A Pck1-directed glycogen metabolic program regulates formation and maintenance of memory CD8+ T cells

PCK2 maintains intestinal homeostasis and prevents colitis by protecting antibody-secreting cells from oxidative stress

Maintaining intracellular redox balance is essential for the survival, antibody secretion, and mucosal immune homeostasis of immunoglobulin A (IgA) antibody-secreting cells (ASCs). However, the relationship between mitochondrial metabolic enzymes and the redox balance in ASCs has yet to be comprehensively studied. Our study unveils the pivotal role of mitochondrial enzyme PCK2 in regulating ASCs' redox balance and intestinal homeostasis. We discover that PCK2 loss, whether globally or in B cells, exacerbates dextran sodium sulphate (DSS)-induced colitis due to increased IgA ASC cell death and diminished antibody production. Mechanistically, the absence of PCK2 diverts glutamine into the TCA cycle, leading to heightened TCA flux and excessive mitochondrial reactive oxygen species (mtROS) production. In addition, PCK2 loss reduces glutamine availability for glutathione (GSH) synthesis, resulting in a decrease of total glutathione level. The elevated mtROS and reduced GSH expose ASCs to overwhelming oxidative stress, culminating in cell apoptosis. Crucially, we found that the mitochondria-targeted antioxidant Mitoquinone (Mito-Q) can mitigate the detrimental effects of PCK2 deficiency in IgA ASCs, thereby alleviating colitis in mice. Our findings highlight PCK2 as a key player in IgA ASC survival and provide a potential new target for colitis treatment.

Deficiency of metabolic regulator PKM2 activates the pentose phosphate pathway and generates TCF1+ progenitor CD8+ T cells to improve immunotherapy

TCF1high progenitor CD8+ T cells mediate the efficacy of immunotherapy; however, the mechanisms that govern their generation and maintenance are poorly understood. Here, we show that targeting glycolysis through deletion of pyruvate kinase muscle 2 (PKM2) results in elevated pentose phosphate pathway (PPP) activity, leading to enrichment of a TCF1high progenitor-exhausted-like phenotype and increased responsiveness to PD-1 blockade in vivo. PKM2KO CD8+ T cells showed reduced glycolytic flux, accumulation of glycolytic intermediates and PPP metabolites and increased PPP cycling as determined by 1,2-13C glucose carbon tracing. Small molecule agonism of the PPP without acute glycolytic impairment skewed CD8+ T cells toward a TCF1high population, generated a unique transcriptional landscape and adoptive transfer of agonist-treated CD8+ T cells enhanced tumor control in mice in combination with PD-1 blockade and promoted tumor killing in patient-derived tumor organoids. Our study demonstrates a new metabolic reprogramming that contributes to a progenitor-like T cell state promoting immunotherapy efficacy.

Focusing on CD8+ T-cell phenotypes: improving solid tumor therapy

Vigorous CD8+ T cells play a crucial role in recognizing tumor cells and combating solid tumors. How T cells efficiently recognize and target tumor antigens, and how they maintain the activity in the "rejection" of solid tumor microenvironment, are major concerns. Recent advances in understanding of the immunological trajectory and lifespan of CD8+ T cells have provided guidance for the design of more optimal anti-tumor immunotherapy regimens. Here, we review the newly discovered methods to enhance the function of CD8+ T cells against solid tumors, focusing on optimizing T cell receptor (TCR) expression, improving antigen recognition by engineered T cells, enhancing signal transduction of the TCR-CD3 complex, inducing the homing of polyclonal functional T cells to tumors, reversing T cell exhaustion under chronic antigen stimulation, and reprogramming the energy and metabolic pathways of T cells. We also discuss how to participate in the epigenetic changes of CD8+ T cells to regulate two key indicators of anti-tumor responses, namely effectiveness and persistence.

Immunometabolism in cancer: A journey into innate and adaptive cells

In recent years, mostly spanning the past decade, the concept of immunometabolism has ushered with a novel perspective on carcinogenesis, tumor progression, and tumor response to therapy. It has become clear that the metabolic state of immune cells plays a significant role in shaping their antitumor or protumor activities within the cancer microenvironment. Consequently, the examination of tumor metabolic heterogeneity, including an exploration of immunometabolism, proves indispensable for enhancing prognostic tools and advancing the quest for personalized treatments. Here we have delved into how metabolic reprogramming profoundly influences the acquisition and maintenance of functional states, spanning from effector and cytotoxic profiles to regulatory and immunosuppressive phenotypes in both innate and adaptive immunity. These alterations wield considerable influence over tumor evolution and affect the outcome of cancer. Furthermore, we explore some of the cellular signaling mechanisms that underpin the metabolic and phenotypic flexibility of immune cells in response to external stimuli.

HMGA1 promotes the progression of esophageal squamous cell carcinoma by elevating TKT-mediated upregulation of pentose phosphate pathway

Esophageal squamous cell carcinoma (ESCC) possesses a poor prognosis and treatment outcome. Dysregulated metabolism contributes to unrestricted growth of multiple cancers. However, abnormal metabolism, such as highly activated pentose phosphate pathway (PPP) in the progression of ESCC remains largely unknown. Herein, we report that high-mobility group AT-hook 1 (HMGA1), a structural transcriptional factor involved in chromatin remodeling, promoted the development of ESCC by upregulating the PPP. We found that HMGA1 was highly expressed in ESCC. Elevated HMGA1 promoted the malignant phenotype of ESCC cells. Conditional knockout of HMGA1 markedly reduced 4-nitroquinoline-1-oxide (4NQO)-induced esophageal tumorigenesis in mice. Through the metabolomic analysis and the validation assay, we found that HMGA1 upregulated the non-oxidative PPP. With the transcriptome sequencing, we identified that HMGA1 upregulated the expression of transketolase (TKT), which catalyzes the reversible reaction in non-oxidative PPP to exchange metabolites with glycolytic pathway. HMGA1 knockdown suppressed the PPP by downregulating TKT, resulting in the reduction of nucleotides in ESCC cells. Overexpression of HMGA1 upregulated PPP and promoted the survival of ESCC cells by activating TKT. We further characterized that HMGA1 promoted the transcription of TKT by interacting with and enhancing the binding of transcription factor SP1 to the promoter of TKT. Therapeutics targeting TKT with an inhibitor, oxythiamine, reduced HMGA1-induced ESCC cell proliferation and tumor growth. Together, in this study, we identified a new role of HMGA1 in ESCCs by upregulating TKT-mediated activation of PPP. Our results provided a new insight into the role of HMGA1/TKT/PPP in ESCC tumorigenesis and targeted therapy.

Glycogenolysis-Induced Astrocytic Serping1 Expression Regulates Neuroinflammatory Effects on Hippocampal neuron

The bacterial pathogen, lipopolysaccharide (LPS), elicits microglial response and induces cytokine secretion that subsequently activates astrocytes. Recent findings have indicated that LPS-induced activation of postnatal glial cells has led to alterations in synapse formation in hippocampal and cortical neurons, thereby resulting in a prolonged increased risk for seizure or depression. Nevertheless, its mechanisms remain to be fully elucidated. Cellular metabolism has recently gained recognition as a critical regulatory mechanism for the activation of peripheral immune cells, as it supplies the requisite energy and metabolite for their activation. In the present study, we report that LPS did not change the expression of reported astrocyte-derived synaptogenic genes in the postnatal hippocampus; however, it induced upregulation of astrocytic complement component regulator Serping1 within the postnatal hippocampus. As a regulatory mechanism, activation of glycogen degradation (glycogenolysis) governs the expression of a subset of inflammatory-responsive genes including Serping1 through reactive oxygen species (ROS)-NF-κB axis. Our study further demonstrated that glycogenolysis is implicated in neurotoxic phenotypes of astrocytes, such as impaired neuronal synaptogenesis or cellular toxicity. These findings suggested that activation of glycogenolysis in postnatal astrocytes is an essential metabolic pathway for inducing responses in inflammatory astrocytes.

