Collaborative Research: Integrative Adaptation of Dendrimer-peptide Conjugates for Cancer Immunotherapy

免疫疗法，利用病人自身的免疫系统来治疗疾病，已经彻底改变了癌症治疗。目前临床上使用的大多数免疫治疗药物都是基于生物制剂，如抗体（仅与特定抗原结合的蛋白质），可以增强对肿瘤细胞的免疫监视。然而，这种基于抗体的药物价格昂贵，而且往往导致令人失望的临床结果，特别是单独使用时。使用肽（由20-30个氨基酸链组成的大分子）将是一个有希望的替代方案；然而，它们的结合弱于相应的抗体已被认为是一个主要的弱点。最近，提出这项工作的合作团队已经证明，小型球形聚合物（大小为人类头发厚度的1/10,000），称为聚（氨基胺）（PAMAM）树状大分子，可以被设计成显着提高肽的结合强度高达一百万倍。在这项提议中，研究小组假设，附着在计算优化的肽上的树状大分子可以增强免疫系统攻击肿瘤细胞，从而最大化其免疫治疗效果。在此项目成功完成后，该团队将致力于开发一种与各种免疫治疗肽兼容的新技术。结合研究工作，该项目包括各种教育活动，招收研究生，本科生和高中生。这些活动不仅可以帮助高学历学生积极参与前沿科学，还可以激发大学预科学生对STEM的兴趣，这将对我们国家保持世界科学和工程领导者的地位产生深远的影响。研究活动的总体目标是整合计算和实验方法来设计基于树突肽偶联物的纳米粒子平台，以增强癌症免疫治疗。该合作团队已经证明，聚氨基胺（PAMAM）树状大分子是多价结合效应的优秀介质，可以显著增强小分子、抗体和肽的结合活性。这种增强结合的纳米工程方法可以直接应用于改善依赖于有效阻断免疫细胞和肿瘤细胞之间结合的癌症免疫治疗。鉴于与靶免疫检查点蛋白（如程序性死亡配体1 （PD-L1）、程序性细胞死亡蛋白-1 （PD-1）和细胞毒性t淋巴细胞相关蛋白4 (CTLA-4)）的强结合是有效诱导检查点阻断所必需的，迄今为止fda批准的所有免疫检查点抑制剂（ICIs）都是基于具有强结合亲和力的抗体。不幸的是，这种基于抗体的治疗方法价格昂贵，而且常常导致令人失望的临床结果，特别是单独使用时。该团队假设，树突状分子与计算优化的肽结合，靶向T细胞上的多个免疫检查点受体，将大大提高其他弱结合肽的结合强度，从而最大限度地提高其免疫治疗效率。与全抗体相比，多肽的使用将是有利的，因为它们具有成本效益，并且适用于各种工程策略。与其他常用的纳米颗粒药物传递系统相比，所提出的树突-肽偶联（DPC）系统，由被肽功能化的工程PAMAM树突组成，相对简单。然而，DPC系统的独特和创新之处在于：i)肽可以通过高通量计算进行调整和优化；Ii)树突状大分子使多肽聚合，利用强大的多价结合效应（贪婪）；Iii)折叠后的肽可以稳定在树突表面，进一步促进结合增强；iv)这种方法几乎与任何肽兼容，为各种组合提供了模块化平台。在这个项目的成功完成后，我们将对肽设计/合成、聚合物工程、DPCs的结合动力学和生物行为有基本的了解。该项目将扩大未被充分代表的少数族裔和妇女在不同教育水平的STEM研究中的参与。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical SummaryImmunotherapy, utilization of a patient’s own immune system to treat diseases, has revolutionized cancer treatment. Most of the immunotherapeutic drugs that are being used in the clinic are based on biologics, such as antibodies (proteins that bind to specific antigens only), that boost immune surveillance against tumor cells. However, such antibody-based drugs are expensive and often result in disappointing clinical outcomes, particularly when used alone. The use of peptides (macromolecules made from a chain of 20-30 amino acids) would be a promising alternative; however, their weaker binding than the corresponding antibodies has been recognized as a major weakness. Recently, the collaborative team proposing this work have demonstrated that small ball-shaped polymers (size of 1/10,000 of human hair thickness), called poly(amidoamine) (PAMAM) dendrimers, can be engineered to dramatically improve the binding strength of the peptides up to a million times. In this proposal, the team hypothesizes that dendrimers attached with computationally optimized peptides can boost up the immune system to attack tumor cells, thereby maximizing their immunotherapeutic effect. Upon successful completion of this project, the team will contribute to developing a new technology that would be compatible with various immunotherapeutic peptides. Integrated with the research effort, this project includes various educational activities that recruit graduate students, undergraduate students, and high school students. These activities will not only help advanced degree students be actively involved in cutting-edge science but also stimulate STEM interests of pre-college students, which will have profound impact on our nation to maintain the position as the world leader of science and engineering.Technical SummaryThe overarching goal of the research activities is to integrate computational and experimental methods to engineer a nanoparticle platform based on dendrimer-peptide conjugates for enhanced cancer immunotherapy. The collaborative team has demonstrated that poly(amidoamine) (PAMAM) dendrimers are excellent mediators for multivalent binding effects, as observed by dramatically enhanced binding avidities of small molecules, antibodies, and peptides. This nanoengineering approach for binding enhancement could be directly applicable for improving cancer immunotherapy that relies on efficient blocking of binding between immune and tumor cells. Given that strong binding to the target immune checkpoint proteins, such as programmed death-ligand 1 (PD-L1), programmed cell death protein-1 (PD-1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), is necessary to effectively induce the checkpoint blockade, all the FDA-approved immune checkpoint inhibitors (ICIs) to date are based on antibodies with strong binding affinities. Unfortunately, such antibody-based therapeutics are expensive and often result in disappointing clinical outcomes, particularly when used alone. The team hypothesizes that dendrimer conjugation with computationally optimized peptides that target multiple immune checkpoint receptors on T cells would substantially improve the binding strength of otherwise weakly binding peptides, which in turn would maximize their immunotherapeutic efficiency. The use of peptides would be advantageous, as they are cost-effective and amenable to various engineering strategies, in contrast to whole antibodies. The proposed dendrimer-peptide conjugate (DPC) systems, consisting of engineered PAMAM dendrimers functionalized with peptides, are relatively simple in comparison to other commonly used nanoparticle drug delivery systems. Yet, the DPC systems are unique and innovative in that: i) peptides can be adapted and optimized via a high-throughput computation; ii) dendrimers multimerize peptides to exploit strong multivalent binding effects (avidity); iii) folded peptides can be stabilized on the dendrimer surface, further contributing for binding enhancement; and iv) this approach is compatible with virtually any peptides, providing a modular platform for various combinations. Upon successful completion of this project, we will have obtained fundamental understanding in peptide design/synthesis, polymer engineering, and binding kinetics and biological behaviors of the DPCs. The project will broaden participation of underrepresented minorities and women in STEM research at various educational levels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.