Figure 3.

Effects of STAT1 knockdown in hematopoietic tumor cell lines. K562, KM12BM and IM-9 were stably transduced with two independent shRNAs targeting STAT1 and two irrelevant shRNAs as control. (A) The level of total STAT1 expression was evaluated by flow cytometry and (B) western blot analysis. Controls and STAT1-KO cell lines were incubated with primary purified NK effector cells pre-stimulated with 100 Units/mL IL-2 at 1:1 E/T ratio as described in Methods. (C) Levels of IFNγ secretion in culture supernatants, (D) percent NK cells expressing CD107a/b and (E) Killing of STAT1-KO and control cell lines mediated by fresh purified NK. Bars represent the specific lysis of target cells (mean ± SEM) of four different experiments (∗p < 0.05, ∗∗p < 0.01 compared to the isotype control with the highest reactivity).