A bug in the gut that shoots up risk of colon cancer
doi:10.1038/nindia.2020.17 Published online 3 February 2020
Indian researchers have identified a new gut-inhabiting bacterium that increases the risk of colon cancer1. This bacterium can break down chemicals with anticancer properties called flavonoids, which humans get from edible plants and fruits.
The researchers have found that colon cancer patients have a higher number of this bacterium than healthy individuals. They say this bacterium may act as a biomarker for detecting the early onset of colon cancer without using invasive procedures.
“The findings of this research could be taken a step further,” says lead researcher Vineet Sharma from the Indian Institute of Science Education and Research in Bhopal, India. “In fact, we can prepare probiotics, dietary supplements made of live bacteria that, when consumed, may restore the cancer-afflicted gut to a healthy state.”
Compared with developed and developing countries, India has a low incidence of colon cancer. Such a low incidence is often linked to a high consumption of vegetables, spices and other food with anticancer properties. However, no studies have yet explored the relationship between colon cancer and gut bacteria.
To find out, the researchers isolated gut bacteria from the faecal samples of colon cancer patients as well as healthy people from Bhopal, a central Indian city, and Kerala state, which reports the highest incidence of colorectal cancer in India. Using the latest gene-sequencing techniques and computational models, they then sequenced the genomes of these bacteria.
Remarkably, they found a few gut bacteria that have not yet been associated with colorectal cancer in India. “A novel and striking finding was the presence of flavonoid-degrading Flavinofractor plautii, significantly associated with colon cancer,” says Sharma.
Sharma and his colleagues also linked other gut bacteria, such as Bacteroides intestinalis, Methanobrevibacter smithii, Streptococcus parasanguinis, and Veillonella parvula, with increased risks of colon cancer.
They identified 33 microbial genes that were highly expressed in the cancer patients. These genes, Sharma says, were highly correlated with F. plautii and Bacteroides fragilis. The results further validate that these bacteria could play a role in increasing the risks of colon cancer among Indians, he adds.
The identification of this novel bacterium may turn out as a potential diagnostic or therapeutic marker, says Palok Aich from the National Institute of Science Education and Research in Bhubaneswar, India. The study highlights only one bacterial species as a biomarker. "My guess is that the human gut harbours many other microbes with potential therapeutic or diagnostic roles," Aich says.
1. Gupta, A. et al. Association of Flavonifractor plautii, a flavonoid-degrading bacterium, with the gut microbiome of colorectal cancer patients in India. mSystems.4, e00438-19 (2019)