Breast cancer is an important and common tumour among women worldwide. We previously showed that 27-hydroxycholesterol (27HC) promoted the invasion and migration of breast cancer cells and activated signal transducer and activator of transcription 3 (STAT-3) signalling through reactive oxygen species (ROS). However, the regulation of STAT-3 signalling by ROS needs to be further explored. Here, we showed that 27HC caused the accumulation of cellular ROS, which upregulated matrix metalloproteinase 9 (MMP9) and increased the invasive ability of MCF7 and T47D cells. 27HC decreased the protein and mRNA levels of reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) in a time- and dose-dependent manner in MCF7 and T47D cells. RECK downregulation was mediated by 27HC-induced DNA methylation via ROS in MCF7 cells. RECK knockdown increased the activity and mRNA levels of MMP9, and promoted the invasion of MCF7 cells. We also found RECK knockdown upregulated the level of p-STAT-3 in MCF7 cells. Furthermore, overexpression of RECK attenuated 27HC-induced invasion in MCF7 cells. RECK overexpression also inhibited p-STAT-3 upregulation induced by 27HC. Collectively, the results showed that DNA methylation induced by 27HC via ROS downregulated RECK, thereby activating the STAT-3 signalling pathway. RECK could serve as a novel target mediating the effect of 27HC on breast cancer.

乳腺癌是全世界女性中重要且常见的肿瘤。我们以前显示27-羟基胆固醇（27HC）促进乳腺癌细胞的侵袭和迁移，并通过活性氧（ROS）激活信号转导子和转录3激活子（STAT-3）信号。然而，ROS对STAT-3信号的调控尚需进一步探索。在这里，我们表明27HC引起细胞ROS积累，从而上调基质金属蛋白酶9（MMP9）并增加MCF7和T47D细胞的侵袭能力。27HC在MCF7和T47D细胞中以时间和剂量依赖的方式降低了具有Kazal基序（RECK）的富含诱导半胱氨酸的回复诱导半胱氨酸蛋白的蛋白质和mRNA水平。RECK下调通过27HC诱导的DNA甲基化介导的经由MCF7细胞中的ROS。RECK基因敲低增加了MMP9的活性和mRNA水平，并促进了MCF7细胞的侵袭。我们还发现RECK敲低可上调MCF7细胞中p-STAT-3的水平。此外，RECK的过表达减弱了27HC诱导的MCF7细胞侵袭。RECK的过表达也抑制了27HC诱导的p-STAT-3上调。总体而言，结果表明27HC通过ROS诱导的DNA甲基化下调RECK，从而激活STAT-3信号通路。RECK可以作为介导27HC对乳腺癌影响的新靶标。