The effect of SET knockdown or overexpression on granzyme B and perforin expression. (A) pSUPER or pSUPER.retro-shSET NK-92 cells were starved from IL-2 for 48 hours and analyzed for granzyme B protein expression by Western blot (left), intracellular flow cytometry (middle), and granzyme B transcript by real-time RT-PCR (right; n = 6). *P < .01. (B) Primary human CD56⁺ NK cells sorted for GFP after lentivirus infection using pNaldini-GFP and pNaldini-GFP-SET vectors were cultured overnight without IL-2 and analyzed for granzyme B protein by Western blot (left) and granzyme B mRNA expression by real-time RT-PCR (right; n = 7). **P = .03. In data not shown, primary human NK cells were also retrovirally infected using PINCO-SET vector, and an 8-fold increase in granzyme B mRNA relative to identical cells infected with PINCO alone was noted. (C) pSUPER or pSUPER.retro-shSET NK-92 cells were starved from IL-2 for 48 hours and analyzed for perforin protein expression by Western blot. Each experiment is representative of at least 3 performed with similar results.