RESUMO
Serine palmitoyltransferase (SPT) predominantly incorporates serine and fatty acyl-CoAs into diverse sphingolipids (SLs) that serve as structural components of membranes and signaling molecules within or amongst cells. However, SPT also uses alanine as a substrate in the contexts of low serine availability, alanine accumulation, or disease-causing mutations in hereditary sensory neuropathy type I, resulting in the synthesis and accumulation of 1-deoxysphingolipids (deoxySLs). These species promote cytotoxicity in neurons and impact diverse cellular phenotypes, including suppression of anchorage-independent cancer cell growth. While altered serine and alanine levels can promote 1-deoxySL synthesis, they impact numerous other metabolic pathways important for cancer cells. Here, we combined isotope tracing, quantitative metabolomics, and functional studies to better understand the mechanistic drivers of 1-deoxySL toxicity in cancer cells. We determined that both alanine treatment and SPTLC1C133W expression induce 1-deoxy(dihydro)ceramide synthesis and accumulation but fail to broadly impact intermediary metabolism, abundances of other lipids, or growth of adherent cells. However, we found that spheroid culture and soft agar colony formation were compromised when endogenous 1-deoxySL synthesis was induced via SPTLC1C133W expression. Consistent with these impacts on anchorage-independent cell growth, we observed that 1-deoxySL synthesis reduced plasma membrane endocytosis. These results highlight a potential role for SPT promiscuity in linking altered amino acid metabolism to plasma membrane endocytosis.
Assuntos
Neoplasias , Serina C-Palmitoiltransferase , Serina C-Palmitoiltransferase/metabolismo , Ágar/metabolismo , Esfingolipídeos/metabolismo , Serina/química , Ceramidas/metabolismo , Alanina/metabolismo , Membrana Celular/metabolismo , Redes e Vias Metabólicas , Endocitose , Neoplasias/metabolismoRESUMO
Despite the clinical benefit of androgen-deprivation therapy (ADT), the majority of patients with advanced prostate cancer (PCa) ultimately develop lethal castration-resistant prostate cancer (CRPC). In this study, we identified thioesterase superfamily member 6 (THEM6) as a marker of ADT resistance in PCa. THEM6 deletion reduces in vivo tumour growth and restores castration sensitivity in orthograft models of CRPC. Mechanistically, we show that the ER membrane-associated protein THEM6 regulates intracellular levels of ether lipids and is essential to trigger the induction of the ER stress response (UPR). Consequently, THEM6 loss in CRPC cells significantly alters ER function, reducing de novo sterol biosynthesis and preventing lipid-mediated activation of ATF4. Finally, we demonstrate that high THEM6 expression is associated with poor survival and correlates with high levels of UPR activation in PCa patients. Altogether, our results highlight THEM6 as a novel driver of therapy resistance in PCa as well as a promising target for the treatment of CRPC.
Assuntos
Antagonistas de Androgênios , Neoplasias de Próstata Resistentes à Castração , Antagonistas de Androgênios/farmacologia , Antagonistas de Androgênios/uso terapêutico , Regulação Neoplásica da Expressão Gênica , Humanos , Metabolismo dos Lipídeos , Masculino , Neoplasias de Próstata Resistentes à Castração/tratamento farmacológico , Neoplasias de Próstata Resistentes à Castração/patologiaRESUMO
Despite the clinical success of Androgen Receptor (AR)-targeted therapies, reactivation of AR signalling remains the main driver of castration-resistant prostate cancer (CRPC) progression. In this study, we perform a comprehensive unbiased characterisation of LNCaP cells chronically exposed to multiple AR inhibitors (ARI). Combined proteomics and metabolomics analyses implicate an acquired metabolic phenotype common in ARI-resistant cells and associated with perturbed glucose and lipid metabolism. To exploit this phenotype, we delineate a subset of proteins consistently associated with ARI resistance and highlight mitochondrial 2,4-dienoyl-CoA reductase (DECR1), an auxiliary enzyme of beta-oxidation, as a clinically relevant biomarker for CRPC. Mechanistically, DECR1 participates in redox homeostasis by controlling the balance between saturated and unsaturated phospholipids. DECR1 knockout induces ER stress and sensitises CRPC cells to ferroptosis. In vivo, DECR1 deletion impairs lipid metabolism and reduces CRPC tumour growth, emphasizing the importance of DECR1 in the development of treatment resistance.
