The combination of orlistat, lonidamine and 6-diazo-5-oxo-L-norleucine induces a quiescent energetic phenotype and limits substrate flexibility in colon cancer cells

Cancer upregulates glycolysis, glutaminolysis and lipogenesis, and induces a catabolic state in patients. The concurrent inhibition of both tumor anabolism and host catabolism, and the energetic consequences of such an approach, have not previously been fully investigated. In the present study, CT26.WT murine colon cancer cells were treated with the combination of anti-anabolic drugs orlistat, lonidamine and 6-diazo-5-oxo-L-norleucine (DON; OLD scheme), which are inhibitors of the de novo synthesis of fatty acids, glycolysis and glutaminolysis, respectively. In addition, the effects of OLD scheme sumplemented with the combination of anti-catabolic compounds, namely growth hormone, insulin and indomethacin (GII scheme), were also evaluated. The effects of the compounds used in combination on CT26.WT cell viability, clonogenicity and energetic metabolism were assessed in vitro. The results demonstrated that the anti-anabolic approach reduced cell viability, clonogenicity and cell cycle progression, and increased apoptosis. These effects were associated with decreased oxidative phosphorylation, glycolysis and fuel flexibility. Furthermore, the anti-catabolic scheme, alone or supplemented with anti-anabolic compounds, did not favor tumor growth. These findings indicated that the simultaneous pharmacological inhibition of tumor anabolism and host catabolism exhibits antitumor effects that should be further evaluated.

Metabolic and OXPHOS Activities Quantified by Temporal ex vivo Analysis Display Patient-Specific Metabolic Vulnerabilities in Human Breast Cancers

Research on mitochondrial metabolism and respiration are rapidly developing areas, however, efficient and widely accepted methods for studying these in solid tumors are still missing. Here, we developed a new method without isotope tracing to quantitate time dependent mitochondrial citrate efflux in cell lines and human breast cancer samples. In addition, we studied ADP-activated respiration in both of the sample types using selective permeabilization and showed that metabolic activity and respiration are not equally linked. Three times lower amount of mitochondria in scarcely respiring MDA-MB-231 cells convert pyruvate and glutamate into citrate efflux at 20% higher rate than highly respiring MCF-7 mitochondria do. Surprisingly, analysis of 59 human breast cancers revealed the opposite in clinical samples as aggressive breast cancer subtypes, in comparison to less aggressive subtypes, presented with both higher mitochondrial citrate efflux and higher respiration rate. Additionally, comparison of substrate preference (pyruvate or glutamate) for both mitochondrial citrate efflux and respiration in triple negative breast cancers revealed probable causes for high glutamine dependence in this subtype and reasons why some of these tumors are able to overcome glutaminase inhibition. Our research concludes that the two widely used breast cancer cell lines fail to replicate mitochondrial function as seen in respective human samples. And finally, the easy method described here, where time dependent small molecule metabolism and ADP-activated respiration in solid human cancers are analyzed together, can increase success of translational research and ultimately benefit patients with cancer.

Metabolic modulation during intestinal fibrosis

Intestinal fibrosis is one of the biggest challenges in the therapeutic management of inflammatory bowel diseases (IBD). Patients with Crohn's disease, in particular, suffer from fibrotic complications, which are manifested by the clinical stenosis of the bowel. Although fibrosis is caused by recurrent episodes of inflammation and wound healing, current therapies for IBD do not seem to reduce the incidence of stenosis, suggesting that inflammation-independent mechanisms also contribute to intestinal fibrogenesis. The lack of anti-fibrotic therapies for IBD and the huge burden this complication places on patients has prompted us to redirect inflammation research toward understanding the mechanisms that drive gut fibrosis. Based on data from other fibroproliferative diseases, metabolic modifications are increasingly recognized as pathogenic processes that may generate new therapeutic opportunities. These metabolic alterations result from a switch in the cellular metabolism of activated fibroblasts, which are the key mediator cells of fibrosis. Here, we review the metabolic changes associated with fibrotic disease and summarize the evidence of a metabolic shift during intestinal fibrosis.

