Immunotherapies have emerged as an effective way to treat cancer. Scientists are very hopeful about these new treatments, which use the body's own defense system to shut down cancer. Several kinds of immunotherapies are already being used to treat certain types of cancer, and ongoing research, including at the University of Chicago, may reveal more possibilities.
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What is immunotherapy?
Immunotherapy is a treatment that strengthens the ability of the patient’s own immune system to detect and destroy cancer.
Cancer cells often have mutations that allow them to escape the immune system. Immunotherapy drugs are designed to boost the cancer-fighting powers of immune cells in order to give the immune system the upper hand.
Although the principles of immunotherapy have been around for a long time, the field has gained momentum during the past decade due to multiple scientific advancements. Based on the overwhelmingly successful results of a number of clinical trials, Science named cancer immunotherapy the “Scientific Breakthrough of the Year” in 2014. Researchers hope they can effectively treat cancer with fewer side effects than other treatments.
How does immunotherapy work?
It is normal for cells to grow and divide, but there are processes within cells that tell them to stop growing. When these processes fail, cell growth can go haywire. These abnormal cells can develop into cancer and overtake healthy organs and tissues, eventually spreading outside the immediate area to other parts of the body.
Usually, the immune system detects and destroys abnormal cells and keeps the growth of potential cancer cells in check. The immune system consists of white blood cells and the organs and tissues of the lymphatic system, such as the thymus, spleen, tonsils, lymph nodes, lymph vessels and bone marrow.
However, cancer cells sometimes acquire clever ways of avoiding destruction by the immune system. Because cancer cells originate as normal cells, the immune system doesn’t always recognize them as foreign. Cancer cells can also take advantage of genetic changes that make them invisible to the immune system; they can contain proteins that “turn off” immune cells; or they can alter how the immune system responds.
To overcome this, researchers have found ways to help the immune system detect and attack cancer cells, just as it would viruses, bacteria or other foreign invaders.
What are the main types of immunotherapy?
There are several different kinds of immunotherapies currently used to treat cancer. Two main types are checkpoint inhibitors and cellular immunotherapy.
Many cancer immunotherapies rely on the activation of T cells—a kind of immune cell that can recognize specific markers on tumor cells and attack them. One way that cancer cells escape T cells is by sending false signals to immune cell “checkpoints” to make themselves look harmless. A class of drugs known as immune checkpoint inhibitors block these false signals, so the immune system isn’t tricked into ignoring tumors.
This discovery was so important that, in 2018, American immunologist James P. Allison and Japanese immunologist Tasuku Honjo were jointly awarded the Nobel Prize for their work that led to the development of checkpoint inhibitors.
Another type of immunotherapy known as cellular immunotherapy uses the “Trojan horse” concept to overcome cancer. Immune cells are taken from a patient’s body, modified in a lab, and replaced back into their body in large numbers to help the immune system fight cancer.
One example is CAR T cell therapy, which takes a patient’s T cells and adds a gene called a chimeric antigen receptor, or CAR. When the modified T cells are placed back in the body as CAR T cells, they’re “supercharged” to recognize cancer cells and fight them. This therapy gives adults and children with blood cancers, such as leukemia and lymphoma, a promising new treatment option. (The University of Chicago Medicine was the first site in Illinois to offer this therapy in 2017.)