Chen P L, Chen Y, Shan B, Bookstein R, Lee W H
Center for Molecular Medicine, University of Texas Health Science Center, San Antonio 78245.
Cell Growth Differ. 1992 Feb;3(2):119-25.
Mutational inactivation of the retinoblastoma gene (RB) is an invariant feature of the childhood eye cancer retinoblastoma and of tumor cells derived therefrom. In a previous study, retrovirus-mediated transfer of wild-type RB into cultured retinoblastoma cells resulted in a marked enlargement and reduced growth rate of these cells, as well as loss of their tumorigenic properties in nude mice. It was therefore difficult to separate the proposed growth-suppressing and tumor-suppressing activities of RB protein. Here, we show that clones of RB-reconstituted retinoblastoma cells can be isolated that stably express apparently normal RB protein for at least 20 months of continuous culture. These clones were indistinguishable from nonreconstituted cells by multiple parameters including morphology, growth rate, and cell cycle distribution. Despite similar phenotypes in culture, clones with stable RB expression were uniformly nontumorigenic in nude mice, whereas those that lost such expression regained their tumorigenic properties. These results indicate that the tumorigenicity of these cells is entirely determined by the presence or absence of exogenous RB protein expression and that suppression of tumorigenicity is distinct from inhibition of cellular growth in culture.
视网膜母细胞瘤基因（RB）的突变失活是儿童眼癌视网膜母细胞瘤以及由此衍生的肿瘤细胞的一个不变特征。在先前的一项研究中，通过逆转录病毒介导将野生型RB导入培养的视网膜母细胞瘤细胞，导致这些细胞显著增大且生长速率降低，同时在裸鼠中丧失了致瘤特性。因此，很难区分RB蛋白所提出的生长抑制和肿瘤抑制活性。在此，我们表明可以分离出RB重组视网膜母细胞瘤细胞的克隆，这些克隆在连续培养至少20个月的时间里能稳定表达明显正常的RB蛋白。通过包括形态、生长速率和细胞周期分布在内的多个参数，这些克隆与未重组细胞没有区别。尽管在培养中表现出相似的表型，但稳定表达RB的克隆在裸鼠中均无致瘤性，而那些失去这种表达的克隆则恢复了其致瘤特性。这些结果表明，这些细胞的致瘤性完全由外源性RB蛋白表达的有无决定，并且肿瘤发生抑制与培养中细胞生长的抑制是不同的。
