Bioenergetic Pathways Research Articles

CHCHD4 (MIA40) and the mitochondrial disulfide relay system.

Mitochondria are pivotal for normal cellular physiology, as they perform a crucial role in diverse cellular functions and processes, including respiration and the regulation of bioenergetic and biosynthetic pathways, as well as regulating cellular signalling and transcriptional networks. In this way, mitochondria are central to the cell's homeostatic machinery, and as such mitochondrial dysfunction underlies the pathology of a diverse range of diseases including mitochondrial disease and cancer. Mitochondrial import pathways and targeting mechanisms provide the means to transport into mitochondria the hundreds of nuclear-encoded mitochondrial proteins that are critical for the organelle's many functions. One such import pathway is the highly evolutionarily conserved disulfide relay system (DRS) within the mitochondrial intermembrane space (IMS), whereby proteins undergo a form of oxidation-dependent protein import. A central component of the DRS is the oxidoreductase coiled-coil-helix-coiled-coil-helix (CHCH) domain-containing protein 4 (CHCHD4, also known as MIA40), the human homologue of yeast Mia40. Here, we summarise the recent advances made to our understanding of the role of CHCHD4 and the DRS in physiology and disease, with a specific focus on the emerging importance of CHCHD4 in regulating the cellular response to low oxygen (hypoxia) and metabolism in cancer.

Pathophysiology of sepsis.

To provide a current overview of sepsis pathophysiology. The emphasis on sepsis pathophysiology has moved away from the pathogen - the initiating factor - and instead is focussed upon the abnormal and exaggerated host response. Instead of targeted eradication of the infection, the host response activates or suppresses multiple downstream pathways, leading to multiple organ dysfunction. Sepsis represents a dysregulated host response to infection leading to organ dysfunction. Here, the pathogen triggers an initial exaggerated inflammatory-immune response that leads to activation or suppression of multiple endothelial, hormonal, bioenergetic, metabolic, immune, and other pathways. These, in turn, produce the circulatory and metabolic perturbations resulting in organ dysfunction. This review will provide an overview of underlying mechanisms and propose that these processes, whereas superficially viewed as dysfunctional, may actually be adaptive/protective in the first instance, though spilling over into maladaptation/harm depending on the magnitude of the host response.

Role of Bladder Cancer Metabolic Reprogramming in the Effectiveness of Immunotherapy.

Simple SummaryUp to 90% of bladder cancers originate from the cells that line the interior of the bladder and are called urothelial carcinomas (UC). Faster growth of UC leads to a higher demand for nutrients and energy than non-malignant cells. UC compensates for this high demand for energy and building blocks by upregulation of different metabolic and bioenergetic pathways, in a process which is known as metabolic reprogramming (MR). However, this MR creates an environment within the tumor that alters immune cells, which in turn reduces the effectiveness of anticancer treatments such as immunotherapy. Here, we review UC MR and its impact on immune cells in UC in order to explore research opportunities that may improve immunotherapy. We discuss the current understanding of UC MR in animal models and summarize clinical trials that are investigating metabolism as a target to enhance immunotherapy in UC patients.Metabolic reprogramming (MR) is an upregulation of biosynthetic and bioenergetic pathways to satisfy increased energy and metabolic building block demands of tumors. This includes glycolytic activity, which deprives the tumor microenvironment (TME) of nutrients while increasing extracellular lactic acid. This inhibits cytotoxic immune activity either via direct metabolic competition between cancer cells and cytotoxic host cells or by the production of immune-suppressive metabolites such as lactate or kynurenine. Since immunotherapy is a major treatment option in patients with metastatic urothelial carcinoma (UC), MR may have profound implications for the success of such therapy. Here, we review how MR impacts host immune response to UC and the impact on immunotherapy response (including checkpoint inhibitors, adaptive T cell therapy, T cell activation, antigen presentation, and changes in the tumor microenvironment). Articles were identified by literature searches on the keywords or references to “UC” and “MR”. We found several promising therapeutic approaches emerging from preclinical models that can circumvent suppressive MR effects on the immune system. A select summary of active clinical trials is provided with examples of possible options to enhance the effectiveness of immunotherapy. In conclusion, the literature suggests manipulating the MR is feasible and may improve immunotherapy effectiveness in UC.

