Science for all newsletter – The Hindu

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Scientists may have unlocked a new milestone in cancer treatment. An individual who received CAR T-cell therapy has been in remission for 18 years without requiring any other treatments, researchers reported in Nature Medicine on February 17.

The individual in question had neuroblastoma, a type of nerve cell cancer.

‘CAR’ is short for ‘chimeric antigen receptor’. CAR T-cell therapy uses genetically altered immune cells to target cancer cells and destroy them.

T cells are a type of white blood cells. They perform a variety of functions in the body’s immune response: they activate other immune cells, directly fight cells infected by a pathogen or cancerous cells, and help the immune system ‘remember’ past infections to mount a more effective defence against it in future.

All T cells develop from stem cells in the bone marrow. They have receptors that identify antigens, or foreign substances, and start the process of destroying them.

Sometimes, cancer cells have antigens that the T cells don’t identify as foreign substances, allowing them to get by without provoking an immune response that would fight or kill them. CAR T-cell therapy works by ‘upgrading’ these T cells to not miss any cancer cells.

The T cells are genetically engineered to have a new, specific type of receptor that can bind to cancer cells and kill them. These cells can also be modified to fight specific types of cancer antigens so that they are more potent. The artificial receptors are the chimeric antigen receptors, or CAR.

The CAR T-cell therapeutic procedure is straightforward. Medical workers withdraw blood from the individual, isolate the T cells in it, then modify those cells in the laboratory to produce the CARs on their surfaces. Once they do, the workers make multiple copies of the T cells and infuse back into the individual’s bloodstream.

The authors of the newly published study have expressed belief that 18 years may be the longest yet an individual has been cancer-free after receiving CAR T-cell therapy. This extended remission is more important because the procedure has proven less effective against solid tumours — and neuroblastoma is a solid-tumour cancer.

The individual who received CAR T-cell therapy did so during a clinical trial conducted between 2004 and 2009 with 18 other participants, all children with neuroblastoma at the time. Twelve of these children died between two months and seven years after the treatment as their neuroblastoma relapsed. Of the seven survivors, five continued follow-up therapies for at least 13 years after treatment.

One, of course, beat neuroblastoma for 18 years without other therapeutic assistance.

Since developing CAR T-cell therapy, researchers have improved it significantly. The fourth generation of therapy today involves ‘armoured CARs’, which can also secrete cytokines, molecules the body uses to coordinate its immune response. Thus armoured CARs made CAR T-cell therapy more potent.

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