Wolff J, Wong C, Cheng H, Poyet P, Butel J S, Rosen J M
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030-3498.
Exp Cell Res. 1992 Sep;202(1):67-76. doi: 10.1016/0014-4827(92)90405-w.
To study the effect of SV40 T-antigen in mammary epithelial cells, a rat beta-casein promoter-driven SV40 early-region construct was stably introduced into the clonal mouse mammary epithelial cell line HC11. With the expression of the viral T-antigens under the control of a hormone-inducible promoter, it was possible to dissociate the effects of different levels of T-antigen expression on cell growth, morphology, and gene expression. Following hormonal induction, a rapid but transient induction of T-antigen was observed, followed by a delayed induction of H4 histone mRNA. In T-antigen-positive HC11 cells cultured in the absence of EGF, the expression of basal levels of T-antigen (in the absence of hormonal induction) led to a decreased doubling time and an increased cell density. In the presence of EGF, T-antigen expression resulted additionally in an altered cell morphology. Despite the effects of T-antigen on cell growth and gene expression, the cells were unable to form colonies in soft agar and were nontumorigenic when transplanted into cleared mammary fat pads. They were, however, weakly tumorigenic in nude mice. Relatively high levels of p53 protein synthesis were observed in both the transfected HC11 cells and the parental COMMA-D cells, as compared to 3T3E fibroblasts and another mammary epithelial cell line. The HC11 and COMMA-D cells synthesized approximately equal levels of wild-type and mutated p53 proteins as defined by their reactivities with monoclonal antibodies PAb246 and PAb240, respectively. Interactions between excess p53 and T-antigen may, in part, explain the failure of these cells to display a completely transformed phenotype.
为了研究猿猴病毒40（SV40）T抗原在乳腺上皮细胞中的作用，将大鼠β-酪蛋白启动子驱动的SV40早期区域构建体稳定导入克隆小鼠乳腺上皮细胞系HC11。由于病毒T抗原在激素诱导型启动子的控制下表达，因此可以区分不同水平的T抗原表达对细胞生长、形态和基因表达的影响。激素诱导后，观察到T抗原迅速但短暂的诱导，随后是H4组蛋白mRNA的延迟诱导。在无表皮生长因子（EGF）培养的T抗原阳性HC11细胞中，基础水平的T抗原表达（无激素诱导时）导致倍增时间缩短和细胞密度增加。在有EGF存在的情况下，T抗原表达还导致细胞形态改变。尽管T抗原对细胞生长和基因表达有影响，但这些细胞在软琼脂中无法形成集落，移植到清除的乳腺脂肪垫中也不具有致瘤性。然而，它们在裸鼠中具有弱致瘤性。与3T3E成纤维细胞和另一个乳腺上皮细胞系相比，在转染的HC11细胞和亲本COMMA-D细胞中均观察到相对高水平的p53蛋白合成。根据HC11和COMMA-D细胞分别与单克隆抗体PAb246和PAb240的反应性来定义，它们合成的野生型和突变型p53蛋白水平大致相等。过量的p53与T抗原之间的相互作用可能部分解释了这些细胞未能表现出完全转化表型的原因。
