Oleanolic acid suppresses the proliferation of lung carcinoma cells by miR-122/Cyclin G1/MEF2D axis.

Oleanolic acid (OA) is a natural compound from plants with anti-tumor activities. However, the mechanism of the inhibitory effect of OA on cell cycle progression has not been completely explored. We employed several lung carcinoma cell lines to investigate the cell cycle-related molecular pathway affected by OA. The data revealed that OA suppressed the proliferation of lung cancer cells in both dose- and time-dependent manners, along with an increase in miR-122 abundance. The suppression of miR-122 abolished the effect of OA on lung cancer cells. CCNG1 and MEF2D, two putative miR-122 targets, were found to be downregulated by OA treatment. Restoring their expression counteracted the effect of OA on lung carcinoma cells. OA was further shown to induce the expression of miR-122-regulating transcriptional factors in lung cancer cells. Collectively, OA induced cell cycle arrest in lung cancer cells through miR-122/Cyclin G1/MEF2D pathway. This finding may contribute to the understanding of the molecular mechanism of OA's anti-tumor activity.

Alcohol facilitates HCV RNA replication via up-regulation of miR-122 expression and inhibition of cyclin G1 in human hepatoma cells.

BACKGROUND: Clinical studies demonstrate synergistic liver damage by alcohol and hepatitis C virus (HCV); however, the mechanisms by which alcohol promotes HCV infection remain obscure. The liver-specific microRNA-122 (miR-122) regulates HCV replication and expression of host genes, including Cyclin G1. Here, we hypothesized that alcohol regulates miR-122 expression and thereby modulates HCV RNA replication. METHODS: The J6/JFH/Huh-7.5 model of HCV infection was used in this study. Real-time quantitative polymerase chain reaction, Western blotting, electrophoretic mobility shift assay, and confocal microscopy were used for experimental analysis. RESULTS: We found that acute alcohol exposure (25 mM) significantly increased intracellular HCV RNA as well as miR-122 levels in Huh-7.5 and Huh-7.5/CYP2E1 expressing cells in the presence and absence of J6/JFH-HCV infection. Expression of the miR-122 target, Cyclin G1, was inhibited by alcohol both in J6/JFH-infected and uninfected Huh-7.5 cells. The use of a miR-122 inhibitor increased Cyclin G1 expression and prevented the alcohol-induced increase in HCV RNA and protein levels, suggesting a mechanistic role for alcohol-induced miR122 in HCV replication. We discovered that siRNA-mediated silencing of Cyclin G1 significantly increased intracellular HCV RNA levels compared with controls, suggesting a mechanistic role for Cyclin G1 in HCV replication. Alcohol-induced increase in miR-122 was associated with increased nuclear translocation and DNA binding of the nuclear regulatory factor-κB and could be prevented by NF-κB inhibition. CONCLUSIONS: Our novel data indicate a miR-122-mediated mechanism for alcohol increasing HCV RNA replication. We show for the first time that Cyclin G1, a miR-122 target gene, has regulatory effects on HCV replication and that alcohol increases HCV replication by regulating miR-122 and Cyclin G1.

The C/EBPß-LINC01133 axis promotes cell proliferation in pancreatic ductal adenocarcinoma through upregulation of CCNG1.

Long non-coding RNAs (lncRNAs) are emerging as important regulators and prognostic markers of multiple cancers. Our aim was to determine functional involvement of lncRNAs in pancreatic ductal adenocarcinoma (PDAC). In this study, we report that LINC01133 expression is higher in PDAC tissues compared to adjacent non-cancerous tissues, and this overexpression is associated with poorer prognosis among the patients. In vitro, a knockdown of LINC01133 substantially decreased PDAC cell proliferation. Tumorigenicity of PDAC cells with the LINC01133 knockdown was significantly impaired in a xenograft model assay. Moreover, we determined that CCAAT/enhancer-binding protein ß (C/EBPß) positively regulates LINC01133 expression by binding to the response elements within the LINC01133 promoter. Higher expression of C/EBPß was observed in PDAC tissues, and this overexpression was also associated with the poorer prognosis. Furthermore, the LINC01133 knockdown decreased cyclin G1 (CCNG1) expression. Overexpression of CCNG1 attenuated the LINC01133 silencing-induced impairment of proliferation in PDAC cells. In summary, our findings revealed that the C/EBPß-LINC01133 axis performs an oncogenic function in PDAC by activating CCNG1, which may serve as a prognostic biomarker or a therapeutic target in PDAC.

MicroRNA sponge blocks the tumor-suppressing functions of microRNA-122 in human hepatoma and osteosarcoma cells.

MicroRNAs (miRNAs), as gene expression regulators, have been identified to be closely associated with tumorigenesis. Thus a loss-of-function study is more likely to reveal the biological roles of endogenous miRNAs. Genetic knockout, antisense oligonucleotide inhibitors, and miRNA sponge (miR­SP) are usually performed to inhibit the activities of miRNAs of interest. In the present study, we utilized the miR-SP method, which has long-term rather than short-term effects of antisense oligonucleotide inhibitors, to generate a microRNA-122 sponge (miR-122-SP) mediated by lentivirus, and identified its silencing role in the Huh7 hepatoma cell line and U2OS osteosarcoma cell line. The results showed that miR-122-SP effectively sequestered ectopic miR-122 and restored the expression of miR-122 which targets cyclin G1 (CCNG1), Bcl-w and disintegrin and metalloprotease 10. Moreover, miR-122-SP overexpression rescued the effects of ectopic miR-122 on suppressing proliferation, inhibiting cell migration and invasion, arresting cell cycle at G1 phase, and activating caspase-3/7, not only in Huh7 human hepatoma cells, but also in U2OS osteosarcoma cells. miR-122-SP also knocked down endogenous miR-122 expression in Huh7 and promoted tumorigenesis in vivo. miR-122-SP therefore is a useful tool that may be utilized to study the functions of miR-122 with regard to liver development and tumorigenesis in vitro and in vivo.

MicroRNA-122 sensitizes HCC cancer cells to adriamycin and vincristine through modulating expression of MDR and inducing cell cycle arrest.

Hepatocellular carcinoma (HCC) is a hypervascular cancer characterized by rapid progression as well as resistance to conventional chemotherapy. It has been shown that microRNAs play critical roles in pathogenesis of HCC. MicroRNA-122 (miR-122) is a liver-specific microRNA and is frequently downregulated in HCC. In the present study, we investigated whether restoration of miR-122 in HCC cells could render cells sensitive to chemotherapeutic agents adriamycin (ADM) or vincristine (VCR). Our data showed that overexpression of miR-122 in HCC cells induced by adenovirus expressing miR-122 could render cell sensitive to ADM or VCR. Analysis of cell cycle distribution showed that the anti-proliferative effect of miR-122 is associated with increase of cell number in the G2/M phase. Moreover, treatment with Ad-miR122 and ADM or VCR resulted in high accumulation of HCC cells in G2/M phase. We further demonstrated that overexpression of miR-122 could modulate the sensitivity of the HCC cells to chemotherapeutic drugs through downregulating MDR related genes MDR-1, GST-π, and MRP, antiapoptotic gene Bcl-w and cell cycle related gene cyclin B1. Taken together, our findings demonstrated that combination of Ad-miR122 with chemotherapeutic agents inhibited HCC cell growth by inducing G2/M arrest and that this arrest is associated, at least in part, with reduced expression of MDR related genes and Cyclin B1.