Norovirus NS1/2 protein increases glutaminolysis for efficient viral replication.

Viruses are obligate intracellular parasites that rely on host cell metabolism for successful replication. Thus, viruses rewire host cell pathways involved in central carbon metabolism to increase the availability of building blocks for successful propagation. However, the underlying mechanisms of virus-induced alterations to host metabolism are largely unknown. Noroviruses (NoVs) are highly prevalent pathogens that cause sporadic and epidemic viral gastroenteritis. In the present study, we uncovered several strain-specific and shared host cell metabolic requirements of three murine norovirus (MNV) strains, MNV-1, CR3, and CR6. While all three strains required glycolysis, glutaminolysis, and the pentose phosphate pathway for optimal infection of macrophages, only MNV-1 relied on host oxidative phosphorylation. Furthermore, the first metabolic flux analysis of NoV-infected cells revealed that both glycolysis and glutaminolysis are upregulated during MNV-1 infection of macrophages. Glutamine deprivation affected the viral lifecycle at the stage of genome replication, resulting in decreased non-structural and structural protein synthesis, viral assembly, and egress. Mechanistic studies further showed that MNV infection and overexpression of the non-structural protein NS1/2 increased the enzymatic activity of the rate-limiting enzyme glutaminase. In conclusion, the inaugural investigation of NoV-induced alterations to host glutaminolysis identified NS1/2 as the first viral molecule for RNA viruses that regulates glutaminolysis either directly or indirectly. This increases our fundamental understanding of virus-induced metabolic alterations and may lead to improvements in the cultivation of human NoVs.

Inulin-gel-based oral immunotherapy remodels the small intestinal microbiome and suppresses food allergy.

Despite the potential of oral immunotherapy against food allergy, adverse reactions and loss of desensitization hinder its clinical uptake. Dysbiosis of the gut microbiota is implicated in the increasing prevalence of food allergy, which will need to be regulated to enable for an effective oral immunotherapy against food allergy. Here we report an inulin gel formulated with an allergen that normalizes the dysregulated ileal microbiota and metabolites in allergic mice, establishes allergen-specific oral tolerance and achieves robust oral immunotherapy efficacy with sustained unresponsiveness in food allergy models. These positive outcomes are associated with enhanced allergen uptake by antigen-sampling dendritic cells in the small intestine, suppressed pathogenic type 2 immune responses, increased interferon-γ+ and interleukin-10+ regulatory T cell populations, and restored ileal abundances of Eggerthellaceae and Enterorhabdus in allergic mice. Overall, our findings underscore the therapeutic potential of the engineered allergen gel as a suitable microbiome-modulating platform for food allergy and other allergic diseases.

Genomic deletion of malic enzyme 2 confers collateral lethality in pancreatic cancer.

The genome of pancreatic ductal adenocarcinoma (PDAC) frequently contains deletions of tumour suppressor gene loci, most notably SMAD4, which is homozygously deleted in nearly one-third of cases. As loss of neighbouring housekeeping genes can confer collateral lethality, we sought to determine whether loss of the metabolic gene malic enzyme 2 (ME2) in the SMAD4 locus would create cancer-specific metabolic vulnerability upon targeting of its paralogous isoform ME3. The mitochondrial malic enzymes (ME2 and ME3) are oxidative decarboxylases that catalyse the conversion of malate to pyruvate and are essential for NADPH regeneration and reactive oxygen species homeostasis. Here we show that ME3 depletion selectively kills ME2-null PDAC cells in a manner consistent with an essential function for ME3 in ME2-null cancer cells. Mechanistically, integrated metabolomic and molecular investigation of cells deficient in mitochondrial malic enzymes revealed diminished NADPH production and consequent high levels of reactive oxygen species. These changes activate AMP activated protein kinase (AMPK), which in turn directly suppresses sterol regulatory element-binding protein 1 (SREBP1)-directed transcription of its direct targets including the BCAT2 branched-chain amino acid transaminase 2) gene. BCAT2 catalyses the transfer of the amino group from branched-chain amino acids to α-ketoglutarate (α-KG) thereby regenerating glutamate, which functions in part to support de novo nucleotide synthesis. Thus, mitochondrial malic enzyme deficiency, which results in impaired NADPH production, provides a prime 'collateral lethality' therapeutic strategy for the treatment of a substantial fraction of patients diagnosed with this intractable disease.

