bims-glucam Biomed News
on Glutamine cancer metabolism
Issue of 2021‒02‒14
thirteen papers selected by
Sreeparna Banerjee
Middle East Technical University

  1. Int J Mol Sci. 2021 Feb 08. pii: 1701. [Epub ahead of print]22(4):
      The significance of glutamine in cancer metabolism has been extensively studied. Cancer cells consume an excessive amount of glutamine to facilitate rapid proliferation. Thus, glutamine depletion occurs in various cancer types, especially in poorly vascularized cancers. This makes glutamine synthetase (GS), the only enzyme responsible for de novo synthesizing glutamine, essential in cancer metabolism. In cancer, GS exhibits pro-tumoral features by synthesizing glutamine, supporting nucleotide synthesis. Furthermore, GS is highly expressed in the tumor microenvironment (TME) and provides glutamine to cancer cells, allowing cancer cells to maintain sufficient glutamine level for glutamine catabolism. Glutamine catabolism, the opposite reaction of glutamine synthesis by GS, is well known for supporting cancer cell proliferation via contributing biosynthesis of various essential molecules and energy production. Either glutamine anabolism or catabolism has a critical function in cancer metabolism depending on the complex nature and microenvironment of cancers. In this review, we focus on the role of GS in a variety of cancer types and microenvironments and highlight the mechanism of GS at the transcriptional and post-translational levels. Lastly, we discuss the therapeutic implications of targeting GS in cancer.
    Keywords:  anticancer effect; cancer metabolism; glutamine metabolism; glutamine synthetase
  2. J Immunol. 2021 Feb 08. pii: ji2001029. [Epub ahead of print]
      T effector cells promote inflammation in asthmatic patients, and both Th2 and Th17 CD4 T cells have been implicated in severe forms of the disease. The metabolic phenotypes and dependencies of these cells, however, remain poorly understood in the regulation of airway inflammation. In this study, we show the bronchoalveolar lavage fluid of asthmatic patients had markers of elevated glucose and glutamine metabolism. Further, peripheral blood T cells of asthmatics had broadly elevated expression of metabolic proteins when analyzed by mass cytometry compared with healthy controls. Therefore, we hypothesized that glucose and glutamine metabolism promote allergic airway inflammation. We tested this hypothesis in two murine models of airway inflammation. T cells from lungs of mice sensitized with Alternaria alternata extract displayed genetic signatures for elevated oxidative and glucose metabolism by single-cell RNA sequencing. This result was most pronounced when protein levels were measured in IL-17-producing cells and was recapitulated when airway inflammation was induced with house dust mite plus LPS, a model that led to abundant IL-4- and IL-17-producing T cells. Importantly, inhibitors of the glucose transporter 1 or glutaminase in vivo attenuated house dust mite + LPS eosinophilia, T cell cytokine production, and airway hyperresponsiveness as well as augmented the immunosuppressive properties of dexamethasone. These data show that T cells induce markers to support metabolism in vivo in airway inflammation and that this correlates with inflammatory cytokine production. Targeting metabolic pathways may provide a new direction to protect from disease and enhance the effectiveness of steroid therapy.
  3. Adv Cancer Res. 2021 ;pii: S0065-230X(20)30070-1. [Epub ahead of print]149 171-255
      Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide. Much recent research has delved into understanding the underlying molecular mechanisms of HCC pathogenesis, which has revealed to be heterogenous and complex. Two major hallmarks of HCC include: (i) a hijacked immunometabolism and (ii) a reprogramming in metabolic processes. We posit that the gut microbiota is a third component in an entanglement triangle contributing to HCC progression. Besides metagenomic studies highlighting the diagnostic potential in the gut microbiota profile, recent research is pinpointing the gut microbiota as an instigator, not just a mere bystander, in HCC. In this chapter, we discuss mechanistic insights on atypical immunometabolism and metabolic reprogramming in HCC, including the examination of tumor-associated macrophages and neutrophils, tumor-infiltrating lymphocytes (e.g., T-cell exhaustion, regulatory T-cells, natural killer T-cells), the Warburg effect, rewiring of the tricarboxylic acid cycle, and glutamine addiction. We further discuss the potential involvement of the gut microbiota in these characteristics of hepatocarcinogenesis. An immediate highlight is that microbiota metabolites (e.g., short chain fatty acids, secondary bile acids) can impair anti-tumor responses, which aggravates HCC. Lastly, we describe the rising 'new era' of immunotherapies (e.g., immune checkpoint inhibitors, adoptive T-cell transfer) and discuss for the potential incorporation of gut microbiota targeted therapeutics (e.g., probiotics, fecal microbiota transplantation) to alleviate HCC. Altogether, this chapter invigorates for continuous research to decipher the role of gut microbiome in HCC from its influence on immunometabolism and metabolic reprogramming.
