2.2 Dual luciferase screening assay
Both Firefly and Renilla luciferase activities were measured using the Dual-Luciferase Reporter Assay System (Promega, Madison, WI, USA) according to the manufacturer’s instructions. 293T cells were plated in 24-well culture plates and co-transfected transiently with the STAT3-luc and Renilla plasmids using Lipofectamine 2000 (Invitrogen, Carlsbad, CA, USA). After incubation for 24 h, the transfected cells were stimulated with recombinant human interleukin-6 (Roche) and treated with TA (0, 0.1, and 1 μM) for 12 h. Afterwards, the cell lysates were prepared and the activities ofFirefly and Renilla luciferases were quantified using a Veritas Microplate Luminometer (Turner Biosystems, Sunnyvale, CA, USA). The data were expressed as the ratio of Firefly to Renillaluciferase activity.