The key role of extracellular vesicles in the metastatic process.

Extracellular vesicles (EVs), including exosomes, have a key role in the paracrine communication between organs and compartments. EVs shuttle virtually all types of biomolecules such as proteins, lipids, nucleic acids, metabolites and even pharmacological compounds. Their ability to transfer their biomolecular cargo into target cells enables EVs to play a key role in intercellular communication that can regulate cellular functions such as proliferation, apoptosis and migration. This has led to the emergence of EVs as a key player in tumor growth and metastasis through the formation of "tumor niches" in target organs. Recent data have also been shown that EVs may transform the microenvironment of primary tumors thus favoring the selection of cancer cells with a metastatic behavior. The release of EVs from resident non-malignant cells may contribute to the metastatic processes as well. However, cancer EVs may induce malignant transformation in resident mesenchymal stem cells, suggesting that the metastatic process is not exclusively due to circulating tumor cells. In this review, we outline and discuss evidence-based roles of EVs in actively regulating multiple steps of the metastatic process and how we can leverage EVs to impair metastasis.

Glutaminolysis: A Hallmark of Cancer Metabolism.

Glutamine is the most abundant circulating amino acid in blood and muscle and is critical for many fundamental cell functions in cancer cells, including synthesis of metabolites that maintain mitochondrial metabolism; generation of antioxidants to remove reactive oxygen species; synthesis of nonessential amino acids (NEAAs), purines, pyrimidines, and fatty acids for cellular replication; and activation of cell signaling. In light of the pleiotropic role of glutamine in cancer cells, a comprehensive understanding of glutamine metabolism is essential for the development of metabolic therapeutic strategies for targeting cancer cells. In this article, we review oncogene-, tumor suppressor-, and tumor microenvironment-mediated regulation of glutamine metabolism in cancer cells. We describe the mechanism of glutamine's regulation of tumor proliferation, metastasis, and global methylation. Furthermore, we highlight the therapeutic potential of glutamine metabolism and emphasize that clinical application of in vivo assessment of glutamine metabolism is critical for identifying new ways to treat patients through glutamine-based metabolic therapy.

Exo-MFA - A 13C metabolic flux analysis framework to dissect tumor microenvironment-secreted exosome contributions towards cancer cell metabolism.

Dissecting the pleiotropic roles of tumor micro-environment (TME) on cancer progression has been brought to the foreground of research on cancer pathology. Extracellular vesicles such as exosomes, transport proteins, lipids, and nucleic acids, to mediate intercellular communication between TME components and have emerged as candidates for anti-cancer therapy. We previously reported that cancer-associated fibroblast (CAF) derived exosomes (CDEs) contain metabolites in their cargo that are utilized by cancer cells for central carbon metabolism and promote cancer growth. However, the metabolic fluxes involved in donor cells towards packaging of metabolites in extracellular vesicles and exosome-mediated metabolite flux upregulation in recipient cells are still not known. Here, we have developed a novel empirical and computational technique, exosome-mediated metabolic flux analysis (Exo-MFA) to quantify flow of cargo from source cells to recipient cells via vesicular transport. Our algorithm, which is based on 13C metabolic flux analysis, successfully predicts packaging fluxes to metabolite cargo in CAFs, dynamic changes in rate of exosome internalization by cancer cells, and flux of cargo release over time. We find that cancer cells internalize exosomes rapidly leading to depletion of extracellular exosomes within 24h. However, metabolite cargo significantly alters intracellular metabolism over the course of 24h by regulating glycolysis pathway fluxes via lactate supply. Furthermore, it can supply up to 35% of the TCA cycle fluxes by providing TCA intermediates and glutamine. Our algorithm will help gain insight into (i) metabolic interactions in multicellular systems (ii) biogenesis of extracellular vesicles and their differential packaging of cargo under changing environments, and (iii) regulation of cancer cell metabolism by its microenvironment.

