In vitro comparison of transfection efficiencies. In vitro comparison of transfection efficiencies of LPEI/siRNA-EGFR under various N/P ratios (black panels), LPEI/siRNA-NEG (grey panels), and Lipofectamine/siRNA-EGFR (white panel) transfected groups. SPC-A1 cells were seeded into 6-well plates at 3 × 105 cells/well and, at ~50% confluency, transfection was performed as indicated. Cells were harvested (A) after 24 hours for quantitative expression of EGFR mRNA by real-time RT-PCR analysis, (B) and after 48 hours for EGFR protein by flow cytometry assays. Data are expressed as means±s.d. of numbers obtained from 6 animals in each group. All the results are shown as the mean±standard error of the mean (SEM). * P<0.05 when compared with respective LPEI/siRNA-NEG groups. ‡ P<0.05 when compared with LPEI/siRNA-EGFR group at different N/P ratios.