All viruses encode for at least one viral interferon (IFN) antagonist, which is used to subvert the cellular IFN response, a powerful antiviral innate immune response. Numerous in vitro and in vivo studies have demonstrated that IFN antagonism is crucial for virus survival, suggesting that viral IFN antagonists could represent promising therapeutic targets. This study focuses on Respiratory Syncytial Virus (RSV), an important human pathogen for which there is no vaccine or virus-specific antiviral drug. RSV encodes two IFN antagonists NS1 and NS2, which play a critical role in RSV replication and pathogenicity. We developed a high-throughput screening (HTS) assay to target NS2 via our A549.pr(ISRE)GFP-RSV/NS2 cell-line, which contains a GFP gene under the control of an IFN-stimulated response element (ISRE) to monitor IFN- signalling pathway. NS2 inhibits the IFN-signalling pathway and hence GFP expression in the A549.pr(ISRE)GFP-RSV/NS2 cell-line by mediating STAT2 degradation. Using a HTS approach, we screened 16,000 compounds to identify small molecules that inhibit NS2 function and therefore relinquish the NS2 imposed block to IFN-signalling, leading to restoration of GFP expression. A total of twenty-eight hits were identified; elimination of false positives left eight hits, four of which (AV-14, -16, -18, -19) are the most promising. These four hit compounds have EC₅₀ values in the single μM range and three of them (AV-14, -16, -18) represent a chemically related series with an indole structure. We demonstrated that the hit compounds specifically inhibit the STAT2 degradation function of NS2, not the function of NS1 or unrelated viral IFN antagonists. At the current time, compounds do not restrict RSV replication in vitro, hence hit optimization is required to improve their potency. Nonetheless, these compounds could be used as chemical tools to determine the unknown mechanism by which NS2 mediates STAT2 degradation and tackle fundamental questions about RSV biology.

Motivation: Although various high-throughput technologies provide a lot of valuable information, each of them is giving an insight into different aspects of cellular activity and each has its own limitations. Thus, a complete and systematic understanding of the cellular machinery can be achieved only by a combined analysis of results coming from different approaches. However, methods and tools for integration and analysis of heterogenous biological data still have to be developed. Results: This work presents systemic analysis of basic cellular processes, i.e. cell viability and cell cycle, as well as embryonic stem cell pluripotency and differentiation. These phenomena were studied using several high-throughput technologies, whose combined results were analysed with existing and novel clustering and hit selection algorithms. This thesis also introduces two novel data management and data analysis tools. The first, called DSViewer, is a database application designed for integrating and querying results coming from various genome-wide experiments. The second, named PhenoFam, is an application performing gene set enrichment analysis by employing structural and functional information on families of protein domains as annotation terms. Both programs are accessible through a web interface. Conclusions: Eventually, investigations presented in this work provide the research community with novel and markedly improved repertoire of computational tools and methods that facilitate the systematic analysis of accumulated information obtained from high-throughput studies into novel biological insights.