Synthesis and biological evaluation of dimeric furanoid macroheterocycles: discovery of new anticancer agents.

A recently developed dimerization/macrocyclization was employed to synthesize a series of macroheterocycles which were biologically evaluated, leading to the discovery of a number of potent cytotoxic agents (e.g., 27: GI50 = 51 nM against leukemia CCRF-CEM cell line; 29: GI50 = 99 nM against melanoma MDA-MB-435 cell line). Further biological studies support an apoptosis mechanism of action for these compounds involving deregulation of the tricarboxylic acid cycle activity and suppression of mitochondrial function in cancer cells.

Metabolic shifts toward glutamine regulate tumor growth, invasion and bioenergetics in ovarian cancer.

Glutamine can play a critical role in cellular growth in multiple cancers. Glutamine-addicted cancer cells are dependent on glutamine for viability, and their metabolism is reprogrammed for glutamine utilization through the tricarboxylic acid (TCA) cycle. Here, we have uncovered a missing link between cancer invasiveness and glutamine dependence. Using isotope tracer and bioenergetic analysis, we found that low-invasive ovarian cancer (OVCA) cells are glutamine independent, whereas high-invasive OVCA cells are markedly glutamine dependent. Consistent with our findings, OVCA patients' microarray data suggest that glutaminolysis correlates with poor survival. Notably, the ratio of gene expression associated with glutamine anabolism versus catabolism has emerged as a novel biomarker for patient prognosis. Significantly, we found that glutamine regulates the activation of STAT3, a mediator of signaling pathways which regulates cancer hallmarks in invasive OVCA cells. Our findings suggest that a combined approach of targeting high-invasive OVCA cells by blocking glutamine's entry into the TCA cycle, along with targeting low-invasive OVCA cells by inhibiting glutamine synthesis and STAT3 may lead to potential therapeutic approaches for treating OVCAs.

A switch in the source of ATP production and a loss in capacity to perform glycolysis are hallmarks of hepatocyte failure in advance liver disease.

BACKGROUND & AIMS: The cause of hepatic failure in the terminal stages of chronic injury is unknown. Cellular metabolic adaptations in response to the microenvironment have been implicated in cellular breakdown. METHODS: To address the role of energy metabolism in this process we studied mitochondrial number, respiration, and functional reserve, as well as cellular adenosine-5'-triphosphate (ATP) production, glycolytic flux, and expression of glycolysis related genes in isolated hepatocytes from early and terminal stages of cirrhosis using a model that produces hepatic failure from irreversible cirrhosis in rats. To study the clinical relevance of energy metabolism in terminal stages of chronic liver failure, we analyzed glycolysis and energy metabolism related gene expression in liver tissue from patients at different stages of chronic liver failure according to Child-Pugh classification. Additionally, to determine whether the expression of these genes in early-stage cirrhosis (Child-Pugh Class A) is related to patient outcome, we performed network analysis of publicly available microarray data obtained from biopsies of 216 patients with hepatitis C-related Child-Pugh A cirrhosis who were prospectively followed up for a median of 10years. RESULTS: In the early phase of cirrhosis, mitochondrial function and ATP generation are maintained by increasing energy production from glycolytic flux as production from oxidative phosphorylation falls. At the terminal stage of hepatic injury, mitochondria respiration and ATP production are significantly compromised, as the hepatocytes are unable to sustain the increased demand for high levels of ATP generation from glycolysis. This impairment corresponds to a decrease in glucose-6-phosphatase catalytic subunit and phosphoglucomutase 1. Similar decreased gene expression was observed in liver tissue from patients at different stages of chronic liver injury. Further, unbiased network analysis of microarray data revealed that expression of these genes was down regulated in the group of patients with poor outcome. CONCLUSIONS: An adaptive metabolic shift, from generating energy predominantly from oxidative phosphorylation to glycolysis, allows maintenance of energy homeostasis during early stages of liver injury, but leads to hepatocyte dysfunction during terminal stages of chronic liver disease because hepatocytes are unable to sustain high levels of energy production from glycolysis.