Beyond the Warburg Effect: N-Myc Contributes to Metabolic Reprogramming in Cancer Cells

Cancer cells generate large amounts of lactate derived from glucose regardless of the available oxygen level. Cancer cells finely control ATP synthesis by modulating the uptake of substrates and the activity of enzymes involved in aerobic glycolysis (Warburg effect), which enables them to adapt to the tumor microenvironment. However, increasing evidence suggests that mitochondrial metabolism, including the tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS), and glutaminolysis, is paradoxically activated in MYCN-amplified malignancies. Unlike non-amplified cells, MYCN-amplified cancer cells significantly promote OXPHOS-dependent ATP synthesis. Furthermore, tumor cells are differentially dependent on fatty acid β-oxidation (FAO) according to N-Myc status. Therefore, upregulation of FAO-associated enzymes is positively correlated with both N-Myc expression level and poor clinical outcome. This review explores therapeutic strategies targeting cancer stem-like cells for the treatment of tumors associated with MYCN amplification.

Metabolic Reprogramming in CD8+ T Cells During Acute Viral Infections

CD8+ T cells represent one of the most versatile immune cells critical for clearing away viral infections. Due to their important role, CD8+ T cell activation and memory formation during viral infection have been the focus of several studies recently. Although CD8+ T cell activation and memory formation have been associated with metabolic alterations, the molecular understanding behind T cells choosing one type of metabolism over others based on their differentiation stage is still unclear. This review focuses on how the signaling molecules and cellular processes that are characteristic of CD8+ T cell activation and memory formation also play a critical role in selecting specific type of metabolism during viral infections. In addition, we will summarize the epigenetic factors regulating these metabolic alterations.

Deactivation of Glutaminolysis Sensitizes PIK3CA-Mutated Colorectal Cancer Cells to Aspirin-Induced Growth Inhibition

Aspirin is one of the most promising over-the-counter drugs to repurpose for cancer treatment. In particular, aspirin has been reported to be effective against PIK3CA-mutated colorectal cancer (CRC); however, little information is available on how the PIK3CA gene status affects its efficacy. We found that the growth inhibitory effects of aspirin were impaired upon glutamine deprivation in PIK3CA-mutated CRC cells. Notably, glutamine dependency of aspirin-mediated growth inhibition was observed in PIK3CA-mutated cells but not PIK3CA wild type cells. Mechanistically, aspirin induced G1 arrest in PIK3CA-mutated CRC cells and inhibited the mTOR pathway, inducing the same phenotypes as glutamine deprivation. Moreover, our study including bioinformatic approaches revealed that aspirin increased the expression levels of glutaminolysis-related genes with upregulation of activating transcription factor 4 (ATF4) in PIK3CA-mutated CRC cells. Lastly, the agents targeting glutaminolysis demonstrated significant combined effects with aspirin on PIK3CA-mutated CRC cells. Thus, these findings not only suggest the correlation among aspirin efficacy, PIK3CA mutation and glutamine metabolism, but also the rational combinatorial treatments of aspirin with glutaminolysis-targeting agents against PIK3CA-mutated CRC.

Nf1 loss promotes Kras-driven lung adenocarcinoma and results in Psat1-mediated glutamate dependence

Mutations to KRAS are recurrent in lung adenocarcinomas (LUAD) and are daunting to treat due to the difficulties in KRAS oncoprotein inhibition. A possible resolution to this problem may lie with co-mutations to other genes that also occur in KRAS-driven LUAD that may provide alternative therapeutic vulnerabilities. Approximately 3% of KRAS-mutant LUADs carry functional mutations in NF1 gene encoding neurofibromin-1, a negative regulator of focal adhesion kinase 1 (FAK1). We evaluated the impact of Nf1 loss on LUAD development using a CRISPR/Cas9 platform in a murine model of Kras-mutant LUAD We discovered that Nf1 deactivation is associated with Fak1 hyperactivation and phosphoserine aminotransferase 1 (Psat1) upregulation in mice. Nf1 loss also accelerates murine Kras-driven LUAD tumorigenesis. Analysis of the transcriptome and metabolome reveals that LUAD cells with mutation to Nf1 are addicted to glutamine metabolism. We also reveal that this metabolic vulnerability can be leveraged as a treatment option by pharmacologically inhibiting glutaminase and/or Psat1. Lastly, the findings advocate that tumor stratification by co-mutations to KRAS/NF1 highlights the LAUD patient population expected to be susceptible to inhibiting PSAT1.

