STO feeder cells were passaged every 3 days and cultured at 37 °C/5% CO2, under normoxia conditions, in STO medium. The STO medium contains Dulbecco's modified Eagle's medium (DMEM) (CORNING), 10% fetal bovine serum (FBS) (Vistech, New Zealand), 1% penicillin/streptomycin (P/S) (Thermo Fisher Scientific, cat. no. 15140122), 2 mM GlutaMAX (Thermo Fisher Scientific, cat. no. 35050061), 1% NEAA (Thermo Fisher Scientific, cat. no. 11140050), 0.1% β-mercaptoethanol (Thermo Fisher Scientific, cat. no. 21985023).
The feeder layer was prepared by treating mouse STO feeder cells with mitomycin for 12 h. STO feeder cells were passaged by washing twice with PBS then incubating with 0.05% trypsin/EDTA (Thermo Fisher Scientific, cat. no. 25300062) for 5 min at 37 °C/5% CO2. STO feeder cells were centrifuged at 300g for 5 min with the STO medium. After removing the supernatant, STO feeder cells were resuspended and plated on 0.1% gelatinized 35 mm-tissue culture plastic at a density of 8 × 105 cells. The STO was free from mycoplasma and was detected by PCR.
The feeder layer was prepared by treating mouse STO feeder cells with mitomycin for 12 h. STO feeder cells were passaged by washing twice with PBS then incubating with 0.05% trypsin/EDTA (Thermo Fisher Scientific, cat. no. 25300062) for 5 min at 37 °C/5% CO2. STO feeder cells were centrifuged at 300g for 5 min with the STO medium. After removing the supernatant, STO feeder cells were resuspended and plated on 0.1% gelatinized 35 mm-tissue culture plastic at a density of 8 × 105 cells. The STO was free from mycoplasma and was detected by PCR.