肿瘤中调控脂肪酸合成限速酶SCD1表达的新机制

Enhanced fatty acid synthesis is one of the important characteristics of tumor cells. SCD1 (Stearoyl-CoA desaturase 1) is a key rate-limiting enzyme in fatty acid synthesis pathway, which is highly expressed in many tumors. However, the molecular mechanism of how SCD1 is regulated is largely unknown. Our preliminary results showed that the transcription factor SIX1 could increase the expression of SCD1 and the promoter activity of SCD1 gene, and the transcription factor HIF-1α could enhance the expression of SIX1 and SCD1. The ability of HIF-1α to increase the expression of SCD1 was lost after SIX1 knockout, suggesting that HIF-1α/SIX1/SCD1 may constitute a regulatory axis. On this basis, the regulation of HIF-1α and SIX1 on SCD1 and its molecular mechanism will be determined by using reporter gene activity analysis, ChIP, EMSA, and protein-protein interaction technology. The effects of HIF-1α and SIX1 on SCD1-mediated fatty acid metabolism and tumor growth will be examined by cell and animal models. The clinical significance of HIF-1α/SIX1/SCD1 axis will be investigated by tumor patients. This study will provide a new basis for the development of antitumor drugs by targeting fatty acid metabolic pathway.

增强的脂肪酸合成是肿瘤细胞的重要特征之一，SCD1(Stearoyl-CoA desaturase 1)是脂肪酸合成途径的一个关键限速酶，在很多肿瘤中高表达，但SCD1如何被调控的分子机制还很不清楚。我们的初步研究结果表明，转录因子SIX1能升高SCD1表达且升高SCD1基因启动子活性，而转录因子HIF-1α能升高SIX1和SCD1表达，敲除SIX1后HIF-1α升高SCD1表达的能力丧失，提示HIF-1α/SIX1/SCD1可能构成了一个调控轴。本研究拟在此基础上，利用报告基因活性分析、ChIP、EMSA、蛋白质间相互作用技术等确定HIF-1α和SIX1对SCD1的调节方式及其分子机制；利用细胞和动物模型确定HIF-1α和SIX1对SCD1介导的脂肪酸代谢和肿瘤生长的影响；利用肿瘤患者标本确定HIF-1α/SIX1/SCD1轴的临床意义，为靶向脂肪酸代谢通路开发抗肿瘤药物提供新的依据。

增强的脂肪酸合成是肿瘤细胞的重要特征之一。SCD1 (Stearoyl-CoA desaturase 1)是脂肪酸合成途径的一个关键限速酶，在很多肿瘤中高表达，但SCD1如何被调控的分子机制还很不清楚。我们的研究结果表明，转录因子SIX1能升高SCD1表达且升高SCD1基因启动子活性，而转录因子HIF-1α能升高SIX1和SCD1表达，敲除SIX1后HIF-1α升高SCD1表达的能力丧失，提示HIF-1α/SIX1/SCD1可能构成了一个正向调控轴。在此基础上，我们利用荧光素酶报告基因活性分析、染色质免疫共沉淀（ChIP）等实验确定了SIX1结合在SCD1启动子上，并促进其启动子活性，且SIX1通过与组蛋白修饰酶KAT7结合调控SCD1的转录和表达。SCD1酶活性检测、甘油三酯含量检测、油红O染色和生长曲线等实验说明了SIX1能调控SCD1的酶活性，并通过SCD1调控脂肪酸代谢及肿瘤细胞增殖和生长；缺氧诱导实验证明缺氧可诱导SIX1表达，荧光素酶报告基因活性分析、染色质免疫共沉淀（ChIP）等实验表明HIF-1α募集在SIX1启动子上，并升高SIX1启动子活性；Western blot、实时定量PCR实验显示HIF-1α调控SIX1及SCD1的表达，并通过SIX1调控SCD1的表达。SCD1酶活性检测、甘油三酯含量检测、油红O染色、生长曲线等实验表明HIF-1α通过SIX1调控SCD1酶活性，并影响脂肪酸代谢和肿瘤细胞生长。乳腺癌病人临床数据分析显示，HIF-1α、SIX1、KAT7和SCD1表达呈正相关。综上所述，HIF-1α/SIX1/SCD1调控轴在脂肪酸代谢和肿瘤生长中至关重要，为靶向脂肪酸代谢通路开发抗肿瘤药物提供了新的依据和候选靶标。