Non-Coding RNAs as Key Regulators of Glutaminolysis in Cancer

Cancer cells exhibit exacerbated metabolic activity to maintain their accelerated proliferation and microenvironmental adaptation in order to survive under nutrient-deficient conditions. Tumors display an increase in glycolysis, glutaminolysis and fatty acid biosynthesis, which provide their energy source. Glutamine is critical for fundamental cellular processes, where intermediate metabolites produced through glutaminolysis are necessary for the maintenance of mitochondrial metabolism. These include antioxidants to remove reactive oxygen species, and the generation of the nonessential amino acids, purines, pyrimidines and fatty acids required for cellular replication and the activation of cell signaling. Some cancer cells are highly dependent on glutamine consumption since its catabolism provides an anaplerotic pathway to feed the Krebs cycle. Intermediate members of the glutaminolysis pathway have been found to be deregulated in several types of cancers and have been proposed as therapeutic targets and prognostic biomarkers. This review summarizes the main players in the glutaminolysis pathway, how they have been found to be deregulated in cancer and their implications for cancer maintenance. Furthermore, non-coding RNAs are now recognized as new participants in the regulation of glutaminolysis; therefore, their involvement in glutamine metabolism in cancer is discussed in detail.

Differential Alternative Polyadenylation Landscapes Mediate Hematopoietic Stem Cell Activation and Regulate Glutamine Metabolism

Alternative polyadenylation (APA) is emerging as an important regulatory mechanism of RNA and protein isoform expression by controlling 3' untranslated region (3'-UTR) composition. The relevance of APA in stem cell hierarchies remains elusive. Here, we first demonstrate the requirement of the APA regulator Pabpn1 for hematopoietic stem cell (HSC) function. We then determine the genome-wide APA landscape (APAome) of HSCs and progenitors by performing low-input 3' sequencing paired with bioinformatic pipelines. This reveals transcriptome-wide dynamic APA patterns and an overall shortening of 3'-UTRs during differentiation and upon homeostatic or stress-induced transition from quiescence to proliferation. Specifically, we show that APA regulates activation-induced Glutaminase (Gls) isoform switching by Nudt21. This adaptation of the glutamine metabolism by increasing the GAC:KGA isoform ratio fuels versatile metabolic pathways necessary for HSC self-renewal and proper stress response. Our study establishes APA as a critical regulatory layer orchestrating HSC self-renewal, behavior, and commitment.

Consideration of Ketogenic Metabolic Therapy as a Complementary or Alternative Approach for Managing Breast Cancer

Breast cancer remains as a significant cause of morbidity and mortality in women. Ultrastructural and biochemical evidence from breast biopsy tissue and cancer cells shows mitochondrial abnormalities that are incompatible with energy production through oxidative phosphorylation (OxPhos). Consequently, breast cancer, like most cancers, will become more reliant on substrate level phosphorylation (fermentation) than on oxidative phosphorylation (OxPhos) for growth consistent with the mitochondrial metabolic theory of cancer. Glucose and glutamine are the prime fermentable fuels that underlie therapy resistance and drive breast cancer growth through substrate level phosphorylation (SLP) in both the cytoplasm (Warburg effect) and the mitochondria (Q-effect), respectively. Emerging evidence indicates that ketogenic metabolic therapy (KMT) can reduce glucose availability to tumor cells while simultaneously elevating ketone bodies, a non-fermentable metabolic fuel. It is suggested that KMT would be most effective when used together with glutamine targeting. Information is reviewed for suggesting how KMT could reduce systemic inflammation and target tumor cells without causing damage to normal cells. Implementation of KMT in the clinic could improve progression free and overall survival for patients with breast cancer.

