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Tumors escape immune surveillance by inducing various immunosuppressive pathways, including the activation of inhibitory receptors on tumor-infiltrating T cells. While monoclonal antibodies (mAbs) blocking programmed cell death 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) have been approved for multiple cancer indications, only a subset of patients benefit from immune checkpoint blockade therapies, highlighting the need for additional approaches. Therefore, the identification of new target molecules acting in distinct or complementary pathways in monotherapy or combination therapy with PD-1/PD-L1 blockade is gaining immense interest. T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif (ITIM) domains (TIGIT) has received considerable attention in cancer immunotherapy. Recently, anti-TIGIT mAb (tiragolumab) has demonstrated promising clinical efficacy in non-small cell lung cancer treatment when combined with an anti-PD-L1 drug (Tecentriq), leading to phase III trial initiation. TIGIT is expressed mainly on T and natural killer cells; it functions as an inhibitory checkpoint receptor, thereby limiting adaptive and innate immunity. CD226 competes for binding with the same ligands with TIGIT but delivers a positive stimulatory signal to the immune cells. This review discusses the recent discoveries regarding the roles of TIGIT and CD226 in immune cell function and their potential application in 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.

Over the past decade, immune checkpoint inhibitors (ICIs) have emerged as a revolutionary cancer treatment modality, offering long-lasting responses and survival benefits for a substantial number of cancer patients. However, the response rates to ICIs vary significantly among individuals and cancer types, with a notable proportion of patients exhibiting resistance or showing no response. Therefore, dual ICI combination therapy has been proposed as a potential strategy to address these challenges. One of the targets is TIGIT, an inhibitory receptor associated with T-cell exhaustion. TIGIT has diverse immunosuppressive effects on the cancer immunity cycle, including the inhibition of natural killer cell effector function, suppression of dendritic cell maturation, promotion of macrophage polarization to the M2 phenotype, and differentiation of T cells to regulatory T cells. Furthermore, TIGIT is linked with PD-1 expression, and it can synergize with PD-1/PD-L1 blockade to enhance tumor rejection. Preclinical studies have demonstrated the potential benefits of co-inhibition of TIGIT and PD-1/PD-L1 in enhancing anti-tumor immunity and improving treatment outcomes in several cancer types. Several clinical trials are underway to evaluate the safety and efficacy of TIGIT and PD-1/PD-L1 co-inhibition in various cancer types, and the results are awaited. This review provides an overview of the mechanisms of TIGIT and PD-1/PD-L1 co-inhibition in anti-tumor treatment, summarizes the latest clinical trials investigating this combination therapy, and discusses its prospects. Overall, co-inhibition of TIGIT and PD-1/PD-L1 represents a promising therapeutic approach for cancer treatment that has the potential to improve the outcomes of cancer patients treated with ICIs.

The emergence of immune checkpoint inhibitors (ICIs), mainly including anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) and anti-cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) monoclonal antibodies (mAbs), has shaped therapeutic landscape of some type of cancers. Despite some ICIs have manifested compelling clinical effectiveness in certain tumor types, the majority of patients still showed de novo or adaptive resistance. At present, the overall efficiency of immune checkpoint therapy remains unsatisfactory. Exploring additional immune checkpoint molecules is a hot research topic. Recent studies have identified several new immune checkpoint targets, like lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), T cell immunoglobulin and ITIM domain (TIGIT), V-domain Ig suppressor of T cell activation (VISTA), and so on. The investigations about these molecules have generated promising results in preclinical studies and/or clinical trials. In this review, we discussed the structure and expression of these newly-characterized immune checkpoints molecules, presented the current progress and understanding of them. Moreover, we summarized the clinical data pertinent to these recent immune checkpoint molecules as well as their application prospects.

Purpose of ReviewT-cell immunoglobulin and ITIM domain (TIGIT) is a next-generation inhibitory receptor with multiple antibodies under exploration in cancer therapy. Here, we review the available data from the early trials and overview upcoming clinical trials on anti-TIGIT antibodies.Recent FindingsThere is a promising activity of anti-TIGIT, particularly in combination with anti-PD-1/PD-L1 in non-small cell lung cancer (NSCLC) with already phase 3 trials currently ongoing to confirm these early findings.SummaryNumerous anti-TIGIT antibodies are in clinical trials currently, and others are in preclinical development. Therefore, more data are expected in the next few years regarding the efficacy of this new checkpoint inhibitor in multiple solid and hematologic malignancies. However, preliminary data are promising, and anti-TIGIT treatment seems to confer more favorable responses when combined with anti-PD-1/anti-PD-L1 compared to either agent alone.

[This corrects the article DOI: 10.3389/fimmu.2025.1677998.].

CD155 is the fifth member in the nectin‐like molecule family, and functions as the receptor of poliovirus; therefore, CD155 is also referred to as necl‐5, or PVR. As an immunoglobulin‐like adhesion molecule, CD155 is involved in cell motility, and natural killer and T cell‐mediated immunity. CD155 is barely or weakly expressed in various normal human tissues, but frequently overexpressed in human malignant tumors. CD155 overexpression promotes tumor cell invasion and migration, and is associated with tumor progression and poor prognosis. As the ligand for both costimulatory receptor CD226 and coinhibitory receptor TIGIT and CD96 on natural killer and T cells, CD155 seems to play a dual role in oncoimmunity. However, some recent studies indicate that CD155 overexpression may induce tumor immune escape. Taken together, CD155 may be considered as a target for the treatment of tumors with CD155 overexpression. CD155 overexpression promotes tumor cell invasion and migration, and is associated with tumor progression and poor prognosis. As the ligand for both costimulatory receptor CD226 and coinhibitory receptor TIGIT and CD96 on NK and T cells, CD155 seems to play a dual role in oncoimmunity. Some recent studies indicate that CD155 overexpression may induce tumor immune escape.

