Scheltema J M, Romijn J C, van Steenbrugge G J, Schröder F H, Mickisch G H
Department of Urology, Erasmus University and Academic Hospital, Rotterdam, The Netherlands.
Anticancer Res. 2001 Sep-Oct;21(5):3161-6.
Renal Cell Carcinomas (RCCs) exhibit strong resistance to the most chemotherapeutic treatments probably due to the expression of various multidrug resistance (MDR) genes. Overexpression of P-glycoprotein (Pgp) is established as one such factor, but other mechanisms such as at-MDR, characterized by attenuated DNA-topoisomerase II (topoII) activity, may be functional as well. In addition, regulating proteins involved in apoptosis can exhibit multidrug resistant features. However, prevention of apoptosis as a mechanism of MDR has not yet been assessed in RCC, nor has the cytotoxicity of a variety of chemotherapeutic agents known to trigger apoptotic or necrotic cell death been tested in RCC in a systematic fashion. Using immunohistochemistry and Western blotting, Bcl-2 and Bax expression was determined in a panel of multidrug resistant RCC lines featuring Pgp and/or at-MDR. The results were related to apoptotic activity and kind of cell death in these cell lines, demonstrated by incubation with Hoechst 33342 and propidium iodide after treatment with various cytotoxic agents and quantitated by MTT. In the drug resistant sublines, some decreased Bax and strongly increased Bcl-2 expression was seen by immunohistochemistry indicating prevention of apoptosis as a distinct feature of MDR in RCC. This was confirmed by Western blotting. Sublines revealed significant resistance for all drugs, except for CC-313 and DiMIQ. However, these drugs induced necrotic cell death, in contrast to all other drugs tested, which induced apoptotic cell death. We conclude that, in chemoselected RCC sublines, multidrug resistance appears to be functional due to inhibition of apoptosis, apart from the MDR1 and at-MDR resistance mechanisms. CC-313 and DiMIQ are very potent cytotoxic agents in RCC, probably because they do not kill by induction of apoptosis.
肾细胞癌（RCCs）对大多数化疗治疗表现出很强的抗性，这可能是由于多种多药耐药（MDR）基因的表达所致。P-糖蛋白（Pgp）的过表达被认为是其中一个因素，但其他机制，如以DNA拓扑异构酶II（拓扑异构酶II）活性减弱为特征的非典型MDR，也可能起作用。此外，参与细胞凋亡的调节蛋白也可能表现出多药耐药特征。然而，尚未在RCC中评估细胞凋亡抑制作为MDR机制的情况，也未系统地测试过已知能引发凋亡或坏死性细胞死亡的多种化疗药物在RCC中的细胞毒性。利用免疫组织化学和蛋白质印迹法，在一组具有Pgp和/或非典型MDR的多药耐药RCC细胞系中测定了Bcl-2和Bax的表达。将结果与这些细胞系中的凋亡活性和细胞死亡类型相关联，这些细胞系在用各种细胞毒性药物处理后，通过与Hoechst 33342和碘化丙啶孵育来证明，并通过MTT进行定量分析。在耐药亚系中，免疫组织化学显示一些细胞系的Bax表达降低，Bcl-2表达强烈增加，表明细胞凋亡抑制是RCC中MDR的一个明显特征。蛋白质印迹法证实了这一点。亚系对所有药物均表现出显著抗性，但对CC-313和DiMIQ除外。然而，与所有其他测试药物诱导凋亡性细胞死亡不同，这些药物诱导坏死性细胞死亡。我们得出结论，在化学选择的RCC亚系中，除了MDR1和非典型MDR耐药机制外，多药耐药似乎是由于细胞凋亡抑制而起作用。CC-313和DiMIQ是RCC中非常有效的细胞毒性药物，可能是因为它们不是通过诱导细胞凋亡来杀死细胞的。
