Figure 5.
Mechanism of increased NKG2D ligand expression in VPA-treated ARK cells. (A) Constitutive activation of pERK in VPA-treated ARK cells compared with that of the untreated cells is shown. The same amount of cell extracts prepared from the VPA-treated or medium-alone cell cultures was used for Western blot analyses. (B) Western blot analysis of VPA-treated ARK cells after specific inhibition of ERK activation using PD98059. Data are representative of three experiments. (C–F) MICA/B and ULBP2 expressions in VPA-treated ARK cells after a 48-hour treatment with PD98059 (PD) using flow cytometric analysis. Histograms and mean fluorescence intensity (MFI) levels of MICA/B and ULBP2 expressions on ARK cells are shown. Blue lines represent untreated cells; purple lines represent VPA-treated cells; red lines represent VPA plus PD98059-treated cells. Results are representative of three different experiments. Error bars indicate ±SD. (G) NK cell cytotoxicity of ARK cells treated with or without VPA after a 48-hour treatment with PD98059 or DMSO alone. Results are representative of three different experiments. Error bars indicate ±SD. *P < .05; **P > .05.