Significant differences in bacterial composition were seen in biopsies from patients with colorectal cancer compared with those without, in a study published online in the May/June issue of the open access journal Gut Microbes.
“Primarily, we found that there was a higher abundance of proteobacteria. We found three particular groups—bacteroidetes, proteobacteria, and firmicutes—but we found that there was a higher abundance of proteobacteria in [colorectal cancer] cases than in controls,” lead author Temitope O. Keku, PhD, of the Center for Gastrointestinal Biology and Disease at the University of North Carolina at Chapel Hill, said in a telephone interview.
Dr. Keku and her colleagues evaluated adherent bacteria in normal colonic mucosa of 21 adenoma and 23 non-adenoma patients who were enrolled in a cross sectional study. Terminal restriction fragment length polymorphism, clone sequencing, and fluorescent in-situ hybridization analysis of the 16S rRNA genes were used to characterize adherent bacteria; a total of 335 clones were sequenced and processed for phylogenetic and taxonomic analysis.
Overall, firmicutes (62%), bacteroidetes (26%), and proteobacteria (11%) were the most dominant phyla. Compared with the controls, a significantly higher abundance of proteobacteria (12.9% vs 4.85%) and a lower abundance of bacteroidetes (29.14% vs 37.24%) were observed in those with an adenoma.
“The implication is that we can pinpoint the particular bacteria that are important in terms of colorectal cancer,” Dr. Keku said.
“We can also identify people who are at risk and we can suggest that they include good bacteria in their diet. For example, it would be great to tell people, ‘we know your risk for colorectal cancer and you can lower it by eating yogurt every day.’ That’s ultimately the long-term implication.”
Since conducting the study, Dr. Keku and her team have already begun taking the next steps with the data, hoping to replicate the study in a larger patient population and also in animal models. Improvements in sequencing technology will allow the researchers to look at a larger number of patient samples at one time, she explained.
“I think that we’ve come a long way from the time when we didn’t know risk factors and how they may impact our chance of getting colon cancer, but now we can look at the bacteria. Being able to do this opens up a whole new world and gives us a better understanding of the various factors that are involved with cancer, like diet, environment, genes, and now microbes.”