Prostate cancer cells metabolism on the interplay of androgenic regulation and metabolic environment

• Main Author: Cardoso, Henrique José Matos Morão Mingote
• Publication Date: 2020
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10400.6/10316
• topic: Cancro da próstata - Metabolismo - Metabolismo tumoral - Metastização; Cancro da próstata - Diagnóstico; Cancro da próstata - Tratamento; Cancro da próstata - Papel dos androgénios

Prostate Cancer (PCa) is one of the most common cancer in men and represents the fifth leading cause of cancer deaths. In an initial phase of PCa, the so-called androgen-sensitive stage, PCa cells are extremely dependent on androgens actions to survive and proliferate. This condition allows the effectiveness of androgens deprivation therapy (ADT) that reduce the circulating levels of androgens or block their action. The continuous administration of ADT renders PCa cells resistant to treatment, becoming capable of survive and metastasize even in the absence or very low circulating levels of androgens. At this moment, it is reached the stage of castrate-resistant prostate cancer (CRPC), a condition with high mortality rates and treatment limitations. In the last years, a substantial amount of data showed that cancer cells have the ability of reprogramming metabolism to survive and metastasize. Warburg studies were pioneer showing that tumour cells predominantly use glycolysis for obtaining energy, in detriment of oxidative phosphorylation, with the production of high amounts of lactate. These findings opened the door to the metabolic adaptation being considered a hallmark of cancer. Currently, it is accepted that mitochondrial oxidative phosphorylation and glycolysis, support tumour cells survival and growth. Primary PCa cases differ from other cancer types by the fact that is less glycolytic, and the idea that predominantly use fatty acids and glutamine as energy substrates has been gaining consistency. Indeed, glycolysis is only overactivated in more advanced stages of the disease, in CRPC. However, the understanding of how each metabolic pathway sustains PCa cells survival and growth still is incomplete. Besides the recognized functions as the main drivers of PCa survival and growth, androgens have been indicated as metabolic regulators in PCa, modulating glycolysis and cell lipid handling. Nevertheless, there are several issues in the role of androgens controlling PCa metabolism that need to be clarified. Although efforts have been made in recent years to develop new drugs for PCa treatment, namely, for CRPC, they have shown limited duration of clinical and survival benefits. Following the trend observed in other cancer types, treatment approaches targeting metabolism also have been explored in the case of PCa and CRPC. However, there are important knowledge gaps in the understanding of PCa cells metabolism that should be fulfilled to improve its efficacy and to avoid resistance and bypassing metabolic pathways. The main goal of this thesis was to clarify the role androgens and the metabolic environment in shaping PCa metabolism, and how this interplay can affect PCa cell fate. The present thesis first established the PCa cells dependency on the different metabolic pathways (glycolysis, glutaminolysis and lipid metabolism). It was demonstrated that CRPC cells have higher metabolic rates being more glycolytic than the androgen-sensitive cells, especially the PC3 cells, which also showed a higher capacity to oxidize glutamine. Androgen-responsive LNCaP cells displayed a higher capacity for using fatty acids as mitochondrial fuels. These findings allowed to demonstrate a differential dependency and capacity of fuel use between androgen-sensitive and CRPC cells. Next, we determined the relevance of glutaminolysis for PCa cells survival and growth and the effect of androgens in the regulation of glutamine metabolism. Treatment of PCa cells with 5α-dihydrotestosterone (DHT, 10nM) potentiated glutamine metabolism in PCa cells, whereas the inhibition of glutaminase activity diminished cell viability and migration, and increased apoptosis, particularly in the CRPC. Moreover, cotreatment with glutaminase inhibitor BPTES and the anti-androgen bicalutamide had a synergic effect suppressing LNCaP cells viability, which highlights the benefit of co-targeting androgen receptor and glutamine metabolism in PCa treatment. Glutaminolysis inhibition also had an impact on glycolysis and lipid metabolism. The role of androgens in regulating lipid metabolism and the influence of these hormones and LDL-cholesterol modulating PCa cells fate were evaluated. DHT upregulated the expression of fatty acid synthase and carnitine palmitoyltransferase 1A in androgensensitive PCa cells. LDL-cholesterol enrichment increased PCa cells viability, proliferation, and migration dependently on DHT. This in vitro approach supports clinical and epidemiological data linking obesity and cholesterol with PCa, and first implicated androgens in this relationship. Finally, we investigated the effect of different glucose availability on the PCa cells response to therapy. For this purpose, it was used the receptor tyrosine kinase inhibitor imatinib and two cell line models of CRPC. Higher glucose availability improved the effectiveness of imatinib suppressing survival and growth of CRPC cells Moreover, imatinib treatment stimulated the glycolytic metabolism of CRPC cells. Overall, it was showed that hyperglycemia, the main serum alteration in diabetic patients, potentiated the effects of imatinib in CRPC cells, which raises the curiosity about the efficacy of this drug for treatment of castration-resistant diabetic patients. In conclusion, the main findings of this thesis confirmed the crucial actions of androgens in regulating the metabolism of PCa cells. These effects were pivotal for PCa cells obtaining energy and triggered proliferation and metastasis. Another innovative result of the present thesis was the identification of the cholesterol and androgens interplay in inducing survival and invasiveness features of PCa cells. Moreover, this dissertation demonstrated the flexibility of PCa cells using different energy sources and contributed to a better understanding of the role of lipids and glutamine in PCa. The molecular mechanism underlying the metabolic support of cancer cell survival and growth were highlighted. Overall, the information gathered in this thesis supports the metabolic environment and androgens as “co-authors” orchestrating the reprogramming of PCa and cancer development. Further research on this interplay could be a basis for the development of new treatment approaches for PCa.