Chimeric antigen receptor (CAR) T cells are emerging as an effective antitumoral therapy. However, their therapeutic effects on solid tumors are limited because of their short survival time and the immunosuppressive tumor microenvironment. Memory T cells respond more vigorously and persist longer than their naïve/effector counterparts. Therefore, promoting CAR T-cell development into memory T cells could further enhance their antitumoral effects. HI-TOPK-032 is a T-LAK cell–originated protein kinase (TOPK)-specific inhibitor that moderately represses some types of tumors. However, it is unknown whether HI-TOPK-032 works on hepatocellular carcinoma (HCC) and whether it impacts antitumoral immunity. Using both subcutaneous and orthotopic xenograft tumor models of two human HCC cell lines, Huh-7 and HepG2, we found that HI-TOPK-032 significantly improved proliferation/persistence of CD8+ CAR T cells, as evidenced by an increase in CAR T-cell counts or frequency of Ki-67+CD8+ cells and a decrease in PD-1+LAG-3+TIM-3+CD8+ CAR T cells in vivo. Although HI-TOPK-032 did not significantly suppress HCC growth, it enhanced the capacity of CAR T cells to inhibit tumor growth. Moreover, HI-TOPK-032 augmented central memory CD8+ T cell (TCM) frequency while increasing eomesodermin expression in CD8+ CAR T cells in tumor-bearing mice. Moreover, it augmented CD8+ CAR TCM cells in vitro and reduced their expression of immune checkpoint molecules. Finally, HI-TOPK-032 inhibited mTOR activation in CAR T cells in vitro and in tumors, whereas overactivation of mTOR reversed the effects of HI-TOPK-032 on CD8+ TCM cells and tumor growth. Thus, our studies have revealed mechanisms underlying the antitumoral effects of HI-TOPK-032 while advancing CAR T-cell immunotherapy.

The early secreted antigenic target of 6 kDa (ESAT-6), a main effector molecule of the ESX-1 secretion system, is identified as a virulence determinant and immunoregulatory protein of Mycobacterium tuberculosis (Mtb), affecting the interaction between host immune cells and pathogens. ESAT-6 facilitates the survival of mycobacteria and their cell-to-cell spreading through membrane-permeabilizing activity and the regulation of host immune cell functions. In this review, we first summarize the recent knowledge of the roles of ESAT-6 in the survival of bacteria, phagosomal escape, and pathogenicity during Mtb infection. Then, we focused on its complex immunomodulatory effects on different immune cells, such as macrophages, dendritic cells, neutrophils, and T cells, accentuating its capability to either facilitate or inhibit immune responses through different signaling pathways. While our review has summarized its main roles in immunopathology in the context of tuberculosis, we additionally search for emerging evidence indicating that ESAT-6 has anti-inflammatory and immunosuppressive properties. Particularly, we discuss recent preclinical studies showing its capability to suppress transplant rejection and alloimmunity, probably via the induction of regulatory T cells. Nevertheless, the potential clinical use of ESAT-6 remains uncertain and needs further verification by comprehensive preclinical and clinical studies. Thus, we propose that ESAT-6 may be exploited to ameliorate immunopathology in TB infection and to suppress immune-mediated inflammation or transplant rejection as well.

Background: Maintenance immunosuppression is required for suppression of alloimmunity or allograft rejection. However, continuous use of immunosuppressants may lead to various side effects, necessitating the use of alternative immunosuppressive drugs. The early secreted antigenic target of 6 kDa (ESAT-6) is a virulence factor and immunoregulatory protein of mycobacterium tuberculosis (Mtb), which alters host immunity through dually regulating development or activation of various immune cells. ESAT-6 may be a potential alternative immunosuppressant that could be utilized to suppress allograft rejection although it remains unknown whether ESAT-6 actually regulates alloimmunity.Methods: In this study, murine skin or heart allotransplantation was performed to determine the effects of ESAT-6 protein on allograft survival. Flow cytometric analyses were conducted to quantify CD4⁺Foxp3⁺ Tregs, while immunohistochemistry was carried out to observe allograft immunopathology. Western blotting was used to detect IĸBα/c-Rel signaling during Treg induction. Finally, CD4⁺CD25^- conventional T cells were cultured to induce Tregs and their proliferation.Results: Here we found that ESAT-6 significantly extended murine skin and heart allograft survival, alleviated CD3⁺ T cell infiltration and increased Foxp3⁺ Tregs in an allograft. ESAT-6 augmented the percentage of CD4⁺Foxp3⁺ Tregs, whereas it decreased the frequency of Th1 and CD4⁺/CD8⁺ effector T cells in spleen and lymph nodes (LNs) posttransplantation. ESAT-6 also induced CD4⁺Foxp3⁺ Tregs from CD4⁺CD25^- T cells in vitro by activating IĸBα/c-Rel signaling pathway, whereas inhibition of c-Rel signaling blocked Treg induction. Moreover, it suppressed conventional CD4⁺CD25^- T cell proliferation in vitro in the absence of antigen-presenting cells (APCs), with an increase in IL-10 and decrease in IFN-γ production. On the other hand, it did not significantly alter DC maturation after allotransplantation.Conclusion: Thus, ESAT-6 suppresses alloimmunity and inhibits allograft rejection by inducing CD4⁺Foxp3⁺ Tregs through IĸBα/c-Rel signaling pathway.

