Tim-3 adaptor protein Bat3 is a molecular checkpoint of T cell terminal differentiation and exhaustion

Combination therapy with immune checkpoint inhibitors in colorectal cancer: Challenges, resistance mechanisms, and the role of microbiota

Colorectal cancer (CRC) is still one of the leading causes of cancer deaths worldwide. Even though there has been progress in cancer immunotherapy, the results of applying immune checkpoint inhibitors (ICIs) have been unsatisfactory, especially in microsatellite stable (MSS) CRC. Single-agent ICIs that target programmed cell death-1 (PD-1)/ PD-L1, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), T cell Ig- and mucin-domain-containing molecule-3 (TIM-3), and lymphocyte activation gene (LAG)-3 have emerged as having specific benefits. However, many primary and secondary resistance mechanisms are available in the tumor microenvironment (TME) that prevent it from happening. Combination strategies, such as the use of anti-PD-1 and anti-CTLA-4, can be effective in overcoming these resistance pathways, but toxicities remain a significant concern. Moreover, ICIs have been integrated with various treatment modalities, including chemotherapy, radiotherapy, antibiotics, virotherapy, polyadenosine diphosphate-ribose polymerase (PARP) inhibitors, and heat shock protein 90 (HSP90) inhibitors. The outcomes observed in both preclinical and clinical settings have been encouraging. Interestingly, manipulating gut microbiota via fecal microbiota transplantation (FMT) has been identified as a new strategy to increase the efficacy of immunotherapy in CRC patients. Therefore, integrating ICIs with other treatment approaches holds promise in enhancing the prognosis of CRC patients. This review focuses on the unmet need for new biomarkers to select patients for combination therapies and the ongoing work to overcome resistance and immune checkpoint blockade.

Reprogramming the breast tumor immune microenvironment: cold-to-hot transition for enhanced immunotherapy

This review discusses reprogramming the breast tumor immune microenvironment from an immunosuppressive cold state to an immunologically active hot state. A complex interplay is revealed, in which the accumulation of metabolic byproducts-such as lactate, reactive oxygen species (ROS), and ammonia-is shown to impair T-cell function and promote tumor immune escape. It is demonstrated that the tumor microenvironment (TME) is dominated by immunosuppressive cytokines, including interleukin-10 (IL-10), transforming growth factorβ (TGFβ), and IL-35. Notably, IL-35 is produced by regulatory T cells and breast cancer cells. The conversion of conventional T cells into IL-35-producing induced regulatory T cells, along with the inhibition of pro-inflammatory cytokine secretion, contributes to the suppression of anti-tumor immunity. It is further demonstrated that key immune checkpoint molecules-such as PD-1, PDL1, CTLA-4, TIM-3, LAG-3, and TIGIT-are upregulated within the TME, leading to Tcell exhaustion and diminished immune responses. The blockade of these checkpoints is shown to restore T-cell functionality and is proposed as a strategy to convert cold tumors into hot ones with robust effector cell infiltration. The therapeutic potential of chimeric antigen receptor (CAR)T cell therapy is also explored, and targeting specific tumor-associated antigens, such as glycoproteins and receptor tyrosine kinases, is highlighted. It is suggested that CART cell efficacy can be enhanced by combining these cells with immune checkpoint inhibitors and other immunomodulatory agents, thereby overcoming the barriers imposed by the immunosuppressive TME. Moreover, the role of the microbiome in regulating estrogen metabolism and systemic inflammation is reviewed. Alterations in the gut microbiota are shown to affect the TME, and microbiome-based interventions are proposed as an additional means to facilitate the cold-to-hot transition. It is concluded that by targeting the metabolic and immunological pathways that underpin immune suppression-through combination strategies involving checkpoint blockade, CART cell therapies, and microbiome modulation-the conversion of the breast TME from cold to hot can be achieved. This reprogramming is anticipated to enhance immune cell infiltration and function, thereby improving the overall efficacy of immunotherapies and leading to better clinical outcomes for breast cancer patients.

Targeting Immune Checkpoint Inhibitors for Non-Small-Cell Lung Cancer: Beyond PD-1/PD-L1 Monoclonal Antibodies

Non-small-cell lung cancer (NSCLC) remains a leading cause of cancer-related mortality worldwide. Immunotherapy targeting the PD-1/PD-L1 axis has revolutionized treatment, providing durable responses in a subset of patients. However, with fewer than 50% of patients achieving significant benefits, there is a critical need to expand therapeutic strategies. This review explores emerging targets in immune checkpoint inhibition beyond PD-1/PD-L1, including CTLA-4, TIGIT, LAG-3, TIM-3, NKG2A, and CD39/CD73. We highlight the biological basis of CD8 T cell exhaustion in shaping the antitumor immune response. Novel therapeutic approaches targeting additional inhibitory receptors (IR) are discussed, with a focus on their distinct mechanisms of action and combinatory potential with existing therapies. Despite significant advancements, challenges remain in overcoming resistance mechanisms and optimizing patient selection. This review underscores the importance of dual checkpoint blockade and innovative bispecific antibody engineering to maximize therapeutic outcomes for NSCLC patients.

