Bouchard L, Vass-Marengo J, Bastin M
Virology. 1986 Nov;155(1):1-12. doi: 10.1016/0042-6822(86)90162-5.
As a step toward understanding the molecular mechanism of cooperation between viral and cellular genes in oncogenic transformation, we examined various properties of rat cells transfected with the polyomavirus transforming genes without selecting for a neoplastic phenotype. The cell lines displayed a phenotype ranging from nontumorigenic (flat) to fully transformed (tumorigenic). In the established FR3T3 cell line, acquisition of the fully transformed phenotype correlated with effective expression of the polyomavirus middle T (pmt) antigen. Flat cells carrying silent copies of pmt mutated spontaneously to the fully transformed state with a frequency of 2 to 6 X 10(-5) per cell per generation. In unestablished rat fibroblasts, simultaneous transfer of either pmt and small T or pmt and large T in the presence of the neo marker conferred only a partially transformed phenotype to most of the cell lines. The same results were obtained when wild-type genomic DNA was cotransfected with pSV2-neo. The flat transformants progressively acquired properties characteristic of fully transformed cells with passage in culture. However, in contrast to FR3T3 cells, the generation of fully transformed variants from the flat, unestablished fibroblasts was not caused by activation of pmt expression. This indicates that the functions conferred by the large and small T antigens, alone or in combination with each other, cannot substitute for all the functions expressed by the FR3T3 cell line as a result of in vitro establishment. Thus, polyomavirus-mediated transformation may require additional cellular alterations beyond the acquisition of the three viral oncogenes.
作为理解病毒基因与细胞基因在致癌转化中协同作用分子机制的一步，我们检测了转染多瘤病毒转化基因的大鼠细胞的各种特性，而未对肿瘤表型进行选择。这些细胞系表现出从非致瘤性（扁平）到完全转化（致瘤性）的一系列表型。在已建立的FR3T3细胞系中，完全转化表型的获得与多瘤病毒中T（pmt）抗原的有效表达相关。携带pmt沉默拷贝的扁平细胞以每代每细胞2至6×10⁻⁵的频率自发突变为完全转化状态。在未建立的大鼠成纤维细胞中，在neo标记存在的情况下同时转染pmt和小T或pmt和大T，仅使大多数细胞系呈现部分转化表型。当野生型基因组DNA与pSV2-neo共转染时，也得到了相同的结果。扁平转化体在培养传代过程中逐渐获得完全转化细胞的特征性特性。然而，与FR3T3细胞不同，未建立的扁平成纤维细胞产生完全转化变体并非由pmt表达的激活所致。这表明大T抗原和小T抗原单独或相互组合所赋予的功能，不能替代FR3T3细胞系因体外建立而表达的所有功能。因此，多瘤病毒介导的转化可能需要除获得三个病毒癌基因之外的其他细胞改变。
