The spindle-assembly checkpoint (SAC) is a safety mechanism which secures accurate chromosome segregation during mitosis. BUB1, a serine/threonine kinase, is one of the proteins involved in this... Show moreThe spindle-assembly checkpoint (SAC) is a safety mechanism which secures accurate chromosome segregation during mitosis. BUB1, a serine/threonine kinase, is one of the proteins involved in this checkpoint and its inhibition is thought to have therapeutic potential for the treatment of cancer. Although the exact role of BUB1 in the SAC remains controversial, inhibition of its kinase function has previously been shown to reduce tumor size in mouse xenograft models when combined with paclitaxel. The research described in this thesis aimed to develop novel BUB1 kinase inhibitors for which high-throughput screening was used as starting point for drug discovery. Medicinal chemistry efforts were performed to improve potency after which the obtained inhibitors were further evaluated in cellular assays. In addition, the development of a cellular BUB1 target engagement assay is described. Hit optimization led to the discovery of two lead compounds with good physicochemical properties, subnanomolar affinity for BUB1, good cellular BUB1 target engagement, acceptable selectivity over other kinases and a favorable in vitro ADME profile. Show less
In this thesis, the researcher developed a nanosystem based on the metallophilic Interaction between cyclometalated complexes. Using this strategy, the researcher achieved efficient photodynamic... Show moreIn this thesis, the researcher developed a nanosystem based on the metallophilic Interaction between cyclometalated complexes. Using this strategy, the researcher achieved efficient photodynamic therapy to several cancers, accompanied by the cell imaging property. Show less
Vitamin A or retinol is essential in embryonic development, the visual cycle and the immune system. Vitamin A is converted to retinoic acid (RA) by aldehyde dehydrogenases (ALDHs). The family of... Show moreVitamin A or retinol is essential in embryonic development, the visual cycle and the immune system. Vitamin A is converted to retinoic acid (RA) by aldehyde dehydrogenases (ALDHs). The family of ALDHs consists of 19 members, three of which (ALDH1A1, ALDH1A2 andALDH1A3) have retinal as their preferred substrate. Due to a lack of selective and potent inhibitors for these enzymes, it is difficult to study their individual contribution to Vitamin A metabolism in biological systems.Therefore an activity-based probe based on the chemical structure of retinal has been synthesized to enable activity-based protein profiling (ABPP) of ALDHs. The probe covalently binds to the catalytic cysteine of ALDH enzymes which can then be visualized on gel or analyzed by proteomics using ligation chemistry.After biological evaluation of the probe this chemical tool has been used to study the influence of individual ALDH enzymes on the mucosal immune system and to determine the ALDH profile of several breast cancer cell lines. Thus showcasing its use to study Vitamin A metabolism in a wide variety of biological settings including but not limited to: immunology, cancer and (cancer) stem cells. Show less
The main goal of the research described in this thesis was the development of new photoactivated chemotherapy (PACT) ruthenium(II) complexes bearing a non-toxic photolabile ligand. We first... Show moreThe main goal of the research described in this thesis was the development of new photoactivated chemotherapy (PACT) ruthenium(II) complexes bearing a non-toxic photolabile ligand. We first investigated whether non-toxic ligands such as L-proline, 2-(methylthio)methylpyridine (mtmp), or 3-(methylthio)propylamine (mtpa), once coordinated to ruthenium(II) complexes, could be photosubstituted upon visible light irradiation. The lipophilicity, and in some cases the strain of the ruthenium(II) complexes, were systematically varied and the effects of such variations on the cytotoxicity of the complexes in the dark and under light irradiation were studied. In the second part, the best ligand candidates (i.e. mtmp and mtpa) were coordinated to cyclometalated ruthenium complexes of the type [Ru(bpy)(phpy)(S,N)]PF6 (bpy = 2,2’-bipyridine and phpy = 2-phenylpyridine), to shift the absorption of the complex to the red region of the spectrum. The photosubstitution properties of these cyclometallated complexes were investigated in detail. The most promising ruthenium complexes were tested in cancer cell monolayers under hypoxic conditions (1% O2) to investigate their mode of action and distinguish between PACT and PDT. Show less
