Establishment of engineered cell-based assays mediating LAG3 and PD1 immune suppression enables potency measurement of blocking antibodies and assessment of signal transduction

Immuno-Oncology: New Insights into Targets and Therapies

The role of immunotherapy in the care of surgical oncology patients promises to expand as investigators and clinicians evaluate new targets and approaches. Currently active clinical trials evaluate new immune checkpoints, including lymphocyte activation gene 3, T cell immunoreceptor with Ig and ITIM domains, and killer Ig-like receptor 2DL1/2L3. Vaccines delivered through mRNA have demonstrated exciting results in early clinical trials and hold promise for expanded application. Investigational approaches include dendritic cell vaccines, peptide vaccines, cytokines therapies, and cellular therapies. These studies have the potential to revolutionize the management of surgical oncology patients and promote durable cures following surgical resection.

The immune checkpoint receptor LAG3: Structure, function, and target for cancer immunotherapy

Lymphocyte activation gene 3 protein (LAG3) is an immune checkpoint receptor that is highly upregulated on exhausted T cells in the tumor microenvironment. LAG3 transmits inhibitory signals to T cells upon binding to MHC class II and other ligands, rendering T cells dysfunctional. Consequently, LAG3 is a major target for cancer immunotherapy with many anti-LAG3 monoclonal antibodies (mAbs) that block LAG3 inhibitory activity in clinical trials. In this review, we examine the molecular basis for LAG3 function in light of recently determined crystal and cryoEM structures of this inhibitory receptor. We review what is known about LAG3 interactions with MHC class II, its canonical ligand, and the newly discovered ligands FGL1 and the T cell receptor (TCR)-CD3 complex, including current controversies over the relative importance of these ligands. We then address the development and mechanisms of action of anti-LAG3 mAbs in clinical trials for cancer immunotherapy. We discuss new strategies to therapeutically target LAG3 using mAbs that not only block the LAG3-MHC class II interaction, but also LAG3 interactions with FGL1 or TCR-CD3, or that disrupt LAG3 dimerization. Finally, we assess the possibility of developing mAbs that enhance, rather than block, LAG3 inhibitory activity as treatments for autoimmune diseases.

Redefining the battle against colorectal cancer: a comprehensive review of emerging immunotherapies and their clinical efficacy

Colorectal cancer (CRC) is the third most common cancer globally and presents a significant challenge owing to its high mortality rate and the limitations of traditional treatment options such as surgery, radiotherapy, and chemotherapy. While these treatments are foundational, they are often poorly effective owing to tumor resistance. Immunotherapy is a groundbreaking alternative that has recently emerged and offers new hope for success by exploiting the body's own immune system. This article aims to provide an extensive review of clinical trials evaluating the efficacy of various immunotherapies, including CRC vaccines, chimeric antigen receptor T-cell therapies, and immune checkpoint inhibitors. We also discuss combining CRC vaccines with monoclonal antibodies, delve into preclinical studies of novel cancer vaccines, and assess the impact of these treatment methods on patient outcomes. This review seeks to provide a deeper understanding of the current state of CRC treatment by evaluating innovative treatments and their potential to redefine the prognosis of patients with CRC.

Novel immune checkpoint targets: A promising therapy for cancer treatments

The immune system frequently comprises immunological checkpoints. They serve as a barrier to keep the immune system from overreacting and damaging cells that are robust. Immune checkpoint inhibitors (ICIs) are utilized in immunotherapy to prevent the synergy of partner proteins of checkpoint proteins with auxiliary proteins. Moreover, the T cells may target malignant cells since the "off" signal cannot be conveyed. ICIs, which are mostly composed of monoclonal antibodies (mAbs) against cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and anti- programmed death-1/programmed ligand 1 (anti-PD-1/PD-L1), might transform the context of cancer therapy. Further, more patients continued to exhibit adaptive resistance, even though several ICIs demonstrated convincing therapeutic benefits in selective tumor types. Immune checkpoint therapy's overall effectiveness is still lacking at this time. A popular area of study involves investigating additional immune checkpoint molecules. Recent research has found a number of fresh immune checkpoint targets, including NKG2A ligands, TIGIT, B7-H6 ligands, Galectin 3, TIM3, and so on. These targets have been focus of the study, and recent investigational approaches have shown encouraging outcomes. In this review article, we covered the development and present level understanding of these recently identified immune checkpoint molecules, its effectiveness and limitations.

First-line immunotherapy in non-small cell lung cancer: how to select and where to go

INTRODUCTION

Immunotherapy (IO) has established a new milestone in lung cancer treatment. Several registrational studies have approved immune checkpoint inhibitors (ICIs) in different settings, including the metastatic nonsmall cell lung cancer (NSCLC). As well known, responders are just a certain proportion of patients; therefore, their selection by using predictive factors has stood out as a crucial issue to address in tailoring a patient-centered care.

