Cell culture and ultraviolet (UV) B treatment of HaCaT cells

HaCaT keratinocytes (human skin keratinocyte line) were kindly provided by Ph.D. Kim (Kyung Hee University, Gyeonggi, Korea). The cells were grown in DMEM containing 10% FBS and 1% antibiotics at 37°C in a humidified atmosphere containing 5% CO₂. UV irradiation was performed using a UV lamp with a wavelength of 290~320 nm, and the amount of light was measured using UV-340A (Lutron Electronic Enterprise Co., Ltd., Taipei, Taiwan).