1′-acetoxychavicol acetate is a novel nuclear factor κB inhibitor with significant activity against multiple myeloma in vitro and in vivo

1′-Acetoxychavicol acetate (ACA) is a component of a traditional Asian condiment obtained from the rhizomes of the commonly used ethno-medicinal plant Languas galanga. Here, we show for the first time that ACA dramatically inhibits the cellular growth of human myeloma cells via the inhibition of nuclear factor κB (NF-κB) activity. In myeloma cells, cultivation with ACA induced G₀-G₁ phase cell cycle arrest, followed by apoptosis. Treatment with ACA induced caspase 3, 9, and 8 activities, suggesting that ACA-induced apoptosis in myeloma cells mediates both mitochondrial- and Fas-dependent pathways. Furthermore, we showed that ACA significantly inhibits the serine phosphorylation and degradation of IκBα. ACA rapidly decreased the nuclear expression of NF-κB, but increased the accumulation of cytosol NF-κB in RPMI8226 cells, indicating that ACA inhibits the translocation of NF-κB from the cytosol to the nucleus. To evaluate the effects of ACA in vivo, RPMI8226-transplanted NOD/SCID mice were treated with ACA. Tumor weight significantly decreased in the ACA-treated mice compared with the control mice. In conclusion, ACA has an inhibitory effect on NF-κB, and induces the apoptosis of myeloma cells in vitro and in vivo. ACA, therefore, provides a new biologically based therapy for the treatment of multiple myeloma patients as a novel NF-κB inhibitor.