AREAS COVERED

In our review we propose a detailed yet handy cross section on ICIs as first-line treatment in metastatic NSCLC, regarding indications, histological, clinical, and blood-based biomarkers, other than their mechanisms of resistance and new immunological actionable targets. We performed a literature search through PubMed entering keywords complying with crucial features of immunotherapy.

EXPERT OPINION

IO represents the backbone of lung cancer treatment. Trials are currently testing novel immune blockade agents assessing combinatorial approaches with standard ICIs, or antibody drug conjugates (ADC), harboring immunological targets. Perfecting patients' selection is an ongoing challenge and a more and more urgent need in order to best predict responders who will consistently benefit from it.

CryoEM structure of a therapeutic antibody (favezelimab) bound to human LAG3 determined using a bivalent Fab as fiducial marker

Lymphocyte activation gene 3 protein (LAG3) is an inhibitory receptor that is upregulated on exhausted T cells in tumors. LAG3 is a major target for cancer immunotherapy with many anti-LAG3 antibodies in clinical trials. However, there is no structural information on the epitopes recognized by these antibodies. We determined the single-particle cryoEM structure of a therapeutic antibody (favezelimab) bound to LAG3 to 3.5 Å resolution, revealing that favezelimab targets the LAG3-binding site for MHC class II, its canonical ligand. The small size of the complex between the conventional (monovalent) Fab of favezelimab and LAG3 (∼100 kDa) presented a challenge for cryoEM. Accordingly, we engineered a bivalent version of Fab favezelimab that doubled the size of the Fab-LAG3 complex and conferred a highly identifiable shape to the complex that facilitated particle selection and orientation for image processing. This study establishes bivalent Fabs as new fiducial markers for cryoEM analysis of small proteins.

Targeting LAG-3, TIM-3, and TIGIT for cancer immunotherapy

In one decade, immunotherapy based on immune checkpoint blockades (ICBs) has become a new pillar of cancer treatment following surgery, radiation, chemotherapy, and targeted therapies. However, not all cancer patients benefit from single or combination therapy with anti-CTLA-4 and anti-PD-1/PD-L1 monoclonal antibodies. Thus, an increasing number of immune checkpoint proteins (ICPs) have been screened and their effectiveness evaluated in preclinical and clinical trials. Lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin and mucin-domain-containing-3 (TIM-3), and T cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif (ITIM) domain (TIGIT) constitute the second wave of immunotherapy targets that show great promise for use in the treatment of solid tumors and leukemia. To promote the research and clinical application of ICBs directed at these targets, we summarize their discovery, immunotherapy mechanism, preclinical efficiency, and clinical trial results in this review.

LAG-3 Inhibitors: Novel Immune Checkpoint Inhibitors Changing the Landscape of Immunotherapy

One of the most important steps forward in the management of cancer was the discovery of immunotherapy. It has become an essential pillar in the treatment paradigm of cancer patients. Unfortunately, despite the various options presented with immune checkpoint inhibitors (ICIs), the benefit is still limited to select patients and the vast majority of these patients gain either minimal benefit or eventually progress, leaving an unmet need for the development of novel therapeutic agents and strategies. Lymphocyte activation gene-3 (LAG-3), an immune checkpoint receptor protein, is a molecule found on the surface of activated T-cells. It plays a major role in negatively regulating T-cell function thereby providing tumors with an immune escape in the tumor microenvironment (TME). Given its importance in regulating the immune system, LAG-3 has been considered as a promising target in oncology and precision medicine. To date, two LAG-3-directed agents (eftilagimod alpha and relatlimab) have been approved in combination with programmed death-1 (PD-1) inhibitors in the setting of advanced solid tumors. In this review, we discuss the structure of LAG-3, its mechanism of action, and its interaction with its ligands. We also shed light on the emerging treatments targeting LAG-3 for the treatment of solid tumors.

Investigating combination benefit of PD1 and LAG3 co-blockade using an engineered cellular bioassay

LAG3 and PD1 are both immunomodulatory receptor that act by inhibiting activation of T cells, producing a more immunosuppressive environment. Even with the recent clinical success of PD1 and LAG3 co-blockade, signal transduction downstream of LAG3 remains largely unknown. We have leveraged an engineered Jurkat (T cell) and Raji (APC) co-culture system to assess simultaneous blockade of PD1 and LAG3 pathways using antibodies. RNA-Seq analysis of cell pellets individually treated with LAG3 or PD1 antibodies revealed modest immune activation however, 5-fold more genes were upregulated upon combination treatment. There were increases in costimulatory genes like CD28, CD5, CD6 as well as intracellular signaling molecules like LCP2 and ITK. Given the role of ERK in immune activation of T cells, pERK levels of Jurkat cells in the assay were evaluated. A very modest activation of pERK was observed with anti-LAG3 compared to anti-PD1 but a combination treatment resulted in prolonged ERK phosphorylation. Treatment of Jurkat cells with a commercial phosphatase inhibitor NSC87877 which can impact many phosphatases resulted in immune activation, measured by increased IL2 levels, only in the presence of LAG3. When NSC87877 was combined with the PD1 antibody, it could phenocopy combination benefit of PD1 and LAG3 blocking antibodies. CD28 has a recognized role in PD1 signaling but the impact on LAG3 signaling remains unknown. CD28 knockout in Jurkat cells affected overall IL-2 response of both LAG3 and PD1 antibody treatment but still retained combination benefit. Taken together this reductionist system highlights differences in downstream effects of LAG3 and PD1 blockade and we believe that the assay may have further utility to dissect convergence of both signaling pathways and augment studies in primary cells.

