Figure 4.

Curcumin induces ERK/MAPK activation, blockade of ERK1/2 abrogates the effect of curcumin on FOXO3a and p53 expression, while restoring the cell growth in the presence of curcumin in NPC cells. (A and B) Human CNE2 and HNE2 cells were treated with curcumin at the concentration of 40 μM for up to 24 h. The expression of the phosphorylated or total protein of ERK1/2, p38 MAPK were measured by western blot analysis using corresponding antibodies. GAPDH was used as loading control. (C) Human CNE2 cells were treated with PD98059 for 2 h, followed by exposure to curcumin (40 μM) for an additional 24 h. The expression of p53 and FOXO3a proteins were detected by western blot analysis using specific antibodies. The bar graphs represent the densitometry results of p53 and FOXO3a/GAPDH as mean ± SD of at least three separate experiments. (D) Human CNE2 cells were treated with PD98059 for 2 h, followed by exposure to curcumin (40 μM) for an additional 24 h. Cell proliferation was determined by MTT assays. The data are presented as mean ± SD of three separate experiments. ^*P<0.01 indicates significant difference from untreated control cells. ^**P<0.01 indicates significance of combination treatment as compared with curcumin alone.