AML stem cell. OSU-2S binds to SET (PDB: 2E50), displacing it from the protein phosphatase 2A (PP2A) heterotrimer (PDB: 2IAE), thus increasing phosphatase activity. In AML stem cells, activated PP2A results in reduced expression of cMYC and subsequent induction of p21, leading to inhibition of leukemia-initiating cell proliferation and survival and terminal myeloid differentiation.