Glutamine blockade induces divergent metabolic programs to overcome tumor immune evasion

CCL2 Expression in Tumor Cells and Tumor-Infiltrating Immune Cells Shows Divergent Prognostic Potential for Bladder Cancer Patients Depending on Lymph Node Stage

Bladder cancer (BCa) is the ninth most commonly diagnosed cancer worldwide. Although there are several well-established molecular and immunological classifications, markers for tumor cells and immune cells that are associated with prognosis are still needed. The chemokine CC motif ligand 2 (CCL2) could be such a marker. We analyzed the expression of CCL2 by immunohistochemistry (IHC) in 168 muscle invasive BCa samples using a tissue microarray. Application of a single cut-off for the staining status of tumor cells (TCs; positive vs. negative) and immune cells (ICs; ≤6% of ICs vs. >6% of ICs) revealed 57 cases (33.9%) and 70 cases (41.7%) with CCL2-positive TCs or ICs, respectively. IHC results were correlated with clinicopathological and survival data. Positive CCL2 staining in TCs was associated with shorter overall survival (OS), disease-specific survival (DSS), and relapse-free survival (RFS) (p = 0.004, p = 0.036, and p = 0.047; log rank test) and appeared to be an independent prognostic factor for OS (RR = 1.70; p = 0.007; multivariate Cox’s regression analysis). In contrast, positive CCL2 staining in the ICs was associated with longer OS, DSS, and RFS (p = 0.032, p = 0.001, and p = 0.001; log rank test) and appeared to be an independent prognostic factor for DSS (RR = 1.77; p = 0.031; multivariate Cox’s regression analysis). Most interestingly, after separating the patients according to their lymph node status (N0 vs. N1+2), CCL2 staining in the ICs was differentially associated with prognosis. In the N0 group, CCL2 positivity in the ICs was a positive independent prognostic factor for OS (RR = 1.99; p = 0.014), DSS (RR = 3.17; p = 0.002), and RFS (RR = 3.10; p = 0.002), whereas in the N1+2 group, CCL2 positivity was a negative independent factor for OS (RR = 3.44; p = 0.019)) and RFS (RR = 4.47; p = 0.010; all multivariate Cox’s regression analyses). In summary, CCL2 positivity in TCs is a negative prognostic factor for OS, and CCL2 can mark ICs that are differentially associated with prognosis depending on the nodal stage of BCa patients. Therefore, CCL2 staining of TCs and ICs is suggested as a prognostic biomarker for BCa patients.

The tumor microenvironment as a metabolic barrier to effector T cells and immunotherapy

Breakthroughs in anti-tumor immunity have led to unprecedented advances in immunotherapy, yet it is now clear that the tumor microenvironment (TME) restrains immunity. T cells must substantially increase nutrient uptake to mount a proper immune response and failure to obtain sufficient nutrients or engage the appropriate metabolic pathways can alter or prevent effector T cell differentiation and function. The TME, however, can be metabolically hostile due to insufficient vascular exchange and cancer cell metabolism that leads to hypoxia, depletion of nutrients, and accumulation of waste products. Further, inhibitory receptors present in the TME can inhibit T cell metabolism and alter T cell signaling both directly and through release of extracellular vesicles such as exosomes. This review will discuss the metabolic changes that drive T cells into different stages of their development and how the TME imposes barriers to the metabolism and activity of tumor infiltrating lymphocytes.

The heterocyclic compound Tempol inhibits the growth of cancer cells by interfering with glutamine metabolism

