The U.S. has recently seen a major breakthrough in cancer treatment called immune checkpoint inhibitors. These inhibitors basically tell the immune system which cells in the body to attack as they point them towards cancerous cells. However, these new treatments aren’t effective for all patients, and they sometimes have side effects. By determining which groups of people may respond better to this new treatment, doctors are hoping to personalize cancer treatment to be the most effective for each patient. Recent research has shown that the key to understanding how to fight tumors seems to come from the gut microbiome, the community of bacteria that resides in the stomach that helps the body fight disease.
A new worldwide research project involving forty doctors from three hospitals has found a connection between the gut microbiome and the immune system’s ability to fight cancer. In a study using mice, the doctors found a mix of 11 bacterial strains that launched an immune system attack on melanoma, a type of skin cancer.
There also seems to be a connection between patients who have a smaller number of proteins in their body and patients who respond well to immune checkpoint inhibitors. This could be a tool that helps to personalize cancer treatment because it will be simpler to find which patients will respond well to the new treatment.
Dr. Thomas Gajewski, a professor at the University of Chicago School of Medicine, says that a lot of patients have already seen the benefits of immunotherapy. But by continuing this research, they are hoping they can see a greater number of patients respond positively to these new treatments. Gajewski also says the link between proteins and response to the new treatments is important in developing new therapies.
The American Cancer Society says that metastatic melanoma, a skin cancer that spreads to a secondary site in the body, is still the most deadly form of skin cancer. The new treatments only help about half of all melanoma patients, and sometimes the treatments become ineffective after a while.
However, more and more evidence has begun to support the importance of the gut microbiome in fighting off diseases like cancer. Traditional antibiotics are now being shown to decrease the efficacy of the new treatments, while the introduction of the microbiome bacteria increases efficacy. The link between these bacteria and the proteins in each individual can be used to select which patients will respond to which treatments best.
Dr. Ze’ev Ronai has spent most of his career researching how cancer responds to treatments and learns to fight back. His most recent study involves mice that don’t have the correct genes to remove damaged proteins from the body. These mice experienced a halt in the growth of melanoma in their bodies, so long as they had a healthy gut microbiome. When the mice were given the traditional antibiotics, they no longer fought the melanoma well. The proteins identified in the earlier human study also had a connection to a strong immune system response in the mice.
The researchers found 11 bacterial strains in the mice that helped them fight the tumor effectively. When the researchers introduced these bacteria to mice that did not have them, those mice also began to fight the tumors better. The scientists then began to apply these findings to humans and found that the same thing applied. When humans were unable to remove the damaged proteins, they responded better to the new cancer treatments.
The next step in the process is for the researchers to find what exactly the bacteria are producing that stops the tumor growth. This will allow them to find other ways to increase the presence of these factors to fight melanoma, and maybe even other cancers.