The Role of TIM-3 in Glioblastoma Progression

Several immunoregulatory or immune checkpoint receptors including T cell immunoglobulin and mucin domain 3 (TIM-3) have been implicated in glioblastoma progression. Rigorous investigation over the last decade has elucidated TIM-3 as a key player in inhibiting immune cell activation and several key associated molecules have been identified both upstream and downstream that mediate immune cell dysfunction mechanistically. However, despite several reviews being published on other immune checkpoint molecules such as PD-1 and CTLA-4 in the glioblastoma setting, no such extensive review exists that specifically focuses on the role of TIM-3 in glioblastoma progression and immunosuppression. Here, we critically summarize the current literature regarding TIM-3 expression as a prognostic marker for glioblastoma, its expression profile on immune cells in glioblastoma patients and the exploration of anti-TIM-3 agents in glioblastoma pre-clinical models for potential clinical application.

Involvement of Tim-3 in Maternal-fetal Tolerance: A Review of Current Understanding

As the first T cell immunoglobulin mucin (Tim) family member to be identified, Tim-3 is a powerful immune checkpoint that functions in immunoregulation and induction of tolerance. Conventionally, Tim-3 is considered to play a role in adaptive immunity, especially in helper T cell-mediated immune responses. As researches progress, Tim-3 has been detected in a wider range of cell types, modulating cell function through ligand-receptor interactions and other pathways. Strikingly, Tim-3 plays a pivotal role in maternal-fetal tolerance by regulating immune cell functions and orchestrating the maternal-fetal cross-talk. In this review, we elaborate on the involvement of Tim-3 in immunology, with a focus on its participation in maternal-fetal tolerance to provide new insights into immunoregulation during pregnancy. Our work will be helpful in further understanding the pathogenesis of pregnancy-related diseases and will inspire new strategies for their diagnosis and treatment.

Myeloid-Derived Suppressor Cells Induce Exhaustion-Like CD8+ T Cells during JEV Infection

Japanese encephalitis (JE), caused by Japanese encephalitis virus (JEV), is a mosquito-borne zoonotic disease and a leading cause of viral encephalitis worldwide. While JEV has the ability to traverse the blood-brain barrier (BBB), the precise mechanisms by which it inhibits the immune response prior to penetrating the BBB remain unclear, presenting obstacles in the development of efficacious therapeutic interventions. This study investigated the impact of JEV on CD8+ T cell responses, with a particular focus on the dysfunction of CD8+ T cells during JEV infection. Our results demonstrated that JEV infection significantly elevated the expression of PD-1 and TIM-3 on CD8+ T cells, which are markers of T cell exhaustion, leading to inhibited function and impaired differentiation, resulting in a poorer prognosis in mice. Compared with nondiseased mice, symptomatic mice presented a greater proportion of exhaustion-like CD8+ T cells. In vitro experiments further demonstrated that MDSCs induced an exhaustion-like state in CD8+ T cells, characterized by significant upregulation of PD-1 and TIM-3 expression. Notably, blocking TIM-3 or depleting MDSCs restored CD8+ T cell functionality by rescuing the expression of IFN-γ and TNF-α. Furthermore, the depletion of MDSCs not only alleviated T cell exhaustion-like phenotypes but also improved survival rates in JEV-infected mice. These findings suggest that JEV promotes immune evasion through MDSC-induced CD8+ T cell exhaustion-like states and identify TIM-3 as a promising therapeutic target for JE treatment.

Reduced T and NK Cell Activity in Glioblastoma Patients Correlates with TIM-3 and BAT3 Dysregulation

