PDCD1 and melanoma: NLRP3 inflammasomes in melanoma cells can be activated by a combination of agonistic anti-PD-L1 antibody and IFN-γ through PD-L1/STAT3/protein kinase R (PKR) signal axis or direct contact of tumor cells and antigen-specific CD8+ T cells at the existence of anti-programmed cell death protein-1 (PD-1) [199].