Research suggests mouth bacteria promote bowel cancer
Two US studies have shown how bacteria that are sometimes found in the mouth and gut can fuel the development of bowel cancer.
The research could lead to more effective strategies for the early diagnosis, prevention and treatment of the disease.
The studies show how gut bacteria called fusobacteria can stimulate immune responses and turn on cancer growth genes.
Other research had shown that fusobacteria from the mouth are also abundant in tissues from bowel cancer patients. But until now, it was not known whether these microbes directly contribute to the formation of tumours or not.
The latest studies, both published in the journal Cell Host and Microbe, were conducted at the Harvard School of Public Health in Boston, and Case Western Reserve University School of Dental Medicine in Cleveland.
They cast new light on the key role played by fusobacteria in bowel cancer.
"Fusobacteria may provide not only a new way to group or describe colon cancers but also, more importantly, a new perspective on how to target pathways to halt tumour growth and spread," according to senior study author Wendy Garrett of the Harvard School of Public Health and the Dana-Farber Cancer Institute.
Oliver Childs, Senior Science Information Officer at Cancer Research UK, said: "Our bodies contain many hundreds of microbes, many of which are beneficial and protect us against disease.
"But some can cause harm and this latest research gives compelling evidence that fusobacteria contribute to the development of certain bowel cancers by helping the cancer cells to grow.
"If larger studies confirm this work, a potential next step will be to develop tests to spot people at higher risk of bowel cancer or drugs that eradicate the effects of the bacteria."
In the first study, Dr Garrett and collaborators found that fusobacteria are found in human adenomas - benign bowel tumours that can become malignant over time.
They also showed that,in mice, the bacteria accelerated the formation of tumours by attracting immune cells called myeloid cells, which invade tumours and stimulate inflammatory responses that can cause cancer.
In the second study, Dr Yiping Han of Case Western Reserve University School of Dental Medicine and her collaborators discovered that fusobacteria rely on a molecule called Fusobacterium adhesin A (FadA), which is found on the surface of these bacterial cells, to attach to and invade bowel cancer cells.
FadA then turns on cancer growth genes and stimulates inflammatory responses in these cells and promotes tumour formation.
Dr Han and her team also found that FadA levels were much higher in tissues from patients with adenomas and bowel cancer compared with healthy individuals.
Furthermore, they identified a compound that can prevent FadA's effects on cancer cells.
She said: "We showed that FadA is a marker that can be used for the early diagnosis of colorectal cancer and identified potential therapeutic targets to treat or prevent this common and debilitating disease."
Copyright Press Association 2013