Translating Novel Antitumor Targets of Vitamin E into New Chemopreventive Agents

将维生素 E 的新型抗肿瘤靶点转化为新型化学预防剂

• 批准号: 8698025
• 负责人: CHING-SHIH CHEN
• 金额: $ 31.93万
• 依托单位: OHIO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8698025
• 关键词: Adenocarcinoma; Affinity; Androgen Receptor; Androgens; Animal Model; Binding; Biological Markers; Boxing; CWR22Rv1; Cancer Etiology; Cell Proliferation; Cells; Cessation of life; Chemopreventive Agent; Chromans; Clinic; Clinical Management; Data; Defect; Development; Disease; Evaluation; Exhibits; Generations; Glycogen Synthase Kinase 3; Goals; Growth; Head; Hydrogen Bonding; Knock-out; LNCaP; Lead; Leucine-Rich Repeat; Ligands; Light; Malignant neoplasm of prostate; Mediating; Membrane; Modeling; Molecular; Molecular Models; Mus; Nude Mice; Oxidation-Reduction; PH Domain; PTEN gene; Peptides; Pharmaceutical Preparations; Phosphoric Monoester Hydrolases; Play; Prevention strategy; Prostate; Prostatic Neoplasms; Protein Dephosphorylation; Protein phosphatase; Receptor Inhibition; Receptor Signaling; Regulation; Relative (related person); Research; Role; Second Primary Cancers; Side; Signal Transduction; Structure; Tocopherols; Toxic effect; Transgenic Animals; Transgenic Organisms; Translating; Tumor Suppressor Proteins; Vertebral column; Vitamin E; analog; base; cancer cell; cancer diagnosis; improved; in vivo; inhibitor/antagonist; men; molecular modeling; mutant; novel; phosphatidylinositol 3,4,5-triphosphate; pre-clinical; prostate cancer cell; prostate carcinogenesis; public health relevance; research study; scaffold; tool; transcription factor; tumor; tumor growth; tumor progression; tumor xenograft

DESCRIPTION (provided by applicant): This project is based on the PI's novel finding that -tocopherol and, to a greater extent, -tocopherol facilitate the selective dephosphorylation of Akt at Ser-473 through PH domain-mediated membrane co- localization of Akt and PHLPP1 (PH domain leucine-rich repeat phosphatase 1). PHLPP1, a Ser-473 Akt phosphatase, acts as a tumor suppressor by negatively regulating Akt. From a mechanistic perspective, these findings provide the first evidence that -/ -tocopherol mediates redox-independent antitumor effects, at least in part, by counteracting the effect of phosphatidylinositol 3,4,5-trisphosphate on Akt activation. This unique mechanism provides a paradigm shift with respect to the regulation of Akt activity through membrane recruitment of PHLPP1, sheds light onto the enigma of how vitamin E mediates its chemopreventive effect and of why -tocopherol is more potent relative to the counterpart in suppressing cancer cell proliferation. In light of the tumor suppressor role of PHLPP in blocking PTEN mutant prostate carcinogenesis, this finding provides a molecular rationale for the use of -tocopherol as a scaffold to develop a novel class of PHLPP1-targeted Akt inhibitors, which have a distinct mode of action from other types of Akt inhibitors. The proof-of-concept of this lead optimization is provided by -VE5, a side chain-truncated -tocopherol derivative, which exhibited at least 20-fold higher potency relative to -tocopherol in mediating Akt dephosphorylation and growth inhibition of prostate cancer cells. Equally important, -VE5 exhibited in vivo efficacy in suppressing the growth of PTEN- deficient PC-3 and LNCaP-abl xenograft tumors in nude mice. Thus, this proposal consists of three specific aims with the goal of translating this novel mechanistic finding into a novel class of PHLPP1-targeted Akt inhibitors to block or delay the onset of prostate tumorigenesis. Aim 1 is to conduct structure-based lead optimization of -VE5 to develop more potent PHLPP1-targeted Akt inhibitors. Based on modeling and mutational analyses, we hypothesize that increasing polar interactions of the ligand with the hydrophilic residues in the binding pocket will enhance binding affinity for the PH domain. Proof-of-concept of this premise has been established by analysis of lead -VE5 derivatives. Continued optimization of these leads to generate 2nd generation compounds via isosteric replacement of metabolically labile moieties is proposed. Aim 2 is to investigate the mechanisms by which optimized -VE5 derivatives inhibit cell proliferation of PTEN-deficient prostate cancer cells. The top 3 optimal -VE5 derivatives from Aim 1 will be mechanistically validated by examining their effects on the activation status of Akt and various Akt downstream targets relevant to prostate carcinogenesis and tumor progression, especially glycogen synthase kinase (GSK)3¿, the forkhead box transcription factor Foxo3a, NF-¿B, and AR signaling. As PHLPP1 plays a pivotal role in mediating the effect of AR inhibition on Akt activation in PTEN- deficient prostate cancer cells, the effects of these compounds on crosstalk of AR signaling with PHLPP1- mediated regulation of Akt activation will also be explored. In vivo efficacy of three optimal -VE5 derivatives will be evaluated in both PTEN-deficient (LNCaP-abl and PC-3) and PTEN-functional (22RV1) xenograft tumor models, which will be correlated with changes in the aforementioned biomarkers in tumors. Aim 3 is to assess the in vivo chemopreventive efficacy of a structurally optimized -VE5 derivative to block prostate tumorigenesis in the PTEN-knockout and TRAMP models. In light of the role of aberrant Akt signaling in prostate carcinogenesis, these two transgenic animal models represent therapeutically relevant models to evaluate the chemopreventive activities of these -VE5-derived PHLPP1-targeted Akt inhibitors.

