Even though several studies have reported a susceptible oncogenic character of P27 in tumors treated by preussin or proteasome inhibitors, they have not clarified the underlying mechanism.48, 49, 50 Our study for the first time revealed P27 functioned as a protective protein for tumor cells by suppressing ROS generation, modulating the profile of BCL-2 family members and maintaining the normal mitochondrial status in gastric cancer cells treated with MLN4924. This evidence concerns the gene BCL2 and gastric cancer.