We first tested pairs of isogenic melanoma cell lines, which differ in outcome after transplantation to immunocompromised mice, for expression of NLGN4X: MCM1G (non-metastatic) and MCM1DLN (metastatic), as well as, WM793B (non-tumorigenic) and 1205Lu (metastatic) melanoma cell lines. Here, NLGN4X is linked to melanoma.