Study May Link Bacteria to Cancer

High levels of Fusobacterium cells have been discovered in the tumor tissues of several colorectal cancer patients, raising the possibility that these bacteria may be linked to the cancer, according to a recently released study headed by Harvard Medical School Graduate Student Aleksandar D. Kostic.

Scientists say they will need to conduct more research to determine the exact relationship between the bacterium and colon cancer, but the findings should make diagnosing patients easier and could have implications for the treatment of colon cancer.

The study, titled “Genomic Analysis Identifies Association of Fusobacterium with Colorectal Carcinoma,” located extraneous organisms in normal and infected tissues by examining their microbial make-up through a process called Pathogen Sequencing.

Taking initial samples from nine colorectal cancer patients, a team of 18 researchers was able to compare DNA sequences to determine which microorganisms were present in the cancerous tissue but not in the healthy tissue. A close analysis of the samples revealed that one genus of bacteria seemed to be present in the infected tissues.

“From the individual samples, we identified more than 300 distinct organisms,” said Kostic. “But there was one very striking exception, and that was the abundance of Fusobacteria in the tumor tissues.”

With this observation, researchers then proceeded to validate their findings with a broader participant pool of 95 patients. Again, the presence of Fusobacteria was found to be common across the samples that were collected.

Tremendous improvement in DNA sequencing technology throughout the past decade helped make the discovery possible, researchers said.

“We had been conducting research on colon cancer since 2001,” said Harvard Medical School Pathology Professor  Matthew L. Meyerson ’85, a researcher on the study. “DNA sequencing technology has helped us make leaps and bounds in attempting to determine the cause of colon cancer.”

Researchers point out, however, that this link between Fusobacteria and colon cancer does not necessarily determine causality.

“What this work shows is simply an association,” said Kostic. “What we’re still trying to establish is whether Fusobacteria is a cause or consequence of colon cancer.”

Kostic and his team have already begun further research on the topic, and are currently conducting experiments on mice.

Although conclusive findings could be a decade away, if the animals are found to develop colon cancer upon exposure to Fusobacteria, it could establish a causal relationship between the bacterium and colon cancer.

The results could play a major role in developing potential treatments for colon cancer.

“We don’t know yet whether there is a causal relationship between this bacteria and colon cancer,” said Kostic. “But if there is, then it might be possible to give patients Fusobacteria-targeting antibiotics to treat colon cancer.”