Adoptive cell therapy treats cancer by taking advantage of the immune system's killer cells, the T cells. At its most basic, this involves removing cells from the patient, greatly enhancing their numbers, and then giving them back to the patient.
Adoptive T-cell therapy (ACT)
ACT increases the number of a person's own tumour-fighting T-cells.
What is Adoptive T-cell therapy?
ACT is a treatment used to help the immune system fight diseases, such as cancer or infections due to certain viruses. This therapy increases the number of T-cells that are able to kill cancer cells or fight infections.
T-cells are collected from a patient's blood or tumour and grown in the laboratory. Once there are enough T-cells, they are given back to the patient to help their immune system fight disease in general.
How ACT is used
Adoptive T-cell therapy could be used in those cancer patients who do not seem to have a good immune response to tumour cells prior to treatment, and therefore may not respond to being “unblocked" by checkpoint inhibitors.
Adoptive T-cell therapy involves the development of a “new drug" for each patient, with T-cells grown for weeks in culture and patients hospitalised to receive therapy. The new drug that is created cannot be given to other patients. As a result, this process is expensive. (In contrast, therapies like checkpoint inhibitors can be used broadly, and represent a more cost-effective approach for the patients that respond to them.)
ACT has been shown to induce regression of established tumours in melanoma, certain types of leukaemia, and prostate cancer.
Using ACT for brain tumours
CAR-T cell therapy is a type of ACT that researchers are currently investigating for use on brain tumours.
This is a promising new way to get immune cells called T-cells to fight cancer.
T-cells are removed from the patient's blood and genetically altered in the lab to have sensing proteins (receptors) on their surface. These receptors recognise specific proteins on the surface of tumour cells. (The receptors on the T-cells are called chimeric antigen receptors, or CARs – hence the name CAR-T cell therapy.)
The T-cells are then multiplied in the lab and given back to the patient, where they can now seek out the tumour cells in their body and launch a precise attack against them.
Research and clinical trials of CAR-T cell therapy
In a pre-clinical study, researchers found that 67% of glioblastomas have a protein called CSPG4 on many of their cells. T-cells engineered to have receptors that attach to the CSPG4 proteins have been shown to control the growth of tumour cells in the lab and in mice. It is hoped a clinical trial will follow.
Other studies have targeted EGFR proteins, which are expressed in about 25% of glioblastomas.
Currently, there are only few CAR-T cell therapies approved for use for certain types of advanced, hard-to-treat leukaemias and lymphomas. They have had mixed results in treating solid tumours, such as brain tumours, where they have caused serious side-effects - some of which can be fatal.
Doctors are still improving how they make the T-cells in the lab and are learning the best ways to use them for different types of cancer.
CAR-T cell therapies being studied are only available in clinical trials for patients whose cancer is not responding to treatment or which has returned after treatment.
Researchers are also still learning about long-term side-effects of these treatments.
CAR-T therapy is being studied as a treatment for glioblastoma.