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Sonstige Einrichtungen

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    Identifizierung von Zielmolekülen für die innovative Therapie pleuraler Mesotheliome : Untersuchung von Tyrosinkinasen sowie Komponenten der NF2/mTOR- und p14/p16-Signalwege
    (2020) Mönch, Dina; Ott, German
    Malignant pleural mesothelioma is a diffuse growing, rare form of cancer affecting the outer lining of the inner chest wall (pleura). About 90% of the cases are related to a prolonged exposure to asbestos. MPM is difficult to distinguish from other respiratory diseases and is therefore often diagnosed at late stages, when curative surgery is no longer a treatment option. Moreover, radiotherapy and chemotherapy only show limited efficacy, including a less than 5% five year survival rate. Targeting single molecules involved in progression, growth and metastasis with specific inhibitors might be a promising new approach for this tumour entity. However, till date there are no recommendations for targeted therapies in MPM. Although specific inhibitors of mTOR or single kinases suppressed MPM tumor growth in pre-clinical studies, they were not effective in clinical trials. Therefore, there is an urgent need to identify new treatment approaches and targets. The aim of this PhD thesis was to identify new therapeutical targets for the treatment of malignant pleural mesothelioma with special emphasis on the simultaneous inhibition of tyrosine kinases, p14/p16 and NF2/mTOR pathway molecules. Moreover it was focused on molecules within these pathways for which specific inhibitors are already available. One key aspect of this project was to examine mTOR and ALK as potential therapeutic targets, and to determine the efficacy of ALK and mTOR inhibition on tumor cell growth with ALK inhibitor Crizotinib and mTOR inhibitor Rapamycin, in individual and combinatorial treatment. Therefore, an ALK and mTOR co-expressing patient-derived MPM xenograft model was used. Crizotinib alone did not show anti-tumor efficacy whereas combined treatment with Rapamycin enhanced anti-tumor effect of Rapamycin treatment, and lead to a reduction in tumor volume in the MPM xenograft model. Simultaneous inhibition not only suppressed mTOR and ALK pathway transduction but also Rapamycin–induced AKT activation. Combined therapy significantly suppressed cell proliferation and induced autophagy as well as caspase-independent, necrotic cell death compared to the single treatment. Although only 5% of MPM tumors coexpress ALK and mTOR, the results of this study confirm that combined treatment with Rapamycin and Crizotinib can be a therapeutic treatment option in pleural mesothelioma. Further analyses included the investigation of p14/p16 regulator BMI1 as a therapeutic target for the treatment of MPM. Increased BMI1 expression was detected in 81.3% of the MPM patient samples analyzed. Coexpression of BMI1 and mTOR, a prerequisite for combined therapy, was present in 25% of the analyzed cases, as detected by qRT-PCR and IHC. Monotherapy with mTORC1/2 inhibitor INK-128, mTOR/PI3K inhibitor BEZ235 and BMI1 inhibitor PTC-209 resulted in dose-dependent reduction of cell viability in three MPM cell lines tested. Co-treatment with mTOR inhibitors enhanced therapeutic effect of BMI1 inhibition 2-fold (BEZ235) and 10-fold (INK-128) respectively, thus representing an appealing approach for targeted therapy in MPM. The last part of the project aimed to identify new therapeutic targets by genome-wide, array-based CNV- analysis of 42 MPM. Array-based ONCOSCAN technology, especially developed for formalin-fixed and paraffin-embedded tissue, and GISTIC algorithm identified new gains on chromosome 9p22.2, 13q34 and chromosome 19 (19p13.3, 19p13.11 and 19q13.2), which were verified via qPCR and FISH. GISTIC-reanalysis of previously published data sets provided genomic data of 182 MPM tumors in total and was used to identify critical regions for further research on new target genes like oncogenic kinases AKT1, AKT2, MAP3K10 and PTK2 among others. AKT2 and MAP3K10 gene and protein expression was elevated in the tested MPM cohort. Especially AKT isoforms AKT1 and AKT2 represent attractive targets with important therapeutic potential, since pan-AKT inhibitor Ipatasertib is currently being tested in clinical trials for other tumors. In conclusion, the results of this PhD thesis demonstrate the potential for small molecule inhibitors as therapeutic strategies for the treatment of malignant pleural mesothelioma. Moreover, the results of this study suggest that the concurrent inhibition of mTOR, ALK and AKT pathways is a viable therapeutic strategy, as these pathways are frequently simultaneously activated in pleural mesothelioma.