Dvorakova Katerina, Payne Claire M, Tome Margaret E, Briehl Margaret M, Vasquez Miguel A, Waltmire Caroline N, Coon Amy, Dorr Robert T
Arizona Cancer Center, 1515 North Campbell Avenue, Tucson, AZ 85724, USA.
Mol Cancer Ther. 2002 Jan;1(3):185-95.
Imexon is an aziridine-containing iminopyrrolidone with selective growth-inhibitory potency for multiple myeloma. Our previous research indicates that imexon induces mitochondrial alterations, oxidative stress, and apoptosis. This drug represents an interesting model drug with a nonmyelosuppressive profile to study the basic mechanisms leading to antitumor activity and resistance. The major purpose of this study was to characterize an imexon-resistant RPMI8226/I cell line that was developed from RPMI8226 cells by continuous exposure to imexon. No significant differences were observed in the sensitivity to several cytotoxic drugs, including mitoxantrone, mitomycin C, melphalan, methotrexate, cytarabine, cisplatin, vincristine, and paclitaxel, in the imexon-resistant cells. However, RPMI8226/I cells were cross-resistant to arsenic trioxide, doxorubicin, fluorouracil, etoposide, irinotecan, and especially IFN-alpha. The data from DNA microarray and Western blot analyses indicated that the levels of antiapoptotic proteins Bcl-2 and thioredoxin-2, which reside mainly in the mitochondria, are increased in RPMI8226/I cells. In addition, increased levels of lung resistance protein were detected in imexon-resistant cells. Expression of P-glycoprotein was not detected in RPMI8226/I cells. No loss of mitochondrial membrane potential or increase in the levels of reactive oxygen species was observed in RPMI8226/I cells after exposure to imexon; however, the levels of glutathione are increased in the RPMI8226/I cells. Transmission electron microscopy revealed significant changes in the mitochondrial morphology of RPMI8226/I cells, whereas no ultrastructural changes were observed in other cellular compartments. Imexon-resistant RPMI8226/I myeloma cells appear to have a unique mechanism of resistance that is associated with morphological alterations of mitochondria, increased protection against oxidative stress, elevated levels of glutathione, and enhanced expression of antiapoptotic mitochondrial proteins.
艾美克生是一种含氮丙啶的亚氨基吡咯烷酮，对多发性骨髓瘤具有选择性生长抑制作用。我们之前的研究表明，艾美克生可诱导线粒体改变、氧化应激和细胞凋亡。这种药物是一种有趣的模型药物，具有非骨髓抑制特性，可用于研究导致抗肿瘤活性和耐药性的基本机制。本研究的主要目的是鉴定一种耐艾美克生的RPMI8226/I细胞系，该细胞系是通过将RPMI8226细胞连续暴露于艾美克生而获得的。在耐艾美克生的细胞中，未观察到对几种细胞毒性药物（包括米托蒽醌、丝裂霉素C、美法仑、甲氨蝶呤、阿糖胞苷、顺铂、长春新碱和紫杉醇）的敏感性有显著差异。然而，RPMI8226/I细胞对三氧化二砷、阿霉素、氟尿嘧啶、依托泊苷、伊立替康，尤其是干扰素-α具有交叉耐药性。DNA微阵列和蛋白质印迹分析数据表明，主要存在于线粒体中的抗凋亡蛋白Bcl-2和硫氧还蛋白-2在RPMI8226/I细胞中的水平升高。此外，在耐艾美克生的细胞中检测到肺耐药蛋白水平升高。在RPMI8226/I细胞中未检测到P-糖蛋白的表达。在RPMI8226/I细胞暴露于艾美克生后，未观察到线粒体膜电位的丧失或活性氧水平的增加；然而，RPMI8226/I细胞中的谷胱甘肽水平升高。透射电子显微镜显示RPMI8226/I细胞的线粒体形态有显著变化，而在其他细胞区室中未观察到超微结构变化。耐艾美克生的RPMI8226/I骨髓瘤细胞似乎具有独特的耐药机制，这与线粒体形态改变、对氧化应激的保护增强、谷胱甘肽水平升高以及抗凋亡线粒体蛋白的表达增强有关。
