Abstract:

Objective To investigate the effect of nuclear receptor subfamily 2 group F member 2 （NR2F2） on the biological behaviors of human ovarian cancer SKOV3 cells， and to clarify its molecular mechauism and provide the new idea for treatment of ovarian cancer. Methods Gene Expression Profiling Interactive Analysis（GEPIA） Database analyse the expression level of NR2F2 gene in ovarian tissue， and analyse its correlation with clinical prognosis of ovarian cancer patients. The human ovarian cancer SKOV3 cells were divided into control group and NR2F2 over-expression （NR2F2 OE） group， which were transfected with mCherry control virus and NR2F2 OE over-expression virus， respectively， when the cell deusity reached 70%， and the stable transfection SKOV3 cell lines were screened with puromycin（puro） 48 h lafter. Real-time fluorescence quantitative PCR （RT-qPCR） and Western blotting methods were used to detect the transfection efficiencies of the cells； RT-qPCR method was used to detect the expression levels of NR2F2 and sex-determining region Y-box 2 （SOX2） mRNA in the cells in two groups； Western blotting method was used to detect the expression levels of NR2F2， ATP-binding cassette superfamily G member 2 （ABCG2）， and programmed cell death 1-ligand 1 （PD-L1） protcins in the cells in two groups. CCK-8 assay was used to detect the proliferation activities of the cells in two groups； Wound assay was used to detect the migration rates of the cells in two groups； Transwell chamber assay was used to detect the number of transmembrane cells； Spheroidization assay was used to detect the numbers of spheroids in the cells； peripheral blood mononuclear cells （PBMCs）-mediated tumor cell killing assay was used to detect the relative densities of surviving tumor cells； CCK-8 assay was used to detect the half maximal inhibitory concentration （IC₅₀） of paclitaxel （PTX） and carboplatin （CBP）. Results Compared with normal ovarian tissue， the expression level of NR2F2 gene in ovarian tumor tissue was decreased （P<0.05）， and decreased with the improvement of clinical pathological grading of ovarian tumor. The patients with higher expression level of NR2F2 gene had better clincal prognosis. The SKOV3 cells with NR2F2 over-expresson were successfully constructed， and the expression levels of NR2F2 mRNA and protein in the cells in NR2F2 OE group were increased compared with control group （P<0.001）. The CCK-8 assay results showed that compared with control group， the proliferation activities of the cells in NR2F2 OE group were decreased at different time points （1， 2， 3， and 4 d） （P<0.05 or P<0.01）. The cell wound assay results showed that compared with control group， the migration rate of the cells in NR2F2 OE group was decreased （P<0.001）. The Transwell assay results showed that compared with control group， the number of transmembrane cells in NR2F2 OE group was decreased （P<0.01）. Compared with control group， the number of the spheroids in NR2F2 OE group was decreased （P<0.05）， and the expression levels of SOX2 mRNA（P<0.01） and protein （P<0.001） were increased. Compared with control group， the relative density of surviving tumor cells in NR2F2 OE group was decreased， but the difference was not significant （P<0.05）， and the expression level of PD-L1 protein was decreased （P<0.05）. Compared with control group， the proliferation activities of cells in NR2F2 OE group were decreased （P<0.05）， and the drug sensitivities of the cells to PTX and CBP were enhanced （P<0.05）； the IC₅₀ of PTX was significantly reduced， while the IC₅₀ of CBP could not be calculated due to excessively high drug concentration； the expression level of ABCG2 protein was decreased （P<0.05）. Conclusion The over-expression of NR2F2 may inhibit the proliferation， migration， and invasion of the human ovarian cancer SKOV3 cells， decrease the expression levels of SOX2， PD-L1 and ABCG2 proteins， suppress the stemness and immune evasion ability of the SKOV3 cells， and enhance the sensitivities of the SKOV3 cells to PTX and CBP.

Key words: Nuclear receptor subfamily 2 group F member 2, Ovarian neoplasm, Tumor stemness, Immune escape, Drug resistance