New study may lead to microbiome-based colon cancer diagnostic

Colorectal carcinoma, or colon cancer, is one of the most common cancers and a leading cause of death among the elderly. The cancer is often caused when adenomas, benign tumors, transform into malignant tumors called adenocarcinomas. The gut microbiome has been long implicated in colorectal cancer however it is not yet clear how the microbiome integrates with other risk factors that may lead to this cancer in patients. A study published in Nature Communications studied various risk factors that may influence this progression into colon cancer. 

The scientists collected stool samples from 156 individuals including healthy individuals as well as those with colorectal adenomas or carcinomas and sequenced the microbial DNA. They identified specific bacteria that were different in patients with adenomas or carcinomas and healthy individuals. For example, Bifidobacterium was deficient in those with benign or malignant tumors as well as other bacteria that are signatures of a healthy microbiome.  This showed that the microbiome was different between patients with the cancer and those without.

The scientists also studied whether they could use the microbiome as a diagnostic tool for identifying patients with carcinomas. Using the data they collected of bacteria in the guts of patients with  and without tumors, they came up with a set of markers that could detect the presence of carcinomas. They also specifically investigated whether this could be done for adenomas, which are harder to screen for than carcinomas but important to identify at an early stage in order to intervene before they mutate into carcinomas. This was also successful, though further investigations would most likely be needed to identify adenomas. 

In addition, the researchers looked at what impact diet had on the microbiome of patients with and without carcinomas and adenomas.  They found that those individuals eating higher levels of red meat had carcinoma enriched bacterial communities in their gut and those eating fruits and vegetables had lower levels of carcinoma enriched bacteria.

Continued research into the role that specific risk factors like smoking, diet, and obesity have on the microbiome will help us better understand how these factors influence the onset of this cancer. In the future, it may be possible to utilize the microbiome as a diagnostic tool for the identification of either colorectal adenomas or carcinomas, or even to help develop new microbiome based therapies for colorectal cancer. 

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