Above: Illustration of adoptive cell transfer (ACT), a form of cancer immunotherapy (Wikimedia Commons/Simon Caulton)
Did you know? T-cells are a type of white blood cell that leads the body’s immune response to malignant (cancerous) and infected cells. Your body’s immune system protects you from external threats like bacteria, viruses, and other infectious agents. But did you know that it also protects you from cancer? In fact, your immune system can recognize and kill developing cancer cells before they grow into life-threatening tumours.
Scientists are exploring how the immune system’s natural ability to attack cancer cells can be harnessed for treating patients with many different kinds of cancer. Enhancing or supplementing a patient’s natural immune response against cancer cells is called cancer immunotherapy.
There are two ways that developing cancer cells can evade the immune system and form tumours: they can either avoid being recognized or make it hard to attack them. For example, cancer cells can send chemical signals to the body that limit or stop an immune response, allowing the cancer to continue to grow.
Types of immunotherapy
Did you know? There are three kinds of T-cells, all of which can play a role in cancer immunotherapy: helper T-cells, killer T-cells, and regulatory T-cells.Different kinds of cancer immunotherapy help prevent cancer cells from being able to hide from the immune system or evade its attacks. Checkpoint modulators are one example. These molecules lift the “brakes” placed on the immune system by chemical signals from cancer cells, clearing the way to attack the cancer.
Another example is adoptive cell transfer (ACT), which involves collecting a patient’s tumour-fighting white blood cells, called T-cells, from a tumour sample. The T-cells that are best at fighting cancer cells are chosen and more of them are produced in a laboratory. A large population of these “elite” T-cells is then put back into the patient, resulting in a more potent attack against the cancer.
T-cells collected from a patient’s blood can also be biochemically modified or reprogrammed to make them more effective at recognizing and killing cancer cells. One exciting example of ACT research involves reprogramming T-cells to fight acute lymphoblastic leukemia (ALL), which causes the largest number of cancer deaths among children.
Other kinds of cancer immunotherapy include cancer vaccines, which use substances derived from tumours to enhance the body’s ability to fight cancer and oncolytic viruses, which are viruses that infect and kill cancer cells (but not healthy cells).
Advantages over other cancer treatments
Did you know? Cancer vaccines work the same way as vaccines for diseases hepatitis, tetanus, and chicken pox. They use molecules that cause the disease to stimulate your body’s immune response, but without actually causing the disease.Immunotherapy offers many advantages over existing cancer treatments. Since it uses a patient’s own immune system to combat cancer, it has the potential to be much more effective than externally administered drugs. It also trains patients’ immune systems to better recognize and attack cancer cells, which means it can provide long-lasting protective effects against future relapses.
And since it uses the body’s natural defense mechanisms to specifically target cancer cells, cancer immunotherapy would have fewer side effects than chemotherapy drugs, which target all rapidly dividing cells—including "good" cells in the hair, nails, bone marrow, and gut. Finally, immunotherapy could potentially be tailored to specific types of cancer, meaning it could help a broad range of patients.
For all these reasons, the cancer research community is extremely excited about cancer immunotherapy. The number of success stories remains small for the moment, since many of the treatments are still at the experimental stage and only a few have been approved for clinical use. But used in combination with existing treatments—including chemotherapy and radiation therapy—immunotherapy may allow cancer patients to live longer and more fulfilling lives with the help of their own immune cells.