Chemotherapy needs gut bacteria to work

Antibiotics may prevent anticancer drugs from killing tumors

GOOD GUT MICROBES  Antibiotics that kill bacteria such as Enterococcus hirae (shown in a scanning electron microscope image) also reduce the effectiveness of chemotherapy drugs. The findings from two independent studies indicate that gut microbes are needed to fight cancer.

Courtesy of Chantal Ecobichon and Christine Schmitt/Pasteur Institute 

Cancer patients may carry powerful weapons against tumors in their intestines. Two independent studies indicate that intestinal bacteria assist chemotherapy drugs in fighting off tumors.

Gut microbes are necessary for several types of anticancer therapies to work properly, the studies published in the Nov. 22 Science suggest. In experiments using mice, antibiotics hampered the ability of two types of anticancer treatments to combat lymphoma and skin and colon tumors, Noriho Iida of the U.S. National Cancer Institute in Frederick, Md., and colleagues report. In mice treated with antibiotics, immune therapy and a platinum-containing chemotherapy drug called oxaliplatin failed to fight off cancer, the researchers found.

A separate study from Sophie Viaud of the French Institute of Health and Medical Research in Villejuif shows that a chemotherapy drug called cyclophosphamide causes bacteria in the gut to move into the lymph system. Once there, the bacteria trigger production of immune cells that then kill tumor cells. Mice raised without any bacteria and mice treated with antibiotics couldn’t produce as many of these immune cells, and the chemotherapy drug became less effective. 

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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