PDCD1 and neoplasm: Last, the analysis of variations of CCL25 expression in tumor samples from patients with melanoma treated with anti–PD-1 (table S4) revealed that only responders displayed a significantly increased ratio between CCL25 levels before and after ICB (Fig. 7B), suggesting that CCL25 bears the potential of being a predictive biomarker of antitumor response by ICB.