Immunometabolism of CD8+ T cell differentiation in cancer

CD8+ cytotoxic T lymphocytes (CTLs) are central mediators of tumor immunity and immunotherapies. Upon tumor antigen recognition, CTLs differentiate from naive/memory-like toward terminally exhausted populations with more limited function against tumors. Such differentiation is regulated by both immune signals, including T cell receptors (TCRs), co-stimulation, and cytokines, and metabolism-associated processes. These immune signals shape the metabolic landscape via signaling, transcriptional and post-transcriptional mechanisms, while metabolic processes in turn exert spatiotemporal effects to modulate the strength and duration of immune signaling. Here, we review the bidirectional regulation between immune signals and metabolic processes, including nutrient uptake and intracellular metabolic pathways, in shaping CTL differentiation and exhaustion. We also discuss the mechanisms underlying how specific nutrient sources and metabolite-mediated signaling events orchestrate CTL biology. Understanding how metabolic programs and their interplay with immune signals instruct CTL differentiation and exhaustion is crucial to uncover tumor-immune interactions and design novel immunotherapies.

PCK1-mediated glycogenolysis facilitates ROS clearance and chemotherapy resistance in cervical cancer stem cells

Cervical cancer, one of the most common gynecological cancers, is primarily caused by human papillomavirus (HPV) infection. The development of resistance to chemotherapy is a significant hurdle in treatment. In this study, we investigated the mechanisms underlying chemoresistance in cervical cancer by focusing on the roles of glycogen metabolism and the pentose phosphate pathway (PPP). We employed the cervical cancer cell lines HCC94 and CaSki by manipulating the expression of key enzymes PCK1, PYGL, and GYS1, which are involved in glycogen metabolism, through siRNA transfection. Our analysis included measuring glycogen levels, intermediates of PPP, NADPH/NADP+ ratio, and the ability of cells to clear reactive oxygen species (ROS) using biochemical assays and liquid chromatography-mass spectrometry (LC-MS). Furthermore, we assessed chemoresistance by evaluating cell viability and tumor growth in NSG mice. Our findings revealed that in drug-resistant tumor stem cells, the enzyme PCK1 enhances the phosphorylation of PYGL, leading to increased glycogen breakdown. This process shifts glucose metabolism towards PPP, generating NADPH. This, in turn, facilitates ROS clearance, promotes cell survival, and contributes to the development of chemoresistance. These insights suggest that targeting aberrant glycogen metabolism or PPP could be a promising strategy for overcoming chemoresistance in cervical cancer. Understanding these molecular mechanisms opens new avenues for the development of more effective treatments for this challenging malignancy.

ROS-responsive thermosensitive polypeptide hydrogels for localized drug delivery and improved tumor chemoimmunotherapy

In this study, we developed a ROS-responsive thermosensitive poly(ethylene glycol)-polypeptide hydrogel loaded with a chemotherapeutic drug, doxorubicin (Dox), an antiviral imidazoquinoline, resiquimod (R848), and antibody targeting programmed cell death protein 1 (aPD-1) for local chemoimmunotherapy. The hydrogel demonstrated controllable degradation and sustained drug release behavior according to the concentration of ROS in vitro. Following intratumoral injection into mice bearing B16F10 melanoma, the Dox/R848/aPD-1 co-loaded hydrogel effectively inhibited tumor growth, prolonged animal survival time and promoted anti-tumor immune responses with low systemic toxicity. In the postoperative model, the Dox/R848/aPD-1 co-loaded hydrogel exhibited enhanced tumor recurrence prevention and long-term immune memory effects. Thus, the hydrogel-based local chemoimmunotherapy system demonstrates potential for effective anti-tumor treatment and suppression of tumor recurrence.

DIAMMONIUM GLYCYRRHIZINATE INHIBITED INFLAMMATORY RESPONSE AND MODULATED SERUM METABOLISM IN POLY(I:C)-INDUCED PNEUMONIA MODEL MICE

ABSTRACT

Currently, the coronavirus disease 2019 (COVID-19) is becoming a serious threat to human health worldwide. Therefore, there is a great need to develop effective drugs against viral pneumonia. Diammonium glycyrrhizinate (DG), derived from Glycyrrhiza glabra L., has been demonstrated with significant anti-inflammatory properties. However, the therapeutic effects and mechanisms of DG on pneumonia require further clarification. In this study, mice received intratracheal injection of polyinosinic-polycytidylic acid (poly(I:C)) to induce pneumonia and were treated with DG. First, we evaluated the therapeutic potential of DG on poly(I:C)-induced pneumonia. Second, the anti-inflammatory and antioxidative activities and the impact of DG on the toll-like receptor 3 (TLR3) pathway were investigated. Third, the mechanism of DG was analyzed through untargeted metabolomics techniques. Our results revealed that DG intervention decreased permeability and reduced abnormal lung alterations in poly(I:C)-induced pneumonia model mice. DG intervention also downregulated cytokine levels in bronchoalveolar lavage fluid. Moreover, DG treatment inhibited the activation of TLR3 pathway. Furthermore, untargeted metabolomics analysis revealed that DG intervention could modulate serum metabolites involved in amino and nucleotide sugar metabolism, fructose and mannose metabolism, tyrosine metabolism, and phenylalanine, tyrosine, and tryptophan biosynthesis pathways. In conclusion, our study showed that DG could ameliorate poly(I:C)-induced pneumonia by inactivating the TLR3 pathway and affecting amino and nucleotide sugar, fructose and mannose metabolism, as well as tryptophan, phenylalanine, and tyrosine biosynthesis.

Metabolic heterogeneity in tumor microenvironment - A novel landmark for immunotherapy

The surrounding non-cancer cells and tumor cells that make up the tumor microenvironment (TME) have various metabolic rhythms. TME metabolic heterogeneity is influenced by the intricate network of metabolic control within and between cells. DNA, protein, transport, and microbial levels are important regulators of TME metabolic homeostasis. The effectiveness of immunotherapy is also closely correlated with alterations in TME metabolism. The response of a tumor patient to immunotherapy is influenced by a variety of variables, including intracellular metabolic reprogramming, metabolic interaction between cells, ecological changes within and between tumors, and general dietary preferences. Although immunotherapy and targeted therapy have made great strides, their use in the accurate identification and treatment of tumors still has several limitations. The function of TME metabolic heterogeneity in tumor immunotherapy is summarized in this article. It focuses on how metabolic heterogeneity develops and is regulated as a tumor progresses, the precise molecular mechanisms and potential clinical significance of imbalances in intracellular metabolic homeostasis and intercellular metabolic coupling and interaction, as well as the benefits and drawbacks of targeted metabolism used in conjunction with immunotherapy. This offers insightful knowledge and important implications for individualized tumor patient diagnosis and treatment plans in the future.

