Brushing your teeth regularly could help to prevent bowel cancer, a study suggests. This is because the mouth bacteria that cause bleeding gums can travel via the blood to the bowel where they could trigger cancer or worsen existing tumours. The bug fusobacterium has been found to be hundreds of times more common in cancerous tumours than in normal cells. Now researchers have found that the microbes can make pre-cancerous growths in the bowel turn cancerous. They can also make any existing tumours in the bowel grow larger. Scientists are investigating how the bacteria make their way to the gut through the bloodstream. One theory is that it may happen if a person has bleeding gums. The researchers found that the bacteria have a protein that allows them to stick to sugar molecules attached to benign growths called polyps as well as cancer tumours in the bowel. The bacteria are anaerobic – they do not breathe oxygen – so are well suited to live in the bowel. After sticking to the polyps or tumours, the presence of the bacteria promotes their growth, according to the research published in Cell Growth and Microbe. By targeting this process, the researchers believe that it may lead to new drugs to treat bowel cancer which around one in 20 of us will develop in our lifetimes. Co-author Wendy Garrett, a professor at Harvard University’s TH Chan School of Public Health, said a greater understanding of the mechanism may help stop people developing cancerous tumours. She added: ‘Alternatively, and perhaps more importantly, our findings suggest that drugs targeting the same or similar mechanisms of bacterial sugar-binding proteins could potentially prevent these bacteria from exacerbating colorectal cancer.’ Fusobacterium worsens gum disease in the mouth because it acts as an ‘anchor’ around teeth and gums for other bacteria, helping to cause a biofilm – a ‘mat’ of different bacteria that eat away at the gums, causing inflammation, and loosening the teeth. As well as worsening cancer, the bugs have also been found to worsen the bowel condition ulcerative colitis, which in turn is also linked to cancer. Fusobacterium is only very rarely found in the guts of healthy patients. The researchers suspected that oral microbes might reach colorectal tumors through the bloodstream. To test this idea, they injected fusobacteria into the tail veins of two mouse models with either precancerous or malignant colorectal tumors. In both types of mice, the fusobacteria accumulated in colorectal tumors compared to adjacent normal tissue. The researchers also detected fusobacteria in the majority of human colorectal cancer metastases tested, but not in most samples taken from tumor-free liver biopsies. Taken together, the findings suggest that fusobacteria travel through the bloodstream to reach colorectal tumors, and then use their Fap2 protein to bind to host cells and proliferate in tumors, thereby accelerating colorectal cancer. Co-author Gilad Bachrach of the Hebrew University-Hadassah School of Dental Medicine said: ‘The strengths are that the study involved both human samples and mouse models. The weakness is that the available mouse models for colorectal adenocarcinoma do not completely reflect the slowly developing disease in humans.’ Increasingly bacteria in the mouth have been linked to diseases in other locations around the body. Mouth bacteria that enter the bloodstream via bleeding gums have been linked to heart disease and stroke. More recently, it has been proposed that oral bacteria may cause Alzheimer’s disease – triggering inflammation in the brain that in turn results in the growth of plaques and tangles of protein that characterise the condition. A 2012 study found that high levels of dental plaque – composed partly of bacteria – was associated with people dying up to 13 years earlier than expected. The people with the most plaque on the surface of their teeth and gums had an 80 percent increased risk of premature death. The researchers at Sweden’s Karolinska Institute however warned that poor mouth hygiene may be an indicator of other lifestyle factors linked to cancer.