Sometimes it is all in the tweaking – immunotherapy studies

by Gomolemo Molope

In school, it goes without saying that acquiring excellent marks throughout the year is a goal most students aim to achieve. However, there is a lot more to the honours year than just bagging distinctions and simply calling it a day – or rather one of the longest years. Some lecturers emphasize that this is a year where you get to expand your knowledge by delving into the scientific work which you find most fascinating; while learning some of the most important techniques researchers use to build this body of knowledge. My supervisor on the other hand refers to it as the year of “trial-and-error”. He says it is the year wherein you’ll gain some lab experience that will either make you joyful and proud or that will just make you cry and super stressed. I couldn’t agree with him more, especially while I was standing in the lab repeating an experiment for the fourth time!

I genuinely felt like giving up at that point. But following a series of numerous attempts at the same experiment, I eventually realized that simply adding a slightly higher volume of enzyme to my reaction tubes could have produced the best results. All I needed to do was to tweak the protocol. And much like me, researchers constantly find themselves having to tweak some of their techniques and protocols to produce effective treatments that aim to alleviate numerous diseases. For instance, acute myeloid leukaemia (AML). This blood and bone marrow cancer has limited treatments with high success rates due to their lack of specificity and their association with life-threatening side effects. Additionally, some of the available treatments cannot be administered to AML patients because they lead to graft-vs-host disease. Consequently, specific and more effective treatments still need to be produced to treat this cancer.

Recently, a much greater effort aimed at developing such specific treatments is being made. The latest research has revealed the use of chimeric antigen receptor (CAR) – T cells as an alternative and novel form of cancer therapy, which boosts the immune system to fight cancer. CAR- T cell therapy has shown exceptional success rates compared to conventional treatments as it targets specific antigens which are expressed by cells known to lead to the development of a particular disease. In some cases, researchers genetically modify natural killer (NK) cells as opposed to T-cells due to their cost effectiveness, reduced side effects and longer lifespan. For instance, work done by Albinger (2022) is proof of concept of a treatment which specifically targets AML cells. Essentially, they set out to generate CD33-targeted CAR-modified natural killer (NK) cells. They focused on CD33 because it is a potential antigenic target frequently expressed on leukemic blasts and cells that prompt leukaemia.

In order for Albinger (2022) to achieve their objectives, they first collected AML cells from patients and then isolated primary NK cells from healthy volunteer donors. They then tweaked or rather genetically modified (by lentiviral transduction) primary NK cells to express a second-generation CD33-CAR. In vivo functional studies of CD33-CAR-NK cells in humanized OCI-AML2 xenograft mouse models which reflect physiological conditions of a human host were performed. Qualitative and quantitative analysis using flow cytometry and confocal microscopy were also done.

In the end, their work showed considerable results proving that the use of CD33-CAR-NK cells could be a potential treatment for AML. In vitro experiments, in the OCI-AML2 cell line, showed that the CD33-CAR-NK cells had stronger cytotoxic activity against AML relative to untransduced NK cells. The in vivo experiments where a single dose injection of CD33-CAR-NK was administered showed effectual clearance of leukemic cells and a greater reduction in leukemic burden relative to untreated mice or mice receiving untransduced NK cells. In vivo experiments where multiple doses of CD33-CARNK cells were administered also showed minimized leukemic burden. The confocal microscopy images obtained from some of the experiments showed low GFP-positive leukemic cells and the presence of intact CAR-NK in the bone marrow of CD33-CAR-NK treated mice. Another one of the major observations made from Albinger’s (2022) work was that the use of the single and repetitive doses of CD33-CAR-NK cells in the mice did not cause any noticeable changes in weight, appearance or behaviour. Additionally, no signs of cytokine release syndrome or graft-vs-host disease were observed.

In conclusion, the results prove that CD33-CAR-NK could be a suitable treatment for AML. Moreover, targeted therapies may assist in improving the prognosis of many patients with AML. This form of therapy could also be applied in the treatment of other types of cancer. However, further research about the identification of unique antigens needs to be done to produce more effective targeted therapies while minimizing undesirable side effects in patients.

Albinger N., Pfeifer R., Nitsche M., et al. (2022) Primary CD33-targeting CAR-NK cells for the treatment of acute myeloid leukemia. Blood Cancer J. 12, 61.

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