Aspirin Mitigated Tumor Growth in Obese Mice Involving Metabolic Inhibition

Obesity is associated with a wide range of chronic diseases, including cancer. It has been noted that the integration of metabolic mechanisms in obese patients may predispose them to suffer from cancer incidence and its progression. Thus, a better understanding of metabolic alterations in obesity, along with the development of feasible therapeutic approaches for intervention, are theoretically relevant to the prevention and treatment of cancer malignancy. Using a syngeneic tumor model involving Lewis Lung Carcinoma (LLC) cells and C57BL/6 mice fed with a high fat diet, obesity was found to be associated with dysregulated glucose and glutamine metabolism, inflammation, along with platelet activation and the promotion of tumor growth. Tumor-bearing lowered glucose levels while moderately increasing inflammation, platelet activation, and glutamine levels. The antiplatelet drug aspirin, mitigated tumor growth in obese mice, paralleled by a decrease in systemic glucose, insulin, inflammation, platelet activation, glutamine and tumor expression of cell proliferation, aerobic glycolysis, glutaminolysis, platelets, and leukocyte molecules. The anti- and pro-cell proliferation, aerobic glycolysis, and glutaminolysis effects of aspirin and glutamine were further demonstrated in a LLC cell study. Although there remains limitations to our experiments, glucose and glutamine metabolism are proposed targets for the anticancer effects of aspirin.

T cell Metabolism in Lupus

Abnormal T cell responses are central to the development of autoimmunity and organ damage in systemic lupus erythematosus. Following stimulation, naïve T cells undergo rapid proliferation, differentiation and cytokine production. Since the initial report, approximately two decades ago, that engagement of CD28 enhances glycolysis but PD-1 and CTLA-4 decrease it, significant information has been generated which has linked metabolic reprogramming with the fate of differentiating T cell in health and autoimmunity. Herein we summarize how defects in mitochondrial dysfunction, oxidative stress, glycolysis, glutaminolysis and lipid metabolism contribute to pro-inflammatory T cell responses in systemic lupus erythematosus and discuss how metabolic defects can be exploited therapeutically.

Hypermetabolism of glutathione, glutamate and ornithine via redox imbalance in methylglyoxal-induced peritoneal injury rats

Peritoneal dialysis (PD) is a blood purification treatment for patients with reduced renal function. However, the peritoneum is exposed to oxidative stress during PD and long-term PD results in peritoneal damage, leading to the termination of PD. Methylglyoxal (MGO) contained in commercial PD fluids is a source of strong oxidative stress. The aim of this study was to clarify the mechanism of MGO-induced peritoneal injury using metabolome analysis in rats. We prepared peritoneal fibrosis rats by intraperitoneal administration of PD fluids containing MGO for 21 days. As a result, MGO-induced excessive proliferation of mesenchymal cells with an accumulation of advanced glycation end-products (AGEs) at the surface of the thickened peritoneum in rats. The effluent levels of methionine sulfoxide, an oxidative stress marker and glutathione peroxidase activity were increased in the MGO-treated rats. The levels of glutathione, glutamate, aspartate, ornithine and AGEs were also increased in these rats. MGO upregulated the gene expression of transporters and enzymes related to the metabolism of glutathione, glutamate and ornithine in the peritoneum. These results suggest that MGO may induce peritoneal injury with mesenchymal cell proliferation via increased redox metabolism, directly or through the formation of AGEs during PD.

NAD(P)H Quinone Dehydrogenase 1 Ablation Inhibits Activation of the Phosphoinositide 3-Kinase/Akt Serine/Threonine Kinase and Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase Pathways and Blocks Metabolic Adaptation in Hepatocellular Carcinoma

