Scientists in the United Kingdom testing a new form of cancer therapy, reported success in a teenaged girl, Alyssia, who has T-cell acute lymphoblastic leukaemia. Alyssia was the first to receive experimental gene therapy that relied on a new technique called 'base editing.'
The objective of the therapy in the case of T-cell leukamia was to fix her immune system in a way that it stops making cancerous T-cells.
- Gene therapy is a promising approach to cancer treatment that involves using genetic material to treat or prevent disease. In the case of cancer, gene therapy can be used to boost the body's natural defence mechanisms against cancer cells, or to directly target cancer cells with therapeutic genes.
- T-cell acute lymphoblastic leukaemia is a type of cancer that affects a type of white blood cell called T cells. T cells are an important part of the immune system, and T-cell acute lymphoblastic leukaemia occurs when T cells in the bone marrow become cancerous and multiply uncontrollably. T-cell acute lymphoblastic leukaemia is a fast-growing cancer that can spread quickly to other parts of the body, and it is most common in children, but it can also affect adults.
- Symptoms of T-cell acute lymphoblastic leukaemia can include fatigue, fever, weight loss, and bruising or bleeding easily. The diagnosis of T-cell acute lymphoblastic leukaemia is typically made through a combination of blood tests, bone marrow biopsy, and imaging tests.
- Treatment for T-cell acute lymphoblastic leukaemia typically involves chemotherapy, which uses drugs to kill cancer cells. In some cases, a bone marrow transplant may also be necessary. The prognosis for T-cell acute lymphoblastic leukaemia varies depending on the stage of the cancer at the time of diagnosis, but overall, the long-term outlook has improved significantly in recent years due to advances in treatment.
- Base Editing’: A person’s genetic code is several permutations of four bases: Adenine (A), Guanin (G), Cytosine (C) and Thymine (T). Sequences of these bases, akin to letters in the alphabet, spell out genes that are instructions to produce the wide array of proteins necessary for the body’s functions.
- In Alyssia’s case, her T cells — perhaps because of a mis-arrangement in the sequence of bases — had become cancerous. The sequence of genes can be altered and errors can be fixed by the CRISPR Cas9 system. While still a nascent technology, base editing is reportedly more effective at treating blood disorders which are caused by so-called single point mutations, or when a change in a single base pair can cause terminal disease.
- How did base editing work for Alyssia’s therapy? The objective of the gene therapy in the case of T cell leukaemia was to fix her immune system in a way that it stops making cancerous T cells. First, healthy T cells were extracted from a donor and put through a series of edits. The first base edit blocked the T cells targeting mechanism so it would cease attacking Alyssa’s body, the second removed a chemical marking, called CD7, which is on all T cells and the third prevented the cells being killed by a chemotherapy drug. Finally, the T cells were programmed to destroy all cells - cancerous or protective - with CD7 marked on it.
Gene therapy is still an experimental approach to cancer treatment, and it is not yet widely available. However, it has shown promise in early-stage clinical trials and researchers are continuing to study its potential as a treatment for cancer.