Furthermore, immunotherapy by ipilimumab has modified the gut microbiome in metastatic melanoma patients at the genus level, leading to a rapid decrease of bacterial species from Bacteroidales and Burkholderiales with a relative abundance of Clostridiales. The effect of anticancer therapy was improved by fecal transplantation, documenting the key role of Bacteroidales in the immunostimulatory effects of CTLA-4 blockade [117]. This evidence concerns the gene CTLA4 and metastatic melanoma.