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)。预防这一高危人群NMSC需要大力发展 由于这些药物是长期给药的，所以这些药物的毒性最小。一个FDA- 批准的药物尚未确定用于预防NMSC。我们开发了一部小说 组织选择性rexinid，命名为UAB30，在上皮组织中作为激动剂，而在 肝脏。UAB30在多种癌症预防模式中高度有效，同时表现出最低限度的 毒性(尤其是脂质毒性)。UAB30目前正在进行第一阶段的人体试验。 初步结果(核心3)表明，UAB30在预防 UVB辐射无毛小鼠的乳头状瘤、基底细胞癌和鳞状细胞癌。 我们还表明，UAB30上调了对增强全反式维甲酸至关重要的基因 酸在正常上皮和癌症中的生物合成。因此，我们在这项提案中假设 UAB30(或其他类似UAB30的激动剂)通过RXR-RAR增强信号传递来预防NMSC 杂二聚体。在目标1中，我们建议进行研究，以了解rexinoid如何结合RXR和重塑 在核受体表面招募共激活剂。残留物在生命周期中的重要性 两个可能的分子网络，将rexin结合部位与辅活化子结合连接起来 将使用X射线结晶学、氢-氚交换质量来研究位置 光谱分析(HDX MS)和等温滴定量热法(ITC)。在目标2中，我们建议进行研究 为了了解效力与毒性的分子特征是否被揭示出来 新的第三代激动剂设计没有毒性。一系列化合物的结构研究 UAB30的甲基衍生物在配体结合口袋中发现了一个假定的“热点”， 刺激脂肪的生物合成和毒性。我们将通过以下方式来考察这一“热点”的重要性 评价一系列具有已知脂谱的强效Rexinoid的结构和动力学(强效 诱导类脂合成的rexinoid与不诱导类脂合成的rexinoid相比)。一个结构生物学家团队，拥有 在x射线结晶学、质谱学、热力学和生物物理学方面的专业知识 为了实现这些目标而聚集在一起。项目2提供了有关结构和动力学的信息 我们假设的RXR对于确定哪些rexinoid有效和 无毒。项目2将与核心2在设计新的第三代Rexinoid方面进行互动，这将 在项目3的体外研究和核心3的体内模型中进行评估。该计划 整合部分包含了第三代Rexinoid的完整发展模式。

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.