Association between Probiotics and Modulation of Gut Microbial Community Composition in Colorectal Cancer Animal Models: A Systematic Review (2010-2021)

Abstract

Background: Colorectal cancer (CRC) is one of the most prevalent gastrointestinal malignancies and is considered the third major cause of mortality globally. Probiotics have been shown to protect against the CRC cascade in numerous studies.

Aims: The goal of this systematic review was to gather the preclinical studies that examined the impact of probiotics on the alteration of gut microbiota profiles (bacterial communities) and their link to colorectal carcinogenesis as well as the potential processes involved.

Methods: The search was performed using Scopus, Web of Science, and PubMed databases. Five parameters were used to develop search filters: "probiotics," "prebiotics," "synbiotics," "colorectal cancer," and "animal model."

Results: Of the 399 full texts that were screened, 33 original articles met the inclusion criteria. According to the current findings, probiotics/synbiotics could significantly attenuate aberrant crypt foci (ACF) formation, restore beneficial bacteria in the microbiota population, increase short-chain fatty acids (SCFAs), and change inflammatory marker expression.

Conclusions: The present systematic review results indicate that probiotics could modulate the gut microbial composition and immune regulation to combat/inhibit CRC in preclinical models. However, where the evidence is more limited, it is critical to transfer preclinical research into clinical data.

Figure 1

Search and inclusion process of PRISMA flow chart of studies to include in this systematic review.

Figure 2

Risk of bias graph displaying each risk of bias item presented as percentages across all 33 studies. The 10 signaling questions of the SYRCLE's risk of bias assessment tool were used. A “Yes” indicates a low risk of bias, a “No” indicates a high risk of bias, and an “Unclear” indicates that insufficient methodology.

Figure 3

The frequency of probiotic species used to treat CRC animal models in 33 studies.

Figure 4

Heat map analysis of probiotics impact on inflammatory markers expression in CRC models. Inflammatory marker levels were compared between probiotic and/or synbiotic treated cancer groups and cancer groups alone (without treatment) in 20 studies. Bif: Bifidobacterium; Clo: Clostridium; Lac: Lactobacillus; Lac. Bif: Lactobacillus Bifidobacterium; Mix: mix of probiotics; Single: single probiotic.

Figure 5

The summary of probiotic potential mechanisms on CRC. The rates of increase and decrease in the microbiota composition and inflammatory markers sections are based on the majority of the articles, not all of them. This diagram is drawn in the Canva web application and the following link provides you with its editable version: https://www.canva.com/design/DAFmjVgqkP0/l-7GhS3AbVkJFG8baGjFmQ/edit?utm_content=DAFmjVgqkP0&utm_campaign=designshare&utm_medium=link2&utm_source=sharebutton.