MicroRNA-23a downregulates the expression of interferon regulatory factor-1 in hepatocellular carcinoma cells

Abstract

Interferon regulatory factor-1 (IRF-1) is a tumor-suppressor gene induced by interferon-γ (IFNγ) and plays an important role in the cell death of hepatocellular carcinoma (HCC). HCC tumors evade death in part by downregulating IRF-1 expression, yet the molecular mechanisms accounting for IRF-1 suppression in HCC have not yet been characterized. Previous studies have shown that microRNA-23a (miR-23a) can suppress apoptosis by targeting IRF-1. Therefore, we hypothesized that miR-23a promotes HCC growth by down-regulating IRF-1. For the in vivo studies, 7 cases of resected HCC and adjacent liver samples were analyzed. For the in vitro studies, IRF-1 mRNA and protein were examined in HepG2 and Huh-7 HCC cells after IFNγ stimulation by real-time PCR and western blotting, respectively. To determine the role of miR-23a in regulating IRF-1, HepG2 cells were transfected with an miR-23a mimic or inhibitor, and IRF-1 expression was examined. Binding of miR-23a was assessed by cloning the 528-bp human IRF-1 3′-untranslated region (3′UTR) into luciferase reporter plasmid pMIR-IRF-1-3′UTR. The results showed that IRF-1 mRNA expression was down-regulated in the human HCC tumor tissues compared to that in the adjacent background liver tissues. IFNγ-induced IRF-1 protein was less in the HepG2 tumor cells compared to that in the primary human hepatocytes. miR-23a expression was inversely correlated with IRF-1, and addition of the miR-23a inhibitor increased basal IRF-1 mRNA and protein. Likewise, the miR-23a mimic downregulated IFNγ-induced IRF-1 protein expression, while the miR-23a inhibitor increased IRF-1. Furthermore, the miR-23a mimic repressed IRF-1-3′UTR reporter activity, while the miR-23a inhibitor increased the reporter activity. These results demonstrated that IRF-1 expression is downregulated in human HCC tumors compared to that noted in the background liver. miR-23a downregulates the expression of IRF-1 in HCC cells, and the IRF-1 3′UTR has an miR-23a binding site that binds miR-23a and decreases reporter activity. These findings suggest that the targeting of IRF-1 by miR-23a may be the molecular basis for IRF-1 downregulation in HCC and provide new insight into the regulation of HCC by miRNAs.

Biomarker MicroRNAs for Diagnosis, Prognosis and Treatment of Hepatocellular Carcinoma: A Functional Survey and Comparison

“…Yan et al . found that miR-23a was a negative regulator of IRF-1in HCC, which highlighted its importance in HCC initiation and progression135. Zhang et al .…”

MicroRNAs and clinical implications in hepatocellular carcinoma

“…This up-regulation in liver cirrhosis than healthy controls and further up-regulation in HCC patients in comparison to viral hepatitis patients suggests a role of microRNA 23a in the pathogenesis of HCC. A study on resected human HCC tissues found that microRNA-23a down-regulates the expression of interferon regulatory factor-1 in HCC cells[ 17 ].…”

MicroRNA-23a-3p Down-Regulation in Active Pulmonary Tuberculosis Patients with High Bacterial Burden Inhibits Mononuclear Cell Function and Phagocytosis through TLR4/TNF-α/TGF-β1/IL-10 Signaling via Targeting IRF1/SP1

“…The SP1 transcriptional regulatory element is present within the TLR4, TNF-α, and TGF-β1 gene promoters, while the IRF1 transcriptional regulatory element is present within the IL10 gene promoter [20][21][22][23]. Furthermore, SP1 and IRF1 have been shown to be direct targets of miR-23a in previous studies [24][25][26]. Thus, it is reasonable to infer that miR-23a-3p could mediate the imbalance between TLR4/TNF-α pro-inflammatory and IL10/TGF-β1 anti-inflammatory pathways under Mtb stimuli via targeting SP1 and IRF1 directly.…”