    Keywords:  Glutamine addiction; Hepatocellular carcinoma; Immunotherapy; Probiotics and prebiotics; Secondary bile acids; Short chain fatty acids; Tricarboxylic acid cycle; Tumor infiltrating lymphocytes; Tumor-associated myeloid cells; Warburg effect
  4. Cell Death Discov. 2020 Apr 16. 6(1): 20
      Cancer cells upregulate anabolic processes to maintain high rates of cellular turnover. Limiting the supply of macromolecular precursors by targeting enzymes involved in biosynthesis is a promising strategy in cancer therapy. Several tumors excessively metabolize glutamine to generate precursors for nonessential amino acids, nucleotides, and lipids, in a process called glutaminolysis. Here we show that pharmacological inhibition of glutaminase (GLS) eradicates glioblastoma stem-like cells (GSCs), a small cell subpopulation in glioblastoma (GBM) responsible for therapy resistance and tumor recurrence. Treatment with small molecule inhibitors compound 968 and CB839 effectively diminished cell growth and in vitro clonogenicity of GSC neurosphere cultures. However, our pharmaco-metabolic studies revealed that only CB839 inhibited GLS enzymatic activity thereby limiting the influx of glutamine derivates into the TCA cycle. Nevertheless, the effects of both inhibitors were highly GLS specific, since treatment sensitivity markedly correlated with GLS protein expression. Strikingly, we found GLS overexpressed in in vitro GSC models as compared with neural stem cells (NSC). Moreover, our study demonstrates the usefulness of in vitro pharmaco-metabolomics to score target specificity of compounds thereby refining drug development and risk assessment.
  5. Cancers (Basel). 2021 Jan 29. pii: 524. [Epub ahead of print]13(3):
      Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are being tested in numerous clinical trials and are currently employed successfully in the clinic for the treatment of breast cancers. Understanding their mechanism of action and interaction with other therapies is vital in their clinical development. CDK4/6 regulate the cell cycle via phosphorylation and inhibition of the tumour suppressor RB, and in addition can phosphorylate many cellular proteins and modulate numerous cellular functions including cell metabolism. Metabolic reprogramming is observed in melanoma following standard-of-care BRAF/MEK inhibition and is involved in both therapeutic response and resistance. In preclinical models, CDK4/6 inhibitors overcome BRAF/MEK inhibitor resistance, leading to sustained tumour regression; however, the metabolic response to this combination has not been explored. Here, we investigate how CDK4/6 inhibition reprograms metabolism and if this alters metabolic reprogramming observed upon BRAF/MEK inhibition. Although CDK4/6 inhibition has no substantial effect on the metabolic phenotype following BRAF/MEK targeted therapy in melanoma, CDK4/6 inhibition alone significantly enhances mitochondrial metabolism. The increase in mitochondrial metabolism in melanoma cells following CDK4/6 inhibition is fuelled in part by both glutamine metabolism and fatty acid oxidation pathways and is partially dependent on p53. Collectively, our findings identify new p53-dependent metabolic vulnerabilities that may be targeted to improve response to CDK4/6 inhibitors.
