EpskA21 is an inhibitor for PI3K/AKT signaling pathway, and inhibits the proliferation of cancer cells MCF-7, A549, MIA-PaCa-2, Panc-1 and HepG2, with IC 50 of 1.3-7.24 μM. EpskA21 inhibits the cell migration, arrests the cell cycle at G2/M (MCF-7) and S (MIA-PaCa-2) phase, and induces apoptosis in MCF-7 and MIA-PaCa-2. EpskA21 causes the mitochondrial dysfunction.