Effect of corilagin on IκB-α and nuclear factor-κB P65 in U251 glioma cells and glioma stem cells

Objective To explore the effect of corilagin on proliferation of glioma U251 cells and glioma stem cells and IκB-α and nuclear factor (NF)-κB P65 protein expressions in these cells. Methods The glioma stem cells were isolated from glioma U251 cells by using immune magnetic beads. The cells were intervened by different corilagin concentrations (0, 25, 50 and 100 μg/mL) for 48h, respectively. Cell morphology changes were observed by microscope; cell counting kit (CCK)-8 assay was used to detect the cell proliferation; dual-luciferase reporter assay was employed to detect the P65 gene promoter expression; Western blotting was used to investigate the protein expressions of IκB-α in cytoplasm and NF-κB P65 in nucleus. Results (1) Cell morphology observation results showed that the cells became shrunken, cell density was decreased, and cell structure was destroyed with a great deal of cell debris. (2) CCK-8 assay results showed that as compared with those in the 0 μg/mL corilagin group, the survival rates of U251 glioma cells and glioma stem cells were significantly decreased in the 25, 50 and 100 μg/mL corilagin groups (P<0.05); while in the presence of the same corilagin concentration, the survival rate of U251 glioma cells was significantly higher than that of glioma stem cells (P<0.05). (3) Dual-luciferase reporter assay results showed that as compared with the 0 μg/mL group, the P65 gene promoter expressions of U251 glioma cells and glioma stem cells in the 25 μg/mL corilagin group were significantly increased (P<0.05), but with increasing concentrations of corilagin, the expressions were gradually decreased. (4) Western blotting results showed that the IκB-α expressions in cytoplasm of U251 cells and U251 stem cells were significantly increased, but the NF-κB P65 expression in nucleus of U251 cells and U251 stem cells was significantly decreased with increasing concentrations of corilagin (0, 25, 50 and 100 μg/mL), with signficant differences between each two groups (P<0.05). Conclusion Corilagin could inhibit the expression of P65 gene promoter, promote the IκB-α protein expression in cytoplasm, reduce NF-κB P65 protein into the nucleus, thereby to inhibit the NF-κB signaling pathway, and it is likely to be one of the important mechanisms to inhibit the proliferation of glioma cells and glioma stem cells. Key words: Glioma; Glioma stem cell; Corilagin; Nuclear factor-κB P65; IκB-α