PTEN and cancer: PTEN can be selectively packaged into exosomes via the Ndfip/Nedd4-dependent ubiquitin ligase system and secreted by cancer cells (Ndfip is an adaptor protein for members of the Nedd4 family of E3 ubiquitin ligase; it enables Nedd4 to ubiquitinate targets such as PTEN, regulating their trafficking and secretion (including via exosomes)) [66, 67].