Silencing Nanog expression inhibits MDA-MB-231 breast stem cancer cell growth in vitro and in vivo

Background: Nanog is a transcription factor with key roles in maintaining self-renewal and pluripotency in human embryonic stem (ES) cells, and it is overexpressed in numerous malignancies. The aim of the present study was to silence Nanog gene expression by RNA interference (RNAi) and observe MDA-MB-231 breast CSC tumorigenicity and chemotherapy resistance. Materials and methods: We constructed a recombinant plasmid of pLvx-siNanog-ZsGreen-Puro and direct injected it into the tumors formed by MDA-MB-231 stem cells implanted in nude mice. A paclitaxel inhibition test was performed to measure resistance of MDA-MB-231 breast cancer stem cells (CSCs). Western blot and quantitative polymerase chain reaction (qPCR) analysis were used to evaluate Nanog expression. Results: MDA-MB-231 stem cells transfected with short interfering RNA (siRNA) constructs showed reduced resistance to paclitaxel. Similarly, western blot and qPCR analyses revealed significantly reduced Nanog levels following siRNA transfection of MDA-MB-231 stem cells. After injecting MDA-MB-231 stem cells into mice, cells transfected with Nanog siRNA formed tumors with significantly smaller volumes and weights than the negative siRNA and control groups. Finally, western blot and qPCR analyses of xenograft tumors revealed lower relative quantities of Nanog, Oct4, c-Myc, Klf4, and SOX-2 in the Nanog siRNA group. Conclusions: The present findings suggest that Nanog gene silencing with siRNA can reduce MDA-MB-231 breast CSC tumorigenicity and chemotherapy resistance.