We previously reported that inflammatory stimulation reduced the tumor suppressor gene Programmed cell death 4 (Pdcd4) protein expression level and enhanced the metastatic abilityof human colon cancer cells. In this study, we investigated the effect of 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulation on the expression levels of Pdcd4 protein and migratory ability in mouse Colon-26 cancer cells and B16-BL6 melanoma cells.
The expression level of Pdcd4 protein in Colon-26 cells treated with TPA significantly decreased in a concentration-dependent manner. On the other hand, Pdcd4 protein in B16-BL6 cells treated with TPA significantly increased in a concentration-dependent manner. In addition, the migratory ability of Colon-26 cells treated with TPA were significantly increased, but the migration of B16-BL6 cells treated with TPA were significantly decreased. Furthermore, we measured the melanin content of the cells and tyrosinase activity as indices of activation of Protein Kinase C (PKC). The melanin content and tyrosinase activity were significantly decreased in B16-BL6 cells treated with TPA.
These results indicated that Pdcd4 might be a negative regulator in the migratory ability of Colon-26 and B16-BL6 cells. Although the activation of PKC promoted degradation of Pdcd4 in Colon-26 cells, it did not function in B16-BL6 cells.