PIP5Kγ-silenced cells exhibit an impaired killing frequency. shRNA-ctr and shRNA-PIP5Kγ–silenced NK92 cells were tested in a ⁵¹Cr-release assay toward 721.221-sensitive target cells for 4 hours and 8 hours. Where indicated, the ⁵¹Cr-release assay was performed in the presence of cycloheximide. (A) Percentage of specific lysis was used to calculate killing frequency as described in the “Degranulation and cytotoxic assay.” Means from 3 independent experiments ± SD are graphed. Differences obtained between shRNA-ctr (gray column) and shRNA-PIP5Kγ (black column) populations at the indicated E:T ratio in the presence of cycloheximide were significant (*P < .05). (B) Data represent the shRNA-ctr (♦) or shRNA-PIP5Kγ (●) percentage (means ± SD) of specific lysis of 3 independent experiments of a standard ⁵¹Cr-release assay. (C) shRNA-ctr and shRNA-PIP5Kγ-silenced primary cultured NK cells or YTS cells were assessed in a ⁵¹Cr-release assay toward K562 and 721.221 targets, respectively. Means from 3 independent experiments ± SD are graphed. Differences between sh-RNA-ctr (gray column) and shRNA-PIP5Kγ (black column) were significant (*P < .05).