乳腺癌亚型特异性FOXF2表达及转录抑制功能的调节机制

We have previously demonstrated that mesenchymal transcription factor forkhead box F2 (FOXF2) is specifically expressed in basal-like breast cancer (BLBC) cells but not or less in non-BLBC cells including luminal breast cancer cells. FOXF2 pleiotropically represses the transcription of its genes coding epithelial-mesenchymal transition-inducting transcription factors (EMT-TFs) and signal molecules related with the induction of EMT, cancer stem cell (CSC) and cancer-associated fibroblast (CAF), whereas, FOXF2 have no such function in luminal breast cancer cells. FOXF2 deficiency permits the transition of BLBC cells into mesenchymal/CSC-like phenotypes to form dissemination and visceral metastasis at early stage. In addition, FOXF2-deficient BLBC cells can be converted into cancer-associated fibroblast (CAF)-like phenotype that trigger the EMT of their adjacent cells through paracrine signals, thus accelerate aggressive progression of tumors. This project aims to investigate the mechanisms underlying histone modification-linked transcriptional regulation on FOXF2 enhancer for breast cancer subtype-specific expression of FOXF2 as well as the transrepression function of FOXF2 through modulating the promoter chromatin status of its target genes in a BLBC subtype-specific manner, based on the bioinformatics analysis and validations by the assays of Co-IP and ChIP-qPCR as well as a series of in vitro experiments. Moreover, we would explore the value of histone deacetylase as therapeutic targets for the treatment of BLBC with different FOXF2 expression statues.

前期研究发现间质转录因子FOXF2特异性表达在基底样乳腺癌（BLBC）细胞，但在非BLBC细胞不表达或低表达；FOXF2在BLBC细胞中多效性转录抑制上皮-间质转化（EMT）、癌干细胞（CSC）和癌相关成纤维细胞（CAF）诱导性转录因子和信号分子相关基因表达，但在Luminal细胞中FOXF2对靶基因无转录抑制作用；FOXF2表达缺乏的BLBC细胞可通过EMT/CSC样/CAF样表型转化，早发播散性内脏转移，还可通过旁分泌信号分子诱导临近细胞EMT，进而加速肿瘤恶性进展，本项目旨在通过生物信息学分析及Co-IP和ChIP-qPCR等实验及体外细胞实验验证，揭示FOXF2在乳腺癌细胞中亚型特异性表达和转录抑制功能的组蛋白修饰介导的增强子转录调节机制以及靶基因启动子组蛋白修饰调节机制，并通过体外细胞实验和体内动物实验评价靶向组蛋白去乙酰化酶抑制剂治疗不同FOXF2表达状态BLBC的应用价值。

前期研究发现间质转录因子FOXF2特异性表达在三阴性乳腺癌（TNBC）/基底样乳腺癌（BLBC）细胞，但在非BLBC细胞不表达或低表达；FOXF2在BLBC细胞中多效性转录抑制上皮-间质转化（EMT）、癌干细胞（CSC）和癌相关成纤维细胞（CAF）诱导性转录因子和信号分子相关基因表达，但在Luminal细胞中FOXF2对靶基因无转录抑制作用；FOXF2表达缺乏的BLBC细胞可通过EMT/CSC样/CAF样表型转化，早发播散性内脏转移，还可通过旁分泌信号分子诱导临近细胞EMT，进而加速肿瘤恶性进展，本项目通过生物信息学分析及Co-IP和Re-ChIP等实验及体外细胞实验验证，揭示了FOXF2在乳腺癌细胞中亚型特异性表达和转录抑制功能的组蛋白修饰介导的增强子转录调节机制以及靶基因启动子组蛋白修饰调节机制，并通过体外细胞实验和体内动物实验证实靶向组蛋白去乙酰化酶治疗不同FOXF2表达状态BLBC的应用价值。研究发现，在ERα+/Luminal乳腺癌细胞中，ERα结合于FOXF2基因座附近，通过募集组蛋白甲基转移酶形成静息状态增强子，从而抑制FOXF2转录；在BLBC细胞中，FOXF2通过募集NCoR1/HDAC3，使靶基因启动子区组蛋白去乙酰化修饰形成抑制性染色质结构，从而抑制EMT和CSC相关靶基因转录；HDAC小分子抑制剂MS-275显著上调TNBC/BLBC细胞的FOXF2表达并抑制细胞增殖和转移，有潜在的临床应用价值，但SAHA下调TNBC/BLBC细胞的FOXF2表达而增加了内脏转移风险。研究结果丰富了对于ERα+/Luminal乳腺癌和TNBC/BLBC转移机制的理论认识，并有助于制定有效的乳腺癌治疗策略。