Gopalakrishnan et al. showed that in melanoma patients, a higher level of Faecalibacterium prausnitzii, Ruminococcus bromii, Enterococcus faecium, Collinsella aerofaciens, Bifidobacterium adolescentis, Klebsiella pneumoniae, Veillonella parvula, Parabac-teroides merdae and Lactococcus formicus correlated with a better response to anti-PD-1 immunotherapy [49,61,62,65]. This evidence concerns the gene PDCD1 and melanoma.