Modeling integrated cellular machinery using hybrid Petri-Boolean networks.

The behavior and phenotypic changes of cells are governed by a cellular circuitry that represents a set of biochemical reactions. Based on biological functions, this circuitry is divided into three types of networks, each encoding for a major biological process: signal transduction, transcription regulation, and metabolism. This division has generally enabled taming computational complexity dealing with the entire system, allowed for using modeling techniques that are specific to each of the components, and achieved separation of the different time scales at which reactions in each of the three networks occur. Nonetheless, with this division comes loss of information and power needed to elucidate certain cellular phenomena. Within the cell, these three types of networks work in tandem, and each produces signals and/or substances that are used by the others to process information and operate normally. Therefore, computational techniques for modeling integrated cellular machinery are needed. In this work, we propose an integrated hybrid model (IHM) that combines Petri nets and Boolean networks to model integrated cellular networks. Coupled with a stochastic simulation mechanism, the model simulates the dynamics of the integrated network, and can be perturbed to generate testable hypotheses. Our model is qualitative and is mostly built upon knowledge from the literature and requires fine-tuning of very few parameters. We validated our model on two systems: the transcriptional regulation of glucose metabolism in human cells, and cellular osmoregulation in S. cerevisiae. The model produced results that are in very good agreement with experimental data, and produces valid hypotheses. The abstract nature of our model and the ease of its construction makes it a very good candidate for modeling integrated networks from qualitative data. The results it produces can guide the practitioner to zoom into components and interconnections and investigate them using such more detailed mathematical models.

Comprehensive sampling of the lung microbiome in early-stage non-small cell lung cancer.

Objectives: Data are scarce on whether the composition of the lung microbiome (extending from the nasopharynx to the peripheral lung tissue) varies according to histology or grade of non-small cell lung cancer. We hypothesized that the composition of the lung microbiome would vary according to the histology and the grade of non-small cell lung cancer. Methods: We collected naso-oral and central lobar (cancer affected, ipsilateral unaffected, and contralateral unaffected) bronchoalveolar lavage fluid and brushing samples from patients with clinical early-stage lung cancer between July 2018 and February 2020 at a single academic center. We performed bacterial 16S rRNA sequencing and then compared clinical and pathologic findings with microbiome signatures. Results: Samples were collected from 28 patients. Microbial composition in affected lobes displayed unique enrichment of oropharyngeal bacterial species that was significantly different compared with that from the unaffected contralateral lobes; patients with chronic obstructive pulmonary disease had similar diversity to those without chronic obstructive pulmonary disease (P = .1312). The lung microbiome diversity in patients with adenocarcinoma was similar to those with squamous cell cancer (P = .27). There were no differences in diversity or composition in the unaffected lobes of patients with adenocarcinoma versus squamous cell cancer. There was a trend toward lower lung microbial diversity in poorly differentiated adenocarcinomas compared with well-differentiated adenocarcinomas (P = .08). Conclusions: The lung microbiota differs between cancer affected and unaffected lobes in the same patient. Furthermore, poorly differentiated lung cancers were associated with lower microbial diversity. Larger studies will be required to confirm these findings.

Oncosecretomics coupled to bioenergetics identifies α-amino adipic acid, isoleucine and GABA as potential biomarkers of cancer: Differential expression of c-Myc, Oct1 and KLF4 coordinates metabolic changes.