Approaches for development of LAG-3 inhibitors and the promise they hold as anticancer agents

INTRODUCTION

LAG-3 is considered to be the third point of immunological control in relation to clinical trials that address cancer treatment, only behind PD-1 and CTLA-4, due to its role as a suppressor of the immune response and enhancer of differentiation of Treg cells.

AREAS COVERED

The authors focus on emphasizing the strategy of development of LAG-3 inhibitors to develop anticancer therapeutics, especially from the perspective of designing new monoclonal and bispecific antibodies against LAG-3. This article also covers details of patents and clinical trials of LAG-3 inhibitors reported in the literature. In addition, we highlight as future research challenges the design and development of peptides and small molecules as inhibitors of LAG-3 function.

EXPERT OPINION

Three approaches have been used for the development of LAG-3 inhibitors, and they include inhibitory LAG-3 binding peptides and antagonist monoclonal and multispecific antibodies. These approaches include more than 100 clinical trials of 21 molecules that bind to LAG-3 and block its binding to MHC II. However, these approaches do not cover the design and development of peptides and small molecules that could inhibit the function of LAG-3, for which it is necessary to develop new alternatives that cover this gap.

LAG-3 as a Potent Target for Novel Anticancer Therapies of a Wide Range of Tumors

LAG-3 (Lymphocyte activation gene 3) protein is a checkpoint receptor that interacts with LSEC-tin, Galectin-3 and FGL1. This interaction leads to reduced production of IL-2 and IFN-γ. LAG-3 is widely expressed in different tumor types and modulates the tumor microenvironment through immunosuppressive effects. Differential expression in various tumor types influences patient prognosis, which is often associated with coexpression with immune checkpoint inhibitors, such as TIM-3, PD-1 and CTLA-4. Here, we discuss expression profiles in different tumor types. To date, many clinical trials have been conducted using LAG-3 inhibitors, which can be divided into anti-LAG-3 monoclonal antibodies, anti-LAG-3 bispecifics and soluble LAG-3-Ig fusion proteins. LAG-3 inhibitors supress T-cell proliferation and activation by disallowing for the interaction between LAG-3 to MHC-II. The process enhances anti-tumor immune response. In this paper, we will review the current state of knowledge on the structure, function and expression of LAG-3 in various types of cancer, as well as its correlation with overall prognosis, involvement in cell-based therapies and experimental medicine. We will consider the role of compounds targeting LAG-3 in clinical trials both as monotherapy and in combination, which will provide data relating to the efficacy and safety of proposed drug candidates.

LAG3 ectodomain structure reveals functional interfaces for ligand and antibody recognition

The immune checkpoint receptor lymphocyte activation gene 3 protein (LAG3) inhibits T cell function upon binding to major histocompatibility complex class II (MHC class II) or fibrinogen-like protein 1 (FGL1). Despite the emergence of LAG3 as a target for next-generation immunotherapies, we have little information describing the molecular structure of the LAG3 protein or how it engages cellular ligands. Here we determined the structures of human and murine LAG3 ectodomains, revealing a dimeric assembly mediated by Ig domain 2. Epitope mapping indicates that a potent LAG3 antagonist antibody blocks interactions with MHC class II and FGL1 by binding to a flexible 'loop 2' region in LAG3 domain 1. We also defined the LAG3-FGL1 interface by mapping mutations onto structures of LAG3 and FGL1 and established that FGL1 cross-linking induces the formation of higher-order LAG3 oligomers. These insights can guide LAG3-based drug development and implicate ligand-mediated LAG3 clustering as a mechanism for disrupting T cell activation.

Detection of cell-cell interactions via photocatalytic cell tagging

The growing appreciation of immune cell-cell interactions within disease environments has led to extensive efforts to develop immunotherapies. However, characterizing complex cell-cell interfaces in high resolution remains challenging. Thus, technologies leveraging therapeutic-based modalities to profile intercellular environments offer opportunities to study cell-cell interactions with molecular-level insight. We introduce photocatalytic cell tagging (PhoTag) for interrogating cell-cell interactions using single-domain antibodies (VHHs) conjugated to photoactivatable flavin-based cofactors. Following irradiation with visible light, the flavin photocatalyst generates phenoxy radical tags for targeted labeling. Using this technology, we demonstrate selective synaptic labeling across the PD-1/PD-L1 axis in antigen-presenting cell-T cell systems. In combination with multiomics single-cell sequencing, we monitored interactions between peripheral blood mononuclear cells and Raji PD-L1 B cells, revealing differences in transient interactions with specific T cell subtypes. The utility of PhoTag in capturing cell-cell interactions will enable detailed profiling of intercellular communication across different biological systems.

