京都大学 / 新制・課程博士 / 博士(医学) / 甲第25161号 / 医博第5047号 / 京都大学大学院医学研究科医学専攻 / (主査)教授 妹尾 浩, 教授 小川 誠司, 教授 伊藤 能永 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

NK/T-cell lymphoma (NKTCL) and T-cell non-Hodgkin lymphomas ( T-NHL) are highly aggressive lymphomas that lack rationally designed therapies and rely on repurposed chemotherapeutics from other hematological cancers. Histone deacetylases (HDACs) have been targeted in a range of malignancies, including T-cell lymphomas. This study represents exploratory findings of HDAC6 inhibition in NKTCL and T-NHL through a second-generation inhibitor NN-429. With nanomolar in vitro HDAC6 potency and high in vitro and in cellulo selectivity for HDAC6, NN-429 also exhibited long residence time and improved pharmacokinetic properties in contrast to older generation inhibitors. Following unique selective cytotoxicity towards T-NHL and NKTCL, NN-429 demonstrated a synergistic relationship with the clinical agent etoposide and potential synergies with doxorubicin, cytarabine, and SNS-032 in these disease models, opening an avenue for combination treatment strategies.

S100A4 spielt eine zentrale Rolle für die Metastasierung des Dickdarmkrebses. Die Hemmung der S100A4 Expression stellt damit einen vielversprechenden therapeutischen Ansatz dar. Die vorliegende Arbeit präsentiert Niklosamid und Calcimycin als neue Inhibitoren der S100A4 Transkription. In Kolonkarzinomzellen, die mit einem der beiden Inhibitoren behandelt wurden, wurde die S100A4 Expression konzentrations- und zeitabhängig unterdrückt. Des Weiteren war die Zellmigration und -invasion in Abhängigkeit von S100A4 in behandelten Zellen vermindert. Niklosamid und Calcimycin Behandlung verhinderten die Zellproliferation und die Koloniebildung von Kolonkarzinomzellen. Beide Inhibitoren hemmten den konstitutiv aktiven Wnt Pathway von Kolonkarzinomzellen. Calcimycin Behandlung verminderte die Expression von beta-catenin. Niklosamid hemmte die Bildung des beta-catenin/TCF Komplexes und unterband damit die Expression von Wnt Pathway Genen, wie z.B. S100A4. Im Rahmen dieser Arbeit wurde ein in vivo Tiermodell entwickelt, mit dem die S100A4-induzierte Metastasierung mit Hilfe von nicht-invasivem Biolumineszenz Imaging visualisiert werden konnte. In diesem Model konnte gezeigt werden, dass Niklosamid signifikant die S100A4 Expression im Tumor vermindert und damit die Metastasierung hemmt. Des Weiteren zeigt diese Arbeit, dass S100A4 die Expression des Wnt Pathway Antagonisten DKK-1 in Kolonkarzinomzellen hemmt. DKK-1 selbst konnte als endogener Inhibitor der S100A4 Expression identifiziert werden. Zusammenfassend beschreibt die vorliegende Arbeit einen neuen regulativen Mechanismus im Wnt Pathway, der die S100A4 Expression im Kolonkarzinom fördert. Diese Beobachtung verdeutlicht die Notwendigkeit für wirksame S100A4 Inhibitoren, wie Niklosamid und Calcimycin, die das Potenzial haben, in einer klinischen Anwendung die Metastasierung von Kolonkarzinompatienten mit erhöhter S100A4 Expression zu hemmen und damit deren Überlebenschance wesentlich zu verbessern. / S100A4 promotes metastasis in colon cancer patients thereby reducing their five-year survival chances to less than 10%. Consequently, inhibition of S100A4 expression is a promising strategy for anti-metastatic treatment of colon cancer patients. The present study characterizes the small molecules niclosamide and calcimycin as transcriptional inhibitors of S100A4 which reduced S100A4 expression concentration- and time-dependently. Niclosamide and calcimycin treatment restricted cell migration, invasion and wound healing capabilities in a S100A4-specific manner, and inhibited cell proliferation and colony formation of colon cancer cells. Both small molecule inhibitors interfere with the constitutively active Wnt pathway. Targeting β-catenin expression by calcimycin or interfering with the β-catenin/TCF transcription activating complex by niclosamide resulted in reduced Wnt target gene transcription, among them S100A4. The study further presents a human colon cancer xenograft mouse model for monitoring S100A4-induced metastasis formation via non-invasive bioluminescence imaging. Treatment of xenograft mice with niclosamide resulted in a significant reduction of the S100A4 mRNA level in the tumor accompanied by inhibition of metastasis formation. Moreover, this study presents evidence that S100A4 is an inhibitor of DKK-1 expression. In colon cancer cells DKK-1 and S100A4 expression was negatively correlated. Ectopic S100A4 overexpression inhibited DKK-1 expression. Targeting S100A4 via shRNA recovered the repressed DKK-1 expression and vice versa. In summary, the study describes a novel positive feedback loop in the Wnt pathway regulation formed by S100A4 repressing its antagonist DKK-1. This novel mechanism further strengthens the need for S100A4 inhibitors such as niclosamide or calcimycin. Consequently, such small molecules provide immense potential for the treatment of colon cancer patients who are at high risk for S100A4-induced colon cancer metastasis.

