Discovery of novel agents for liver cancer therapeutics and characterization of their bioactivities on cellular pathways

Yuluğ, Işık G.
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Bilkent University
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Hepatocellular carcinoma is the second deadliest and fifth most common cancer type worldwide. Due to the limited therapy options, it is crucial to develop novel targeted therapeutic agents that provide better prognosis and enhance life quality of patients. The specific aim of this thesis was to identify and characterize novel compounds with anticancer properties in liver cancer. Three groups of molecules were investigated. First group were cardiac glycosides extracted and purified from Digitalis Ferruginea. Extensive analysis Glycoside Lanatoside C revealed that these molecules induced ROS accumulation in liver cancer cells with differential downstream targets in mesenchymal-like PTENdeficient drug-resistant Mahlavu and epithelial-like PTEN-adequate drug-sensitive Huh7 liver cancer cells. Xenograft models on nude mice also confirmed the anticancer activities of Lanatoside C in vivo with decreased tumor volume and weight. The second group of compounds were novel molecules that contains triazolothiadiazine and triazolothiadiazole scaffold, derived from known NSAIDs (ibuprofen, naproxen and flurbiprofen). Results indicated that SubG1/G1 cell cycle arrest is induced in treated cells. In addition, extensive molecular analysis disclosed oxidative stress induction and COX activity inhibition leading to ASK1 activation and Akt inhibition. The levels of downstream elements GSK3β, β-catenin and CyclinD1 were also altered. Apoptosis was characterized as the cell death mechanism that is triggered by these molecules in liver cancer cells. Novel nucleobase/nucleoside analogues were the third group of molecules explored in this study. 24 of 127 investigated compounds showed significant cytotoxicity during initial screening. 6 molecules were selected for further molecular analysis upon real-time cytotoxicity assay. It was observed that the molecules induced SubG1/G1 cell cycle arrest through Src pathway inhibition. CyclinE-cdk2 complex formation was prevented then the inhibition of Rb leading to a decrease in cell growth and proliferation and induction of apoptosis in liver cancer cells. This thesis disclosed the mode of action of three groups molecules, glycosides are pure examples of drug repurposing. NSAID represent the modified small molecule compounds for novel targets and finally nucleobase analogs are novel compounds as anti metabolites.

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Hepatocellular carcinoma, Cardiac glycoside, NSAIDs, Apoptosis, Nucleobase, Nucleoside, Triazol, Thiadiazine, Drug repurposing, Anticancer
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