A Novel Synthetic Androgen Receptor Antagonist

描述（由申请人提供）：由于雄激素非依赖性生长的发展，目前的激素消融疗法是晚期前列腺癌的主要治疗方法，是姑息性的。雄激素受体（AR）在大多数前列腺癌细胞中表达，并且AR的AR过表达对于雄激素非依赖性生长是足够和必要的，这为通过下调AR来开发针对晚期前列腺癌的新疗法提供了强有力的理论基础。Dong博士的实验室已经鉴定了一种新的合成化合物6-氨基-2-[2-（4-叔丁基-苯氧基）-乙基硫基]-1H-嘧啶-4-酮，为简单起见命名为DL 3，作为一种有效的AR拮抗剂。DL 3在所有测试的前列腺癌细胞系中抑制二氢睾酮（DHT）刺激的细胞生长和基因表达，包括雄激素非依赖性细胞和对抗雄激素、氟替卡松（Flut）或尼鲁米特（Nilut）耐药的细胞。DL 3的抑制作用比比卡鲁胺（Bical）、Flut和Nilut更强。它既不抑制AR核定位，也不抑制DHT诱导的AR NH 2-末端和COOH-末端相互作用，并且没有可检测到的AR激动剂活性。DL 3降低AR稳定性并下调AR蛋白表达。它与DHT竞争结合细胞，但不与雌二醇竞争结合细胞。使用AR配体结合结构域（LBD）的蛋白质晶体结构的对接分析暗示DL 3可以结合LBD。这些观察结果促使Dong博士假设DL 3是一种新的AR拮抗剂，其结合AR并诱导非活性AR转录机制的形成和AR降解，从而中断AR信号传导。提出了三个具体的目标来检验假设，并研究DL 3疗法对动物中的人前列腺癌细胞的功效。在具体目标1中，他将表征DL 3与AR的结合并鉴定DL 3结合位点的氨基酸残基。他将确定结合的生化特性，调查DL 3是否与DHT竞争AR结合，并确定与DL 3相互作用的AR氨基酸残基。在具体目标2中，他将研究DL 3对蛋白体介导的AR降解和AR转录复合物组装的影响。他将确定DL 3和Bical对AR稳定性，泛素化以及与E3泛素连接酶的关系的影响。通过使用染色质免疫沉淀（ChIP）试验，他将研究DL 3和Bical治疗是否诱导在前列腺特异性抗原基因启动子区域形成转录失活的AR复合物，并鉴定复合物中的辅助因子。在具体目标3中，Dong博士提出研究DL 3对小鼠中的人前列腺癌细胞的治疗效果。他将确定和比较DL 3和Bical单独或与去势联合对雄激素依赖性和非依赖性细胞以及Flut难治性细胞形成的肿瘤生长的影响。他将确定DL 3在荷瘤小鼠中的分布，并将治疗效果与肿瘤中AR和AR靶基因的表达相关联。这些研究将坚定地确定DL 3是一种新型AR拮抗剂，并将丰富对Bical中断AR信号传导机制的理解。我们的初步研究已经鉴定了一种新的合成化合物6-氨基-2-[2-（4-叔丁基-苯氧基）-乙硫基]-1H-嘧啶-4-酮，为简单起见命名为DL 3。DL 3竞争性抑制DHT与人前列腺癌细胞的结合，但不抑制雌二醇与人乳腺癌细胞的结合。它下调雄激素受体的表达，并抑制雄激素诱导的前列腺癌细胞的细胞生长和基因表达。拟议的研究将确定DL 3是一种新型AR拮抗剂，将阐明DL 3中断AR信号传导的机制，并将确定DL 3对小鼠人前列腺癌细胞的治疗效果。 公共卫生相关性：我们的初步研究鉴定了一个新的合成化合物6-氨基-2-[2-（4-叔丁基-苯氧基）-乙硫基]-1H-嘧啶-4-酮，为简单起见命名为DL 3。DL 3竞争性抑制DHT与人前列腺癌细胞的结合，但不抑制雌二醇与人乳腺癌细胞的结合。它下调雄激素受体的表达，并抑制雄激素诱导的前列腺癌细胞的细胞生长和基因表达。拟议的研究将确定DL 3是一种新型AR拮抗剂，将阐明DL 3中断AR信号传导的机制，并将确定DL 3对小鼠人前列腺癌细胞的治疗效果。

DESCRIPTION (provided by applicant): Current hormonal ablation therapy, the mainstay treatment for advance prostate cancer, is palliative, due the development of androgen-independent growth. Androgen receptor (AR) is expressed in most prostate cancer cells and AR overexpression of AR is sufficient and necessary for androgen-independent growth, which provides strong rationale for developing novel therapies against advanced prostate cancer through downregulation of AR. Dr. Dong's laboratory has identified a novel synthetic compound 6-amino-2-[2-(4-tert- butyl-pnenoxy)-ethylsulfanyl]-1H-pyrimidin-4-one, named DL3 for simplicity, as a potent AR antagonist. DL3 inhibits dihydrotestosterone (DHT)-stimulated cell growth and gene expression in all prostate cancer cell lines tested, including androgen-independent cells and cells resistant to antiandrogens, flutamide (Flut) or nilutamide (Nilut). The inhibitory effects of DL3 are more potent than bicalutamide (Bical), Flut, and Nilut. It inhibits neither AR nuclear localization nor DHT-induced AR NH2-terminus and COOH-terminus interaction and has no detectable AR agonist activity. DL3 reduces AR stability and downregulates of AR protein expression. It competes with DHT but not estradiol for the binding to cells. Docking analysis using protein crystal structure of AR ligand-binding domain (LBD) implies that DL3 can bind to the LBD. These observations prompted Dr. Dong to hypothesize that DL3 is a novel AR antagonist that binds to AR and induces the