LXR活化介导的CHOP依赖性凋亡在AIPC生长抑制中的作用及其信号转导机制研究

Androgen-independent prostate cancer (AIPC) is characterized by shorter median survival period and lack of effective therapeutic targets, which is still puzzling the urologists. In our earlier research, it was found that liver X receptor (LXR) agonist (GW3965) could significantly inhibit cell growth of AIPC cell lines (DU-145and PC-3). The latest experimental results suggested activation of LXR can upregulate the expression of the C/EBP-homologous protein (CHOP) and downstream genes related to cell apoptosis, such as death receptor 5(DR5). Nevertheless, CHOP gene knock-out could abolish the inhibitory effects induced by LXR activator on growth of AIPC cells in great degree. In addition, the outcomes of bioinformatics analysis suggested that there were three transcription factor binding sites by LXR in the promotor region of CHOP gene. Based on the above clues and other literature, we hold the viewpoint that CHOP-dependent apoptosis play a pivotal role in growth inhibition of AIPC cells induced by LXR activation, on the other hand, LXR activation may directly regulate the gene expression of CHOP. In the research project, we will firstly clarify the effects of LXR activation on proliferation and apoptosis of AIPC cells, and on the expression of CHOP and a series of genes related cell apoptosis, through construction plasmids of LXR gene overexpression and knock-out. Secondly, we will determine the roles of CHOP-dependent apoptosis in apoptosis and growth inhibition of AIPC cells induced by LXR activation, through RNA interference and overexpression techniques of CHOP gene. Lastly, we will investigate the molecular mechanisms involved in the direct regulation of LXR activation on CHOP expression in AIPC cells with the assays of luciferase reporter (pGL2-APRE-luc) and chromatin immunoprecipitation. The research results may shed light on the pharmacological role of LXR signaling as a potential therapeutic target of AIPC.

雄激素非依赖性前列腺癌(AIPC)目前缺乏有效治疗手段。我们前期研究发现肝X受体(LXR)活化显著抑制AIPC细胞生长，进一步实验提示LXR活化明显上调AIPC细胞CHOP及其下游促凋亡基因表达，敲除CHOP基因有效拮抗LXR活化介导的细胞生长抑制。生物信息学分析显示CHOP启动子中存在LXR结合位点。综上线索及相关报道，我们认为：CHOP表达增强介导的凋亡事件在LXR活化抑制AIPC细胞生长过程中发挥关键作用，CHOP基因表达可能受LXR直接调控。本项目拟通过构建LXR各亚型过表达及干扰载体，明确其在AIPC细胞生长抑制中的作用及对增殖凋亡相关基因表达的影响；通过敲除及过表达CHOP基因，明确其在LXR活化介导的AIPC细胞凋亡及生长抑制中的作用；最后采用荧光酶报告系统等方法，探讨LXR活化直接调控CHOP基因表达的信号转导机制。该研究结果有望为LXR成为治疗AIPC新靶点提供实验证据。