RESUMEN
Ferroptosis is a form of cell death that has received considerable attention not only as a means to eradicate defined tumour entities but also because it provides unforeseen insights into the metabolic adaptation that tumours exploit to counteract phospholipid oxidation1,2. Here, we identify proferroptotic activity of 7-dehydrocholesterol reductase (DHCR7) and an unexpected prosurvival function of its substrate, 7-dehydrocholesterol (7-DHC). Although previous studies suggested that high concentrations of 7-DHC are cytotoxic to developing neurons by favouring lipid peroxidation3, we now show that 7-DHC accumulation confers a robust prosurvival function in cancer cells. Because of its far superior reactivity towards peroxyl radicals, 7-DHC effectively shields (phospho)lipids from autoxidation and subsequent fragmentation. We provide validation in neuroblastoma and Burkitt's lymphoma xenografts where we demonstrate that the accumulation of 7-DHC is capable of inducing a shift towards a ferroptosis-resistant state in these tumours ultimately resulting in a more aggressive phenotype. Conclusively, our findings provide compelling evidence of a yet-unrecognized antiferroptotic activity of 7-DHC as a cell-intrinsic mechanism that could be exploited by cancer cells to escape ferroptosis.
Asunto(s)
Linfoma de Burkitt , Deshidrocolesteroles , Ferroptosis , Neuroblastoma , Animales , Humanos , Linfoma de Burkitt/metabolismo , Linfoma de Burkitt/patología , Supervivencia Celular , Deshidrocolesteroles/metabolismo , Peroxidación de Lípido , Trasplante de Neoplasias , Neuroblastoma/metabolismo , Neuroblastoma/patología , Oxidación-Reducción , Fenotipo , Reproducibilidad de los ResultadosRESUMEN
In homogenous solution, cholesterol autoxidation leads to a mixture of epimers of 5 primary products, whose concentrations vary in the presence/absence of antioxidants, such as vitaminâ E. Two of the products (5α-OOH and 6ß-OOH) undergo Hock fragmentation to yield electrophilic secosterols implicated in disease. Herein, we show that the product distribution is similar in phospholipid bilayers, in that the 7-OOHs are the major products, but the presence/absence of vitaminâ E has no effect on the distribution. Cholesterol 7α-OOH, but not 7ß-OOH, undergoes Hock fragmentation to yield a mixture of unprecedented A-ring cleavage products and 6,7-epoxides. When subjected to typical derivatization conditions, 7α-OOH yields products with essentially indistinguishable chromatographic and spectroscopic features from the previously identified secosterols, casting further doubt on their controversial origin from endogenous O3 .