Unleashing the Immune System to Attack Cancer
Immunotherapy is a treatment that uses the body's own natural defenses to fight cancer. White blood cells (T cells) that make up the immune system can be stimulated in several ways by specially designed drugs that allow them to recognize and kill cancer cells.
Early immunotherapy drugs worked in a general way by boosting the body’s immune system to fight cancer cells. However, recent research has discovered several proteins on the surface of T cells that act like a brake, or checkpoint, preventing them from attacking cancer cells.
CTLA-4 is one such checkpoint. Research on CTLA-4 led scientist Jim Allison in 1996 to propose blocking the protein as a cancer therapy. The findings by Allison, now chair of immunology at MD Anderson, led to the development and approval of ipilimumab, an immune checkpoint inhibitor that turns off CTLA-4 and allows the T cells to do their work. Ipilimumab has extended survival in patients with advanced melanoma.
Another checkpoint is PD-1, discovered in 2000. Several drugs have been developed to turn off PD-1 in many types of cancer, allowing existing T cells near the tumor to attack. Researchers continue to identify more checkpoints that can be exploited to fight cancer.
Adoptive cell therapy (ACT) approaches work in two ways. One method takes a patient’s own immune cells that recognize and attack cancer but are too few to succeed, multiplies their number to billions of cells in the lab, and then gives them back to patients. Another method genetically engineers a patient’s immune cells in the lab to recognize and attack their own specific cancer, expands their number and reinfuses them in the patient. Both methods are being developed in clinical trials for solid tumors and blood cancers.
Other immunotherapies fall into two general categories.
Targeted immunotherapies attack specific proteins on the surface of cells that help identify cancer and stimulate an immune response. Common types include:
Monoclonal antibodies are designed to identify specific abnormalities on the surface of cancer cells. Monoclonal antibodies attach themselves to these abnormalities, marking them as a target for the immune system.
Cancer vaccines help the body recognize cancer cells and stimulate the immune system to destroy them. Some vaccines contain cancer cells harvested from the patient’s tumor. Others contain proteins designed to attach themselves to cancer cells.
General immunotherapies are non-specific treatments that do not affect the cancer itself. They work on proteins called cytokines that send signals to stimulate the body’s immune system to fight cancer cells. Common types include:
Interleukins control the growth and activity of T cells. More than a dozen interleukins have been identified. Interleukin-2 (IL-2) is used to treat kidney cancers and melanomas that have spread to other regions of the body. Other interleukins are being studied as possible treatments for other types of cancer.
Interferons are a group of three proteins released by T cells in reaction to invading organisms. Interferons increase the immune system's reaction to cancer cells. Interferon alpha (IFN-alfa) is currently being used to treat melanoma, kidney cancer and certain types of leukemia and lymphoma.
Colony Stimulating Factors (CSF) strengthen the immune system by stimulating the production of white blood cells in the bone marrow. CSF therapies are used to help elevate low white blood cell counts after chemotherapy.
MD Anderson patients have access to clinical trials offering promising new treatments that cannot be found anywhere else.
Moon Shots Program
June 01, 2016
You’ve probably heard of immunotherapy. But what exactly is it? And who should consider immunotherapy?
At its most basic, immunotherapy uses the body’s own natural defense system to attack diseases like cancer.
We sat down recently with Padmanee Sharma, M.D., Ph.D., co-leader of MD Anderson’s immunotherapy platform, to learn more. Here’s what she had to say.
Let’s start with the basics. What is immunotherapy?...