Assuntos
Metabolismo dos Lipídeos , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Neoplasias de Próstata Resistentes à Castração/enzimologia , Antagonistas de Receptores de Andrógenos/administração & dosagem , Progressão da Doença , Homeostase , Humanos , Masculino , Mitocôndrias/enzimologia , Mitocôndrias/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Fosfolipídeos/metabolismo , Próstata/enzimologia , Próstata/metabolismo , Neoplasias de Próstata Resistentes à Castração/tratamento farmacológico , Neoplasias de Próstata Resistentes à Castração/genética , Receptores Androgênicos/genética , Receptores Androgênicos/metabolismoRESUMO
Oncogene activation and loss of tumor suppressor function changes the metabolic activity of cancer cells to drive unrestricted proliferation. Moreover, cancer cells adapt their metabolism to sustain growth and survival when access to oxygen and nutrients is restricted, such as in poorly vascularized tumor areas. We show here that p53-deficient colon cancer cells exposed to tumor-like metabolic stress in spheroid culture activated the mevalonate pathway to promote the synthesis of ubiquinone. This was essential to maintain mitochondrial electron transport for respiration and pyrimidine synthesis in metabolically compromised environments. Induction of mevalonate pathway enzyme expression in the absence of p53 was mediated by accumulation and stabilization of mature SREBP2. Mevalonate pathway inhibition by statins blocked pyrimidine nucleotide biosynthesis and induced oxidative stress and apoptosis in p53-deficient cancer cells in spheroid culture. Moreover, ubiquinone produced by the mevalonate pathway was essential for the growth of p53-deficient tumor organoids. In contrast, inhibition of intestinal hyperproliferation by statins in an Apc/KrasG12D-mutant mouse model was independent of de novo pyrimidine synthesis. Our results highlight the importance of the mevalonate pathway for maintaining mitochondrial electron transfer and biosynthetic activity in cancer cells exposed to metabolic stress. They also demonstrate that the metabolic output of this pathway depends on both genetic and environmental context. SIGNIFICANCE: These findings suggest that p53-deficient cancer cells activate the mevalonate pathway via SREBP2 and promote the synthesis of ubiquinone that plays an essential role in reducing oxidative stress and supports the synthesis of pyrimidine nucleotide.
Assuntos
Ácido Mevalônico/metabolismo , Neoplasias/patologia , Pirimidinas/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 2/metabolismo , Ubiquinona/análogos & derivados , Animais , Apoptose , Linhagem Celular Tumoral , Sobrevivência Celular , Ciclo do Ácido Cítrico/efeitos dos fármacos , Ciclo do Ácido Cítrico/genética , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Mucosa Intestinal/citologia , Mucosa Intestinal/patologia , Camundongos , Camundongos Transgênicos , Neoplasias/genética , Neoplasias/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Estresse Fisiológico , Microambiente Tumoral/genética , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Ubiquinona/metabolismo , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Statins are widely prescribed inhibitors of the mevalonate pathway, acting to lower systemic cholesterol levels. The mevalonate pathway is critical for tumorigenesis and is frequently upregulated in cancer. Nonetheless, reported effects of statins on tumor progression are ambiguous, making it unclear whether statins, alone or in combination, can be used for chemotherapy. Here, using advanced mass spectrometry and isotope tracing, we showed that statins only modestly affected cancer cholesterol homeostasis. Instead, they significantly reduced synthesis and levels of another downstream product, the mitochondrial electron carrier coenzyme Q, both in cultured cancer cells and tumors. This compromised oxidative phosphorylation, causing severe oxidative stress. To compensate, cancer cells upregulated antioxidant metabolic pathways, including reductive carboxylation, proline synthesis, and cystine import. Targeting cystine import with an xCT transporter-lowering MEK inhibitor, in combination with statins, caused profound tumor cell death. Thus, statin-induced ROS production in cancer cells can be exploited in a combinatorial regimen. SIGNIFICANCE: Cancer cells induce specific metabolic pathways to alleviate the increased oxidative stress caused by statin treatment, and targeting one of these pathways synergizes with statins to produce a robust antitumor response.See related commentary by Cordes and Metallo, p. 151.