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

描述（申请人提供）：恶性胶质瘤是神经胶质肿瘤中最大的一类，其增殖潜力高，颅内播散倾向强，常规治疗不良反应严重，预后较差。虽然手术切除配合辅助化疗和/或放疗用于治疗恶性胶质瘤，但肿瘤固有的对放疗或化疗的耐药性以及全身使用抗肿瘤药物的毒性往往阻碍了成功的结果。因此，鉴于目前胶质瘤治疗方法的局限性，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，并降低正常组织中的细胞毒性。我们开发了一种热响应多肽（cppp - elp - h1），可抑制c-Myc转录活性和恶性胶质瘤细胞增殖。本研究的目的是证明在体内系统给药后，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。热响应多肽的氨基酸序列基于弹性蛋白样（ELP）生物聚合物，在生理温度（37℃）以下可溶于水溶液，但当温度升高到41℃以上时聚集。一种细胞穿透肽（CPP）， Bactenecin （Bac）或Tat与ELP结合，以增强多肽穿过血脑屏障的传递，并促进细胞进入。在CPP-ELP上添加了一种源自c-Myc螺旋-环-螺旋结构域的螺旋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，静脉注射的热反应性c-Myc抑制多肽可能在生理条件下被清除（37℃）。然而，它们会在大鼠大脑中生长的胶质瘤中积累，在那里，外部诱导的局部加热（40-42℃）将被应用。积累的多肽会阻断c-Myc的活性，从而抑制癌细胞的增殖。为了验证这一假设，我们将研究以下具体目标：(1)测量正常组织和肿瘤组织中CPP-ELP-H1的血浆动力学和体内分布；(2)通过反复给药并联合局部热疗和不联合局部热疗来评估CPP-ELP-H1治疗大鼠肿瘤的疗效。该研究的成功完成将提供第一个证据，证明ELP可以以热靶向的方式传递治疗分子并减小脑肿瘤大小，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，从而将该技术推向人类治疗的最终目标。因此，拟议的研究可能会产生重大影响，使这项技术进入临床试验，并可能为治疗和管理脑肿瘤提供强有力的技术。

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.