Meta-analysis of gene expression patterns in Down syndrome highlights significant alterations in mitochondrial and bioenergetic pathways

Individuals with Down syndrome (DS) have an extra copy of chromosome 21. Clinical observations and preclinical studies both suggest that DS is associated with altered bioenergetic pathways. Several studies have reported that differentially expressed genes in DS are located not only on chromosome 21 but also on all other chromosomes. Numerous sets of microarray and RNA-seq data are publicly accessible through the Gene Expression Omnibus. We have conducted a meta-analysis on differentially expressed genes between DS and control subjects. Data deposited before July 1, 2020, were identified by using the search terms “Down syndrome” or “trisomy 21” and “human”. Gene expression data were analyzed and normalized for each study. The mixed effect model was used to identify the differentially expressed genes. We conclude that in DS more than 60% of the genes located on chromosome 21 are significantly upregulated and none of them are downregulated. In addition, a significant dysregulation of genes occurs on all other chromosomes as well. Several of the upregulated genes in DS encode for important components of various bioenergetic pathways, for instance PFKL and ACLY. Genes involved in oxidative phosphorylation are mostly downregulated in DS. The gene expression alterations are consistent with the development of significant metabolic disturbances (“pseudohypoxia”) in DS cells, which may explain some of the well-known functional defects (ranging from neuronal dysfunction to reduced exercise tolerance) associated with DS.

Targeting Cancer Metabolism and Current Anti-Cancer Drugs.

Several studies have exploited the metabolic hallmarks that distinguish between normal and cancer cells, aiming at identifying specific targets of anti-cancer drugs. It has become apparent that metabolic flexibility allows cancer cells to survive during high anabolic demand or the depletion of nutrients and oxygen. Cancers can reprogram their metabolism to the microenvironments by increasing aerobic glycolysis to maximize ATP production, increasing glutaminolysis and anabolic pathways to support bioenergetic and biosynthetic demand during rapid proliferation. The increased key regulatory enzymes that support the relevant pathways allow us to design small molecules which can specifically block activities of these enzymes, preventing growth and metastasis of tumors. In this review, we discuss metabolic adaptation in cancers and highlight the crucial metabolic enzymes involved, specifically those involved in aerobic glycolysis, glutaminolysis, de novo fatty acid synthesis, and bioenergetic pathways. Furthermore, we also review the success and the pitfalls of the current anti-cancer drugs which have been applied in pre-clinical and clinical studies.

UCP2 - Taking the heat out of P-glycoprotein?

Cancer cells are highly proliferative, invasive, metastatic and initiate angiogenesis. These activities demand plentiful energy and bountiful stores of anabolic precursors, a situation that puts significant strain on metabolic pathways and necessitates juggling of finite resources. However, the location and erratic structural organisation of tumours means they reside in a nutrient-poor environment. The glycolytic phenotype has evolved in cancer cells to provide a suitable balance between bioenergetic and biosynthetic pathways. Does this adopted strategy also support the overexpression of an ATP-dependent transporter (P-glycoprotein) to maintain resistance against chemotherapy? This article highlights the metabolic adaptations used by cancer cells to maintain both a glycolytic phenotype and sustain the activity of P-glycoprotein. We argue that these cells negotiate an energy precipice to achieve these adaptations. Finally, we advocate the use of compounds that place resistant cells expressing P-glycoprotein under further metabolic strain and how uncoupling protein-2 may provide an ideal target for them.

Modulation of histone deacetylase 2 (HDAC2) drives neuronal gene expression, mitochondrial dynamics and AD pathophysiology in human stem cell derived neurons

