PDCD1 and melanoma: We extracted a set of hot tumor signature genes from a previous study (Dong et al., 2021) and distinguished melanoma samples into hot and cold tumor samples by using of hot tumor signature genes (CXCR4, CD274, CXCL9, CXCL10, CXCL11, CD4, CXCR3, CD3E, CCL5, PDCD1, CD8A and CD8B).