Celastrol blocks cell cycle of A549 cells by regulating miR-17-5p/miR-155-5p and targeting cyclin D1

AIM: To investigate the effect of celastrol on the cell cycle of human lung adenocarcinoma A549 cells and to probe into its mechanisms.METHODS: A549 cells were exposed to celastrol at gradient concentrations. The cell viability and apoptosis were detected by MTT assay and flow cytometry, respectively, and the median lethal concentration (LC₅₀) of celastrol was screened. The A549 cells were treated with celastrol at LC₅₀, and the cell cycle was detected by flow cytometry. The expression of cyclin D1 was determined by Western blot, and the expression of microRNA (miR)-17-5p and miR-155-5p was detected by real-time PCR. The correlation between cyclin D1 and miR-17-5p or miR-155-5p was predicted by bioinformatics software. After miR-17-5p mimics/miR-155-5p mimics/mutant-miR-17-5p/mutant-miR-155-5p and pcDNA-GFP-cyclin D1-3'UTR were cotransfected into the A549 cells, the changes of GFP expression were evaluated by fluorescence microscopy and flow cytometry. Finally, after miR-17-5p mimics or miR-155-5p mimics were transfeced into the A549 cells, the expression of miR-17-5p and miR-155-5p was detected by real-time PCR, and the protein level of cyclin D1 was determined by Western blot. RESULTS: With the increasing concentration of celastrol, the viability inhibition rate and apoptotic rate of the A549 cells were increased, indicating that celastrol effectively inhibited the growth of A549 cells and induced apoptosis. The LC₅₀ of celastrol was almost 3 μmol/L. After treatment with celastrol at LC₅₀, the A549 cell cycle was arrested at G₁ phase, the protein expression of cyclin D1 was down-regulated (P<0.01), and the expression levels of miR-17-5p and miR-155-5p were significantly increased (P<0.01). The results of bioinformatics software prediction indicated that there were binding sites for miR-17-5p and miR-155-5p in the 3'-UTR of cyclin D1. After cotransfected with miR-17-5p or miR-155-5p and pcDNA-GFP-cyclin D1-3'UTR into the A549 cells, the expression of GFP declined (P<0.05). After miR-17-5p or miR-155-5p mimics were transfected into A549 cells, the results of real-time PCR showed this treatment significantly increased the miRNA expression (P<0.01), and the results of Western blot showed the transfection inhibited cyclin D1 expression (P<0.01).CONCLUSION: Celastrol blocks the A549 cells at G₁ phase, inhibits the viability and induces apoptosis, which may be caused by up-regulating the expression of miR-17-5p and miR-155-5p, and then down-regulating cyclin D1 expression. This study provides a new theoretical basis for the treatment of non-small-cell lung cancer with celastrol.