Inhibitory receptors are critical for regulating immune cell function. In cancer, these receptors are often over-expressed on the cell surface of T and NK cells, leading to reduced anti-tumor activity. Here, through the analysis of 11 commonly studied checkpoint and inhibitory receptors, we discern that only HAVCR2 (TIM3) and ENTPD1 (CD39) display significantly greater gene expression in glioblastoma compared to normal brain and lower grade glioma. Cell surface TIM-3, but not ENTPD1, was also elevated on activated CD4+ and CD8+ T cells, as well as on NK cells from glioblastoma patients compared to healthy donor T and NK cells. A subsequent analysis of molecules known to co-ordinate TIM-3 function and regulation was performed, which revealed that BAT3 expression was significantly reduced in CD4+ and CD8+ T cells, as well as NK cells from glioblastoma patients compared to counterparts from healthy donors. These pro-inhibitory changes are also correlated with reduced levels of the activation marker CD69 and the pro-inflammatory cytokine IFNγ in CD4+ and CD8+ T cells, as well as NK cells from glioblastoma patients. Collectively, these data reveal that glioblastoma-mediated CD4+ and CD8+ T cell and NK cell suppression is due, at least in part, to dysregulated TIM-3 and BAT3 expression and the associated downstream immunoregulatory and dysfunctional effects.

IL-27/Blimp-1 axis regulates the differentiation and function of Tim-3+ Tregs during early pregnancy

Decidual regulatory T cells (Tregs) are essential for successful pregnancy outcome. A subset of Tregs, T cell immunoglobulin and mucin domain-containing protein 3-positive regulatory T cells (TregsTim-3+), plays a central role in the acceptance of the fetus during early stages of normal pregnancy. The molecular mechanism regulating the differentiation and function of TregsTim-3+ is unknown. Here, we investigated the role of the transcription factor B lymphocyte-induced maturation protein 1 (Blimp-1) on decidual TregTim-3+ differentiation. We demonstrated that Blimp-1 enhanced the coexpression of negative costimulatory molecules (Tim-3, T cell immunoreceptor with Ig and ITIM domains, and programmed cell death protein 1) on Tregs and improved their immunosuppressive functions, including increased IL-10 secretion, suppression of effector T cell proliferation, and promotion of macrophage polarization toward the M2 phenotype. Furthermore, we showed that IL-27 regulated the expression of Tim-3 and Blimp-1 through the STAT1 signaling pathway and that transfer of TregsBlimp-1+ into an abortion-prone mouse model effectively reduced embryo absorption rate. We postulated that abnormalities in the IL-27/Blimp-1 axis might be associated with recurrent pregnancy loss (RPL). These findings provided insights for developing more efficient immunotherapies for women with RPL.

Endoplasmic reticulum stress-a key guardian in cancer

Endoplasmic reticulum stress (ERS) is a cellular stress response characterized by excessive contraction of the endoplasmic reticulum (ER). It is a pathological hallmark of many diseases, such as diabetes, obesity, and neurodegenerative diseases. In the unique growth characteristic and varied microenvironment of cancer, high levels of stress are necessary to maintain the rapid proliferation and metastasis of tumor cells. This process is closely related to ERS, which enhances the ability of tumor cells to adapt to unfavorable environments and promotes the malignant progression of cancer. In this paper, we review the roles and mechanisms of ERS in tumor cell proliferation, apoptosis, metastasis, angiogenesis, drug resistance, cellular metabolism, and immune response. We found that ERS can modulate tumor progression via the unfolded protein response (UPR) signaling of IRE1, PERK, and ATF6. Targeting the ERS may be a new strategy to attenuate the protective effects of ERS on cancer. This manuscript explores the potential of ERS-targeted therapies, detailing the mechanisms through which ERS influences cancer progression and highlighting experimental and clinical evidence supporting these strategies. Through this review, we aim to deepen our understanding of the role of ER stress in cancer development and provide new insights for cancer therapy.

Development of pharmacological immunoregulatory anti-cancer therapeutics: current mechanistic studies and clinical opportunities

Immunotherapy represented by anti-PD-(L)1 and anti-CTLA-4 inhibitors has revolutionized cancer treatment, but challenges related to resistance and toxicity still remain. Due to the advancement of immuno-oncology, an increasing number of novel immunoregulatory targets and mechanisms are being revealed, with relevant therapies promising to improve clinical immunotherapy in the foreseeable future. Therefore, comprehending the larger picture is important. In this review, we analyze and summarize the current landscape of preclinical and translational mechanistic research, drug development, and clinical trials that brought about next-generation pharmacological immunoregulatory anti-cancer agents and drug candidates beyond classical immune checkpoint inhibitors. Along with further clarification of cancer immunobiology and advances in antibody engineering, agents targeting additional inhibitory immune checkpoints, including LAG-3, TIM-3, TIGIT, CD47, and B7 family members are becoming an important part of cancer immunotherapy research and discovery, as are structurally and functionally optimized novel anti-PD-(L)1 and anti-CTLA-4 agents and agonists of co-stimulatory molecules of T cells. Exemplified by bispecific T cell engagers, newly emerging bi-specific and multi-specific antibodies targeting immunoregulatory molecules can provide considerable clinical benefits. Next-generation agents also include immune epigenetic drugs and cytokine-based therapeutics. Cell therapies, cancer vaccines, and oncolytic viruses are not covered in this review. This comprehensive review might aid in further development and the fastest possible clinical adoption of effective immuno-oncology modalities for the benefit of patients.

