Project description:The ability of cancer cells to switch phenotype in response to a dynamic intra-tumor microenvironment is a major barrier to effective therapy. In melanoma, down-regulation of the lineage addiction oncogene MITF (Microphthalmia-associated transcription factor) is a hallmark of the proliferative-to-invasive phenotype switch. Yet how MITF promotes proliferation and suppresses invasion is poorly understood. Here we show that expression of the key lipogenic enzyme stearoyl-CoA desaturase (SCD) is activated by MITF, but suppressed by the stress-responsive transcription factor ATF4. SCD expression is required for MITF-positive melanoma cell proliferation,. By contrast, MITF-low cells express reduced levels of SCD and are insensitive to its inhibition, indicating that cell phenotype dictates response to drugs targeting lipid metabolism. Since SCD suppresses inflammatory signalling and ATF4 expression, the results identify a positive feedback-loop that can maintain an invasive phenotype, uncover a key role for MITF and ATF4 in metabolic reprograming, and reveal fatty acid composition as a driver of melanoma phenotype-switching.
Project description:Phenotypic and metabolic heterogeneity within tumors is a major barrier to effective cancer therapy. Yet how metabolism is implicated in specific phenotypes, and whether lineage-restricted mechanisms control key metabolic vulnerabilities remains poorly understood. In melanoma, down-regulation of the lineage addiction oncogene Microphthalmia-associated Transcription Factor (MITF) is a hallmark of the proliferative-to-invasive phenotype switch, though how MITF promotes proliferation and suppresses invasion is poorly defined. Here we show that MITF is a lineage restricted activator of the key lipogenic enzyme stearoyl-CoA desaturase (SCD), and that SCD is required for MITFHigh melanoma cell proliferation. By contrast MITFLow cells are insensitive to SCD inhibition. Significantly, the MITF-SCD axis suppresses metastasis, inflammatory signalling, and an ATF4-mediated feedback-loop that maintains dedifferentiation. Our results reveal that MITF is a lineagespecific regulator of metabolic reprogramming, whereby fatty acid composition is a driver of melanoma phenotype-switching, and highlight that cell phenotype dictates response to drugs targeting lipid metabolism.
Project description:Stearoyl-CoA desaturase (SCD) is the rate-limiting enzyme catalyzing the conversion of saturated fatty acids palmitate and stearate to monounsaturated fatty acids palmitoleate and oleate. During adipocyte differentiation, SCD expression increases concomitantly with several transcription factors and lipogenic genes. We used microarrays to examine gene expression in differentiated pre-adipocytes treated with and without an SCD inhibitor. On day 7 of adipocyte differentiation, total RNA was extracted from adipocytes. Two conditions were selected for comparison: total RNA extracted from adipocytes treated with DMSO (control) and or a SCD inhibitor.
Project description:The impact of various fatty acid types on adaptive immunity remains uncertain, and their roles remain unelucidated. In this study, we showed that the enzyme stearoyl-CoA desaturase-1 (Scd-1) and its resulting compound, oleic acid (OA), have a substantial impact on the transformation of CD8+ naïve T cells into effector T cells. Inactivation of Scd-1 triggers the specialization of CD8+ T cells into the Teff subset, enhancing the effector function and mitochondrial metabolism of Teff cells, and OA can partially counteract this.
Project description:Stearoyl-CoA desaturase (SCD) is the rate-limiting enzyme catalyzing the conversion of saturated fatty acids palmitate and stearate to monounsaturated fatty acids palmitoleate and oleate. During adipocyte differentiation, SCD expression increases concomitantly with several transcription factors and lipogenic genes. We used microarrays to examine gene expression in differentiated pre-adipocytes treated with and without an SCD inhibitor.
Project description:Early- and late-onset forms of Alzheimer’s disease (AD) share common features that include abnormalities in lipid metabolism, immune response and synaptic function. Of these, the role of lipids remains the least understood. Our study revealed that molecular functions related to Stearoyl-CoA Desaturase (SCD), the rate limiting enzyme in monounsaturated fatty acid synthesis were specifically altered in the hippocampus of 3xTg-AD (a model of early-onset AD). Remarkably, infusion of an SCD inhibitor (SCDi) reversed 40% of altered immune and synapse genes, rescue dendritic spine number and structure, recovered activity-associated immediate-early gene expression and restored learning and memory in 3xTg-AD mice. In addition, we employed single cell RNA sequencing to characterize the cellular landscape of microglia subpopulations within the 3xTg hippocampus and uncovered that SCDi reversed microglial activation and polarization. Together, we show that a single lipid enzyme, SCD, impinges on the core features of AD.
Project description:Early- and late-onset forms of Alzheimer’s disease (AD) share common features that include abnormalities in lipid metabolism, immune response and synaptic function. Of these, the role of lipids remains the least understood. Our study revealed that molecular functions related to Stearoyl-CoA Desaturase (SCD), the rate limiting enzyme in monounsaturated fatty acid synthesis were specifically altered in the hippocampus of 3xTg-AD (a model of early-onset AD). Remarkably, infusion of an SCD inhibitor (SCDi) reversed 40% of altered immune and synapse genes, rescue dendritic spine number and structure, recovered activity-associated immediate-early gene expression and restored learning and memory in 3xTg-AD mice. In addition, we employed single cell RNA sequencing to characterize the cellular landscape of microglia subpopulations within the 3xTg hippocampus and uncovered that SCDi reversed microglial activation and polarization. Together, we show that a single lipid enzyme, SCD, impinges on the core features of AD.
Project description:To understand molecular mechanisms underlying the growth inhibitory ativity of Stearoyl-CoA desaturase-1 (SCD1) inhibitor, we performed microarray analysis using HCT-116 colorectal cancer cells, in which SCD1 was pharmacologically blocked or genetically ablated.
Project description:Cytotoxic stress activates stress-activated kinases, initiates adaptive mechanisms, including the unfolded protein response (UPR) and autophagy, and induces programmed cell death. Fatty acid unsaturation, controlled by stearoyl-CoA desaturase (SCD)1, prevents cytotoxic stress but the mechanisms are diffuse. We found that SCD1 inhibition alters the levels of proteins phosphorylated at tyrosine in fibroblasts. Major regulated proteins were identified following immunoprecipitation using an anti-phospho-tyrosine antibody and subsequent proteomic analysis.
Project description:Immune cells can metabolize fatty acids (FAs) to generate energy. The source of different fatty acid species, and their impacts on humoral immunity remains poorly understood. Here we report that proliferating B cells require increased amount of monounsaturated fatty acids (MUFA) to maintain mitochondrial metabolism and mTOR activity, and to prevent excessive autophagy and endoplasmic reticular (ER) stress. Furthermore, B cell extrinsic Stearoyl-Coa desaturase (SCD) activity generates endogenous MUFA to support early B cell development and germinal center (GC) formation in vivo during immunization and influenza infection. Thus, SCD-mediated MUFA production is critical for humoral immunity.