Résumé
A large effort has been made to understand the intracellular function of a novel tumor-suppressor gene, PTEN, recently identified in the 10q23 chromosome region that is often altered in human tumors. PTEN is a multifunctional protein endowed with a phosphatase activity capable of dephosphorylating not only proteins, at tyrosine, serine or threonine residues, but also phospholipids of the phosphatidylinositol pathway. Its protein phosphatase activity allows it to inhibit the Ras/Mek/Erk cascade, as well as FAK, the focal adhesion kinase, and thus to affect the interactions of cells with intracellular matrix which are important in the mechanism of invasion. Its lipid phosphatase activity blocks the PI3K/Akt pathway, provokes an arrest in G1 of the cell cycle and an increased sensitivity to apoptosis. PTEN therefore acts simultaneously on the morphology and the proliferation of tumoral cells and has thus been attributed a major role in tumor suppression.