肺癌细胞中RARγ通过"非基因组作用"调控EGFR生物学功能

Our group has discoved and published that retinoic acid receptor-γ (RARγ) among multi-nuclear receptors remains a unique subcellular localization for the first time. RARγ was cytoplasmic in confluent cells, or when cells were released from serum depletion or treated with growth factors, but the biological function is unclear. EGFR, a member of the ErbB family of receptor tyrosine kinases, is frequently overexpressed and mutated in many types of human lung cancer.Therefore, It's an important therapeutic target for the critical effects on the initiation and progression of lung cancer. Our recently data have showed that the nuclear receptor RARγ interacts with EGFR and regulates the degradation of EGFR and the downstream responses induced by EGF via a "nongenomic" actions. Based on this important finding, we suppose that RARγ may regulate both of kinase dependent and kinase independent biological function of EGFR through interaction with EGFR.We will explain the effects of RARγ on lung cancer initiation and progression and find new lead compounds targeted RARγ by taking advantages of many tools in molecular, cellular and animals models, which focused on the biological function regulation of EGFR by nuclear receptor RARγ. Therefore, this program will explaine its new inspects on the effects of RARγ in lung cancer, and may offer a new therapeutic target and strategy to kill lung cancer cells.

我们课题组首次发现并报道，在众多核受体中，RARγ细胞定位独特。生长因子、血清刺激以及高细胞密度可以使RARγ转位并定位于细胞核外，但RARγ出核后的功能尚不清楚。肺癌细胞中EGFR高表达、多突变且功能异常、多样，在肺癌的发生、发展和演进中起着非常重要的作用。因此，EGFR是肺癌治疗的重要靶点。我们的前期研究显示，在肺癌细胞中RARγ与EGFR相互作用，并以"非基因组作用"方式调控EGF诱导的EGFR降解和下游的激酶活性。基于这一重要发现，我们假设RARγ通过与EGFR相互作用调控其激酶依赖和非依赖的生物学功能。本项目以肺癌为研究对象，在分子水平、细胞水平和动物模型等多个层面、采用多种技术方法，围绕核受体RARγ对EGFR的调控，深入了解RARγ对肺癌发生、发展的影响，发现新的基于RARγ的先导化合物。本项目将从新的视角阐述核受体RARγ在肺癌中的作用，并为肺癌的治疗提供新的靶点和方法。

以RARγ的特异性拮抗剂MM11253为小分子探针，研究了RARγ调控 EGFR激酶活性依赖的生物学功能及机制，鉴定并发现了一系列靶向RARγ的天然化合物或合成化合物，为基于RARγ寻找治疗肺癌的先导化合物奠定了基础。主要工作如下：.1. 肺癌细胞H292中干扰RARγ，抑制EGF诱导具促分裂作用的Nur77的表达和细胞周期进程。.2. MM11253 RARγ依赖的抑制EGF诱导的ERK、AKT等激酶激活，Cyclin D1、c-Myc的表达以及细胞周期进程。.3. RARγ与KSR1的相互作用，EGF可以增强它们的相互作用，而MM11253可以抑制这种相互作用。这表明RARγ可以通过与KSR1相互作用，从而以一种非基因型作用方式调控EGF/EGFR所激活的ERK信号通路。.4. 以RARγ特异性激动剂AHPN母环为结构基础，以RARγ-LBD为靶点，结合计算机辅助药物设计，通过7步合成反应，得到39个AHPN衍生物，所有的化合物的结构均经过波谱分析验证。.5. 采用表面等离子共振技术（Surface Plasmon Resonance，SPR）从一系列天然和合成化合物中筛选出多个与RARγ结合的新配体，其中AHPN衍生物6个，以紫草酸和姜黄素为代表的天然产物8个。