The association of intestinal barrier state biomarkers and Ig-bound stool microbiota signatures with clinical outcomes of anti-PD-1 therapy in the study cohort suggests that intestinal barrier functionality may contribute to shaping anti-cancer immune responses in advanced melanoma patients undergoing anti-PD-1 therapy, potentially through the interaction with the gut microbiota and/or whole-body immunity. The gene discussed is PDCD1; the disease is cancer.