Luciferase assay

Cells were seeded in 48-well plates at density of 5×10⁴ cells/well and transfection was carried out with Genefectine. Foxo3a reporter (FHRE-luc), p21 promoter reporter (WWP-luc), p53 reporter (pG13-Luc) or GADD45 promoter reporter (Gadd45-Luc) (Addgene) (200 ng/well) and control reporter (pRL-TK, Promega) (20 ng/well) were used for co-transfection. After 24 h, cells were treated with 20 µM quercetin. Luciferase activities were measured after 24 h in luminometer (Glomax, Promega, CA, US) using a Dual-Luciferase assay kit (Promega), according to the manufacture's recommendations. Value of luciferase activity was normalized to Renilla luciferase activity.