Kristina Žukauskaitė has defended her thesis entitled "Impact of Gastrointestinal Cancer Therapies on the Gut Microbiome: Findings from Clinical Studies and an In Vitro Modelling" for the degree of Doctor of Science in Biology.
Scientific supervisor: Prof. Dr. Sonata Jarmalaitė (Vilnius University, Natural Sciences, Biology).
Scientific consultant: Dr. Angela Horvath (Medical University of Graz, Austria, Medical and Health Sciences, Medicine).
Composition of the Dissertation Defence Board: Chairperson - Prof. Dr. Eglė Lastauskienė (Vilnius University, Natural Sciences); Dr. Aurelijus Burokas (Vilnius University, Natural Sciences, Biology); Dr. Daiva Dabkevičienė (Vilnius University, Natural Sciences, Biology); Prof. Dr. Barbara Obermayer-Pietsch (Medical University of Graz, Austria, Medical and Health Sciences, Medicine); Prof. Dr. Tomas Poškus (Vilnius University, Medical and Health Sciences, Medicine).
This study analyzes the impact of gastroenterological (GE) cancer treatment on the gut microbiome and introduces a novel in vitro model for investigating microbiome changes. The ultimate goal of this research is to adapt the system to evaluate the effectiveness of probiotics in mitigating the side effects of cancer treatment and reducing the use of animal models.
In the case of colorectal cancer, the study assessed the effects of preoperative mechanical bowel preparation on the microbiome and the risk of postoperative infections. The results showed that both preparation methods had a similar impact on the microbiome, while patients who developed infections exhibited specific post-surgical microbiome alterations, including an increase in Enterococcus faecalis.
The analysis of gastric cancer patients revealed that neoadjuvant chemotherapy did not significantly alter the gut microbiome composition. However, radical gastrectomy led to pronounced microbiome shifts, including the overgrowth of oral bacteria in the gut (oralization). This phenomenon was further investigated using the newly developed in vitro model. The bioreactor-based human gut model enabled the study of the organization’s effects on the microbiome and the efficacy of novel probiotics. The findings demonstrated that the selected probiotics reduced oral bacterial overgrowth in bioreactors containing a human gut microbiome, suggesting their potential to help patients counteract the unwanted oralization effects induced by cancer treatment.
This study is significant from both scientific and practical perspectives – it enhances our understanding of microbiome changes during GE cancer treatment and provides a platform for testing various interventions without relying on animal models.
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| Kristina Žukauskaitė | Prof. dr. Sonata Jarmalaitė, dr. Angela Horvath | Prof. dr. Eglė Lastauskienė |