Study of Microbiota Associated to Early Tumors Can Shed Light on Colon Carcinogenesis

Abstract

An increasingly important role for gut microbiota in the initiation and progression of colorectal cancer (CRC) has been described. Even in the early stages of transformation, i.e., colorectal adenomas, changes in gut microbiota composition have been observed, and several bacterial species, such as pks⁺Escherichia coli and enterotoxigenic Bacteroides fragilis, have been proposed to drive colon tumorigenesis. In recent years, several strategies have been developed to study mucosa-associated microbiota (MAM), which is more closely associated with CRC development than lumen-associated microbiota (LAM) derived from fecal samples. This review summarizes the state of the art about the oncogenic actions of gut bacteria and compares the different sampling strategies to collect intestinal microbiota (feces, biopsies, swabs, brushes, and washing aspirates). In particular, this article recapitulates the current knowledge on MAM in colorectal adenomas and serrated polyps, since studying the intestinal microbiota associated with early-stage tumors can elucidate the molecular mechanisms underpinning CRC carcinogenesis.

Keywords: colon polyp; colorectal cancer; gut microbiota; intestinal pathogens; lumen-associated microbiota; mucosa-associated microbiota.

Figure 1

The diverse mechanisms used by pathobionts to induce damage. The information included in this figure refers to citations [28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,53,54,55,56,57,64,65,66,67] and was created with BioRender.com app.biorender.com (accessed on 15 October 2024).

Figure 2

The most commonly employed methods to collect samples for gut microbiota studies. The information included in this figure refers to citations [73,74,75,76,81,82,83,84,85,86] and was created with app.biorender.com (accessed on 15 October 2024).