Cell-Free Supernatant of Odoribacter splanchnicus Isolated From Human Feces Exhibits Anti-colorectal Cancer Activity

Abstract

The gut microbiota (GM) has been shown to be closely associated with the development of colorectal cancer (CRC). However, the involvement of GM is CRC has mainly been demonstrated by metagenomic profiling studies showing the compositional difference between the GM of healthy individuals and that of CRC patients and not by directly studying isolated gut microbes. Thus, to discover novel gut microbes involved in CRC, we isolated the GM from the feces of healthy individuals and evaluated its anti-CRC activity in vitro and in vivo. After GM isolation, cell-free supernatants (CFSs) were prepared from the isolated gut microorganisms to efficiently screen a large amount of the GM for anti-proliferative ability in vitro. Our results showed that the CFSs of 21 GM isolates had anti-proliferative activity against human colon cancer HCT 116 cells. Of these 21 GM isolates, GM07 was chosen for additional study because it had the highest anti-cancer activity against mouse colon cancer CT 26 cells in vitro and was further evaluated in a CT 26 allograft mouse model in vivo. GM07 was identified as Odoribacter splanchnicus through phylogenetic analysis based on 16S rRNA gene sequencing. Further investigation determined that the CFS of O. splanchnicus (OsCFS) induced anti-proliferative activity via apoptosis, but not cell cycle arrest. Moreover, GC/MS analysis suggested that the putative active molecule in OsCFS is malic acid. Finally, in the CRC mouse model, peri-tumoral injection of OsCFS significantly decreased CRC formation, compared to the control group. Altogether, these findings will provide valuable information for the discovery of potential probiotic candidates that inhibit CRC.

Gut Microbiota Eubacterium callanderi Exerts Anti-Colorectal Cancer Activity

“…6 ). Interestingly, unlike our previous study that revealed only the CFS of O. splanchnicus , not live bacteria, exhibits anti-CRC activity in vivo ( 14 ), oral administration of E. callanderi live bacteria inhibited tumor growth in the mouse model. We speculated that orally administered E. callanderi can safely reach the gastrointestinal tract, leading to successful colonization, allowing it to exert anti-CRC effects by producing the same active molecules suggested in in vitro studies or different molecules in vivo , which has not been investigated in this study.…”

“…In a previous study, we screened the anti-CRC activity of gut microbes isolated from healthy Korean feces using their cell-free supernatants (CFSs) and discovered several CFSs with antiproliferative activity against colonic carcinoma cell lines ( 14 ). To identify one of the candidate microbes, we performed 16S rRNA gene sequencing and phylogenetic and phenotypic analyses, and discovered that it is E. callanderi (99.52% 16S rRNA gene similarity, rod-shaped without flagella).…”

“…Another study revealed that Lactobacillus delbrueckii CU/22 producing hydrogen peroxide could induce apoptosis and necrosis in human CRC cells ( 30 ). Moreover, our recent study demonstrated that O. splanchnicus exerts anti-CRC activity by inducing apoptosis ( 14 ). However, numerous anti-CRC candidates still need to be confirmed or identified.…”

“…and Akkermansia muciniphila ( 11 to 13 ). In addition, we recently demonstrated that Odoribacter splanchnicus exhibits anti-CRC activity ( 14 ). However, the metagenomic analysis of patients with CRC can have the same limitations mentioned above; thus, culture-based identification is needed to identify gut microbes for CRC treatment.…”

Alterations in co-abundant bacteriome in colorectal cancer and its persistence after surgery: a pilot study

“…including B. caccae and B. vulgatus are known to be involved in destabilizing the colonic wall of the gut, potentially resulting in the progression of CRC 46 , 47 . At the same time, Odoribacter levels is shown to correlate with somatic mutations and cell proliferation resulting in poorer CRC prognosis 50 , 51 . Interestingly, differences in Bacteroidetes ASVs and Odoribacter splanchnicus were no longer observed after surgery when compared to NC individuals (Fig.…”