Colon cancer linked to bacteria: future treatment with antibiotics?

By Deborah Kotz , Globe Staff

A significant percentage of colon cancers could be caused by a bacteria and -- if that’s indeed the case -- some tumors eventually may be prevented or treated with antibiotics, suggests a new research finding from the Broad Institute and Dana-Farber Cancer Institute. Using gene sequencing techniques, the researchers found that areas of the colon where tumors are located were far more likely to contain high levels of Fusobacteria -- associated with appendicitis and inflammatory bowel disease -- than other portions of the colon in the same patients that didn’t contain cancer.

“In general, some of the most common bacteria that live in the colon are harmless kinds like e. coli and enterobacteria,” said study leader Aleksandar Kostic, a doctoral candidate in biomedicine at Harvard Medical School. “But most colon cancer patients had Fusobacterium as the most prevalent type but only in areas where there were tumors.” Certain strains of the bacteria are known to cause dangerous inflammation if their growth is unchecked by other bacteria.

In about 10 percent to 15 percent of the 95 patients who participated in the study, Kostic said, more than half of the bacteria in malignant tissue was Fusobacteria. Future studies, he added, need to include at least 1,000 patients to better ascertain whether the association is real.

This wouldn’t be the first time that specific bacteria and viruses were implicated in cancer: The sexually transmitted human papillomavirus (HPV) inserts itself into the human genome to trigger cervical cancer and the herpes virus has been associated with the soft tissue cancer Kaposi’s sarcoma. The bacteria Helicobacter pylori can create an inflammatory environment in the gut that leads to gastric cancer and stomach lymphoma, as well as benign ulcers.

Kostic and his colleagues are currently conducting a study in mice to see if those fed Fusobacteria develop colon tumors at higher rates than those who aren’t infected. “We’ve had encouraging results, but our data aren’t complete yet,” he said.

If and when researchers can demonstate that Fusobacteria actually trigger colon cancer, colon cancer patients who test positive for Fusobacteria via a stool sample -- such a test now exists -- could be treated with antibiotics to see whether they shrink their tumors, Kostic said. Others without colon cancer who test positive for the bacteria, he added, could be treated prophylactically with antibiotics in an effort to lower their risk.

Deborah Kotz can be reached at dkotz@globe.com. Follow her on Twitter @debkotz2.