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The human body is colonized by more than 100 trillion microbes which make up an essential part of the body and plays a significant role in health. We now know the over use and misuse of broad-spectrum antibiotics can disrupt this microbiome contributing to the onset of disease and runs the risk of promoting antibiotic resistance. With antibiotic research still on the decline, new strategies are greatly needed to combat emerging pathogens while maintaining a healthy microbiome. We therefore set out to present a novel species-selective antimicrobial drug discovery strategy. Disruption of the homeostasis within the oral cavity can trigger the onset of one of the most common bacterial infections, periodontal disease. Even though the oral cavity is one of the most diverse sites on the human body, the Gram-negative colonizer, Porphyromonas gingivalis has long been considered a key player in the initiation of periodontitis, suggesting the potential for novel narrow-spectrum therapeutics. By targeting key pathogens, it may be possible to treat periodontitis while allowing for the recolonization of the beneficial, healthy flora. Therefore, we set out to use P. gingivalis and periodontal disease as a model for pathogen-specific antimicrobial drug discovery. In this study we present a unique approach to predict essential gene targets selective for the periodontal pathogen within the oral environment. Using our knowledge of metabolic networks and essential genes we identified a “druggable” essential target, meso-diaminopimelate dehydrogenase, which is found in a limited number of species. This enzyme, meso-diaminopimelate dehydrogenase from P. gingivalis, was first expressed and purified, then characterized for enzymatic inhibitor screening studies. We then applied a computer-based drug discovery method, combining pharmacophore models, high-throughput virtual screening and molecular docking. Utilizing the ZINC database we virtually screened over 9 million small-molecules to identify several potential target-specific inhibitors. Finally, we used target-based and whole-cell based biochemical screening to assess in vitro activity. We conclude that the establishment of this target and screening strategy provides a framework for the future development of new antimicrobials and drug discovery.

High aerobic glycolytic capacity is correlated with poor prognosis and increased tumour aggressiveness. 6Phosphofructo-1-kinase catalyses the first irreversible step of glycolysis, and is activated by fructose-2,6-bisphosphate, a product of the kinase activity of four bifunctional isoenzymes, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFK-2/FBPase-2:PFKFB1-4). These are potential anti-tumour targets, but their individual and collective role requires further investigation. This thesis had three aims; to validate the PFK-2/FBPase-2 isoenzymes as anti-cancer targets, to investigate the requirement for isoenzyme-specific targeting, and to initiate assay development, enabling future identification of novel inhibitors. A panel of cancer cell lines was examined and PFKFB3 and PFKFB4 were confirmed to be the most strongly induced isoenzymes in hypoxia, regulated by HIF-1α. Basal and hypoxic relative PFKFB3/PFKFB4 expression varied markedly, and three cell lines with varying expression ratios (MCF-7, U87, PC3) were selected for further study. siRNA knockdown of each isoenzyme individually, markedly reduced 2D and 3D cell growth. The effect of PFKFB3 knockdown was consistently more pronounced, particularly in hypoxia. Double PFKFB3/PFKFB4 knockdown was significantly less effective than PFKFB3 knockdown alone. Direct antagonism of PFKFB3 and PFKFB4 on F-2,6-BP concentration was observed, with PFKFB3 exhibiting high kinase activity, as anticipated, and PFKFB4 exhibiting high bisphosphatase activity. The degree of antagonism was dependent on the relative PFKFB3/PFKFB4 expression ratio. Extensive efforts were made to examine the wider metabolic effect of PFKFB3/PFKFB4 on flux towards glycolysis or the pentose phosphate pathway (PPP), including using metabolite, lipid droplet, ¹³C NMR and mass spectrometry assays. No significant change in metabolic flux was detected, the evidence presented therefore suggesting the impact of the antagonistic effects of the isoenzymes on [F-2,6-BP] extends beyond regulation of metabolic flux alone. This study concluded that the most effective therapeutic strategy will be one that involves a PFKFB3-specific inhibitor, preferably hypoxia-targeted. Accordingly, steps were taken to validate and optimise a robust medium-throughput assay system.

