Two cancer studies have found a type of bacteria that cause dental decay and skin ulcers to possibly be linked to bowel cancer.
The two research teams have discovered the pathogen 'Fusobacterium' in bowel cancer tumors.
They say it's not yet clear if the bug might cause cancerous changes or whether it is just an incidental finding, TIME reports.
If the bacterium is found to be responsible, the teams say antibiotics might be able to treat it and prevent cancer.
The two studies looked at more than 100 samples of healthy and cancerous bowel tissue and found the presence of the bug.
They discovered the link by analyzing genetic material in tumor samples. They then subtracted human genes from the mix, until only microbe genes remained.
Dr. Robert A. Holt, a genomics researcher at the British Columbia Cancer Agency, had long wondered whether colon cancer was caused, or driven further along, by a bacterial infection.
Remembering that cancers of the liver, stomach and cervix have all been linked to microbes, Holt realized the number of microbial cells in the colon outnumber human cells there by a ratio of at least nine to one.
Holt and another group of researchers, working independently, discovered that one species of bacterium never particularly prevalent in the colon seems to be present in colon cancers.
The two research groups discovered the link by analyzing genetic material in tumor samples. They then subtracted human genes from the mix. What remained were microbe genes.
An analysis of these microbial genes showed that a type of bacterium, Fusobacterium, was abundant in the tumors although it normally is not among the more prominent species in the gut.
Dr. Holt found in subsequent experiments that the bacteria were burrowing into tumor cells - "which is kind of creepy," he said, reports the Press Association.
An ability to invade cells, he said, is often what distinguishes a disease-causing microbe from one that is harmless.
As Holt and his colleagues investigated further, they found the bacteria were especially prevalent in patients whose cancer had spread beyond their colons.
Dr. Matthew Meyerson and his colleagues at the Dana-Farber Cancer Institute in Boston found the same thing.
"That, to me, was a real eye-opener," Dr. Meyerson said. Having expected to find lots of different bacteria in the tumor tissue, he said. "It turned out not to be that way,” the Press Association reports.
"I don't know what to make of it," Dr. Meyerson said. "The bacteria are hanging around the tumors, but I have no idea if they spur or cause cancer."
The two studies are published online Tuesday in the journal Genome Research: http://genome.cshlp.org/content/early/2011/10/05/gr.126516.111.abstract
