Liver cancer can be hard to treat and has a relatively low survival rate. Immunotherapy is a promising way of treating many forms of cancer, including liver cancer. In this form of treatment, doctors target the immune system and alter its activity in ways that fight cancer. However, researchers haven’t known a lot about how immune cells are involved in liver cancer development, which is critical information if immunotherapy is going to be used.
A team of researchers recently published a study in the journal Nature that provides new information about the immune system’s involvement in liver cancer. The researchers say that the study is a strong demonstration of how the immune system helps to prevent liver cancer.
Immune cells have different roles in cancer
One condition that increases the risk of liver cancer is non-alcoholic fatty liver disease, which is associated with obesity and is expected to become the most common cause of liver cancer in the near future. In this condition, the immune system attacks fatty tissue in the liver and scar tissue develops. This can lead to more advanced liver damage, eventually increasing the risk of cancer.
At the same time, the immune system constantly monitors the body and for material that doesn’t belong. Immune cells called T cells are highly effective at attacking cancer cells, and when this surveillance system is operating properly, it is very effective at eliminating cancer before it ever becomes a problem.
The researchers in this study focused on 2 different types of immune cells that appear to have opposite functions in order to understand how liver cancer develops. One type of immune cell promotes cancer development, while the other prevents it. This “push-pull” relationship influences whether cancer actually develops.
Immune cells influence each other
In this study, the researchers focused on liver cancer related to non-alcoholic fatty liver disease. They found that livers with this disease have higher levels of a type of immune cell that suppresses the T cell attacks on cancer cells.
The researchers found that these the immune suppressing cells and T cells directly affect each other. The immune suppressing cells had a direct effect on reducing cancer-fighting T cells and promoting cancer development. And when the researchers reduced the levels of the immune suppressing cells, the T cells bounced back and were able to relaunch an attack on the cancer cells, stopping fatty liver disease from becoming cancer.
The researchers also discovered that a protein called PD-L1 is involved in generating the immune suppressing cells that allow cancer to grow. Importantly, this same protein is involved in suppressing the immune system in other forms of cancer, and therapies already exist that block the activity of this protein.
This research explains how a properly functioning immune system helps to prevent liver cancer development, and it provides details about what goes wrong among these cells to lead to cancer. Researchers can now use these details, and the knowledge that there may be similarities to other cancers, to explore using immunotherapy for liver cancer in an effort to improve treatment and survival.
Eileen Hoftyzer, BSc, and Carolyn Goard, PhD