Cancer cells undergo metabolic adaptation to sustain uncontrolled proliferation. Aerobic glycolysis and glutaminolysis are two of the most essential characteristics of cancer metabolic reprogramming. Hyperactivated phosphoinositide 3-kinase (PI3K)/Akt serine/threonine kinase (Akt) and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling pathways play central roles in cancer cell metabolic adaptation given that their downstream effectors, such as Akt and c-Myc, control most of the glycolytic and glutaminolysis genes. Here, we report that the cytosolic flavoprotein, NAD(P)H quinone dehydrogenase 1 (Nqo1), is strongly overexpressed in mouse and human hepatocellular carcinoma (HCC). Knockdown of Nqo1 enhanced activity of the serine/threonine phosphatase, protein phosphatase 2A, which operates at the intersection of the PI3K/Akt and MAPK/ERK pathways and dephosphorylates and inactivates pyruvate dehydrogenase kinase 1, Akt, Raf, mitogen-activated protein kinase kinase, and ERK1/2. Nqo1 ablation also induced the expression of phosphatase and tensin homolog, a dual protein/lipid phosphatase that blocks PI3K/Akt signaling, through the ERK/cAMP-responsive element-binding protein/c-Jun pathway. Together, Nqo1 ablation triggered simultaneous inhibition of the PI3K/Akt and MAPK/ERK pathways, suppressed the expression of glycolysis and glutaminolysis genes and blocked metabolic adaptation in liver cancer cells. Conversely, Nqo1 overexpression caused hyperactivation of the PI3K/Akt and MAPK/ERK pathways and promoted metabolic adaptation. Conclusion: In conclusion, Nqo1 functions as an upstream activator of both the PI3K/Akt and MAPK/ERK pathways in liver cancer cells, and Nqo1 ablation blocked metabolic adaptation and inhibited liver cancer cell proliferation and HCC growth in mice. Therefore, our results suggest that Nqo1 may function as a therapeutic target to inhibit liver cancer cell proliferation and inhibit HCC.

The activation loop and substrate-binding cleft of glutaminase C are allosterically coupled

The glutaminase C (GAC) isoform of mitochondrial glutaminase is overexpressed in many cancer cells and therefore represents a potential therapeutic target. Understanding the regulation of GAC activity has been guided by the development of spectroscopic approaches that measure glutaminase activity in real time. Previously, we engineered a GAC protein (GAC(F327W)) in which a tryptophan residue is substituted for phenylalanine in an activation loop to explore the role of this loop in enzyme activity. We showed that the fluorescence emission of Trp-327 is enhanced in response to activator binding, but quenched by inhibitors of the BPTES class that bind to the GAC tetramer and contact the activation loop, thereby constraining it in an inactive conformation. In the present work, we took advantage of a tryptophan substitution at position 471, proximal to the GAC catalytic site, to examine the conformational coupling between the activation loop and the substrate-binding cleft, separated by ∼16 Å. Comparison of glutamine binding in the presence or absence of the BPTES analog CB-839 revealed a reciprocal relationship between the constraints imposed on the activation loop position and the affinity of GAC for substrate. Binding of the inhibitor weakened the affinity of GAC for glutamine, whereas activating anions such as P_i increased this affinity. These results indicate that the conformations of the activation loop and the substrate-binding cleft in GAC are allosterically coupled and that this coupling determines substrate affinity and enzymatic activity and explains the activities of CB-839, which is currently in clinical trials.

Metabolic changes related to the IDH1 mutation in gliomas preserve TCA-cycle activity: An investigation at the protein level

The discovery of the IDH1 R132H (IDH1 mut) mutation in low-grade glioma and the associated change in function of the IDH1 enzyme has increased the interest in glioma metabolism. In an earlier study, we found that changes in expression of genes involved in the aerobic glycolysis and the TCA cycle are associated with IDH1 mut. Here, we apply proteomics to FFPE samples of diffuse gliomas with or without IDH1 mutations, to map changes in protein levels associated with this mutation. We observed significant changes in the enzyme abundance associated with aerobic glycolysis, glutamate metabolism, and the TCA cycle in IDH1 mut gliomas. Specifically, the enzymes involved in the metabolism of glutamate, lactate, and enzymes involved in the conversion of α-ketoglutarate were increased in IDH1 mut gliomas. In addition, the bicarbonate transporter (SLC4A4) was increased in IDH1 mut gliomas, supporting the idea that a mechanism preventing intracellular acidification is active. We also found that enzymes that convert proline, valine, leucine, and isoleucine into glutamate were increased in IDH1 mut glioma. We conclude that in IDH1 mut glioma metabolism is rewired (increased input of lactate and glutamate) to preserve TCA-cycle activity in IDH1 mut gliomas.

