PXN and breast cancer: RhoU has recently been reported to increase paxillin phosphorylation in MDA-MB-231 breast cancer cells.15 Paxillin is a scaffolding component in focal adhesion complexes and serves as a platform to integrate adhesion signaling.24 RhoU overexpression increased phospho-paxillin (pS272) levels in a PAK4-depleted background, and RhoU associated with paxillin.15 RhoU might provide a scaffold to recruit an additional kinase to induce paxillin S272 phosphorylation, possibly via JNK activation.3,20