Unleashing the power of immune checkpoints: Post-translational modification of novel molecules and clinical applications

Immune checkpoint molecules play a pivotal role in the initiation, regulation, and termination of immune responses. Tumor cells exploit these checkpoints to dampen immune cell function, facilitating immune evasion. Clinical interventions target this mechanism by obstructing the binding of immune checkpoints to their ligands, thereby restoring the anti-tumor capabilities of immune cells. Notably, therapies centered on immune checkpoint inhibitors, particularly PD-1/PD-L1 and CTLA-4 blocking antibodies, have demonstrated significant clinical promise. However, a considerable portion of patients still encounter suboptimal efficacy and develop resistance. Recent years have witnessed an exponential surge in preclinical and clinical trials investigating novel immune checkpoint molecules such as TIM3, LAG3, TIGIT, NKG2D, and CD47, along with their respective ligands. The processes governing immune checkpoint molecules, from their synthesis to transmembrane deployment, interaction with ligands, and eventual degradation, are intricately tied to post-translational modifications. These modifications encompass glycosylation, phosphorylation, ubiquitination, neddylation, SUMOylation, palmitoylation, and ectodomain shedding. This discussion proceeds to provide a concise overview of the structural characteristics of several novel immune checkpoints and their ligands. Additionally, it outlines the regulatory mechanisms governed by post-translational modifications, offering insights into their potential clinical applications in immune checkpoint blockade.

The role of TIM-3 in sepsis: a promising target for immunotherapy?

Sepsis remains a significant cause of mortality and morbidity worldwide, with limited effective treatment options. The T-cell immunoglobulin and mucin domain-containing molecule 3 (TIM-3) has emerged as a potential therapeutic target in various immune-related disorders. This narrative review aims to explore the role of TIM-3 in sepsis and evaluate its potential as a promising target for immunotherapy. We discuss the dynamic expression patterns of TIM-3 during sepsis and its involvement in regulating immune responses. Furthermore, we examine the preclinical studies investigating the regulation of TIM-3 signaling pathways in septic models, highlighting the potential therapeutic benefits and challenges associated with targeting TIM-3. Overall, this review emphasizes the importance of TIM-3 in sepsis pathogenesis and underscores the promising prospects of TIM-3-based immunotherapy as a potential strategy to combat this life-threatening condition.

Beyond T cell exhaustion: TIM-3 regulation of myeloid cells

T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) is an important immune checkpoint molecule initially identified as a marker of IFN-γ-producing CD4+ and CD8+ T cells. Since then, our understanding of its role in immune responses has significantly expanded. Here, we review emerging evidence demonstrating unexpected roles for TIM-3 as a key regulator of myeloid cell function, in addition to recent work establishing TIM-3 as a delineator of terminal T cell exhaustion, thereby positioning TIM-3 at the interface between fatigued immune responses and reinvigoration. We share our perspective on the antagonism between TIM-3 and T cell stemness, discussing both cell-intrinsic and cell-extrinsic mechanisms underlying this relationship. Looking forward, we discuss approaches to decipher the underlying mechanisms by which TIM-3 regulates stemness, which has remarkable potential for the treatment of cancer, autoimmunity, and autoinflammation.

Diffuse large B-cell lymphoma: the significance of CD8+ tumor-infiltrating lymphocytes exhaustion mediated by TIM3/Galectin-9 pathway

BACKGROUND

Overexpression of T-cell immunoglobulin and mucin domain-containing protein 3 (TIM3) is related to the exhaustion of CD8+ tumor-infiltrating lymphocytes (TILs) in diffuse large B-cell lymphoma (DLBCL). However, the mechanism of TIM3-mediated CD8+TILs exhaustion in DLBCL remains poorly understood. Therefore, we aimed to clarify the potential pathway involved in TIM3-mediated CD8+TILs exhaustion and its significance in DLBCL.

METHODS

The expression of TIM3 and its correlation with CD8+TILs exhaustion, the key ligand of TIM3, and the potential pathway of TIM3-mediated CD8+TILs exhaustion in DLBCL were analyzed using single-cell RNA sequencing and validated by RNA sequencing. The biological significance of TIM3-related pathway in DLBCL was investigated based on RNA sequencing, immunohistochemistry, and reverse transcription-quantitative polymerase chain reaction data. Finally, the possible regulatory mechanism of TIM3-related pathway in DLBCL was explored using single-cell RNA sequencing and RNA sequencing.

