在基于雌激素受体的机制。汇合后，与静止的周围单层细胞相比，灶保留了增殖细胞。因此，灶形成反映了这些细胞对雌激素的异质反应性，应该提供一个模型，允许对多细胞灶的祖细胞和单层细胞群体进行体外比较。
