3-Formylchromone (3-FC) has been associated with anticancer potential through a mechanism yet to be elucidated. Because of the critical role of NF-κB in
tumorigenesis, we investigated the effect of this agent on the NF-κB activation pathway. Whether activated by inflammatory agents (such as TNF-α and
endotoxin) or
tumor promoters (such as
phorbol ester and
okadaic acid), 3-FC suppressed NF-κB activation. It also inhibited constitutive NF-κB expressed by most
tumor cells. This activity correlated with sequential inhibition of IκBα
kinase (IKK) activation, IκBα phosphorylation, IκBα degradation, p65 phosphorylation, p65 nuclear translocation, and reporter gene expression. We found that 3-FC inhibited the direct binding of p65 to
DNA, and this binding was reversed by a
reducing agent, thus suggesting a role for the
cysteine residue. Furthermore, mutation of Cys38 to Ser in p65 abolished this effect of the
chromone. This result was confirmed by a docking study. 3-FC also inhibited IKK activation directly, and the
reducing agent reversed this inhibition. Furthermore, mutation of Cys179 to Ala in IKK abolished the effect of the
chromone. Suppression of NF-κB activation led to inhibition of anti-apoptotic (Bcl-2, Bcl-xL,
survivin, and cIAP-1), proliferative (
cyclin D1 and COX-2), invasive (MMP-9 and ICAM-1), and angiogenic (
VEGF) gene products and sensitization of
tumor cells to
cytokines. Thus, this study shows that modification of
cysteine residues in IKK and p65 by 3-FC leads to inhibition of the NF-κB activation pathway, suppression of anti-apoptotic gene products, and potentiation of apoptosis in
tumor cells.