BAK1 and neoplasm: PI3K is a major pathway for tumor cell growth and migration and has a pro-proliferative and inhibitory effect on apoptosis, while as an upstream signaling molecule of Bcl-2, the pro-apoptotic protein Bak was confirmed to be reduced in expression under the action of PYR26, and the present study demonstrated by Western blot that PYR26 down-regulated PI3K protein expression significantly.