GGT5: a potential immunotherapy response inhibitor in gastric cancer by modulating GSH metabolism and sustaining memory CD8+ T cell infiltration

PURPOSE

The variable responses to immunotherapy observed in gastric cancer (GC) patients can be attributed to the intricate nature of the tumor microenvironment. Glutathione (GSH) metabolism significantly influences the initiation and progression of gastric cancer. Consequently, targeting GSH metabolism holds promise for improving the effectiveness of Immune checkpoints inhibitors (ICIs).

METHODS

We investigated 16 genes related to GSH metabolism, sourced from the MSigDB database, using pan-cancer datasets from TCGA. The most representative prognosis-related gene was identified for further analysis. ScRNA-sequencing analysis was used to explore the tumor heterogeneity of GC, and the results were confirmed by  Multiplex immunohistochemistry (mIHC).

RESULTS

Through DEGs, LASSO, univariate and multivariate Cox regression analyses, and survival analysis, we identified GGT5 as the hub gene in GSH metabolism with the potential to promote GC. Combining CIBERSORT, ssGSEA, and scRNA analysis, we constructed the immune architecture of GC. The subpopulations of T cells were isolated, revealing a strong association between GGT5 and memory CD8+ T cells. Furthermore, specimens from 10 GC patients receiving immunotherapy were collected. mIHC was used to assess the expression levels of GGT5 and memory CD8+ T cell markers. Our results established a positive correlation between GGT5 expression, the enrichment of memory CD8+ T cells, and a suboptimal response to immunotherapy.

CONCLUSIONS

Our study identifies GGT5, a hub gene in GSH metabolism, as a potential therapeutic target for inhibiting the response to immunotherapy in GC patients. These findings offer new insights into strategies for optimizing immunotherapy of GC.

Acetyl-CoA carboxylase obstructs CD8+ T cell lipid utilization in the tumor microenvironment

The solid tumor microenvironment (TME) imprints a compromised metabolic state in tumor-infiltrating T cells (TILs), hallmarked by the inability to maintain effective energy synthesis for antitumor function and survival. T cells in the TME must catabolize lipids via mitochondrial fatty acid oxidation (FAO) to supply energy in nutrient stress, and it is established that T cells enriched in FAO are adept at cancer control. However, endogenous TILs and unmodified cellular therapy products fail to sustain bioenergetics in tumors. We reveal that the solid TME imposes perpetual acetyl-coenzyme A (CoA) carboxylase (ACC) activity, invoking lipid biogenesis and storage in TILs that opposes FAO. Using metabolic, lipidomic, and confocal imaging strategies, we find that restricting ACC rewires T cell metabolism, enabling energy maintenance in TME stress. Limiting ACC activity potentiates a gene and phenotypic program indicative of T cell longevity, engendering T cells with increased survival and polyfunctionality, which sustains cancer control.

Cellular metabolism regulates the differentiation and function of T-cell subsets

T cells are an important component of adaptive immunity and protect the host from infectious diseases and cancers. However, uncontrolled T cell immunity may cause autoimmune disorders. In both situations, antigen-specific T cells undergo clonal expansion upon the engagement and activation of antigens. Cellular metabolism is reprogrammed to meet the increase in bioenergetic and biosynthetic demands associated with effector T cell expansion. Metabolites not only serve as building blocks or energy sources to fuel cell growth and expansion but also regulate a broad spectrum of cellular signals that instruct the differentiation of multiple T cell subsets. The realm of immunometabolism research is undergoing swift advancements. Encapsulating all the recent progress within this concise review in not possible. Instead, our objective is to provide a succinct introduction to this swiftly progressing research, concentrating on the metabolic intricacies of three pivotal nutrient classes-lipids, glucose, and amino acids-in T cells. We shed light on recent investigations elucidating the roles of these three groups of metabolites in mediating the metabolic and immune functions of T cells. Moreover, we delve into the prospect of "editing" metabolic pathways within T cells using pharmacological or genetic approaches, with the aim of synergizing this approach with existing immunotherapies and enhancing the efficacy of antitumor and antiinfection immune responses.

Inhibition of Pck1 in intestinal epithelial cells alleviates acute pancreatitis via modulating intestinal homeostasis

Intestinal barrier dysfunction usually occurred in acute pancreatitis (AP) but the mechanism remains unclear. In this study, RNA sequencing of ileum in L-arginine-induced AP mice demonstrated that phosphoenolpyruvate kinase 1 (Pck1) was significantly up-regulated. Increased Pck1 expression in intestinal epithelial cells (IECs) was further validated in ileum of AP mice and duodenum of AP patients. In AP mice, level of Pck1 was positively correlated with pancreatic and ileal histopathological scores, serum amylase activity, and intestinal permeability (serum diamine oxidase (DAO), D-lactate, and endotoxin). In AP patients, level of Pck1 had a positive correlation with Ranson scores, white blood cell count and C-reactive protein. Inhibition of Pck1 by 3-Mercaptopicolinic acid hydrochloride (3-MPA) alleviated pancreatic and ileal injuries in AP mice. AP + 3-MPA mice showed improved intestinal permeability, including less epithelial apoptosis, increased tight junction proteins (TJPs) expression, decreased serum DAO, D-lactate, endotoxin, and FITC-Dextran levels, and reduced bacteria translocation. Lysozyme secreted by Paneth cells and mucin2 (MUC2) secretion in goblet cells were also partly restored in AP + 3-MPA mice. Meanwhile, inhibition of Pck1 improved intestinal immune response during AP, including elevation of M2/M1 macrophages ratio and secretory immunoglobulin A (sIgA) and reduction in neutrophils infiltration. In vitro, administration of 3-MPA dramatically ameliorated inflammation and injuries of epithelial cells in enteroids treated by LPS. In conclusion, inhibition of Pck1 in IECs might alleviate AP via modulating intestinal homeostasis.

Metabolic plasticity of T cell fate decision

ABSTRACT

The efficacy of adaptive immune responses in cancer treatment relies heavily on the state of the T cells. Upon antigen exposure, T cells undergo metabolic reprogramming, leading to the development of functional effectors or memory populations. However, within the tumor microenvironment (TME), metabolic stress impairs CD8 + T cell anti-tumor immunity, resulting in exhausted differentiation. Recent studies suggested that targeting T cell metabolism could offer promising therapeutic opportunities to enhance T cell immunotherapy. In this review, we provide a comprehensive summary of the intrinsic and extrinsic factors necessary for metabolic reprogramming during the development of effector and memory T cells in response to acute and chronic inflammatory conditions. Furthermore, we delved into the different metabolic switches that occur during T cell exhaustion, exploring how prolonged metabolic stress within the TME triggers alterations in cellular metabolism and the epigenetic landscape that contribute to T cell exhaustion, ultimately leading to a persistently exhausted state. Understanding the intricate relationship between T cell metabolism and cancer immunotherapy can lead to the development of novel approaches to improve the efficacy of T cell-based treatments against cancer.

