RalGDS comes of age.

Ras proteins send signals through multiple effector pathways. The Raf/MEK/MAPK and PI 3' kinase pathways are well-validated Ras effectors in human cancers, but many other candidate pathways could be equally important. RalGDS is such a candidate: in a new paper from Chris Marshall's group, an important role for RalGDS in Ras transformation in vivo has been established for the first time. Mice lacking RalGDS are defective in tumor formation, possibly because of increased apoptosis in Ras-driven tumors. The hunt for a clear role for RalGDS activation in human cancer is on.