Gut microbiota Eubacterium callanderi exerts anti-colorectal cancer activity

Abstract

The gut microbiota (GM) is associated with colorectal cancer (CRC) development. However, studies demonstrating the role of GM in CRC are limited to metagenomic analyses. These studies lack direct evidence proving that the candidate strains are involved in CRC, and isolated probiotics for bacteriotherapy. Therefore, to identify novel GM with anti-CRC activity, we previously isolated gut bacteria from the feces of healthy individuals, screened the isolated GM's anti-CRC activity, and discovered that cell-free supernatants of GM isolates demonstrated antiproliferative activity against CRC cells. Here, our study identified one of them as Eubacterium callanderi and chose it for further study because the genus Eubacterium has been suggested to contribute to various aspects of gut health; however, the functions are unknown. First, we confirmed that E. callanderi cell-free supernatant (EcCFS) exerted antiproliferative activity-by inducing apoptosis and cell cycle arrest-that was dose-dependent and specific to cancer cell lines. Next, we discovered that EcCFS active molecules were heat stable and protease insensitive. High-performance liquid chromatography analysis revealed that EcCFS contained high butyrate concentrations possessing anticancer activity. Additionally, gas chromatography-mass spectrometry analysis of the aqueous phase of ethyl acetate-extracted EcCFS and an antiproliferation assay of the aqueous phase and 4-aminobutanoic acid (GABA) suggested that GABA is a possible anti-CRC agent. Finally, in the CT26 allograft mouse model, E. callanderi oral administration and EcCFS peri-tumoral injection inhibited tumor growth in vivo. Therefore, our study reveals that E. callanderi has an anti-CRC effect and suggests that it may be a potential candidate for developing probiotics to control CRC.