Phosphatases as small-molecule targets: inhibiting the endogenous inhibitors of kinases

Inositols and their phosphorylated derivatives, phosphoinositides, play an important role in diverse cellular functions. They have been recognized as second messengers and are accurately controlled by phosphatases and kinases, such as phosphoinositide 3-kinase and the phosphatidylinositol 3-phosphatase PTEN (phosphatase and tensin homologue deleted on chromosome 10). Specific inhibitors targeting phosphoinositide 3-kinase and protein phosphatases have been described and characterized, but no small-molecule tools for phosphoinositide phosphatases are currently available. The present mini-review gives an overview of representative phosphatase inhibitors and summarizes the work that has been done recently on molecules that inhibit PTEN.