Introduction: Toll-like receptor (TLR) signaling has been implicated in the colon inflammatory responses. Such inflammatory signals mediate complex interactions between commensal bacteria and TLRs and are required for immune response and homeostasis. Herein we have aimed to demonstrate immunomodulatory role of gut microbiota by regulation of intestinal TLRs expression.

Methods: Fecal and colonic tissue samples were collected from normal controls (NC) and colon cancerous (CRC) patients via colonoscopy for CRC screening during 2016 to 2018. Fecal samples were collected to analyze intestinal bacteria including Streptococcus bovis, Enterococcus faecalis, Bacteroides fragilis, enterotoxigenic Bacteroides fragilis (ETBF), Fusobacterium nucleatum, Porphyromonas gingivalis, Porphyromonas spp. and Roseburia spp. by real-time PCR. Gene expression of TLR2, TLR4 and TLR5 was examined in colonic tissues by qRT-PCR.

Results: Different abundant of gut bacteria were achieved in NC and CRC groups. The genes expression of TLR2, TLR4 and TLR5 were significantly different in CRC cases vs. normal group (P value <0.05). There was a significant relationship between TLR2, TLR4, TLR5 genes expression and Roseburia spp., P.gingivalis and ENTB quantity in normal group. Also significant association between TLR2, TLR4 genes expression level and the quantity of S.bovis, ENTB, Roseburia spp. and E.faecalis in CRC cases were achieved.

Discussion: Intestinal expression of TLR2, TLR4 and TLR5 is dynamic and depends on gut microbiota. Hence, altered immune activation in response to dysbiotic microbiota may promote intestinal inflammation in a subset of patients with CRC. Keywords: Colon cancer; gut microbiota; Toll-like receptor