Thermally Targeted Delivery of Therapeutic Peptides

描述（由申请人提供）：目前实体肿瘤的治疗受到正常组织耐受性、肿瘤对放疗或化疗的固有抵抗力以及全身使用抗肿瘤药物的毒性的限制。结果是目前大多数化疗药物的治疗指标很窄。我们的长期目标是通过开发针对局部肿瘤的靶向治疗方法来克服这些局限性，从而提高治疗的特异性和有效性，并降低正常组织中的细胞毒性。我们已经开发了一种热反应多肽，它可以抑制细胞周期的进展和癌细胞在细胞培养中的增殖。本研究的目的是证明在全身给药后，这些基因工程多肽可以通过局部热疗靶向肿瘤部位。这将导致药物在肿瘤中的积累，随后抑制肿瘤生长。热响应多肽的氨基酸序列是基于类弹性蛋白（ELP）生物聚合物，在低于生理温度（37℃）的水溶液中可溶，但当温度升高到41℃以上时聚集。一种细胞穿透肽，Bactenecin （Bac）与ELP结合以促进细胞进入。在Bac-ELP上添加了一种从细胞周期蛋白依赖性激酶抑制剂p21中提取的肽，它可以抑制细胞周期。我们的初步体外实验结果表明，与非热反应性对照肽相比，Bac-ELP-p21构建物在Mat BIII大鼠乳腺腺癌细胞中具有非常显著的作用。我们的假设是，静脉注射的热反应性细胞周期抑制多肽可能在生理条件下（37℃）被清除。然而，它们会在乳房肿瘤中积聚，在那里，外部诱导的局部加热（40-42℃）将被应用。积累的多肽会抑制细胞周期，从而抑制癌细胞的增殖。为了解决这一假设，将解决以下具体目标：(1)测量正常组织和肿瘤组织中Bac-ELP-p21的血浆动力学和体内分布；(2)通过反复给药结合或不局部热疗来评估Bac-ELP-p21治疗大鼠乳腺肿瘤的治疗效果。拟议研究的成功完成将为一种比现有/替代技术具有竞争优势的新技术提供基础。这些研究将提供必要的体内数据，将这种疗法推向人类治疗的转化阶段。通过局部热疗将所提出的治疗多肽特异性靶向实体瘤，可以提高癌症治疗的疗效，降低正常组织中的细胞毒性，为局部肿瘤的治疗提供替代或增强现有治疗方法的替代手段。

DESCRIPTION (provided by applicant): Current treatment of solid tumors is limited by normal tissue tolerance, inherent tumor resistance to radiation or chemotherapy, and toxicity from systemic administration of antineoplastic agents. The result is a narrow therapeutic index for most current chemotherapeutic agents. Our long term goal is to overcome these limitations by developing a targeted therapeutic approach for localized tumors that increases the specificity and efficacy of the therapy and reduces the cytotoxicity in normal tissues. We have developed a thermally responsive polypeptide which inhibits cell cycle progression and proliferation of cancer cells in cell culture. The objective of the proposed research is to demonstrate that after systemic administration, these genetically engineered polypeptides can be targeted to the tumor site by applying local hyperthermia. This will results in accumulation of the agent in the tumor with subsequent inhibition of tumor growth. The amino acid sequence of the thermally responsive polypeptides is based on elastin-like (ELP) biopolymers, which are soluble in aqueous solution below physiological temperature (37 oC), but aggregate when the temperature is raised above 41 oC. A cell-penetrating peptide, Bactenecin (Bac) is conjugated to the ELP to facilitate cell entry. To the Bac-ELP is added a peptide derived from the cyclin- dependent kinase inhibitor p21, which inhibits the cell cycle. Our preliminary in vitro results demonstrate a very significant effect of the Bac-ELP-p21 construct in Mat BIII rat mammary adenocarcinoma cells when compared to a non-thermally responsive control peptide. Our hypothesis is that intravenously delivered thermally responsive cell cycle inhibitory polypeptides are likely to be cleared under physiological conditions (37 oC). However, they will accumulate in breast tumors, where externally induced local heat (40-42 oC) will be applied. The accumulated polypeptides will inhibit the cell cycle and consequently inhibit proliferation of the cancer cells. In order to address this hypothesis, the following specific aims will be addressed: (1) measure the plasma kinetics and in vivo distribution of Bac-ELP-p21 in normal and neoplastic tissue and (2) evaluate the therapeutic efficacy of Bac-ELP-p21 in the treatment of breast tumor in rats through repeated administration of the agent coupled with and without local hyperthermia. The successful completion of the proposed research will provide the basis for a new technology that has a competitive advantage over existing/alternate technologies. These studies will provide the in vivo data necessary to move this therapy towards the translational stage of human therapeutics. Specific targeting of the proposed therapeutic polypeptides to solid tumors by local hyperthermia would increase efficacy of the cancer treatment and reduce the cytotoxicity in normal tissues, and it would provide an alternative means to substitute or augment present therapy for treatment of localized tumors. PUBLIC HEALTH RELEVANCE: Current treatment of solid tumors is limited because only a small fraction of the administered dose of drug reaches the tumor site while the rest of the drug is distributed throughout the body. This causes undesirable side effects to normal tissues when drugs are used in the doses required to eradicate cancer cells. Our long term goal is to overcome this limitation by developing an approach that allows the therapeutics to be delivered specifically to the tumor site. This will increase the specificity of the therapy and reduce the toxicity in normal tissues.