RESULTS

Our results demonstrated that CD8+TILs, especially the terminally exhausted state, were the major clusters that expressed TIM3 in DLBCL. Galectin-9, mainly expressed in M2 macrophages, is the key ligand of TIM3 and can induce the exhaustion of CD8+TILs through TIM3/Galectin-9 pathway. Meanwhile, high TIM3/Galectin-9 enrichment is related to immunosuppressive tumor microenvironment, severe clinical manifestations, inferior prognosis, and poor response to CHOP-based chemotherapy, and can predict the clinical efficacy of immune checkpoint blockade therapy in DLBCL. Furthermore, the TIM3/Galectin-9 enrichment in DLBCL may be regulated by the IFN-γ signaling pathway.

CONCLUSIONS

Our study highlights that TIM3/Galectin-9 pathway plays a crucial role in CD8+TILs exhaustion and the immune escape of DLBCL, which facilitates further functional studies and could provide a theoretical basis for the development of novel immunotherapy in DLBCL.

Cutting Edge: Serpine1 Negatively Regulates Th1 Cell Responses in Experimental Autoimmune Encephalomyelitis

Th1 cells are critical in experimental autoimmune encephalomyelitis (EAE). Serine protease inhibitor clade E1 (Serpine1) has been posited as an inhibitor of IFN-γ from T cells, although its role in autoimmunity remains unclear. In this study, we show that Serpine1 knockout (KO) mice develop EAE of enhanced severity relative to wild-type (WT) controls. Serpine1 overexpression represses Th1 cell cytokine production and pathogenicity, whereas Serpine1-KO:2D2 Th1 cells transfer EAE of increased severity in comparison with WT 2D2 Th1 cells. Notably, polarized Serpine1-KO Th1 cells display delayed expression of the Th1-specific inhibitory receptor, Tim-3 (T cell Ig and mucin-domain containing-3). Serpine1-KO:Tim-3-Tg Th1 cells, which transgenically overexpress Tim-3, showed increased expression of IFN-γ and reduced expression of the checkpoint molecules Lag-3 and PD-1 relative to WT Tim-3-Tg counterparts. Furthermore, Serpine1 deficiency restored the EAE phenotype of Tim-3-Tg mice that normally develop mild disease. Taken together, we identify Serpine1 as a negative regulator of Th1 cells.

Identification of a small-molecule Tim-3 inhibitor to potentiate T cell-mediated antitumor immunotherapy in preclinical mouse models

T cell immunoglobulin and mucin-containing molecule 3 (Tim-3), expressed in dysfunctional and exhausted T cells, has been widely acknowledged as a promising immune checkpoint target for tumor immunotherapy. Here, using a strategy combining virtual and functional screening, we identified a compound named ML-T7 that targets the FG-CC' cleft of Tim-3, a highly conserved binding site of phosphatidylserine (PtdSer) and carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). ML-T7 enhanced the survival and antitumor activity of primary CD8+ cytotoxic T lymphocytes (CTLs) and human chimeric antigen receptor (CAR) T cells and reduced their exhaustion in vitro and in vivo. In addition, ML-T7 promoted NK cells' killing activity and DC antigen-presenting capacity, consistent with the reported activity of Tim-3. ML-T7 strengthened DCs' functions through both Tim-3 and Tim-4, which is consistent with the fact that Tim-4 contains a similar FG-CC' loop. Intraperitoneal dosing of ML-T7 showed comparable tumor inhibitory effects to the Tim-3 blocking antibody. ML-T7 reduced syngeneic tumor progression in both wild-type and Tim-3 humanized mice and alleviated the immunosuppressive microenvironment. Furthermore, combined ML-T7 and anti-PD-1 therapy had greater therapeutic efficacy than monotherapy in mice, supporting further development of ML-T7 for tumor immunotherapy. Our study demonstrates a potential small molecule for selectively blocking Tim-3 and warrants further study.