Sustained AhR activity programs memory fate of early effector CD8+ T cells

Identification of mechanisms that program early effector T cells to either terminal effector T (Teff) or memory T (Tm) cells has important implications for protective immunity against infections and cancers. Here, we show that the cytosolic transcription factor aryl hydrocarbon receptor (AhR) is used by early Teff cells to program memory fate. Upon antigen engagement, AhR is rapidly up-regulated via reactive oxygen species signaling in early CD8+ Teff cells, which does not affect the effector response, but is required for memory formation. Mechanistically, activated CD8+ T cells up-regulate HIF-1α to compete with AhR for HIF-1β, leading to the loss of AhR activity in HIF-1αhigh short-lived effector cells, but sustained in HIF-1αlow memory precursor effector cells (MPECs) with the help of autocrine IL-2. AhR then licenses CD8+ MPECs in a quiescent state for memory formation. These findings partially resolve the long-standing issue of how Teff cells are regulated to differentiate into memory cells.

Nutrients: Signal 4 in T cell immunity

T cells are integral in mediating adaptive immunity to infection, autoimmunity, and cancer. Upon immune challenge, T cells exit from a quiescent state, followed by clonal expansion and effector differentiation. These processes are shaped by three established immune signals, namely antigen stimulation (Signal 1), costimulation (Signal 2), and cytokines (Signal 3). Emerging findings reveal that nutrients, including glucose, amino acids, and lipids, are crucial regulators of T cell responses and interplay with Signals 1-3, highlighting nutrients as Signal 4 to license T cell immunity. Here, we first summarize the functional importance of Signal 4 and the underlying mechanisms of nutrient transport, sensing, and signaling in orchestrating T cell activation and quiescence exit. We also discuss the roles of nutrients in programming T cell differentiation and functional fitness and how nutrients can be targeted to improve disease therapy. Understanding how T cells respond to Signal 4 nutrients in microenvironments will provide insights into context-dependent functions of adaptive immunity and therapeutic interventions.

Lithium carbonate revitalizes tumor-reactive CD8+ T cells by shunting lactic acid into mitochondria

The steady flow of lactic acid (LA) from tumor cells to the extracellular space via the monocarboxylate transporter symport system suppresses antitumor T cell immunity. However, LA is a natural energy metabolite that can be oxidized in the mitochondria and could potentially stimulate T cells. Here we show that the lactate-lowering mood stabilizer lithium carbonate (LC) can inhibit LA-mediated CD8+ T cell immunosuppression. Cytoplasmic LA increased the pumping of protons into lysosomes. LC interfered with vacuolar ATPase to block lysosomal acidification and rescue lysosomal diacylglycerol-PKCθ signaling to facilitate monocarboxylate transporter 1 localization to mitochondrial membranes, thus transporting LA into the mitochondria as an energy source for CD8+ T cells. These findings indicate that targeting LA metabolism using LC could support cancer immunotherapy.

Photodynamic Therapy and Adaptive Immunity Induced by Reactive Oxygen Species: Recent Reports

Cancer is one of the most significant causes of death worldwide. Despite the rapid development of modern forms of therapy, results are still unsatisfactory. The prognosis is further worsened by the ability of cancer cells to metastasize. Thus, more effective forms of therapy, such as photodynamic therapy, are constantly being developed. The photodynamic therapeutic regimen involves administering a photosensitizer that selectively accumulates in tumor cells or is present in tumor vasculature prior to irradiation with light at a wavelength corresponding to the photosensitizer absorbance, leading to the generation of reactive oxygen species. Reactive oxygen species are responsible for the direct and indirect destruction of cancer cells. Photodynamically induced local inflammation has been shown to have the ability to activate an adaptive immune system response resulting in the destruction of tumor lesions and the creation of an immune memory. This paper focuses on presenting the latest scientific reports on the specific immune response activated by photodynamic therapy. We present newly discovered mechanisms for the induction of the adaptive response by analyzing its various stages, and the possible difficulties in generating it. We also present the results of research over the past 10 years that have focused on improving the immunological efficacy of photodynamic therapy for improved cancer therapy.

Metabolomic machine learning predictor for diagnosis and prognosis of gastric cancer

Gastric cancer (GC) represents a significant burden of cancer-related mortality worldwide, underscoring an urgent need for the development of early detection strategies and precise postoperative interventions. However, the identification of non-invasive biomarkers for early diagnosis and patient risk stratification remains underexplored. Here, we conduct a targeted metabolomics analysis of 702 plasma samples from multi-center participants to elucidate the GC metabolic reprogramming. Our machine learning analysis reveals a 10-metabolite GC diagnostic model, which is validated in an external test set with a sensitivity of 0.905, outperforming conventional methods leveraging cancer protein markers (sensitivity < 0.40). Additionally, our machine learning-derived prognostic model demonstrates superior performance to traditional models utilizing clinical parameters and effectively stratifies patients into different risk groups to guide precision interventions. Collectively, our findings reveal the metabolic landscape of GC and identify two distinct biomarker panels that enable early detection and prognosis prediction respectively, thus facilitating precision medicine in GC.

Hepatic glycogenesis antagonizes lipogenesis by blocking S1P via UDPG

The identification of mechanisms to store glucose carbon in the form of glycogen rather than fat in hepatocytes has important implications for the prevention of nonalcoholic fatty liver disease (NAFLD) and other chronic metabolic diseases. In this work, we show that glycogenesis uses its intermediate metabolite uridine diphosphate glucose (UDPG) to antagonize lipogenesis, thus steering both mouse and human hepatocytes toward storing glucose carbon as glycogen. The underlying mechanism involves transport of UDPG to the Golgi apparatus, where it binds to site-1 protease (S1P) and inhibits S1P-mediated cleavage of sterol regulatory element-binding proteins (SREBPs), thereby inhibiting lipogenesis in hepatocytes. Consistent with this mechanism, UDPG administration is effective at treating NAFLD in a mouse model and human organoids. These findings indicate a potential opportunity to ameliorate disordered fat metabolism in the liver.

Vitamin B6 Competition in the Tumor Microenvironment Hampers Antitumor Functions of NK Cells

Nutritional factors play crucial roles in immune responses. The tumor-caused nutritional deficiencies are known to affect antitumor immunity. Here, we demonstrate that pancreatic ductal adenocarcinoma (PDAC) cells can suppress NK-cell cytotoxicity by restricting the accessibility of vitamin B6 (VB6). PDAC cells actively consume VB6 to support one-carbon metabolism, and thus tumor cell growth, causing VB6 deprivation in the tumor microenvironment. In comparison, NK cells require VB6 for intracellular glycogen breakdown, which serves as a critical energy source for NK-cell activation. VB6 supplementation in combination with one-carbon metabolism blockage effectively diminishes tumor burden in vivo. Our results expand the understanding of the critical role of micronutrients in regulating cancer progression and antitumor immunity, and open new avenues for developing novel therapeutic strategies against PDAC.

SIGNIFICANCE

The nutrient competition among the different tumor microenvironment components drives tumor growth, immune tolerance, and therapeutic resistance. PDAC cells demand a high amount of VB6, thus competitively causing NK-cell dysfunction. Supplying VB6 with blocking VB6-dependent one-carbon metabolism amplifies the NK-cell antitumor immunity and inhibits tumor growth in PDAC models. This article is featured in Selected Articles from This Issue, p. 5.

