This week, President Jimmy Carter announced he has been declared N.E.D (No Evidence of Disease) after undergoing treatment for metastatic melanoma, which was diagnosed in August of this year. President Carter credits this happy announcement to an immunotherapy treatment he received. Immunotherapy is a type of cancer treatment that uses the body’s own immune system to control cancer. Here’s what we know about this exciting new treatment option and how it works.
What is Immunotherapy?
“Immunotherapy is complex, but it really comes down to one thing- getting T cells to kill cancer cells.” Patrick Hwu, MD, MD Anderson Cancer Center- addressing an educational session at ASCO 2014.
Immunotherapy means using the body’s own defense system to fight cancer. It is a simple concept, but relies on very intricate mechanisms. For decades, efforts to use the immune system as an effective weapon against cancer were met with disappointment. Adding to the frustration was a convincing body of evidence that our immune systems are able to recognize and destroy cancer cells but frequently do not. Understanding the complex interactions between the immune system and cancer is the key to developing new therapies–and in the last few years a great deal of progress has been made in that area.
The immune system is a well- coordinated army that includes blood cells, the lymphatic system and a number of organs, including the skin, spleen and thymus gland. White blood cells, especially T cells and B cells, are the most important soldiers in this fighting force, and as Dr. Hwu noted in his talk at ASCO, the goal of most immunotherapy is to activate these cells to attack and destroy cancer cells.
What do T cells and B cells do?
T cells and B cells are highly specialized defenders. When your body is infected or when there are abnormal cells, the T and B cells recognize the invader and respond. They do this by identifying specific molecules on the surface of the cells called “antigens.” The T cells multiply quickly, attacking and destroying the unhealthy cells. The B cells, with the help of the T cells, make antibodies that stick to the surface of invaders or abnormal cells, stopping them in their tracks. Only recently have researchers begun to understand the ways in which cancer cells interact with the immune system and are able to deactivate T cells and B cells.
Different Approaches to Immunotherapy for Cancer
There are several ways in which the immune system can fight cancers:
By boosting the overall immune response: This is not specific to cancer. The goal is to stimulate a strong immune response that will enhance the body’s ability to fight infections or kill abnormal cells. Older forms of immunotherapy, such as interleukins, are examples of this approach.
Checkpoint blockades: We now know that cancer cells “turn off” the immune system by expressing proteins on their surface that tell the T cells not to attack. There are several mechanisms or pathways that the cancer cells use to deactivate the immune system.
Cancer vaccines: Today, there is only one vaccine approved to treat cancer, and it’s for advanced prostate cancer. However, there is a great deal of interest in developing vaccines for many types of cancer, including breast and lung cancers. The goal of any vaccine is to train the immune system to react to specific invader- or in the case of cancer, abnormal cells.
Adaptive T cell therapy: This approach involves removing a person’s own T cells, “re-engineering” them and injecting them back to fight the cancer. This approach has been used to treat some forms of leukemia and lymphoma and is now being studied in a number of other cancers.
Want to learn more about this fascinating, and ever-evolving treatment option? Check out our Frankly Speaking About Cancer education series on immunotherapy here.