Clinical landscape of LAG-3-targeted therapy

Lymphocyte-activated gene 3 (LAG-3) is a cell surface inhibitory receptor and a key regulator of immune homeostasis with multiple biological activities related to T-cell functions. LAG-3 is considered a next-generation immune checkpoint of clinical importance, right next to programmed cell death protein 1 (PD-1) and cytotoxic T-cell lymphocyte antigen-4 (CTLA-4). Indeed, it is the third inhibitory receptor to be exploited in human anticancer immunotherapies. Several LAG-3-antagonistic immunotherapies are being evaluated at various stages of preclinical and clinical development. In addition, combination therapies blocking LAG-3 together with other immune checkpoints are also being evaluated at preclinical and clinical levels. Indeed, the co-blockade of LAG-3 with PD-1 is demonstrating encouraging results. A new generation of bispecific PD-1/LAG-3-blocking agents have also shown strong capacities to specifically target PD-1+ LAG-3+ highly dysfunctional T cells and enhance their proliferation and effector activities. Here we identify and classify preclinical and clinical trials conducted involving LAG-3 as a target through an extensive bibliographic research. The current understanding of LAG-3 clinical applications is summarized, and most of the publically available data up to date regarding LAG-3-targeted therapy preclinical and clinical research and development are reviewed and discussed.

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LAG-3 is a highly important next-generation immune checkpoint molecule.

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Ninety-seven clinical trials are evaluating at least 16 LAG-3-targeting molecules.

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Here we identify preclinical and clinical studies conducted involving LAG-3.

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Bispecific LAG-3 molecules are being developed, showing strong capacities.

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LAG-3/PD-1 co-blockade is demonstrating encouraging results.

Immune Checkpoint LAG3 and Its Ligand FGL1 in Cancer

LAG3 is the most promising immune checkpoint next to PD-1 and CTLA-4. High LAG3 and FGL1 expression boosts tumor growth by inhibiting the immune microenvironment. This review comprises four sections presenting the structure/expression, interaction, biological effects, and clinical application of LAG3/FGL1. D1 and D2 of LAG3 and FD of FGL1 are the LAG3-FGL1 interaction domains. LAG3 accumulates on the surface of lymphocytes in various tumors, but is also found in the cytoplasm in non-small cell lung cancer (NSCLC) cells. FGL1 is found in the cytoplasm in NSCLC cells and on the surface of breast cancer cells. The LAG3-FGL1 interaction mechanism remains unclear, and the intracellular signals require elucidation. LAG3/FGL1 activity is associated with immune cell infiltration, proliferation, and secretion. Cytokine production is enhanced when LAG3/FGL1 are co-expressed with PD-1. IMP321 and relatlimab are promising monoclonal antibodies targeting LAG3 in melanoma. The clinical use of anti-FGL1 antibodies has not been reported. Finally, high FGL1 and LAG3 expression induces EGFR-TKI and gefitinib resistance, and anti-PD-1 therapy resistance, respectively. We present a comprehensive overview of the role of LAG3/FGL1 in cancer, suggesting novel anti-tumor therapy strategies.

Systems-level conservation of the proximal TCR signaling network of mice and humans

We exploited traceable gene tagging in primary human T cells to establish the composition and dynamics of seven canonical TCR-induced protein signaling complexes (signalosomes) using affinity purification coupled with mass spectrometry (AP-MS). It unveiled how the LAT adaptor assembles higher-order molecular condensates and revealed that the proximal TCR-signaling network has a high degree of qualitative and quantitative conservation between human CD4+ and CD8+ T cells. Such systems-level conservation also extended across human and mouse T cells and unexpectedly encompassed protein–protein interaction stoichiometry. Independently of evolutionary considerations, our study suggests that a drug targeting the proximal TCR signaling network should behave similarly when applied to human and mouse T cells. However, considering that signaling differences likely exist between the distal TCR-signaling pathway of human and mouse, our fast-track AP-MS approach should be favored to determine the mechanism of action of drugs targeting human T cell activation. An opportunity is illustrated here using an inhibitor of the LCK protein tyrosine kinase as a proof-of-concept.

