Silencing SIX1 by miR-7160 inhibits non-small cell lung cancer cell growth

The homeoprotein SIX1 is upregulated in non-small cell lung cancer (NSCLC) and associated with NSCLC tumorigenesis and progression. We identified microRNA-7160 (miR-7160) as a SIX1-targeting miRNA. RNA immunoprecipitation results confirmed a direct binding between miR-7160 and SIX1 mRNA in NSCLC cells. In the primary and established NSCLC cells, forced overexpression of miR-7160 downregulated SIX1 and inhibited cancer cell growth, proliferation, migration and invasion. Furthermore, miR-7160 overexpression induced apoptosis activation in NSCLC cells. Conversely, miR-7160 inhibition elevated SIX1 expression and enhanced NSCLC cell progression in vitro. Restoring SIX1 expression, by an untranslated region-depleted SIX1 expression construct, reversed miR-7160-induced anti-NSCLC cell activity. CRISPR/Cas9-inudced knockout of SIX1 mimicked miR-7160-induced actions and produced anti-NSCLC cell activity. In vivo, intratumoral injection of miR-7160-expressing lentivirus downregulated SIX1 mRNA and inhibited NSCLC xenograft growth in severe combined immunodeficient mice. Significantly, miR-7160 expression is downregulated in human NSCLC tissues and is correlated with SIX1 mRNA upregulation. Collectively, miR-7160 silenced SIX1 and inhibited NSCLC cell growth in vitro and in vivo.