NF-κB signaling relieves negative regulation by miR-194 in hepatocellular carcinoma by suppressing the transcription factor HNF-1α

Constitutive activation of the proinflammatory transcription factor nuclear factor kappa B (NF-kappa B) plays an important role in progression of hepatocellular carcinoma (HCC). Emerging modulators of NF-kB signaling are noncoding RNAs, especially microRNAs (miRNAs). We previously identified miRNAs that reduced the induction of NF-kappa B activity upon addition of tumor necrosis factor-alpha (TNF alpha) to HCC cells. We found that among these miRNAs, the abundance of liver-enriched miR-194 was decreased in HCC tissue and that low abundance of miR-194 correlated with a high occurrence of vascular invasion. Overexpressing miR-194 suppressed HCC cell migration and invasiveness in culture and metastatic seeding in mice. Transcripts encoding tripartite motif containing 23 (TRIM23), a ubiquitin ligase involved in NF-kappa B activation, and chromosome 21 open reading frame 91 (C21ORF91), a protein of unknown function, were identified as direct targets of miR-194 in HCC cells; knocking down either protein decreased the activity of a luciferase NF-kappa B reporter. Furthermore, the NF-kappa B pathway activator TNF alpha, an inflammatory cytokine, inhibited the transcription of miR-194 by decreasing the abundance of hepatocyte nuclear factor-1 alpha (HNF-1 alpha). The abundance of miR-194 positively correlated with that of HNF-1 alpha and inversely correlated with that of TNF alpha in human HCC tissue. Thus, we identified a pathway in which TNF alpha-NF-kappa B signaling switches off negative regulation by suppressing HNF-1 alpha-mediated expression of miR-194, revealing insight into the mechanisms linking inflammatory pathways, miRNA, and HCC metastasis.