Published Thursday, scientists at the National Cancer Institute wrote an article called “NIH Mouse Study Finds Gut Microorganisms May Determine Cancer Treatment Outcomes”.  The National Cancer Institute believes they may have found a connection between the presence of certain organisms living in the human gut and the success of cancer therapy.  Mice that had cancerous tumors were studied and the mice that did not have these microorganisms had an impaired ability to fight cancer growth and live longer.  These microorgansisms that live within the gut are called “commensal microbiota” and do not negatively affect their host.  Chemotherapy drugs such as oxaliplatin and cisplatin also had a diminished effect for the mice that lack commensal microbiota.

Some reports suggest that chemotherapy drugs harm the intestinal microbiota and affect the anti-tumor immune response intended by the drugs.  The bacterial composition in the gut does not return to normal after being treated with antibiotics and may permanently inhibit the effectiveness of anti-cancer therapy and people who have frequently used antibiotics throughout their life may be included for this decreased effectiveness of cancer drugs.  Researchers are now trying to determine how these microorganisms send messages to different parts of the body and increase levels of inflammation to infected parts; it is thought that this signal to change the type and level of inflammation in the infected body organ is related to the successful outcomes with cancer therapies.

The mice used for this study were raised in sterile environments so they did not acquire any bacteria and were given strong antibiotics to ensure they did not harbor any of the commensal microbiota.  Once the necessary precautions were taken to sterilize the mice, they were injected with cancer cells that would form tumors in the mice.  This study showed that the germ free mice did not respond well to the drugs meant to target their tumors.