What prompted you to take up this particular topic?
During my doctoral studies, I was offered participation in the OPUS 19 research grant. The topic seemed exceptionally interesting to me due to its application aspect. At the same time, in terms of research, it is a relatively new topic in the world, hence the desire to carry out this research. The research project itself was very broad, so I knew that it was a great opportunity for me to develop.
What is DNA polymerase theta?
In the human body, in every cell there are proteins that are responsible for basic functions that allow us to survive. DNA polymerase theta is one of these proteins. Specifically, it is an enzyme that is responsible for DNA synthesis during its repair. In general, DNA polymerases are a wide group of proteins, or more precisely enzymes that enable DNA synthesis during its repair and replication. Replication, or the basic process that allows DNA to be duplicated, so that then during cell division, this genetic material can be divided into daughter cells. If it were not for the ability to repair DNA, there would probably be so much damage to it that the cell would die. Scientists have discovered that DNA polymerase theta is primarily involved in the process of repairing double-stranded DNA breaks, taking its name from this protein, i.e. polymerase theta-mediated end joining.
Schematic diagram of the process involving DNA polymerase theta
What conclusions have you reached?
These are preliminary studies. In order to actually directly translate into anticancer therapy, a great deal of processes would still have to take place. The studies were conducted mainly on cancer cells, i.e. in vitro. We should then expand the studies in vivo, i.e. on animals, and then conduct clinical trials, already on patients and healthy people. However, from my studies we can already conclude that the combinations of drugs that I used, i.e. DNA polymerase theta inhibitors, together with inhibitors of other proteins involved in DNA repair, i.e. ADP-ribose polymerase (PARP for short) or RAD52, lead to the death of cancer cells. In the scientific world, PARP is a widely studied group of proteins and is already functioning in anticancer therapies, especially in the case of breast and ovarian cancer. The main drawback of this treatment is that cancer cells become resistant to these inhibitors, hence the great interest in DNA polymerase theta inhibitors – it may be a second therapeutic target that will help in the fight against resistance to PARP inhibitors. In my studies, I used a combination of these drugs along with a chemotherapy agent. For glioma, it was temozolomide, and for melanoma, it was dacarbazine. These drugs are routinely used in the chemotherapy treatment of these cancers. Our goal was to study the effect of each of these agents separately and when combined.
It turned out that the combination of two inhibitors kills cancer cells quite effectively, i.e. its effect is statistically significantly higher compared to the use of single drugs in most of the obtained results. Adding a chemotherapeutic to this increases this effect even more. However, importantly, these combinations affect normal, i.e. healthy cells to a much lesser extent. This is the key to precise therapy, which would target only cancers and not harm healthy tissues in the human body. This could become a real anti-cancer therapy for patients.
The effect of the DNA polymerase theta inhibitor (ART558), PARP inhibitor (BMN), RAD52 inhibitor (L-OH-DOPA), cytotoxic compound temozolomide (TMZ) and their combination on glioma cells (GBM21) and normal cells (NHA) observed under fluorescence microscope using double staining with Propidium Iodide and Calcein AM. Viable cells are stained in green and cells with impaired cell membrane integrity are stained in red
Is there a possibility of implementing your discoveries in cancer treatment?
DNA polymerase theta inhibitors are already used in clinical trials as compounds with anticancer potential, so this also shows a practical aspect and a chance to enter real anticancer therapy. My research, perhaps indirectly, has a chance to enter the practice of cancer treatment. I am happy about this because it contributes to expanding knowledge in this field. To my knowledge, we are the first team to study the use of these inhibitors in the treatment of brain and skin cancers. There are no such publications, at least publicly available, and this is certainly something new.
While carrying out your research, you cooperated with various external centres. What did this cooperation look like?
We cooperated with three units of the Medical University: the Department of Medical Biochemistry, headed by Prof. Janusz Szemraj, where part of the research was carried out, the Clinic of Neurosurgery and Peripheral Nerve Surgery, which provided us with glioma material for research, and the Department of Oncological Surgery, which provided us with melanoma material. In turn, Dr Grażyna Hoser from the Department of Translational Immunology and Experimental Intensive Therapy of the Centre of Postgraduate Medical Education in Warsaw supported us substantively and performed in vivo studies together with us.
The cooperation with Prof. Tomasz Skorski from the Department of Microbiology and Immunology and Fels Institute for Cancer Research and Molecular Biology Lewis Katz School of Medicine from Temple University of Philadelphia in the United States was also of a content-related nature. Prof. Skorski is a specialist in this topic and was a source of knowledge and valuable, latest information for us.
Will the research you conducted for your doctoral dissertation be continued in any way?
There are such plans. Initially, it is known that the continuation will be an extension of exactly the same studies, but on pancreatic cancer, which is difficult to treat and causes high mortality. Therefore, if we could contribute to increasing its curability, it would be very valuable. We would also like to carry out research on the same cancers, but on a larger number of cell lines, i.e. expand the scale of the research, to further confirm the obtained results. As we know, each patient is a bit different. Another plan for continuation is a grant, for which we are preparing an application. This would allow for financing the extension of the research to include other factors that could contribute to better understanding of the mechanism of action of DNA polymerase theta and the entire therapy. This research involves a large financial outlay and grants from the National Science Centre are an excellent source of support.
What are your plans after defending your doctoral dissertation?
I would like to stay as close to science as possible, and I am looking for a job in pharmaceutical companies. It is very important that you can use the knowledge you gain at university to have a real impact on the development of drugs and therapies, as well as on the shape of conducting commercial research, which later reaches patients.
Thank you for the interview. We hope that the research you are conducting will really contribute to increasing the effectiveness of cancer treatment.
Dr inż. Gabriela Barszczewska-Pietraszek completed her doctoral studies at the Full-time Doctoral School of Molecular Genetics, Cytogenetics and Medical Biophysics at the Department of Molecular Genetics, Institute of Biochemistry, Faculty of Biology and Environmental Protection, University of Lodz. She has prepared her doctoral dissertation under the supervision of Prof. dr hab. Tomasz Śliwiński from the Department of Molecular Genetics, Institute of Biochemistry, Faculty of Biology and Environmental Protection, University of Lodz and dr n. biol. Piotr Czarny from the Department of Medical Biochemistry, Medical University of Lodz.
Edit: Kamila Knol-Michałowska, Promotion Centre, Faculty of Biology and Environmental Protection, University of Lodz
Source and figures: Gabriela Barszczewska-Pietraszek, Faculty of Biology and Environmental Protection, University of Lodz