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

非技术概述免疫疗法利用患者自身的免疫系统来治疗疾病，使癌症治疗发生了革命性的变化。临床上使用的大多数免疫治疗药物都是基于生物制剂，例如抗体(只与特定抗原结合的蛋白质)，这些抗体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，而且经常导致令人失望的临床结果，特别是单独使用时。使用多肽(由20-30个氨基酸组成的大分子)将是一个有希望的替代方案；然而，它们的结合比相应的抗体弱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，被称为聚酰胺胺(PAMAM)树枝状大分子的小球状聚合物(大小为人类头发厚度的1/10000)可以被设计成显著提高多肽的结合强度，最高可达100万倍。在这项提案中，该团队假设，树枝状大分子与经过计算优化的多肽相连，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。在该项目成功完成后，该团队将为开发一种与各种免疫治疗多肽兼容的新技术做出贡献。与研究工作相结合，该项目包括招收研究生、本科生和高中生的各种教育活动。这些活动不仅将帮助高级学位学生积极参与尖端科学，还将激发预科学生的STEM兴趣，这将对我国保持世界科学和工程领先者的地位产生深远影响。技术总结本研究活动的总体目标是将计算和实验方法相结合，设计一个基于树枝状大分子-多肽结合物的纳米颗粒平台，用于增强癌症免疫治疗。合作团队已经证明，聚酰胺胺(PAMAM)树枝状大分子是多价结合效应的优秀介体，小分子、抗体和多肽的结合亲和力显著增强。这种结合增强的纳米工程方法可以直接应用于改进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的强结合是有效诱导检查点阻断所必需的，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)，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，这种基于抗体的疗法价格昂贵，而且经常导致令人失望的临床结果，特别是当单独使用时。该团队假设，树枝状大分子与以T细胞上多个免疫检查点受体为靶标的经过计算优化的多肽结合将显著提高其他弱结合多肽的结合强度，这反过来将使其免疫治疗效率最大化。多肽的使用将是有利的，因为与整个抗体相比，它们具有成本效益，并且易于接受各种工程策略。与其他常用的纳米给药系统相比，所提出的树枝状大分子-多肽共轭(DPC)系统由带有多肽的工程PAMAM树枝状大分子组成，相对简单。然而，DPC系统的独特和创新之处在于：i)多肽可以通过高通量计算进行调整和优化；ii)树枝状大分子使多肽多聚化以利用强大的多价结合效应(亲和力)；iii)折叠多肽可以稳定在树枝状大分子表面，进一步有助于结合增强；以及iv)这种方法几乎与任何多肽兼容，为各种组合提供了一个模块化平台。本项目成功完成后，我们将对多肽的设计/合成、聚合物工程以及DPC的结合动力学和生物学行为有了基本的了解。该项目将扩大代表不足的少数群体和妇女在不同教育水平上参与STEM研究。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.