Introducing Molecular Chaperones into the Causality and Prospective Management of Autoimmune Hepatitis

Molecular chaperones influence the immunogenicity of peptides and the activation of effector T cells, and their pathogenic roles in autoimmune hepatitis are unclear. Heat shock proteins are pivotal in the processing and presentation of peptides that activate CD8+ T cells. They can also induce regulatory B and T cells and promote immune tolerance. Tapasin and the transporter associated with antigen processing-binding protein influence the editing and loading of high-affinity peptides for presentation by class I molecules of the major histocompatibility complex. Their over-expression could enhance the autoimmune response, and their deficiency could weaken it. The lysosome-associated membrane protein-2a isoform in conjunction with heat shock cognate 70 supports the importation of cytosolic proteins into lysosomes. Chaperone-mediated autophagy can then process the peptides for activation of CD4+ T cells. Over-expression of autophagy in T cells may also eliminate negative regulators of their activity. The human leukocyte antigen B-associated transcript three facilitates the expression of class II peptide receptors, inhibits T cell apoptosis, prevents T cell exhaustion, and sustains the immune response. Immunization with heat shock proteins has induced immune tolerance in experimental models and humans with autoimmune disease by inducing regulatory T cells. Therapeutic manipulation of other molecular chaperones may promote T cell exhaustion and induce tolerogenic dendritic cells. In conclusion, molecular chaperones constitute an under-evaluated family of ancillary proteins that could affect the occurrence, severity, and outcome of autoimmune hepatitis. Clarification of their contributions to the immune mechanisms and clinical activity of autoimmune hepatitis could have therapeutic implications.

Control of immune cell function by the unfolded protein response

Initiating and maintaining optimal immune responses requires high levels of protein synthesis, folding, modification and trafficking in leukocytes, which are processes orchestrated by the endoplasmic reticulum. Importantly, diverse extracellular and intracellular conditions can compromise the protein-handling capacity of this organelle, inducing a state of 'endoplasmic reticulum stress' that activates the unfolded protein response (UPR). Emerging evidence shows that physiological or pathological activation of the UPR can have effects on immune cell survival, metabolism, function and fate. In this Review, we discuss the canonical role of the adaptive UPR in immune cells and how dysregulation of this pathway in leukocytes contributes to diverse pathologies such as cancer, autoimmunity and metabolic disorders. Furthermore, we provide an overview as to how pharmacological approaches that modulate the UPR could be harnessed to control or activate immune cell function in disease.

Incorporating the Molecular Mimicry of Environmental Antigens into the Causality of Autoimmune Hepatitis

Molecular mimicry between foreign and self-antigens has been implicated as a cause of autoimmune hepatitis in experimental models and cross-reacting antibodies in patients. This review describes the experimental and clinical evidence for molecular mimicry as a cause of autoimmune hepatitis, indicates the limitations and uncertainties of this premise, and encourages investigations that assess diverse environmental antigens as sources of disease-relevant molecular mimics. Pertinent articles were identified in PubMed using multiple search phrases. Several pathogens have linear or conformational epitopes that mimic the self-antigens of autoimmune hepatitis. The occurrence of an acute immune-mediated hepatitis after vaccination for severe acute respiratory syndrome (SARS)-associated coronavirus 2 (SARS-CoV-2) has suggested that vaccine-induced peptides may mimic disease-relevant tissue antigens. The intestinal microbiome is an under-evaluated source of gut-derived antigens that could also engage in molecular mimicry. Chaperone molecules may enhance the pathogenicity of molecular mimics, and they warrant investigation. Molecular mimics of immune dominant epitopes within cytochrome P450 IID6, the autoantigen most closely associated with autoimmune hepatitis, should be sought in diverse environmental antigens and assessed for pathogenicity. Avoidance strategies, dietary adjustments, vaccine improvement, and targeted manipulation of the intestinal microbiota may emerge as therapeutic possibilities. In conclusion, molecular mimicry may be a missing causality of autoimmune hepatitis. Molecular mimics of key immune dominant epitopes of disease-specific antigens must be sought in diverse environmental antigens. The ubiquity of molecular mimicry compels rigorous assessments of peptide mimics for immunogenicity and pathogenicity in experimental models. Molecular mimicry may complement epigenetic modifications as causative mechanisms of autoimmune hepatitis.

