E. coli - Friend or Foe?
E. coli implicated in colon cancer...
Colorectal cancer (CRC) is the third most common cause of cancer-related death in the United States, with approximately 50,000 deaths reported in 2020. (1) Most cases and deaths may be attributable to risk factors such as age, family history, adenomas, inflammatory bowel disease, or racial and ethnic backgrounds. (2)
Other lifestyle-related factors associated to colorectal cancer are weight, smoking, alcohol consumption or diet type. In recent years, increasing importance in the progression of CRC has been linked to the gut microbiome.
Twenty percent of the global cancer burden may be attributed to bacterial pathogens. (3) In colorectal cancer specifically, bacteria associated with carcinogensis, include Helicobacter pylori, enterotoxigenic Bacteroides fragilis, and various pathogenic strains of Escherichia coli. (4) Despite E. coli being a commensal bacteria in the human microbiota, various studies have demonstrated a relationship between mucosa-adherent E. coli and colorectal cancer.
Additionally, several strains of E. coli phylogenic group B2 have been associated with Crohn’s disease, a known risk factor for colorectal cancer. (5) Moreover, mucosa associated or internalized E. coli were observed more often in patients with colorectal cancer than in controls. (6)
E. coli has been known to damage the DNA of gut epithelial cells
During the development of cancer, the gut microbiome, immune system, and tumor microbiome may produce an imbalance in bacterial composition (dysbiosis).
The tumor microbiome has a negative impact on the gut microbiome causing poor local and systemic responses from host immune system and limited efficacy of chemo- and immunotherapy. When left unchecked in the gut microbiome, pathogenic E. coli can damage the DNA of epithelial cells, i.e., inducing DNA double-strand breaks and/or chromosomal instability (7).
The complex immunological cascade that follows could promote the development of an aggressive form of carcinoma.
Predictive and prognostic biomarkers, such as the presence of pathogenic E. coli in stool and the composition of gut microbiomes can be of great use in screening colorectal cancers. There are many interventional approaches to modulating the gut microbiome including pro- and prebiotics, dietary modifications and regular physical activity.
It is important to emphasize that by promoting one’s healthy gut microbiome, the overall health of the individual is improved.(8)
Until patient-tailored personalized medicine is created, the most effective way to reduce the risk of colorectal cancer is routine screening, beginning at age 45. (9)
By Yesenia Morales - Technical Services Microbiologist at Hardy Diagnostics
