Objective  To investigate the effect of interleukin-37 (IL-37) inflammatory inhibitor on the proliferation, apoptosis and cycle of HepG2 hepatoma cells.

Methods  The lentiviral expression vector pCDH-CMV-MCS-IL37-copGFP-T2A-Puro with the IL-37 (pCDH-IL-37 group) and blank vector pCDH-CMV-MCS-EF1-copGFP-T2A-Puro (pCDH group) were divided into the experimental group and the control group, respectively. The two groups were screened for viral packaging and puromycin, respectively, and then transfected into HepG2 cells in vitro. The mRNA expression level of IL-37 in transfected HepG2 cells was determined by quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR). The effect of IL-37 on the proliferation of HepG2 cells was detected by cell counting kit-8 (CCK-8). The effects of IL-37 on the cycle and apoptosis of HepG2 cells were evaluated by flow cytometry.

Results  After lentivirus packaging, infection, and puromycin screening, fluorescence microscopy showed that the lentiviral expression vectors were successfully transfected into HepG2 cells. RT-qPCR showed a high level of IL-37 expression in HepG2 cells. The results of CCK-8 assay showed that after 24 h, 48 h and 72 h of cell culture, the optical density (OD) at 450 nm of cells in PCDH-IL-37 group was significantly lower than that in pCDH group. The difference was statistically significant (P<0.001), and the cell survival rate decreased gradually with the extension of culture time. Flow cytometry showed that compared with pCDH group, the ratio of S phase cells was significantly decreased in PCDH-IL-37 group, and the ratio of G1 phase cells was significantly increased, and the cell cycle was blocked in G1 phase. Flow cytometry showed that the apoptosis rate of PCDH-IL-37 group was significantly higher than that of pCDH group (9.833%±0.252% vs. 4.867%±0.569%, P<0.001). RT-qPCR results showed that mRNA expression levels of Caspase-3 and Fas were decreased in pCDH-IL-37 group, suggesting that IL-37 may have a resistance to Caspase-3 and Fas induced apoptosis.

Conclusion  IL-37 can directly inhibit the proliferation of HepG2 hepatoma cells in vitro, promote the apoptosis, and block the cell cycle in the G1 phase, and may play a role in the resistance to Caspase-3 and Fas induced apoptosis by down-regulating the expression of Caspase-3 and Fas.

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