PDCD1 and melanoma: In this study, we characterized the expression landscape of circRNAs using total RNAseq data from two melanoma patient cohorts, including 88 melanoma patients treated with single-agent anti-PD-1 or combined anti-CTLA-4 and anti-PD-1 immunotherapy54, and 69 melanoma patients treated with anti-PD-1 therapy55.