Hurdle or thruster: Glucose metabolism of T cells in anti-tumour immunity

Glucose metabolism is essential for the activation, differentiation and function of T cells and proper glucose metabolism is required to maintain effective T cell immunity. Dysregulation of glucose metabolism is a hallmark of cancer, and the tumour microenvironment (TME2) can create metabolic barriers in T cells that inhibit their anti-tumour immune function. Targeting glucose metabolism is a promising approach to improve the capacity of T cells in the TME. The efficacy of common immunotherapies, such as immune checkpoint inhibitors (ICIs3) and adoptive cell transfer (ACT4), can be limited by T-cell function, and the treatment itself can affect T-cell metabolism. Therefore, understanding the relationship between immunotherapy and T cell glucose metabolism helps to achieve more effective anti-tumour therapy. In this review, we provide an overview of T cell glucose metabolism and how T cell metabolic reprogramming in the TME regulates anti-tumour responses, briefly describe the metabolic patterns of T cells during ICI and ACT therapies, which suggest possible synergistic strategies.

Aryl hydrocarbon receptor sulfenylation promotes glycogenolysis and rescues cancer chemoresistance

Elevation of reactive oxygen species (ROS) levels is a general consequence of tumor cells' response to treatment and may cause tumor cell death. Mechanisms by which tumor cells clear fatal ROS, thereby rescuing redox balance and entering a chemoresistant state, remain unclear. Here, we show that cysteine sulfenylation by ROS confers on aryl hydrocarbon receptor (AHR) the ability to dissociate from the heat shock protein 90 complex but to bind to the PPP1R3 family member PPP1R3C of the glycogen complex in drug-treated tumor cells, thus activating glycogen phosphorylase to initiate glycogenolysis and the subsequent pentose phosphate pathway, leading to NADPH production for ROS clearance and chemoresistance formation. We found that basic ROS levels were higher in chemoresistant cells than in chemosensitive cells, guaranteeing the rapid induction of AHR sulfenylation for the clearance of excess ROS. These findings reveal that AHR can act as an ROS sensor to mediate chemoresistance, thus providing a potential strategy to reverse chemoresistance in patients with cancer.

Nrf2 attenuates oxidative stress to mediate the protective effect of ciprofol against cerebral ischemia-reperfusion injury

Neuroinflammation and oxidative stress damage are involved in the pathogenesis of cerebral ischemia-reperfusion injury (CIRI). Ferroptosis emerged as a new player in the regulation of lipid peroxidation processes. This study aimed at exploring the potential involvement of ciprofol on ferroptosis-associated CIRI and subsequent neurological deficits in the mouse model of transient cerebral ischemia and reperfusion. Cerebral ischemia was built in male C57BL/6 J wild-type (WT) and Nrf2-knockout (Nrf2 KO) mice in the manner of middle cerebral artery occlusion (MCAO) followed by reperfusion. Ciprofol improved autonomic behavior, alleviated reactive oxygen species output and ferroptosis-induced neuronal death by nucleus transportation of NFE2 like BZIP transcription factor 2 (Nrf2) and the promotion of heme oxygenase 1 (Ho-1), solute carrier family 7 member 11 (SLC7A11/xCT), and glutathione peroxidase 4 (GPX4). Additionally, ciprofol improved neurological scores and reduced infarct volume, brain water content, and necrotic neurons. Cerebral blood flow in MCAO-treated mice was also improved. Furthermore, absence of Nrf2 abrogated the neuroprotective actions of ciprofol on antioxidant capacity and sensitized neurons to oxidative stress damage. In vitro, the primary-cultured cortical neurons from mice were pre-treated with oxygen-glucose deprivation/reperfusion (OGD/R), followed by ciprofol administration. Ciprofol effectively reversed OGD/R-induced ferroptosis and accelerated transcription of GPX4 and xCT. In conclusion, we investigated the ciprofol-induced inhibition effect of ferroptosis-sheltered neurons from lipid preoxidation in the pathogenesis of CIRI via Nrf2-xCT-GPX4 signaling pathway.

Two-Dimensional-PAGE Coupled with nLC-MS/MS-Based Identification of Differentially Expressed Proteins and Tumorigenic Pathways in MCF7 Breast Cancer Cells Transfected for JTB Protein Silencing

The identification of new cancer-associated genes/proteins, the characterization of their expression variation, the interactomics-based assessment of differentially expressed genes/proteins (DEGs/DEPs), and understanding the tumorigenic pathways and biological processes involved in BC genesis and progression are necessary and possible by the rapid and recent advances in bioinformatics and molecular profiling strategies. Taking into account the opinion of other authors, as well as based on our own team's in vitro studies, we suggest that the human jumping translocation breakpoint (hJTB) protein might be considered as a tumor biomarker for BC and should be studied as a target for BC therapy. In this study, we identify DEPs, carcinogenic pathways, and biological processes associated with JTB silencing, using 2D-PAGE coupled with nano-liquid chromatography tandem mass spectrometry (nLC-MS/MS) proteomics applied to a MCF7 breast cancer cell line, for complementing and completing our previous results based on SDS-PAGE, as well as in-solution proteomics of MCF7 cells transfected for JTB downregulation. The functions of significant DEPs are analyzed using GSEA and KEGG analyses. Almost all DEPs exert pro-tumorigenic effects in the JTBlow condition, sustaining the tumor suppressive function of JTB. Thus, the identified DEPs are involved in several signaling and metabolic pathways that play pro-tumorigenic roles: EMT, ERK/MAPK, PI3K/AKT, Wnt/β-catenin, mTOR, C-MYC, NF-κB, IFN-γ and IFN-α responses, UPR, and glycolysis/gluconeogenesis. These pathways sustain cancer cell growth, adhesion, survival, proliferation, invasion, metastasis, resistance to apoptosis, tight junctions and cytoskeleton reorganization, the maintenance of stemness, metabolic reprogramming, survival in a hostile environment, and sustain a poor clinical outcome. In conclusion, JTB silencing might increase the neoplastic phenotype and behavior of the MCF7 BC cell line. The data is available via ProteomeXchange with the identifier PXD046265.

Nebulized Therapy of Early Orthotopic Lung Cancer by Iron-Based Nanoparticles: Macrophage-Regulated Ferroptosis of Cancer Stem Cells

Cancer stem cells (CSCs) within protumorigenic microlesions are a critical driver in the initiation and progression of early stage lung cancer, where immune cells provide an immunosuppressive niche to strengthen the CSC stemness. As the mutual interactions between CSCs and immune cells are increasingly recognized, regulating the immune cells to identify and effectively eliminate CSCs has recently become one of the most attractive therapeutic options, especially for abundant tumor-associated macrophages (TAMs). Herein, we developed a nebulized nanocatalytic medicine strategy in which iron-based nanoparticle-regulated TAMs effectively target CSC niches and trigger CSC ferroptosis in the early stage of lung cancer. Briefly, the iron-based nanoparticles can effectively accumulate in lung cancer microlesions (minimum 122 μm in diameter) through dextran-mediated TAM targeting by nebulization administration, and as a result, nanoparticle-internalized TAMs can play a predominant role of the iron factory in elevating the iron level surrounding CSC niches and destroying redox equilibrium through downregulating glucose-6-phosphate metabolite following their lysosomal degradation and iron metabolism. The altered microenvironment results in the enhanced sensitivity of CSCs to ferroptosis due to their high expression of the CD44 receptor mediating iron endocytosis. In an orthotopic mouse model of lung cancer, the initiation and progression of early lung cancer are significantly suppressed through ferroptosis-induced stemness reduction of CSCs by nebulization administration. This work presents a nebulized therapeutic strategy for early lung cancer through modulation of communications between TAMs and CSCs, which is expected to be a general approach for regulating primary microlesions and micrometastatic niches of lung cancer.