Tumor microenvironment signaling and therapeutics in cancer progression

Tumor development and metastasis are facilitated by the complex interactions between cancer cells and their microenvironment, which comprises stromal cells and extracellular matrix (ECM) components, among other factors. Stromal cells can adopt new phenotypes to promote tumor cell invasion. A deep understanding of the signaling pathways involved in cell-to-cell and cell-to-ECM interactions is needed to design effective intervention strategies that might interrupt these interactions. In this review, we describe the tumor microenvironment (TME) components and associated therapeutics. We discuss the clinical advances in the prevalent and newly discovered signaling pathways in the TME, the immune checkpoints and immunosuppressive chemokines, and currently used inhibitors targeting these pathways. These include both intrinsic and non-autonomous tumor cell signaling pathways in the TME: protein kinase C (PKC) signaling, Notch, and transforming growth factor (TGF-β) signaling, Endoplasmic Reticulum (ER) stress response, lactate signaling, Metabolic reprogramming, cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) and Siglec signaling pathways. We also discuss the recent advances in Programmed Cell Death Protein 1 (PD-1), Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA4), T-cell immunoglobulin mucin-3 (TIM-3) and Lymphocyte Activating Gene 3 (LAG3) immune checkpoint inhibitors along with the C-C chemokine receptor 4 (CCR4)- C-C class chemokines 22 (CCL22)/ and 17 (CCL17), C-C chemokine receptor type 2 (CCR2)- chemokine (C-C motif) ligand 2 (CCL2), C-C chemokine receptor type 5 (CCR5)- chemokine (C-C motif) ligand 3 (CCL3) chemokine signaling axis in the TME. In addition, this review provides a holistic understanding of the TME as we discuss the three-dimensional and microfluidic models of the TME, which are believed to recapitulate the original characteristics of the patient tumor and hence may be used as a platform to study new mechanisms and screen for various anti-cancer therapies. We further discuss the systemic influences of gut microbiota in TME reprogramming and treatment response. Overall, this review provides a comprehensive analysis of the diverse and most critical signaling pathways in the TME, highlighting the associated newest and critical preclinical and clinical studies along with their underlying biology. We highlight the importance of the most recent technologies of microfluidics and lab-on-chip models for TME research and also present an overview of extrinsic factors, such as the inhabitant human microbiome, which have the potential to modulate TME biology and drug responses.

PD-1 and TIM-3 differentially regulate subsets of mouse IL-17A-producing γδ T cells

IL-17A-producing γδ T cells in mice consist primarily of Vγ6+ tissue-resident cells and Vγ4+ circulating cells. How these γδ T cell subsets are regulated during homeostasis and cancer remains poorly understood. Using single-cell RNA sequencing and flow cytommetry, we show that lung Vγ4+ and Vγ6+ cells from tumor-free and tumor-bearing mice express contrasting cell surface molecules as well as distinct co-inhibitory molecules, which function to suppress their expansion. Vγ6+ cells express constitutively high levels of PD-1, whereas Vγ4+ cells upregulate TIM-3 in response to tumor-derived IL-1β and IL-23. Inhibition of either PD-1 or TIM-3 in mammary tumor-bearing mice increased Vγ6+ and Vγ4+ cell numbers, respectively. We found that genetic deletion of γδ T cells elicits responsiveness to anti-PD-1 and anti-TIM-3 immunotherapy in a mammary tumor model that is refractory to T cell checkpoint inhibitors, indicating that IL-17A-producing γδ T cells instigate resistance to immunotherapy. Together, these data demonstrate how lung IL-17A-producing γδ T cell subsets are differentially controlled by PD-1 and TIM-3 in steady-state and cancer.

MicroRNAs with Multiple Targets of Immune Checkpoints, as a Potential Sensitizer for Immune Checkpoint Inhibitors in Breast Cancer Treatment

Breast cancer is the most common cancer type and the leading cause of cancer-associated mortality in women worldwide. In recent years, immune checkpoint inhibitors (ICIs) have made significant progress in the treatment of breast cancer, yet there are still a considerable number of patients who are unable to gain lasting and ideal clinical benefits by immunotherapy alone, which leads to the development of a combination regimen as a novel research hotspot. Furthermore, one miRNA can target several checkpoint molecules, mimicking the therapeutic effect of a combined immune checkpoint blockade (ICB), which means that the miRNA therapy has been considered to increase the efficiency of ICIs. In this review, we summarized potential miRNA therapeutics candidates which can affect multiple targets of immune checkpoints in breast cancer with more therapeutic potential, and the obstacles to applying miRNA therapeutically through the analyses of the resources available from a drug target perspective. We also included the content of "too many targets for miRNA effect" (TMTME), combined with applying TargetScan database, to discuss adverse events. This review aims to ignite enthusiasm to explore the application of miRNAs with multiple targets of immune checkpoint molecules, in combination with ICIs for treating breast cancer.

Decoding endoplasmic reticulum stress signals in cancer cells and antitumor immunity

The tumor microenvironment (TME) provokes endoplasmic reticulum (ER) stress in malignant cells and infiltrating immune populations. Sensing and responding to ER stress is coordinated by the unfolded protein response (UPR), an integrated signaling pathway governed by three ER stress sensors: activating transcription factor (ATF6), inositol-requiring enzyme 1α (IRE1α), and protein kinase R (PKR)-like ER kinase (PERK). Persistent UPR activation modulates malignant progression, tumor growth, metastasis, and protective antitumor immunity. Hence, therapies targeting ER stress signaling can be harnessed to elicit direct tumor killing and concomitant anticancer immunity. We highlight recent findings on the role of the ER stress responses in onco-immunology, with an emphasis on genetic vulnerabilities that render tumors highly sensitive to therapeutic UPR modulation.

