PDCD1 and melanoma: They collected 112 melanoma patients who were undergoing anti-PD-1 immunotherapy, then they examined the gut microbiome of these patients, and they found the diversity and composition of gut microbiota are different between the responders and non-responders: Clostridiales order and Ruminococcaceae family are enriched in responders while Bacteroidales order are enriched in non-responders.