Stoika Rostyslav, Yakymovych Mariya, Souchelnytskyi Serhiy, Yakymovych Ihor
Department of Regulation of Cell Proliferation, Institute of Cell Biology, National Academy of Sciences of Ukraine, Drahomanov Str. 14/16, 79005 Lviv, Ukraine.
Acta Biochim Pol. 2003;50(2):497-508.
Acquired drug resistance of tumor cells is frequently observed in cancer patients undergoing chemotherapy. We studied murine leukemia L1210 cells sensitive and resistant to the cytotoxic action of cisplatin and showed that cisplatin-resistant leukemia cells were also refractory to TGF beta1-dependent growth inhibition and apoptosis. Addressing the question about the mechanisms responsible for the cross-resistance to cisplatin and TGF beta1, we found that cisplatin- and TGF beta1-resistant L1210 cells possessed a decreased expression of type I TGF beta1 receptor, while the expression of type II TGF beta1 receptor was not affected. Western blot analysis of Smad proteins 2, 3, 4, 6, and 7, which participate in signal transduction pathway down-stream of the TGF beta1 receptors, revealed an increased expression of Smad 6, inhibiting TGF beta1 action, only in cisplatin- and TGF beta1-resistant L1210 cells. TGF beta1 and especially the cytotoxic mistletoe agglutinin increased Smad 6 expression in TGF beta1-sensitive but not in TGF beta1-resistant L1210 cells. TGF beta1-resistant L1210 cells also differed from TGF beta1-sensitive cells by the lack of expression of the pro-apoptotic p53 protein and higher level of expression of the anti-apoptotic Bcl-2 protein. Thus, the described co-expression of tumor cell refractoriness to an anti-cancer drug and to the inhibitory cytokine TGF beta1 is accompanied by multiple changes in the TGF beta1 signal transduction pathway and in other regulatory systems of the target cells. Besides, we found that various anti-tumor drugs and cytotoxic plant lectins increased the level of TGF beta1 expression in both TGFbeta1-sensitive and -resistant L1210 cells. A hypothesis is proposed that TGFbeta1 can at least partly mediate the effect of cell-stressing agents and, thus, the development of TGF beta1 resistance may be responsible for the appearance of tumor cell refractoriness to the action of some anti-cancer drugs.
在接受化疗的癌症患者中，肿瘤细胞获得性耐药现象屡见不鲜。我们研究了对顺铂细胞毒性作用敏感和耐药的小鼠白血病L1210细胞，结果显示，顺铂耐药的白血病细胞对转化生长因子β1（TGFβ1）依赖性生长抑制和凋亡也具有抗性。针对顺铂和TGFβ1交叉耐药的机制问题，我们发现，顺铂和TGFβ1耐药的L1210细胞中I型TGFβ1受体表达降低，而II型TGFβ1受体的表达未受影响。对参与TGFβ1受体下游信号转导通路的Smad蛋白2、3、4、6和7进行蛋白质印迹分析发现，只有在顺铂和TGFβ1耐药的L1210细胞中，抑制TGFβ1作用的Smad 6表达增加。TGFβ1尤其是细胞毒性槲寄生凝集素可增加TGFβ1敏感而非耐药的L1210细胞中Smad 6的表达。TGFβ1耐药的L1210细胞与TGFβ1敏感细胞的不同之处还在于，前者缺乏促凋亡p53蛋白的表达，而抗凋亡Bcl-2蛋白的表达水平较高。因此，肿瘤细胞对抗癌药物和抑制性细胞因子TGFβ1的难治性共同表达伴随着TGFβ1信号转导通路及靶细胞其他调节系统的多种变化。此外，我们发现，各种抗肿瘤药物和细胞毒性植物凝集素均可增加TGFβ1敏感和耐药L1210细胞中TGFβ1的表达水平。我们提出一个假说，即TGFβ1至少可以部分介导细胞应激剂的作用，因此，TGFβ1耐药的产生可能是肿瘤细胞对某些抗癌药物作用产生难治性的原因。
