Probiotic strain Lactobacillus plantarum YYC-3 prevents colon cancer in mice by regulating the tumour microenvironment

The gut microbiota plays important roles in chronic inflammation and colon cancer. Lactobacillus is a gut-resident probiotic with benefits to host health. We recently identified Lactobacillus plantarum strain YYC-3 with strong inhibition against two colon cancer cell lines (HT-29 and Caco2). However, the inhibitory effect of YYC-3 against colon cancer in vivo has not been verified. Thus, in the present study, we explored the probiotic function of strain YYC-3 and its cell-free supernatant (YYCS) respectively in the APC^Min/+ mouse model of colon cancer during tumour development and growth, and the underlying anti-cancer mechanism. Treatment of both strain YYC-3 and the YYCS prevented the occurrence of colon tumours and mucosal damage in APC^Min/+ mice fed a high-fat diet, although YYC-3 had a stronger anti-cancer effect. The mechanism involved modulation of the immune system and downregulated expression of the inflammatory cytokines interleukin (IL)-6, IL-17 F, and IL-22, along with reduced infiltration of inflammatory cells. Moreover, YYC-3 suppressed activation of the NF-κB and Wnt signalling pathways, and restored the altered gut microbiota composition to closely match that of wild-type mice. These results lay a theoretical foundation for application of YYC-3 in colon cancer prevention.