PAK4 and melanoma: To validate loss of functionality at the PAK4 kinase domain, we evaluated whether B16 PAK4 KD cells had decreased phosphorylation of β-catenin S675 and reduced response to Wnt-3a stimulation, as we have previously observed in B16 PAK4 KO cells as well as in human melanoma PAK4 KO cells (Supplementary Fig. S8).