Effect of hypoxia on HIF-1α binding genes in SUM159 breast cancer cells with ChIP-Seq.

Brain metastasis is a major cause of breast cancer mortality, but the molecular basis and pathological mechanisms are poorly understood. Here, we determined that integrin β3 (ITGB3) expression mediated by hypoxia-inducible factor 1 (HIF-1) plays a critical role in brain metastasis of breast cancer. Hypoxia induces HIF-1-dependent expression of ITGb3, which is required for breast cancer cell migration and invasion. Knockdown of HIF-1a or ITGB3 expression impairs the colonization of breast cancer cells to brain after injection into the cardiac left ventricle. Mechanistically, ITGB3 protein expressed by breast cancer cells was incorporated into extracellular vesicles (EVs). The ITGb3+ EVs associated with brain endothelial cells, activated vascular endothelial growth factor receptor 2 signaling, and increased endothelial permeability to facilitate metastatic colonization of the brain. ChIP-seq for HIF-1α in SUM159 cells. Comparative HIF-1α binding gene profiling analysis of ChIP-seq data for SUM159 cells that were exposed in 20% or 1% oxygen condition for 16 hours.

脑转移是乳腺癌致死的主要诱因之一，但其分子基础与病理机制尚未得到充分阐释。本研究证实，由缺氧诱导因子1（hypoxia-inducible factor 1, HIF-1）介导的整合素β3（integrin β3, ITGB3）表达，在乳腺癌脑转移过程中发挥关键作用。缺氧可通过HIF-1依赖性途径诱导ITGB3表达，而该表达是乳腺癌细胞迁移与侵袭所必需的。敲低HIF-1α或ITGB3的表达，会削弱乳腺癌细胞经左心室注射后向脑部定植的能力。机制研究显示，乳腺癌细胞表达的ITGB3蛋白会被整合进入细胞外囊泡（extracellular vesicles, EVs）。携带ITGB3的细胞外囊泡可与脑内皮细胞结合，激活血管内皮生长因子受体2信号通路，并提高内皮细胞通透性，从而促进肿瘤细胞向脑部定植转移。本研究对SUM159细胞开展了HIF-1α的染色质免疫沉淀测序（ChIP-seq）；同时，对分别在20%氧浓度与1%氧浓度条件下培养16小时的SUM159细胞的ChIP-seq数据，开展了HIF-1α结合基因的对比分析。