Conventional chemotherapy often suffers from a lack of specificity, affecting both normal and cancer cells. Light-activated drugs provide spatial and temporal control over their activity, providing... Show moreConventional chemotherapy often suffers from a lack of specificity, affecting both normal and cancer cells. Light-activated drugs provide spatial and temporal control over their activity, providing a possible solution for this problem. This dissertation describes the synthesis and biological applications of (blue/green/red) light-activated ruthenium polypyridyl drugs as potential prodrugs against cancer. Show less
The field of transition-metal based chemotherapeutics are dominated by derivatives of cisplatin, but a major downside of these platinum based chemotherapeutics is their lack of selectivity... Show moreThe field of transition-metal based chemotherapeutics are dominated by derivatives of cisplatin, but a major downside of these platinum based chemotherapeutics is their lack of selectivity that leads to undesirable side effects. In this work we present alternative strategies such as light-activation with different transition-metals such as ruthenium and palladium that have the potential to be more selective than cisplatin type of drugs. Show less
Proteasomes are multi-protein, multi-catalytic complexes responsible for the degradation of 80-90% of the proteins inside eukaryotic cells. Proteasomes contain a cylindrical 20S core particle (CP)... Show moreProteasomes are multi-protein, multi-catalytic complexes responsible for the degradation of 80-90% of the proteins inside eukaryotic cells. Proteasomes contain a cylindrical 20S core particle (CP) and one or two 19S regulatory particles (RP). The constitutive proteasome core particle (cCP), which is expressed in all mammalian tissues, contains three catalytically active subunits, namely β1c, β2c and β5c. Lymphoid cells express another proteasome core particle known as the immunoproteasome (iCP). In iCPs, β1c, β2c and β5c are replaced by β1i, β2i and β5i. The research described in this thesis reports on the development of new subunit-selective inhibitors and activity-based probes, on the development of an assay to simultaneously monitor all cCP and iCP catalytic activities and on the development of a method that reports on CP catalytic active subunit composition. The tools that stem from the work described in this thesis can now be used to unravel the role of each individual catalytic subunit in a chemical genetics setting (selective and (near) complete inhibition of each subunit), and to clarify the role of mCPs, in, for instance, antigen presentation and cancer. Furthermore, these tools could possibly serve as leads in the discovery of agents for future treatment of cancer and autoimmune diseases. Show less
Cancer is one of the leading causes of death worldwide. Treatment is hampered by an incomplete understanding of the mechanisms underlying carcinogenesis and, consequently, by the absence of... Show moreCancer is one of the leading causes of death worldwide. Treatment is hampered by an incomplete understanding of the mechanisms underlying carcinogenesis and, consequently, by the absence of therapies to specifically eradicate cancer cells without harming normal, healthy cells. Intriguingly, the avian-virus derived protein apoptin was found to selectively induce apoptosis in transformed and tumor cells, heralding the advent of a new era in cancer treatment. The aim of this thesis was to discover the path followed by apoptin to distinguish between normal and cancer cells, and selectively kill the latter, in order to a) get to the root of the problem that is cancer, and b) provide the knowledge which is necessary to design novel, more selective, more effective, safe anti-tumor therapies. To this end, we identified a number of apoptin-interacting proteins, and studied their roles in tumor-selective apoptin-induced apoptosis. Show less
Inspired by cisplatin, the inorganic drug discovered by Barnett Rosenberg in 1965, the research described in this thesis uses targeting ligands, or ligands varied in a combinatorial fashion, to... Show moreInspired by cisplatin, the inorganic drug discovered by Barnett Rosenberg in 1965, the research described in this thesis uses targeting ligands, or ligands varied in a combinatorial fashion, to find platinum complexes with more specific modes of action. These studies have lead to the development of novel (solid-phase) synthetic methods and to the discovery of several compounds with promising biological properties. Show less