Lidocaine, an amide-type regional anesthetic, has been an important medication in the field of anesthesia since its clinical approval. Recently, lidocaine has emerged as a powerful immunomodulatory agent beyond its classical anesthetic properties. This review has summarized the recent basic and clinical studies with sufficient evidence on the multifaceted effects of lidocaine on both innate and adaptive immune cells, including macrophages, neutrophils, eosinophils, basophils, natural killer (NK) cells, mast cells, dendritic cells (DCs), monocytes, and T lymphocytes. We have also detailed how lidocaine affects critical cellular processes, such as cellular polarization, cytokine production, phagocytosis, and apoptosis, through multiple signaling pathways, including NF-κB, TLR4/p38 MAPK, voltage-sensitive sodium channels, HIF1α, TGF-β/Smad3, AMPK-SOCS3, TBK1-IRF7, and G protein-coupled receptors. These immunoregulatory effects of lidocaine are dependent on its concentration, duration of action, and the microenvironment. The immunomodulatory actions of lidocaine may contribute to its potential therapeutic value in various settings of diseases, such as cancer, sepsis, acute lung injury, asthma, organ transplantation, ischemia–reperfusion injury (IRI), and diabetes. We propose that lidocaine can be repurposed as an immunomodulator for treating immune-mediated inflammatory diseases. However, future research should define optimal dosing strategies, validate its mechanisms of action in clinical trials, and explore its novel clinical applications as a complementary immunotherapy.

Chimeric antigen receptor (CAR) T cells are emerging as an effective antitumoral therapy. However, their therapeutic effects on solid tumors are limited because of their short survival time and the immunosuppressive tumor microenvironment. Memory T cells respond more vigorously and persist longer than their naïve/effector counterparts. Therefore, promoting CAR T-cell development into memory T cells could further enhance their antitumoral effects. HI-TOPK-032 is a T-LAK cell–originated protein kinase (TOPK)-specific inhibitor that moderately represses some types of tumors. However, it is unknown whether HI-TOPK-032 works on hepatocellular carcinoma (HCC) and whether it impacts antitumoral immunity. Using both subcutaneous and orthotopic xenograft tumor models of two human HCC cell lines, Huh-7 and HepG2, we found that HI-TOPK-032 significantly improved proliferation/persistence of CD8+ CAR T cells, as evidenced by an increase in CAR T-cell counts or frequency of Ki-67+CD8+ cells and a decrease in PD-1+LAG-3+TIM-3+CD8+ CAR T cells in vivo. Although HI-TOPK-032 did not significantly suppress HCC growth, it enhanced the capacity of CAR T cells to inhibit tumor growth. Moreover, HI-TOPK-032 augmented central memory CD8+ T cell (TCM) frequency while increasing eomesodermin expression in CD8+ CAR T cells in tumor-bearing mice. Moreover, it augmented CD8+ CAR TCM cells in vitro and reduced their expression of immune checkpoint molecules. Finally, HI-TOPK-032 inhibited mTOR activation in CAR T cells in vitro and in tumors, whereas overactivation of mTOR reversed the effects of HI-TOPK-032 on CD8+ TCM cells and tumor growth. Thus, our studies have revealed mechanisms underlying the antitumoral effects of HI-TOPK-032 while advancing CAR T-cell immunotherapy.

HI-TOPK-032 decreases the expression of LAG-3 and TIM-3 and frequencies of CCR7+PD-1+ subset in CD8+ CAR-T cells of mice bearing subcutaneous Huh7-HCC.