表观遗传蛋白BRD4调控肿瘤相关成纤维细胞HGF分泌促结直肠癌增殖转移的功能与分子机制研究

Cancer-associated fibroblasts (CAF) promote proliferation and metastasis of cancer cells through paracrine effect. Targeting paracrine of CAF showed promising responses in cancer treatment. In our previous study, we demonstrated the role of BRD4 proteins in promoting colorectal cancer cells. BRD4 regulated oncogene transcription through binding H3K27ac. Targeting BRD4 showed colorectal cancer inhibition through c-myc downregulation. Moreover, we found that BRD4 inhibitors could also inhibit tumor promoting effect of CAF, suggesting that BRD4 could play a critical role in CAF. Epigenetic dysregulation plays great role in the function of CAF. However, little is known about tumor promoting effect and epigenetic regulation of BRD4 in CAF. Thus, we suppose that BRD4 could activate CAF through promoting transcription and secretion of HGF. Targeting BRD4 could block the pro-tumor microenvironment of colorectal cancer. In this study, we explored the epigenetic molecular mechanism of BRD4 proteins in activating HGF secretion in CAFs and evaluate whether it could serve as a molecular therapeutic target, which can provide new molecular mechanism for CAF and new drug target for the treatment of colorectal cancer.

肿瘤相关成纤维细胞(CAF)通过旁分泌作用促进肿瘤的增殖转移，抑制CAF的促肿瘤功能具有重要治疗意义。本课题申请人既往研究表观蛋白BRD4在结直肠癌的异常调控，BRD4通过与H3K27ac结合调节癌基因转录，靶向抑制BRD4可通过调控c-myc抑制结直肠癌细胞。我们进一步发现，BRD4抑制剂亦可显著抑制原代CAF促肿瘤作用，提出BRD4可通过表观调控参与CAF促肿瘤功能。CAF促肿瘤作用与表观异常调控密切相关，但CAF促肿瘤机制尚未阐明，BRD4对CAF的表观调控未见报道。我们推测：BRD4是CAF重要表观调控蛋白，通过直接调控HGF转录与旁分泌促进肿瘤细胞增殖转移，靶向BRD4可阻断适宜肿瘤生存的微环境。本课题拟在CAF中研究BRD4转录调控HGF促肿瘤的生物学功能与分子机制，评估BRD4能否作为CAF治疗靶点，为CAF促肿瘤表观调控提供新的机制，也为结直肠癌靶向治疗提供新的药物靶点。

肿瘤相关成纤维细胞(CAF)通过旁分泌作用促进肿瘤的增殖转移，抑制CAF的促肿瘤功能具有重要治疗意义。BET蛋白是一类重要的表观遗传调控蛋白，包括BRD2/3/4，通过溴化结构域与H3K27结合调节癌基因的转录表达，促进肿瘤发生发展。我们前期研究发现，BRD4抑制剂亦可显著抑制原代CAF促肿瘤作用，提出BRD4可通过表观调控参与CAF促肿瘤功能。CAF促肿瘤作用与表观异常调控密切相关，但CAF促肿瘤机制尚未阐明，BRD4对CAF的表观调控未见报道。本课题在CAF中研究BRD4转录调控HGF促肿瘤的生物学功能与分子机制，评估BRD4能否作为CAF治疗靶点，对于深入理解CAF在微环境中的促肿瘤作用、寻找新的分子靶点具有重要意义。研究内容主要分为以下四个部分：（1）原代结直肠癌CAF培养与鉴定；（2）BRD4调控CAF促肿瘤增殖转移的生物功能学研究；（3）BRD4转录调控HGF促肿瘤的分子机制研究；（4）动物实验验证CAF通过BRD4-HGF轴促进肿瘤增殖转移。本项目得出以下结论：BRD4是CAF促肿瘤作用中的重要表观调控蛋白之一，BRD4与HGF转录位点结合，直接调控HGF表达，通过旁分泌HGF与肿瘤细胞MET受体结合，通过BRD4-HGF-MET信号轴促进肿瘤细胞增殖转移。靶向抑制BRD4可通过抑制CAF细胞因子旁分泌，阻断适宜肿瘤生存的微环境，从而抑制CRC细胞增殖及远处转移。受该项目资助，目前发表SCI论文1篇（共同通讯，影响影子6.63，JCR分区1区），获得1项国家发明专利。