Energy Metabolism Rewiring Precedes UVB-Induced Primary Skin Tumor Formation

Although growing evidence indicates that bioenergetic metabolism plays an important role in the progression of tumorigenesis, little information is available on the contribution of reprogramming of energy metabolism in cancer initiation. By applying a quantitative proteomic approach and targeted metabolomics, we find that specific metabolic modifications precede primary skin tumor formation. Using a multistage model of ultraviolet B (UVB) radiation-induced skin cancer, we show that glycolysis, tricarboxylic acid (TCA) cycle, and fatty acid β-oxidation are decreased at a very early stage of photocarcinogenesis, while the distal part of the electron transport chain (ETC) is upregulated. Reductive glutamine metabolism and the activity of dihydroorotate dehydrogenase (DHODH) are both necessary for maintaining high ETC. Mice with decreased DHODH activity or impaired ETC failed to develop pre-malignant and malignant lesions. DHODH activity represents a major link between DNA repair efficiency and bioenergetic patterning during skin carcinogenesis.

Pharmacokinetic Assessment of 18F-(2S,4R)-4-Fluoroglutamine in Patients with Cancer

¹⁸F-(2S,4R)-4-fluoroglutamine (¹⁸F-FGln) is an investigational PET radiotracer for imaging tumor glutamine flux and metabolism. The aim of this study was to investigate its pharmacokinetic properties in patients with cancer. Methods: Fifty lesions from 41 patients (21 men and 20 women, aged 54 ± 14 y) were analyzed. Thirty-minute dynamic PET scans were performed concurrently with a rapid intravenous bolus injection of 232 ± 82 MBq of ¹⁸F-FGln, followed by 2 static PET scans at 97 ± 14 and 190 ± 12 min after injection. Five patients also underwent a second ¹⁸F-FGln study 4-13 wk after initiation of therapy with glutaminase, dual TORC1/2, or programmed death-1 inhibitors. Blood samples were collected to determine plasma and metabolite fractions and to scale the image-derived input function. Regions of interest were manually drawn to calculate SUVs. Pharmacokinetic modeling with both reversible and irreversible 1- and 2-tissue-compartment models was performed to calculate the kinetic rate constants K ₁, k ₂, k ₃, and k ₄ The analysis was repeated with truncated 30-min dynamic datasets. Results: Intratumor ¹⁸F-FGln uptake patterns demonstrated substantial heterogeneity in different lesion types. In most lesions, the reversible 2-tissue-compartment model was chosen as the most appropriate according to the Akaike information criterion. K ₁, a surrogate biomarker for ¹⁸F-FGln intracellular transport, was the kinetic rate constant that was most correlated both with SUV at 30 min (Spearman ρ = 0.71) and with SUV at 190 min (ρ = 0.51). Only K ₁ was reproducible from truncated 30-min datasets (intraclass correlation coefficient, 0.96). k ₃, a surrogate biomarker for glutaminolysis rate, was relatively low in about 50% of lesions. Treatment with glutaminase inhibitor CB-839 substantially reduced the glutaminolysis rates as measured by k ₃ Conclusion: ¹⁸F-FGln dynamic PET is a sensitive tool for studying glutamine transport and metabolism in human malignancies. Analysis of dynamic data facilitates better understanding of ¹⁸F-FGln pharmacokinetics and may be necessary for response assessment to targeted therapies that impact intracellular glutamine pool size and tumor glutaminolysis rates.

β-Catenin mutations as determinants of hepatoblastoma phenotypes in mice

Hepatoblastoma (HB) is the most common pediatric liver cancer. Although long-term survival of HB is generally favorable, it depends on clinical stage, tumor histology, and a variety of biochemical and molecular features. HB appears almost exclusively before the age of 3 years, is represented by seven histological subtypes, and is usually associated with highly heterogeneous somatic mutations in the catenin β1 (CTNNB1) gene, which encodes β-catenin, a Wnt ligand-responsive transcriptional co-factor. Numerous recurring β-catenin mutations, not previously documented in HB, have also been identified in various other pediatric and adult cancer types. Little is known about the underlying factors that determine the above HB features and behaviors or whether non-HB-associated β-catenin mutations are tumorigenic when expressed in hepatocytes. Here, we investigated the oncogenic properties of 14 different HB- and non-HB-associated β-catenin mutants encoded by Sleeping Beauty vectors following their delivery into the mouse liver by hydrodynamic tail-vein injection. We show that all β-catenin mutations, as well as WT β-catenin, are tumorigenic when co-expressed with a mutant form of yes-associated protein (YAP). However, tumor growth rates, histologies, nuclear-to-cytoplasmic partitioning, and metabolic and transcriptional landscapes were strongly influenced by the identities of the β-catenin mutations. These findings provide a context for understanding at the molecular level the notable biological diversity of HB.

