PDCD1 and melanoma: The fact that l-fuc does not alter the cell surface levels of PD-L1 in human or mouse melanoma cells (Extended Data Fig. 6a), suggesting that the discrepant tumor suppression by single-agent versus combination l-fuc and anti-PD1 therapy in our SW1 and SM1 mouse models (Fig. 5a), is attributed to determinants beyond the PD1–PD-L1 axis.