Chen W S, Luker K E, Dahlheimer J L, Pica C M, Luker G D, Piwnica-Worms D
Laboratory of Molecular Radiopharmacology, Department of Radiology and Department of Molecular Biology and Pharmacology, Washington University Medical School, St. Louis, MO 63110, USA.
Biochem Pharmacol. 2000 Aug 1;60(3):413-26. doi: 10.1016/s0006-2952(00)00341-5.
Multidrug resistance (MDR1) P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP1), and breast cancer resistance protein (BCRP/MXR/ABCP) are members of the ATP-binding-cassette (ABC) superfamily of membrane transporters and are thought to function as energy-dependent efflux pumps of a variety of structurally diverse chemotherapeutic agents. We herein report the characterization of (99m)Tc-Tetrofosmin, a candidate radiopharmaceutical substrate of ABC transporters. (99m)Tc-Tetrofosmin showed high membrane potential-dependent accumulation in drug-sensitive KB 3-1 cells and low antagonist-reversible accumulation in MDR KB 8-5 and KB 8-5-11 cells in proportion to levels of MDR1 Pgp expression. In KB 8-5 cells, EC(50) values of the potent MDR antagonists 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), (2R)-anti-5-¿3-[4-(10, 11-difluoromethanodibenzo-suber-5-yl)piperazin-1-yl]-2 -hydroxypropoxy ¿quinoline trihydrochloride (LY335979), and (3'-keto-Bmt')-[Val(2)]-cyclosporin A (PSC 833) were 40, 66, and 986 nM, respectively. Furthermore, only baculoviruses carrying human MDR1, but not MDR3, conferred both a decrease in accumulation of (99m)Tc-Tetrofosmin in host Spodoptera frugiperda (Sf9) cells and a GF120918-induced enhancement. Transport studies with a variety of stably transfected and drug-selected tumor cell lines were performed with (99m)Tc-Tetrofosmin and compared with (99m)Tc-Sestamibi, a previously validated MDR imaging agent. MDR1 Pgp readily transported each agent. To a lesser extent, MRP1 also transported each agent, likely as co-transport substrates with GSH; neither agent was a substrate for the BCRP/MXR/ABCP half-transporter. In mdr1a(-/-) and mdr1a/1b(-/-) mice, (99m)Tc-Tetrofosmin showed approximately 3. 5-fold greater brain uptake and retention compared with wild-type, with no net change in blood pharmacokinetics, consistent with transport in vivo by Pgp expressed at the capillary blood-brain barrier. Molecular imaging of the functional transport activity of ABC transporters in vivo with (99m)Tc-Tetrofosmin and related radiopharmaceuticals may enable non-invasive monitoring of chemotherapeutic and MDR gene therapy protocols.
多药耐药（MDR1）P-糖蛋白（Pgp）、多药耐药相关蛋白（MRP1）和乳腺癌耐药蛋白（BCRP/MXR/ABCP）是膜转运蛋白ATP结合盒（ABC）超家族的成员，被认为作为多种结构不同的化疗药物的能量依赖性外排泵发挥作用。我们在此报告ABC转运蛋白的候选放射性药物底物（99m）Tc-替曲膦的特性。（99m）Tc-替曲膦在药物敏感的KB 3-1细胞中显示出高膜电位依赖性积累，而在MDR KB 8-5和KB 8-5-11细胞中的积累具有低拮抗剂可逆性，且与MDR1 Pgp表达水平成比例。在KB 8-5细胞中，强效MDR拮抗剂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-吖啶甲酰胺（GF120918）、（2R）-反式-5-（3-[4-（10,11-二氟亚甲基二苯并-5-亚基）哌嗪-1-基]-2-羟基丙氧基）喹啉三盐酸盐（LY335979）和（3'-酮基-Bmt'）-[Val（2）]-环孢素A（PSC 833）的半数有效浓度（EC50）值分别为40、66和986 nM。此外，只有携带人MDR1而非MDR3的杆状病毒能使宿主草地贪夜蛾（Sf9）细胞中（99m）Tc-替曲膦的积累减少，并增强GF120918诱导的积累。用（99m）Tc-替曲膦对多种稳定转染并经药物筛选的肿瘤细胞系进行转运研究，并与先前验证的MDR显像剂（99m）Tc-司他比进行比较。MDR1 Pgp能轻易转运每种药物。MRP1在较小程度上也能转运每种药物，可能作为与谷胱甘肽的共转运底物；两种药物都不是BCRP/MXR/ABCP半转运蛋白的底物。在mdr1a（-/-）和mdr1a/1b（-/-）小鼠中，（99m）Tc-替曲膦的脑摄取和滞留量比野生型高约3.5倍，血液药代动力学无净变化，这与毛细血管血脑屏障处表达的Pgp在体内的转运一致。用（99m）Tc-替曲膦和相关放射性药物对ABC转运蛋白的体内功能转运活性进行分子显像，可能实现对化疗和MDR基因治疗方案的无创监测。
