Lipoplexes were obtained by mixing 125 μL of the diluted Lipofectamine 3000 with 125 μL of the diluted plasmid. After a 10 min incubation the lipoplexes were added to the HEK293 cells and incubated at 37 °C/5% CO2. After 24h, the media was replaced and changed to full culture medium containing geneticin (0.6 mg/mL) to select transfected cells. Transfectants were selected under this condition for 14 days and the stably transfected cells were maintained in 0.6 mg/ml geneticin.