Catalase suppression‐mediated H₂O₂ accumulation in cancer cells by wogonin effectively blocks tumor necrosis factor‐induced NF‐κB activation and sensitizes apoptosis

Abstract

Tremendous effort has been made to improve the anticancer value of tumor necrosis factor (TNF). In this study, we show that wogonin, a flavonoid isolated from Huang-Qin (Scutellaria baicalensis), synergistically sensitizes cancer cells derived from the cervix, ovary and lung to TNF-induced apoptosis, which was associated with inhibition of catalase activity and an increase of cellular hydrogen peroxide (H(2)O(2)). Wogonin-induced reactive oxygen species block TNF-induced NF-κB activation through inhibiting phosphorylation on the NF-κB p65 subunit and consequently the DNA binding of NF-κB. In addition, wogonin suppressed the expression of the antiapoptotic factor c-FLIP, which is accompanied with potentiation of TNF-induced caspase 8 activation that initiates apoptosis. Importantly, wogonin did not sensitize normal bronchial epithelial cells to TNF-induced cell death, which was associated with the defect in induction of H(2)O(2). Thus, wogonin specifically sensitizes cancer cells to TNF-induced cytotoxicity through H(2)O(2)-mediated NF-κB suppression and apoptosis activation. Our data provide important insights into the molecular mechanism underlying wogonin's anticancer activity, and suggest this common flavonoid could be used as a TNF adjuvant for cancer therapy.