Denbinobin inhibits nuclear factor-kappaB and induces apoptosis via reactive oxygen species generation in human leukemic cells.

Denbinobin, a 1,4-phenanthrenequinone firstly isolated from the stems of Dendrobium moniliforme (Shi-Hu in Chinese medicine), has been reported to exhibit anti-tumoral and anti-inflammatory activities through mechanism(s) not yet fully understood. Because of the critical role of the transcription factor NF-kappaB and of ROS-induced activation of stress regulated kinases in tumorigenesis, we have investigated the effect of denbinobin on these pathways. We found that denbinobin is a potent inhibitor of TNFalpha and PMA-induced NF-kappaB activation, and that it can block the phosphorylation and degradation of IkappaBalpha by inhibiting TAK1 activity, an event lying upstream of IKK activation.