Bioenergetic profiling of tumors is a new challenge of cancer research and medicine as therapies are currently being developed. Meanwhile, methodological means must be proposed to gather information on tumor metabolism in order to adapt these potential therapies to the bioenergetic specificities of tumors. Studies performed on tumors and cancer cell lines have shown that cancer cells bioenergetics is highly variable. This profile changes with microenvironmental conditions (eg. substrate availability), the oncogenes activated (and the tumor suppressors inactivated) and the interaction with the stroma (i.e. reverse Warburg effect). Here, we assessed the power of metabolic footprinting (MFP) to unravel the bioenergetics and associated anabolic changes induced by three oncogenes, c-Myc, KLF4 and Oct1. The MFP approach provides a quantitative analysis of the metabolites secreted and consumed by cancer cells. We used ultra performance liquid chromatography for quantifying the amino acid uptake and secretion. To investigate the potential oncogene-mediated alterations in mitochondrial metabolism, we measured oxygen consumption rate and ATP production as well as the glucose uptake and lactate release. Our findings show that c-Myc deficiency initiates the Warburg effect along with a reduction of mitochondrial respiration. KLF4 deficiency also stimulated glycolysis, albeit without cellular respiration impairment. In contrast, Oct1 deficiency reduced glycolysis and enhanced oxidative phosphorylation efficiency. MFP revealed that c-Myc, KLF4 and Oct1 altered amino acid metabolism with specific patterns. We identified isoleucine, α-aminoadipic acid and GABA (γ-aminoisobutyric acid) as biomarkers related. Our findings establish the impact of Oct1, KLF4 and c-Myc on cancer bioenergetics and evidence a link between oncosecretomics and cellular bioenergetics profile.

The glucose-deprivation network counteracts lapatinib-induced toxicity in resistant ErbB2-positive breast cancer cells.

Dynamic interactions between intracellular networks regulate cellular homeostasis and responses to perturbations. Targeted therapy is aimed at perturbing oncogene addiction pathways in cancer, however, development of acquired resistance to these drugs is a significant clinical problem. A network-based computational analysis of global gene expression data from matched sensitive and acquired drug-resistant cells to lapatinib, an EGFR/ErbB2 inhibitor, revealed an increased expression of the glucose deprivation response network, including glucagon signaling, glucose uptake, gluconeogenesis and unfolded protein response in the resistant cells. Importantly, the glucose deprivation response markers correlated significantly with high clinical relapse rates in ErbB2-positive breast cancer patients. Further, forcing drug-sensitive cells into glucose deprivation rendered them more resistant to lapatinib. Using a chemical genomics bioinformatics mining of the CMAP database, we identified drugs that specifically target the glucose deprivation response networks to overcome the resistant phenotype and reduced survival of resistant cells. This study implicates the chronic activation of cellular compensatory networks in response to targeted therapy and suggests novel combinations targeting signaling and metabolic networks in tumors with acquired resistance.

Norovirus NS1/2 protein increases glutaminolysis for efficient viral replication.

Viruses are obligate intracellular parasites that rely on host cell metabolism for successful replication. Thus, viruses rewire host cell pathways involved in central carbon metabolism to increase the availability of building blocks for replication. However, the underlying mechanisms of virus-induced alterations to host metabolism are largely unknown. Noroviruses (NoVs) are highly prevalent pathogens that cause sporadic and epidemic viral gastroenteritis. In the present study, we uncovered several strain-specific and shared host cell metabolic requirements of three murine norovirus (MNV) strains, the acute MNV-1 strain and the persistent CR3 and CR6 strains. While all three strains required glycolysis, glutaminolysis, and the pentose phosphate pathway for optimal infection of macrophages, only MNV-1 relied on host oxidative phosphorylation. Furthermore, the first metabolic flux analysis of NoV-infected cells revealed that both glycolysis and glutaminolysis are upregulated during MNV-1 infection of macrophages. Glutamine deprivation affected the MNV lifecycle at the stage of genome replication, resulting in decreased non-structural and structural protein synthesis, viral assembly, and egress. Mechanistic studies further showed that MNV infection and overexpression of the MNV non-structural protein NS1/2 increased the enzymatic activity of the rate-limiting enzyme glutaminase. In conclusion, the inaugural investigation of NoV-induced alterations to host glutaminolysis identified the first viral regulator of glutaminolysis for RNA viruses, which increases our fundamental understanding of virus-induced metabolic alterations.

Devimistat in Combination with Gemcitabine and Cisplatin in Biliary Tract Cancer: Preclinical Evaluation and Phase Ib Multicenter Clinical Trial (BilT-04).

