QUORUM QUENCHING DECREASES METASTATIC RATE WITHOUT AFFECTING GUT MICROBIOME COMPOSITION IN A COLORECTAL CANCER MODEL

Gut microbiome plays a key role in human health, and the gut microbiome composition has been linked with many diseases, including colorectal cancer (CRC). The microbiome has been found to be associated with CRC progression, as well as patient outcomes. We hypothesized that disrupting communication within the gut microbiome and between the gut microbiome and host cells via quorum quenching (QQ) enzymes may affect CRC metastasis. These enzymes degrade quorum sensing (QS) chemicals used by bacteria to communicate and regulate gene expression, including expression of virulence factors. We administered two QQ enzymes: GcL, an enzyme with a broad substrate specificity allowing it to target a larger number of QS chemicals, and SsoPox, which is active on longer-chain QS chemicals. After being implanted with a CRC tumor organoid, male mice were separated into one of two treatment groups (GcL or SsoPox) or a water control (DW) and given water with their assigned QQ enzyme at 1mg/mL (n = 10). Mice were housed individually for a period of eight weeks or until moribund, at which point a necropsy was performed, during which blood and tissue were collected. Fecal samples were collected weekly throughout the experiment. At the time of necropsy, 3 of 10 (30.0%) DW control mice had visible metastases, while only 1 of 19 (5.3%) treatment mice, a GcL mouse, metastasized (McNemar’s test, p = 0.002). No metastases were observed among mice receiving SsoPox (n = 9). When GcL and SsoPox were analyzed individually, differences in metastatic rate approached significance by Cochrane-Armitage trend test (p = 0.057). The gut microbiome composition was determined by amplicon sequencing of fecal pellets. At the endpoint, the gut microbiome compositions of both treatment groups were not statistically significant from one another or the DW control (ANOSIM p=0.481). Additionally, both Chao1 (247.4±96.0) and Shannon (3.28±0.26) indices of diversity were not significant at the endpoint (ANOVA p=0.694, 0.803, respectively). The in vivo effects of QQ enzymes are poorly understood, but these results indicate that QQ treatments may have clinically relevant effects without altering the gut microbiome composition of the host. This is a promising first step in our investigation of QQ treatments for CRC, demonstrating that the behavior of the gut microbiota may be as important as the gut microbiome composition itself.