描述（由申请人提供）：该项目基于 PI 的新发现，即 α-生育酚以及更大程度上的 α-生育酚通过 PH 结构域介导的 Akt 和 PHLPP1（PH 结构域富含亮氨酸重复磷酸酶 1）的膜共定位促进 Akt Ser-473 选择性去磷酸化。 PHLPP1 是一种 Ser-473 Akt 磷酸酶，通过负向调节 Akt 发挥肿瘤抑制因子的作用。从机制角度来看，这些发现提供了第一个证据，证明 -/ -生育酚至少部分通过抵消磷脂酰肌醇 3,4,5-三磷酸对 Akt 激活的影响来介导不依赖于氧化还原的抗肿瘤作用。这种独特的机制为通过 PHLPP1 的膜募集来调节 Akt 活性提供了范式转变，揭示了维生素 E 如何介导其化学预防作用以及为什么生育酚在抑制癌细胞增殖方面相对于对应物更有效的谜团。鉴于 PHLPP 在阻断 PTEN 突变型前列腺癌发生中的肿瘤抑制作用，这一发现为使用 α-生育酚作为支架来开发一类新型 PHLPP1 靶向 Akt 抑制剂提供了分子原理，该抑制剂具有与其他类型 Akt 抑制剂不同的作用模式。这种先导优化的概念验证是由 -VE5 提供的，-VE5 是一种侧链截短的 生育酚衍生物，在介导 Akt 去磷酸化和前列腺癌细胞生长抑制方面，其效力比 生育酚高出至少 20 倍。同样重要的是，-VE5 在抑制裸鼠体内 PTEN 缺陷的 PC-3 和 LNCaP-abl 异种移植肿瘤的生长方面表现出体内功效。 因此，该提案包含三个具体目标，旨在将这一新机制发现转化为一类新型 PHLPP1 靶向 Akt 抑制剂，以阻止或延迟前列腺肿瘤发生。目标 1 是对 -VE5 进行基于结构的先导化合物优化，以开发更有效的 PHLPP1 靶向 Akt 抑制剂。基于建模和突变分析，我们假设增加配体与结合口袋中亲水残基的极性相互作用将增强对 PH 的结合亲和力 领域。通过对先导-VE5 衍生物的分析，已经建立了这一前提的概念验证。建议继续优化这些先导化合物，通过代谢不稳定部分的等排取代来生成第二代化合物。目标2是研究优化的-VE5衍生物抑制PTEN缺陷型前列腺癌细胞增殖的机制。 Aim 1 的前 3 种最佳 -VE5 衍生物将通过检查它们对 Akt 激活状态和与前列腺癌发生和肿瘤进展相关的各种 Akt 下游靶标的影响进行机械验证，特别是糖原合酶激酶 (GSK)3¿、叉头盒转录因子 Foxo3a、NF-¿B 和 AR 信号传导。由于PHLPP1在介导PTEN缺陷前列腺癌细胞中AR抑制对Akt激活的影响中发挥着关键作用，因此还将探讨这些化合物对AR信号传导与PHLPP1介导的Akt激活调节的串扰的影响。将在 PTEN 缺陷（LNCaP-abl 和 PC-3）和 PTEN 功能性（22RV1）异种移植肿瘤模型中评估三种最佳 -VE5 衍生物的体内功效，这将与肿瘤中上述生物标志物的变化相关。目标 3 是评估结构优化的 -VE5 衍生物在 PTEN 敲除和 TRAMP 模型中阻断前列腺肿瘤发生的体内化学预防功效。鉴于异常 Akt 信号传导在前列腺癌发生中的作用，这两种转基因动物模型代表了治疗相关模型，用于评估这些 -VE5 衍生的 PHLPP1 靶向 Akt 抑制剂的化学预防活性。