AbstractBackgroundHistone deacetylase 2 (HDAC2) is a major HDAC protein in the adult brain and has been shown to regulate many neuronal genes. Aberrant expression of HDAC2 and subsequent dysregulation of neuronal gene expression has been implicated in Alzheimer’s disease (AD) and brain aging. In vitro models of AD and other neurodegenerative disorders using human induced pluripotent stem cells (hiPSCs) are being increasingly utilized and have provided novel insights into disease mechanisms. However, the role of HDAC2 in living, human neurons and how its manipulation in an AD model may affect disease phenotypes has not been investigated.MethodWe used human induced pluripotent stem cells and lentiviral‐mediated manipulation of HDAC2 in hiPSC‐derived neurons to study the effects of increasing or decreasing HDAC2 expression on neuronal mitochondrial gene expression, morphology, and AD phenotypes.ResultIn this study, we show that levels of HDAC2 naturally decrease as hiPSCs are differentiated towards a neuronal lineage and that this suppression of HDAC2 inversely corresponds to an increase in neuronal‐specific isoforms of Endophilin‐B1, a multifunctional protein involved in mitochondrial dynamics. Manipulation of HDAC2 and Endophilin‐B1 using lentiviral approaches shows that knock‐down of HDAC2 or overexpression of Endophilin‐B1 promote mitochondrial elongation in hiPSC‐derived neurons, but HDAC2 knock‐down specifically influences genes regulating neuronal mitochondrial dynamics. We also observe that the endogenous decrease in HDAC2 levels upon neuronal differentiation also correlates with natural increases in neuronal activity and knock‐down of HDAC2 in differentiated neurons increases expression of genes related to neuronal synapses and further increases neuronal firing. Finally, we demonstrate that knock‐down of HDAC2 reduces amyloid beta peptides and the phospho/total Tau ratio in iPSC‐derived neurons.ConclusionCollectively, our study demonstrates that HDAC2 regulates key neuronal functional and bioenergetic pathways in hiPSC‐derived neurons and suggests that HDAC2 may represent a novel therapeutic target for AD.

Mitochondrial Function and Metabolism of Cultured Skeletal Cells.

Measuring cellular metabolism accurately is necessary to understand bioenergetic pathways in cells. The major ATP generating pathways in cells are oxidative phosphorylation and glycolysis. We have recently analyzed and published bioenergetic pathways active in osteoblasts undergoing differentiation in response to various substrates. Based on those studies, here we provide step-by-step procedures to isolate, culture, plate and run a seahorse assay for measuring cellular metabolism. Furthermore, we provide an example of oxygen consumption and extracellular acidification rate traces obtained from MC3T3E1-C4 cells using the XFe96 seahorse analyzer. One of the limitations of studying bioenergetics in bone cells is the current lack of techniques to analyze bioenergetics in vivo in live animals. There are currently techniques that have been developed using third harmonic generation to study osteocytes using three-photon microscopy along with metabolic changes using endogenous two-photon excited fluorescence. However, these sophisticated techniques are not widely available. The relative ease with which one can obtain data pertaining to metabolic parameters using the XF technology makes it a very attractive technique to utilize on a monolayer of adherent cells.

Multiple metabolic changes mediate the response of Caenorhabditis elegans to the complex I inhibitor rotenone

Rotenone, a mitochondrial complex I inhibitor, has been widely used to study the effects of mitochondrial dysfunction on dopaminergic neurons in the context of Parkinson’s disease. Although the deleterious effects of rotenone are well documented, we found that young adult Caenorhabditis elegans showed resistance to 24 and 48 h rotenone exposures. To better understand the response to rotenone in C. elegans, we evaluated mitochondrial bioenergetic parameters after 24 and 48 h exposures to 1 μM or 5 μM rotenone. Results suggested upregulation of mitochondrial complexes II and V following rotenone exposure, without major changes in oxygen consumption or steady-state ATP levels after rotenone treatment at the tested concentrations. We found evidence that the glyoxylate pathway (an alternate pathway not present in higher metazoans) was induced by rotenone exposure; gene expression measurements showed increases in mRNA levels for two complex II subunits and for isocitrate lyase, the key glyoxylate pathway enzyme. Targeted metabolomics analyses showed alterations in the levels of organic acids, amino acids, and acylcarnitines, consistent with the metabolic restructuring of cellular bioenergetic pathways including activation of complex II, the glyoxylate pathway, glycolysis, and fatty acid oxidation. This expanded understanding of how C. elegans responds metabolically to complex I inhibition via multiple bioenergetic adaptations, including the glyoxylate pathway, will be useful in interrogating the effects of mitochondrial and bioenergetic stressors and toxicants.

Bioenergetic and metabolic aberrations in induced pluripotent stem cell-derived cardiomyocytes generated from PRKAG2-mutated, WPW patient

