ARHGEF1 and melanoma: Whereas NK cell- and macrophage-specific ablation of ARHGEF1 did not result in reduced frequency of lung metastases after intravenous administration of B16 melanoma cells, we found that T cell-specific ablation of ARHGEF1 in Arhgef1fl/flCd4cre mice (hereafter Arhgef1-cKO mice) resulted in markedly reduced lung metastasis compared with Arhgef1+/+Cd4cre (hereafter cWT) controls (Fig. 1i–l and Extended Data Fig. 3a), recapitulating the resistance to metastasis observed in mice lacking ARHGEF1 in all tissues.