Lung cancer (LC) is the leading cause of cancer-related mortality worldwide, with non-small-cell lung cancer (NSCLC) representing 85–90% of cases. Despite the efficacy of PD-1/PD-L1 immune checkpoint inhibitors, primary and acquired resistance highlight the need for novel immunotherapeutic strategies. A systematic review of the literature from 2020 to 2025 was conducted according to the PICO model. Six studies were included, encompassing phase I–III clinical trials. The analysis focused on efficacy, safety, and emerging therapeutic strategies targeting TIGIT in NSCLC. TIGIT blockade enhances cytotoxic T lymphocyte and natural killer (NK) cell activity, strengthening antitumor immunity. Clinical trials, particularly with the monoclonal antibody tiragolumab combined with PD-1/PD-L1 inhibitors, show promising synergistic effects. Emerging strategies, including bispecific antibodies (e.g., TIGIT/PD-1 and TIGIT/PD-L1) and experimental cell therapies, are under investigation to further improve the antitumor response. Anti-TIGIT therapies represent a highly promising approach in NSCLC. While phase III data remain limited, biomarker-driven, well-designed trials are essential. If validated, TIGIT blockade could become a key addition to immuno-oncology treatment strategies for NSCLC.

Neoadjuvant systemic therapy (NST) is standard for locally advanced breast cancer (BC), yet predictors of pathological complete response (pCR) remain elusive. While Natural Killer (NK) cells are vital for anti-tumor response, their specific receptor dynamics during NST are poorly defined. This study provides a high-dimensional characterization of the peripheral NK cell landscape and immune signatures associated with therapeutic success. This prospective cohort study included 34 BC patients and 35 healthy donors (HD). Clinical characteristics were collected, and peripheral blood NK cell subsets were evaluated. We utilized high-parameter flow cytometry and unsupervised clustering (UMAP) to longitudinally track NK cell phenotypes (NKG2D, DNAM-1, PD-1, TIGIT) pre- and post-NST. NK cell cytotoxicity was evaluated, and serum levels of related IL-17A (interleukin), IL-2, IL-4, IL-10, IL-6, TNF-α (tumor necrosis factor-alpha), Fas, sFasL, IFN-γ (interferon-gamma), and Granzyme A were analyzed. Patients exhibited distinct NK cell profiles according to the pathological response. Only 12 BC patients achieved pCR. These patients showed improved NK cell cytotoxicity and higher concentrations of IL-2, TNF-α, sFASL, and Granzyme B after treatment compared with Non-pCR patients. In contrast, in Non-pCR patients, the percentages of CD56bright NK cells increased after neoadjuvant therapy, whereas the more cytotoxic CD56dim NK cell population decreased. Additionally, NK cells from Non-pCR patients exhibited higher co-expression of inhibitory checkpoints (TIGIT and PD-1), indicating reduced NK cell function. Otherwise, pCR patients displayed a more favorable balance of activating receptors (NKG2D and DNAM-1), and a favorable shift in the TIGIT/DNAM-1 activating-to-inhibitory axis. This study highlights the potential role of NK cells in determining the response to neoadjuvant therapy in BC patients. Those who achieved pCR showed enhanced NK cell activity and higher expression of activating receptors. Moreover, NK cells from Non-pCR patients showed lower cytotoxicity and higher expression of inhibitory receptors. These results suggest that NK cell phenotype evaluation could serve as a biomarker of treatment response in patients with BC. They also showed that the TIGIT/DNAM-1 axis can be a critical determinant of pCR.

Treatment strategies for patients with advanced solid tumors have traditionally been based on three different paradigms: surgery, cytotoxics (chemotherapy or radiation therapy) and targeted therapies. Immunotherapy has emerged as a novel treatment paradigm in our armamentarium. Unfortunately, most patients still do not benefit from immunotherapy. These patients often have “cold tumors” characterized by a paucity of effector T cells in the tumor microenvironment, low mutational load, low neoantigen burden and often an immunosuppressive tumor microenvironment. TIGIT is an immunoreceptor inhibitory checkpoint that has been implicated in tumor immunosurveillance. Expression of TIGIT has been demonstrated in both NK cells and T cells and plays a role in their activation and maturation. TIGIT competes with immunoactivator receptor CD226 (DNAM-1) for the same set of ligands: CD155 (PVR or poliovirus receptor) and CD112 (Nectin-2 or PVRL2). TIGIT’s role in tumor immunosurveillance is analogous to the PD-1/PD-L1 axis in tumor immunosuppression. Both TIGIT and PD-1 are upregulated in a variety of different cancers. Anti-TIGIT antibodies have demonstrated synergy with anti-PD-1/PD-L1 antibodies in pre-clinical models. Currently, there are multiple first-in-man phase I trials hoping to exploit this new pathway and improve response rates with existing immunotherapies.