FIGURE 6.

Erk1/2 inhibitor U0126 directly decreased cytotoxicity of NK92 cells without influencing NK92-K562 binding. NK92 cells and CFSE-labeling K562 cells were starved of serum for 4 h and mixed with equal numbers with or without the presence of 10 μm U0126. A, phosphorylation of Erk1/2 in NK92 cells was analyzed by flow cytometry. NK92 cells ligated with K562 cells were gated and analyzed. The number indicates the mean fluorescence intensity (MFI) of phospho-Erk1/2 in NK92 cells. B, mixture was lysed, and equal amounts of total cell lysate were loaded onto SDS-PAGE gels for Western blot analysis of phosphorylation of Erk1/2. C, cytotoxicity of NK92 cells against K562 with or without the presence of 10 μm U0126 was examined by 4-h ⁵¹Cr release assay. D, NK92- and CFSE-labeled K562 cells were mixed and incubated at 37 °C for different times with or without the presence of 10 μm U0126. Then the cells were fixed and stained with CD56 mAb and analyzed by flow cytometry. For C and D, data were collected from three independent experiments and analyzed by Student's t test; *, p < 0.05.