Non-toxic CAR-T
Therapy with genetically modified lymphocytes with chimeric antigen receptors (CAR-T) is a relatively new and promising direction in cancer immunotherapy. It consists in taking the patient's T cells and injecting them back into the blood after their genetic modification, which gives lymphocytes the ability to recognize and attack cancer cells. This type of therapy is not without drawbacks. The engineering of the patient's T-lymphocytes is time–consuming and expensive, and if successful, changes in the immune system after the introduction of altered cells in most cases lead to the development of serious side effects within a short period of time, such as neurotoxic reactions and "cytokine storm" (cytokine syndrome) - an acute inflammatory reaction accompanied by high fever, respiratory and cardiovascular insufficiency.
Artistic representation of nanoparticles transporting mRNA to T-lymphocytes (blue), allowing cells to express surface receptors that recognize cancer cells (red). Source: Ryan Allen, Second Bay Studios.
The main goal of CAR T therapy is to give the patient's T cells the ability to express chimeric antigenic receptors (CAR) on their surface. These receptors allow T cells to recognize cancer cells as foreign invaders and remove them from the body.
Currently, for modification, T cells are first purified, then their genome is transduced using a viral vector (usually weakened gammaretroviruses or lentiviruses). This engineering method creates T cells that constantly express CAR, and this leads to serious side effects, since they remain active in the patient's body even after the destruction of cancer cells.
Bioengineers Michael Mitchell and Margaret Billingsley from the University of Pennsylvania, in collaboration with one of the pioneers of CAR-T therapy, Carl Jun, have developed a new method for creating CAR-T cells using matrix RNA.
The use of mRNA creates T cells with temporary CAR expression. This will allow clinicians to use CAR T-cell therapy in doses sufficient to destroy cancer cells without damaging healthy cells, thereby mitigating side effects.
This approach has not yet been clinically widespread, since the ways of delivering mRNA to T cells are limited. The current standard – the electroporation method, which provides for the perforation of the cell membrane by an electric pulse – is not a promising option, since it is an invasive process that carries a high risk of T-cell death or a decrease in its functionality. Even in the best case, electroporation leads to the death of 50% of cells during the production process. Given the cost, difficulties and risks associated with obtaining T-lymphocytes from a patient, a much less toxic method of mRNA administration is needed, only then will this method become a viable alternative to viral DNA editing.
Therefore, the researchers undertook to find a suitable platform for delivering mRNA through the membrane into T cells in sufficient quantities for their translation into the desired receptor proteins.
Finding a suitable nanoparticle was not easy, since T cells are reluctant to absorb material from the environment. In addition, it was extremely important that the platform included a rare combination – both highly efficient delivery and low cytotoxicity.
Researchers have developed ionizable lipid nanoparticles that are able to safely penetrate cell membranes and release therapeutic mRNA only when it should be released.
This technology of mRNA delivery to T cells can be used not only for CAR-T therapy. The method allows you to create mRNA for various therapeutic receptors very quickly, for this it is enough to simply change the sequence of mRNA.
In in vitro experiments, researchers have shown that nanoparticles generate CAR-T cells that are just as effective in destroying cancer cells as CAR-T cells constructed with viruses - a method currently used in clinical practice.
The next steps will include studies of the effects of this delivery system in vivo, studying the effect of temporary CAR expression on therapeutic efficacy and side effects.
Given the growing potential of RNA therapy, mRNA delivery in the form of lipid nanoparticles will find wide application in T cell engineering, including genetic editing of T cells and modulation of protein expression.
Article by M.Billingsley et al. Ionizable Lipid Nanoparticle Mediated mRNA Delivery for Human CAR T Cell Engineering is published in the journal Nano Letters.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on Penn Engineering: Penn Nanoparticles are Less Toxic to T Cells Engineered for Cancer Immunotherapy