Abstract Introduction Familial hypertrophic cardiomyopathy (HCM) is caused by over 400 mutations affecting mostly key sarcomere components, such as titin and myosin. However, HCM also results from mutations in non-structural genes such as PRKAG2 which is involved directly in a variety of bioenergetic and metabolic pathways. When the metabolic processes fail to work properly or effectively, structural and functional aberrations resulting in cardiac dysfunction can occur. Thus, mutations in the human PRKAG2 gene lead to HCM, autosomal dominant ventricular pre-excitation - Wolff-Parkinson-White syndrome (WPW), a progressive conduction system disease and vacuolar glycogen accumulation in cardiomyocytes. Purpose To investigate the hypothesis that intervening with the bioenergetic and metabolic consequences of the R302Q mutation in the PRKAG2 gene causing inherited cardiomyopathy, will attenuate the cardiac impairments. Methods We generated mutated and isogenic induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CMs) from a WPW patient carrying the R302Q mutation. As additional control, we used healthy volunteers' iPSC-CMs. Bioenergetic (Oxygen Consumption Rate, OCR) and metabolic status were measured using the Seahorse Flux Analyzer and LC-MS, respectively. To decipher the molecular basis underlying the bioenergetic and metabolic deficits, RNA-seq analysis was performed. Results The OCR results demonstrated in PRKAG2-mutated compared to isogenic and healthy iPSC-CMs, a 2-fold increase in maximal respiration rate and a 3.75-fold increase in spare respiratory capacity, while basal OCR parameters were similar in all groups. Importantly, when treated with the AMPK activator metformin (2.5 [mM]), all the abovementioned OCR parameters were similar in the three groups. RNA-seq analysis demonstrated that of the 553 differently expressed genes (DEGs), and of the 99 DEGs mutually differentially expressed, compared to isogenic and healthy cells, the most relevant altered pathways were glycolysis, carbon metabolism, biosynthesis of amino acids, HIF-1 signaling and fructose and mannose metabolism. These findings are consistent with the LC-MS results demonstrating in PRKAG2-mutated versus isogenic and healthy iPSC-CMs, at least a 3-fold decrease in metabolites linked to the abovementioned pathways: butyryl-carnitine, creatine, docosahexaenoic acid, GMP, IMP, myristoyl-carnitine, palmitoyl-carnitine, succinyl-Cys, UMP, UTP, UDP-GlcNAc. Conclusion PRKAG2-mutated iPSC-CMs exhibit bioenergetic and metabolic aberrations, which contribute to the cardiac pathological aspects of WPW syndrome. Importantly, treatment with the AMPK activator metformin eliminated the bioenergetic abnormalities in the mutated cells, while isogenic and healthy control cells remained unaffected. Based on these novel findings, a new therapeutic modality in WPW patients may be considered. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Israel Science Foundation (ISF)

Prostate Cancer Proliferation Is Affected by the Subcellular Localization of MCT2 and Accompanied by Significant Peroxisomal Alterations.

Simple SummaryFatty acid β-oxidation is a dominant bioenergetic pathway in prostate cancer. It has recently been suggested that the specific targeting of monocarboxylate transporter 2 (MCT2) to peroxisomes contributed to an increase in β-oxidation rates and maintenance of the redox balance in prostate cancer cells. Here we provide evidence demonstrating that prostate cancer streamlines peroxisome metabolism by upregulating distinct pathways involved in lipid metabolism. Importantly, we show that the localization of MCT2 at peroxisomes is required for prostate cancer cell proliferation. Our results emphasize the importance of peroxisomes for prostate cancer development and highlight different cellular mechanisms that may be further explored as possible targets for prostate cancer therapy.Reprogramming of lipid metabolism directly contributes to malignant transformation and progression. The increased uptake of circulating lipids, the transfer of fatty acids from stromal adipocytes to cancer cells, the de novo fatty acid synthesis, and the fatty acid oxidation support the central role of lipids in many cancers, including prostate cancer (PCa). Fatty acid β-oxidation is the dominant bioenergetic pathway in PCa and recent evidence suggests that PCa takes advantage of the peroxisome transport machinery to target monocarboxylate transporter 2 (MCT2) to peroxisomes in order to increase β-oxidation rates and maintain the redox balance. Here we show evidence suggesting that PCa streamlines peroxisome metabolism by upregulating distinct pathways involved in lipid metabolism. Moreover, we show that MCT2 is required for PCa cell proliferation and, importantly, that its specific localization at the peroxisomal membranes is essential for this role. Our results highlight the importance of peroxisomes in PCa development and uncover different cellular mechanisms that may be further explored as possible targets for PCa therapy.

Mitochondrial bioenergetics and neurodegeneration: a paso doble.

Mitochondrial bioenergetics and neurodegeneration: a paso doble.