Combination Immune Checkpoint Blockade Enhances IL-2 and CD107a Production from HIV-Specific T Cells Ex Vivo in People Living with HIV on Antiretroviral Therapy

In people with HIV (PWH) on antiretroviral therapy (ART), immune dysfunction persists, including elevated expression of immune checkpoint (IC) proteins on total and HIV-specific T cells. Reversing immune exhaustion is one strategy to enhance the elimination of HIV-infected cells that persist in PWH on ART. We aimed to evaluate whether blocking CTL-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), T cell Ig domain and mucin domain 3 (TIM-3), T cell Ig and ITIM domain (TIGIT) and lymphocyte activation gene-3 (LAG-3) alone or in combination would enhance HIV-specific CD4⁺ and CD8⁺ T cell function ex vivo. Intracellular cytokine staining was performed using human PBMCs from PWH on ART (n = 11) and expression of CD107a, IFN-γ, TNF-α, and IL-2 was quantified with HIV peptides and Abs to IC. We found the following: 1) IC blockade enhanced the induction of CD107a and IL-2 but not IFN-γ and TNF-α in response to Gag and Nef peptides; 2) the induction of CD107a and IL-2 was greatest with multiple combinations of two Abs; and 3) Abs to LAG-3, CTLA-4, and TIGIT in combinations showed synergistic induction of IL-2 in HIV-specific CD8⁺ and CD107a and IL-2 production in HIV-specific CD4⁺ and CD8⁺ T cells. These results demonstrate that the combination of Abs to LAG-3, CTLA-4, or TIGIT can increase the frequency of cells expressing CD107a and IL-2 that associated with cytotoxicity and survival of HIV-specific CD4⁺ and CD8⁺ T cells in PWH on ART. These combinations should be further explored for an HIV cure.

A reporter gene assay for determining the biological activity of therapeutic antibodies targeting TIGIT

T cell immunoglobulin and ITIM domain (TIGIT) is a novel immune checkpoint that has been considered as a target in cancer immunotherapy. Current available bioassays for measuring the biological activity of therapeutic antibodies targeting TIGIT are restricted to mechanistic investigations because donor primary T cells are highly variable. Here, we designed a reporter gene assay comprising two cell lines, namely, CHO-CD112-CD3 scFv, which stably expresses CD112 (PVRL2, nectin-2) and a membrane-bound anti-CD3 single-chain fragment variable (scFv) as the target cell, and Jurkat-NFAT-TIGIT, which stably expresses TIGIT as well as the nuclear factor of activated T-cells (NFAT) response element-controlled luciferase gene, as the effector cell. The anti-CD3 scFv situated on the target cells activates Jurkat-NFAT-TIGIT cells through binding and crosslinking CD3 molecules of the effector cell, whereas interactions between CD112 and TIGIT prevent activation. The presence of anti-TIGIT mAbs disrupts their interaction, which in turn reverses the inactivation and luciferase expression. Optimization and validation studies have demonstrated that this assay is superior in terms of specificity, accuracy, linearity, and precision. In summary, this reliable and effective reporter gene assay may potentially be utilized in lot release control, stability assays, screening, and development of novel TIGIT-targeted therapeutic antibodies.

Research Progresses in Immunological Checkpoint Inhibitors for Breast Cancer Immunotherapy

Tumor immune escape refers to the phenomenon in which tumor cells escape the recognition and attack of the body’s immune system through various mechanisms so that they can survive and proliferate in vivo. The imbalance of immune checkpoint protein expression is the primary mechanism for breast cancer to achieve immune escape. Cytotoxic T lymphocyte antigen 4 (CTLA4) and programmed cell death protein 1 (PD-1)/programmed cell death protein-ligand 1 (PD-L1) are critical immune checkpoints for breast cancer. Immune checkpoint inhibitors block the checkpoint and relieve its inhibition effect on immune cells, reactivate T-cells and destroy cancer cells and restore the body’s ability to resist tumors. At present, immunological checkpoint inhibitors have made significant progress in breast cancer immunotherapy, and it is expected to become a new treatment for breast cancer.

Cyclophilin A is an endogenous ligand for the triggering receptor expressed on myeloid cells-2 (TREM2)

Triggering receptor expressed on myeloid cells 2 (TREM2) is a cell surface receptor expressed on macrophages, microglial cells, and pre-osteoclasts, and that participates in diverse cellular function, including inflammation, bone homeostasis, neurological development, and coagulation. In spite of the indispensable role of the TREM2 protein in the maintenance of immune homeostasis and osteoclast differentiation, the exact ligand for TREM2 has not yet been identified. Here, we report a putative TREM2 ligand which is secreted from MC38 cells and identified as a cyclophilin A (CypA). A specific interaction between CypA and TREM2 was shown at both protein and cellular levels. Exogenous CypA specifically interacted and co-localized with TREM2 in RAW264.7 cells, and the physical interactions were shown to regulate TREM2 signaling transduction. The Pro¹⁴⁴ residue in the extracellular domain of TREM2 was found to be the specific binding site of CypA. When considered together, this provides evidence that CypA interacts specifically with TREM2 as a potent ligand.

