Figure 3.

In vitro cytotoxicity assay. SNU-761 cells were incubated with VPA (5 mM) or vorinostat (2 μM) for 40 hours, and aliquots of 2 × 10⁵ target cells/mL were prepared. Human CIK cells (effector cells) were obtained from mononuclear cells cultured with interleukin 2 and immobilized monoclonal antibody to CD3, and centrifuged cells were resuspended to 3×10⁶ cells/mL in RPMI 1640 with FBS 1%. For the in vitro cytotoxicity assay, each well consisted of 50 μl of target cells and 100 μl of effector cells. After a 4-hour incubation period, treated cells were centrifuged, and the optical densities of supernatants were measured. Both VPA (5 mM) and vorinostat (2 μM) significantly increased CIK cell cytotoxicity against SNU-761 cells (control: 22.2 ± 7.6; VPA: 60.40 ± 10.16, P < 0.001; vorinostat: 56.54 ± 9.73, P < 0.001).