Bristol-Myers Squibb, PO Box 4000, Princeton, NJ 08543-4000, USA.
J Pharmacol Exp Ther. 2011 May;337(2):423-32. doi: 10.1124/jpet.110.175604. Epub 2011 Jan 24.
Ixabepilone is the first epothilone to be approved for clinical use. Current data suggest the epothilones have a role in treating taxane-resistant cancers and ixabepilone is unaffected by at least some of the mechanisms underlying chemoresistance. Here, we report a series of cytotoxicity and transport studies to assess the potential role of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) in ixabepilone resistance. A significant decrease in ixabepilone-mediated cytotoxicity was observed in Madin-Darby canine kidney cells transfected with human multidrug resistance 1 (MDR1) comparative with the parental cells (IC(50) > 2000 nM versus 90 nM). Overexpression of P-gp also resulted in significantly decreased cell susceptibility to docetaxel, paclitaxel, and vinblastine. Bidirectional transport of ixabepilone across monolayers of porcine kidney-derived cells expressing human MDR1 showed a significantly increased efflux ratio relative to the parental cells. A BCRP-overexpressing cell line was developed by transfecting human embryonic kidney (HEK)-293 cells with BCRP cDNA and confirmed by immunoblotting and bodipy prazosin and mitoxantrone uptake. Neither P-gp nor multidrug resistance protein 2 was detected in the cells by corresponding polyclonal antibodies. This HEK-BCRP cell line demonstrated resistance to docetaxel, paclitaxel, vinblastine, and mitoxantrone, in comparison with the parental cell line (7.3, 4.3, 2.9, and 11.9 resistance factor, respectively). Transport inhibition by BCRP inhibitor fumitremorgin C and broad efflux inhibitor N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918) restored drug sensitivity. In contrast, ixabepilone was far less susceptible to BCRP-mediated resistance, resulting in a resistance factor of only 1.2-fold. In summary, these results suggest that P-gp could cause resistance to ixabepilone in tumors and affect the disposition of the drug, but it is unlikely that BCRP mediates any drug resistance to ixabepilone.
伊沙匹隆是首个获准临床应用的埃博霉素类药物。目前的数据表明，埃博霉素类药物在治疗紫杉烷类耐药性癌症方面具有一定作用，而伊沙匹隆不受至少部分耐药机制的影响。在这里，我们报告了一系列细胞毒性和转运研究结果，以评估多药耐药蛋白 1（MDR1）和乳腺癌耐药蛋白（BCRP）在伊沙匹隆耐药中的潜在作用。与亲本细胞相比，转染人 MDR1 的 Madin-Darby 犬肾细胞中伊沙匹隆介导的细胞毒性显著降低（IC50＞2000 nM 对 90 nM）。P-糖蛋白的过度表达也导致细胞对多西他赛、紫杉醇和长春碱的敏感性显著降低。伊沙匹隆在表达人 MDR1 的猪肾源性细胞单层中的双向转运显示出与亲本细胞相比，流出比显著增加。通过将 BCRP cDNA 转染到人胚肾（HEK）-293 细胞中，开发了一个 BCRP 过表达细胞系，并通过免疫印迹和 bodipy 哌唑嗪和米托蒽醌摄取进行了验证。相应的多克隆抗体未在细胞中检测到 P-糖蛋白或多药耐药蛋白 2。与亲本细胞系相比，该 HEK-BCRP 细胞系对多西他赛、紫杉醇、长春碱和米托蒽醌表现出耐药性（分别为 7.3、4.3、2.9 和 11.9 耐药系数）。BCRP 抑制剂 furitremorgin C 和广谱外排抑制剂 N-（4-[2-（1,2,3,4-四氢-6,7-二甲氧基-2-异喹啉基）乙基]-苯基）-9,10-二氢-5-甲氧基-9-氧代-4-吖啶羧酸酰胺（GF120918）的转运抑制恢复了药物敏感性。相比之下，伊沙匹隆对 BCRP 介导的耐药性的敏感性要低得多，导致耐药系数仅为 1.2 倍。总之，这些结果表明，P-糖蛋白可能导致肿瘤对伊沙匹隆产生耐药性，并影响药物的处置，但 BCRP 不太可能介导伊沙匹隆的任何耐药性。