Inhibition of Glutaminase 1 Attenuates Experimental Pulmonary Fibrosis

It has been increasingly recognized lately that aberrant cellular metabolism plays an important role in the pathogenesis of pulmonary fibrosis. In our previous systemic studies, we found that human lung myofibroblasts undergo glutaminolytic reprogramming, which is mediated by an increased expression of glutaminase (Gls) 1. We showed that augmented glutaminolysis critically regulates collagen production by promoting its stabilization in human lung myofibroblasts. Our study indicates that lung fibroblast Gls1 is a promising therapeutic target for this disease. In this investigation, we primarily focused on delineating the in vivo role of fibroblast Gls1 in mouse models of pulmonary fibrosis and determining the efficacy of Gls1 inhibition in treating this pathology. We now show that fibroblast Gls1 is upregulated in fibrotic mouse lungs. We present evidence that mice with ablation of fibroblast Gls1 are protected from bleomycin-induced lung fibrosis. We show that the Gls1 inhibitor, CB-839, is therapeutically efficacious in treating both bleomycin- and transforming growth factor-β1-induced pulmonary fibrosis. Our study has thus established a solid rationale for advancing Gls1 inhibitors, particularly CB-839, to the next stage of testing in the treatment of this disease.

Causes and Consequences of A Glutamine Induced Normoxic HIF1 Activity for the Tumor Metabolism

The transcription factor hypoxia-inducible factor 1 (HIF1) is the crucial regulator of genes that are involved in metabolism under hypoxic conditions, but information regarding the transcriptional activity of HIF1 in normoxic metabolism is limited. Different tumor cells were treated under normoxic and hypoxic conditions with various drugs that affect cellular metabolism. HIF1α was silenced by siRNA in normoxic/hypoxic tumor cells, before RNA sequencing and bioinformatics analyses were performed while using the breast cancer cell line MDA-MB-231 as a model. Differentially expressed genes were further analyzed and validated by qPCR, while the activity of the metabolites was determined by enzyme assays. Under normoxic conditions, HIF1 activity was significantly increased by (i) glutamine metabolism, which was associated with the release of ammonium, and it was decreased by (ii) acetylation via acetyl CoA synthetase (ACSS2) or ATP citrate lyase (ACLY), respectively, and (iii) the presence of L-ascorbic acid, citrate, or acetyl-CoA. Interestingly, acetylsalicylic acid, ibuprofen, L-ascorbic acid, and citrate each significantly destabilized HIF1α only under normoxia. The results from the deep sequence analyses indicated that, in HIF1-siRNA silenced MDA-MB-231 cells, 231 genes under normoxia and 1384 genes under hypoxia were transcriptionally significant deregulated in a HIF1-dependent manner. Focusing on glycolysis genes, it was confirmed that HIF1 significantly regulated six normoxic and 16 hypoxic glycolysis-associated gene transcripts. However, the results from the targeted metabolome analyses revealed that HIF1 activity affected neither the consumption of glucose nor the release of ammonium or lactate; however, it significantly inhibited the release of the amino acid alanine. This study comprehensively investigated, for the first time, how normoxic HIF1 is stabilized, and it analyzed the possible function of normoxic HIF1 in the transcriptome and metabolic processes of tumor cells in a breast cancer cell model. Furthermore, these data imply that HIF1 compensates for the metabolic outcomes of glutaminolysis and, subsequently, the Warburg effect might be a direct consequence of the altered amino acid metabolism in tumor cells.

