Combater o metabolismo nas células cancerígenas: implicações para a terapia do cancro gastrointestinal

Tese de Doutoramento em Ciências da SaúdePara atender às suas necessidades catabólicas e anabólicas, necessárias para manter a homeostasia e a proliferação celular, as células cancerígenas reprogramam o seu metabolismo. Otto Warburg introduziu o conceito de que as células cancerígenas alteram as fontes energéticas para auxiliar a sua proliferação, uma alteração específica dos tumores conhecida como “efeito de Warburg”. Este comportamento confere uma vantagem metabólica às células cancerígenas, uma vez que fornece energia e compostos intermediários necessários à síntese de novos componentes celulares. O metabolismo das células cancerígenas cria também um microambiente tumoral (TME) limitado em nutrientes e imunossupressor, que diminui a capacidade das células imunes de montar uma resposta adequada contra o cancro. Assim, o metabolismo aberrante das células cancerígenas apresenta oportunidades terapêuticas atrativas para combater o cancro. O trabalho apresentado foca-se na compreensão do papel do metabolismo das células cancerígenas na tumorigénese e nos benefícios terapêuticos em inibir proteínas-chave nestas vias para superar a resistência à quimioterapia convencional e ao bloqueio de checkpoints imunológicos (ICB). Neste sentido, investigamos o papel dos transportadores de monocarboxilatos (MCTs), proteínas responsáveis pelo transporte transmembranar de lactato e protões, na sobrevivência das células do cancro colorretal (CRC) e explorá-los como alvos terapêuticos, isoladamente ou em combinação com 5-fluorouracilo (5-FU). A inibição da atividade ou silenciamento da expressão dos MCTs diminuíram o crescimento celular, inibiram o metabolismo glicolítico e proliferação, aumentaram a morte celular e potenciaram a citotoxicidade do 5-FU nas células de CRC. Na segunda parte desta tese identificamos a citidina desaminase (CDA), uma enzima da via de recuperação das pirimidinas, como um potencial alvo envolvido na falta de resposta ao ICB. A inativação genética e a inibição farmacológica da CDA nas células cancerígenas sensibilizou os tumores de adenocarcinoma ductal pancreático (PDAC) para o ICB e aumentou o recrutamento de células T citotóxicas ativadas e macrófagos associados a tumores do tipo M1 nestes tumores. Em suma, o trabalho apresentado nesta tese contribui para um melhor entendimento do papel do metabolismo das células cancerígena na tumorigénese e resistência à terapia farmacológica.In order to match their catabolic and anabolic requirements, necessary to maintain cellular homeostasis and cell proliferation, cancer cells reprogram their metabolism. Otto Warburg introduced the concept that cancer cells switch their energy sources to support their proliferation, a tumour-specific alteration known as “Warburg effect”. This metabolic behaviour confers a metabolic advantage to cancer cells as it provides energy and intermediates necessary for the synthesis of cell building blocks. The metabolism of cancer cells also creates a nutrient deprived and immunosuppressive tumour microenvironment (TME) that dampens the capacity of immune cells to mount a proper immune response against cancer. Therefore, the aberrant metabolism of cancer cells presents attractive therapeutic opportunities to fight cancer. The work presented here focus on understanding the role of cancer cell metabolism in tumorigenesis and the therapeutic benefits of tackling key players in metabolic pathways to overcome resistance to conventional chemotherapy and immune checkpoint blockade (ICB). Here we investigated the role of monocarboxylate transporters (MCTs), proteins responsible for the transmembrane transport of lactate and protons, in the survival of colorectal cancer (CRC) cells and explored them as therapeutic targets alone, or in combination with 5-fluorouracil (5-FU). MCT activity inhibition or expression silencing decreased cell growth, disrupted the glycolytic metabolism, inhibited proliferation, enhanced cell death and potentiated 5-FU cytotoxicity in CRC cells. In the second part of this thesis we identified cytidine deaminase (CDA), an enzyme of the pyrimidine salvage pathway, as a potential target involved in unresponsiveness to ICB. Genetic inactivation or pharmacological inhibition of CDA in cancer cells sensitized pancreatic ductal adenocarcinoma (PDAC) tumours to ICB and increased the recruitment of activated cytotoxic T cells and M1-like anti-tumour associated macrophages into these tumours. In summary, the work presented in this thesis contributes to our understanding of the role of cancer cell metabolism in tumorigenesis and resistance to pharmacological therapy.The work presented in this thesis was performed at the Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho and VIB-KU Leuven Center for Cancer Biology. The author was supported by the grant SFRH/B0/98002/2013 from Fundacao para a Ciencia e a Tecnologia (FCT). Financial support was provided by the European Research Council (ERC) Consolidator - grant (773208; EU) and by Fonds Wetenschappelijk Onderzoek (FWO) (G0A7419N; Belgium). Project co-financed by ON.2-0 Novo Norte; QREN; FEDER funds through the Operational Programme Competitiveness Factors - COMPETE and National Funds through FCT under the project POCI-01-0145-FEDER-007038; and the project NORTE-01-0145-FEDER-000013, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (FEDER). This work was financed by FCT within the scope of project PTDC/QUIQIN/28662/2017. This work was also supported by the strategic programme UID/BIA/04050/2019 funded by national funds through the FCT I.P