Endogenous glutamine is rate-limiting for anti-CD3 and anti-CD28 induced CD4+ T-cell proliferation and glycolytic activity under hypoxia and normoxia

Solid tumor immunotherapy using NKG2D-based adaptor CAR T cells

NKG2D ligands (NKG2DLs) are broadly expressed in cancer. To target these, we describe an adaptor chimeric antigen receptor (CAR) termed NKG2D/Dap10-12. Herein, T cells are engineered to co-express NKG2D with a fusion protein that comprises Dap10 joined to a Dap12 endodomain. NKG2D/Dap10-12 T cells elicit compelling efficacy, eradicating or controlling NKG2DL-expressing tumors in several established xenograft models. Importantly, durable responses, long-term survival, and rejection of tumor re-challenge are reproducibly achieved. Efficacy is markedly superior to a clinical stage CAR analog, comprising an NKG2D-CD3ζ fusion. Structure-function analysis using an extended CAR panel demonstrates that potency is dependent on membrane proximity of signaling units, high NKG2D cell surface expression, adaptor structure, provision of exogenous Dap10, and inclusion of one rather than three immune tyrosine activation motifs per signaling unit. Potent therapeutic impact of NKG2D/Dap10-12 T cells is also underpinned by enhanced oxidative phosphorylation, reduced senescence, and transcriptomic re-programming for increased ribosomal biogenesis.

Hypoxia-adenosinergic regulation of B cell responses

Hypoxic microenvironments induce widespread metabolic changes that have been shown to be critical in regulating innate and adaptive immune responses. Hypoxia-induced changes include the generation of extracellular adenosine followed by subsequent signaling through adenosine receptors on immune cells. This evolutionarily conserved "hypoxia-adenosinergic" pathway of hypoxia → extracellular adenosine → adenosine receptor signaling has been shown to be critical in limiting and redirecting T cell responses including in tumor microenvironments and the gut mucosa. However, the question of whether hypoxic microenvironments are involved in the development of B cell responses has remained unexplored until recently. The discovery that germinal centers (GC), the anatomic site in which B cells undergo secondary diversification and affinity maturation, develop a hypoxic microenvironment has sparked new interest in how this evolutionarily conserved pathway affects antibody responses. In this review we will summarize what is known about hypoxia-adenosinergic microenvironments in lymphocyte development and ongoing immune responses. Specific focus will be placed on new developments regarding the role of the hypoxia-adenosinergic pathway in regulating GC development and humoral immunity.

Aerobic glycolysis but not GLS1-dependent glutamine metabolism is critical for anti-tumor immunity and response to checkpoint inhibition

Tumor cells undergo uncontrolled proliferation driven by enhanced anabolic metabolism including glycolysis and glutaminolysis. Targeting these pathways to inhibit cancer growth is a strategy for cancer treatment. Critically, however, tumor-responsive T cells share metabolic features with cancer cells, making them susceptible to these treatments as well. Here, we assess the impact on anti-tumor T cell immunity and T cell exhaustion by genetic ablation of lactate dehydrogenase A (LDHA) and glutaminase1 (GLS1), key enzymes in aerobic glycolysis and glutaminolysis. Loss of LDHA severely impairs expansion of T cells in response to tumors and chronic infection. In contrast, T cells lacking GLS1 can compensate for impaired glutaminolysis by engaging alternative pathways, including upregulation of asparagine synthetase, and thus efficiently respond to tumor challenge and chronic infection as well as immune checkpoint blockade. Targeting GLS1-dependent glutaminolysis, but not aerobic glycolysis, may therefore be a successful strategy in cancer treatment, particularly in combination with immunotherapy.

SLC38A2 promotes cell proliferation and invasion by promoting glutamine metabolism in adenomyosis

Adenomyosis is a benign uterine disorder that is associated with female infertility, a reduced clinical pregnancy rate and a high risk of miscarriage. Solute carrier family 38 member a2 (SLC38A2) is a glutamine (Gln) transporter that serves roles in various medical conditions. The present study aimed to reveal the role of SLC38A2 in adenomyosis. The mRNA expression levels of SLC38A2 in eutopic endometrial (EU) and ectopic endometrial (EC) tissues from adenomyotic patients were examined by reverse transcription-quantitative PCR. EU and EC cell proliferation and invasion were analyzed by Cell Counting Kit-8 and Transwell assays. Changes in the oxygen consumption rate (OCR) were determined to indicate the mitochondrial respiratory function and observed using a Seahorse analyzer. SLC38A2 expression in EC tissues was upregulated compared with that in normal endometrial tissues. SLC38A2 knockdown repressed EC cell proliferation and invasion. In addition, the Gln content and OCR were decreased in EC cells transfected with SLC38A2-knockdown lentivirus, whereas SLC38A2 overexpression had the opposite effect in EU cells. Furthermore, the increased proliferation and invasion rates and Gln level induced by SLC38A2 overexpression in EU cells were alleviated by CB-839, a glutaminase inhibitor. SLC38A2 overexpression promoted Gln metabolism and oxygen consumption rate, resulting in an increase in cell proliferation and invasion in the adenomyosis context. The present study indicated that reduction of SLC38A2 expression could be a novel target for adenomyosis therapy, and SLC38A2 may be a valuable clinical diagnostic molecule for adenomyosis.

Glutaminolysis and CD4+ T-cell metabolism in autoimmunity: From pathogenesis to therapy prospects

The recent increase in the pathogenesis of autoimmune diseases revealed the critical role of T cells. Investigation into immunometabolism has drawn attention to metabolic processes other than glycometabolism. In rapidly dividing immune cells, including T lymphocytes, the consumption of glutamine is similar to or higher than that of glucose even though glucose is abundant. In addition to contributing to many processes critical for cellular integrity and function, glutamine, as the most abundant amino acid, was recently regarded as an immunomodulatory nutrient. A better understanding of the biological regulation of glutaminolysis in T cells will provide a new perspective for the treatment of autoimmune diseases. In this review, we summarized the current knowledge of glutamine catabolism in CD4⁺ T-cell subsets of autoimmunity. We also focused on potential treatments targeting glutaminolysis in patients with autoimmune diseases. Knowledge of immunometabolism is constantly evolving, and glutamine metabolism may be a potential therapeutic target for autoimmune disease therapy.