Inhibition of Anaplerotic Glutaminolysis Underlies Selenite Toxicity in Human Lung Cancer

Large clinical trials and model systems studies suggest that the chemical form of selenium dictates chemopreventive and chemotherapeutic efficacy. Selenite induces excess ROS production, which mediates autophagy and eventual cell death in non-small cell lung cancer adenocarcinoma A549 cells. As the mechanisms underlying these phenotypic effects are unclear, the clinical relevance of selenite for cancer therapy remains to be determined. The authors' previous stable isotope-resolved metabolomics and gene expression analysis showed that selenite disrupts glycolysis, the Krebs cycle, and polyamine metabolism in A549 cells, potentially through perturbed glutaminolysis, a vital anaplerotic process for proliferation of many cancer cells. Herein, the role of the glutaminolytic enzyme glutaminase 1 (GLS1) in selenite's toxicity in A549 cells and in patient-derived lung cancer tissues is investigated. Using [¹³ C₆ ]-glucose and [¹³ C₅ ,¹⁵ N₂ ]-glutamine tracers, selenite's action on metabolic networks is determined. Selenite inhibits glutaminolysis and glutathione synthesis by suppressing GLS1 expression, and blocks the Krebs cycle, but transiently activates pyruvate carboxylase activity. Glutamate supplementation partially rescues these anti-proliferative and oxidative stress activities. Similar metabolic perturbations and necrosis are observed in selenite-treated human patients' cancerous lung tissues ex vivo. The results support the hypothesis that GLS1 suppression mediates part of the anti-cancer activity of selenite both in vitro and ex vivo.

Inhibition of cancer metabolism: a patent landscape

Cancer metabolism is currently a hot topic. Since it was first realized that cancer cells rely upon an altered metabolic program to sustain their rapid proliferation, the enzymes that support those metabolic changes have appeared to be good targets for pharmacological intervention. Here, we discuss efforts pertaining to targets in cancer metabolism, focusing upon the tricarboxylic acid cycle and the mechanisms which feed nutrients into it. We describe a broad landscape of small-molecule inhibitors, targeting a dozen different proteins, each implicated in cancer progression. We hope that this will serve as a reference both to the areas being most highly examined today and, relatedly, the areas that are still ripe for novel intervention.

Wnt Signaling in Cancer Metabolism and Immunity

The Wingless (Wnt)/β-catenin pathway has long been associated with tumorigenesis, tumor plasticity, and tumor-initiating cells called cancer stem cells (CSCs). Wnt signaling has recently been implicated in the metabolic reprogramming of cancer cells. Aberrant Wnt signaling is considered to be a driver of metabolic alterations of glycolysis, glutaminolysis, and lipogenesis, processes essential to the survival of bulk and CSC populations. Over the past decade, the Wnt pathway has also been shown to regulate the tumor microenvironment (TME) and anti-cancer immunity. Wnt ligands released by tumor cells in the TME facilitate the immune evasion of cancer cells and hamper immunotherapy. In this review, we illustrate the role of the canonical Wnt/β-catenin pathway in cancer metabolism and immunity to explore the potential therapeutic approach of targeting Wnt signaling from a metabolic and immunological perspective.

Non-oncogene Addiction to SIRT3 Plays a Critical Role in Lymphomagenesis

Diffuse large B cell lymphomas (DLBCLs) are genetically heterogeneous and highly proliferative neoplasms derived from germinal center (GC) B cells. Here, we show that DLBCLs are dependent on mitochondrial lysine deacetylase SIRT3 for proliferation, survival, self-renewal, and tumor growth in vivo regardless of disease subtype and genetics. SIRT3 knockout attenuated B cell lymphomagenesis in VavP-Bcl2 mice without affecting normal GC formation. Mechanistically, SIRT3 depletion impaired glutamine flux to the TCA cycle via glutamate dehydrogenase and reduction in acetyl-CoA pools, which in turn induce autophagy and cell death. We developed a mitochondrial-targeted class I sirtuin inhibitor, YC8-02, which phenocopied the effects of SIRT3 depletion and killed DLBCL cells. SIRT3 is thus a metabolic non-oncogene addiction and therapeutic target for DLBCLs.