The tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN; EC 3.1.3.67), a phosphatidylinositol 3′-phosphatase that converts PtdIns(3,4,5)P3 to phosphatidylinositol 4,5-bisphosphate, is one of the three regulators (besides PI3K and SHIP) of the cellular level of phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P3], and one of the most important tumor suppressors by down-regulating the PI3K–Akt–mTOR pathway, through its lipid phosphatase activity[1]. Due to its protein phosphatase activity, PTEN plays an important role as one of the key mediators of downstream GPCR signaling. As such, its role is also emerging as an important factor in other diseases, such as diabetes and autism spectrum disorders. For example, depletion of PTEN enhances the sensitivity of neutrophil to chemoattractant stimulation, augments neutrophil recruitment to sites of infection, and prevents neutrophil death. In a neutropenia-related pneumonia model, PTEN-null neutrophils possess an enhanced bacteria-killing capability, and their recruitment to the inflamed lungs is augmented[2].