Effect of TLR3 agonist on the proliferation and apoptosis of NB cell lines. (A) Cell proliferation assay. After treatment with different doses of poly(I:C) for 24 h, the proliferation of various NB cells was measured by WST-1 assay and expressed as mean ± SD absorbance values of quadruplicate experiments. (B) Apoptosis assay. After treatment with 50 μg/ml poly(I:C) for 24 h, the apoptosis of various NB cells was determined by flow cytometry analysis following propidium iodide staining and expressed as mean ± SD percentages in pre-G0 stage from triplicate experiments. *: P < 0.05.