Harnessing Metabolic Reprogramming to Improve Cancer Immunotherapy

From metabolic byproduct to immune modulator: the role of lactate in tumor immune escape

Lactic acid, a key metabolic byproduct within the tumor microenvironment, has garnered significant attention for its role in immune evasion mechanisms. Tumor cells produce and release large amounts of lactic acid into the tumor microenvironment through aberrant glycolysis via the Warburg effect, leading to a drop in pH. Elevated lactic acid levels profoundly suppress proliferation capacity, cytotoxic functions, and migratory abilities of immune effector cells such as macrophages and natural killer cells at the tumor site. Moreover, lactic acid can modulate the expression of surface molecules on immune cells, interfering with their recognition and attack of tumor cells, and it regulates signaling pathways that promote the expansion and enhanced function of immunosuppressive cells like regulatory T cells, thereby fostering immune tolerance within the tumor microenvironment. Current research is actively exploring strategies targeting lactic acid metabolism to ameliorate tumor immune evasion. Key approaches under investigation include inhibiting the activity of critical enzymes in lactic acid production to reduce its synthesis or blocking lactate transporters to alter intracellular and extracellular lactate distribution. These methods hold promise when combined with existing immunotherapies such as immune checkpoint inhibitors and chimeric antigen receptor T-cell therapies to enhance the immune system's ability to eliminate tumor cells. This could pave the way for novel combinatorial treatment strategies in clinical cancer therapy, effectively overcoming tumor immune evasion phenomena, and ultimately improving overall treatment efficacy.

The role of metabolic reprogramming in immune escape of triple-negative breast cancer

Triple-negative breast cancer (TNBC) has become a thorny problem in the treatment of breast cancer because of its high invasiveness, metastasis and recurrence. Although immunotherapy has made important progress in TNBC, immune escape caused by many factors, especially metabolic reprogramming, is still the bottleneck of TNBC immunotherapy. Regrettably, the mechanisms responsible for immune escape remain poorly understood. Exploring the mechanism of TNBC immune escape at the metabolic level provides a target and direction for follow-up targeting or immunotherapy. In this review, we focus on the mechanism that TNBC affects immune cells and interstitial cells through hypoxia, glucose metabolism, lipid metabolism and amino acid metabolism, and changes tumor metabolism and tumor microenvironment. This will help to find new targets and strategies for TNBC immunotherapy.

Deep neural network for discovering metabolism-related biomarkers for lung adenocarcinoma

Introduction

Lung cancer is a major cause of illness and death worldwide. Lung adenocarcinoma (LUAD) is its most common subtype. Metabolite-mRNA interactions play a crucial role in cancer metabolism. Thus, metabolism-related mRNAs are potential targets for cancer therapy.

Methods

This study constructed a network of metabolite-mRNA interactions (MMIs) using four databases. We retrieved mRNAs from the Tumor Genome Atlas (TCGA)-LUAD cohort showing significant expressional changes between tumor and non-tumor tissues and identified metabolism-related differential expression (DE) mRNAs among the MMIs. Candidate mRNAs showing significant contributions to the deep neural network (DNN) model were mined. Using MMIs and the results of function analysis, we created a subnetwork comprising candidate mRNAs and metabolites.

Results

Finally, 10 biomarkers were obtained after survival analysis and validation. Their good prognostic value in LUAD was validated in independent datasets. Their effectiveness was confirmed in the TCGA and an independent Clinical Proteomic Tumor Analysis Consortium (CPTAC) dataset by comparison with traditional machine-learning models.

Conclusion

To summarize, 10 metabolism-related biomarkers were identified, and their prognostic value was confirmed successfully through the MMI network and the DNN model. Our strategy bears implications to pave the way for investigating metabolic biomarkers in other cancers.

GPR81-mediated reprogramming of glucose metabolism contributes to the immune landscape in breast cancer

BACKGROUND

Local tumor microenvironment (TME) plays a crucial role in immunotherapy for breast cancer (BC). Whereas, the molecular mechanism responsible for the crosstalk between BC cells and surrounding immune cells remains unclear. The present study aimed to determine the interplay between GPR81-mediated glucometabolic reprogramming of BC and the immune landscape in TME.

