IFNG and melanoma: To characterize the expression patterns of PD-L1 in melanoma, we investigated cell surface PD-L1 expression in melanoma cell lines and selected six cell lines that constitutively expressed PD-L1 (PD-L1 positive, referred to as PD-L1CON) and six cell lines that expressed PD-L1 only upon induction after treatment with IFN-γ (PD-L1 negative, referred to as PD-L1IND) (Figure 1).