PTEN: a default gate-keeping tumor suppressor with a versatile tail. 
The tumor suppressor PTEN controls a variety of biological processes including cell proliferation, growth, migration, and death.  As a master cellular regulator, PTEN itself is also subjected to deliberated regulation to ensure its proper function.  Defects in PTEN regulation have a profound impact on carcinogenesis.  In this review, we briefly discuss recent advances concerning PTEN regulation and how such knowledge facilitates our understanding and further exploration of PTEN biology.  The carboxyl-tail of PTEN, which appears to be associated with multiple types of posttranslational regulation, will be under detailed scrutiny.  Further, a comparative analysis of PTEN and p53 suggests while p53 needs to be activated to suppress tumorigenesis (a dormant gatekeeper), PTEN is probably a constitutive surveillant against cancer development, thus a default gatekeeper.