PDCD1 and melanoma: An initial proteomics analysis of the clinical samples from advanced-stage melanoma patients undergoing either tumor-infiltrating lymphocyte (TIL)-based or anti-PD-1 immunotherapy has shown that oxidative phosphorylation in general melanoma tissues is significantly higher in responders than in non-responders in both treatments, indicating that mitochondrial function can be used as a potential biomarker for predicting the response to immunotherapy (21).