STAT3 deficiency in B cells exacerbates uveitis by promoting expansion of pathogenic lymphocytes and suppressing regulatory B cells (Bregs) and Tregs

STAT3 transcription factor induces differentiation of naïve T cells into Th17 cells and loss of STAT3 in T cell prevents development of CNS autoimmune diseases. However, function of STAT3 in the B lymphocyte subset is not well understood. In this study, we have generated mice lacking STAT3 in CD19+ B cells (CD19-STAT3KO) and investigated intrinsic and extrinsic functions of STAT3 in B cells and its potential role in resistance or pathogenesis of organ-specific autoimmune diseases. We show that STAT3 regulates metabolic mechanisms in B cells with implications for bioenergetic and metabolic pathways that control cellular homeostasis in B cells. Thus, loss of STAT3 in CD19-STAT3KO cells perturbed growth and apoptosis by inducing rapid entry of B cells into the S-phase of the cell cycle, decreasing expression of cyclin-dependent kinase inhibitors and upregulating pro-apoptotic proteins. We further show that the CD19-STAT3KO mice develop severe experimental autoimmune uveitis (EAU), an animal model of human uveitis. Exacerbated uveitis in CD19-STAT3KO mice derived in part from enhanced expression of costimulatory molecules on B cells, marked increase of Th17 responses and increased recruitment of granulocytes into the neuroretina. The enhanced autoimmunity upon deletion of STAT3 in B cells is also recapitulated in experimental autoimmune encephalitis, a mouse model of multiple sclerosis and thus support our conclusion that STAT3 deletion in B cells enhanced inflammation and the effects observed are not model specific. Our data further indicate that STAT3 pathway modulates interactions between B and T cells during EAU resulting in alteration of lymphocyte repertoire by increasing levels of autoreactive pathogenic T cells while suppressing development and/or expansion of immune-suppressive lymphocytes (Bregs and Tregs). Taken together, STAT3 exerts diametrically opposite effects in lymphocytes, with loss of STAT3 in B cells exacerbating uveitis whereas Stat3 deletion in T cells confers protection.

The lncRNA LOC102549805 (U1) modulates neurotoxicity of HIV-1 Tat protein

HIV-1 Tat is a potent neurotoxic protein that is released by HIV-1 infected cells in the brain and perturbs neuronal homeostasis, causing a broad range of neurological disorders in people living with HIV-1. Furthermore, the effects of Tat have been addressed in numerous studies to investigate the molecular events associated with neuronal cells survival and death. Here, we discovered that exposure of rat primary neurons to Tat resulted in the up-regulation of an uncharacterized long non-coding RNA (lncRNA), LOC102549805 (lncRNA-U1). Our observations showed that increased expression of lncRNA-U1 in neurons disrupts bioenergetic pathways by dysregulating homeostasis of Ca2+, mitigating mitochondrial oxygen reduction, and decreasing ATP production, all of which point mitochondrial impairment in neurons via the Tat-mediated lncRNA-U1 induction. These changes were associated with imbalances in autophagy and apoptosis pathways. Additionally, this study showed the ability of Tat to modulate expression of the neuropeptide B/W receptor 1 (NPBWR1) gene via up-regulation of lncRNA-U1. Collectively, our results identified Tat-mediated lncRNA-U1 upregulation resulting in disruption of neuronal homeostasis.

Control of T lymphocyte fate decisions by PI3K signaling.

Virtually all aspects of T and B lymphocyte development, homeostasis, activation, and effector function are impacted by the interaction of their clonally distributed antigen receptors with antigens encountered in their respective environments. Antigen receptors mediate their effects by modulating intracellular signaling pathways that ultimately impinge on the cytoskeleton, bioenergetic pathways, transcription, and translation. Although these signaling pathways are rather well described at this point, especially those steps that are most receptor-proximal, how such pathways contribute to more quantitative aspects of lymphocyte function is still being elucidated. One of the signaling pathways that appears to be involved in this “tuning” process is controlled by the lipid kinase PI3K. Here we review recent key findings regarding both the triggering/enhancement of PI3K signals (via BCAP and ICOS) as well as their regulation (via PIK3IP1 and PHLPP) and how these signals integrate and determine cellular processes. Lymphocytes display tremendous functional plasticity, adjusting their metabolism and gene expression programs to specific conditions depending on their tissue of residence and the nature of the infectious threat to which they are responding. We give an overview of recent findings that have contributed to this model, with a focus on T cells, including what has been learned from patients with gain-of-function mutations in PI3K as well as lessons from cancer immunotherapy approaches.

