Several
protein tyrosine kinase (PTK) inhibitors predominantly
isoflavones, such as
genistein,
erbstatin,
quercetin,
daidzein, present in red clover, cabbage and alfalfa, show apoptotic effect against
cancer cells. In this study I found that
biochanin, a methoxy form of
genistein, inhibits IL-8-mediated activation of nuclear
transcription factor kappaB (NF-κB) and
activator protein 1 (AP-1) more potently than
genistein as shown in Jurkat T-cell line. Both biochanin and
genistein potently inhibited activity of Lck and Syk, but biochanin specifically inhibited activity of IKK. Biochanin inhibited completely NF-κB activation induced by PMA, LPS,
pervanadate (PV), or H₂O₂, but only partially that induced by TNFα.
Genistein was unable to inhibit IL-8-induced IKK activity, but it blocked PV-induced IKK activity. Biochanin inhibited activation of NF-κB by
TRAF6 completely, but by
TRAF2 partially. In silico data suggested that biochanin interacted strongly with
serine/threonine kinase than
genistein, though both equally interacted with PTK. The data show that both biochanin and
genistein are potent inhibitors of PTK, but biochanin is a potent inhibitor of
serine/threonine kinase too.
Formononetin, having
hydroxyl methoxy group is less potent to inhibit IKK than biochanin. Biochanin inhibits NF-κB activation not only by blocking the upstream IKK, but also PTK that phosphorylate
tyrosine residues of IκBα. Thus, the double-edged sword effect of inhibition of NF-κB via inhibition of both
serine/threonine kinase and PTK by biochanin might show useful therapeutic value against activities of cells that lead to
tumorigenesis and
inflammation.