Biological evaluation of boronated unnatural amino acids as new boron carriers
Biological evaluation of boronated unnatural amino acids as new boron carriers
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DOI：
10.1016/j.apradiso.2009.03.104
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发表时间：
2009-07-01
影响因子：
1.6
通讯作者：
Chandra, S.
中科院分区：
文献类型：
--
作者：
Kabalka, G. W.;Yao, M. -L.;Chandra, S.
迫切需要新的和更有效的硼递送剂到肿瘤细胞中用于硼中子捕获治疗（BNCT）。一类硼化的非天然环状氨基酸在动物和细胞培养模型中显示出对肿瘤的显著选择性，远远优于目前临床BNCT中使用的药剂上级。这些氨基酸之一，1-氨基-3-硼环戊烷羧酸（ABCPC），在荷黑色素瘤小鼠模型中显示肿瘤与血液的比率为8，肿瘤与正常脑的比率接近21。这项工作代表了该化合物在EMT 6鼠乳腺癌小鼠模型和T98 G人胶质母细胞瘤细胞系中肿瘤靶向的进一步生物学表征。携带EMT 6肿瘤的雌性BALB/c小鼠注射相同浓度的ABCPC的顺式和反式异构体的外消旋混合物的果糖复合物形式。在注射后1、3和5小时测量肿瘤、血液、脑、皮肤和肝组织中的硼浓度。这些观察揭示了硼在肿瘤靶向中的顺式和反式异构体的外消旋混合物的显著差异。这意味着该化合物的L和D形式的进一步分离可以比外消旋混合物提供的更高程度地增强肿瘤靶向。由于摄取测量是在均质化的肿瘤和正常组织中进行的，因此对由氨基酸的各种异构体形式产生的硼的亚细胞位置知之甚少。为了研究ABCPC在T98 G人胶质母细胞瘤细胞中硼的亚细胞递送，我们采用基于二次离子质谱（西姆斯）的离子显微镜技术，该技术能够以500 nm的空间分辨率定量成像细胞和组织中的同位素（元素）梯度。将T98 G细胞暴露于含有100 ppm硼当量的果糖复合物形式的ABCPC的L和D异构体的混合物的营养培养基中1小时。在该处理后，将细胞快速冷冻、冷冻破碎并冷冻干燥用于西姆斯分析。在一个小时的曝光，ABCPC提供3/1的细胞内到细胞外硼的分区。西姆斯成像显示，来自ABCPC的硼分布在整个细胞中，包括细胞核。暴露一小时内的硼递送水平上级于对硼苯丙氨酸（BPA）和硼硫合钠（BSH），其先前已通过西姆斯在相同细胞系中研究。这些令人鼓舞的观察结果为进一步将ABCPC异构分离成D和L形式以增强肿瘤靶向和继续测试这些化合物作为BNCT中的新硼载体提供了令人信服的支持。(C)2009年由Elsevier Ltd.出版
There is a pressing need for new and more efficient boron delivery agents to tumor cells for use in boron neutron capture therapy (BNCT). A class of boronated unnatural cyclic amino acids has demonstrated a remarkable selectivity toward tumors in animal and cell culture models, far superior to currently used agents in clinical BNCT. One of these amino acids, 1-amino-3-boronocyclopentanecarboxylic acid (ABCPC), has shown a tumor to blood ratio of 8 and a tumor to normal brain ratio of nearly 21 in a melanoma bearing mouse model. This work represents further biological characterization of this compound for tumor targeting in an EMT6 murine mammary carcinoma mouse model and a T98G human glioblastoma cell line. Female BALB/c mice bearing EMT6 tumors were injected with the fructose complex form of racemic mixtures of cis and trans isomers of ABCPC in identical concentrations. Boron concentrations were measured in the tumor, blood, brain, skin, and liver tissues at 1, 3, and 5 h post-injection. These observations revealed a remarkable difference in racemic mixtures of cis and trans isomers in tumor targeting by boron. This implies that further separation of the L and D forms of this compound may enhance tumor targeting to an even higher degree than that provided by the racemic mixtures. Since the uptake measurements were made in homogenized tumor and normal tissues, little is known about the subcellular location of the boron arising from the various isomeric forms of the amino acid. To study subcellular delivery of boron from ABCPC in T98G human glioblastoma cells, we employed secondary ion mass spectrometry (SIMS) based technique of ion microscopy, which is capable of quantitatively imaging isotopic (elemental) gradients in cells and tissues at 500 nm spatial resolution. The T98G cells were exposed to the nutrient medium containing 100 ppm boron equivalent of a mixture of both L and D isomers of ABCPC in the form of a fructose complex for 1 h. Following this treatment, the cells were fast frozen, freeze-fractured, and freeze-dried for SIMS analysis. Within an hour of exposure, ABCPC provided partitioning of intracellular to extracellular boron of 3/1. SIMS imaging revealed that boron from ABCPC was distributed throughout the cell, including the nucleus. This level of boron delivery within an hour of exposure is superior to p-boronophenylalanine (BPA) and sodium borocaptate (BSH), which have been previously studied by SIMS in the same cell line. These encouraging observations provide compelling support for further isomeric separations of ABCPC into the D and L forms for enhanced tumor targeting and continued testing of these compounds as new boron carriers in BNCT. (C) 2009 Published by Elsevier Ltd.