MicroRNA-124 Enhances T Cells Functions by Manipulating the Lactic Acid Metabolism of Tumor Cells

  High production of lactic acid is a common feature of various tumors. Lactic acid is an immunosuppressive molecule with crucial roles in tumor cells' immune escape, which could largely be attributed to its negative effects on the T cells present in the tumor microenvironment (TME). Strategies that decrease the glycolysis rate of tumor cells could enhance immunosurveillance and limit tumor growth. Pyruvate kinase M2 (PKM2) is a key enzyme in the glycolysis pathway, and it plays a vital role in lactic acid buildup in the TME. MicroRNA (miR)-124 has been shown to be able to decrease tumor cell lactic acid synthesis indirectly by reducing PKM2 levels. In this study, we first overexpressed miR-124 in the tumor cells and evaluated its effects on the PKM2 expression and lactic acid production of the tumor cells using quantitative real-time polymerase chain reaction (qRT-PCR) and spectrophotometry, respectively. Then, we cocultured miR-124–treated tumor cells with T cells to investigate the effects of miR-124 overexpression on T cell proliferation, cytokine production, and apoptosis. Our results demonstrated that miR-124 overexpression could significantly reduce the amount of lactic acid produced by tumor cells by manipulating their glucose metabolism, which led to the augmented proliferation and IFN-γ production of T cells. Moreover, it rescued T cells from lactic acid-induced apoptosis. Our data suggest that lactic acid is a hindering factor for T-cell–based immunotherapies; however, manipulating tumor cells' metabolism via miR-124 could be a promising way to improve antitumor responses of T cells.

Targeted knockdown of Tim3 by short hairpin RNAs improves the function of anti-mesothelin CAR T cells

T-cell immunoglobulin mucin 3 (Tim3) is an immune checkpoint receptor that plays a central role in chimeric antigen receptor (CAR) T cell exhaustion within the tumor microenvironment. This study was aimed to evaluate the effects of targeted-knockdown of Tim3 on the antitumor function of anti-mesothelin (MSLN)-CAR T cells. To knockdown Tim3 expression, three different shRNA sequences specific to different segments of the human Tim3 gene were designed and co-inserted with an anti-MSLN-CAR transgene into lentiviral vectors. To investigate the efficacy of Tim3 targeting in T cells, expression of Tim3 was assessed before and after antigen stimulation. Afterwards, cytotoxic effects, proliferative response and cytokine production of MSLN-CAR T cells and Tim3-targeted MSLN-CAR T cells were analyzed. Our results showed that activation of T cells and MSLN-CAR T cells led to up-regulation of Tim3. Tim3 knockdown significantly decreased its expression in different groups of MSLN-CAR T cells. Tim3 knockdown significantly improved cytotoxic function, cytokine production and proliferation capacity of MSLN-CAR T cells. Our findings indicate that targeted knockdown of Tim3 allows tumor-infiltrating CAR T cells that would otherwise be inactivated to continue to expand and carry out effector functions, thereby altering the tumor microenvironment from immunosuppressive to immunosupportive via mitigated Tim3 signaling.

Mitochondria as Playmakers of CAR T-cell Fate and Longevity

The development of chimeric antigen receptor (CAR) T-cell therapy has led to a paradigm shift in cancer treatment. However, patients often do not benefit from CAR T-cell therapy due to poor persistence of the adoptively transferred cells. Development of strategies based on the generation and maintenance of long-lasting memory T cells may expand the therapeutic effects of CAR T cells. Mitochondrial metabolic pathways play crucial roles in regulating the fate, function, and longevity of T cells. Here, we discuss how reprogramming of mitochondrial metabolic pathways influences function, persistence, and determination of CAR T-cell fate toward a memory phenotype. Moreover, we explore how mitochondrial activity determines persistence and the clinical outcome of CAR T-cell therapy. In addition, we review some strategies for manipulating CAR T-cell mitochondria to improve the survival of CAR T cells.

A metabolic switch to memory CAR T cells: Implications for cancer treatment

Therapeutic efficacy of chimeric antigen receptor (CAR) T cells is associated with their expansion, persistence and effector function. Although CAR T cell therapy has shown remarkable therapeutic effects in hematological malignancies, its therapeutic efficacy has been limited in some types of cancers - in particular, solid tumors - partially due to the cells' inability to persist and the acquisition of T cell dysfunction within a harsh immunosuppressive tumor microenvironment. Therefore, it would be expected that generation of CAR T cells with intrinsic properties for functional longevity, such as the cells with early-memory phenotypes, could beneficially enhance antitumor immunity. Furthermore, because the metabolic pathways of CAR T cells help determine cellular differentiation and lifespan, therapies targeting such pathways like glycolysis and oxidative phosphorylation, can alter CAR T cell fate and durability within tumors. Here we discuss how reprogramming of CAR T cell metabolism and metabolic switch to memory CAR T cells influences their antitumor activity. We also offer potential strategies for targeting these metabolic circuits in the setting of adoptive CAR T cell therapy, aiming to better unleash the potential of adoptive CAR T cell therapy in the clinic.