Abstract P242: Perivascular Adipose Tissue Regulates Endothelial Function And Glucose Disposal Via Leptin Control Of The 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 / NADPH Oxidase 1 Pathways

Our group has previously reported that lack of adipose tissue (lipodystrophy) leads to glucose intolerance and impaired endothelial-dependent vasorelaxation (EDR) via reduced signaling of the adipokine, leptin in the endothelium. However, the identity of the adipose depot responsible for endothelial leptin signaling activation and the underlying mechanism remains ill-defined. Our new data indicate that the perivascular adipose tissue (PVAT) is an important source of leptin. Thus, we hypothesized that leptin specifically derived from PVAT restores EDR and glucose tolerance in a mouse model with global deficiency in adipose tissue (lipodystrophic, BSCL2 -/- ). Restoration of PVAT in BSCL2 -/- mice corrected systemic glycemic status (GTT AUC, BSCL2 -/- + PVAT 635.3 ± 31.28 vs sham 741.6 ± 45.87, p<0.05). Moreover, PVAT transplantation restored EDR locally (abdominal aorta EDR AUC, BSCL2 -/- + PVAT 224.9 ± 23.97 vs 109 ± 19, P<0.05) but not systemically (thoracic aorta EDR AUC, BSCL2 -/- + PVAT 143.8 ± 22.29 vs sham 131.3 ± 11.54, P<0.05), indicating a distinctive paracrine role for PVAT-derived leptin in the vasculature. Concomitantly, we reported that inhibition of endothelial glycolysis, the main bioenergetic pathway of endothelial cells, via inhibition of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a major regulator of the glycolytic pathway, significantly improved endothelial function in both lipodystrophic mice and endothelial leptin receptor (LepR) deficient mice, as leptin does. Also, endothelial cells extracted from aortas of BSCL2 -/- mice showed a trend towards an increase in PFKFB3 mRNA expression compared to WT mice. Moreover, we found that overexpression of PFKFB3 in aortic rings and endothelial cells impaired EDR and increased the ROS generating enzyme, Nox1 expression, respectively. Collectively, our results showed the critical role of PVAT-driven leptin and endothelial leptin receptor signaling in regulating systemic glucose disposal as well as endothelial function via a mechanism that potentially regulates endothelial glycolysis and oxidative stress-mediated via PFKFB3/NOX1.

Pieces of the Complex Puzzle of Cancer Cell Energy Metabolism: An Overview of Energy Metabolism and Alternatives for Targeted Cancer Therapy.

Over the past decades, several advances in cancer cell biology have led to relevant details about a phenomenon called the 'Warburg effect'. Currently, it has been accepted that the Warburg effect is not compatible with all cancer cells, and thus the process of aerobic glycolysis is now challenged by the knowledge of a large number of cells presenting mitochondrial function. The energy metabolism of cancer cells is focused on the bioenergetic and biosynthetic pathways in order to meet the requirements of rapid proliferation. Changes in the metabolism of carbohydrates, amino acids and lipids have already been reported for cancer cells and this might play an important role in cancer progression. To the best of our knowledge, these changes are mainly attributed to genetic reprogramming which leads to the transformation of a healthy into a cancerous cell. Indeed, several enzymes that are highly relevant for cellular energy are targets of oncogenes (e.g. PI3K, HIF1, and Myc) and tumor suppressor proteins (e.g. p53). As a consequence of extensive studies on cancer cell metabolism, some new therapeutic strategies have appeared that aim to interrupt the aberrant metabolism, in addition to influencing genetic reprogramming in cancer cells. In this review, we present an overview of cancer cell metabolism (carbohydrate, amino acid, and lipid), and also describe oncogenes and tumor suppressors that directly affect the metabolism. We also discuss some of the potential therapeutic candidates which have been designed to target and disrupt the main driving forces associated with cancer cell metabolism and proliferation.

Universal free-energy landscape produces efficient and reversible electron bifurcation

For decades, it was unknown how electron-bifurcating systems in nature prevented energy-wasting short-circuiting reactions that have large driving forces, so synthetic electron-bifurcating molecular machines could not be designed and built. The underpinning free-energy landscapes for electron bifurcation were also enigmatic. We predict that a simple and universal free-energy landscape enables electron bifurcation, and we show that it enables high-efficiency bifurcation with limited short-circuiting (the EB scheme). The landscape relies on steep free-energy slopes in the two redox branches to insulate against short-circuiting using an electron occupancy blockade effect, without relying on nuanced changes in the microscopic rate constants for the short-circuiting reactions. The EB scheme thus unifies a body of observations on biological catalysis and energy conversion, and the scheme provides a blueprint to guide future campaigns to establish synthetic electron bifurcation machines.