PURPOSE: Devimistat (CPI-613) is a novel inhibitor of tumoral mitochondrial metabolism. We investigated the effect of devimistat in vitro and in a phase Ib clinical trial in patients with advanced biliary tract cancer (BTC). PATIENTS AND METHODS: Cell viability assays of devimistat ± gemcitabine and cisplatin (GC) were performed and the effect of devimistat on mitochondrial respiration via oxygen consumption rate (OCR) was evaluated. A phase Ib/II trial was initiated in patients with untreated advanced BTC. In phase Ib, devimistat was infused over 2 hours in combination with GC on days 1 and 8 every 21 days with a primary objective to determine the recommended phase II dose (RP2D). Secondary objectives included safety, overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). RESULTS: In vitro, devimistat with GC had a synergistic effect on two cell lines. Devimistat significantly decreased OCR at higher doses and in arms with divided dosing. In the phase Ib trial, 20 patients received a median of nine cycles (range, 3-19). One DLT was observed, and the RP2D of devimistat was determined to be 2,000 mg/m2 in combination with GC. Most common grade 3 toxicities included neutropenia (n = 11, 55%), anemia (n = 4, 20%), and infection (n = 3, 15%). There were no grade 4 toxicities. After a median follow-up of 15.6 months, ORR was 45% and median PFS was 10 months (95% confidence interval, 7.1-14.9). Median OS is not yet estimable. CONCLUSIONS: Devimistat in combination with GC is well tolerated and has an acceptable safety profile in patients with untreated advanced BTC.

Exploiting metabolic vulnerabilities after anti-VEGF antibody therapy in ovarian cancer.

Despite modest clinical improvement with anti-vascular endothelial growth factor antibody (AVA) therapy in ovarian cancer, adaptive resistance is ubiquitous and additional options are limited. A dependence on glutamine metabolism, via the enzyme glutaminase (GLS), is a known mechanism of adaptive resistance and we aimed to investigate the utility of a GLS inhibitor (GLSi). Our in vitro findings demonstrated increased glutamine abundance and a significant cytotoxic effect in AVA-resistant tumors when GLSi was administered in combination with bevacizumab. In vivo, GLSi led to a reduction in tumor growth as monotherapy and when combined with AVA. Furthermore, GLSi initiated after the emergence of resistance to AVA therapy resulted in a decreased metabolic conversion of pyruvate to lactate as assessed by hyperpolarized magnetic resonance spectroscopy and demonstrated robust antitumor effects with a survival advantage. Given the increasing population of patients receiving AVA therapy, these findings justify further development of GLSi in AVA resistance.

Rewiring of cortical glucose metabolism fuels human brain cancer growth.

The brain avidly consumes glucose to fuel neurophysiology. Cancers of the brain, such as glioblastoma (GBM), lose aspects of normal biology and gain the ability to proliferate and invade healthy tissue. How brain cancers rewire glucose utilization to fuel these processes is poorly understood. Here we perform infusions of 13 C-labeled glucose into patients and mice with brain cancer to define the metabolic fates of glucose-derived carbon in tumor and cortex. By combining these measurements with quantitative metabolic flux analysis, we find that human cortex funnels glucose-derived carbons towards physiologic processes including TCA cycle oxidation and neurotransmitter synthesis. In contrast, brain cancers downregulate these physiologic processes, scavenge alternative carbon sources from the environment, and instead use glucose-derived carbons to produce molecules needed for proliferation and invasion. Targeting this metabolic rewiring in mice through dietary modulation selectively alters GBM metabolism and slows tumor growth. Significance: This study is the first to directly measure biosynthetic flux in both glioma and cortical tissue in human brain cancer patients. Brain tumors rewire glucose carbon utilization away from oxidation and neurotransmitter production towards biosynthesis to fuel growth. Blocking these metabolic adaptations with dietary interventions slows brain cancer growth with minimal effects on cortical metabolism.

Metabolomics for mitochondrial and cancer studies.