MATERIALS AND METHODS

Immunohistochemistry (IHC) assay was first performed to evaluate the association between GPR81 and the immune landscape. Then, several stable BC cell lines with down-regulated GPR81 expression were established to directly identify the role of GPR81 in glucometabolic reprogramming, and western blotting assay was used to detect the underlying molecular mechanism. Finally, a transwell co-culture system confirmed the crosstalk between glucometabolic regulation mediated by GPR81 in BC and induced immune attenuation.

RESULTS

IHC analysis demonstrated that the representation of infiltrating CD8⁺ T cells and FOXP3⁺ T cells were dramatically higher in BC with a triple negative (TN) subtype in comparison with that with a non-TN subtype (P < 0.001). Additionally, the ratio of infiltrating CD8⁺ to FOXP3⁺ T cells was significantly negatively associated with GPR81 expression in BC with a TN subtype (P < 0.001). Furthermore, GPR81 was found to be substantially correlated with the glycolytic capability (P < 0.001) of BC cells depending on a Hippo-YAP signaling pathway (P < 0.001). In the transwell co-culture system, GPR81-mediated reprogramming of glucose metabolism in BC significantly contributed to a decreased proportion of CD8⁺ T (P < 0.001) and an increased percentage of FOXP3⁺ T (P < 0.001) in the co-cultured lymphocytes.

CONCLUSION

Glucometabolic reprogramming through a GPR81-mediated Hippo-YAP signaling pathway was responsible for the distinct immune landscape in BC. GPR81 was a potential biomarker to stratify patients before immunotherapy to improve BC's clinical prospect.

IL-1RA promotes oral squamous cell carcinoma malignancy through mitochondrial metabolism-mediated EGFR/JNK/SOX2 pathway

BACKGROUND

Interleukin-1 receptor antagonist (IL-1RA), a member of the IL-1 family, has diverse roles in cancer development. However, the role of IL-1RA in oral squamous cell carcinoma (OSCC), in particular the underlying mechanisms, remains to be elucidated.

METHODS

Tumor tissues from OSCC patients were assessed for protein expression by immunohistochemistry. Patient survival was evaluated by Kaplan-Meier curve analysis. Impact of differential IL-1RA expression on cultured OSCC cell lines was assessed in vitro by clonogenic survival, tumorsphere formation, soft agar colony formation, and transwell cell migration and invasion assays. Oxygen consumption rate was measured by Seahorse analyzer or multi-mode plate reader. PCR array was applied to screen human cancer stem cell-related genes, proteome array for phosphorylation status of kinases, and Western blot for protein expression in cultured cells. In vivo tumor growth was investigated by orthotopic xenograft in mice, and protein expression in xenograft tumors assessed by immunohistochemistry.

RESULTS

Clinical analysis revealed that elevated IL-1RA expression in OSCC tumor tissues was associated with increased tumor size and cancer stage, and reduced survival in the patient group receiving adjuvant radiotherapy compared to the patient group without adjuvant radiotherapy. In vitro data supported these observations, showing that overexpression of IL-1RA increased OSCC cell growth, migration/invasion abilities, and resistance to ionizing radiation, whereas knockdown of IL-1RA had largely the opposite effects. Additionally, we identified that EGFR/JNK activation and SOX2 expression were modulated by differential IL-1RA expression downstream of mitochondrial metabolism, with application of mitochondrial complex inhibitors suppressing these pathways. Furthermore, in vivo data revealed that treatment with cisplatin or metformin-a mitochondrial complex inhibitor and conventional therapy for type 2 diabetes-reduced IL-1RA-associated xenograft tumor growth as well as EGFR/JNK activation and SOX2 expression. This inhibitory effect was further augmented by combination treatment with cisplatin and metformin.

CONCLUSIONS

The current study suggests that IL-1RA promoted OSCC malignancy through mitochondrial metabolism-mediated EGFR/JNK activation and SOX2 expression. Inhibition of this mitochondrial metabolic pathway may present a potential therapeutic strategy in OSCC.

Glucose-6-phosphate dehydrogenase: a therapeutic target for ovarian cancer

INTRODUCTION

Ovarian cancer (OC) is a gynecological tumor disease, which is usually diagnosed at an advanced stage and has a poor prognosis. It has been established that the glucose metabolism rate of cancer cells is significantly higher than that of normal cells, and the pentose phosphate pathway (PPP) is an important branch pathway for glucose metabolism. Glucose-6-phosphate dehydrogenase (G6PD) is the key rate-limiting enzyme in the PPP, which plays an important role in the initiation and development of cancer (such as OC), and has been considered as a promisinganti-cancer target.

