2.2. Cell culture
RGM1 cells were cultured in Dulbecco's Modified Eagle's Medium (DMEM)/F12 Ham (Sigma Chemical Co.) supple- mented with 10% fetal bovine serum (FBS; Sigma Chemical Co.) and 1% anticiobitics/antimycotic (AA; Invitrogen Corp., Carlsbad, CA) at 37 °C in 5% CO2 atmosphere.