Metabolic diversity of tumor-infiltrating T cells as target for anti-immune therapeutics

Tumor-infiltrating T cells are promising drug targets to modulate the tumor microenvironment. However, tumor-infiltrating T lymphocytes, as central targets of cancer immunotherapy, show considerable heterogeneity and dynamics across tumor microenvironments and cancer types that may fundamentally influence cancer growth, metastasis, relapse, and response to clinical drugs. The T cell heterogeneity not only refers to the composition of subpopulations but also divergent metabolic states of T cells. Comparing to the diversity of tumor-infiltrating T cell compositions that have been well recognized, the metabolic diversity of T cells deserves more attention for precision immunotherapy. Single-cell sequencing technology enables panoramic stitching of the tumor bulk, partly by showing the metabolic-related gene expression profiles of tumor-infiltrating T cells at a single-cell resolution. Therefore, we here discuss T cell metabolism reprogramming triggered by tumor microenvironment as well as the potential application of metabolic targeting drugs. The tumor-infiltrating T cells metabolic pathway addictions among different cancer types are also addressed in this brief review.

The glucose transporter 2 regulates CD8+ T cell function via environment sensing

T cell activation is associated with a profound and rapid metabolic response to meet increased energy demands for cell division, differentiation and development of effector function. Glucose uptake and engagement of the glycolytic pathway are major checkpoints for this event. Here we show that the low-affinity, concentration-dependent glucose transporter 2 (Glut2) regulates the development of CD8+ T cell effector responses in mice by promoting glucose uptake, glycolysis and glucose storage. Expression of Glut2 is modulated by environmental factors including glucose and oxygen availability and extracellular acidification. Glut2 is highly expressed by circulating, recently primed T cells, allowing efficient glucose uptake and storage. In glucose-deprived inflammatory environments, Glut2 becomes downregulated, thus preventing passive loss of intracellular glucose. Mechanistically, Glut2 expression is regulated by a combination of molecular interactions involving hypoxia-inducible factor-1 alpha, galectin-9 and stomatin. Finally, we show that human T cells also rely on this glucose transporter, thus providing a potential target for therapeutic immunomodulation.

Electrical stimulation facilitates NADPH production in pentose phosphate pathway and exerts an anti-inflammatory effect in macrophages

Macrophages play an important role as effector cells in innate immune system. Meanwhile, macrophages activated in a pro-inflammatory direction alter intracellular metabolism and damage intact tissues by increasing reactive oxygen species (ROS). Electrical stimulation (ES), a predominant physical agent to control metabolism in cells and tissues, has been reported to exert anti-inflammatory effect on immune cells. However, the mechanism underlying the anti-inflammatory effects by ES is unknown. This study aimed to investigate the effect of ES on metabolism in glycolytic-tricarboxylic acid cycle (TCA) cycle and inflammatory responses in macrophages. ES was performed on bone marrow-derived macrophages and followed by a stimulation with LPS. The inflammatory cytokine expression levels were analyzed by real-time polymerase chain reaction and ELISA. ROS production was analyzed by CellRox Green Reagent and metabolites by capillary electrophoresis-mass spectrometry. As a result, ES significantly reduced proinflammatory cytokine expression levels and ROS generation compared to the LPS group and increased glucose-1-phosphate, a metabolite of glycogen. ES also increased intermediate metabolites of the pentose phosphate pathway (PPP); ribulose-5-phosphate, rebose-5 phosphate, and nicotinamide adenine dinucleotide phosphate, a key factor of cellular antioxidation systems, as well as α-Ketoglutarate, an anti-oxidative metabolite in the TCA cycle. Our findings imply that ES enhanced NADPH production with enhancement of PPP, and also decreased oxidative stress and inflammatory responses in macrophages.

Insights into the tumor-stromal-immune cell metabolism cross talk in ovarian cancer

The ovarian cancer tumor microenvironment (TME) consists of a constellation of abundant cellular components, extracellular matrix, and soluble factors. Soluble factors, such as cytokines, chemokines, structural proteins, extracellular vesicles, and metabolites, are critical means of noncontact cellular communication acting as messengers to convey pro- or antitumorigenic signals. Vast advancements have been made in our understanding of how cancer cells adapt their metabolism to meet environmental demands and utilize these adaptations to promote survival, metastasis, and therapeutic resistance. The stromal TME contribution to this metabolic rewiring has been relatively underexplored, particularly in ovarian cancer. Thus, metabolic activity alterations in the TME hold promise for further study and potential therapeutic exploitation. In this review, we focus on the cellular components of the TME with emphasis on 1) metabolic signatures of ovarian cancer; 2) understanding the stromal cell network and their metabolic cross talk with tumor cells; and 3) how stromal and tumor cell metabolites alter intratumoral immune cell metabolism and function. Together, these elements provide insight into the metabolic influence of the TME and emphasize the importance of understanding how metabolic performance drives cancer progression.

State of CD8+ T cells in progression from nonalcoholic steatohepatitis to hepatocellular carcinoma: From pathogenesis to immunotherapy

With the obesity epidemic, nonalcoholic steatohepatitis (NASH) is emerging as the fastest growing potential cause of hepatocellular carcinoma (HCC). NASH has been demonstrated to establish a tumor-prone liver microenvironment where both innate and adaptive immune systems are involved. As the most typical anti-tumor effector, the cell function of CD8+ T cells is remodeled by chronic inflammation, metabolic alteration, lipid toxicity and oxidative stress in the liver microenvironment along the NASH to HCC transition. Unexpectedly, NASH may blunt the effect of immune checkpoint inhibitor therapy against HCC due to the dysregulated CD8+ T cells. Growing evidence has supported that NASH is likely to facilitate the state transition of CD8+ T cells with changes in cell motility, effector function, metabolic reprogramming and gene transcription according to single-cell sequencing. However, the mechanistic insight of CD8+ T cell states in the NASH-driven HCC is not comprehensive. Herein, we focus on the characterization of state phenotypes of CD8+ T cells with both functional and metabolic signatures in NASH-driven fibrosis and HCC. The NASH-specific CD8+ T cells are speculated to mainly have a dualist effect, where its aberrant activated phenotype sustains chronic inflammation in NASH but subsequently triggers its exhaustion in HCC. As the exploration of CD8+ T cells on the distribution and phenotypic shifts will provide a new direction for the intervention strategies against HCC, we also discuss the implications for targeting different phenotypes of CD8+ T cells, shedding light on the personalized immunotherapy for NASH-driven HCC.

Characterizing control of memory CD8 T cell differentiation by BTB-ZF transcription factor Zbtb20

Members of the BTB-ZF transcription factor family regulate the immune system. Our laboratory identified that family member Zbtb20 contributes to the differentiation, recall responses, and metabolism of CD8 T cells. Here, we report a characterization of the transcriptional and epigenetic signatures controlled by Zbtb20 at single-cell resolution during the effector and memory phases of the CD8 T cell response. Without Zbtb20, transcriptional programs associated with memory CD8 T cell formation were up-regulated throughout the CD8 T response. A signature of open chromatin was associated with genes controlling T cell activation, consistent with the known impact on differentiation. In addition, memory CD8 T cells lacking Zbtb20 were characterized by open chromatin regions with overrepresentation of AP-1 transcription factor motifs and elevated RNA- and protein-level expressions of the corresponding AP-1 components. Finally, we describe motifs and genomic annotations from the DNA targets of Zbtb20 in CD8 T cells identified by cleavage under targets and release under nuclease (CUT&RUN). Together, these data establish the transcriptional and epigenetic networks contributing to the control of CD8 T cell responses by Zbtb20.

