Elucidation and therapeutic exploitation of PAK mediated radioresistance

项目总结/摘要 肿瘤对放疗的抵抗仍然是改善诊断为乳腺癌患者预后的关键障碍。 局部晚期无法切除的癌症细胞对电离辐射（IR）的敏感性受细胞内 和细胞外因子。为了克服肿瘤的辐射抗性，可以使用使肿瘤细胞对电离辐射敏感的药物。 辐射（IR）。与放疗同时给予的非靶向细胞毒性化疗， 在癌症患者中显示出改善的肿瘤控制和总体存活率。然而，由于这种模式 转变的方法发生在20世纪80年代，在发展分子生物学方面令人震惊地缺乏进展。 靶向放射增敏方法。提高胰岛素抵抗的治愈率 递送药物可以通过两种一般方法实现，1）使用阻断DNA损伤修复的药物 反应2）将放射增敏药物选择性地递送至肿瘤。这两种方法是正交的 技术，以实现相同的最终目标，即增加IR诱导的肿瘤杀伤，同时减少正常组织 毒性为了解决这两个基本的癌症治疗问题，我们专注于靶向治疗。 发现和肿瘤选择性药物递送载体。关于目标发现，我们最近的研究 非典型的CRAF功能导致我们发现PAK在DNA损伤修复中的意外作用， PAK由细分为组I和组II的六种激酶的家族组成。重要的是，PAK 参与肿瘤发生、肿瘤侵袭性和患者存活的中心过程。对付肿瘤 选择性药物递送，我们正在开发药物缀合的可活化细胞穿透肽（ACPP）， 基于细胞外肿瘤蛋白酶活性选择性地将有效的放射增敏剂递送至肿瘤。ACPP 由药物偶联的聚阳离子细胞穿透肽和自身抑制性聚阴离子肽组成， 通过柔性肽接头彼此分开。该肽接头被蛋白酶特异性地切割 在细胞外肿瘤微环境中富集。虽然ACPP是完整的，但药物缀合的细胞 穿透肽被聚阴离子肽中和（即保持在"前药"状态）， 无法接近其细胞内目标。肿瘤微环境蛋白酶切割ACPP并释放肿瘤微环境蛋白酶。 药物结合的细胞穿透肽，然后被肿瘤细胞吸收。我们提案的目标是 深入了解PAK如何调节放射抵抗性，然后用靶向PAK进行治疗性利用 抑制剂的在目标1中，我们将从遗传学上确定I组和II组PAK的调控机制 IR电阻。在目标2中，我们将进一步测试小分子放射增敏肿瘤的能力。 PAK抑制剂。在目标3中，我们将测试肿瘤靶向ACPP是否增加缀合PAK的治疗率 抑制剂的我们的方法在DNA损伤靶点发现和肿瘤治疗方面都有互补的创新。 选择性药物输送将这些方法结合起来，将为远离非针对性奠定基础 从细胞毒性放射增敏到生物标志物驱动的分子引导放射增敏。

PROJECT SUMMARY/ABSTRACT Tumor resistance to radiotherapy remains a critical barrier to improving outcomes for patients diagnosed with locally advanced, unresectable cancers. Cellular sensitivity to ionizing radiation (IR) is governed by intracellular and extracellular factors. To overcome tumor radioresistance, drugs that sensitize tumor cells to ionizing radiation (IR) are used. Non-targeted cytotoxic chemotherapies given concurrently with radiotherapy have demonstrated improved tumor control and overall survival in cancer patients. However, since this paradigm shifting approach occurred in the 1980's there has been a shocking lack of progress in developing molecularly targeted radiosensitization approaches. Improving the therapeutic ratio of IR in combination with systemically delivered drugs can be achieved by two general approaches, 1) using drugs that block DNA damage repair responses 2) delivering radiosensitizing drugs selectively to tumors. These two methods are orthogonal techniques to achieve the same end goal of increasing IR induced tumor kill while reducing normal tissue toxicities. To address both of these fundamental cancer therapy problems, we have focused on target discovery and tumor selective drug delivery vehicles. With regards to target discovery, our recent studies on non-canonical CRAF functions led to our discovery of an unexpected role for PAK in DNA damage repair and sensitivity to IR. PAK is comprised of a family of six kinases subdivided in Group I and II. Importantly, PAK are involved in process central to oncogenesis, tumor aggressiveness and patient survival. To tackle tumor selective drug delivery, we are developing drug conjugated activatable cell penetrating peptides (ACPP) to selectively deliver potent radiosensitizers to tumors based on extracellular tumor protease activity. ACPP consist of a drug conjugated polycationic cell penetrating peptide and an autoinhibitory polyanionic peptide separated from each other by a flexible peptide linker. This peptide linker is specifically cleaved by proteases enriched in the extracellular tumor microenvironment. While ACPP is intact, the drug conjugated cell penetrating peptide is neutralized (i.e. held in a “pro-drug” state) by the polyanionic peptide so that the drug cannot gain access to its intracellular target. Tumor microenvironment proteases cleave ACPP and release the drug conjugated cell penetrating peptide, which is then taken up by tumor cells. The goals of our proposal are to gain insight into how PAK governs radioresistance and then therapeutically exploit this with targeted PAK inhibitors. In Aim 1, we will genetically determine the mechanisms through which Group I and II PAKs govern IR resistance. In Aim 2, we will pharmacologically test the ability to radiosensitize tumors with small molecule PAK inhibitors. In Aim 3, we will test if tumor targeted ACPP increase the therapeutic ratio of conjugated PAK inhibitors. Our approach has complementary innovations in both DNA damage target discovery and tumor selective drug delivery. Combining these approaches will lay a foundation for moving away from non-targeted cytotoxic radiosensitization to biomarker driven molecularly guided radiosensitization.