    Keywords:  BRAF; CDK4; melanoma; metabolism; targeted therapy
  6. Mol Genet Metab Rep. 2021 Mar;26 100721
    Keywords:  2-oxoglutarate-malate antiport; Aspartate; Chromaffin cells; Citrin; Complex II, SDHx; Cytosolic glutamine reductive pathway; Familial pheochromocytoma; Glutamine; NADH redox status; Paraganglioma; SCL25A13; SLC25A11; Succinate dehydrogenase
  7. Front Oncol. 2020 ;10 571384
      Introduction: RHPN2, a member of rhophilin family of rho-binding proteins, regulates actin cytoskeleton and vesicular trafficking, and promotes mesenchymal transformation in cancer. We have found that RHPN2 was significantly mutated in lung adenocarcinoma (LUAD). However, the role of RHPN2 in lung cancer is not fully understood.Methods: In the present study, we investigated the expression of RHPN2 in 125 patients with LUAD by qRT-PCR and correlated its expression with clinical characteristics. The effects of RHPN2 on the proliferation and invasion of lung cancer cells were determined by CCK-8 and in vitro transwell assays, clonogenic assay, and xenograft mouse model. The RhoA pull down assay and Western blotting were performed to elucidate the mechanism of RNPN2 in tumorigenesis of lung cancer.
    Results: RHPN2 was overexpressed in tumors from LUAD, and high levels of RHPN2 were associated with poor prognosis of LUAD patients. RHPN2 was required for proliferation and invasion of lung cancer cells. Intriguingly, overexpression of RHPN2 conferred the resistance to glutamine depletion in lung cancer cells. Mechanistic studies revealed that ectopic overexpression of RHPN2 promoted the stability of c-Myc protein via phosphorylation at Ser62 and increased c-Myc target glutamine synthetase (GS). Analysis of GS expression in clinical sample showed that the expression of GS was elevated in tumor cells. Kaplan-Meier analysis revealed that high levels of GS were significantly associated with worse overall survival time of the patients with LUAD.
    Conclusions: Taken together, this study suggested that RHPN2 was involved in tumorigenesis of lung cancer via modulating c-Myc stability and the expression of its target GS in lung adenocarcinoma, which links RHPN2 and glutamine metabolism.
    Keywords:  RHPN2; c-Myc protein; glutamine synthetase; lung adenocarcinoma; tumorigenesis
  8. Neurooncol Adv. 2021 Jan-Dec;3(1):3(1): vdaa177
      Background: Recently, we showed that melanoma brain metastases (MBMs) are characterized by increased utilization of the oxidative phosphorylation (OXPHOS) metabolic pathway compared to melanoma extracranial metastases (ECMs). MBM growth was inhibited by a potent direct OXPHOS inhibitor, but observed toxicities support the need to identify alternative therapeutic strategies. Thus, we explored the features associated with OXPHOS to improve our understanding of the pathogenesis and potential therapeutic vulnerabilities of MBMs.Methods: We applied an OXPHOS gene signature to our cohort of surgically resected MBMs that had undergone RNA-sequencing (RNA-seq) (n = 88). Clustering by curated gene sets identified MBMs with significant enrichment (High-OXPHOS; n = 21) and depletion (Low-OXPHOS; n = 25) of OXPHOS genes. Clinical data, RNA-seq analysis, and immunohistochemistry were utilized to identify significant clinical, molecular, metabolic, and immune associations with OXPHOS in MBMs. Preclinical models were used to further compare melanomas with High- and Low-OXPHOS and for functional validation.
    Results: High-OXPHOS MBMs were associated with shorter survival from craniotomy compared to Low-OXPHOS MBMs. High-OXPHOS MBMs exhibited an increase in glutamine metabolism, and treatment with the glutaminase inhibitor CB839 improved survival in mice with MAPKi-resistant, High-OXPHOS intracranial xenografts. High-OXPHOS MBMs also exhibited a transcriptional signature of deficient immune activation, which was reversed in B16-F10 intracranial tumors with metformin treatment, an OXPHOS inhibitor.
    Conclusions: OXPHOS is associated with distinct clinical, molecular, metabolic, and immune phenotypes in MBMs. These associations suggest rational therapeutic strategies for further testing to improve outcomes in MBM patients.