Les produits naturels (PNs) englobent une énorme diversité chimique qui a conduit à la découverte de médicaments révolutionnaires contre le cancer, contre les maladies infectieuses et contre d'autres maladies. La majorité des médicaments actuellement approuvés sont des dérivés de PNs, où nombre d’entre eux engagent des cibles considérées comme non thérapeutiques. Malgré ces avantages, les PNs posent des problèmes au niveau de l’isolement, de la déréplication, du réapprovisionnement et de la traçabilité chimique. Compte tenu du besoin urgent de découvrir de nouvelles molécules bioactives contre de nouvelles cibles pour tous les types de maladies, des stratégies innovantes sont nécessaires pour revigorer la découverte de médicaments à partir des PNs. Nous avons développé une plateforme utilisant Saccharomyces cerevisiae pour la production hétérologue de molécules similaire aux PNs, appelée « produits naturels synthétiques » (PNSs). Nous avons synthétisé une vaste bibliothèque de gènes impliqués dans la biosynthèse de PNs (GBSs) provenant de plantes, de champignons et de bactéries, pour lesquels leur contenu en GC et leurs codons ont été optimisés pour l’expression dans S. cerevisiae. Ces gènes sont assemblés en chromosomes artificiels de levure pour générer de vastes bibliothèques combinatoires de BSG pour la production de molécules similaires aux PNs. Les bibliothèques de PNSs peuvent être directement criblées contre des microorganismes ou des cibles spécifiques dans des essais à haut débit. J'ai effectué le criblage de bibliothèques de PNSs contre une variété de cibles bactériennes et humaines. L'un de ces criblages a conduit à la découverte de PNSs ayant une activité antimicrobienne contre un groupe de pathogènes cliniquement pertinents. Récemment, certaines équipes scientifiques, dont la nôtre, ont découvert que l'hyperactivation de la protéase mitochondriale humaine CLPP par les composés anticancéreux ONC201 et ONC212, qui sont présentement en phase préclinique, provoque la mort cellulaire par protéolyse mitochondriale incontrôlée. Cependant, j'ai trouvé que ONC201/212 activent également la version bactérienne de ClpP et ils pourraient donc perturber le microbiome. J'ai donc développé des essais génétiques de substitution dans la levure pour les protéases ClpP afin de cribler pour des activateurs plus spécifiques. Ensuite, j'ai adapté mon approche dans la levure pour le criblage d’inhibiteurs de la protéase principale (Mpro) et de l'endoribonucléase (NendoU) de SRAS-CoV-2, afin de répondre au besoin pour des thérapies antivirales efficaces afin de traiter les personnes atteintes de la forme grave de la COVID-19. Enfin, une autre variante de mon approche dans la levure a également été développée pour le criblage de stabilisateurs de l'interaction entre FKBP12 et calcineurine dans le but d'identifier de nouveaux immunosuppresseurs qui présentent moins d'effets secondaires. Le criblage de ces différents essais m’a permis d’identifier des candidats potentiels pour chaque cible. Bien que les tests faits dans la levure soient utilisés dans le contexte de criblages traditionnels, l’utilisation de la plateforme PNS permet d’explorer un espace chimique inaccessible auparavant afin de favoriser la découverte de médicaments, le tout de manières économique, modulable et durable. / Natural products (NPs) encompass enormous chemical diversity, leading to revolutionary medicines in cancer, infectious disease, and other indications. The majority of currently approved drugs are derived from NPs, with many of them engage targets otherwise viewed as undruggable. Despite these advantages, NPs pose problems in isolation, dereplication, resupply and chemical tractability. Given the pressing need to discover bioactive chemical matter against new targets in all disease areas, innovative strategies are required to reinvigorate NP-based drug discovery. We have developed a Saccharomyces cerevisiae platform for heterologous production of NP-like chemical matter, termed Synthetic Natural Products (SynNPs). We synthesized an extensive library of codon- and GC-content optimized NP biosynthetic genes (BSGs) from plants, fungi and bacteria. These genes are then assembled into programmable yeast artificial chromosomes (YAC) to generate vast combinatorial BSG libraries that produce NP-like molecules. SynNP libraries can be directly screened in high-throughput in either cell- or target-based assays. I constructed and screened SynNP libraries in yeast-based surrogate genetic assays against a variety of bacterial and human targets. One of these screens led to the discovery of SynNPs with antimicrobial activity against a panel of clinically relevant pathogens. Recently, we and others discovered that hyperactivation of the human mitochondrial caseinolytic protease proteolytic subunit (CLPP) by the preclinical anti-cancer compounds ONC201 and ONC212 causes cell death by rampant mitochondrial proteolysis. However, I found that ONC201/212 also activates bacterial ClpP and could therefore disrupt the microbiome. I thus developed yeast-based surrogate genetic assays for ClpP proteases to screen for more specific activators. Then, I adapted my yeast-based approach to screen for inhibitors of SARS-CoV-2 main protease (Mpro) and endoribonuclease (NendoU) to address the need for efficacious antiviral therapies to mitigate the COVID-19 pandemic. Finally, I developed another variant of my yeast-based approach to screen for stabilizers of the interaction between FKBP12 and calcineurin to identify novel candidate immunosuppressants. Screens with these various assay formats allowed me to identify candidate hits for each target. In summary, the SynNP platform allows the exploration of new-to-nature NP-like chemical space for drug discovery in a cost-effective, scalable and sustainable manner, and yeast-based surrogate genetic assays can be used to screen both existing chemical libraries and SynNP libraries.

High-throughput drug screening (HTS) in live cells is often a vital part of the preclinical anticancer drug discovery process. So far, two-dimensional (2D) monolayer cell cultures have been the most prevalent model in HTS endeavors. However, 2D cell cultures often fail to recapitulate the complex microenvironments of in vivo tumors. Monolayer cultures are highly proliferative and generally do not contain quiescent cells, thought to be one of the main reasons for the anticancer therapy failure in clinic. Thus, there is a need for in vitro cellular models that would increase predictive value of preclinical research results. The utilization of more complex three-dimensional (3D) cell cultures, such as multicellular tumor spheroids (MCTS), which contain both proliferating and quiescent cells, has therefore been proposed. However, difficult handling and high costs still pose significant hurdles for application of MCTS for HTS. In this work, we aimed to develop novel assays to apply MCTS for HTS and drug evaluation. We also set out to identify cellular processes that could be targeted to selectively eradicate quiescent cancer cells. In Paper I, we developed a novel MCTS-based HTS assay and found that nutrient-deprived and hypoxic cancer cells are selectively vulnerable to treatment with inhibitors of mitochondrial oxidative phosphorylation (OXPHOS). We also identified nitazoxanide, an FDA-approved anthelmintic agent, to act as an OXPHOS inhibitor and to potentiate the effects of standard chemotherapy in vivo. Subsequently, in Paper II we applied the high-throughput gene-expression profiling method for MCTS-based drug screening. This led to discovery that quiescent cells up-regulate the mevalonate pathway upon OXPHOS inhibition and that the combination of OXPHOS inhibitors and mevalonate pathway inhibitors (statins) results in synergistic toxicity in this cell population. In Paper III, we developed a novel spheroid-based drug combination-screening platform and identified a set of molecules that synergize with nitazoxanide to eradicate quiescent cancer cells. Finally, in Paper IV, we applied our MCTS-based methods to evaluate the effects of phosphodiesterase (PDE) inhibitors in PDE3A-expressing cell lines. In summary, this work illustrates how MCTS-based HTS yields potential to reveal and exploit previously unrecognized tumor-specific vulnerabilities. It also underscores the importance of cell culture conditions in preclinical drug discovery endeavors.

