NAG-1 up-regulation mediated by EGR-1 and p53 is critical for quercetin-induced apoptosis in HCT116 colon carcinoma cells

Abstract

Quercetin, a flavonoid molecule ubiquitously present in nature, has multiple effects on cancer cells, including the inhibition of cell proliferation and migration. However, the responsible molecular mechanisms are not fully understood. We found that quercetin induces the expression of NAG-1 (Non-steroidal anti-inflammatory drug activated gene-1), a TGF-β superfamily protein, during quercetininduced apoptosis of HCT116 human colon carcinoma cells. Reporter assays using the luciferase constructs contain-ing NAG-1 promoter region demonstrate that early growth response-1 (EGR-1) and p53 are required for quercetinmediated activation of the NAG-1 promoter. Overexpression ofNAG-1 enhanced the apoptotic effect of quercetin, but suppression of quercetin-induced NAG-1 expression by NAG-1 siRNA attenuated quercetin-induced apoptosis in HCT116 cells. Taken together, the present study demonstrates for the first time that quercetin induces apoptosis via NAG-1, providing a mechanistic basis for the apoptotic effect of quercetin in colon carcinoma cells. Keywords Quercetin . NAG-1 . Apoptosis . Sp1 . EGR-1 . p53 . Colon carcinoma cells