Glycosylation is a widely occurring and complex modification found on lipids and proteins and is involved in the recognition, signaling and interaction events within the cell and between cells.... Show moreGlycosylation is a widely occurring and complex modification found on lipids and proteins and is involved in the recognition, signaling and interaction events within the cell and between cells. These events based on glycan structures result in adhesion, cell-matrix interaction and immune recognition. Alterations in the glycomic profile are considered a hallmark of various diseases, including cancer where it contributes to the development and progression of cancer, affecting cell-cell communication, cell-matrix interactions, tumor angiogenesis, invasion and metastasis. These functions are governed by different glycans and their terminal structures. In order to further explore these structures with regard to their potential as biomarkers and specific targets for diagnostic applications and therapeutical strategies for various diseases, in-depth glycomic analysis is needed. It is further noted that aberrant glycosylation not only results from the altered expression of glycosyltransferases (GTs) but also from the changed activity of GTs and glycosidases as well as the availability and abundance of sugar nucleotide donors. The aim of the research described in this thesis was to explore the glycomic signatures of colorectal cancer (CRC) in cell lines and tissues as well as of acute myeloid leukemia (AML) cell lines. Show less
Background: Acute myeloid leukemia (AML) is a genetically and phenotypically heterogeneous disease that has been suffering from stagnant survival curves for decades. In the endeavor toward improved... Show moreBackground: Acute myeloid leukemia (AML) is a genetically and phenotypically heterogeneous disease that has been suffering from stagnant survival curves for decades. In the endeavor toward improved diagnosis and treatment, cellular glycosylation has emerged as an interesting focus area in AML. While mechanistic insights are still limited, aberrant glycosylation may affect intracellular signaling pathways of AML blasts, their interactions within the microenvironment, and even promote chemoresistance. Here, we performed a meta-omics study to portray the glycomic landscape of AML, thereby screening for potential subtypes and responsible glyco-regulatory networks. Results: Initially, by integrating comprehensive N-, O-, and glycosphingolipid (GSL)-glycomics of AML cell lines with transcriptomics from public databases, we were able to pinpoint specific glycosyltransferases (GSTs) and upstream transcription factors (TFs) associated with glycan phenotypes. Intriguingly, subtypes M5 and M6, as classified by the French-American-British (FAB) system, emerged with distinct glycomic features such as high (sialyl) Lewis(x/a) ((s)Le(x/a)) and high sialylation, respectively. Exploration of transcriptomics datasets of primary AML cells further substantiated and expanded our findings from cell lines as we observed similar gene expression patterns and regulatory networks that were identified to be involved in shaping AML glycan signatures. Conclusions: Taken together, our data suggest transcriptionally imprinted glycomic signatures of AML, reflecting their differentiation status and FAB classification. This study expands our insights into the emerging field of AML glycosylation and paves the way for studies of FAB class-associated glycan repertoires of AML blasts and their functional implications. Show less
Glycosidases are essential in fundamental biological processes and are responsible for the degradation of most (oligo)saccharides, glycolipids and glycoproteins. Malfunctioning of glycosidases... Show moreGlycosidases are essential in fundamental biological processes and are responsible for the degradation of most (oligo)saccharides, glycolipids and glycoproteins. Malfunctioning of glycosidases causes various complex pathologies in man, for example, lysosomal storage disorders such as Fabry disease and Krabbe disease. Activity-Based Protein Profiling (ABPP) is a powerful technique to selectively analyze functional proteins in their physiological surroundings. Potent and selective activity-based glycosidase probes (ABPs) could help to understand the pathological processes connected with these enzymes. The first part of this Thesis describes the design, synthesis and application of a set of ABPs for retaining α-galactosidases, β-galactosidases, α-mannosidases and β-mannosidases.Several reversible, competitive glycosidase inhibitors have been developed in the past and are employed for therapeutic applications. The second part of this Thesis focuses on the design of functionalized bicycle [4.1.0] heptanes, carba-cyclophellitols, as new potential competitive inhibitors of glycosidases (α-galactosidases, β-galactosidases, α-glucosidases and β-glucosidases) and glycosyltransferases (both galactosyltransferases and glucosyltransferases). Herein a specific substituted carba-cyclophellitol turned out to be highly potent towards Thermotoga maritima TmGH1 β-glucosidase and therefore conformational strain induced through a cyclopropyl unit may be added to the armory of tight-binding inhibitor designs. Show less
