The fact that NECTIN1 downregulation by shRNA and complete NECTIN1 ablation by CRISPR elicited similar cellular phenotypes indicates that both homozygous and hemizygous deletions of NECTIN1, together detected in 55% of patients with melanoma, promote metastasis and that NECTIN1 acts as a haploinsufficient metastasis-suppressor gene. This evidence concerns the gene NECTIN1 and melanoma.