DNA transfection and luciferase reporter assay

The protocols for DNA transfection and luciferase reporter assays have been previously reported [48, 49]. Briefly, ovarian cancer cells (SKOV3 and MDAH2774) were trypsinized and re-suspended in serum-free RPMI medium (concentration: 10 million cells/mL). Cell suspensions (200 μL) were mixed with 5 μg DNA, transferred to a 2 mm-gap electroporation cuvette, and pulsed at 120 V for 70 msec with a BTX ECM2001 electroporator (Genetronics Inc., San Diego, CA, USA). Cells were subsequently re-seeded into a 6-well plate and maintained in DMEM/F12 with 10% fetal bovine serum for 24 h. ARK2 cells were transfected with Lipofectamine 2000 (Invitrogen) according to the manufacturer’s protocol. Finally, luciferase activity was measured using the Dual luciferase reporter assay system (Promega).