Construction and Functional Characterization of a Fully Human Anti-mesothelin Chimeric Antigen Receptor (CAR) Expressing T Cell

Chimeric antigen receptor (CAR) T cell therapy is considered as an encouraging approach for the treatment of hematological malignancies. However, its efficacy in solid tumors has not been satisfying, mainly in the immunosuppressive network of the tumor microenvironment and paucity of appropriate target antigens. Mesothelin (MSLN) is a tumor-associated antigen (TAA) expressed in numerous types of solid tumors such as gastrointestinal, ovarian, and pancreatic tumors. Owing to high expression in tumor cells and low expression in normal tissues, MSLN-targeted therapies like monoclonal antibodies have been previously developed. In the present study, a CAR T cell harboring the second-generation of a fully human anti-MSLN-CAR construct containing CD3ζ and 4-1BB signaling domains was produced and it was functionally evaluated against an MSLN-expressing cell line. The findings showed potent, specific proliferation, cytotoxic activity, and interleukin (IL)-2, Tumor necrosis factor-(TNF) α, and Interferon-(IFN) γ production in an antigen-dependent manner. Cytotoxic activity was shown in effector-to-target ratio from 1:1 to 20:1, but the most adequate efficacy was observed in the ratio of 10:1. Non-specific activity against MSLN negative cell line was not observed. Our data demonstrated that primary human T cells expressing fully human MSLN-CAR construct are effective against MSLN-expressing cell lines in vitro, suggesting this MSLN-CAR construct as a potential therapeutic tool in a clinical setting.

Prolonged Persistence of Chimeric Antigen Receptor (CAR) T Cell in Adoptive Cancer Immunotherapy: Challenges and Ways Forward

CAR T cell qualities, such as persistence and functionality play important roles in determining the outcome of cancer immunotherapy. In spite of full functionality, it has been shown that poor persistence of CAR T cells can limit an effective antitumor immune response. Here, we outline specific strategies that can be employed to overcome intrinsic and extrinsic barriers to CAR T cell persistence. We also offer our viewpoint on how growing use of CAR T cells in various cancers may require modifications in the intrinsic and extrinsic survival signals of CAR T cells. We anticipate these amendments will additionally provide the rationales for generation of more persistent, and thereby, more effective CAR T cell treatments. CAR T cell qualities, such as persistence and functionality play important roles in determining the outcome of cancer immunotherapy. In spite of full functionality, it has been shown that poor persistence of CAR T cells can limit an effective antitumor immune response. Here, we outline specific strategies that can be employed to overcome intrinsic and extrinsic barriers to CAR T cell persistence. We also offer our viewpoint on how growing use of CAR T cells in various cancers may require modifications in the intrinsic and extrinsic survival signals of CAR T cells. We anticipate these amendments will additionally provide the rationales for generation of more persistent, and thereby, more effective CAR T cell treatments.

Genetic and pharmacological targeting of A2a receptor improves function of anti-mesothelin CAR T cells

Background

CAR T cell-based therapies have shown promising results in hematological malignancies. Results of CAR T cell projects in solid tumors have been less impressive, and factors including lack of targetable antigens and immunosuppressive tumor microenvironment (TME) have been suggested as culprits. Adenosine, a metabolite which is highly produced in TME, is known to mediate the suppression of anti-tumor T cell responses via binding and signaling through adenosine 2a receptor (A2aR).

Methods

In this study, the expression of A2aR and the effects of its activation on the function of fully human anti-mesothelin CAR T cells (MSLN-CAR T), were analyzed. Afterwards, the molecular and pharmacological means to overcome the inhibitory effects of A2aR signaling on CAR T cell function were used. This was performed by targeting A2aR expression in MSLN-CAR T cells using various anti-A2aR shRNA sequences embedded in the CAR vector and an A2aR pharmacological antagonist, SCH-58261. Statistical analyses were performed Prism 7 software.

Results

Our experiments showed significant A2aR upregulation on T cells during the CAR T cell production procedure (cell activation and transduction). Activation of adenosine signaling using adenosine analog led to the suppression of all major anti-tumor functions in MSLN-CAR T cells. Interestingly, CAR T cells that carried the anti-A2aR shRNA sequences were resistant to the inhibitory effects of adenosine signaling. Pharmacological inhibition of A2aR reversed the reduction in CAR T cell proliferation and cytokine response caused by the adenosine analog; however, it failed to rescue the cytotoxic function of the cells.

Conclusion

Altogether, our results indicate that mitigating A2aR signaling by genetic targeting of the receptor might be a promising approach in improving CAR T cell function in an unreceptive microenvironment and could potentially improve the outcome of treatment in clinical settings.