Metabolomics, a high-throughput global metabolite analysis, is a burgeoning field, and in recent times has shown substantial evidence to support its emerging role in cancer diagnosis, cancer recurrence, and prognosis, as well as its impact in identifying novel cancer biomarkers and developing cancer therapeutics. Newly evolving advances in disease diagnostics and therapy will further facilitate future growth in the field of metabolomics, especially in cancer, where there is a dire need for sensitive and more affordable diagnostic tools and an urgency to develop effective therapies and identify reliable biomarkers to predict accurately the response to a therapy. Here, we review the application of metabolomics in cancer and mitochondrial studies and its role in enabling the understanding of altered metabolism and malignant transformation during cancer growth and metastasis. The recent developments in the area of metabolic flux analysis may help to close the gap between clinical metabolomics research and the development of cancer metabolome. In the era of personalized medicine with more and more patient specific targeted therapies being used, we need reliable, dynamic, faster, and yet sensitive biomarkers both to track the disease and to develop and evolve therapies during the course of treatment. Recent advances in metabolomics along with the novel strategies to analyze, understand, and construct the metabolic pathways opens this window of opportunity in a very cost-effective manner.

Pyruvate uptake is increased in highly invasive ovarian cancer cells under anoikis conditions for anaplerosis, mitochondrial function, and migration.

Anoikis resistance, or the ability for cells to live detached from the extracellular matrix, is a property of epithelial cancers. The "Warburg effect," or the preference of cancer cells for glycolysis for their energy production even in the presence of oxygen, has been shown to be evident in various tumors. Since a cancer cell's metastatic ability depends on microenvironmental conditions (nutrients, stromal cells, and vascularization) and is highly variable for different organs, their cellular metabolic fluxes and nutrient demand may show considerable differences. Moreover, a cancer cell's metastatic ability, which is dependent on the stage of cancer, may further create metabolic alterations depending on its microenvironment. Although recent studies have aimed to elucidate cancer cell metabolism under detached conditions, the nutrient demand and metabolic activity of cancer cells under nonadherent conditions remain poorly understood. Additionally, less is known about metabolic alterations in ovarian cancer cells with varying invasive capability under anoikis conditions. We hypothesized that the metabolism of highly invasive ovarian cancer cells in detachment would differ from less invasive ovarian cancer cells and that ovarian cancer cells will have altered metabolism in detached vs. attached conditions. To assess these metabolic differences, we integrated a secretomics-based metabolic footprinting (MFP) approach with mitochondrial bioenergetics. Interestingly, MFP revealed higher pyruvate uptake and oxygen consumption in more invasive ovarian cancer cells than their less invasive counterparts. Furthermore, ATP production was higher in more invasive vs. less invasive ovarian cancer cells in detachment. We found that pyruvate has an effect on highly invasive ovarian cancer cells' migration ability. Our results are the first to demonstrate that higher mitochondrial activity is related to higher ovarian cancer invasiveness under detached conditions. Importantly, our results bring insights regarding the metabolism of cancer cells under nonadherent conditions and could lead to the development of therapies for modulating cancer cell invasiveness.

Driving with Both Feet: Supplementing AKG While Inhibiting BCAT1 Leads to Synthetic Lethality in GBM.

Understanding how carcinogenesis can expose cancers to synthetically lethal vulnerabilities has been an essential underpinning of development of modern anticancer therapeutics. Isocitrate dehydrogenase wild-type (IDHWT) glioblastoma multiforme (GBM), which is known to have upregulated branched-chain amino acid transaminase 1 (BCAT1) expression, has not had treatments developed to the same extent as the IDH mutant counterpart, despite making up the majority of cases. In this issue, Zhang and colleagues utilize a metabolic screen to identify α-ketoglutarate (AKG) as a synthetically lethal treatment in conjunction with BCAT1 inhibition in IDHWT GBM. These treatments synergize in a multipronged approach that limits substrate catabolism and disrupts mitochondrial homeostasis through perturbing the balance of NAD+/NADH, leading to mTORC1 inhibition and a reduction of nucleotide biosynthesis. Based on these results, the authors propose combination treatment targeting branched chain amino acid catabolism as a potential option for patients with IDHWT GBM. See related article by Zhang et al., p. 2388.