MAP2K1 and neoplasm: Through the use of inhibitors of MEK1 and H/N-Ras, studies have reported the importance of the Erk1/2 signaling in transformation of NIH3T3 and rat kidney epithelial cells (RK3E) cells by the JSRV Env protein [12] and more recently, activation of the Erk pathway has been reported in Env-mediated tumor development in FVB mice [33].