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The role of mitochondrial metabolism in breast cancer aggressive phenotype induced by hypercholesterolemia
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Introdução: Atualmente sabe-se que as células tumorais adotam o metabolismo que melhor satisfaz as suas necessidades energéticas, contrariamente ao previamente estabelecido pelo “efeito Warburg”. As células cancro de mama triplo negativo, em particular, obtêm elevados níveis de ATP através da ß-oxidação. Segundo o trabalho previamente desenvolvido no Sérgio Dias lab, a exposição a LDL favorece a proliferação, migração e perda de adesão de células de cancro de mama triplo negativo (MDA-MD-231) in vitro. Estas células apresentam um aumento da massa mitocondrial, maior produção de ATP e menor produção de lactato, sugerindo a adoção preferencial da respiração mitocondrial. Objetivo: 1) Caracterizar as alterações metabólicas induzidas pela hipercolesterolemia e 2) determinar a sua implicância no fenótipo agressivo das células MDA-MD-231 expostas a LDL-colesterol in vitro. Resultados: As células MDA-MD-231 expostas a LDL apresentam um aumento de gotículas lipídicas (avaliado por marcação com Bodipy) e um incremento da massa mitocondrial (avaliado por Microscopia Eletrónica de Transmissão e marcação com MitoTracker Deep Red). A análise de expressão génica por qPCR revelou um aumento da expressão de genes de complexos da cadeia respiratória (COX5b, ATP5q1 e NDUFB5) e da ß-oxidação (CTP1a), uma diminuição da expressão de genes da síntese lípica (FASN e HMGCOA) e ausência de alterações na expressão de genes da biogénese mitocondrial (PGC-1α, PGC-1β, NRF1 e TFAM). A utilização do inibidor de CPT1a Etomoxir não interfere com a proliferação das células MDA-MB-231 expostas a LDL, mas impacta a sua capacidade migratória. Conclusão: As células MDA-MB-231 expostas ao LDL têm mais mitocôndrias, maior conteúdo de lípidos e a sua alta capacidade migratória encontra-se dependente da ß-oxidação.
Introduction: Cancer cells are no longer thought to obtain all their energy from aerobic glycolysis (Warburg’s effect) and are able to adopt metabolic programs that better fit their needs. Recently, it was shown that metastatic triple negative breast cancer (TNBC) obtains high levels of ATP through fatty acid oxidation (FAO). In Sérgio Dias lab, it was previously shown that LDL-cholesterol exposure promotes TNBC cells (MDA-MB-231) proliferation, migration and loss of adhesion in vitro. LDL exposed cells have increased mitochondrial number, lower lactate production and higher ATP levels, suggesting a preferential adoption of mitochondrial respiration by more aggressive TNBC cells. Objectives: The aim of this study is 1) to characterize the metabolic alterations induced by hypercholesterolemia and 2) to elucidate their requirement for the acquisition of aggressiveness by LDL exposed MDA-MB-231 cells in vitro. Methods/Results: We confirmed the increase in lipid droplets content in LDL exposed MDA-MD-231 cells by Bodipy staining and the increase in mitochondrial mass by MitoTracker Deep Red staining and analysis of Transmission Electron Microscopy imaged sections. By qPCR analysis, we showed that LDL exposed cells have an increased expression of oxidative phosphorylation chain components (COX5b, ATP5q1 and NDUFB5) and the FAO component CPT1a; a decreased expression of lipid synthesis enzymes (FASN and HMGCOA) and no differences in the expression of mitochondrial biogenesis factors (PGC-1α, PGC-1β, NRF1 and TFAM). Additionally, the CPT1a inhibitor Etomoxir does not affect proliferation, but abolishes the increased migratory capacity of LDL exposed MDA-MB-231 cells. Conclusions: LDL exposed MDA-MB-231 cells have more mitochondria, increased lipid droplets content and rely on FAO for the increase migratory capability.
Introduction: Cancer cells are no longer thought to obtain all their energy from aerobic glycolysis (Warburg’s effect) and are able to adopt metabolic programs that better fit their needs. Recently, it was shown that metastatic triple negative breast cancer (TNBC) obtains high levels of ATP through fatty acid oxidation (FAO). In Sérgio Dias lab, it was previously shown that LDL-cholesterol exposure promotes TNBC cells (MDA-MB-231) proliferation, migration and loss of adhesion in vitro. LDL exposed cells have increased mitochondrial number, lower lactate production and higher ATP levels, suggesting a preferential adoption of mitochondrial respiration by more aggressive TNBC cells. Objectives: The aim of this study is 1) to characterize the metabolic alterations induced by hypercholesterolemia and 2) to elucidate their requirement for the acquisition of aggressiveness by LDL exposed MDA-MB-231 cells in vitro. Methods/Results: We confirmed the increase in lipid droplets content in LDL exposed MDA-MD-231 cells by Bodipy staining and the increase in mitochondrial mass by MitoTracker Deep Red staining and analysis of Transmission Electron Microscopy imaged sections. By qPCR analysis, we showed that LDL exposed cells have an increased expression of oxidative phosphorylation chain components (COX5b, ATP5q1 and NDUFB5) and the FAO component CPT1a; a decreased expression of lipid synthesis enzymes (FASN and HMGCOA) and no differences in the expression of mitochondrial biogenesis factors (PGC-1α, PGC-1β, NRF1 and TFAM). Additionally, the CPT1a inhibitor Etomoxir does not affect proliferation, but abolishes the increased migratory capacity of LDL exposed MDA-MB-231 cells. Conclusions: LDL exposed MDA-MB-231 cells have more mitochondria, increased lipid droplets content and rely on FAO for the increase migratory capability.
Descrição
Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2018
Palavras-chave
Cancro da mama Mitocôndria Hipercolesterolémia Oncobiologia