Molecular and Clinical Characterization of LAG3 in Breast Cancer Through 2994 Samples

Despite the promising impact of cancer immunotherapy targeting CTLA4 and PD1/PDL1, numerous cancer patients fail to respond. LAG3 (Lymphocyte Activating 3), also named CD233, serves as an alternative inhibitory receptor to be targeted in the clinic. The impacts of LAG3 on immune cell populations and coregulation of immune responses in breast cancer remain largely unknown. To characterize the role of LAG3 in breast cancer, we investigated transcriptome data and associated clinical information derived from 2,994 breast cancer patients. We estimated the landscape of the relationship between LAG3 and 10 types of cell populations of breast cancer. We investigated the correlation pattern between LAG3 and immune modulators in pancancer, particularly the synergistic role of LAG3 with other immune checkpoint members in breast cancer. LAG3 expression was closely related to the malignancy of breast cancer and may serve as a potential biomarker. LAG3 may play an important role in regulating the tumor immune microenvironment of T cells and other immune cells. More important, LAG3 may synergize with CTLA4, PD1/PDL1, and other immune checkpoints, thereby contributing more evidence to improve combination cancer immunotherapy by simultaneously targeting LAG3, PD1/PDL1, and CTLA4.

What Is on the Horizon for Novel Immunotherapies in Lung Cancer?

Programmed death (ligand) 1 checkpoint inhibitors have become standard treatment in patients with non-small cell lung cancer. Recently, combinations of nivolumab and ipilimumab have entered the clinic based on regulatory approval. Oftentimes, these checkpoint inhibitors are given in conjunction with chemotherapy. Through increased understanding of checkpoint evasion by cancer cells, many promising studies using combination therapies have continued to develop that aim to attack cancer cells by eliciting immunogenic responses through different modalities. Novel approaches include (1) using vaccines to trigger immune response, (2) combining multiple checkpoint inhibitors, (3) targeting inflammatory responses, (4) utilizing multitargeted tyrosine kinase inhibitors, (5) employing agonists of T-cell stimulators, and (6) applying specific biomarker antagonists to treat lung cancer patients. Herein, we discuss several studies that aim to answer what lies ahead in lung cancer treatment.

Using Machine Learning Modeling to Explore New Immune-Related Prognostic Markers in Non-Small Cell Lung Cancer

OBJECTIVE

To find new immune-related prognostic markers for non-small cell lung cancer (NSCLC).

METHODS

We found GSE14814 is related to NSCLC in GEO database. The non-small cell lung cancer observation (NSCLC-OBS) group was evaluated for immunity and divided into high and low groups for differential gene screening according to the score of immune evaluation. A single factor COX regression analysis was performed to select the genes related to prognosis. A prognostic model was constructed by machine learning, and test whether the model has a test efficacy for prognosis. A chip-in-chip non-small cell lung cancer chemotherapy (NSCLC-ACT) sample was used as a validation dataset for the same validation and prognostic analysis of the model. The coexpression genes of hub genes were obtained by pearson analysis and gene enrichment, function enrichment and protein interaction analysis. The tumor samples of patients with different clinical stages were detected by immunohistochemistry and the expression difference of prognostic genes in tumor tissues of patients with different stages was compared.

RESULTS

By screening, we found that LYN, C3, COPG2IT1, HLA.DQA1, and TNFRSF17 is closely related to prognosis. After machine learning, we constructed the immune prognosis model from these 5 genes, and the model AUC values were greater than 0.9 at three time periods of 1, 3, and 5 years; the total survival period of the low-risk group was significantly better than that of the high-risk group. The results of prognosis analysis in ACT samples were consistent with OBS groups. The coexpression genes are mainly involved B cell receptor signaling pathway and are mainly enriched in apoptotic cell clearance. Prognostic key genes are highly correlated with PDCD1, PDCD1LG2, LAG3, and CTLA4 immune checkpoints. The immunohistochemical results showed that the expression of COPG2IT1 and HLA.DQA1 in stage III increased significantly and the expression of LYN, C3, and TNFRSF17 in stage III decreased significantly compared with that of stage I. The experimental results are consistent with the previous analysis.

CONCLUSION

LYN, C3, COPG2IT1, LA.DQA1, and NFRSF17 may be new immune markers to judge the prognosis of patients with non-small cell lung cancer.

The Role of Immunomodulatory Receptors in the Pathogenesis of HIV Infection: A Therapeutic Opportunity for HIV Cure?

