RHO and melanoma: This data supports using ROCK inhibitors in melanoma to block this pathway downstream of Rho rather than upstream regulators, and builds upon prior work that has shown ROCK inhibition slowing melanoma progression in vivo.15,16,18,42,57 For in vivo validation of candidate migrastatics, we specifically developed a new in vivo traceable model of spontaneous melanoma metastasis (Fig. 3).