Our bodies harbor countless microbes—and so do our tumors, it turns out. Over the past 5 years, researchers have shown cancer tissue contains entire communities of bacteria and fungi. Now, it appears some of the bacteria may be cancer’s accomplices. In a paper in this week, a team led by Susan Bullman of the Fred Hutchinson Cancer Center reports that in oral and colorectal tumors, bacteria live inside cancer cells and boost their production of proteins known to suppress immune responses. The microbial interlopers may set off a chain reaction that prevents the immune system from killing cancerous cells, and they may also help cancer metastasize to other parts of the body.
The study doesn’t entirely clinch the case for a bacterial role in cancer, but it is very suggestive, says Laurence Zitvogel, a tumor immunologist at the Gustave Roussy Institute. “It shows that bacteria in colorectal and oral tumors can actively disturb the immune equilibrium,” she says.
Confirmation that microbes can cause tumors to grow or spread could open up new ways to make cancer treatment more effective, for instance by killing bacteria with antibiotics. And because each type of cancer appears to come with a unique microbiome, researchers are exploring whether microbes could be used as a diagnostic tool to detect cancer early in a blood sample.
