3.4. Reporter Assay

HEK293 cells were seeded into 24-well plates and transfected with 200 ng of the STAT3-reponsive dual luciferase Cignal reporter construct (Qiagen) and 400 ng of the various STAT3 constructs. Attractene transfection reagent (Qiagen) was used to facilitate DNA uptake, and STAT3 activity was assessed 24 h after transfection using a dual luciferase reporter assay system (Promega, Madison, WI, USA) and with luminescence detected using a Pherastar FS (BMG Labtech, Ortenberg, Germany). In some experiments, cells were treated with human IL-6 (R&D systems, Minneapolis, MN, USA) 4 h after transfection.