Terlizzi, Cristina (2022) Modulation of glucose metabolism in oncogene-driven tumors: implications for therapy. [Tesi di dottorato]

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Abstract

Background and rationale: Activation of oncogenes or loss of function of suppressor genes, in addition to induce neoplastic transformation, leads to a reprogramming of glucose metabolism consisting of a shift from oxidative phosphorylation to aerobic glycolysis even in normoxic conditions. A number of evidences indicates that targeting both oncogene signaling and tumor metabolism may affect proliferation and survival of cancer cells. The aim of the present study was to test whether targeting oncogene drivers in Chronic Myeloid Leukemia (CML) and Non-Small cell Lung Cancer (NSCLC) cells can reverse the Warburg effect by reducing glycolysis and upregulating mitochondrial complexes and to test the effects of combined therapy targeting both oncogene drivers and glucose metabolism. Methods: Oncogene drivers such as EGFR, BCR-ABL and MET were selected as targets along with key proteins regulating glucose metabolism. CML and NSCLC cell lines were subjected to oncogene inhibition by treatment with selective Tyrosine Kinase Inhibitors (TKIs) and tested for glycolytic and mitochondrial protein expression along with glucose uptake, lactate production, oxygen consumption rate and extracellular acidification rate. Co-targeting of oncogene drivers and glucose metabolism was performed by silencing Pyruvate Dehydrogenase Kinase 1 (PDK1), that phosphorylates and inactivates the pyruvate dehydrogenase complex (PDHC), followed by exposure to TKIs. Similarly, the simultaneous inhibition of the oncogene driver and ataxia-telangiectasia mutated protein kinase (ATM), that induces glucose-6-phosphate dehydrogenase (G6PDH) activity, was obtained by exposure to TKIs and ATM inhibitor. Then levels of apoptotic markers were evaluated by Western blot analysis in response to combined treatments and cell viability assays were performed to test toxicity. Results: EGFR and BCR-ABL driven cells showed a reduction of glycolysis and an upregulation of oxidative phosphorylation in response to treatment with the selective TKIs. In NSCLC cancer cells, silencing of PDK1 combined with TKI treatment caused a more pronounced effects on glycolysis and oxidative phosphorylation as well as higher levels of apoptotic markers as compared to those observed after single treatment. A similar potentiation effects on apoptotic markers and cell viability was observed in the same cell lines exposed to combined treatment with ATM and EGFR inhibitors. Silencing of ATM along with TKI treatment confirmed the results obtained with the ATM inhibitor. Conclusions: Co-targeting of glucose metabolism and oncogene drivers such as EGFR, BCR-ABL and MET improves tumor response and can be proposed as a suitable strategy for improving the efficacy of TKI treatment.

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