How Effective is Gene Therapy for Cancer Cure?

How Effective is Gene Therapy for Cancer Cure?

How Effective is Gene Therapy for Cancer Cure?:

• Gene therapy is a medical approach that treats or prevents disease by correcting the underlying genetic problem. Gene therapy techniques allow doctors to treat a disorder by altering a person’s genetic makeup instead of using drugs or surgery.
• Gene therapy, which involves replacement of a defective gene with a functional, healthy copy of that gene, is a potentially beneficial to cure cancer.

Genome Editing and CRISPR-CAS9: Definition | Working | Advantages | Challenges

What is the Case?

• Scientists in the United Kingdom test­ing a new form of cancer therapy, reported success in a teenaged girl, Alyssia, with a form of cancer called T­cell acute lymphoblastic leukaemia.
• The team at Great Ormond Street used a technology called base editing, which was invented only six years ago.

What happens in T­cell acute lymphoblastic leukaemia?

• In this form of blood cancer, the T­cells, which are a class of white blood cells, equipped to hunt and neutralise threats to the body, turn against the body and end up destroying healthy cells that normally help with immunity.
• The disease is rapid and progressive and is usually treated by chemotherapy and radiation therapy.

What is ‘base editing’ Technique?

• Bases are the language of life. The four types of base – adenine (A), cytosine (C), guanine (G) and thymine (T) – are the building blocks of our genetic code.
• Just as letters in the alphabet spell out words that carry meaning, the billions of bases in our DNA spell out the instruction manual for our body.
• Or we can say, a person’s genetic code is several permu­tations of four bases: Adenine (A), Guanin (G), cytosine (C) and thymine (T).
• In Alyssia’s case, her T­cells — per­haps because of a mis­arrangement in the sequence of bases — had become cancer­ous. A way to correct this mis­arrangement could mean a healthier immune system.

What is CRISPR Technique?

• In the last two decades, the world of biomed­ical engineering has been enthused by a technique that allow genes to be altered and errors ‘fixed.’ The most popular among these approaches has been the CRISPR­cas9 system.
• Inspired by how certain bacteria defend themselves against viruses, by snipping out and storing pieces of their genes, the CRISPR­cas 9 system, consists of an en­zyme that acts like molecular scissors.
• It can be made to cut a piece of DNA at a pre­cise location and a guide RNA can be used to insert a changed genetic code at the sites of incision.
• While there are a few ways to effect such changes, the CRISPR­ cas9 system is believed to be the fast, most versatile system to effect such gene edit­ing.
• While still a nascent technology, base editing is reportedly more effective at treating blood disorders which are caused by so­called single point mutations, or when a change in a single base pair can cause terminal disease.

How did base­editing work for Alyssia’s therapy?

• The objective of the gene therapy in the case of T­cell leukamia was to fix her im­mune system in a way that it stops making cancerous T­cells.
• First, healthy T­cells were extracted from a donor and put through a series of edits. The first base edit blocked the T­cells targeting mechanism so it would cease attacking Alyssa’s body, the second removed a chemical marking, called CD7, which is on all T­cells and the third prevented the cells being killed by a chemotherapy drug.

• Finally, the T­cells were programmed to destroy all cells — cancerous or protective — with CD7 marked on it. After spending a month in remission, she was given a second donor transplant to regrow her immune system that would contain healthy T­cells.
• Three months after the treatment, her cancer seemed to resurface but the most recent investigations suggest no signs of it.

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