A New Hope for Cancer Patients: CAR T-Cell Therapy

T-cells are a type of white blood cell that are a component of the immune system. These cells work as parts of the body's cell-mediated immunity, meaning they protect the body by killing bacteria, viruses, and cancer cells without the use of antibodies. There are many types of T-cells; for example, helper T-cells recruit other immune cells to organize an immune response, or natural killer T-cells (NKT) which participate in anti-tumor responses. So, how are T-cells being implemented in treatment for cancer patients?

Background:

Cancer is most commonly treated through surgery, chemotherapy, or radiation therapy; however, researchers have discovered different forms of treatment in the past decade. Immunotherapy has been shown to shrink and even remove cancerous tumors through the use of immune-boosting drugs. The therapy ultimately boosts the immune system, helping the body fight cancer.

CAR T-Cell therapy is a new form of immunotherapy that has caused much interest among researchers and oncologists. This treatment is used to treat blood-related cancers such as lymphoma and leukemia. CAR T-cells are still not widely used to treat cancer, however, the therapy has entered “the mainstream of cancer treatment” [1].

How it Works:

First, normal T cells are collected from the patient. Normal T cells won’t go after cancerous cells as they appear to be normal. The T cells are re-engineered in a laboratory to produce proteins called chimeric antigen receptors (CARs) on the cells’ surface. The CARs allow the modified T cells to identify and bind to specific proteins on the targeted cancer cells, then kill the cells.

The T cells are “grown” in the laboratory until there are enough to infuse into the patient. The CAR T cells are then expected to expand further in number within the body and destroy all cancer cells.

Issues to be Considered:

CAR T cell treatment causes severe side effects. The treatment also kills off healthy cells and could lead to a “mass die-off of antibody-producing B cells and infections”[1]. Other side effects may also occur due to the mass use of T cells. For example, T cells release cytokines*, and if the cytokines flood the bloodstream, it could lead to cytokine release syndrome (CRS)*. However, mild side effects can be managed using additional therapies.

Another issue is the neurological effects of T cell therapy. The therapy may cause “severe confusion, seizure-like activities, and impaired speech”[1]. As the cause of these side effects is still unclear, effective treatment is still being researched.

Who Does This Help?

CAR T-cell treatment is currently approved for children and adolescents with more advanced acute lymphoblastic leukemia (ALL)*, the most common cancer in children, or who have relapsed. The results have shown to be positive; for example, an NCI-led research team reported that of the relapse children who were treated with CAR T-cell therapy, “More than half the children went on to receive a potentially curative stem-cell transplant [...] and approximately 60% of those children were still alive 5 years later without their cancer coming back or the children experiencing any disease-related problems”[1].

*acute lymphoblastic leukemia (ALL): A type of cancer of the blood and bone marrow that affects white blood cells.

*cytokines: chemical messengers that help stimulate and direct the immune response

*cytokine release syndrome (CRS): infused T cells flood the bloodstream with cytokines, causing serious side effects, including dangerously high fevers and precipitous drops in blood pressure

Sources:

1. “Car T Cells: Engineering Immune Cells to Treat Cancer.” National Cancer Institute, https://www.cancer.gov/about-cancer/treatment/research/car-t-cells.

2. Indranil Mallick, MD. “The Role of T-Cells in Cancer.” Verywell Health, Verywell Health, 24 May 2022, https://www.verywellhealth.com/t-cells-2252171.

3. ​​“NCI Dictionary of Cancer Terms.” National Cancer Institute, https://www.cancer.gov/publications/dictionaries/cancer-terms/def/t-cell.

The Children's Hospital of Philadelphia. “Car T-Cell Therapy.” Children's Hospital of Philadelphia, The Children's Hospital of Philadelphia, 21 Aug. 2017, https://www.chop.edu/treatments/car-t-cell-therapy-immunotherapy-b-cell-acute-lymphoblastic-leukemia.