Tempol (4-hydroxy-2,2,6,6-Tetramethylpiperidine-1-oxyl, TPL), a nitroxide compound, inhibits proliferation and increases the vulnerability of cancer cells to apoptosis induced by cytotoxic agents. However, the molecular mechanism of TPL inhibiting cancer cell proliferation has not been fully understood. In this study, we evaluated the metabolic effect of TPL on cancer cells and explored its cancer therapeutic potential. Extracellular flow assays showed that TPL inhibited cellular basal and maximal oxygen consumption rates of mitochondrial. ¹³C metabolic flux analysis showed that TPL treatment had minimal effect on glycolysis. However, we found that TPL inhibits glutamine metabolism by interfering with the oxidative tricarboxylic acid cycle (TCA) process and reductive glutamine process. We found that the inhibitory effect of TPL on metabolism occurs mainly on the step from citrate to α-ketoglutarate or vice versa. We also found that activity of isocitrate dehydrogenase IDH1 and IDH2, the key enzymes in TCA, were inhibited by TPL treatment. In xenograft mouse model, TPL treatment reduced tumor growth by inhibiting cellular proliferation of xenograft tumors. Thus, we provided a mechanism of TPL inhibiting cancer cell proliferation by interfering with glutamine utilization that is important for survival and proliferation of cancer cells. The study may help the development of a therapeutic strategy of TPL combined with other anticancer medicines.

mTOR signaling at the crossroads of environmental signals and T-cell fate decisions

The evolutionarily conserved serine/threonine kinase mTOR (mechanistic target of rapamycin) forms the distinct protein complexes mTORC1 and mTORC2 and integrates signals from the environment to coordinate downstream signaling events and various cellular processes. T cells rely on mTOR activity for their development and to establish their homeostasis and functional fitness. Here, we review recent progress in our understanding of the upstream signaling and downstream targets of mTOR. We also provide an updated overview of the roles of mTOR in T-cell development, homeostasis, activation, and effector-cell fate decisions, as well as its important impacts on the suppressive activity of regulatory T cells. Moreover, we summarize the emerging roles of mTOR in T-cell exhaustion and transdifferentiation. A better understanding of the contribution of mTOR to T-cell fate decisions will ultimately aid in the therapeutic targeting of mTOR in human disease.

Immunometabolism: From basic mechanisms to translation

Immunometabolism has emerged as a major mechanism central to adaptive and innate immune regulation. From early observations that inflammatory cytokines were induced in obese adipose tissue and that these cytokines contributed to metabolic disease, it was clear that metabolism and the immunological state are inextricably linked. With a second research wave arising from studies in cancer metabolism to also study the intrinsic metabolic pathways of immune cells themselves and how those pathways influence cell fate and function, immunometabolism is a rapidly maturing area of research. Several key themes and goals drive the field. There is abundant evidence that metabolic pathways are closely tied to cell signaling and differentiation which leads different subsets of immune cells to adopt unique metabolic programs specific to their state and environment. In this way, metabolic signaling drives cell fate. It is also apparent that microenvironment greatly influences cell metabolism. Immune cells adopt programs specific for the tissues where they infiltrate and reside. Ultimately, a central goal of the field is to apply immunometabolism findings to the discovery of novel therapeutic strategies in a wide range of diseases, including cancer, autoimmunity, and metabolic syndrome. This review summarizes these facets of immunometabolism and highlights opportunities for clinical translation.

Metabolic Regulation of Myeloid-Derived Suppressor Cell Function in Cancer

Myeloid-derived suppressor cells (MDSCs) are a group of immunosuppressive cells that play crucial roles in promoting tumor growth and protecting tumors from immune recognition in tumor-bearing mice and cancer patients. Recently, it has been shown that the metabolic activity of MDSCs plays an important role in the regulation of their inhibitory function, especially in the processes of tumor occurrence and development. The MDSC metabolism, such as glycolysis, fatty acid oxidation and amino acid metabolism, is rewired in the tumor microenvironment (TME), which enhances the immunosuppressive activity, resulting in effector T cell apoptosis and suppressive cell proliferation. Herein, we summarized the recent progress in the metabolic reprogramming and immunosuppressive function of MDSCs during tumorigenesis.

Metabolic reprogramming and cancer progression

Metabolic reprogramming is a hallmark of malignancy. As our understanding of the complexity of tumor biology increases, so does our appreciation of the complexity of tumor metabolism. Metabolic heterogeneity among human tumors poses a challenge to developing therapies that exploit metabolic vulnerabilities. Recent work also demonstrates that the metabolic properties and preferences of a tumor change during cancer progression. This produces distinct sets of vulnerabilities between primary tumors and metastatic cancer, even in the same patient or experimental model. We review emerging concepts about metabolic reprogramming in cancer, with particular attention on why metabolic properties evolve during cancer progression and how this information might be used to develop better therapeutic strategies.

