Project 2: Design and Development of Third Generation RXR Rexinoids as Potential Chemoprevention Agents

免疫抑制的器官移植患者患非黑色素瘤的风险很高 皮肤癌（NMSC）。在这种高危人群中预防NMSC需要开发 因为这些药物是长期给药的，所以这些药物具有最小的毒性。食品药品管理局- 批准的药物尚未确定用于预防NMSC。我们已经开发出一种新颖 组织选择性rexinoid，命名为UAB 30，在上皮组织中作为激动剂，但在 肝脏UAB 30在多种癌症预防模型中高度有效，同时表现出最小的 毒性（尤其是脂质毒性）。UAB 30目前正在1期人体试验中进行评估。 初步结果（核心3）表明，UAB 30在防止形成 乳头状瘤、基底细胞癌和鳞状细胞癌。 我们还表明，UAB 30上调了对增强全反式维甲酸的重要基因。 在正常上皮和癌症中的酸生物合成。因此，我们在本提案中假设， UAB 30（或其他UAB 30样激动剂）通过增强RXR-RAR信号传导来预防NMSC 异二聚体。在目标1中，我们提出研究来了解rexinoids如何结合RXR并重塑 核受体的表面来募集辅激活因子。残留物的重要性 两个假定的分子网络，将rexinoid结合位点与辅激活物结合位点连接起来 将使用X射线晶体学、氢-氘交换质量 光谱法（HDX MS）和等温滴定量热法（ITC）。在目标2中，我们提出研究 了解是否揭示了效力与毒性的分子特征， 新的第三代激动剂被设计为无毒性。一系列的结构研究 UAB 30的甲基衍生物已经揭示了配体结合口袋中的推定“热点”， 刺激脂质生物合成和毒性。我们将通过以下方式研究这一“热点”的重要性： 评价一系列具有已知脂质分布的有效类Rexinoids的结构和动力学（有效的 诱导脂质合成的类Rexinoids与不诱导脂质合成的类Rexinoids）。一组结构生物学家 在X射线晶体学、质谱、热力学和生物物理学方面的专业知识， 为实现这些目标而聚集。项目2提供了关于结构和动力学的信息 我们假设的RXR的水平，对于确定哪些rexinoids是有效的， 无毒的项目2将与核心2在设计新的第三代rexinoids， 在项目3的体外研究和核心3的体内模型中进行评价。程序 整合部分包含第三代rexinoids的完整开发方案。

Organ transplant patients who are immune-suppressed are at high risk to develop non-melanoma skin cancers (NMSC). Prevention of NMSC in this high risk population requires the development of effective drugs with minimal toxicity since these drugs are administered chronically. An FDA- approved drug has yet to be identified for use to prevent NMSC. We have developed a novel tissue-selective rexinoid, named UAB30, which acts as an agonist in epithelial tissues but not in liver. UAB30 is highly effective in multiple cancer prevention models while exhibiting minimal toxicity (especially lipid toxicity). UAB30 is currently evaluated in phase 1 human trials. Preliminary results (Core 3) show that UAB30 is highly effective in preventing the formation of papilloma, basal cell carcinoma, and squamous cell carcinoma in UVB-irradiated hairless mice. We have also shown that UAB30 up-regulates genes important for enhancing all-trans-retinoic acid biosynthesis in normal epithelium and in cancers. Thus, we hypothesize in this proposal that UAB30 (or other UAB30-like agonists) prevent NMSC by enhancing signaling through RXR-RAR heterodimers. In Aim 1, we propose studies to understand how rexinoids bind RXR and remodel the surface of the nuclear receptor to recruit coactivators. The importance of residues within the two putative molecular networks that bridge the rexinoid binding site to the coactivator binding site will be investigated using x-ray crystallography, Hydrogen-Deuterium Exchange Mass Spectrometry (HDX MS), and isothermal titration calorimetry (ITC). In Aim 2, we propose studies to understand if the molecular signatures of potency versus those of toxicity be revealed so that new 3rd -generation agonists are designed without toxicity. Structural studies on a series of methyl-derivatives of UAB30 have revealed a putative `hot-spot' in the ligand binding pocket that stimulates lipid biosynthesis and toxicity. We will examine the importance of this `hot-spot' by evaluating structures and dynamics of a series of potent rexinoids with known lipid profiles (potent rexinoids that induce lipid synthesis versus those that do not). A team of structural biologists with expertise in x-ray crystallography, mass spectrometry, thermodynamics, and biophysics has been assembled to address these aims. Project 2 provides information on the structure and dynamics of RXR, which we hypothesized, can be important for determining which rexinoids are potent and nontoxic. Project 2 will interact with Core 2 in designing new 3rd generation rexinoids, which will be evaluated in in vitro studies in Project 3 and in in vivo models in Core 3. The Program Integration section contains a complete developmental schema for 3rd generation rexinoids.