Glioblastoma is the most common malignant brain tumour and remains one of the most aggressive and lethal types of cancer, with a median survival of only 12–15 months following diagnosis. Despite the current treatment, which consists of surgical resection followed by combination of radiotherapy and chemotherapy with temozolomide, glioblastoma remains highly challenging due to the location of the tumour, its heterogeneous nature, invasive behavior of cancer cells, and the development of resistance to therapy. In clinical practice, there is a limited number of biomarkers that would enable more accurate prediction of patient survival and monitoring of treatment response; therefore the search for new biomarkers, taking into account the function and interactions of cells within the complex tumour microinvironment, is crucial. Researchers at the National Institute of Biology identified the DAB2 gene as a prognostic biomarker by transcriptome analysis of tumour samples from the Slovenian population of patients with glioblastoma, as its elevated expression in tumours was associated with shorter patient survival. DAB2 is an adaptor protein that, in healthy cells, participates in the process of clathrin-mediated endocytosis and plays an important role in regulating signaling pathways involved in cell proliferation, differentiation, and apoptosis. In this bachelor's thesis, we analyzed the expression of the DAB2 protein in different cell types within the glioblastoma tumour microenvironment using the immunofluorescence method. DAB2 expression was confirmed in immune cells, predominantly in microglia and macrophages. DAB2-positive cells were most frequently present in the perivascular niche, in the immediate vicinity of CD31- and FAP-positive cells, in which DAB2 was not present. DAB2 protein expression was detected in glioblastoma stem cells but was absent in differentiated tumour cells. In the second part of the bachlelor's thesis, we performed a quantitative analysis of DAB2 expression on analyzed samples, in which we observed differences between individual patients and compared mRNA levels with DAB2 protein expression. These results reflect the heterogeneity of glioblastoma and indicate the presence of complex regulatory mechanisms at the transcriptional and post-transcriptional levels that influence the relationship between the amount of mRNA and the amount of expressed protein. The results of this bachelor's thesis provide an important basis for further investigation of the role of the DAB2 protein in glioblastoma biology and its potential as a biomarker and therapeutic target in the treatment of this disease.
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