L’obésité, le diabète de type 2 et l’athérosclérose sont les principaux problèmes de santé publique affectant les pays développés. Bien que de nombreux traitements soient disponibles contre ces maladies, de nombreux progrès sont encore nécessaire pour le développement de composés plus actif et plus sûr. Mon laboratoire a montré que l’activation du récepteur aux acides biliaires TGR5 par ses ligands entrainait une augmentation de la dépense énergétique et réduisait le niveau des cytokines chez la souris, ce qui pourrait être une nouvelle voie vers le traitement de ces désordres métaboliques. Nous décrivons ici le développement d’un nouvel agoniste synthétique, spécifique et puissant pour TGR5. A partir d’une librairie de 20.000 composés, les composés 50980906, 13008574 et 37525283 ont été caractérisés comme les plus puissants et stables. Le composé 13008574 a montré une réduction significative sur la prise de poids de souris C57BL/6J après un régime alimentaire riche en graisses. Suite à l’activation de TGR5, nous avons observés une augmentation du niveau d'expression des gènes Ucp-1, Dio-2 et Cpt-1 dans le tissu adipeux brun et une augmentation de la clairance du glucose suite à une augmentation de la sécrétion de GLP-1 chez les souris traitées par le composé 13008574. Nous avons également montrés que le composé 13008574 n’a pas d’effet sur les souris TGR5-/- témoignant de sa spécificité. Enfin nous avons par ailleurs confirmé l'effet du composé 13008574 comme agent anti-inflammatoire, avec un effet protecteur face au développement de l'athérosclérose. Notre travail montre ainsi que le développement d’agonistes pour TGR5, puissant et sûr, est possible pour traiter le syndrome métabolique. / Obesity, type 2 diabetes and atherosclerosis, are amongst the main driving factors of a public health crisis that impacts developed countries. Although several drugs are available, there is still a large unmet medical need to find better and safer compounds to treat these diseases. In this context, my host laboratory discovered that activation of the membrane bile acid receptor TGR5 induces energy expenditure and reduces inflammation in mice, which would be beneficial to manage the above–mentioned disorders. INT-777, a semi-synthetic bile acid, is until now, one of the most specific TGR5 ligands. Here, we report the identification of a new synthetic, selective and potent TGR5 agonist. From a screen of 20,000 compounds as potential TGR5 activators, the compounds 50980906, 13008574 and 37525283 were the most potent and stable. In particular, 13008574 induced a significant reduction of body weight gain when C57BL/6J mice were exposed to a high fat diet, paralleled by an increase in the expression levels of Ucp-1, Dio-2 and Cpt-1 in brown adipose tissue. In addition, mice treated with 13008574 displayed improved glucose clearance, consequent to increased GLP-1 secretion. We showed furthermore that the effects of 13008574 were lost in TGR5-/- mice, testifying the specificity of the compound. In addition, 13008574 acts as an anti-inflammatory agent, with a protective effect on atherosclerosis development in LDLr-/- mice treated with a high cholesterol diet. Our work hence shows that potent, selective, and safe TGR5 agonists can be developed to cure the metabolic syndrome.

Nucleic acids have proven to be viable targets for small molecule drugs. While many examples of such drugs are detailed in the literature, only a select few have found practical use in a clinical setting. These currently employed nucleic acid targeting therapies suffer from either debilitating off-target side effects or succumb to a resistance mechanism of the target. The need for new small molecules that target nucleic acids is evident. However, designing a novel drug to bind to DNA or RNA requires a detailed understanding of exactly what binding environments each nucleic acid presents. In an effort to broaden this knowledge, the work presented in this thesis details the binding location and affinity of known and novel nucleic acid binding small molecules with targets ranging from simple RNA secondary structure all the way to the complex structure of ribosomal RNA. Specifically, it is shown that the anthracycline class of antineoplastics prefer to bind at or near mismatch base pairs in both physiologically relevant iron responsive element RNA hairpin constructs as well as DNA hairpin constructs presenting mismatched base pairs. Also characterized in this thesis is a novel class of topoisomerase II / histone deacetylase inhibitor conjugates that display a unique affinity for DNA over RNA. Finally, the novel class of macrolide-peptide conjugates, known as peptolides, are shown to retain potent translation inhibition of the prokaryotic ribosome. The binding pocket of the peptolides, including a crevice previously unreachable by macrolides that extends away from the peptidyl transferase center toward the subunit interface, is confirmed in detail via chemical footprinting of the 70S ribosome. Overall, the identification of a novel binding site for the anthracycline class of drugs and the characterization of the two novel drug designs presented in this thesis will undoubtedly aid in the effort to design and discover new molecules that aim for nucleic acid targets. For example, the anthracycline derivative topoisomerase II / histone deacetylase inhibitor conjugates, with their differential mode of nucleic acid binding, may prove to have a unique side effect profile in a therapeutic application. The peptolide compounds also have the potential to be applied as novel antibiotics as they bind to an area of the prokaryotic ribosome unrelated to known macrolide resistance mutations. Furthermore, as a result of the observation of this thesis work that some peptolides also posses eukaryotic translation inhibition capabilities, they could prove to be useful in preventing the growth of rapidly proliferating eukaryotic cells such as plasmodium, leishmania, or tumor cells. Additionally, different head groups could be utilized in creating new peptolides; for example, an oxazolidinone antibiotic could be employed to sample a different binding area of the ribosome.