You may have heard about gene therapy, but you’re still a little confused about the topic, or you have absolutely no clue what on earth gene therapy is and you’re just here to learn more, but worry not! Whichever it may be, by the end of this article, I’m sure you’ll have a good understanding of the fundamentals of gene therapy.
Essentially, gene therapy is when a piece of DNA is inserted into a living organism to treat a genetic disease such as cystic fibrosis and cancer. The piece of DNA which is introduced to the organism consists of a functioning gene which aims to correct the effects of a disease-causing mutation.
There are two main types of gene therapy:
- Somatic Gene Therapy — The placement of DNA into somatic cells (cells which DO NOT produce sperm or egg cells). This way, the overall effect of gene therapy and the changes that are made to the genome are not passed down to the subsequent generations.
- Germline Gene Therapy — This is the opposite of somatic gene therapy; This is the placement of DNA into cells which DO produce reproductive cells. Thus, the effects of germline gene therapy are passed down to the following generations.
Although there are quite a few techniques for carrying out gene therapy, the following are the three most common techniques of gene therapy which are carried out.
- Gene Augmentation Therapy
Mutations in the DNA occur randomly within a living organism, while most mutations go unnoticed, some do have significant consequences, like a disease which prevents a gene from producing a protein. This is where gene augmentation therapy comes in as it tries to treat the mutations which stop protein production.
This procedure corrects the protein deficiencies which were caused by the mutated genes. It corrects them by introducing a healthy non-mutated version of the gene, which produce the necessary protein, without actually replacing the flawed gene in the DNA. This new gene then starts to produce the missing product at sufficient levels.
However, this form of therapy is only effective if the impact of the disease has not concluded in lasting damage to the body.
To give an example, gene augmentation therapy can be implemented to treat loss-of-function disorders, such as cystic fibrosis. This is done by inserting a functional copy of the gene to correct the disease.
2. Gene Inhibition Therapy
This therapy is for the treatment of inappropriate gene activity, which causes cancers, infectious diseases and inherited disease. Its objective is to place a gene which eliminates those genes which either inhibit (restrain) the expression of another gene or interferes with the product of another gene.
The purpose of this procedure is to inhibit the action of a gene which promotes the growth of cells related to disease.
For example, let’s take oncogene; a gene which is responsible for cell growth. When this gene is over-stimulated, it can result in cancer. So, by eradicating the activity of oncogene via gene inhibition therapy, further cell proliferation can be prevented and the cancer can be brought to a halt.
3. Killing Specific Cells
Although the previous two can treat most genetic diseases, the killing of specific cells is suitable for illnesses (i.e. cancer) which can be treated only by destroying the specific cells or when treatment with other forms of gene therapy is ineffective.
The goal of this therapy is pretty self-explanatory, to kill the cancer cells, by inserting genes that will result in the cell to die. Harsh. This procedure can be carried out in two ways:
- By inserting a strand of DNA into the cancer cell, containing a “suicide” gene that will produce toxins within the cell — resulting in its death.
- By injecting a strand of DNA which triggers the expression of an antigen that marks the diseased cells, such that the immune system of the body sends white blood cells to destroy it, consequently destroying the diseased cells as well.
However, it’s crucial that these cancer cells are targetted appropriately and with cautiousness to prevent targetting and killing healthy cells.
Okay, but how is the transfer of DNA done?
I’m glad you asked, DNA transfer is done by packaging the DNA containing the desired genes in a vector (a carrier of disease or of medication), which in this case is generally a virus, bacterium or a plasmid. The vector serves as a way of bringing in the new DNA into the recipient’s cell with a genetic disease.
However, we are posed with many challenges in the field of gene therapy. These include:
- Sending the gene to the right location and turning it on — It is important that the new gene reaches the correct cell because delivering a gene into the incorrect cell will be wasteful and may even cause health issues for the patient. Even after reaching the right cell, the gene has to be switched on; cells also try to hinder this process of switching on genes by shutting down genes which have been showing unusual behaviour.
- Rejection from the immune system — The primary role of the body’s immune system is to protect you from harmful substances. However, it is common that the immune system mistakes non-harmful foreign substances as “harmful”, and triggers attacks against them. So, sometimes new genes transported by gene therapy are deemed as possibly harmful intruders. Therefore, scientists are faced with the challenge of delivering the genes to the cells without being “noticed” by the immune system. This is generally achieved by using vectors that are less likely to cause an immune response.
- Ensuring that the new genes don’t affect the activity of other genes — In a perfect scenario, the newly introduced gene will mingle well within the genome and execute it’s assigned job without any issues for the rest of the patient’s life. However, the process does run the risk of hampering the activity of a pre-existing gene, which is a dangerous gamble as it might disrupt the work of a gene that regulates cell division, ultimately leading to cancer.
- Cost of gene therapy — It is no surprise that cost makes this list of the challenges we face with gene therapy. This is because gene therapy usually requires an approach on a case-by-case basis due to the fact that genetic disorders which can be treated by gene therapy are quite rare. But as technology progresses, we can definitely expect the cost of gene therapy to decline.
To conclude, although gene therapy remains quite risky at the moment, it is a powerful and a promising tool which is still, as I believe to be, in its early stages of development, with a huge potential of wide-spread use and treating some more common genetic disorders. That being said, gene therapy has a long road ahead and is where the future of healthcare is headed.