Researchers at Tel Aviv University warn: treatment with the CRISPR method may cause damage to the genome

According to the researchers: "The method is indeed very effective, but it is not always safe either. Sometimes chromosomes that have been cut in the procedure fail to recover and the stability of the genome is undermined - something that may in the long run even cause cancer"

A new study by Tel Aviv University indicates risks in the use of CRISPR technology. This is an innovative method for cutting and editing DNA, which won a Nobel Prize for its findings, and already forms the basis of advanced treatment for a variety of diseases, including cancer, liver and intestinal diseases, and genetic syndromes. The researchers examined the effect of the method on T cells - white blood cells of the immune system, and found that in a significant percentage of the cells there is a loss of genetic material, and the genome loses its stability - a situation that may cause cancer.

The study was carried out by a team of researchers at Tel Aviv University, led by Dr. Adi Barzel from the School of Neurobiology, Biochemistry and Biophysics in the Faculty of Life Sciences and the Dotan Institute for Advanced Therapies in collaboration with the Sourasky Hospital (Ichilov) as well as led by Dr. Assaf Medi and Dr. Uri Ben-David from the Sackler Faculty of Medicine. The study was published in the prestigious journal Nature Biotechnology.

The researchers explain that CRISPR is an innovative technology for DNA editing - that is, cutting the sequence at a certain point to destroy unwanted segments or alternatively to repair or add desired segments. The technology, which was developed about a decade ago, has already demonstrated impressive effectiveness in the treatment of a variety of diseases - cancer, liver diseases, genetic syndromes and more.

The first experiment using CRISPR technology to treat humans was carried out in 2020 when researchers at the University of Pennsylvania in the USA applied it to T cells - white blood cells that belong to the immune system. The researchers took T cells from a donor, engineered them to express a receptor that recognizes cancer cells and at the same time, using CRISPR, destroyed genes that code for the original receptor - which could cause the T cells to attack the cells of the donor's body.

In the current study, the researchers sought to examine whether, along with the apparent benefit, there may also be an accompanying risk to cutting the genome, and this under the assumption that repair does not always occur, and when it does occur, it is not always perfect.

Dr. Ben-David and his research assistant Eli Reuvani explain: "The genome in the cells of each one of us breaks often naturally, and usually knows how to repair itself. However, it sometimes happens that a certain chromosome fails to recover, and large parts of it, or even the entire chromosome, are lost. Such chromosomal changes can destabilize the genome - and we often see this phenomenon in cancer cells. In the case of using CRISPR technology, this means that a procedure designed to treat cancer may, in an extreme scenario, itself cause the creation of a cancerous tumor."

To examine the extent of the damage caused by the technology, the researchers repeated the operations carried out in the experiment in Pennsylvania - and cut the genome of T cells in exactly the same place and in the same way - on chromosomes numbered 2, 7, and 14 (of the 23 pairs of chromosomes that make up the human genome). Then they performed a separate analysis for each cell, in a procedure known as RNA sequencing at the single cell level, and measured the expression level of each chromosome in each of the cells.

In some cells, a significant loss of genetic material was detected in this way. For example, after CRISPR cutting was performed on chromosome 14, it was found that it is almost not expressed in about 5% of the cells. When all three chromosomes were cut at the same time, the rate of damage increased: approximately 9% of the cells did not repair the damage to chromosome 14, 10% did not repair the damage to chromosome 7, and 3% did not repair the break to chromosome 2. However, the extent of the damage in each of the chromosomes was different.

Dr. Medi and his student Ella Goldschmidt explain: "RNA sequencing at the single cell level and the computational analysis made this precise identification possible, and the reason for the difference is the location of the cut on the surface of the chromosome. In total, the study revealed that more than 9% of the T cells that underwent genetic editing using CRISPR technology lost a significant amount of genetic material as a result. This could mean the loss of genomic stability, a phenomenon that can cause cancer."

Following their findings, the researchers recommend caution in using CRISPR technology to develop treatments, and even suggest alternative, less dangerous methods for specific medical procedures. They also recommend focusing research effort on developing solutions in two alternative directions: locating markers on the damaged cells, in order to keep them away from the substance injected into the patient; or developing methods that guarantee in advance the production of fewer damaged cells.

Dr. Barzel and his doctoral student Alessio Nichim conclude: "In this study, we sought to shed light on possible problems and risks in the use of CRISPR technology. And this despite the fact that we are well aware of its benefits, and in other studies we even develop treatments that rely on it. For example, just a short time ago we developed a promising method for treating AIDS that relies on CRISPR, and we even founded companies - one of which uses CRISPR, while the other avoids the use of this technology. That is, on the one hand we promote the technology, and on the other we warn of its dangers. Apparently there is a contradiction in this, but we as scientists are proud of it. This is the essence of science: we do not 'pick sides'. We take an issue and examine it from all sides, positive and negative, and look for answers."

לThe scientific article