(A) 1205Lu cells were treated with siRNAs specific for RIG-I or MDA-5 or with control siRNA (Ctrl) for 48 hours. Then cells were treated (+) with pppRNA or poly(I:C) (3 ng/ml) or with transfection reagent alone (–). Expression of RIG-I and MDA-5 mRNA was analyzed by quantitative RT-PCR. Mean ± SD of 3 independent experiments is shown. rel. U, relative units. (B) 1205Lu cells were treated with siRNAs and pppRNA or poly(I:C) (5 ng/ml) as described for A and analyzed for apoptosis by FACS. Annexin V–positive and propidium iodide–negative cells are represented. Mean ± SD of 3 independent experiments is shown. *P ≤ 0.05 compared with control siRNA–transfected cells treated with pppRNA. (C) 1205Lu cells were treated with siRNA specific for TLR3 or control siRNA and pppRNA, poly(I:C), or transfection reagent alone as described for A. Left: Quantification of TLR3 mRNA by quantitative RT-PCR. Right: Analysis of apoptotic cells. Mean ± SD of 3 independent experiments is shown. (D) 1205Lu cells were treated with siRNA specific for PKR or control siRNA and pppRNA, poly(I:C), or transfection reagent alone as described for A. Left: Quantification of PKR mRNA by quantitative RT-PCR. Right: Analysis of apoptotic cells. Mean ± SD of 3 independent experiments is shown.