AREAS COVERED

In this review, based on the structure and biological function of G6PD, recent research on the roles of G6PD in the progression, metastasis, and chemoresistance of OC are summarized and accompanied by proposed molecular mechanisms, which may provide a systematic understanding of targeting G6PD for the treatment of patients with OC.

EXPERT OPINION

Accumulating evidence demonstrates that G6PD is a promising target of cancer. The development of G6PD inhibitors for cancer treatment merits broad application prospects.

Glutamine metabolism-related genes predict prognosis and reshape tumor microenvironment immune characteristics in diffuse gliomas

Background

Diffuse gliomas possess a kind of malignant brain tumor with high mortality. Glutamine represents the most abundant and versatile amino acid in the body. Glutamine not only plays an important role in cell metabolism but also involves in cell survival and malignancies progression. Recent studies indicate that glutamine could also affect the metabolism of immune cells in the tumor microenvironment (TME).

Materials and methods

The transcriptome data and clinicopathological information of patients with glioma were acquired from TCGA, CGGA, and West China Hospital (WCH). The glutamine metabolism-related genes (GMRGs) were retrieved from the Molecular Signature Database. Consensus clustering analysis was used to discover expression patterns of GMRGs, and glutamine metabolism risk scores (GMRSs) were established to model tumor aggressiveness-related GMRG expression signature. ESTIMATE and CIBERSORTx were applied to depict the TME immune landscape. The tumor immunological phenotype analysis and TIDE were utilized for predicting the therapeutic response of immunotherapy.

Results

A total of 106 GMRGs were retrieved. Two distinct clusters were established by consensus clustering analysis, which showed a close association with the IDH mutational status of gliomas. In both IDH-mutant and IDH-wildtype gliomas, cluster 2 had significantly shorter overall survival compared with cluster 1, and the differentially expressed genes between the two clusters enriched in pathways related to malignant transformation as well as immunity. In silico TME analysis of the two IDH subtypes revealed not only significantly different immune cell infiltrations and immune phenotypes between the GMRG expression clusters but also different predicted responses to immunotherapy. After the screening, a total of 10 GMRGs were selected to build the GMRS. Survival analysis demonstrated the independent prognostic role of GMRS. Prognostic nomograms were established to predict 1-, 2-, and 3-year survival rates in the four cohorts.

Conclusion

Different subtypes of glutamine metabolism could affect the aggressiveness and TME immune features of diffuse glioma, despite their IDH mutational status. The expression signature of GMRGs could not only predict the outcome of patients with glioma but also be combined into an accurate prognostic nomogram.

Influence of Sports Training in Foothills on the Professional Athlete's Immunity

Neuroplasticity and inflammation play important part in the body's adaptive reactions in response to prolonged physical activity. These processes are associated with the cross-interaction of the nervous and immune systems, which is realized through the transmission of signals from neurotransmitters and cytokines. Using the methods of flow cytometry and advanced biochemical analysis of blood humoral parameters, we showed that intense and prolonged physical activity at the anaerobic threshold, without nutritional and metabolic support, contributes to the development of exercise-induced immunosuppression in sportsmen. These athletes illustrate the following signs of a decreased immune status: fewer absolute indicators of the content of leukocytes, lowered values in the immunoregulatory index (CD4⁺/CD8⁺), and diminished indicators of humoral immunity (immunoglobulins A, M, and G, and IFN-γ). These factors characterize the functional state of cellular and humoral immunity and their reduction affects the prenosological risk criteria, indicative of the athletes' susceptibility to develop exercise-induced immunosuppression.

CARD9 deficiency promotes pancreatic cancer growth by blocking dendritic cell maturation via SLC6A8-mediated creatine transport

Pancreatic cancer (PC) is featured with low survival rate and poor outcomes. Herein, we found that the expression of caspase-recruitment domain-containing protein 9 (CARD9), predominantly expressed in innate immune cells, was positively related to the prognosis of PC patients. CARD9-deficient PC mice exhibited rapider cancer progression and poorer survival rate. CARD9 knockout decreased dendritic cell (DC) maturation and impaired DC ability to activate T cells in vivo and in vitro. Adoptive DC transfer confirmed that the role of CARD9 deficiency in PC relied on DCs. Creatine was identified as the most significant differential metabolite between WT DCs and CARD9^-/- DCs wherein it played an essential role in maintaining DC maturation and function. CARD9 deficiency led to decreased creatine levels in DCs by inhibiting the transcription of the creatine-specific transporter, solute carrier family 6 member 8 (SLC6A8). Furtherly, CARD9 deletion blocked p65 activation by abolishing the formation of CARD9-BCL10-MALT1 complex, which prevented the binding between p65 and SLC6A8 promoter. These events decreased the creatine transport into DCs, and led to DC immaturity and impairment in antitumor immunity, consequently promoting PC progression.

