Thermally Targeted Delivery of c-Myc Inhibitory Polypeptides to Malignant Gliomas

描述(申请人提供)：恶性胶质瘤是胶质瘤中最大的一类，由于其高增殖潜力、强烈的颅内扩散倾向以及传统治疗的严重不良反应，预后较差。虽然手术切除辅以化疗和/或放射治疗是治疗恶性胶质瘤的有效方法，但肿瘤对放化疗的固有抵抗力以及全身应用抗肿瘤药物的毒性往往阻碍了治疗的成功。因此，受目前胶质瘤治疗方法局限性的驱使，我们的长期目标是开发一种针对局部肿瘤的靶向治疗方法，以提高治疗的特异性和有效性，并降低对正常组织的细胞毒性。我们已经开发出一种热响应多肽(CPP-ELP-H1)，它可以抑制c-Myc转录活性和恶性胶质瘤细胞的增殖。这项研究的目的是证明，在体内全身给药后，这些基因工程多肽可以通过局部热疗靶向脑肿瘤部位，并抑制肿瘤生长。热响应性多肽的氨基酸序列是以类弹性蛋白(ELP)生物聚合物为基础的，ELP生物聚合物在生理温度(370℃)以下可溶于水溶液，但当温度高于410℃时会聚集。一种细胞穿透性多肽(CPP)，芽孢菌素(Bac)或Tat，连接到ELP上，以促进多肽通过血脑屏障的输送，并促进细胞进入。在CPP-ELP中添加了一种源自c-Myc螺旋-环-螺旋域的螺旋1(H1)的肽，它抑制c-Myc的转录激活，从而抑制癌细胞的增殖。我们的假设是，在生理条件下(37℃)，静脉递送的热响应性c-Myc抑制多肽可能被清除。然而，它们会在大鼠脑内生长的胶质瘤中积累，在那里将施加外部诱导的局部热(40-420摄氏度)。积聚的多肽将阻断c-Myc的活性，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)测定CPP-ELP-H1在正常组织和肿瘤组织中的血浆动力学和体内分布；(2)通过反复给予CPP-ELP-H1联合局部加温和不加局部加温，评价CPP-ELP-H1对大鼠肿瘤的治疗效果。这项拟议研究的成功完成将提供第一个证据，证明ELP可以提供治疗分子，并以热靶向方式缩小脑瘤大小，这项工作将获得必要的毒性、药代动力学、生物分布和疗效数据，以推动这项技术朝着人类治疗的最终目标迈进。因此，提出的研究可能会产生重大影响，将这项技术带入临床试验，并可能为治疗和管理脑肿瘤提供强大的技术。 公共卫生相关性：胶质母细胞瘤是最常见和最具侵袭性的原发脑肿瘤。尽管包括手术、放疗和化疗在内的综合治疗方案取得了进展，但由于治疗药物对血脑屏障的穿透能力差、对化疗药物的耐药性以及正常组织中的非特异性细胞毒作用，胶质母细胞瘤的诊断预后仍然黯淡。鉴于目前治疗胶质母细胞瘤的方法的局限性，本研究的目的是开发一种可通过局部热疗靶向脑肿瘤部位并抑制其生长的热响应性治疗性多肽。

DESCRIPTION (provided by applicant): Malignant gliomas represent the largest group of glial tumors, and they have a poor prognosis because of their high proliferation potential, strong tendency for intracranial dissemination, and the severe adverse effects of conventional therapies. Although surgical resection with adjuvant chemotherapy and/or radiotherapy is used to treat malignant gliomas, inherent tumor resistance to radiation or chemotherapy and toxicity from systemic administration of antineoplastic agents often hinders a successful outcome. Therefore, motivated by the limitations of current therapeutic approaches for gliomas, our long term goal is to develop 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 (CPP-ELP-H1) that inhibits c-Myc transcriptional activity and malignant glioma cell proliferation. The objective of the proposed research is to demonstrate that after systemic administration in vivo, these genetically engineered polypeptides can be targeted to the brain tumor site by applying local hyperthermia and inhibit tumor growth. The amino acid sequence of the thermally responsive polypeptides is based on the elastin-like (ELP) biopolymer, which is soluble in aqueous solution below physiological temperature (37 0C), but aggregates when the temperature is raised above 41 0C. A cell-penetrating peptide (CPP), Bactenecin (Bac) or Tat, is conjugated to the ELP to enhance delivery of the polypeptide across the blood brain barrier and to facilitate cell entry. To the CPP-ELP is added a peptide derived from helix 1 (H1) of the helix-loop-helix domain of c-Myc, which inhibits transcriptional activation by c-Myc and consequently inhibits cancer cell proliferation. Our hypothesis is that intravenously delivered thermally responsive c-Myc inhibitory polypeptides are likely to be cleared under physiological conditions (37 0C). However, they will accumulate in gliomas grown in rat brains, where externally induced local heat (40-42 0C) will be applied. The accumulated polypeptides will block c-Myc activity 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 CPP-ELP-H1 in normal and neoplastic tissue and (2) evaluate the therapeutic efficacy of CPP-ELP-H1 in the treatment of neoplastic brain tumors in rats through repeated administration of the agent coupled with and without local hyperthermia. Successful completion of the proposed study will provide the first evidence that ELP can deliver a therapeutic molecule and reduce brain tumor size in a thermally targeted manner, and this work will obtain the necessary toxicity, pharmacokinetic, biodistribution, and efficacy data necessary to advance this technology toward the ultimate goal of human therapeutics. Therefore, proposed research may have a significant impact, leading this technology into clinical trials, and it may provide a powerful technology to treat and manage brain tumors. PUBLIC HEALTH RELEVANCE: Glioblastoma is the most common and most aggressive of the primary brain tumors. Despite advances in combined treatment regimens including surgery, radio- and chemotherapy, the prognosis of a glioblastoma diagnosis is still bleak due to poor blood- brain barrier penetration of therapeutics, resistance to chemotherapeutic agents and nonspecific cytotoxicity in normal tissues. Motivated by the limitations of current therapeutic approaches for treatment of glioblastoma, the objective of the proposed research is to develop a thermally responsive therapeutic polypeptide which can be targeted to the brain tumor site by applying local hyperthermia and inhibit its growth.