PDCD1 and melanoma: Given that the expression of PD-L1 on tumor cells has predictive value for the response to antibody-based monotherapies in many studies, especially those on melanoma and NSCLC6,16,17, and because inhibition of PD-L1 expression in tumor cells in combination with anti-PD-L1 or anti-PD-1 antibody immunotherapy can effectively suppress the growth of various tumors18,19, fully understanding the regulation of PD-L1 expression is vital for improving the clinical efficacy of relevant anticancer agents.