Departments of Chemical and Biochemical Engineering and Biomedical Engineering, Rutgers University, Piscataway, New Jersey; and.
J Nucl Med. 2014 Jan;55(1):107-14. doi: 10.2967/jnumed.113.125476. Epub 2013 Dec 12.
This study evaluates targeted liposomes loaded with the α-particle generator (225)Ac to selectively kill prostate-specific membrane antigen (PSMA)-expressing cells with the aim to assess their potential for targeted antivascular radiotherapy.
In this study, PEGylated liposomes were loaded with (225)Ac and labeled with the mouse antihuman PSMA J591 antibody or with the A10 PSMA aptamer. The targeting selectivity, extent of internalization, and killing efficacy of liposomes were evaluated on monolayers of prostate cancer cells intrinsically expressing PSMA (human LNCaP and rat Mat-Lu cells) and on monolayers of HUVEC induced to express PSMA (induced HUVEC).
The loading efficiency of (225)Ac into preformed liposomes ranged from 58.0% ± 4.6% to 85.6% ± 11.7% of introduced radioactivity. The conjugation reactions resulted in approximately 17 ± 2 J591 antibodies and 9 ± 2 A10 aptamers per liposome. The average size of liposomes, 107 ± 2 nm in diameter, was not affected by conjugation or loading. LNCaP cells exhibit 2:1:0.5 relative PSMA expression, compared with MatLu and induced HUVEC, respectively, based on flow cytometry detecting association of the J591 antibody. J591-labeled liposomes display higher levels of total specific binding to all cell lines than A10 aptamer-labeled liposomes. Specific cell association of targeted liposomes increases with incubation time. Cytotoxicity studies demonstrate that radiolabeled J591-labeled liposomes are most cytotoxic, with median lethal dose values, after 24 h of incubation, equal to 1.96 (5.3 × 10(-5)), 2.92 × 10(2) (7.9 × 10(-3)), and 2.33 × 10(1) Bq/mL (6.3 × 10(-4) μCi/mL) for LNCaP, Mat-Lu, and induced HUVEC, respectively, which are comparable to the values for the radiolabeled J591 antibody. For A10 aptamer-labeled liposomes, the corresponding values are 3.70 × 10(1) (1.0 × 10(-3)), 1.85 × 10(3) (5.0 × 10(-2)), and 4.07 × 10(3) Bq/mL (1.1 × 10(-1) μCi/mL), respectively.
Our studies demonstrate that anti-PSMA-targeted liposomes loaded with (225)Ac selectively bind, become internalized, and kill PSMA-expressing cells including endothelial cells induced to express PSMA. These findings-combined with the unique ability of liposomes to be easily tuned, in terms of size and surface modification, for optimizing biodistributions-suggest the potential of PSMA-targeting liposomes encapsulating α-particle emitters for selective antivascular α radiotherapy.
本研究评估了靶向载α 粒子发生器（225）Ac 的脂质体，以选择性杀伤前列腺特异性膜抗原（PSMA）表达细胞，旨在评估其用于靶向抗血管放疗的潜力。
在这项研究中，聚乙二醇化脂质体负载（225）Ac，并标记以小鼠抗人 PSMA J591 抗体或 A10 PSMA 适体。通过单层前列腺癌细胞（人 LNCaP 和大鼠 Mat-Lu 细胞）和诱导表达 PSMA 的单层人脐静脉内皮细胞（诱导 HUVEC）评估脂质体的靶向选择性、内化程度和杀伤效力。
（225）Ac 预形成脂质体的负载效率范围为 58.0%±4.6%至 85.6%±11.7%。结合反应导致每个脂质体约有 17±2 个 J591 抗体和 9±2 个 A10 适体。脂质体的平均粒径为 107±2nm，直径不受结合或负载的影响。基于流式细胞术检测 J591 抗体的结合，LNCaP 细胞相对于 MatLu 和诱导 HUVEC 的 PSMA 表达分别为 2:1:0.5。与 A10 适体标记的脂质体相比，J591 标记的脂质体对所有细胞系的总特异性结合水平更高。靶向脂质体的细胞结合随着孵育时间的延长而增加。细胞毒性研究表明，放射性标记的 J591 标记的脂质体最具细胞毒性，孵育 24 小时后的半数致死剂量值分别为 1.96（5.3×10（-5））、2.92×10（2）（7.9×10（-3））和 2.33×10（1）Bq/mL（6.3×10（-4）μCi/mL）对于 LNCaP、Mat-Lu 和诱导的 HUVEC，分别与放射性标记的 J591 抗体相当。对于 A10 适体标记的脂质体，相应的值分别为 3.70×10（1）（1.0×10（-3））、1.85×10（3）（5.0×10（-2））和 4.07×10（3）Bq/mL（1.1×10（-1）μCi/mL）。
我们的研究表明，负载（225）Ac 的抗 PSMA 靶向脂质体选择性结合、内化并杀伤包括诱导表达 PSMA 的内皮细胞在内的 PSMA 表达细胞。这些发现——结合脂质体在大小和表面修饰方面易于调整以优化生物分布的独特能力——表明封装α 粒子发射体的 PSMA 靶向脂质体用于选择性抗血管α 放疗的潜力。