Immune activation is the hallmark of HIV infection and plays a role in the pathogenesis of the disease. In the context of suppressed HIV RNA replication by combination antiretroviral therapy (cART), there remains immune activation which is associated to the HIV reservoirs. Persistent virus contributes to a sustained inflammatory environment promoting accumulation of "activated/exhausted" T cells with diminished effector function. These T cells show increased expression of immunomodulatory receptors including Programmed cell death protein (PD1), Cytotoxic T Lymphocyte Associated Protein 4 (CTLA4), Lymphocyte activation gene 3 (LAG3), T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin domain containing 3 (TIM3) among others. More importantly, recent reports had demonstrated that, HIV infected T cells express checkpoint receptors, contributing to their survival and promoting maintenance of the viral reservoir. Therapeutic strategies are focused on viral reservoir elimination and/or those to achieve sustained cART-free virologic remission. In this review, we will discuss the immunological basis and the latest advances of the use of checkpoint inhibitors to treat HIV infection.

A reporter gene assay for measuring the bioactivity of anti-LAG-3 therapeutic antibodies

Although enormous success has been achieved with anti-PD-1/PD-L1 and anti-CTLA-4 monoclonal antibodies (mAbs), their unsatisfactory response rate in cancer patients has been driving the research and development of novel immune checkpoint inhibitors (ICIs). Anti-LAG-3 mAbs, as one of the most promising candidates, are now being tested for various human cancers at different stages of clinical trials. Here, we describe the development and validation of a reporter gene assay (RGA) to measure the bioactivity of anti-LAG-3 mAbs. We established the bioassay based on parental Raji cells and a Jurkat cell line stably transfected with human LAG-3 gene and luciferase reporter elements controlled by nuclear factor of activated T cell (NFAT) from the IL-2 promoter. After optimization of key parameters, the established RGA showed excellent precision, specificity, accuracy, and stability. The mechanism of action (MOA) relatedness and the excellent assay performance make the RGA suitable for the characterization, lot release, and stability test of anti-LAG-3 mAbs.

Microenvironment mapping via Dexter energy transfer on immune cells

Many disease pathologies can be understood through the elucidation of localized biomolecular networks, or microenvironments. To this end, enzymatic proximity labeling platforms are broadly applied for mapping the wider spatial relationships in subcellular architectures. However, technologies that can map microenvironments with higher precision have long been sought. Here, we describe a microenvironment-mapping platform that exploits photocatalytic carbene generation to selectively identify protein-protein interactions on cell membranes, an approach we term MicroMap (μMap). By using a photocatalyst-antibody conjugate to spatially localize carbene generation, we demonstrate selective labeling of antibody binding targets and their microenvironment protein neighbors. This technique identified the constituent proteins of the programmed-death ligand 1 (PD-L1) microenvironment in live lymphocytes and selectively labeled within an immunosynaptic junction.

A LAG-3-Specific Agonist Antibody for the Treatment of T Cell-Induced Autoimmune Diseases

T cells chronically stimulated with the same peptide tend to express exhaustion markers such as PD-1 or LAG-3. Deficiencies in the PD-1 and LAG-3 pathways have been linked to the development of autoimmune diseases. IMP761 is a LAG-3-specific humanized agonist Ab with immunosuppressive properties both in vitro and in vivo in an Ag-specific delayed-type hypersensitivity (DTH) model in the cynomolgus macaque (Macaca fascicularis). IMP761 inhibits TCR-mediated NFAT activation and Ag-induced human T cell proliferation and activation. In the DTH model, assessment of T cell infiltration and gene expression profile at the DTH biopsy site corresponds to immunosuppression of an Ag-induced T cell response. IMP761 is the first LAG-3-specific agonist product candidate, acting upstream on activated T cells, the root cause of self-Ag-specific T cell-induced autoimmune diseases.

The co-expression characteristics of LAG3 and PD-1 on the T cells of patients with breast cancer reveal a new therapeutic strategy

Many studies have shown a special interaction between LAG3 and PD-1 in T cell inhibition, while the co-expression and effect of LAG3 and PD-1 on T cells in breast cancer patients are still not very clear. Here, with strict exclusion criteria, 88 patients with breast cancer and 18 healthy controls were enrolled. The percentages of LAG3⁺PD-1⁺ T cells in their peripheral blood (PBL) and tumor infiltrating T cells (TIL) were analyzed by flow cytometry, which showed an increase in TILs but no difference in PBLs and presented differences in TILs in different molecular subtypes (P < 0.05). In triple-negative breast cancer (TNBC), the highest percentages were observed, while in ER+/PR+ breast cancer, the lowest percentages were observed; however, these percentages were not different in different clinical stages (P > 0.05). Immunohistochemical staining showed that the expression of their ligands, PD-L1, MHC class II molecular and FGL1, was inconsistent in different molecular subtypes and clinical stages. Analysis of the functions of T cells with different phenotypes showed that the proliferation and secretion capacity of LAG3⁺PD-1⁺ T cells was obviously exhausted, with more than a two-fold of decrease compared with the groups of single positive LAG3 or PD-1 (P < 0.05). Finally, in a mouse model of TNBC, the dual blockade of LAG3 and PD-1 was indicated to achieve a better anti-tumour effect than either one alone (P < 0.05), which may provide a new strategy for the immunoregulatory treatment of patients with TNBC in the future.

