STAT3-dependent dual-luciferase assay: HCT-116 cells are transiently transfected with reporter plasmid having the STAT3-binding element for regulating luciferase assay. Cells are treated with Cryptotanshinone for 24 hours at a concentration range of 0.2 to 50 μM. After treatment, cells are harvested in 20 μL of passive lysis buffer and luciferase activity is evaluated by the Dual Luciferase Reporter Assay kit on Wallac Victor2. The concentration of Cryptotanshinone that inhibits the luciferase activity by 50% represents IC50 value.
RAW264.7 cells are maintained at subconfluence in 95% air and 5% CO2 humidified atmosphere maintained at 37°C. The medium used for routine subculture is Dulbecco's Modified Eagle's Medium supplemented with 10% fetal bovine serum, penicillin (100 units/mL) and streptomycin (100 μg/ mL). An MTT assay is used to measure the viability of the cells after treatment with puerarin. After the supernatants are removed for nitrite determination, cells are incubated at 37°C with MTT (0.05 mg/mL) for 4 h, and the optical density is measured at 540 nm. The concentrations of puerarin are10, 20, 40 and 100 μM[1].