    Keywords:  brain metastases; immune therapy; melanoma; oxidative phosphorylation; targeted therapy
  9. Front Physiol. 2020 ;11 609103
      Pyruvate kinase deficiency (PKD) is a rare congenital hemolytic anemia caused by mutations in the PKLR gene. Here, we review pathophysiological aspects of PKD, focusing on the interplay between pyruvate kinase (PK)-activity and reticulocyte maturation in the light of ferroptosis, an iron-dependent process of regulated cell death, and in particular its key player glutathione peroxidase 4 (GPX4). GPX4 plays an important role in mitophagy, the key step of peripheral reticulocyte maturation and GPX4 deficiency in reticulocytes results in a failure to fully mature. Mitophagy depends on lipid oxidation, which is under physiological conditions controlled by GPX4. Lack of GPX4 leads to uncontrolled auto-oxidation, which will disrupt autophagosome maturation and thereby perturb mitophagy. Based on our review, we propose a model for disturbed red cell maturation in PKD. A relative GPX4 deficiency occurs due to glutathione (GSH) depletion, as cytosolic L-glutamine is preferentially used in the form of α-ketoglutarate as fuel for the tricarboxylic acid (TCA) cycle at the expense of GSH production. The relative GPX4 deficiency will perturb mitophagy and, subsequently, results in failure of reticulocyte maturation, which can be defined as late stage ineffective erythropoiesis. Our hypothesis provides a starting point for future research into new therapeutic possibilities, which have the ability to correct the oxidative imbalance due to lack of GPX4.
    Keywords:  GPX4; ferroptosis; mitophagy; pyruvate kinase deficiency; reticulocytes
  10. Cell Metab. 2021 Feb 04. pii: S1550-4131(21)00014-0. [Epub ahead of print]
      Cell-to-cell heterogeneity in metabolism plays an unknown role in physiology and pharmacology. To functionally characterize cellular variability in metabolism, we treated cells with inhibitors of oxidative phosphorylation (OXPHOS) and monitored their responses with live-cell reporters for ATP, ADP/ATP, or activity of the energy-sensing kinase AMPK. Across multiple OXPHOS inhibitors and cell types, we identified a subpopulation of cells resistant to activation of AMPK and reduction of ADP/ATP ratio. This resistant state persists transiently for at least several hours and can be inherited during cell divisions. OXPHOS inhibition suppresses the mTORC1 and ERK growth signaling pathways in sensitive cells, but not in resistant cells. Resistance is linked to a multi-factorial combination of increased glucose uptake, reduced protein biosynthesis, and G0/G1 cell-cycle status. Our results reveal dynamic fluctuations in cellular energetic balance and provide a basis for measuring and predicting the distribution of cellular responses to OXPHOS inhibition.
    Keywords:  AKT; FRET; PI3K; adenosine mono-phosphate-regulated protein kinase; electron transport chain; insulin signaling; mammalian target of rapamycin; metabolic cycle; oligomycin; oscillation; translation regulation
