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Microbial DNA in blood may help diagnose cancer

16 March 2020
Appeared in BioNews 1039

Different types and stages of cancer may cause unique microbial DNA signatures that can be detected in the blood, according to new research published in Nature.

The preliminary study, led by a team in the Centre for Microbiome Innovation at the University of California, San Diego, mined the Cancer Genome Atlas to determine whether specific patterns of microbial DNA are present in cancer.

They examined more than 18,000 tumour samples from 33 different types of cancer and found it was not only possible to differentiate between cancer types based upon the microbe DNA signature, but that this signatory code was also present in early stage cancers, suggesting microbe changes happen early in the disease.

Professor Rob Knight, director of the Centre for Microbiome Innovation said: 'Almost all previous cancer research efforts have assumed tumours are sterile environments, and ignored the complex interplay human cancer cells may have with the bacteria, viruses and other microbes that live in and on our bodies. The number of microbial genes in our bodies vastly outnumbers the number of human genes, so it shouldn't be surprising that they give us important clues to our health.'

To assess whether their microbe findings applied to real-life samples, the team took plasma from patients with high-grade prostate, lung and skin cancer, and people who did not have cancer. All were tested for the signatory DNA codes.

Results showed the microbe DNA signature was only present in cancer samples, there were no false positives. Furthermore, specific microbe signatures could be used to differentiate between cancer types – achieving an 81 percent accuracy between prostate and lung cancer samples.

This new research demonstrates a specific change in a person's microbe occurs when they have cancer. Whether that change drives cancer development, or is a result of the cancer is not yet known. However, Dr Sandip Patel, a co-author of the study said: 'The ability, in a single tube of blood, to have a comprehensive profile of the tumour's DNA (nature) as well as the DNA of the patient's microbiota (nurture), so to speak, is an important step forward in better understanding host-environment interactions in cancer.'

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