Developing Fisetin for the Managment of Prostate Cancer

前列腺癌是美国男性中最常诊断的癌症，也是癌症相关死亡的第二大常见原因。虽然预防和治疗的进展提高了总生存率，但仍然明显需要有效的基于机制的方法，可以实现前列腺癌管理的长期改善。在前列腺癌发展中涉及的许多信号传导网络中，有PTEN/AKT/哺乳动物雷帕霉素靶蛋白（AKT/mTOR）和MAPK通路。值得注意的是，PTEN/AKT/mTOR和MAPK信号通路协同作用以促进肿瘤生长和肿瘤难治性疾病的出现。这些观察结果构成了我们提出的同时靶向PTEN/Akt/mTOR和MAPK信号通路可能是抑制前列腺上皮内瘤变（PIN）发展及其转化为癌症的有效策略的基础。根据这一假设，并在我们的追求无毒的饮食化学预防剂，我们最近取得了一些新的和令人兴奋的观察与非瑟酮，一种结构独特的化学物质，属于类黄酮组的多酚。用非瑟酮处理前列腺癌PC 3细胞导致mTOR激酶信号传导的抑制。使用模拟前列腺癌发生过程中多个步骤的独特的人类前列腺上皮细胞系家族，我们观察到具有增加的肿瘤发生潜力的转化细胞表现出更高的mTOR信号传导和对非瑟酮诱导的细胞死亡更高的敏感性。更有趣的是，使用分子建模，我们观察到非瑟酮与mTOR分子物理相互作用，并在两个位点停靠，结合能为-8Kcal/mol。这些观察结果提供了非瑟酮作为mTOR信号传导复合物的新型抑制剂的功能，导致诱导细胞死亡的证据。在本申请中，我们建议利用非瑟酮的能力，以目标多种信号通路，并研究其疗效在体外使用一个独特的家庭的六个人前列腺上皮细胞和体内使用基因工程改造的Nkx3.1/Pten突变小鼠模型，概括了人类前列腺癌的许多功能。与当前研究最相关的是，Nkx3.1/Pten突变小鼠在癌症进展期间显示AKT/mTOR和MAPK信号传导的激活。因此，我们推断这些Nkx3.1/Pten小鼠应该提供一个极好的临床前模型来测试同时靶向AKT/mTOR和ERK MAPK信号传导对前列腺肿瘤发生的后果。在本申请中，我们将1）建立PTEN/Akt/mTOR和MAPK信号通路的参与，并确定非瑟酮在模拟前列腺癌发生过程中多个步骤的独特的人前列腺上皮细胞系家族中的功效，2）研究膳食非瑟酮的作用和PTEN/Akt/前列腺癌的Nkx3.1/Pten小鼠模型中PIN和雄激素依赖性腺癌发展过程中的mTOR和MAPK信号通路，以及3）在晚期前列腺癌的Nkx3.1/Pten突变小鼠模型中研究非瑟酮对去势诱导的雄激素非依赖性腺癌的功效。该提案的成功完成可能导致非瑟酮作为预防和治疗前列腺癌的新药物的开发。

Prostate cancer is the most commonly diagnosed cancer and the second most common cause of cancer related deaths among men in the US. Although advances in prevention and treatment have improved overall survival, there remains a clear need for effective mechanism-based approaches that can achieve long-term improvements in the management prostate cancer. Among the many signaling networks that have been implicated in the development of prostate cancer are the PTEN/AKT/mammalian target of rapamycin (AKT/mTOR) and MAPK pathways. Notably, the PTEN/AKT/mTOR and MAPK signaling pathways function cooperatively to promote tumor growth and the emergence of hormone-refractory disease. These observations form the basis of our proposal that simultaneous targeting of the PTEN/Akt/mTOR and the MAPK signaling pathways may be an effective strategy for inhibiting the development of prostatic intraepithelial neoplasia (PIN) and its conversion to cancer. In line with this hypothesis and in our pursuit for non-toxic dietary agents for chemoprevention, we recently made some novel and exciting observations with fisetin, a structurally distinct chemical substance that belongs to the flavonoid group of polyphenols. Treatment of prostate cancer PC3 cells with fisetin resulted in inhibition of mTOR kinase signaling. Using a unique family of human prostate epithelial cell lines that mimic multiple steps in the process of prostate carcinogenesis we observed that transformed cells with increased potential for tumorigenesis exhibit higher mTOR signaling and greater sensitivity to fisetin induced cell death. More interestingly, using molecular modeling we observed that fisetin physically interacts with the mTOR molecule and docks at two sites with a binding energy of -8Kcal/mol. These observations provide evidence that fisetin functions as a novel inhibitor of mTOR signaling complex leading to induction of cell death. In this application we propose to take advantage of fisetin's ability to target multiple signaling pathways and investigate its efficacy in vitro using a unique family of six human prostate epithelial cells and in vivo using a genetically engineered Nkx3.1/Pten mutant mouse model that recapitulates many features of human prostate cancer. Most relevant for the current study, Nkx3.1/Pten mutant mice display activation of AKT/mTOR and MAPK signaling during cancer progression. Therefore, we reasoned that these Nkx3.1/Pten mice should provide an excellent preclinical model to test the consequences of simultaneous targeting of AKT/mTOR and ERK MAPK signaling for prostate tumorigenesis. In this application we will 1) establish the involvement of PTEN/Akt/mTOR and the MAPK signaling pathways and determine the efficacy of fisetin in a unique family of human prostate epithelial cell lines that mimic multiple steps in the process of prostate carcinogenesis, 2) investigate the effects of dietary fisetin and involvement of PTEN/Akt/mTOR and the MAPK signaling pathways during the development of PIN and androgen dependent adenocarcinoma in the Nkx3.1/Pten mouse model of prostate cancer and 3) investigate the efficacy of fisetin against castration induced androgen independent adenocarcinoma in the Nkx3.1/Pten mutant mouse model of advanced prostate cancer. A successful completion of this proposal may result in the development of fisetin as a novel agent for prevention and possibly for the treatment of prostate cancer.