A subsequent investigation of tumorigenesis showed that mice that received the PepT1−/− microbiota had a smaller number of larger tumors (≥2 mm2) and a lower overall tumor burden index (measured as total tumor surface area) compared with mice that received a WT microbiota, in which all tumors were >1 mm2 (Fig. 3l, m). This evidence concerns the gene SLC15A1 and neoplasm.