Thermally Triggered Multivalent Targeting of Tumors

描述（由申请人提供）：这一竞争性NIH R01更新申请的总体目标是创建一种肿瘤靶向细胞穿透肽（CPP）纳米级药物递送系统，以靶向治疗各种实体肿瘤的有效载荷。这一建议建立在低精氨酸肽在其细胞渗透能力中表现出很强的阈值效应的观察基础上；低于CPP中连续6个精氨酸（Arg）残基的阈值，很少观察到细胞摄取，而超过这个阈值的Arg残基数，细胞摄取显著。我们假设这种阈值效应与低精氨酸CPP中顺序Arg残基的数量无关，而是反映了局部Arg残基密度。该假设预测，双嵌段共聚物的触发自组装，在其亲水端呈现< 6个精氨酸残基，形成胶束，应该提供一个显示数字的系统

DESCRIPTION (provided by applicant): The overall goal of this competing NIH R01 renewal application is to create a tumor-targeted cell-penetrating peptide (CPP) nanoscale drug delivery system to target therapeutic payloads to a wide range of solid tumors. This proposal builds upon the observation that oligoarginine peptides display a strong threshold effect in their cell penetration ability; below a threshold of 6 consecutive arginine (Arg) residues in the CPP, little cell uptake is observed, while above this threshold number of Arg residues, there is significant cell uptake. We hypothesized that this threshold effect is not related to the number of sequential Arg residues in the oligoarginine CPP, but instead is reflective of the local Arg residue density. This hypothesis predicts that the triggered self-assembly of a diblock copolymer, that presents < 6 Arg residues on its hydrophilic end, into a micelle should provide a system that exhibits digital "off-on" cell uptake. To test this hypothesis and develop an externally triggered CPP drug delivery system, thermally responsive diblock copolymers of an elastin-like polypeptide (ELPBCs) will be synthesized such that the number of Arg residues on the hydrophilic terminus of the ELPBC will be below the threshold required for efficient cellular uptake of ELPBC unimers at 37 ¿C. In tumors that are externally heated to 39-42 ¿C, which is greater than the critical micellization temperature of the ELPBC, the ELPBC will self-assemble into micelles decorated with Arg residues, and the local Arg residue density in the corona of the ELPBC will exceed the threshold required for efficient cellular uptake, thereby resulting in efficient intracellular uptae within the tumor. Arg-presenting ELPBC with a range of architectural variables will be synthesized, tested for self-assembly and stability between 39 and 42 ¿C in serum, and their temperature-triggered cellular uptake will be quantified by flow cytometry and visualized by fluorescence microscopy. Optimal Arg-presenting ELPBC selected from these studies will then be tested for their pharmacokinetics, tissue distribution and their ability to regress tumors, when they are fused to gemcitabine that is sequestered within the core of the ELPBC micelles. The significance of this proposal is that it will provide a receptor independent method of actively targeting tumors that is applicable to a broad range of cancer types and circumvents the limitations of receptor targeting; furthermore this targeting modality piggybacks on to existing hyperthermia technology, so that it can be readily deployed in the clinic. The drug carrier design presented here is innovative because it is, to our knowledge, the first attempt to control cellular uptake of cancer therapeutics by manipulating the local density of Arg residues on a nanoscale scaffold by externally triggered self-assembly under clinically relevant conditions.