Zhou Y, Li J, Xu K, Hu S X, Benedict W F, Xu H J
Center for Biotechnology, Baylor College of Medicine, The Woodlands, TX 77381.
Proc Natl Acad Sci U S A. 1994 May 10;91(10):4165-9. doi: 10.1073/pnas.91.10.4165.
We have transfected the osteosarcoma cell line Saos2 and the bladder carcinoma cell line 5637 with additional retinoblastoma (RB) expression plasmids. The RB-reconstituted Saos2 and 5637 cells showed only slightly lower ratios of cells undergoing DNA synthesis compared to their parental RB- tumor cells, and there were no noticeable changes in cell morphology. Furthermore, we have isolated long-term RB+ clones from Saos2, 5637, and the retinoblastoma cell line WERI-Rb27 after transfection/transduction with a RB expression plasmid or retrovirus. These clones were similar to their parental cell lines in terms of morphology and growth rates, and they all expressed functional RB protein (p110RB) as evidenced by its potential of phosphorylation, simian virus 40 large tumor antigen binding, and nuclear tethering. No mutation or deletion of the exogenous RB gene was detectable by PCR and single-strand conformation polymorphism analysis. In addition, either the individual or pooled RB+ clones did form malignant tumors in nude mice but usually with a longer latency period and lower frequency. Such tumors also retained normal RB expression, suggesting that at least a portion of the RB-reconstituted tumor cells were still tumorigenic. This phenomenon is referred to by us as tumor suppressor resistance (TSR).
我们用额外的视网膜母细胞瘤（RB）表达质粒转染了骨肉瘤细胞系Saos2和膀胱癌细胞系5637。与它们的亲代RB-肿瘤细胞相比，RB重组的Saos2和5637细胞中进行DNA合成的细胞比例仅略低，并且细胞形态没有明显变化。此外，在用RB表达质粒或逆转录病毒转染/转导后，我们从Saos2、5637和视网膜母细胞瘤细胞系WERI-Rb27中分离出了长期RB+克隆。这些克隆在形态和生长速率方面与其亲代细胞系相似，并且它们都表达功能性RB蛋白（p110RB），这通过其磷酸化潜力、猿猴病毒40大肿瘤抗原结合和核束缚得到证明。通过PCR和单链构象多态性分析未检测到外源性RB基因的突变或缺失。此外，单个或合并的RB+克隆在裸鼠中确实形成了恶性肿瘤，但通常潜伏期更长且频率更低。此类肿瘤也保留了正常的RB表达，表明至少一部分RB重组的肿瘤细胞仍具有致瘤性。我们将这种现象称为肿瘤抑制抗性（TSR）。
