CD80 and melanoma: Initial studies of CD80-transfected human melanoma and lung adenocarcinoma cells that constitutively express PD-L1 or are induced by IFNγ to express PD-L1 suggested that CD80 inhibited the plasma membrane expression of PD-L1, despite the transfected cells containing PD-L1 mRNA and protein as assessed by RT-PCR and western blotting.