To establish whether Plexin-B1 might signal via RhoA/C to promote metastasis in the mouse models of prostate cancer, phosphorylation of myosin light chain (phospho-MLC2Ser19—a marker of ROCK activation (44)) was evaluated in tumors of Ptenfl/flKrasG12V and Ptenfl/flp53fl/fl models (Fig. 5). The gene discussed is RHOA; the disease is prostate cancer.