Meschini S, Marra M, Calcabrini A, Federici E, Galeffi C, Arancia G
Laboratory of Ultrastructures, National Institute of Health, Rome, Italy.
Int J Oncol. 2003 Dec;23(6):1505-13. doi: 10.3892/ijo.23.6.1505.
Multidrug-resistance (MDR) is largely caused by the efflux of therapeutics from the tumor cell by means of P-glycoprotein (P-gp), resulting in reduced efficacy of the chemotherapy. In order to overcome MDR, substances, such as verapamil and cyclosporin A (CsA), were employed. As these P-gp modulating agents did not seem promising in clinical practice, new compounds with a low degree of undesirable side effects, were introduced. In this study, bisindolic alkaloid voacamine was examined for its possible capability of enhancing the cytotoxic effect of doxorubicin (DOX) on drug resistant cells. Two different pairs of tumor cell lines were analyzed: the parental lymphoblastoid cell line CEM-WT and its MDR derivative CEM-R, the parental osteosarcoma cell line U-2 OS-WT and its resistant counterpart U-2 OS-R. These cell lines were characterized for their morphological features by scanning electron microscopy (SEM) and for the expression of the main drug transporters by flow cytometric analysis. The effects of voacamine on the cell survival and on both accumulation and efflux of DOX were then investigated. The intracellular distribution of DOX, given alone or in association with CsA or voacamine, was observed by laser scanning confocal microscopy. A differential effect of voacamine between sensitive and resistant cells on the intracellular DOX concentration and distribution was shown. In particular, voacamine induced a significant increase of drug retention and intranuclear location in resistant cells. The results of cell survival experiments revealed an enhancement of the cytotoxic effect of DOX induced by voacamine, confirmed by evident morphological changes observed by SEM. These findings suggest promising applications of this natural substance against MDR tumors.
多药耐药性（MDR）很大程度上是由肿瘤细胞通过P-糖蛋白（P-gp）将治疗药物排出所致，从而导致化疗疗效降低。为了克服MDR，人们使用了维拉帕米和环孢素A（CsA）等物质。由于这些P-gp调节剂在临床实践中似乎前景不佳，因此引入了副作用较小的新化合物。在本研究中，对双吲哚生物碱沃卡明增强阿霉素（DOX）对耐药细胞细胞毒性作用的可能性进行了研究。分析了两对不同的肿瘤细胞系：亲本淋巴母细胞系CEM-WT及其MDR衍生物CEM-R，亲本骨肉瘤细胞系U-2 OS-WT及其耐药对应物U-2 OS-R。通过扫描电子显微镜（SEM）对这些细胞系的形态特征进行了表征，并通过流式细胞术分析了主要药物转运蛋白的表达。然后研究了沃卡明对细胞存活以及DOX的蓄积和流出的影响。通过激光扫描共聚焦显微镜观察了单独给予DOX或与CsA或沃卡明联合给予时DOX的细胞内分布。结果表明，沃卡明对敏感细胞和耐药细胞的细胞内DOX浓度和分布有不同的影响。特别是，沃卡明使耐药细胞中的药物滞留和核内定位显著增加。细胞存活实验结果显示，沃卡明增强了DOX的细胞毒性作用，SEM观察到的明显形态变化证实了这一点。这些发现表明这种天然物质在对抗MDR肿瘤方面具有广阔的应用前景。
