Researchers have found that a specific subtype of a microbe commonly found in the mouth is able to travel to the gut and grow within colorectal cancer tumours. This microbe is also a culprit for driving cancer progression and leads to poorer patient outcomes after cancer treatment. The findings could help improve therapeutic approaches and early screening methods for colorectal cancer, which is the second most common cause of cancer deaths in adults in the U.S. Examining colorectal cancer tumours removed from 200 patients, researchers measured levels of Fusobacterium nucleatum, a bacterium known to infect tumours. In about 50% of the cases, they found that only a specific subtype of the bacterium was elevated in the tumour tissue compared to healthy tissue. They also found this microbe in higher numbers within stool samples of colorectal cancer patients compared with stool samples from healthy people. Patients with colorectal tumours containing this bacterium have poor survival and poorer prognosis compared with patients without the microbe. The predominant group of Fusobacterium nucleatum in colorectal cancer tumours, thought to be a single subspecies, is actually composed of two distinct lineages known as clades.

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