Tarone G, Ceschi P, Prat M, Comoglio P M
Cancer Res. 1981 Sep;41(9 Pt 1):3648-52.
The [35S]methionine-labeled proteins released in the medium conditioned by normal and transformed mouse fibroblasts have been analyzed by sodium dodecyl sulfate-polyacrylamide electrophoresis. Three major proteins, fibronectin, procollagens, and a protein with a molecular weight of 45,000 (45K protein) have been identified. The 45K protein, which has not yet been described, accounts for about 30% of the proteins released by control 3T3 fibroblasts or mouse embryo cultures. Quantitation of the radioactivity incorporated by the 45K protein indicated a 10- to 15-fold decrease in 3T3 fibroblasts transformed by Kirsten, Abelson, or Rous sarcoma viruses. The amounts of fibronectin and procollagens released in the medium by transformed cells were also reduced by factors of 3- and 5-fold, respectively. Pulse chase experiments have shown that the decreased level of the 45K protein in the medium of transformed cells cannot be explained by a reduced rate of secretion or by extracellular proteolytic degradation. It is not known, however, whether decreased synthesis is responsible for this alteration. The "tumor promoter" phorbol myristate acetate, which is known to induce many of the alterations associated with neoplastic cells, also induced 3T3 fibroblasts to release the 45K protein in amounts comparable to that of transformed cells. Thus, this protein represents a new molecular marker of oncoviral transformation.
通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析了由正常和转化的小鼠成纤维细胞条件培养基中释放的[35S]甲硫氨酸标记的蛋白质。已鉴定出三种主要蛋白质，纤连蛋白、前胶原和一种分子量为45000的蛋白质（45K蛋白质）。尚未描述的45K蛋白质约占对照3T3成纤维细胞或小鼠胚胎培养物释放蛋白质的30%。对45K蛋白质掺入放射性的定量分析表明，经 Kirsten、Abelson 或劳氏肉瘤病毒转化的3T3成纤维细胞中该蛋白质减少了10至15倍。转化细胞在培养基中释放的纤连蛋白和前胶原的量也分别减少了3倍和5倍。脉冲追踪实验表明，转化细胞培养基中45K蛋白质水平的降低不能用分泌速率降低或细胞外蛋白水解降解来解释。然而，尚不清楚合成减少是否是这种改变的原因。已知能诱导许多与肿瘤细胞相关改变的“肿瘤促进剂”佛波酯肉豆蔻酸酯乙酸盐，也能诱导3T3成纤维细胞释放与转化细胞相当量的45K蛋白质。因此，这种蛋白质代表了一种新的肿瘤病毒转化分子标志物。