  11. Invest New Drugs. 2021 Feb 13.
      Purpose Acute radiation-induced esophagitis (ARIE) leads to treatment delays, decreased quality of life (QOL), and secondary adverse events such as weight loss. Grade 3 ARIE occurs in 15%-30% of patients undergoing radiotherapy to the esophagus, leading to disruption or discontinuation of treatment. The purpose of this study was to assess the effects of glutamine, a common nutritional supplement, on ARIE in patients with thoracic malignancies. Patients and methods This double-blind, placebo-controlled trial enrolled patients with advanced thoracic malignancies receiving concurrent chemotherapy/radiotherapy or radiotherapy alone, with radiation doses to the esophagus ≥45 Gy. Patients were randomized (1:1) to receive 4 g of glutamine or glycine placebo twice daily. The primary objective was to determine whether glutamine decreases the severity of ARIE in these patients. Secondary objectives included assessment of the effects of glutamine on other measures of ARIE, weight, symptom burden measure assessed by the MD Anderson Symptom Inventory (MDASI-HN) questionnaire and the toxicity profile of glutamine. Results At the time of interim analysis, 53 patients were enrolled: 27 in the glutamine arm and 26 in the placebo arm. There was no difference in the incidence of esophagitis in the first 6 weeks of radiotherapy between the glutamine and placebo arms (74% versus 68%; P = 1.00). There were no significant differences between the two arms for time to onset of esophagitis. The duration of ARIE was shorter (6.3 versus 7.1 weeks; P = 0.54) and median weight loss was lower (0.9 kg versus 2.8 kg; p = 0.83) in the glutamine arm versus the placebo arm. The groups differ significantly in core symptom severity (2.1 vs 1.5, p < .03) but not in head and neck specific symptom severity (1.2 vs 1.1, p < .60) nor in symptom interference (2.1 vs 1.7, p < .22). There was no grade 3 or higher adverse event at least possibly related to glutamine. The study was terminated for futility following interim analysis. Conclusion Oral glutamine was not associated with significant improvement in severity of ARIE, weight loss, head and neck specific symptoms or symptom interference compared with placebo in patients with advanced thoracic malignancies receiving radiotherapy to the esophagus.Clinical trial information. NCT01952847, and date of registration is September 30, 2013.
    Keywords:  Advanced cancers; Clinical trial; Esophagitis; Glutamine; Prevention; Radiation to the esophagus; Thoracic malignancies
  12. Am J Surg Pathol. 2021 Feb 08.
      Some hepatocellular adenoma (HCA) subtypes are characterized by different CTNNB1 mutations, leading to different beta-catenin activation levels, hence variable immunostaining patterns of glutamine synthetase (GS) expression, and different risks of malignant transformation. In a retrospective multicentric study of 63 resected inflammatory (n=33) and noninflammatory (n=30) molecularly confirmed CTNNB1-mutated b-(I)HCA, we investigated the predictive potential of 3 known GS patterns as markers for CTNNB1 exon 3, 7/8 mutations. Pattern 1 (diffuse homogenous) allowed recognition of 17/21 exon 3 non-S45 mutated b-(I)HCA. Pattern 2 (diffuse heterogenous) identified all b-(I)HCA harboring exon 3 S45 mutation (20/20). Pattern 3 (focal patchy) distinguished 12/22 b-(I)HCA with exon 7/8 mutations. In exon 3 S45 and 7/8 mutations, both b-HCA and b-IHCA showed a GS+/CD34- rim with diffuse CD34 positivity in the center of the lesion. Interobserver reproducibility was excellent for exon 3 mutations. Comparative analysis of GS patterns with molecular data showed 83% and 80% sensitivity (b-HCA/b-IHCA) and 100% specificity for exon 3 non-S45. For exon 3 S45, sensitivity was 100% for b-(I)HCA, and specificity 93% and 92% (b-HCA/b-IHCA). For exon 7/8, sensitivity was 55% for both subtypes and specificity 100% and 96% (b-HCA/b-IHCA). Preliminary data from 16 preoperative needle biopsies from the same patients suggest that this panel may also be applicable to small samples. In surgically resected HCA, 2 distinct GS patterns can reliably predict CTNNB1 exon 3 mutations, which are relevant because of the higher risk for malignant transformation. The third pattern, although specific, was less sensitive for the identification of exon 7/8 mutation, but the GS+/CD34- rim is a valuable aid to indicate either an exon 3 S45 or exon 7/8 mutation.
  13. Biology (Basel). 2021 Feb 07. pii: 129. [Epub ahead of print]10(2):
      The expression "metabolic reprogramming" has been encountered more and more in the literature since the mid-1990s. It seems to encompass several notions depending on the author, but the lack of a clear definition allows it to be used as a "catch-all" expression. Our first intention is to point out the inconsistencies in the use of the reprogramming terminology for cancer metabolism. The second is to address the over-focus of the role of mutations in metabolic adaptation. With the increased interest in metabolism and, more specifically, in the Warburg effect in cancer research, it seems appropriate to discuss this terminology and related concepts in detail.
    Keywords:  Warburg effect; cancer metabolism; metabolic reprogramming