Many people likely know someone who has been affected by cancer, whether that be a friend or a family member. Because of this, many are also familiar with its devastating effects, not only on the person who is sick but also on everyone around them. But what exactly is cancer?
Cancer is the result of a mistake in cell division - when the cell’s DNA gets a mutation. This causes the cell to begin dividing uncontrollably, forming tumours that disrupt normal bodily functions. While we have made great progress in the ways in which we treat cancer, some cancers still do not respond to typical treatments such as surgery, chemotherapy or radiation. This is where CAR - T cell therapy steps in. Scientists are rewriting the patient’s genetic code and reprogramming their immune system to recognize cancer cells.
So how exactly does this work? In order to understand how CAR - T cell therapy works, it is first important to understand how your immune system works. You are constantly under attack by viruses, bacteria and fungi, and your immune system is very good at defending you against these invaders. You can think of the immune system as a security team, constantly defending you from “criminals” (the viruses, bacteria and fungi). Some of the immune system's best guards are white blood cells.
In the same way that police officers might sometimes ask for pieces of ID - drivers license, health card, etc, white blood cells check the “ID’s” of any cells that they might pass though these pieces of identification are called antigens, little protein fragments on the surface of cells. Two types of white blood cells are T- cells and B - cells.
T - cells have receptors that lock with particular antigens. If they find a match, they release toxic chemicals that destroy the cell membrane. B - cells create antibodies, proteins that latch onto particular antigens, ensuring that they are destroyed. While your immune system does a brilliant job at protecting you from pathogens (organisms that cause disease) that invade from outside, it has more difficulty spotting it when your own cells have turned against you, like what happens when someone has cancer.
The antigens on cancer cells don’t seem abnormal and hence, are not spotted by the immune system. Therefore, T - cells and B - cells won’t attack them. And sometimes, the cells that have the error are actually your white blood cells, meaning your immune system will really struggle to find the problem.
Scientists reprogram the patient’s immune system to recognize the antigens found on cancer cells. First, they need millions of the patient’s T - cells. In order to change what the T -cell does, they must reprogram its genetic code. DNA is made up of 4 bases, a bit like the fundamental building blocks of DNA. They are called adenine, guanine, thymine and cytosine. When reprogramming the patient’s T - cells, scientists can use a computer to put together their own sequence of these bases and model what it will do. Then, using a DNA printer they will make those sequences.
The modified T - cells have 3 main instructions. 1. Recognize and kill cancer cells - specifically it tells it to change the antibodies (proteins produced by B - cells that recognize particular antigens) so that they recognize the antigens found on cancer cells. 2. Copy itself when it finds the cancer cell. 3. Survive in the patient’s body. A vector is used to get the DNA into the cell - something that will easily infect it. Think of vectors like USB sticks. USB sticks can be used to transfer data to your computer and vectors are used to transfer the new code into a T - cell.
The name comes from the fire breathing chimera, a monster from ancient Greek legends. It had the head of a lion, the body of a goat and the tail of a snake, though now the word is used to refer to things that have two or more types of tissues or cells. The cell’s genetic code is part T - cell and part antibody (this comes from B - cells) so it's a chimera. And it goes in search of a particular antigen using its new receptor. Hence, CAR - T cell therapy.
Before inserting the reprogrammed T - cells into the patient’s body, the patient is first given chemotherapy to wipe their existing T - cells and then the CAR - T cells are inserted into the patient.
Unlike conventional chemical treatments, the CAR - T cells stay in the patient’s body for years. It is, however, a very expensive treatment, and it is quite difficult to make it work with common cancers such as breast or lung.
Ultimately, CAR - T cell therapy provides hope for the future of cancer medicine. It shows that perhaps one day, we will defeat this devastating illness.
References:
How to biohack your cells to fight cancer - Greg Foot. YouTube. (2019, April 9). Retrieved August 1, 2022, from https://youtu.be/Mt5C5fhuU_0
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