Zhang X, Wang T, Batist G, Tsao M S
Department of Pathology, Montreal General Hospital, Quebec, Canada.
Cancer Res. 1994 Dec 1;54(23):6122-8.
The neoplastic transformation of cultured rat liver epithelial cells by various means has consistently been associated with the development of resistance to the mito-inhibitory effect of transforming growth factor beta (TGF-beta), suggesting that such phenotype plays a mechanistic role during the transformation of these cells. We have studied the induction of the "TGF-beta-resistant" phenotype in a clonal strain of early passage WB-F344 normal cultured rat liver epithelial cells, the proliferation of which was markedly inhibited by TGF-beta. The control WB cells in continuous culture slowly developed TGF-beta resistance. However, when the same cells were exposed to step-wise increases of TGF-beta concentration in their culture medium, the development of TGF-beta resistance was accelerated. Cells which had been grown in medium containing 1 ng/ml TGF-beta developed colony-forming capacity in soft agar containing epidermal growth factor. Cells which were grown in media containing 5 and 10 ng/ml TGF-beta demonstrated a low level of colony-forming efficiency in soft agar medium without added epidermal growth factor and tumorigenicity in isogeneic rats. These TGF-beta-resistant cells also exhibited progressively increasing levels of expression of the c-fos and and myc mRNA, and increased resistance to the cytotoxicity of Adriamycin and melphalan. The latter phenomenon was accompanied by an increase in the mdr-1 mRNA expression, cellular glutathione level, and glutathione S-transferase activity. The results suggest that chronic exposure to high concentration of TGF-beta promotes the spontaneous neoplastic transformation of cultured rat liver epithelial cells, and that this process may represent one of the mechanisms of cellular adaptation for induction of the multidrug-resistant phenotype during the carcinogenesis of epithelial cells.
通过各种方式对培养的大鼠肝上皮细胞进行肿瘤转化，一直与对转化生长因子β（TGF-β）的线粒体抑制作用产生抗性相关，这表明这种表型在这些细胞的转化过程中发挥着机制性作用。我们研究了在早期传代的WB-F344正常培养大鼠肝上皮细胞的克隆株中“TGF-β抗性”表型的诱导情况，该细胞株的增殖受到TGF-β的显著抑制。持续培养的对照WB细胞缓慢产生TGF-β抗性。然而，当相同细胞在培养基中逐步增加TGF-β浓度时，TGF-β抗性的产生加速。在含有1 ng/ml TGF-β的培养基中生长的细胞在含有表皮生长因子的软琼脂中发展出集落形成能力。在含有5和10 ng/ml TGF-β的培养基中生长的细胞在未添加表皮生长因子的软琼脂培养基中表现出低水平的集落形成效率，并在同基因大鼠中具有致瘤性。这些TGF-β抗性细胞还表现出c-fos和myc mRNA表达水平逐渐增加，以及对阿霉素和马法兰细胞毒性的抗性增加。后一种现象伴随着mdr-1 mRNA表达、细胞谷胱甘肽水平和谷胱甘肽S-转移酶活性的增加。结果表明，长期暴露于高浓度的TGF-β促进培养的大鼠肝上皮细胞的自发肿瘤转化，并且这个过程可能代表上皮细胞癌变过程中诱导多药耐药表型的细胞适应机制之一。
