siRNA knockdown of TLR4 expression in the human liver cancer HepG2 cell line. (A) Results of reverse transcription-polymerase chain reaction of RNA extracted from HepG2 cells transfected with siRNA-1, −2 or −3, the blank control, negative siRNA or Lipo. β-actin mRNA was amplified as a control. (B) Levels of TLR4 mRNA expression in HepG2 cells transfected with siRNA-1, −2 or −3 and the three control groups. The data are expressed as the mean ± SD of TLR4 mRNA levels for each group. *P<0.05 vs. control groups (blank control, negative siRNA-transfected and Lipo-transfected cells). (C) Western blotting of protein extracted from siRNA-1-transfected, blank control, negative siRNA-transfected and Lipo-transfected HepG2 cells. β-actin was included as a loading control. (D) Levels of TLR4 protein expression in HepG2 cells transfected with siRNA-1, −2 or −3 and the three control cells, assessed using western blotting. The data are expressed as the mean ± SD of TLR4 protein levels for each group. *P<0.05 vs. control groups (blank control, negative siRNA-transfected and Lipo-transfected cells). Students t-test and analysis of variance were used to determine the significance of differences between groups. siRNA, small interfering RNA; TLR4, Toll-like receptor 4; Lipo, Lipofectamine 2000; mRNA, messenger RNA; SD, standard deviation.