Copper-Enriched Prussian Blue Nanomedicine for In Situ Disulfiram Toxification and Photothermal Antitumor Amplification

In situ toxification of less toxic substance for the generation of effective anticarcinogens at the specific tumor tissue has been a novel paradigm for combating cancer. Significant efforts have been recently dedicated to turning clinical-approved drugs into anticancer agents in specific tumor microenvironment by chemical reactions. Herein, a hollow mesoporous Prussian blue (HMPB)-based therapeutic nanoplatform, denoted as DSF@PVP/Cu-HMPB, is constructed by encapsulating alcohol-abuse drug disulfiram (DSF) into the copper-enriched and polyvinylpyrrolidone (PVP)-decorated HMPB nanoparticles to achieve in situ chemical reaction-activated and hyperthermia-amplified chemotherapy of DSF. Upon tumor accumulation of DSF@PVP/Cu-HMPB, the endogenous mild acidity in tumor condition triggers the biodegradation of the HMPB nanoparticle and the concurrent co-releases of DSF and Cu²⁺ , thus forming cytotoxic bis(N,N-diethyl dithiocarbamato)copper(II) complexes (CuL₂ ) via DSF-Cu²⁺ chelating reaction. Moreover, by the intrinsic photothermal-conversion effect of PVP/Cu-HMPBs, the anticancer effect of DSF is augmented by the hyperthermia generated upon near-infrared irradiation, thus inducing remarkable cell apoptosis in vitro and tumor elimination in vivo on both subcutaneous and orthotopic tumor-bearing models. This strategy of in situ drug transition by chemical chelation reaction and photothermal-augmentation provides a promising paradigm for designing novel cancer-therapeutic nanoplatforms.

Dietary restriction of amino acids for Cancer therapy

Biosyntheses of proteins, nucleotides and fatty acids, are essential for the malignant proliferation and survival of cancer cells. Cumulating research findings show that amino acid restrictions are potential strategies for cancer interventions. Meanwhile, dietary strategies are popular among cancer patients. However, there is still lacking solid rationale to clarify what is the best strategy, why and how it is. Here, integrated analyses and comprehensive summaries for the abundances, signalling and functions of amino acids in proteomes, metabolism, immunity and food compositions, suggest that, intermittent dietary lysine restriction with normal maize as an intermittent staple food for days or weeks, might have the value and potential for cancer prevention or therapy. Moreover, dietary supplements were also discussed for cancer cachexia including dietary immunomodulatory.

Metabolic determinants of lupus pathogenesis

The metabolism of healthy murine and more recently human immune cells has been investigated with an increasing amount of details. These studies have revealed the challenges presented by immune cells to respond rapidly to a wide variety of triggers by adjusting the amount, type, and utilization of the nutrients they import. A concept has emerged that cellular metabolic programs regulate the size of the immune response and the plasticity of its effector functions. This has generated a lot of enthusiasm with the prediction that cellular metabolism could be manipulated to either enhance or limit an immune response. In support of this hypothesis, studies in animal models as well as human subjects have shown that the dysregulation of the immune system in autoimmune diseases is associated with a skewing of the immunometabolic programs. These studies have been mostly conducted on autoimmune CD4⁺ T cells, with the metabolism of other immune cells in autoimmune settings still being understudied. Here we discuss systemic metabolism as well as cellular immunometabolism as novel tools to decipher fundamental mechanisms of autoimmunity. We review the contribution of each major metabolic pathway to autoimmune diseases, with a focus on systemic lupus erythematosus (SLE), with the relevant translational opportunities, existing or predicted from results obtained with healthy immune cells. Finally, we review how targeting metabolic programs may present novel therapeutic venues.

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.

