PDCD1 and cancer: In 2023, a pan-cancer immunotherapy response study built a predictive model based on endothelial senescence and showed that the machine learning algorithm “KKNN” had the highest AUC for response at 0.75 in the anti-PD-1/PD-L1 treated melanoma cohort (PUCH SKCM, 2021), while in other melanoma immunotherapy cohorts the AUC decreased to around 0.5, and the AUC for OS was even lower (32).