Indiana University-Purdue University Indianapolis (IUPUI) / ALDH isoenzymes are known to impact the sensitivity of certain neoplastic cells toward cyclophosphamides and its analogs. Despite its bone marrow toxicity, cyclophos-phamide is still used to treat various recalcitrant forms of cancer. When activated, cyclo-phosphamide forms aldophosphamide that can spontaneously form the toxic phospho-ramide mustard, an alkylating agent unless detoxified by ALDH isozymes to the carbox-yphosphamide metabolite. Prior work has demonstrated that the ALDH1A1 and ALDH3A1 isoenzymes can convert aldophosphamide to carboxyphosphamide. This has also been verified by over expression and siRNA knockdown studies. Selective small molecule inhibitors for these ALDH isoenzymes are not currently available. We hypothe-sized that novel and selective small molecule inhibitors of ALDH3A1 would enhance cancer cells’ sensitivity toward cyclophosphamide. If successful, this approach can widen the therapeutic treatment window for cyclophosphamides; permitting lower effective dos-ing regimens with reduced toxicity. An esterase based absorbance assay was optimized in a high throughput setting and 101, 000 compounds were screened and two new selective inhibitors for ALDH3A1, which have IC50 values of 0.2 µM (CB7) and 16 µM (CB29) were discovered. These two compounds compete for aldehyde binding, which was vali-dated both by kinetic and crystallographic studies. Structure activity relationship dataset has helped us determine the basis of potency and selectivity of these compounds towards ALDH3A1 activity. Our data is further supported by mafosfamide (an analog of cyclo-phosphamide) chemosensitivity data, performed on lung adenocarcinoma (A549) and gli-oblastoma (SF767) cell lines. Overall, I have identified two compounds, which inhibit ALDH3A1’s dehydrogenase activity selectively and increases sensitization of ALDH3A1 positive cells to aldophosphamide and its analogs. This may have the potential in improving chemotherapeutic efficacy of cyclophosphamide as well as to help us understand better the role of ALDH3A1 in cells. Future work will focus on testing these compounds on other cancer cell lines that involve ALDH3A1 expression as a mode of chemoresistance.

Confronted with the global demographic changes and the increasing pressure on modern healthcare system, there has been a surge of developing new technology platforms in the past decades. Droplet microfluidics is a prominent example of such technology platforms, which offers an efficient format for massively parallelized screening of a large number of samples and holds great promise to boost the throughput and reduce the costs of modern biomedical activities. Despite recent achievements, the realization of a compact and generic screening system which is suited for resource-limited settings and point-of-care applications remains elusive. To address the above challenges, the dissertation focuses on the development of a compact multifunctional droplet micro-magnetofluidic system by exploring the advantages of magnetic in-flow detection principles. The methodologies behind a novel technique for biomedical applications, namely, magnetic in-flow cytometry have been put forth, which encompass magnetic indexing schemes, quantitative multiparametric analytics and magnetically-activated sorting. A magnetic indexing scheme is introduced and intrinsic to the magnetofluidic system. Two parameters characteristic of the magnetic signal when detecting magnetically functionalized objects, i.e. signal amplitude and peak width, providing information which is necessary to perform quantitative analysis in the spirit of optical cytometry has been proposed and realized. Magnetically-activated sorting is demonstrated to actively select individual droplets or to purify a population of droplets of interest. Together with the magnetic indexing scheme and multiparametric analytic technique, this functionality synergistically enables controlled synthesis, quality administration and screening of encoded magnetic microcarriers, which is crucial for the practical realization of magnetic suspension arrays technologies. Furthermore, to satisfy the needs of cost-efficient fabrication and high-volume delivery, an approach to fabricate magnetofluidic devices on flexible foils is demonstrated. The resultant device retains high performance of its rigid counterpart and exhibits excellent mechanical properties, which promises long-term stability in practical applications.