Fernandez-Pol J A, Hamilton P D, Klos D J
Cancer Res. 1982 Feb;42(2):609-17.
We have studied the effects of paraquat (methyl viologen), a herbicide that increases intracellular production of superoxide radical, on the viability of virus-transformed and nontransformed normal rat kidney (NRK) cells in culture. We have shown that a low concentration of paraquat (12.5 microM) is cytotoxic toward virus-transformed cell lines, including Kirsten sarcoma virus- and SV40-transformed NRK cells. The corresponding untransformed NRK cells were resistant to the same and a 4-fold higher concentration of paraquat. There was a good correlation between the susceptibility of transformed and untransformed cells to paraquat cytotoxicity and their ability to increase the superoxide dismutase (SOD) enzymatic activity. We found that paraquat is cytotoxic toward Kirsten sarcoma virus-transformed and SV40-transformed NRK cells which showed low intracellular SOD activity. The relationship between SOD activity and paraquat cytoxicity was strengthened by the finding that the tolerance of NRK cells to the drug was associated with high intracellular SOD activity. This report also describes the isolation of a revertant (revertant RE8G3) cell line derived from Kirsten sarcoma virus-transformed NRK cells after paraquat treatment which contains SOD activity at levels much higher than those found in NRK cells. This revertant is undistinguishable from NRK cells with respect to its lack of transformed cell properties. Not only are these cells normal morphologically but also they do not grow in soft agar, an in vitro property that closely correlates with in vivo tumorigenicity. Several biological and biochemical properties of RE8G3 cells, including growth characteristics, surface receptors for both transferrin and epidermal growth factor (EGF), and the EGF-dependent 32P phosphorylation of specific membrane polypeptides have been studied. The most interesting conclusion that can be drawn from these studies is that there is a correlation between loss of the transformed phenotype and an increase in both EGF receptors and EGF-dependent 32P phosphorylation of a m.w. 170,000 membrane-associated protein.
我们研究了百草枯（甲基紫精）对培养的病毒转化和未转化的正常大鼠肾（NRK）细胞活力的影响，百草枯是一种能增加细胞内超氧自由基生成的除草剂。我们发现低浓度的百草枯（12.5微摩尔）对病毒转化的细胞系具有细胞毒性，包括柯斯顿肉瘤病毒和SV40转化的NRK细胞。相应的未转化NRK细胞对相同浓度及4倍高浓度的百草枯具有抗性。转化和未转化细胞对百草枯细胞毒性的敏感性与其增加超氧化物歧化酶（SOD）酶活性的能力之间存在良好的相关性。我们发现百草枯对细胞内SOD活性较低的柯斯顿肉瘤病毒转化和SV40转化的NRK细胞具有细胞毒性。NRK细胞对该药物的耐受性与细胞内高SOD活性相关，这一发现进一步加强了SOD活性与百草枯细胞毒性之间的关系。本报告还描述了在百草枯处理后从柯斯顿肉瘤病毒转化的NRK细胞中分离出的一个回复突变细胞系（回复突变体RE8G3），其SOD活性水平远高于NRK细胞。该回复突变体在缺乏转化细胞特性方面与NRK细胞无法区分。这些细胞不仅形态正常，而且在软琼脂中不生长，软琼脂中的这种体外特性与体内致瘤性密切相关。我们研究了RE8G3细胞的几种生物学和生化特性，包括生长特性、转铁蛋白和表皮生长因子（EGF）的表面受体，以及特定膜多肽的EGF依赖性32P磷酸化。从这些研究中可以得出的最有趣的结论是，转化表型的丧失与EGF受体的增加以及分子量为170,000的膜相关蛋白依赖于EGF的32P磷酸化之间存在相关性。
