Lactobacillus fermentum V3 ameliorates colitis-associated tumorigenesis by modulating the gut microbiome

Lactobacillus spp., a common probiotic used as a dietary supplement, is good for the digestive system. However, its anti-cancer activity still remains unclear. In this study, we aim to examine the effect of Lactobacillus fermentum, Lactobacillus acidophilus and Lactobacillus rhamnosus on azoxymethane/dextran sulfate sodium (AOM/DSS)-induced colitis-associated cancer. Male ICR mice were injected with 10 mg/kg AOM and 2.5% DSS via drinking water, and then fed with different Lactobacillus (1 × 10⁸ CFU/day) for 14 weeks. The colonic tissues were collected for biomedical analysis, and gut microbiota profiling was detected by next generation high-throughput sequencing comparing to the 16S rRNA gene. We found that pretreatment with Lactobacillus fermentum (Lac.ferm) significantly inhibits colonic tumor formation (P < 0.05) and markedly decreases pro-inflammatory cytokines in AOM/DSS-induced mice. Furthermore, 16S rRNA sequencing data showed that Lac.ferm altered the composition of gut microbiota by reducing the percentage of Bacteroides. Moreover, linear discriminant analysis scores revealed that Lactobacillus fermentum within phylum Firmicutes was the prominent species existing in the Lac.ferm-treated group. Overall, the above findings suggest that dietary Lac.ferm could modulate the gut microbial community, which might be beneficial to alleviating colon cancer progression.