Thus, an improvement in anti-CTLA-4 effectiveness may be partially due to the enrichment of B. fragilis. Improved effectiveness of anti-CTLA-4 therapy was also observed in melanoma patients with increased abundance of Bacteroides, Bacteroides thetaiotaomicron, and B. fragilis (Vétizou et al., 2015). This evidence concerns the gene CTLA4 and melanoma.