Two new studies, one of them involving SFU researchers, have uncovered the first link between human colorectal cancer and a specific microorganism.

The studies, just published online in the journal Genome Research, found the bacterium Fusobacterium hundreds of times more prevalent in tumors than in normal tissue in 99 colorectal cancer patients. Colon cancer ranks as the second leading cause of cancer deaths.

Rob Holt, associate professor of molecular biology and biochemistry (MBB), and a BC Cancer Agency scientist, is a senior author of one of the reports. He says: “We were surprised by this result. Although Fusobacterium is a known infectious agent, it is rarely in the contents of a normal gut and until now hasn’t been associated with cancer.”

Holt and Matthew Meyerson (senior author of the other study and a pathologist with the Dana-Farber Cancer Institute in Boston) note it has yet to be proven whether Fusobacterium infection causes or precedes colorectal tumors.

“Our future directions are to further investigate the possibility that Fusobacterium could be a direct cause of colon cancer and if so by what mechanism,” says Holt. “We will be also be applying the same methodology to look for correlations between infectious agents in other types of cancer.

“If Fusobacterium is proven to cause colorectal cancer, then targeting it with antibiotics or vaccines may provide a new approach to colon cancer treatment or prevention.”

While Holt and Meyerson are surprised by their independent studies’ results, they observe that several previously known factors support them.

“Gastric cancers have been previously linked to inflammation caused by the microorganism H. pylori. It’s well established now that patients with irritable bowel disease have higher rates of colorectal cancer,” says Holt. “And about 15 per cent of cancers globally are caused by known infectious agents. So it is possible that some of the many species of microbes found in the gut could be associated with colorectal cancers.”

Some other cancers known to be caused by viruses or bacteria are cervical cancer (Human Papilloma virus) and liver cancer (Hepatitis B and C virus).

Richard Moore, adjunct professor in the Faculty of Health Sciences and BC Cancer Agency researcher, and MBB doctoral student Mauro Castellarin, worked with Holt on this study.