A reporter construct (0.2 μg) was mixed with 20 ng/ml of a control vector pRL-TK in 50 μl of OPTI-MEM (Invitrogen Corp., Carlsbad, CA). The solution was mixed with 1 μl of Lipofectamine (Invitrogen Corp.), diluted in 150 μl of OPTI- MEM, and incubated at room temperature for 30 min; two vectors in 200 μl solution were co-transfected into RGM1 cells after the cells were washed twice with OPTI-MEM. The cells were incubated at 37 °C for 24 h in a 5% CO2 atmosphere. The medium was replaced with DMEM/F12 Ham supplemented with 10% FBS, and plaunotol was added to the reaction. After 6 h of culture, cells were harvested and assayed with a PicaGene Dual-Luciferase Assay kit (PG-DUAL SP, Toyo Ink Co. Ltd., Tokyo, Japan) according to the manufacturer's instructions.