Metabolic regulation and function of T helper cells in neuroinflammation

Neuroinflammatory conditions such as multiple sclerosis (MS) are initiated by pathogenic immune cells invading the central nervous system (CNS). Autoreactive CD4⁺ T helper cells are critical players that orchestrate the immune response both in MS and in other neuroinflammatory autoimmune diseases including animal models that have been developed for MS. T helper cells are classically categorized into different subsets, but heterogeneity exists within these subsets. Untangling the more complex regulation of these subsets will clarify their functional roles in neuroinflammation. Here, we will discuss how differentiation, immune checkpoint pathways, transcriptional regulation and metabolic factors determine the function of CD4⁺ T cell subsets in CNS autoimmunity. T cells rely on metabolic reprogramming for their activation and proliferation to meet bioenergetic demands. This includes changes in glycolysis, glutamine metabolism and polyamine metabolism. Importantly, these pathways were recently also implicated in the fine tuning of T cell fate decisions during neuroinflammation. A particular focus of this review will be on the Th17/Treg balance and intra-subset functional states that can either promote or dampen autoimmune responses in the CNS and thus affect disease outcome. An increased understanding of factors that could tip CD4⁺ T cell subsets and populations towards an anti-inflammatory phenotype will be critical to better understand neuroinflammatory diseases and pave the way for novel treatment paradigms.

Tim-3 adapter protein Bat3 acts as an endogenous regulator of tolerogenic dendritic cell function

Dendritic cells (DCs) sense environmental cues and adopt either an immune-stimulatory or regulatory phenotype, thereby fine-tuning immune responses. Identifying endogenous regulators that determine DC function can thus inform the development of therapeutic strategies for modulating the immune response in different disease contexts. Tim-3 plays an important role in regulating immune responses by inhibiting the activation status and the T cell priming ability of DC in the setting of cancer. Bat3 is an adaptor protein that binds to the tail of Tim-3; therefore, we studied its role in regulating the functional status of DCs. In murine models of autoimmunity (experimental autoimmune encephalomyelitis) and cancer (MC38-OVA-implanted tumor), lack of Bat3 expression in DCs alters the T cell compartment-it decreases TH1, TH17 and cytotoxic effector cells, increases regulatory T cells, and exhausted CD8+ tumor-infiltrating lymphocytes, resulting in the attenuation of autoimmunity and acceleration of tumor growth. We found that Bat3 expression levels were differentially regulated by activating versus inhibitory stimuli in DCs, indicating a role for Bat3 in the functional calibration of DC phenotypes. Mechanistically, loss of Bat3 in DCs led to hyperactive unfolded protein response and redirected acetyl-coenzyme A to increase cell intrinsic steroidogenesis. The enhanced steroidogenesis in Bat3-deficient DC suppressed T cell response in a paracrine manner. Our findings identified Bat3 as an endogenous regulator of DC function, which has implications for DC-based immunotherapies.

An Emerging Role of TIM3 Expression on T Cells in Chronic Kidney Inflammation

T cell immunoglobulin domain and mucin domain 3 (TIM3) was initially identified as an inhibitory molecule on IFNγ-producing T cells. Further research discovered the broad expression of TIM3 on different immune cells binding to multiple ligands. Apart from its suppressive effects on the Th1 cells, recent compelling experiments highlighted the indispensable role of TIM3 in the myeloid cell-mediated inflammatory response, supporting that TIM3 exerts pleiotropic effects on both adaptive and innate immune cells in a context-dependent manner. A large number of studies have been conducted on TIM3 biology in the disease settings of infection, cancer, and autoimmunity. However, there is a lack of clinical evidence to closely evaluate the role of T cell-expressing TIM3 in the pathogenesis of chronic kidney disease (CKD). Here, we reported an intriguing case of Mycobacterium tuberculosis (Mtb) infection that was characterized by persistent overexpression of TIM3 on circulating T cells and ongoing kidney tubulointerstitial inflammation for a period of 12 months. In this case, multiple histopathological biopsies revealed a massive accumulation of recruited T cells and macrophages in the enlarged kidney and liver. After standard anti-Mtb treatment, repeated renal biopsy identified a dramatic remission of the infiltrated immune cells in the tubulointerstitial compartment. This is the first clinical report to reveal a time-course expression of TIM3 on the T cells, which is pathologically associated with the progression of severe kidney inflammation in a non-autoimmunity setting. Based on this case, we summarize the recent findings on TIM3 biology and propose a novel model of CKD progression due to the aberrant crosstalk among immune cells.