Yoon2017 - Mathematical Modeling of Mutant Transferrin-CRM107 Molecular Conjugates for Cancer Therapy

Mathematical modeling of mutant transferrin-CRM107 molecular conjugates for cancer therapy.
Yoon DJ1, Chen KY1, Lopes AM1, Pan AA1, Shiloach J2, Mason AB3, Kamei DT4.
Author information

1
Department of Bioengineering, University of California, Los Angeles, 420 Westwood Plaza, 5121 Engineering V, Los Angeles, CA 90095, USA.
2
Biotechnology Core Laboratory, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health, Bethesda, MD 20892, USA.
3
Department of Biochemistry, University of Vermont College of Medicine, Burlington, VT 05405, USA.
4
Department of Bioengineering, University of California, Los Angeles, 420 Westwood Plaza, 5121 Engineering V, Los Angeles, CA 90095, USA. Electronic address: [e-mail].

Abstract

The transferrin (Tf) trafficking pathway is a promising mechanism for use in targeted cancer therapy due to the overexpression of transferrin receptors (TfRs) on cancerous cells. We have previously developed a mathematical model of the Tf/TfR trafficking pathway to improve the efficiency of Tf as a drug carrier. By using diphtheria toxin (DT) as a model toxin, we found that mutating the Tf protein to change its iron release rate improves cellular association and efficacy of the drug. Though this is an improvement upon using wild-type Tf as the targeting ligand, conjugated toxins like DT are unfortunately still highly cytotoxic at off-target sites. In this work, we address this hurdle in cancer research by developing a mathematical model to predict the efficacy and selectivity of Tf conjugates that use an alternative toxin. For this purpose, we have chosen to study a mutant of DT, cross-reacting material 107 (CRM107). First, we developed a mathematical model of the Tf-DT trafficking pathway by extending our Tf/TfR model to include intracellular trafficking via DT and DT receptors. Using this mathematical model, we subsequently investigated the efficacy of several conjugates in cancer cells: DT and CRM107 conjugated to wild-type Tf, as well as to our engineered mutant Tf proteins (K206E/R632A Tf and K206E/R534A Tf). We also investigated the selectivity of mutant Tf-CRM107 against non-neoplastic cells. Through the use of our mathematical model, we predicted that (i) mutant Tf-CRM107 exhibits a greater cytotoxicity than wild-type Tf-CRM107 against cancerous cells, (ii) this improvement was more drastic with CRM107 conjugates than with DT conjugates, and (iii) mutant Tf-CRM107 conjugates were selective against non-neoplastic cells. These predictions were validated with in vitro cytotoxicity experiments, demonstrating that mutant Tf-CRM107 conjugates is indeed a more suitable therapeutic agent. Validation from in vitro experiments also confirmed that such whole-cell kinetic models can be useful in cancer therapeutic design.

Copyright © 2017 Elsevier Ltd. All rights reserved.

用于癌症治疗的突变转铁蛋白-CRM107分子偶联物的数学建模
Yoon DJ1, Chen KY1, Lopes AM1, Pan AA1, Shiloach J2, Mason AB3, Kamei DT4.
作者信息
1 加州大学洛杉矶分校生物工程系，美国加利福尼亚州洛杉矶市韦斯特伍德广场420号工程V楼5121室，邮编90095。
2 美国国立卫生研究院国立糖尿病、消化和肾脏疾病研究所生物技术核心实验室，美国马里兰州贝塞斯达市，邮编20892。
3 佛蒙特大学医学院生物化学系，美国佛蒙特州伯灵顿市，邮编05405。
4 加州大学洛杉矶分校生物工程系，美国加利福尼亚州洛杉矶市韦斯特伍德广场420号工程V楼5121室，邮编90095。电子通讯地址：[e-mail]。
摘要
转铁蛋白（transferrin, Tf）运输通路因癌细胞表面转铁蛋白受体（transferrin receptor, TfR）过表达，成为靶向癌症治疗的极具前景的策略。我们此前已开发Tf/TfR运输通路的数学模型，以提升转铁蛋白作为药物载体的效率。以白喉毒素（diphtheria toxin, DT）为模型毒素时，我们发现突变转铁蛋白可通过改变其铁释放速率，提升药物的细胞结合能力与疗效。尽管这相较于以野生型转铁蛋白作为靶向配体已有改进，但诸如白喉毒素这类偶联毒素仍会在非靶标位点产生极强的细胞毒性。本研究针对癌症研究中的这一难题，开发数学模型以预测使用替代毒素的转铁蛋白偶联物的疗效与选择性。为此，我们选择研究白喉毒素的突变体——交叉反应物质107（cross-reacting material 107, CRM107）。首先，我们将原有Tf/TfR模型拓展至包含白喉毒素及其受体的胞内运输过程，以此构建Tf-DT运输通路的数学模型。基于该模型，我们随后研究了多种偶联物在癌细胞中的疗效：分别与野生型转铁蛋白、我们工程化改造的突变转铁蛋白（K206E/R632A Tf及K206E/R534A Tf）偶联的白喉毒素与CRM107。我们还探究了突变转铁蛋白-CRM107对非肿瘤细胞的选择性。通过本数学模型，我们预测：（1）突变转铁蛋白-CRM107对癌细胞的细胞毒性强于野生型转铁蛋白-CRM107；（2）相较于白喉毒素偶联物，CRM107偶联物的这一提升效果更为显著；（3）突变转铁蛋白-CRM107偶联物对非肿瘤细胞具有选择性。上述预测均通过体外细胞毒性实验得到验证，结果表明突变转铁蛋白-CRM107偶联物确实是更合适的治疗制剂。体外实验的验证结果也证实，此类全细胞动力学模型可有效用于癌症治疗方案的设计。
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