A novel macromolecular prodrug concept exploiting endogenous serum albumin as a drug carrier for cancer chemotherapy
A novel macromolecular prodrug concept exploiting endogenous serum albumin as a drug carrier for cancer chemotherapy
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DOI：
10.1021/jm9905864
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发表时间：
2000-04-06
影响因子：
7.3
通讯作者：
Unger, C
中科院分区：
文献类型：
--
作者：
Kratz, F;M端ller-Driver, R;Unger, C
导言。血清蛋白由于在肿瘤组织中的蓄积，是抗肿瘤药物的潜在药物载体。1实体肿瘤对这些蛋白质的摄取是由多种因素介导的，包括肿瘤代谢活动的增加，肿瘤血管对循环大分子的血管渗透性增强，以及肿瘤组织中缺乏功能正常的淋巴引流系统。2近年来，一些对酸敏感的白蛋白和转铁蛋白与蒽环类药物和烷基化试剂氯苯丁腈的偶联反应显示出良好的体外活性。3-7此外，酸性阿霉素与单抗的结合物和戊二醛交联法制备的白蛋白阿霉素结合物在体内表现出良好的抗肿瘤效果。8、9本课题组研制的阿霉素白蛋白结合物可诱导小鼠肾癌原发灶完全缓解，防止肺转移。相比之下，在实验结束时，接受最佳剂量阿霉素治疗的小鼠表现出清晰可见的肾脏肿瘤和大量的肺转移。这种白蛋白阿霉素结合物是通过将阿霉素的马来酰亚胺羧基糖苷衍生物(见图1)与硫代化白蛋白偶联而成。1含有一种酸敏感连接体，允许药物在肿瘤细胞的溶酶体和内切体中存在的低pH值下释放。我们最近发现，1还可以共价结合到商业上可买到的人血清白蛋白的半胱氨酸-34上，人血清白蛋白是硫代白蛋白和非硫代白蛋白的混合物。血流中大约70%的循环白蛋白是硫代白蛋白，它含有一种可接近的半胱氨酸-34，这种半胱氨酸不会被半胱氨酸或谷胱甘肽等内源性巯基化合物阻挡。12、13考虑到除白蛋白以外的大多数循环血清蛋白上不存在游离的硫基，内源性白蛋白的半胱氨酸-34是循环蛋白表面的一种相当独特的氨基酸，可用于开发新的大分子前药概念。由于马来酰亚胺基团与硫醇基团发生特异性和选择性的反应，我们推测，静脉给药后，马来酰亚胺药物衍生物优先结合到白蛋白半胱氨酸-34位的HS基团是可能的。这样，在血液循环中将硫代结合药物衍生物与内源性白蛋白原位偶联后，就形成了大分子前药。按照这种方法，应该可以避免药物白蛋白结合物的体外合成和表征，这种方法昂贵、耗时，并且依赖于外源和可能的致病蛋白。本工作的目的是通过使用阿霉素马来酰亚胺衍生物1进行体外和体内结合研究来评估我们方法的可行性和选择性。此外，我们想要获得第一个体内证据，在动物肿瘤模型中，即在小鼠肾细胞癌(Rena)中，1优于游离阿霉素。
Introduction. Serum proteins are potential drug carriers of antineoplastic agents due to their accumulation in tumor tissue. 1 Uptake of these proteins in solid tumors is mediated by a number of factors including an increased metabolic activity of tumors, an enhanced vascular permeability of tumor blood vessels for circulating macromolecules, and a lack of a functional lymphatic drainage system in tumor tissue. 2 Recently, a number of acid-sensitive albumin and transferrin conjugates with anthracyclines and the alkylating agent chlorambucil have shown promising in vitro activity. 3-7 In addition, acid-sensitive doxorubicin conjugates with monoclonal antibodies and albumin doxorubicin conjugates prepared by glutaraldehyde cross-linking have shown promising antitumor efficacy in vivo. 8, 9 A selected acid-sensitive doxorubicin albumin conjugate that was developed in our group induced complete remissions of primary kidney tumors in murine renal carcinoma and prevented the formation of metastases in the lungs. In contrast, mice treated with doxorubicin at optimal dose manifested clearly visible kidney tumors at the end of the experiment and large numbers of lung metastases. 10 This albumin doxorubicin conjugate was synthesized by coupling 1, a maleimide carboxylic hydrazone derivative of doxorubicin (see Figure 1), to thiolated albumin. 1 contains an acid-sensitive linker that allows the drug to be released at the low pH values present in lysosomes and endosomes of tumor cells. We have recently shown that 1 also binds covalently to the cysteine-34 of commercially available human serum albumin which is a mixture of mercaptalbumin and nonmercaptalbumin. 11, 12 Approximately 70% of circulating albumin in the blood stream is mercaptalbumin that contains an accessible cysteine-34 which is not blocked by endogenous sulfhydryl compounds such as cysteine or glutathione. 12, 13 Considering that free thiol groups are not found on the majority of circulating serum proteins except for albumin, cysteine-34 of endogenous albumin is a fairly unique amino acid on the surface of a circulating protein that could be exploited for developing a novel macromolecular prodrug concept. Since the maleimide group reacts specifically and selectively with thiol groups, we reasoned that it should be possible to preferentially bind maleimide drug derivatives to the HS group of the cysteine-34 position of albumin after intravenous application. In this way a macromolecular prodrug is formed after in situ coupling of a thiolbinding drug derivative to endogenous albumin in the blood circulation. Following this approach, it should be possible to avoid the ex vivo synthesis and characterization of drug albumin conjugates which are costly, are time-consuming, and rely on exogenous and possibly pathogenic albumin.The objective of the present work was to assess the feasibility and selectivity of our approach by carrying out in vitro and in vivo binding studies using the doxorubicin maleimide derivative 1. In addition, we wanted to obtain the first in vivo evidence that 1 is superior to free doxorubicin in an animal tumor model, ie, in murine renal cell carcinoma (RENCA).