Effects of altered glycolysis levels on CD8+ T cell activation and function

CD8+ T cells are an important component of the body's adaptive immune response. During viral or intracellular bacterial infections, CD8+ T cells are rapidly activated and differentiated to exert their immune function by producing cytokines. Alterations in the glycolysis of CD8+ T cells have an important effect on their activation and function, while glycolysis is important for CD8+ T cell functional failure and recovery. This paper summarizes the importance of CD8+ T cell glycolysis in the immune system. We discuss the link between glycolysis and CD8+ T cell activation, differentiation, and proliferation, and the effect of altered glycolysis on CD8+ T cell function. In addition, potential molecular targets to enhance and restore the immune function of CD8+ T cells by affecting glycolysis and the link between glycolysis and CD8+ T cell senescence are summarized. This review provides new insights into the relationship between glycolysis and CD8+ T cell function, and proposes novel strategies for immunotherapy by targeting glycolysis.

Augmenting TCR signal strength and ICOS costimulation results in metabolically fit and therapeutically potent human CAR Th17 cells

IL-17-producing antigen-specific human T cells elicit potent antitumor activity in mice. Yet, refinement of this approach is needed to position it for clinical use. While activation signal strength regulates IL-17 production by CD4+ T cells, the degree to which T cell antigen receptor (TCR) and costimulation signal strength influences Th17 immunity remains unknown. We discovered that decreasing TCR/costimulation signal strength by incremental reduction of αCD3/costimulation beads progressively altered Th17 phenotype. Moreover, Th17 cells stimulated with αCD3/inducible costimulator (ICOS) beads produced more IL-17A, IFNγ, IL-2, and IL-22 than those stimulated with αCD3/CD28 beads. Compared with Th17 cells stimulated with the standard, strong signal strength (three beads per T cell), Th17 cells propagated with 30-fold fewer αCD3/ICOS beads were less reliant on glucose and favored the central carbon pathway for bioenergetics, marked by abundant intracellular phosphoenolpyruvate (PEP). Importantly, Th17 cells stimulated with weak αCD3/ICOS beads and redirected with a chimeric antigen receptor that recognizes mesothelin were more effective at clearing human mesothelioma. Less effective CAR Th17 cells generated with high αCD3/ICOS beads were rescued by overexpressing phosphoenolpyruvate carboxykinase 1 (PCK1), a PEP regulator. Thus, Th17 therapy can be improved by using fewer activation beads during manufacturing, a finding that is cost effective and directly translatable to patients.

Lipid metabolism reprogramming of CD8+ T cell and therapeutic implications in cancer

Effector, memory and exhaustion are three phenotypes of CD8⁺ T cell. In tumor microenvironment (TME), metabolism dysfunction of the three should take the blame for immune escape. Against background of CD8⁺ T cell in normal development, multiple determinants in TME, including nutrition competition, PD-1 signals and other cancer- CD8⁺ T cell interaction, cause metabolism reprograming, including failure in energy metabolism and other abnormal lipid metabolism. Further, incompatibility of different CD8⁺ T cell metabolism pattern results in unresponsiveness of immune checkpoint blockade (ICB). Therefore, combination of ICB and drugs aiming at abnormal lipid metabolism provides promising direction to improve cancer therapy.

Cell metabolism-based optimization strategy of CAR-T cell function in cancer therapy

Adoptive cell therapy (ACT) using chimeric antigen receptor (CAR)-modified T cells has revolutionized the field of immune-oncology, showing remarkable efficacy against hematological malignancies. However, its success in solid tumors is limited by factors such as easy recurrence and poor efficacy. The effector function and persistence of CAR-T cells are critical to the success of therapy and are modulated by metabolic and nutrient-sensing mechanisms. Moreover, the immunosuppressive tumor microenvironment (TME), characterized by acidity, hypoxia, nutrient depletion, and metabolite accumulation caused by the high metabolic demands of tumor cells, can lead to T cell "exhaustion" and compromise the efficacy of CAR-T cells. In this review, we outline the metabolic characteristics of T cells at different stages of differentiation and summarize how these metabolic programs may be disrupted in the TME. We also discuss potential metabolic approaches to improve the efficacy and persistence of CAR-T cells, providing a new strategy for the clinical application of CAR-T cell therapy.

Phosphoenolpyruvate carboxykinases as emerging targets in cancer therapy

Metabolic reprogramming is commonly accompanied by alterations in the expression of metabolic enzymes. These metabolic enzymes not only catalyze the intracellular metabolic reaction, but also participate in a series of molecular events to regulate tumor initiation and development. Thus, these enzymes may act as promising therapeutic targets for tumor management. Phosphoenolpyruvate carboxykinases (PCKs) are the key enzymes involved in gluconeogenesis, which mediates the conversion of oxaloacetate into phosphoenolpyruvate. Two isoforms of PCK, namely cytosolic PCK1 and mitochondrial PCK2, has been found. PCK not only participates in the metabolic adaptation, but also regulates immune response and signaling pathways for tumor progression. In this review, we discussed the regulatory mechanisms of PCKs expression including transcription and post-translational modification. We also summarized the function of PCKs in tumor progression in different cellular contexts and explores its role in developing promising therapeutic opportunities.

PCK1 activates oncogenic autophagy via down-regulation Serine phosphorylation of UBAP2L and antagonizes colorectal cancer growth

Phosphoenolpyruvate carboxykinase 1 (PCK1) is the rate-limiting enzyme in gluconeogenesis. PCK1 is considered an anti-oncogene in several human cancers. In this study, we aimed to determine the functions of PCK1 in colorectal cancer (CRC). PCK1 expression in CRC tissues was tested by western blot and immunohistochemistry analyses and associations of PCK1 level with clinicopathological characteristics and disease survival evaluated. Further, we studied the effect of PCK1 on CRC cell proliferation and the underlying mechanisms. Our results show that PCK1 is expressed at significantly lower levels in CRC than in control tissues. High PCK1 expression was correlated with smaller tumor diameter and less bowel wall invasion (T stage). Overexpression and knockdown experiments demonstrated that PCK1 inhibits CRC cell growth both in vitro and in vivo. Mechanistically, PCK1 antagonizes CRC growth via inactivating UBAP2L phosphorylation at serine 454 and enhancing autophagy. Overall, our findings reveal a novel molecular mechanism involving PCK1 and autophagy, and highlight PCK1 as a promising candidate therapeutic target in CRC.

Metabolic challenges and interventions in CAR T cell therapy

Chimeric antigen receptor (CAR) T cells have achieved true clinical success in treating hematological malignancy patients, laying the foundation of CAR T cells as a new pillar of cancer therapy. Although these promising effects have generated strong interest in expanding the treatment of CAR T cells to solid tumors, reproducible demonstration of clinical efficacy in the setting of solid tumors has remained challenging to date. Here, we review how metabolic stress and signaling in the tumor microenvironment, including intrinsic determinants of response to CAR T cell therapy and extrinsic obstacles, restrict the efficacy of CAR T cell therapy in cancer treatment. In addition, we discuss the use of novel approaches to target and rewire metabolic programming for CAR T cell manufacturing. Last, we summarize strategies that aim to improve the metabolic adaptability of CAR T cells to enhance their potency in mounting antitumor responses and survival within the tumor microenvironment.