Nitrogen Metabolism in Cancer and Immunity

As one of the fundamental requirements for cell growth and proliferation, nitrogen acquisition and utilization must be tightly regulated. Nitrogen can be generated from amino acids (AAs) and utilized for biosynthetic processes through transamination and deamination reactions. Importantly, limitations of nitrogen availability in cells can disrupt the synthesis of proteins, nucleic acids, and other important nitrogen-containing compounds. Rewiring cellular metabolism to support anabolic processes is a feature common to both cancer and proliferating immune cells. In this review, we discuss how nitrogen is utilized in biosynthetic pathways and highlight different metabolic and oncogenic programs that alter the flow of nitrogen to sustain biomass production and growth, an important emerging feature of cancer and immune cell proliferation.

Analysing central metabolism in ultra-high resolution: At the crossroads of carbon and nitrogen

BACKGROUND

Cancer cell metabolism can be characterised by adaptive metabolic alterations, which support abnormal proliferative cell growth with high energetic demand. De novo nucleotide biosynthesis is essential for providing nucleotides for RNA and DNA synthesis, and drugs targeting this biosynthetic pathway have proven to be effective anticancer therapeutics. Nevertheless, cancers are often able to circumvent chemotherapeutic interventions and become therapy resistant. Our understanding of the changing metabolic profile of the cancer cell and the mode of action of therapeutics is dependent on technological advances in biochemical analysis.

SCOPE OF REVIEW

This review begins with information about carbon- and nitrogen-donating pathways to build purine and pyrimidine moieties in the course of nucleotide biosynthesis. We discuss the application of stable isotope resolved metabolomics to investigate the dynamics of cancer cell metabolism and outline the benefits of high-resolution accurate mass spectrometry, which enables multiple tracer studies.

CONCLUSION

With the technological advances in mass spectrometry that allow for the analysis of the metabolome in high resolution, the application of stable isotope resolved metabolomics has become an important technique in the investigation of biological processes. The literature in the area of isotope labelling is dominated by 13C tracer studies. Metabolic pathways have to be considered as complex interconnected networks and should be investigated as such. Moving forward to simultaneous tracing of different stable isotopes will help elucidate the interplay between carbon and nitrogen flow and the dynamics of de novo nucleotide biosynthesis within the cell.

Advances into understanding metabolites as signaling molecules in cancer progression

Recent years have seen a great expansion in our knowledge of the roles that metabolites play in cellular signaling. Structural data have provided crucial insights into mechanisms through which amino acids are sensed. New nutrient-coupled protein and RNA modifications have been identified and characterized. A growing list of functions has been ascribed to metabolic regulation of modifications such as acetylation, methylation, and glycosylation. A current challenge lies in developing an integrated understanding of the roles that metabolic signaling mechanisms play in physiology and disease, which will inform the design of strategies to target such mechanisms. In this brief article, we review recent advances in metabolic signaling through post-translational modification during cancer progression, to provide a framework for understanding signaling roles of metabolites in the context of cancer biology and illuminate areas for future investigation.

Targeting glutamine metabolism slows soft tissue sarcoma growth

Tumour cells frequently utilize glutamine to meet bioenergetic and biosynthetic demands of rapid cell growth. However, glutamine dependence can be highly variable between in vitro and in vivo settings, based on surrounding microenvironments and complex adaptive responses to glutamine deprivation. Soft tissue sarcomas (STSs) are mesenchymal tumours where cytotoxic chemotherapy remains the primary approach for metastatic or unresectable disease. Therefore, it is critical to identify alternate therapies to improve patient outcomes. Using autochthonous STS murine models and unbiased metabolomics, we demonstrate that glutamine metabolism supports sarcomagenesis. STS subtypes expressing elevated glutaminase (GLS) levels are highly sensitive to glutamine starvation. In contrast to previous studies, treatment of autochthonous tumour-bearing animals with Telaglenastat (CB-839), an orally bioavailable GLS inhibitor, successfully inhibits undifferentiated pleomorphic sarcoma (UPS) tumour growth. We reveal glutamine metabolism as critical for sarcomagenesis, with CB-839 exhibiting potent therapeutic potential.

