Curcumin inhibits APC/C activity. A, DAOY cells were released from thymidine/nocodazole block in the presence of 0, 20 and 40 μM curcumin for indicated time points. Cell lysates were subjected to immunoblotting with antibodies shown. Arrow indicates phosphorylated Cdc27, while the arrowhead shows unphosphorylated Cdc27. B, Mitotically arrested DAOY cells were released with different concentrations of curcumin for 2 and 4 h, respectively, and blotted with antibodies indicated. C, DAOY cells were synchronized by double thymidine arrest and then incubated with curcumin for 8 h. Cell lysates were subjected to immunoprecipitation with anti-Cdc27 antibodies. Immunoprecipitated proteins were immunoblotted with antibodies indicated. Immunoblots of total cell lysates are shown to ensure equal loading D, Mitotically arrested DAOY cells were released in the presence of either DMSO or curcumin for indicated time points and APC/C activity was determined as described in Materials and Methods.