A novel risk model based on immune response predicts clinical outcomes and characterizes immunophenotypes in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is highly heterogeneous in prognosis. The current TNM staging system shows its limitation in accurate risk evaluation. Immune response and immune cell abundances in the tumor immune microenvironment (TIME) are critical for cancer progression, clinical outcome and therapeutic response in TNBC. However, there is a lack of an effective risk model based on the overall transcriptional alterations relevant to different immune responses. In this study, multiple bioinformatics and statistical approaches were used to develop an immune-related risk (IRR) signature based on the differentially expressed genes between the immune-active and immune-inactive samples. The IRR model showed great performance in risk stratification, immune landscape evaluation and immunotherapy response prediction. Compared with the low-IRR group, the high-IRR group exhibited a poorer prognosis, less cytotoxic cell infiltration, higher M2/M1 ratio and upregulated glycolytic activity. Moreover, the high-IRR group showed more resistance to immunotherapy than the low-IRR group. Our study reveals that the IRR model may be a promising tool to help clinicians assess risk and optimize treatment for TNBC patients.

Connections between metabolism and epigenetics: mechanisms and novel anti-cancer strategy

Cancer cells undergo metabolic adaptations to sustain their growth and proliferation under several stress conditions thereby displaying metabolic plasticity. Epigenetic modification is known to occur at the DNA, histone, and RNA level, which can alter chromatin state. For almost a century, our focus in cancer biology is dominated by oncogenic mutations. Until recently, the connection between metabolism and epigenetics in a reciprocal manner was spotlighted. Explicitly, several metabolites serve as substrates and co-factors of epigenetic enzymes to carry out post-translational modifications of DNA and histone. Genetic mutations in metabolic enzymes facilitate the production of oncometabolites that ultimately impact epigenetics. Numerous evidences also indicate epigenome is sensitive to cancer metabolism. Conversely, epigenetic dysfunction is certified to alter metabolic enzymes leading to tumorigenesis. Further, the bidirectional relationship between epigenetics and metabolism can impact directly and indirectly on immune microenvironment, which might create a new avenue for drug discovery. Here we summarize the effects of metabolism reprogramming on epigenetic modification, and vice versa; and the latest advances in targeting metabolism-epigenetic crosstalk. We also discuss the principles linking cancer metabolism, epigenetics and immunity, and seek optimal immunotherapy-based combinations.

Metabolic pathway-based molecular subtyping of colon cancer reveals clinical immunotherapy potential and prognosis

PURPOSE

Colon cancer presents challenges to clinical diagnosis and management due to its high heterogeneity. For more efficient and convenient diagnosis and treatment of colon cancer, we are committed to characterizing the molecular features of colon cancer by pioneering a classification system based on metabolic pathways.

METHODS

Based on the 113 metabolic pathways and genes collected in the previous stage, we scored and filtered the metabolic pathways of each sample in the training set by ssGSEA, and obtained 16 metabolic pathways related to colon cancer recurrence. In consistent clustering of training set samples with recurrence-related metabolic pathway scores, we identified two robust molecular subtypes of colon cancer (MC1 and MC2). Furthermore, we performed multi-angle analysis on the survival differences of subtypes, metabolic characteristics, clinical characteristics, functional enrichment, immune infiltration, differences with other subtypes, stemness indices, TIDE prediction, and drug sensitivity, and finally constructed colon cancer prognostic model.

RESULTS

The results showed that the MC1 subtype had a poor prognosis based on higher immune activity and immune checkpoint gene expression. The MC2 subtype is associated with high metabolic activity and low expression of immune checkpoint genes and a better prognosis. The MC2 subtype was more responsive to PD-L1 immunotherapy than the MC1 subclass. However, we did not observe significant differences in tumor mutational burden between the two.

CONCLUSION

Two molecular subtypes of colon cancer based on metabolic pathways have distinct immune signatures. Constructing prognostic models based on subtype differential genes provides valuable reference for personalized therapy targeting unique tumor metabolic signatures.