formation of inactive AR transcription machinery and AR degradation, and, hence, interrupts AR signaling. Three specific aims are proposed to test the hypothesis and to investigate efficacy of DL3 therapy against human prostate cancer cells in animals. In the specific aim 1, he will characterize the binding of DL3 to AR and identify amino acid residues of the DL3 binding site. He will determine the biochemical properties of the binding, investigate whether DL3 competes with DHT for AR binding, and identify amino acid residues of AR that interact with DL3. In the specific aim 2, he will investigate effects of DL3 on proteosome-mediated degradation of AR and assembly of AR transcription complex. He will determine effects of DL3 and Bical on AR stability, ubiquitination, and association with E3 ubiquitin ligase. By using the chromatin immunoprecipitation (ChIP) assay, he will investigate whether treatment with DL3 and Bical induce formation of transcription-inactive AR complex at the promoter region of prostate-specific antigen gene and identify cofactors in the complex. In the specific aim 3, Dr. Dong propose to investigate therapeutic effects of DL3 against human prostate cancer cells in mice. He will determine and compare effects of DL3 and Bical, alone or in combination with castration, on growth of tumors formed by both androgen-dependent and -independent cells and by cells refractory to Flut. He will determine DL3 distribution in tumor-bearing mice and correlate therapeutic effects with expression of AR and AR-target genes in tumors. These studies will firmly establish that DL3 is a novel AR antagonist and will enrich the understanding of mechanisms by which Bical interrupts AR signaling. Project Narrative Our preliminary studies have identified a novel synthetic compound 6-amino-2-[2-(4-tert- butyl-pnenoxy)-ethylsulfanyl]-1H-pyrimidin-4-one, named DL3 for simplicity. DL3 competitively inhibits the binding of DHT to human prostate cancer cells, but not estradiol to human breast cancer cells. It downregulates androgen receptor expression and suppresses androgen-induced cell growth and gene expression in prostate cancer cells. The proposed research will establish that DL3 is a novel AR antagonist, will elucidate mechanisms by which DL3 interrupts AR signaling, and will determine therapeutic effects of DL3 against human prostate cancer cells in mice. PUBLIC HEALTH RELEVANCE: Our preliminary studies have identified a novel synthetic compound 6-amino-2-[2-(4-tertbutyl-pnenoxy)-ethylsulfanyl]-1H-pyrimidin-4-one, named DL3 for simplicity. DL3 competitively inhibits the binding of DHT to human prostate cancer cells, but not estradiol to human breast cancer cells. It downregulates androgen receptor expression and suppresses androgen-induced cell growth and gene expression in prostate cancer cells. The proposed research will establish that DL3 is a novel AR antagonist, will elucidate mechanisms by which DL3 interrupts AR signaling, and will determine therapeutic effects of DL3 against human prostate cancer cells in mice.