MicroRNA-Mediated Mitochondrial Dysfunction Is Involved in the Anti-triple-Negative Breast Cancer Cell Activity of...

Emerging evidence suggests that modulating redox homeostasis through targeting mitochondrial functions may be a useful strategy for suppressing triple-negative breast cancer (TNBC) activities. However, whether there are specific microRNAs (miRNAs) involved in regulating oxidative stress-associated mitochondrial functions that can act as therapeutic targets to suppress TNBC activities remains unclear. Here, we aimed to identify the role of redox-associated miRNAs in TNBC and investigated their potential as therapeutic targets. We identified oxidative stress-responsive differentially expressed miRNAs (DEMs) regulated by phytosesquiterpene lactone deoxyelephantopin (DET) and its novel derivative DETD-35, which are known to inhibit TNBC growth and metastasis in vitro and in vivo, using comparative miRNA microarray analysis and reactive oxygen species (ROS) scavenging approaches. Mitochondrial dysfunction was identified as a major biological function regulated by a few specific DEMs. In particular, miR-4284 was identified to play a role in DET- and DETD-35-mediated ROS production, mitochondrial basal proton leak, and antiproliferation activity in TNBC cells. Moreover, DET- and DETD-35-induced mitochondrial DNA damage was observed in TNBC cells and xenograft tumors. miR-4284 was also identified to play a role in oxidative DNA damage in TNBC tumors. We identified a novel role for miR-4284 in regulating mitochondrial basal proton leak in TNBC cells, and highlighted its significance in TNBC tumor oxidative DNA damage, and its direct correlation with TNBC patient survival. We used DET and DETD-35 as proof of concept to demonstrate that activities of anticancer agents can involve regulation of multiple miRNAs playing different roles in cancer progression. Antioxid. Redox Signal. 38, 198-214.