CANCER GENE THERAPY
1. Introduction:
Scientists in the United Kingdom tested a new form of cancer therapyand, reported success with a form of cancer called T-cell acute lymphoblastic leukaemia.
2. Mechanism:
- In this form of cancer, the T-cells, which are a class of white blood cells, are equipped to hunt & neutralise e threats to the o body, turn against the body & end up destroying healthy cells that normally help with immunity.
- The disease is rapid & progressive & is usually treated by chemotherapy & radiation therapy.
3. Marked Treatment:
- A teenage girl named Alyssia, tried several of the standard treatments including chemotherapy & radiation but with limited success.
- Later she was enrolled in the trial testing on experimental medicine.
- This trial was led by doctors & scientists from University College London & Great Ormond Street Hospital.
- Alyssia was the first to receive experimental gene therapy that relied on a new technique called 'Base Editing'.
4. Base Editing:
- A person's genetic code is several permutations of four bases; Adenine (A), Guanine (G), Cytosine (C) & Thymine (T).
- Sequences of these, 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-because of mixed arrangement in the sequence of bases, might have become cancerous.
- A way to correct this arrangement could mean a healthier immune system.
- In the last two decades, the world of biomedical engineering was enthused by a technique thaallowsow genes to be altered & errors fixed.
- The most popular among these approaches is CRISPR-cas 9 system.
- Inspired by how bacteria defend themselves against viruses, by snipping out & storing pieces of their genes, the CRISPR-cas9 consists of an enzyme that acts like molecular scissors.
- It can be made to cut a piece of DNA at a precise location & a guide RNA can be used to insert a changed genetic code at the sites othe f incisions.
- The CRISPR-cas9 system is believed to be the fast, most versatile system to effect such gene editing.
- The CRISPR-cas9 system was improvised to be able to directly change certain bases like a C can be changed into G & T into an A.
| Base Editing is reportedly more effective at treating blood disorders which are caused by single point mutations or when a change in a single base pair can cause terminal disease. |
5. Base Editing for Alyssia:
- In Ithe n case of T-celleukaemiaia, the objective is to fix the immune system in a way that it stops making cancerous T-cells.
- Healthy T-cells were extracted from a donor & put through a serieofod edits.
- The first base edit blocked the T-cells targeting mechanism, so it would cease attacking Alyssia's body, the second removed a chemical marking called CD7, which is on all T-cells & the third prevented the cell from s being killed by a chemotherapy drug.
- Finally T-cells were programmed to destroy all cells i.e., 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 T-cells.
6. Effectiveness:
- Three months after the treatment, the patient's cancer seemed to resurface but the most recent investigations suggest no signs of it.
- Alyssia was one of 10 people enrolled in the trial to receive the treatment.
- It has been 1.5 years since she was first diagnosed with the disease & whether the treatment has reliably & entirely fixed her immune system, remains to be established.