Abstract 237: DECR1: The rate limiting enzyme of polyunsaturated fatty acid metabolism and a novel therapeutic target in prostate cancer

Abstract Introduction: Fatty acid oxidation (FAO) is the dominant bioenergetic pathway in prostate cancer (PCa). Previous studies have demonstrated efficacy in targeting key FAO enzymes using in vitro and in vivo models of PCa. However, clinical evidence supporting FAO targeting in PCa is lacking. A recent study reported that FAO is upregulated in PCa cells and is essential for cell viability. Here, we demonstrated therapeutic efficacy of targeting FAO in clinical prostate tumors and identified DECR1 as a potential FAO-related survival factor. Methods and Results: To examine the therapeutic efficacy of targeting FAO in a more clinically-relevant setting, patient-derived prostate explants (PDE) were treated with etomoxir (FAO inhibitor). Results showed significant inhibition of cell proliferation (evaluated using Ki67 immunohistochemistry staining) in drug-treated PDE by a mean of 48% (n=13, p<0.05). To identify key targets of FAO in PCa, a meta-analysis was performed using four clinical RNA-sequencing datasets comprising of malignant and matched normal PCa patient tissues. DECR1 – the rate limiting enzyme of polyunsaturated fatty acid (PUFA) oxidation was identified as a robustly overexpressed FAO gene in PCa tissues; its expression is significantly associated with shorter biochemical recurrence-free survival and overall PCa patient survival. Consistent with the vital role of DECR1 in PUFA oxidation, knockdown of DECR1 impaired the cell's capacity to metabolize PUFAs; furthermore, FAO inhibition via DECR1 knockdown is specific to PUFA oxidation. Notably, DECR1 knockdown significantly inhibited PCa cell proliferation, migration, and invasion, and significantly reduced cellular proliferation in tumors. Mechanistically, DECR1 knockdown results in the induction of lipid peroxidation and cell death via ferroptosis in PCa cells. In contrast, overexpression of DECR1 significantly decreased mitochondrial oxidative stress and reduced levels of malondialdehyde. Treatment of PCa cells with ferrostatin successfully rescued PCa cells from death by DECR1 inhibition. Taken together, these data suggest that overexpression of DECR1 may offer PCa cells a survival advantage by protecting the cells from ferroptosis. Conclusion: This study demonstrated for the first time clinically-relevant evidence that targeting FAO is efficacious and provides evidence for the importance of FAO, and specifically PUFA oxidation, in PCa progression. Importantly, this study identified DECR1 as a promising and novel therapeutic target for PCa. Citation Format: Chui Yan Mah, Zeyad D. Nassar, Ingrid J. Burvenich, Swati Irani, Margaret M. Centenera, Max Moldovan, David J. Lynn, Andrew J. Hoy, Johannes V. Swinnen, Lisa M. Butler. DECR1: The rate limiting enzyme of polyunsaturated fatty acid metabolism and a novel therapeutic target in prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 237.

Human DECR1 is an androgen-repressed survival factor that regulates PUFA oxidation to protect prostate tumor cells from ferroptosis.

Fatty acid β-oxidation (FAO) is the main bioenergetic pathway in human prostate cancer (PCa) and a promising novel therapeutic vulnerability. Here we demonstrate therapeutic efficacy of targeting FAO in clinical prostate tumors cultured ex vivo, and identify DECR1, encoding the rate-limiting enzyme for oxidation of polyunsaturated fatty acids (PUFAs), as robustly overexpressed in PCa tissues and associated with shorter relapse-free survival. DECR1 is a negatively-regulated androgen receptor (AR) target gene and, therefore, may promote PCa cell survival and resistance to AR targeting therapeutics. DECR1 knockdown selectively inhibited β-oxidation of PUFAs, inhibited proliferation and migration of PCa cells, including treatment resistant lines, and suppressed tumor cell proliferation and metastasis in mouse xenograft models. Mechanistically, targeting of DECR1 caused cellular accumulation of PUFAs, enhanced mitochondrial oxidative stress and lipid peroxidation, and induced ferroptosis. These findings implicate PUFA oxidation via DECR1 as an unexplored facet of FAO that promotes survival of PCa cells.