Cancer Immunotherapies Targeting Tumor-Associated Regulatory T Cells

Tumor-associated regulatory T cells (Tregs) are important effectors in the tumor microenvironment (TME), acting as accomplices in the promotion of tumor progression. Currently, the importance of removing the immunosuppressive activity in the TME has received its due attention, and Tregs have been focused on. The cytokine-receptor axes are among the essential signaling pathways in immunocytes, and tumor-associated Tregs are no exception. Therefore, manipulating cytokine-receptor pathways may be a promising effective strategy for treating various malignancies. Here, we summarize the classification, immunosuppressive mechanisms, existing immunotherapies, and potential biomarkers related to tumor-infiltrating Tregs to guide the development of effective cancer immunotherapies.

Characterization of a novel anti-human lymphocyte activation gene 3 (LAG-3) antibody for cancer immunotherapy

Lymphocyte activation gene 3 (LAG-3) is expressed on activated T cells, natural killer cells or B cells, and functions to negatively regulate homeostasis of these cells. Anti-LAG-3 antibodies might be useful for antitumor immunotherapy. In this study, we characterized a novel anti-LAG-3 antibody, LBL-007, which was isolated from a human antibody phage display library. LBL-007 was found to specifically bind to human LAG-3 antigen, but not to human CD4 or mouse LAG-3. LBL-007 bound activated T cells and promoted interleukin-2 secretion. LBL-007 internalization efficacy by endocytosis into different cells was better than that of another anti-LAG-3 antibody, relatlimab analog. Moreover, LBL-007 was able to block LAG-3 binding to MHC class II molecules and liver sinusoidal endothelial cell lectin, and block LAG-3-induced downstream signaling. In mice transplanted with colorectal cancer cells, treatment with either anti-PD-1 antibody or LBL-007 (10 mg/kg per mouse twice a week for three weeks) resulted in a significant delay in tumor growth compared with control IgG treatment, and their combination was even more effective. Serum LBL-007 levels were highly stable in monkeys after a single intravenous injection of LBL-007 at 3, 10, or 30 mg/kg. This study demonstrated that the combination of LBL-007 with an anti-PD-1 antibody is a promising antitumor regimen for immunotherapy of solid tumors in future that deserves further study.

Roles, function and relevance of LAG3 in HIV infection

HIV causes several forms of immune dysfunction that need to be addressed in a functional cure for HIV. Immune exhaustion describes a dysfunctional phenotype caused by chronic cellular activation. Lymphocyte activation gene-3 (LAG3) is one of several negative coreceptors known as immune checkpoints that contribute to this exhaustion phenotype. Antibodies targeting immune checkpoints are now used clinically to restore immunity against cancer and hold promise in restoring immunity during HIV infection. Here, we summarize current knowledge surrounding LAG3 and discuss its relevance during HIV infection and the potential for LAG3-targeting antibodies in a functional HIV cure.

Not All Immune Checkpoints Are Created Equal

Antibodies that block T cell inhibition via the immune checkpoints CTLA-4 and PD-1 have revolutionized cancer therapy during the last 15 years. T cells express additional inhibitory surface receptors that are considered to have potential as targets in cancer immunotherapy. Antibodies against LAG-3 and TIM-3 are currently clinically tested to evaluate their effectiveness in patients suffering from advanced solid tumors or hematologic malignancies. In addition, blockade of the inhibitory BTLA receptors on human T cells may have potential to unleash T cells to effectively combat cancer cells. Much research on these immune checkpoints has focused on mouse models. The analysis of animals that lack individual inhibitory receptors has shed some light on the role of these molecules in regulating T cells, but also immune responses in general. There are current intensive efforts to gauge the efficacy of antibodies targeting these molecules called immune checkpoint inhibitors alone or in different combinations in preclinical models of cancer. Differences between mouse and human immunology warrant studies on human immune cells to appreciate the potential of individual pathways in enhancing T cell responses. Results from clinical studies are not only highlighting the great benefit of immune checkpoint inhibitors for treating cancer but also yield precious information on their role in regulating T cells and other cells of the immune system. However, despite the clinical relevance of CTLA-4 and PD-1 and the high potential of the emerging immune checkpoints, there are still substantial gaps in our understanding of the biology of these molecules, which might prevent the full realization of their therapeutic potential. This review addresses PD-1, CTLA-4, BTLA, LAG-3, and TIM-3, which are considered major inhibitory immune checkpoints expressed on T cells. It provides summaries of our current conception of the role of these molecules in regulating T cell responses, and discussions about major ambiguities and gaps in our knowledge. We emphasize that each of these molecules harbors unique properties that set it apart from the others. Their distinct functional profiles should be taken into account in therapeutic strategies that aim to exploit these pathways to enhance immune responses to combat cancer.