PTEN: an intercellular peacekeeper?

It is generally assumed that cells synthesize their own intracellular enzymes. Therefore, if expression of a specific gene is silenced in a potential cancer cell, it is expected that loss of protein function will follow. A provocative study indicates an unexpected mechanism of intercellular tumor suppression, showing that PTEN (phosphatase and tensin homolog deleted from chromosome 10), a cytosolic enzyme, can be transferred between cells in exosomes to suppress signaling and proliferation in target cells.