Cell culture and transfection

The HaCaT keratinocyte cell line was kindly provided from Prof. Do-Young Yoon (Konkuk University, Seoul, Korea). These cells were grown at 37 °C in DMEM medium supplemented with 10% FBS, penicillin (100 units/ml) and streptomycin sulfate (100 μg/ml) in humidified atmosphere of 5% CO₂. Cells were incubated with K284 at various concentrations (0.5, 1 and 2 μM; dissolved in DMSO) and then stimulated with the TNF-α and IFN-γ (20 ng/ml) combination for the indicated time points in figure legends. The final concentration of DMSO used was less than 0.05%. Cells were treated with 0.05% DMSO as vehicle control. For transfection, HaCaT cells were transiently transfected with CHI3L1 plasmid vector, CHI3L1 siRNA or LTF siRNA, using Lipofectamine 3000 (for plasmid vector) and RNAiMAX (for siRNA) reagent in Opti-MEM, according to the manufacturer's specifications. CHI3L1 siRNA and LTF siRNA were purchased from Origene (Rockville, MA, USA).