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Are Certain Bacteria Associated With Development of Colorectal Cancer?

By: Kayci Reyer
Posted: Tuesday, October 2, 2018

The gut microbiome may play an important role in the development of colorectal cancer, according to a study published in the Journal of Gastrointestinal Oncology. Study author Jessica D. Dahmus, MD, of the Thomas Jefferson University Hospital, and colleagues sought to analyze the potential carcinogenic associations of five strains of sulfidogenic bacteria based on prior published research.

Sulfidogenic bacteria was focused on due to its production of hydrogen sulfide, which has been shown to cause DNA damage. This can result in genomic instability, notably found in more than 80% of sporadic colorectal cancers. The authors suggested that hydrogen sulfide affects mitochondrial function in intestinal epithelial cells, resulting in hyperproliferation in the Ras/MAPK pathway. Colorectal cancer is one of many malignancies for which this pathway is a known mechanism of carcinogenesis.

Researchers analyzed Streptococcus bovis, Fusobacterium nucleatum, Helicobacter pylori, Bacteroides fragilis, and Clostridium septicum. S. bovis seems to be associated with higher rates of both adenomas and carcinomas. Patients with colorectal cancer have been shown to have high concentrations of F. nucleatum and less microbial diversity than control groups. H. pylori infections appear to be associated with a 1.4-fold risk increase for colorectal cancer, although the authors mentioned that data may be controversial due to publication bias from the original research. The subtype Enterotoxigenic Bacteroides fragilis produces a toxin that has been shown to affect the development of colorectal cancer. Finally, C. septicum has not been associated with the initial appearance of colorectal cancer, but it does appear to have a mutually beneficial relationship with malignancies in progress.

“Future research may focus on whether the detection of certain bacterial concentrations within stool or biopsied polyps could serve as adjuncts to current screening modalities to help identify higher risk patients,” the authors concluded.



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