Multiple myeloma(MM)is one of the most common hematological malignancies and to date,it remains an incurable disease.In this study,we evaluated the inhibitory effect of 5-acetyloxy-6,7,8,4′-tetramethoxyflavone(5-ATMF),a compound from aged citrus peel extracts,on the MM U266 cell line.We found that the compound inhibited cell growth and induced cell apoptosis in multiple apoptotic assays.The apoptotic proteins caspase-3,caspase-9,and PARP(poly ADP-ribose polymerase)were cleaved when cells were treated with 5-ATMF.Along with the apoptosis process,the anti-apoptotic protein,Bcl-2(B-cell lymphoma-2),was significantly downregulated and the pro-apoptotic protein,Bax(Bcl-2 associated X protein),upregulated along with the release of cytochrome C(Cyt c)and the reduction of mitochondrial membrane potential(MMP).Notably,we found that the phosphorylation of Bad(Bcl-2/Bcl-XL-associated death promoter)was decreased but Bad remained unchanged in this process.On adding 5-ATMF to U266 cells,we observed that 5-ATMF repressed the phosphorylation of Akt(PKB Protein Kinase B PKB),thereby increasing the release of Cyt c and inhibiting the phosphorylation of Bad.These effects were enhanced by Ly294002,an inhibitor of Akt.These results suggested that 5-ATMF exerts a pro-apoptotic effect on U266 cells,possibly associated with the mitochondrial apoptotic pathway induced by the PI3K/Akt/Bad pathway.