Glutamine is an energetic source required for the proliferation of cancer cells. Here, the authors show that soft tissue sarcomas expressing high levels of glutaminase (GLS) are particularly sensitive to glutamine starvation and GLS inhibition in tumour-bearing allograft and autochthonous mouse models.

Tumor hypermetabolism confers resistance to immunotherapy

Advances in our understanding of tumor immune biology and development of cancer immunotherapies have led to improved outcomes for patients that suffer from aggressive cancers such as metastatic melanoma. Despite these advances, a significant proportion of patients still fail to benefit, and as a result, attention has shifted to understanding how cancer cells escape immune destruction. Of particular interest is the metabolic landscape of the tumor microenvironment, as recent studies have demonstrated how both competition for essential nutrients and depletion of specific amino acids can promote T cell dysfunction. Here, we will discuss the major energetic pathways engaged by both T cells and cancer cells, metabolic substrates present in the tumor microenvironment, and emerging therapeutic strategies that seek to improve T cell metabolic fitness and bolster the antitumor immune response.

Is Lactate an Oncometabolite? Evidence Supporting a Role for Lactate in the Regulation of Transcriptional Activity of Cancer-Related Genes in MCF7 Breast Cancer Cells

Lactate is a ubiquitous molecule in cancer. In this exploratory study, our aim was to test the hypothesis that lactate could function as an oncometabolite by evaluating whether lactate exposure modifies the expression of oncogenes, or genes encoding transcription factors, cell division, and cell proliferation in MCF7 cells, a human breast cancer cell line. Gene transcription was compared between MCF7 cells incubated in (a) glucose/glutamine-free media (control), (b) glucose-containing media to stimulate endogenous lactate production (replicating some of the original Warburg studies), and (c) glucose-containing media supplemented with L-lactate (10 and 20 mM). We found that both endogenous, glucose-derived lactate and exogenous, lactate supplementation significantly affected the transcription of key oncogenes (MYC, RAS, and PI3KCA), transcription factors (HIF1A and E2F1), tumor suppressors (BRCA1, BRCA2) as well as cell cycle and proliferation genes involved in breast cancer (AKT1, ATM, CCND1, CDK4, CDKN1A, CDK2B) (0.001 < p < 0.05 for all genes). Our findings support the hypothesis that lactate acts as an oncometabolite in MCF7 cells. Further research is necessary on other cell lines and biopsy cultures to show generality of the findings and reveal the mechanisms by which dysregulated lactate metabolism could act as an oncometabolite in carcinogenesis.

Inhibition of glutaminase to reverse fibrosis in iatrogenic laryngotracheal stenosis

OBJECTIVES/HYPOTHESIS

Glutamine metabolism is a critical energy source for iatrogenic laryngotracheal stenosis (iLTS) scar fibroblasts, and glutaminase (GLS) is an essential enzyme converting glutamine to glutamate. We hypothesize that the GLS-specific inhibitor BPTES will block glutaminolysis and reduce iLTS scar fibroblast proliferation, collagen deposition, and fibroblast metabolism in vitro.

STUDY DESIGN

Test-tube Lab Research.

METHODS

Immunohistochemistry of a cricotracheal resection (n = 1) and a normal airway specimen (n = 1) were assessed for GLS expression. GLS expression was assessed in brush biopsies of subglottic/tracheal fibrosis and normal airway from patients with iLTS (n = 6). Fibroblasts were isolated and cultured from biopsies of subglottic/tracheal fibrosis (n = 6). Fibroblast were treated with BPTES and BPTES + dimethyl α-ketoglutarate (DMK), an analogue of the downstream product of GLS. Fibroblast proliferation, gene expression, protein production, and metabolism were assessed in all treatment conditions and compared to control.

RESULTS

GLS was overexpressed in brush biopsies of iLTS scar specimens (P = .029) compared to normal controls. In vitro, BPTES inhibited iLTS scar fibroblast proliferation (P = .007), collagen I (Col I) (P < .0001), collagen III (P = .004), and α-smooth muscle actin (P = .0025) gene expression and protein production (P = .031). Metabolic analysis demonstrated that BPTES reduced glycolytic reserve (P = .007) but had no effects on mitochondrial oxidative phosphorylation. DMK rescued BPTES inhibition of Col I gene expression (P = .0018) and protein production (P = .021).

