Microbiota Alterations in Precancerous Colon Lesions: A Systematic Review

Abstract

Gut microbiota plays an important role in human health. It may promote carcinogenesis and is related to several diseases of the gastrointestinal tract. This study of microbial dysbiosis in the etiology of colorectal adenoma aimed to investigate the possible causative role of microbiota in the adenoma–carcinoma sequence and its possible preventive role. A systematic, PRISMA-guided review was performed. The PubMed database was searched using “adenoma microbiota” and selecting original articles between January 2010 and May 2020 independently screened. A higher prevalence of Proteobacteria, Fusobacteria, and Bacteroidetes phyla was observed in the fecal luminal and mucosa-associated microbiota of patients with adenoma. However, other studies provided evidence of depletion of Clostridium, Faecalibacterium, Bacteroides and Romboutsia. Results on the relationship between adenoma endoscopic resection and microbiota were inconsistent. In conclusion, none of the analyzed studies developed a predictive model that could differentiate adenoma from non-adenoma patients, and therefore, to prevent cancer progression. The impact of adenoma’s endoscopic resection on microbiota was investigated, but the results were inconclusive. Further research in the field is required.

Microbiota Dysbiosis a Cause of Colorectal Cancer or Not? A Systematic Review

“…In contrast, Proteobacteria were the most predominant organisms demonstrated in the gut of well persons, with a summing up to a percentage of 60.35, as compared to that seen in colorectal cancer, which was only present in small numbers of 10.66% (95% CI: −35.32 to −15.57%, P: < 0.001) [9]. Another study supports these findings in colorectal adenoma patients and healthy individuals as controls, which also showed a predominant amount of Proteobacteria in colorectal adenoma patients and a lower amount of Bacteroides in both colorectal adenoma patients and healthy individuals [8].…”

“…The fecal sample derived from colorectal adenoma patients revealed differences in their constituents when matched with those of healthy individuals. Clostridium, Roseburia, and Eubacterium species, in addition to the genera that metabolize butyrate, were noted to be depleted; surprisingly, Enterococcus, Streptococcus species, and Proteobacteria phylum were abundant when juxtaposed with the healthy patient's group [8].…”

“…A progressive increase in the genetic variation was highlighted, with a progressive increase starting from the controls to reaching the top in the carcinoma patients. Thus, in patients with advanced colorectal adenoma or carcinoma, many genes or genera likely indicate an overgrowth of harmful bacteria or archaea [8].…”

“…Consequently, the theorem which implicates microbes as crucial role players in the pathogenesis of CRC has been increasingly noticed; these agents cause modifications in the porosity of the gut mucosal lining, bacterial translocation, and trigger the immune system resulting in long-standing inflammation that could lead to CRC development [8]. CRC is usually diagnosed following the presence of occult blood in stool, which is generally followed by colonoscopy and biopsy for histology [2].…”

Microbiota: An Emerging Biomarker in Colorectal Cancer

“…Hence, the analysis of intestinal microbiota composition in precancerous colonic lesions could have a predictive value in CRC, differentiating adenoma from non-adenoma patients, and therefore, preventing cancer progression. Nevertheless, the results of such correlations are still inconsistent and inconclusive in current literature and further research is required to elucidate the importance of such microbiota alterations [ 5 ]. Genetic susceptibility to CRC is also linked to microbiota dysbiosis.…”