We observed that the Shannon index of the microbiota of Pten−/−; Rb1−/− mice was reduced by 19 ± 8% compared to mice without tumours (p = 0.02, two-sided Welch’s t-test), but not for Pten−/−; Rb1+/+ tumour bearing mice (Fig. 2g). This evidence concerns the gene RB1 and neoplasm.