PTEN: a tumour suppressor that functions as a phospholipid phosphatase

The tumour suppressor PTEN has been implicated in a large number of human t umours and is conserved from humans to worms. Characterization of PTEN prot ein showed that it is a phosphatase that acts on proteins and on 3-phosphor ylated phosphoinositides, including phosphatidylinositol (3,4,5)-trisphosph ate, and can therefore modulate signal-transduction pathways that involve l ipid second messengers. Recent results indicate that at least part of its r ole is to regulate the activity of the serine/threonine kinase AKT/PKB, and thus influence cell survival signalling. This article discusses the functi on of PTEN and how this could be linked to its activity as a tumour suppres sor.