Calorie restriction remodels gut microbiota and suppresses tumorigenesis of colorectal cancer in mice

Abstract

Colorectal cancer (CRC) is one of the most common cancers worldwide and the consumption of a high‑calorie diet is one of its risk factors. Calorie restriction (CR) slows tumor growth in a variety of cancers, including colorectal cancer; however, the mechanism behind this remains unknown. In the present study, CR effectively reduced the tumor volume and weight in a xenograft BALB/c male nude mouse model. In addition, tumor immunohistochemistry revealed that the CR group had significantly higher expression of Bax (P&lt;0.001) and significantly lower levels of Bcl2 (P&lt;0.0001) and Ki67 (P&lt;0.001) compared with control group. Furthermore, data from 16S ribosomal (r)RNA sequencing implied that CR was able to reprogram the microbiota structure, characterized by increased <em>Lactobacillus</em> constituent ratio (P&lt;0.05), with amelioration of microbial dysbiosis caused by CRC. Further receiver operating characteristic curves demonstrated that the bacteria Bacteroides [area under the curve (AUC)=0.800], <em>Lactobacillus</em> (AUC=0.760) and <em>Roseburia</em> (AUC=0.720) served key roles in suppression of CRC in the mouse model. The functional prediction of intestinal flora indicated ‘cyanoamino acid metabolism’ (P&lt;0.01), ‘replication initiation protein REP (rolling circle plasmid replication)’ (P&lt;0.01), ‘tRNA G10 N‑methylase Trm11’ (P&lt;0.01) and ‘uncharacterized protein with cyclophilin fold, contains DUF369 domain’ (P&lt;0.05) were downregulated in CR group. These findings implied that CR suppressed CRC in mice and altered the gut microbiota.

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