Martens I, Nilsson M, Magnusson G, Linder S
Department of Medical Virology, Uppsala University Biomedical Centre, Sweden.
Proc Natl Acad Sci U S A. 1988 Aug;85(15):5571-5. doi: 10.1073/pnas.85.15.5571.
The addition of glucocorticoids to the growth medium could substitute for the expression of the polyomavirus large tumor antigen in the transformation of rat fibroblasts in vitro. After transfection with a large tumor antigen-deficient mutant of polyomavirus, pbc1051, high-frequency permanent transformation was observed, if the cells were grown in medium containing dexamethasone. Growth of pbc1051-transfected rat fibroblasts was strictly dependent on the presence of glucocorticoids during the initial phase of transformation. In the second phase, the growth of pbc1051-transfected cells was stimulated by dexamethasone, but the hormone was not essential for growth. After approximately 10 weeks in culture, pbc1051-transfected cells had progressed to hormone independent growth. Rat embryo cells transfected with wild-type polyomavirus DNA had the second phase in which growth was stimulated by glucocorticoid, and after this phase growth was steroid independent. Addition of glucocorticoids to rat fibroblasts transfected with a plasmid encoding only the middle-sized tumor antigen resulted in only a weak stimulation of growth. In contrast, embryo cells transfected with a plasmid containing the human homologue of the cellular T24 Ha-ras gene linked to murine sarcoma virus and simian virus 40 enhancers could be efficiently established as cell lines in medium supplemented with glucocorticoids. The data suggest that, in the transformation of primary rodent cells by polyomavirus, the activity of large tumor antigen can be substituted for by stimulating normal cellular functions with dexamethasone.
在生长培养基中添加糖皮质激素可替代多瘤病毒大肿瘤抗原在体外转化大鼠成纤维细胞中的表达。用多瘤病毒的大肿瘤抗原缺陷型突变体pbc1051转染后，如果细胞在含有地塞米松的培养基中生长，可观察到高频永久性转化。在转化的初始阶段，pbc1051转染的大鼠成纤维细胞的生长严格依赖于糖皮质激素的存在。在第二阶段，地塞米松刺激pbc1051转染细胞的生长，但该激素对生长并非必不可少。培养约10周后，pbc1051转染细胞已发展为激素非依赖性生长。用野生型多瘤病毒DNA转染的大鼠胚胎细胞有第二阶段，其中糖皮质激素刺激生长，在此阶段之后生长不依赖于类固醇。向仅编码中等大小肿瘤抗原的质粒转染的大鼠成纤维细胞中添加糖皮质激素仅导致生长的微弱刺激。相比之下，用含有与鼠肉瘤病毒和猿猴病毒40增强子相连的细胞T24 Ha-ras基因的人同源物的质粒转染的胚胎细胞可在补充有糖皮质激素的培养基中有效地建立为细胞系。数据表明，在多瘤病毒对原代啮齿动物细胞的转化中，大肿瘤抗原的活性可通过用地塞米松刺激正常细胞功能来替代。