CONCLUSIONS

GLS is overexpressed in iLTS scar. Blockage of GLS with BPTES significantly inhibits iLTS scar fibroblasts proliferation and function, demonstrating a critical role for GLS in iLTS. Targeting GLS to inhibit glutaminolysis may be a successful strategy to reverse scar formation in the airway.

LEVEL OF EVIDENCE

NA Laryngoscope, 2020.

Transcriptome Analysis Reveals Key Genes and Pathways Associated with Metastasis in Breast Cancer

BACKGROUND

Metastasis is the major cause of death in breast cancer patients. Although the strategies targeting metastasis have promoted survival, the underlying mechanisms still remain unclear. In this study, we used microarray data of primary breast tumor, tumor derived from bone and liver, and skin metastatic tissue, to identify the key genes and pathways that are involved in metastasis in breast cancer.

METHODS

We first calculated the differentially expressed genes (DEGs) between three metastatic tissues and primary tumor tissue, and then used it to perform Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Further, we analyzed the correlation of genes enriched in GO terms and KEGG pathways with survival of breast cancer patients. To identify the key genes and pathways associated with metastasis, we overlapped the DEGs and KEGG pathways. In our in vitro experiments, we knocked down the key gene, ERLIN2, and detected the PI3K expression in tumor cells to evaluate their effect on tumor metastasis.

RESULTS

We identified six genes (ALOX15, COL4A6, LMB13, MTAP, PLA2G4A, TAT) that correlated with survival. Seven key genes (SNRPN, ARNT2, HDGFRP3, ERO1LB, ERLIN2, YBX2, EBF4) and seven signaling pathways (metabolic pathways, phagosome pathway, PI3K-AKT signaling pathway, focal adhesion, ECM-receptor interaction, pancreatic secretion, human papillomavirus infection) associated with metastasis were also identified. Our in vitro experiments revealed that ERLIN2 was highly expressed in MDA-MB231 cells compared to MCF-7 cells. Moreover, knockdown of ERLIN2 increased apoptosis, while inhibiting the proliferation, invasion, and migration ability of breast cancer cells. The PI3K/AKT signaling pathway was also found to be highly expressed in MDA-MB231 cells.

CONCLUSION

Our results reveal the key genes and signaling pathways that contribute to metastasis, and highlight that strategic targeting of ENLIN2 and PI3K/AKT signaling pathways could inhibit metastasis of breast cancer.

Tumor microenvironmental influences on dendritic cell and T cell function: A focus on clinically relevant immunologic and metabolic checkpoints

Cancer immunotherapy is fast becoming one of the most promising means of treating malignant disease. Cancer vaccines, adoptive cell transfer therapies, and immune checkpoint blockade have all shown varying levels of success in the clinical management of several cancer types in recent years. However, despite the clinical benefits often achieved by these regimens, an ongoing problem for many patients is the inherent or acquired resistance of their cancer to immunotherapy. It is now appreciated that dendritic cells and T lymphocytes both play key roles in antitumor immune responses and that the tumor microenvironment presents a number of barriers to the function of these cells that can ultimately limit the success of immunotherapy. In particular, the engagement of several immunologic and metabolic checkpoints within the hostile tumor microenvironment can severely compromise the antitumor functions of these important immune populations. This review highlights work from both preclinical and clinical studies that has shaped our understanding of the tumor microenvironment and its influence on dendritic cell and T cell function. It focuses on clinically relevant targeted and immunotherapeutic strategies that have emerged from these studies in an effort to prevent or overcome immune subversion within the tumor microenvironment. Emphasis is also placed on the potential of next-generation combinatorial regimens that target metabolic and immunologic impediments to dendritic cell and T lymphocyte function as strategies to improve antitumor immune reactivity and the clinical outcome of cancer immunotherapy going forward.