Saturday, 18 May 2019

Global microbial signatures for colorectal cancer


Patients with colorectal cancer have the same consistent changes in the gut bacteria across continents, cultures, and diets -- a team of international researchers find in a new study. The hope is the results in the future can be used to develop a new method of diagnosing colorectal cancer. This is based on research from the University of Copenhagen The Faculty of Health and Medical Sciences.

Cancers have long been known to arise due to environmental exposures such as unhealthy diet or smoking. Lately, the microbes living in and on our body have entered the stage as key players. But the role that gut microbes play in the development of colorectal cancer -- the third most common cancer worldwide -- is unclear. To determine their influence, association studies have aimed to map how the microbes colonizing the gut of colorectal cancer patients are different from those that inhabit healthy subjects.

Now, researchers have analysed multiple existing microbiome association studies of colorectal cancer together with newly generated data. Their meta-analyses establish disease-specific microbiome changes, which are globally robust -- consistent across seven countries on three continents -- despite differences in environment, diet and life style.


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The study led by UCPH and EMBL scientists focuses on a process in which certain gut bacteria turn bile acids that are part of our digestive juices into metabolites that can be carcinogenic. A related study from the University of Trento shows how certain classes of bacteria degrade choline, an essential nutrient contained in meat and other foods, and turn it into a potentially dangerous metabolite. This metabolite has previously been shown to increase cardiovascular disease risk, and can now also be linked to colorectal cancer.

One of the challenges of metagenomic studies, which are based on genetic material from microbes in environmental samples such as stool, is to link genetic fragments to the various microbial organisms they belong to. The goal of this so-called taxonomic profiling task is to identify and quantify the bacterial species present in the sample.

The role of gut microbes in colorectal cancer still needs to be established. If the changes in the microbiome play a role in developing the cancer, they could also be a therapeutic target. Therefore, Manimozhiyan Arumugam hopes that there will be more focus on the role of microbiome in diseases and that researchers will recognize the advantages of collecting microbiome samples, for example, in large cohorts.

Journal reference:

Meta-analysis of fecal metagenomes reveals global microbial signatures that are specific for colorectal cancer. Nature Medicine, 2019; DOI: 10.1038/s41591-019-0406-6
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology

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