Targeted Delivery of c-Myc Inhibitory Polypeptides

描述（由申请人提供）：目前实体瘤的治疗受到肿瘤对放疗或化疗的固有抗性以及全身给予化疗药物的毒性的限制。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限制，该方法增加了治疗的特异性和有效性，并降低了正常组织中的细胞毒性。c-Myc原癌基因是一种转录因子，在细胞生长和分化的调节中起着重要作用，其异常过表达与癌发生有关。我们已经开发了一种热响应多肽，其抑制c-Myc转录活性和培养中细胞的增殖。我们的假设是，在全身给药后，基因工程多肽可以通过局部热疗靶向肿瘤部位。这将导致药剂在肿瘤中积累，随后抑制肿瘤生长。所设计的多肽的氨基酸序列基于弹性蛋白样（ELP）生物聚合物，其在低于生理温度37 ℃的水溶液中可溶，但当温度升高到41 ℃以上时聚集。细胞穿透肽（CPP）与ELP缀合以促进细胞进入。向CPP-ELP添加来自c-Myc的螺旋-环-螺旋区域的肽，称为H1，其抑制c-Myc途径。我们的初步体外结果证明，当与非热响应性对照肽相比时，CPP-ELP-H1构建体在MCF 7细胞中具有非常显著的作用。为了解决这一假设，将讨论以下具体目标：（1）通过将MCF 7细胞植入无胸腺大鼠的大腿肌肉中，创建合适的动物模型以在体内测试假设，（2）测量CPP-ELP-1的血浆动力学和体内分布。通过测定血浆浓度曲线和定量放射自显影术测定组织浓度，测定无胸腺大鼠模型中正常和肿瘤组织中的H1。3）通过重复施用CPP-ELP-H1与局部热疗结合，评估CPP-ELP-H1在有和没有局部热疗的无胸腺大鼠大腿中治疗肿瘤异种移植物的治疗功效。 这些研究将为靶向递送特定癌基因抑制剂的新技术提供基础。通过局部热疗将所提出的治疗性多肽特异性靶向实体肿瘤将增加治疗的特异性和功效，并降低正常组织中的细胞毒性。因此，所提出的多肽介导的治疗递送系统的开发将提供有效替代或增强用于治疗局部肿瘤的现有疗法的替代手段。拟议研究的成功完成将提供体内数据，以将这种疗法推向人类疗法的转化阶段。

DESCRIPTION (provided by applicant): Current treatment of solid tumors is limited by inherent tumor resistance to radiation or chemotherapy and toxicity from systemic administration of antineoplastic 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. The c-Myc proto-oncogene is a transcription factor which plays a central role in the regulation of cell growth and differentiation, and its aberrant overexpression is associated with carcinogenesis. We have developed a thermally responsive polypeptide which inhibits c-Myc transcriptional activity and proliferation of cells in culture. Our hypothesis is that after systemic administration, 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 designed polypeptides is based on elastin-like (ELP) biopolymers which are soluble in aqueous solution below physiological temperature 37 degrees C, but aggregate when the temperature is raised above 41 degrees C. A cell-penetrating peptide (CPP) is conjugated to the ELP to facilitate cell entry. To the CPP-ELP is added a peptide from the helix-loop-helix region of c-Myc, called H1, which inhibits the c-Myc pathway. Our preliminary in vitro results demonstrate a very significant effect of the CPP- ELP-H1 construct in MCF7 cells when compared to a non-thermally responsive control peptide. In order to address the hypothesis, the following specific aims will be addressed: (1) Create a suitable animal model to test the hypothesis in vivo through implantation of the MCF7 cells in the thigh muscle of athymic rats, (2) Measure the plasma kinetics and in vivo distribution of CPP-ELP-H1 in normal and neoplastic tissue in an athymic rat model by determining the plasma concentration curve and determination of the tissue concentrations with quantitative autoradiography.and (3) Evaluate therapeutic efficacy of CPP-ELP-H1 in the treatment of neoplastic xenografts in the thigh of athymic rats with and without localized hyperthermia through repeated administration of the agent coupled with local hyperthermia. These studies will provide the basis for a new technology for targeted delivery of specific oncogene inhibitors. Specific targeting of the proposed therapeutic polypeptides to solid tumors by local hyperthermia would increase specificity and efficacy of treatment and reduce the cytotoxicity in normal tissues. Thus, development of the proposed polypeptide-mediated therapeutic delivery system would provide an alternative means to effectively substitute or augment present therapy for treatment of localized tumors. The successful completion of the proposed research will provide In vivo data to move this therapy towards the translational stage of human therapeutics.