In the course of modeling malignant melanoma in a tyrosinase promoter transgenic system, we developed a genetically-engineered mouse (GEM) model of invasive prostate cancers, whereby an activating mutation of BRAF(V6</span>00E)--a mutation found in approximately 10% of human prostate tumors--was targeted to the epithelial compartment of the prostate gland on the background of Ink4a/Arf deficiency.