Oral Bacteria and Intestinal Dysbiosis in Colorectal Cancer

Abstract

The human organism coexists with its microbiota in a symbiotic relationship. These polymicrobial communities are involved in many crucial functions, such as immunity, protection against pathogens, and metabolism of dietary compounds, thus maintaining homeostasis. The oral cavity and the colon, although distant anatomic regions, are both highly colonized by distinct microbiotas. However, studies indicate that oral bacteria are able to disseminate into the colon. This is mostly evident in conditions such as periodontitis, where specific bacteria, namely Fusobacterium nucrelatum and Porphyromonas gingivalis project a pathogenic profile. In the colon these bacteria can alter the composition of the residual microbiota, in the context of complex biofilms, resulting in intestinal dysbiosis. This orally-driven disruption promotes aberrant immune and inflammatory responses, eventually leading to colorectal cancer (CRC) tumorigenesis. Understanding the exact mechanisms of these interactions will yield future opportunities regarding prevention and treatment of CRC.

Interplay between Dietary Polyphenols and Oral and Gut Microbiota in the Development of Colorectal Cancer

“…(F. nucleatum, F. mortiferum, and F. necrophorum) in CRC tissues, while bacteria belonging to Firmicutes and Bacteroidetes phyla were decreased [41]. This reduction in intestinal microbial diversity, as well as the overabundance of Fusobacterium, has been reported as common microbiota characteristics of CRC patients [37]. Interestingly, longer overall survival time was observed in CRC patients with low levels of F. nucleatum than in subjects with either moderate or high levels of this species.…”

“…Interestingly, longer overall survival time was observed in CRC patients with low levels of F. nucleatum than in subjects with either moderate or high levels of this species. Going one step further, other studies have shown a connection between the detection of F. nucleatum and a poorer prognosis in CRC cases [42], suggesting the involvement of this bacteria as a non-invasive biomarker for CRC screening [37]. On the other hand, it is remarkable the high similarity found between F. nucleatum strains in tumor tissue and saliva from patients with CRC, which highlights an oral origin and strengthens the hypothesis about an orally driven intestinal dysbiosis in CRC [43,44].…”

“…In addition, Treponema denticola and Prevotella intermedia seem to be associated with increased CRC risk. In this sense, a complete description of the oral bacteria related with the development of CRC has been recently reported by Koliarakis et al (2019) [37]. Although many oral bacteria have been suggested for their involvement in one or most types of CRC, two well-known pro-inflammatory, invasive, anaerobic, oral pathogens, with evident associations with dental plaques and periodontitis as later colonizers, Fusobacterium nucleatum and Porphyromonas spp.…”

Effect of Periodontopathic Bacteria <i>Fusobacterium Nucleatum</i> on Intestinal Im mune Cells

“…The oral cavity and colon are separate anatomical regions, but both are highly established by distinct microbiota. However, oral bacteria can spread to the colon (5) . This is mostly evident in the destruction of oral microbi-omes, such as periodontitis, where certain bacteria such as Fusobacterium nucleatum and Porphyromonas gingivalis have a pathogenic profile (6) .…”

HARMONIES: A Hybrid Approach for Microbiome Networks Inference via Exploiting Sparsity

“…In fact, previous CRC studies showed enrichment of these three genera or their species in CRC patients (see e.g. Geng et al, 2014;Ugai et al, 2014;Kumar et al, 2017;Koliarakis et al, 2019), but had not detected these novel interactions. In conclusion, HARMONIES may reveal how multiple CRC-related taxa could potentially promote disease progression together.…”