Immunological and metabolic characteristics of the Omicron variants infection

The Omicron variants of SARS-CoV-2, primarily authenticated in November 2021 in South Africa, has initiated the 5th wave of global pandemics. Here, we systemically examined immunological and metabolic characteristics of Omicron variants infection. We found Omicron resisted to neutralizing antibody targeting receptor binding domain (RBD) of wildtype SARS-CoV-2. Omicron could hardly be neutralized by sera of Corona Virus Disease 2019 (COVID-19) convalescents infected with the Delta variant. Through mass spectrometry on MHC-bound peptidomes, we found that the spike protein of the Omicron variants could generate additional CD8 + T cell epitopes, compared with Delta. These epitopes could induce robust CD8 + T cell responses. Moreover, we found booster vaccination increased the cross-memory CD8 + T cell responses against Omicron. Metabolic regulome analysis of Omicron-specific T cell showed a metabolic profile that promoted the response of memory T cells. Consistently, a greater fraction of memory CD8 + T cells existed in Omicron stimulated peripheral blood mononuclear cells (PBMCs). In addition, CD147 was also a receptor for the Omicron variants, and CD147 antibody inhibited infection of Omicron. CD147-mediated Omicron infection in a human CD147 transgenic mouse model induced exudative alveolar pneumonia. Taken together, our data suggested that vaccination booster and receptor blocking antibody are two effective strategies against Omicron.

Manipulation of metabolic pathways to promote stem-like and memory T cell phenotypes for immunotherapy

Utilizing the immune system's capacity to recognize and kill tumor cells has revolutionized cancer therapy in recent decades. Phenotypic study of antitumor T cells supports the principle that superior tumor control is achieved by cells with more long-lived memory or stem-like properties as compared to terminally differentiated effector cells. In this Mini-Review, we explore recent advances in profiling the different metabolic programs that both generate and define subsets of memory T cells. We additionally discuss new experimental approaches that aim to maximize the durability and sustained antitumor response associated with memory T cells within the unique immunosuppressive conditions of the tumor microenvironment, such as engineered attempts to overcome hypoxia-induced changes in mitochondrial function, the inhibitory effects of tumor metabolites, and exploitation of more recently-defined metabolic pathways controlling T cell memory fate such as glycogen metabolism.

Ammonia detoxification promotes CD8+ T cell memory development by urea and citrulline cycles

Amino acid metabolism is essential for cell survival, while the byproduct ammonia is toxic and can injure cellular longevity. Here we show that CD8⁺ memory T (T_M) cells mobilize the carbamoyl phosphate (CP) metabolic pathway to clear ammonia, thus promoting memory development. CD8⁺ T_M cells use β-hydroxybutyrylation to upregulate CP synthetase 1 and trigger the CP metabolic cascade to form arginine in the cytosol. This cytosolic arginine is then translocated into the mitochondria where it is split by arginase 2 to urea and ornithine. Cytosolic arginine is also converted to nitric oxide and citrulline by nitric oxide synthases. Thus, both the urea and citrulline cycles are employed by CD8⁺ T cells to clear ammonia and enable memory development. This ammonia clearance machinery might be targeted to improve T cell-based cancer immunotherapies.

Stress-Mediated Attenuation of Translation Undermines T-cell Activity in Cancer

Protein synthesis supports robust immune responses. Nutrient competition and global cell stressors in the tumor microenvironment (TME) may impact protein translation in T cells and antitumor immunity. Using human and mouse tumors, we demonstrated here that protein translation in T cells is repressed in solid tumors. Reduced glucose availability to T cells in the TME led to activation of the unfolded protein response (UPR) element eIF2α (eukaryotic translation initiation factor 2 alpha). Genetic mouse models revealed that translation attenuation mediated by activated p-eIF2α undermines the ability of T cells to suppress tumor growth. Reprograming T-cell metabolism was able to alleviate p-eIF2α accumulation and translational attenuation in the TME, allowing for sustained protein translation. Metabolic and pharmacological approaches showed that proteasome activity mitigates induction of p-eIF2α to support optimal antitumor T-cell function, protecting from translation attenuation and enabling prolonged cytokine synthesis in solid tumors. Together, these data identify a new therapeutic avenue to fuel the efficacy of tumor immunotherapy.

SIGNIFICANCE

Proteasome function is a necessary cellular component for endowing T cells with tumor killing capacity by mitigating translation attenuation resulting from the unfolded protein response induced by stress in the tumor microenvironment.

Tumor Microenvironment Immunosuppression: A Roadblock to CAR T-Cell Advancement in Solid Tumors

Chimeric antigen receptor (CAR) T cells are an exciting advancement in cancer immunotherapy, with striking success in hematological cancers. However, in solid tumors, the unique immunosuppressive elements of the tumor microenvironment (TME) contribute to the failure of CAR T cells. This review discusses the cell populations, cytokine/chemokine profile, and metabolic immunosuppressive elements of the TME. This immunosuppressive TME causes CAR T-cell exhaustion and influences failure of CAR T cells to successfully infiltrate solid tumors. Recent advances in CAR T-cell development, which seek to overcome aspects of the TME immunosuppression, are also reviewed. Novel discoveries overcoming immunosuppressive limitations of the TME may lead to the success of CAR T cells in solid tumors.

CD8+ T cell metabolic rewiring defined by scRNA-seq identifies a critical role of ASNS expression dynamics in T cell differentiation

T cells dynamically rewire their metabolism during an immune response. We applied single-cell RNA sequencing to CD8⁺ T cells activated and differentiated in vitro in physiological medium to resolve these metabolic dynamics. We identify a differential time-dependent reliance of activating T cells on the synthesis versus uptake of various non-essential amino acids, which we corroborate with functional assays. We also identify metabolic genes that potentially dictate the outcome of T cell differentiation, by ranking them based on their expression dynamics. Among them, we find asparagine synthetase (Asns), whose expression peaks for effector T cells and decays toward memory formation. Disrupting these expression dynamics by ASNS overexpression promotes an effector phenotype, enhancing the anti-tumor response of adoptively transferred CD8⁺ T cells in a mouse melanoma model. We thus provide a resource of dynamic expression changes during CD8⁺ T cell activation and differentiation, and identify ASNS expression dynamics as a modulator of CD8⁺ T cell differentiation.

Reprogramming T-Cell Metabolism for Better Anti-Tumor Immunity

T cells play central roles in the anti-tumor immunity, whose activation and differentiation are profoundly regulated by intrinsic metabolic reprogramming. Emerging evidence has revealed that metabolic processes of T cells are generally altered by tumor cells or tumor released factors, leading to crippled anti-tumor immunity. Therefore, better understanding of T cell metabolic mechanism is crucial in developing the next generation of T cell-based anti-tumor immunotherapeutics. In this review, we discuss how metabolic pathways affect T cells to exert their anti-tumor effects and how to remodel the metabolic programs to improve T cell-mediated anti-tumor immune responses. We emphasize that glycolysis, carboxylic acid cycle, fatty acid oxidation, cholesterol metabolism, amino acid metabolism, and nucleotide metabolism work together to tune tumor-reactive T-cell activation and proliferation.