A Link Between Fusobacterium species and Colon Cancer

The possibility that are associated of Fusobacterium species with colonic cancer was suggested in two studies published in Genome Research. The organism was detected in colon cancer cells by both Meyerson et al from the Dana Farber Cancer Institute and Holt et al from the British Columbia Cancer Agency Genome Sciences Center. The two research groups used genetic probes to identify the bacteria found in the tumor tissues.  

Fusobacterium species are mostly found in the mouth and are linked to periodontal disease and oral infections. It is rarely found among the usual gastrointestinal bacteria, but it appears to the only type of bacteria inside colonic cancer cells.  

Gram staining of Fusobacterium nucleatum 

Meyerson et al looked for bacterial DNA, comparing tumor tissue and healthy colon samples from nine patients with colonic cancer. They found Fusobacteria DNA mostly in the cancer tissue. In further studies these investigators found Fusobacterium species in 95 other colon cancer patients.  

Holt et al. focused on RNA instead of DNA. These investigators studied colon cancer biopsies and normal tissues of 11 patients and found that Fusobacteria were more likely to be in cancer tissue than in normal cells. In some specimens, the number of Fusobacteria was hundreds of time higher in cancer cells than in normal tissues.   The investigators also found that other types of bacteria that commonly reside in the gut are depleted in colon cancer tissues. Whether the Fusobacteria are crowding out these more common bugs, or whether they tend to die off in the presence of malignant cells isn't known.  

Currently it is unclear whether or how Fusobacteria might be contributing to the development of cancer. These organisms may promote inflammation, which can contribute to malignant transformation in normal cells. Alternatively, the tumor environment may be more hospitable to Fusobacterial growth, and the high number of this bacterium would be a consequence, not the cause, of the cancer.

Colonic cancer