BRD4通过增加染色质可接近性激活RUNX2/MMP-13信号通路促进胃癌恶性进展的作用和机制研究

Chromatin accessibility is critical for tumor development, however its mechanisms remain unclear. As a crucial regulator for chromatin remodeling, BRD4 promotes tumor development by regulating multiple genes, but the role of BRD4 in gastric cancer (GC) initiation and progression still remains unknown. Our previous work found that BRD4 expression was high in GC tissues, and was associated with the poor prognosis of GC patients. And BRD4 inhibitor, JQ1, could inhibit the proliferation and migration, and induce the apoptosis of GC cells, indicating BRD4 as an important gene for GC development. Besides, ATAC-seq data showed that BRD4 enhanced the chromatin accessibility of the promoter region of RUNX2, and upregulated the expression of RUNX2 and MMP-13, demonstrating that BRD4 could promote the expression of various genes related to tumor biology by changing chromatin accessibility. In this current project, we aim to investigate the biological function of BRD4, and how BRD4 activates RUNX2/MMP-13 pathway by regulating chromatin accessibility in patient-derived organoids through knockdown and overexpression methods. Finally we will evaluate the in vivo anti-tumor effect of BRD4 inhibitors in orthotopic xenografts transplanted with GC organoids. Our project will initiate the novel investigation into the association between chromatin accessibility and GC progression, and provide scientific evidence of targeting BRD4 for the treatment of GC.

细胞中染色质可接近性异常与肿瘤发展密切相关，但机制不明。BRD4作为重要的染色质重塑相关分子，可影响多基因表达，促进肿瘤恶性进展，但其在胃癌发生和恶化中的作用不清。我们前期研究发现，BRD4在胃癌组织中高表达且与患者的不良预后显著相关，BRD4抑制剂JQ1可抑制胃癌细胞增殖、迁移并诱导凋亡，表明BRD4是胃癌进展的关键基因；ATAC-seq发现BRD4可增加RUNX2启动子区域的染色质可接近性，上调RUNX2、MMP-13表达，提示BRD4可通过改变染色质可接近性促进肿瘤生物学相关基因表达。本项目拟在患者来源的胃癌类器官模型中沉默和过表达BRD4，进一步探讨BRD4功能，明确其通过调控染色质可接近性激活RUNX2/MMP-13通路的分子机制；并在移植瘤模型中评估BRD4抑制的体内抗胃癌作用。本项目将在染色质可接近性异常与胃癌发展的机制研究上开展新探索，为靶向抑制BRD4抗胃癌提供科学依据。

细胞中染色质可接近性异常与肿瘤发展密切相关，但机制尚不清楚。BRD4 作为重要的染色质重塑相关分子，通过调控大量基因的表达促进肿瘤发展。JQ1作为BRD4的小分子抑制剂，已被证明对各种人类癌症具有抑制作用，包括血液恶性肿瘤和实体恶性肿瘤。然而，JQ1是否在胃癌中也具有潜在的抗肿瘤作用仍然是未知的。在这项研究中，我们发现胃癌组织中BRD4呈高表达且与患者的不良预后有相关性。JQ1在体外可显著抑制胃癌细胞的增殖并诱导其凋亡。此外，JQ1通过诱导MET过程抑制胃癌细胞的迁移和侵袭。值得注意的是，ATAC-seq数据显示JQ1处理可下调胃癌细胞中的染色质可及性，而在可及性差异峰区域中最为富集的motif是转录因子RUNX2的结合序列。RNA-seq数据表明NID1是JQ1处理后最为下调的基因之一。随后我们证实了JQ1能显著抑制RUNX2的转录活性。同时JQ1也能显著下调NID1的蛋白和mRNA表达，而RUNX2过表达可拯救JQ1诱导的NID1表达下调。通过小干扰RNA(SiRNA)敲减NID1可诱导MET过程抑制胃癌细胞的转移。而RUNX2或NID1的过表达可以逆转JQ1对胃癌细胞转移能力的抑制。小鼠成瘤模型提示JQ1在体内通过RUNX2/NID1信号通路抑制胃癌细胞的增殖及转移。综上我们得出结论：BET蛋白抑制剂JQ1可通过下调染色质可及性使RUNX2/NID1信号通路失活从而抑制胃癌细胞的恶性生物学进展。因此，对于晚期胃癌患者来说，BRD4可能成为有希望的治疗靶点。