Compared to controls, at the phylum level, we observed a 20 ± 5% increase of Firmicutes relative abundance similar to PCa patients with high PSA BCR (p = 0.01, two-sided Welch’s t-test) and a 48 ± 14% reduction of Actinobacteria relative abundance (p = 0.001, two-sided Welch’s t-test) in fecal samples of animals with Pten−/−; Rb1−/− tumours but not in the animals with Pten−/−; Rb1+/+ tumours (Fig. 2f). This evidence concerns the gene BCR and neoplasm.