Thermally Targeted Cell Cycle Inhibitors for the Treatment of Pancreatic Cancer

描述（由申请人提供）：手术切除，然后是化疗和/或放疗，是治疗胰腺癌最常用的治疗方式。然而，目前局部胰腺癌的治疗受到正常组织耐受性和/或肿瘤对放疗或化疗固有耐药性的限制，导致治疗指数较低。为了克服这些局限性，我们的目标是开发一种针对局限性胰腺癌的靶向治疗方法，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。我们设计了一种热响应多肽，它能在细胞培养中阻断细胞周期进程，诱导细胞凋亡，抑制胰腺癌的增殖。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，并抑制胰腺肿瘤的生长。热响应多肽的氨基酸序列是基于弹性蛋白样多肽（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Bactenecin （Bac）与ELP结合以促进细胞进入，并添加一种从细胞周期蛋白依赖性激酶抑制剂p21衍生的肽来抑制细胞周期。我们的体外实验结果表明，Bac-ELP-p21是一种有效的胰腺癌细胞增殖抑制剂。我们的假设是，静脉注射的Bac-ELP-p21在生理条件下（37℃）会从循环中清除，但在外部诱导的局部加热（42℃）条件下，会在小鼠生长的胰腺肿瘤中积累。积累的多肽会抑制细胞周期，诱导细胞凋亡，从而抑制癌细胞的增殖。为了验证这一假设，我们将进行以下具体的研究：(1)测量Bac-ELP-p21在正常和肿瘤组织中的血浆动力学和体内分布；(2)通过反复给药和局部热疗来评估Bac-ELP-p21治疗小鼠胰腺肿瘤异种移植物的疗效。拟议研究的成功完成将提供必要的体内数据，以建立一种比现有/替代治疗胰腺癌的技术具有竞争优势的新技术。所提出的治疗多肽通过局部热疗特异性靶向胰腺肿瘤，相对于现有药物，可以提高疗效，减少副作用，为局部胰腺癌的治疗提供替代或增强现有治疗的手段。

DESCRIPTION (provided by applicant): Surgical resection, followed by chemotherapy and/or radiotherapy, is the most common therapeutic modalities used to treat pancreatic cancer. However, current treatment of localized pancreatic cancer is limited by normal tissue tolerance and/or inherent tumor resistance to radiation or chemotherapy, resulting in a low therapeutic index. To overcome these limitations, our goal is to develop a targeted therapeutic approach for localized pancreatic cancer that increases the specificity and efficacy of the therapy and reduces the cytotoxicity in normal tissues. We have designed a thermally responsive polypeptide which blocks cell cycle progression, induces apoptosis, and inhibits proliferation of pancreatic cancer 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 and can inhibit pancreatic tumor growth. The amino acid sequence of the thermally responsive polypeptides is based on elastin-like polypeptide (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, and a peptide derived from the cyclin-dependent kinase inhibitor p21 is added to inhibit the cell cycle. Our in vitro results demonstrate that Bac-ELP-p21 is a potent inhibitor of pancreatic cancer cell proliferation. Our hypothesis is that intravenously delivered Bac-ELP-p21 will be cleared from circulation under physiological conditions (37 oC), but will accumulate in pancreatic tumors grown in mice where externally induced local heat (42 oC) will be applied. The accumulated polypeptides will inhibit the cell cycle, induce apoptosis, and consequently inhibit proliferation of the cancer cells. In order to address this hypothesis, the following specific aims will be pursued: (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 pancreatic tumor xenografts in mice through repeated administration of the agent coupled with local hyperthermia. The successful completion of the proposed research will provide the in vivo data necessary to establish a new technology that has a competitive advantage over existing/alternate technologies for treatment of pancreatic cancer. Specific targeting of the proposed therapeutic polypeptides to pancreatic tumors by local hyperthermia would improve the efficacy and reduce the side effects relative to current drugs, and it would provide a means to substitute or augment present therapy for treatment of localized pancreatic cancer. PUBLIC HEALTH RELEVANCE: Current treatment of solid tumors is limited because only a small fraction of the administered drug dose 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 and reduce toxicity in normal tissues by developing an approach to specifically deliver therapeutics to the tumor site.