Is there any hope for people who are suffering from incurable diseases? Modern medicine shed light in the darkness in the form of a novel therapy, gene therapy.
Gene therapy is a relatively new experimental technique, which uses the gene to treat, prevent or limit illness development. It is based on medical procedures that take place at the cellular level. It seems to be a very promising method and is currently at the testing stage. Let’s take a close look at this promising treatment.
Image Credit: Konstancja Gołębiowska & Julia Majka
NEW HOPE AND ITS TYPES
Probably, everyone has heard about genes? We all have them. Thinking about humans, or animals we can say that genes are the pieces of DNA (from a chemistry point of view molecules, which are unique carriers of the genetic information determining like eyes color, the shape of the nose, the hair color that we have) [1].
Moreover, genes can also be used in medicine at the molecular level, as gene therapies [2], where cells with some defects can be repaired by introducing genetic material from viruses into them. Figure 1 shows how it works. When we lead a gene directly into a cell, it often does not perform its function correctly. An alternative way is to use a genetic vector, a carrier of this gene [3]. Different genetic vectors or pharmacological preparations are used depending on the expected result in a given therapy.
Can viruses have positive capabilities? Yes, and we can use this potential in gene therapies. Let's say “wrong” genes are producing defective protein. If we know in which of the patient's genes is a mutation, we can choose the proper genetic vector. Next, it can be introduced into the cells to synthesize the “correct” protein. So, this genetic vector plays a role in the repair tool. This therapy is not always effective; in fact, it works only if the defective protein is not active, and it is not inhibited or impair the action of the normal protein [4]. What about other cases?
There are three main types of gene therapy:
- Replacing the “wrong” gene responsible for the disease.
- Inactivating the “wrong” gene.
- Introducing a new gene into the body to help fight the disease.
The first one works only in the very early disease stages. This type of therapy allows, for example, to correct the gene responsible for sickle cell anemia, which is a fatal disease. Then, new, precise gene-editing technologies can help.
What about ethical issues? Opinions about gene therapy are divided. In many countries, the method of replacing the “wrong” gen is prohibited. In other cases, the original genetic defect is not removed. It remains in the cells and can be passed onto the next generation. We can act on a “wrong” gene by “switching on” and “switching off”, or introduce products that will destroy a particular cell or inhibit its growth. The second case is used, for example, to treat cancer [5].
Figure 1. Gene therapy, which used a vector gene. Image Credit: Konstancja Gołębiowska & Julia Majka
APPLICATION FIELDS
Genetic engineering may be a hope to treat some diseases, or the genetics tool, which gives us the possibility to change humans' physical appearance, metabolism and even improve mental features like memory and intelligence. Some see it as an opportunity to design their perfect baby. But should it be so? Is it ethical?
Genetic diseases are caused by gene mutations in the DNA chain, e. g. deletion, i.e. falling out of a fragment of DNA, point mutation – replacement of a single nucleotide by another, abnormal one, inversion – rearrangement of sections of the nucleotide sequence [6]. Here, gene therapy may help. Mono-gene diseases, which can be treated with gene therapy, are: phenylketonuria, ADA deficiency, or cystic fibrosis.
Gene therapy can also be used as a treatment for cancer patients. The application in this area is based on the premise that cancers arise from defective host genes. It is theoretically possible to prevent further cancer development by replacing a defective tumor suppressor gene with a correct one [7]. While gene therapy in cancer treatment is very likely, its application to genetic diseases is much more difficult. In the second case, the gene carriers are not safe enough, and its development is still going on. The genetically modified spider silk proteins can be one of them.
Another critical aspect of gene therapy is the blocking of the synthesis of defective proteins. An example can be RNA interference (also called post-transcriptional gene blocking). Such a process occurs naturally in cells as a system of protection against viruses. This technique involves combining small molecules of different types of RNA, which causes degradation of ribonucleic acid and prevents the gene translation process.
ADVERSE EFFECTS
A lot of controversy surrounding gene therapy arises, medical as well as ethical. From the medical perspective, we have to deal with so-called side effects (undesirable activity). So far, there have been many different kinds of adverse effects and even death.
The problem of gene therapy is developing methods to precisely deliver genes to the patient's target cells and create carriers that will not induce an adverse immune system response. Each body may respond differently to gene therapy. Symptoms may include severe chills, fever, nausea, vomiting, or headache. At this point, the use of gene therapy has led to the death of two people – a boy with an immune disorder and a teenager suffering from rare liver disease (probably by overly rapid immune system response) [8].
ETHICAL ISSUES AND LEGAL REGULATIONS
It is a real mission impossible to talk about gene therapy without addressing the ethical aspect. This therapy is a controversial technique, while some are conducted on sperm, ova, zygotes, or early embryos [9]. The consequences of such interference prove challenging to assess, as changes in the genome could be fixed and passed onto offspring. On the other hand, there is a blanket ban on human germline gene therapy in international legislation. The position of Christian ethics is negative on this issue.
Other gene therapy receives a different ethical evaluation because it does not interfere with the genotype of germ cells but merely attempts to repair some defect in a single organ or tissue. The genotype of the whole person is not changed. One can morally justify such genetic surgery because, in this case, a single gene is sacrificed or replaced with a healthy gene for the good of the whole [10].
When gene therapy is the only way to save a patient's life, it may be justified. The patient's explicit consent to a procedure must be given entirely voluntarily and after sufficient familiarization of the patient with the form of therapy to be undertaken. Patient privacy should be protected, and medical confidentiality should be maintained as with standard treatment [11].
Despite many years of research and experience, gene therapy is not commercially available until now. There are currently clinical trials worldwide to introduce it into treatment, but most of the methods are in the first and second phases of problems, which are aimed primarily at testing the safety of the therapy.
When it comes to legal issues, they are primarily handled by the FDA and the National Institutes of Health (NIH). The FDA deals with issues regarding the control and safety of gene therapies. Their consent is necessary for the introduction of any gene therapy. The NIH also plays an essential role in regulation. All gene therapy studies that the NIH supports must be approved [12].
Summary
Gene therapy relies on foreign nucleic acids (DNA or RNA) into the patient's cells. These new structures are supposed to have a therapeutic effect. It changes the defective genetic record of an ill person resulting in disease (mutated gene, defective genetic material). This medical treatment causes a lot of discussion in the world. Some countries even prohibit it.
It is a great promise but also considerable risk. Currently, it is in the test stage for diseases that have no other cures. What does the future bring? Let's see…
This article is a joint work of Oliwia Raniszewska (Faculty of Chemistry, University of Warsaw), Emilia Cywińska (Faculty of Chemistry, University of Warsaw), Julia Daszkiewicz (Faculty of Chemistry, University of Warsaw), Agnieszka Pregowska (Institute of Fundamental Technological Research, Polish Academy of Sciences) as a part of the Science Embassy project. Images Credit: Konstancja Gołębiowska & Julia Majka.
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