Mitochondrial metabolic flexibility is critical for CD8+ T cell antitumor immunity

Microenvironment actuated CAR T cells improve solid tumor efficacy without toxicity

A major limiting factor in the success of chimeric antigen receptor (CAR) T cell therapy for the treatment of solid tumors is targeting tumor antigens also found on normal tissues. CAR T cells against GD2 induced rapid, fatal neurotoxicity because of CAR recognition of GD2+ normal mouse brain tissue. To improve the selectivity of the CAR T cell, we engineered a synthetic Notch receptor that selectively expresses the CAR upon binding to P-selectin, a cell adhesion protein overexpressed in tumor neovasculature. These tumor microenvironment actuated T (MEAT) cells ameliorated T cell infiltration in the brain, preventing fatal neurotoxicity while maintaining antitumor efficacy. We found that conditional CAR expression improved the persistence of tumor-infiltrating lymphocytes because of enhanced metabolic fitness of MEAT cells and the infusion of a less differentiated product. This approach increases the repertoire of targetable solid tumor antigens by restricting CAR expression and subsequent killing to cancer cells only and provides a proof-of-concept model for other targets.

PTPMT1 inhibition induces apoptosis and growth arrest of human SCLC cells by disrupting mitochondrial metabolism

Background

Many cancer cells exhibit aberrant metabolic reprogramming through abnormal mitochondrial respiration. Protein tyrosine phosphatase mitochondrial 1 (PTPMT1) is a protein tyrosine phosphatase localized to the mitochondria and linked to mitochondrial respiration. However, the expression and role of PTPMT1 in regulating the biological characteristics of small cell lung cancer (SCLC) has not yet been explored. The aim of this study was to evaluate the role of PTPMT1 on SCLC cell survival and mitochondrial function.

Methods

SCLC and adjacent normal tissues were obtained from surgery. The expression level of PTPMT1 in the SCLC tissues and cell lines was determined by immunohistochemical staining, western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). PTPMT1 knockdown was induced by lentivirus-mediated short-hairpin RNA (shRNA) transduction and PTPMT1 inhibition (alexidine dihydrochloride). The biological characteristics of the cells were measured by cell counting kit 8 (CCK-8), colony formation assay, and cell migration assay. The mitochondrial function of the cells was measured by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining. The H69 cells were treated with alexidine dihydrochloride, after which transcriptome sequencing and an untargeted metabolomic analysis were performed. The transcriptome differentially expressed genes were measured by qRT-PCR.

Results

PTPMT1 was upregulated in the SCLC tissues compared to the adjacent normal tissues. PTPMT1 inhibition by lentiviral shRNA transduction or specific inhibition resulted in significant growth arrest and apoptosis. The transcriptome sequencing analysis revealed that pathways related to the respiration chain and mitochondrial member protein were disrupted. Several mitochondrial metabolism-related genes, such as FGF21, GDF-15, APLN, and MT-DN6, were dysregulated. Further, PTPMT1 inhibition was found to downregulate Glut expression and disturb mitochondrial function.

Conclusions

PTPMT1 was shown to play a critical role in the survival and growth of SCLC cells, and may become a potential therapeutic target.

Upregulation of CD244 promotes CD8+ T cell exhaustion in patients with alveolar echinococcosis and a murine model

BACKGROUND

In patients with alveolar echinococcosis (AE), CD8+ T cells undergo functional exhaustion, which accelerates the malignant progression of AE. However, the role of inhibitory receptor CD244 in mediating CD8+ T cell exhaustion remains elusive.

METHODS

CD244 expression on exhausted CD8+ T cells in the close liver tissue (CLT) of AE patients was analyzed using single-cell RNA sequencing data. Immunohistochemistry and immunofluorescence were employed to detect CD244 expression. Flow cytometry was used to assess the impact of CD244 on differentiation and effector function of CD8+ T cells in patients with AE, in vitro and in vivo models. Reactive oxygen species (ROS) and oxygen consumption rate (OCR) were measured to evaluate the influence of CD244 on mitochondrial function of CD8+ T cells.

RESULTS

CD244+CD8+ T cells in the CLT of AE patients exhibit a more terminal differentiation phenotype, with reduced secretion of IFN-γ and TNF-α. In vitro studies revealed that CD8+ T cells from CD244-deficient mice produced higher levels of IFN-γ, TNF-α and Granzyme B. In vivo studies revealed that CD244 deficiency enhanced the secretion capacity of IFN-γ and TNF-α by CD8+ T cells, inhibiting the growth of metacestodes. Moreover, CD244 deficiency leads to a decrease in ROS levels in liver CD8+ T cells, while significantly increasing their adenosine triphosphate (ATP)-linked oxygen consumption rate.

CONCLUSIONS

CD244 facilitates AE disease progression by mediating immune exhaustion in CD8+ T cells.

Impact of mitochondrial dysfunction on the antitumor effects of immune cells

Mitochondrial dysfunction, a hallmark of immune cell failure, affects the antitumor effects of immune cells through metabolic reprogramming, fission, fusion, biogenesis, and immune checkpoint signal transduction of mitochondria. According to researchers, restoring damaged mitochondrial function can enhance the efficacy of immune cells. Nevertheless, the mechanism of mitochondrial dysfunction in immune cells in patients with cancer is unclear. In this review, we recapitulate the impact of mitochondrial dysfunction on the antitumor effects of T cells, natural killer cells, dendritic cells, and tumor-associated macrophage and propose that targeting mitochondria can provide new strategies for antitumor therapy.

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.

Targeting metabolism to improve CAR-T cells therapeutic efficacy

ABSTRACT

Chimeric antigen receptor T (CAR-T) cell therapy achieved advanced progress in the treatment of hematological tumors. However, the application of CAR-T cell therapy for solid tumors still faces many challenges. Competition with tumor cells for metabolic resources in an already nutrient-poor tumor microenvironment is a major contributing cause to CAR-T cell therapy's low effectiveness. Abnormal metabolic processes are now acknowledged to shape the tumor microenvironment, which is characterized by increased interstitial fluid pressure, low pH level, hypoxia, accumulation of immunosuppressive metabolites, and mitochondrial dysfunction. These factors are important contributors to restriction of T cell proliferation, cytokine release, and suppression of tumor cell-killing ability. This review provides an overview of how different metabolites regulate T cell activity, analyzes the current dilemmas, and proposes key strategies to reestablish the CAR-T cell therapy's effectiveness through targeting metabolism, with the aim of providing new strategies to surmount the obstacle in the way of solid tumor CAR-T cell treatment.