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 κB (NF-κB) plays an important role in progression of hepatocellular carcinoma (HCC). Emerging modulators of NF-κB signaling are noncoding RNAs, especially microRNAs (miRNAs). We previously identified miRNAs that reduced the induction of NF-κB activity upon addition of tumor necrosis factor-α (TNFα) 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-κB 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-κB reporter. Furthermore, the NF-κB pathway activator TNFα, an inflammatory cytokine, inhibited the transcription of miR-194 by decreasing the abundance of hepatocyte nuclear factor-1α (HNF-1α). The abundance of miR-194 positively correlated with that of HNF-1α and inversely correlated with that of TNFα in human HCC tissue. Thus, we identified a pathway in which TNFα-NF-κB signaling switches off negative regulation by suppressing HNF-1α-mediated expression of miR-194, revealing insight into the mechanisms linking inflammatory pathways, miRNA, and HCC metastasis.