PLOS ONE · 15 authors, 8 centres
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This study tested a new probiotic powder (containing Lactobacillus plantarum, Bifidobacterium adolescentis, and prebiotics) in a mouse model of colorectal cancer (CRC). The probiotic powder improved survival, reduced tumor size, and restored gut barrier integrity. These benefits were linked to increased Bifidobacterium animalis, decreased Clostridium cocleatum, reduced Treg cells, and enhanced anti-tumor immune responses including CD8+ T cells, Th2 cells, and B cells.
**Background:** Colorectal cancer (CRC) remains a leading cause of cancer-related mortality despite advances in surgery and chemotherapy. Gut microbiota imbalances—including increases in Bacteroides, Fusobacterium, and Campylobacter, and decreases in beneficial bacteria such as Bifidobacterium and Lactobacillus—are closely linked to CRC development. Probiotic-based preparations may prevent gut microbiota disorders and serve as effective therapy against CRC. This study developed a new probiotic powder formulation and evaluated its effects on CRC, gut microbiota composition, immune cell populations, and apoptotic protein expression in a mouse model.
**Methods:** CRC was induced in 6-week-old C57BL/6J male mice using the azoxymethane/dextran sulfate sodium salt (AOM/DSS) method. Eighteen mice per group were assigned to: normal control (NC), CRC control (RC), and CRC plus probiotic powder (CP). The probiotic powder contained Lactobacillus plantarum powder (18%-24%), Bifidobacterium adolescentis powder (18%-24%), stachyose (20%-23%), Lycium barbarum polysaccharides (10%-16%), isomalto-oligosaccharide (2%-5%), and maltodextrin (balance). Mice in the CP group received 0.3 mL physiological saline containing 6.6 mg probiotic powder once daily. Colorectal tissue was assessed by hematoxylin and eosin staining. Gut microbiota was analyzed by 16S rDNA sequencing at weeks 4, 7, 10, and 13. Immune cells from spleen were analyzed by flow cytometry for CD4+ Foxp3+ Treg cells, IFN-γ+ CD8+ T cells, CD4+ IL-4+ Th2 cells, CD4+ CXCR3+ Th1 cells, CD4+ RoRrt+ Th17 cells, CD19+ GL-7+ B cells, and TIGIT expression on Th2 cells. BAX and Bcl-2 protein expression in tumor tissue was measured by western blot.
**Key Results:** The probiotic powder significantly improved survival and reduced tumor volume compared to the RC group. Tumor formation rate was 100% in both RC and CP groups, but average tumor volumes were markedly smaller in the CP group (individual volumes: 29.23, 43.23, 24.12, 32.49, 28.43 mm³) versus the RC group (81.39, 66.06, 208.73 mm³). By day 90, 9 of 18 mice survived in the CP group versus 4 of 18 in the RC group. Histological analysis showed more goblet cells, inflammatory cell infiltration, and relatively complete tissue structure in the CP group compared to the RC group, which exhibited more inflammatory necrosis and crypt abscess. PCoA analysis revealed that the probiotic powder reduced gut microbiota differences between CP and NC groups over time. Two key bacteria were identified: Bifidobacterium animalis was consistently increased by the probiotic powder at all time points, while Clostridium cocleatum was consistently reduced. Flow cytometry showed that the probiotic powder significantly reversed CRC-induced increases in CD4+ Foxp3+ Treg cells (p<0.05), significantly reversed CRC-induced decreases in IFN-γ+ CD8+ T cells (p<0.05), significantly reversed CRC-induced decreases in CD4+ IL-4+ Th2 cells (p<0.05), and significantly reversed CRC-induced increases in TIGIT expression on CD4+ IL-4+ Th2 cells. The probiotic powder also significantly increased CD19+ GL-7+ B cells compared to the RC group (p<0.05). No meaningful changes were observed in CD4+ CXCR3+ Th1 or CD4+ RoRrt+ Th17 cells. Western blot analysis showed that BAX expression was significantly lower in the RC group than the NC group, and the probiotic powder significantly reversed this decrease (p<0.05). Bcl-2 expression was not significantly affected.
**Clinical Implications:** This study demonstrates that a probiotic powder formulation can ameliorate CRC in a mouse model through multiple mechanisms: increasing beneficial Bifidobacterium animalis, reducing potentially harmful Clostridium cocleatum, suppressing immunosuppressive Treg cells, enhancing cytotoxic CD8+ T cell responses, promoting Th2 and B cell activity, reducing TIGIT-mediated immune inhibition, and increasing pro-apoptotic BAX expression. These findings suggest that this probiotic powder has therapeutic potential for CRC, though further studies are needed to evaluate specific mechanisms and potential combinations with other antineoplastic agents such as Chinese herbal medicines or PD-L1 antibodies.