The Microbiome and Cancer: A New Approach to Cancer Immunotherapy

Researchers have connected microbiome composition to a whole host of diseases and cancer seems to be next in line to receive attention from the microbiology community. Researchers have shown that the efficacy of certain anti-cancer drugs may be impacted by the microbial composition of the patient.

We will cover the topic in the following sections:

First off, let’s explore what the connection is between the microbiome and cancer.

The microbiome/cancer connection

There are several ways the microbiome may be related to cancer. Some cancers are linked to inflammation which clearly has links to the microbiome and some cancers even have infectious roots. But the current excitement brewing around the microbiomes connection to cancer is through its interactions with certain cancer therapies.

It seems that the effectiveness of certain anti-cancer treatments is largely dependent on the composition of the gut microbiome. Preliminary results of studies done on humans and mice found that the gut microbiome can impact the efficacy of those drugs and now the search is on to decipher how that can be harnessed to improve the treatments.

Though excitement has been building around the microbiome and cancer for about the past three years, the research around it goes back further. A 2013 study out of the Gustave Roussy cancer centre found that a drug called cyclophosphamide worked by damaging the mucus layer in the intestine. This damage led to gut bacteria traveling into the spleen and lymph nodes and thereby activating certain immune cells that helped fight tumors. When the drugs were tested on germ free mice, they all but lost their anticancer properties.

Cancer treatments success dependent on the microbiome

The study on cyclophosphamide moved its leader, Laurence Zitvogel, to test out the impact of the gut microbiome on other classes of cancer drugs, namely a type of immunotherapy drug called a checkpoint inhibitor. These drugs are very effective in treating certain cancers but only in about 20-40% of people.

Zitvogel wanted to see if the drugs efficacy was impacted by microbial composition, so she tested the drug in mice. In the study her and her team showed that germ free mice had a poor response to the drug, while mice with an abundance of the bacteria, Bacteroides fragilis responded better.

Could FMT be used on cancer patients?

A 2018 study reported the safe use of FMT’s to replenish the microbiomes of cancer patients after use of intense antibiotics. Could fecal microbiota transplants also be used in order to improve outcomes from certain anti-cancer drugs?

As of we don’t have an answer to that question but there are promising early studies. One such study out of the Sheba Medical Center in Ramat Gan, Israel trialed FMT’s efficacy in assisting immunosuppressant drugs in cancer patients. They did so by taking stool from cancer patients for whom PD-1 blockers had been effective and transferring it into patients who had failed to respond to the same drug. In the end two of the three patients who received transplants saw improvements in their responses to the drug.

As more studies such as this emerge, the way cancers are treated may change to include bacteria focused therapies. Employing not only the use of anti-cancer drugs but the use of the human microbiome.

Unlike the treatment of C Diff or Autism, FMT is not being examined as a singular treatment for cancer. Instead it is a part of a movement to integrate the microbiome into existing medicine, in order to advance already effective treatments and therapies.