TIGIT-Fc Promotes Antitumor Immunity

Nature killer cell for solid tumors: Current obstacles and prospective remedies in NK cell therapy and beyond

In recent years, cell therapy has emerged as an innovative treatment method for the management of clinical tumors following immunotherapy. Among them, Natural killer (NK) cell therapy has achieved a significant breakthrough in the treatment of hematological tumors. However, the therapeutic effectiveness of NK cells in the treatment of solid tumors remains challenging. With the progress of gene editing and culture techniques and their application to NK cell engineering, it is expected that NK cell therapy will revolutionize the treatment of solid tumors. In this review, we explore the discovery and biological properties of NK cells, their role in the tumor microenvironment, and the therapeutic strategies, clinical trials, challenges, and prospects of NK cells in the treatment of solid tumors.

CD8+ T-cell exhaustion: Impediment to triple-negative breast cancer (TNBC) immunotherapy

CD8+ T-cell exhaustion has been identified as a significant contributor to immunosuppression and immune escape in triple-negative breast cancer (TNBC). Dysfunction due to cell exhaustion is characterized by reduced effector capacity and sustained expression of inhibitory receptors (IRs). The factors contributing to CD8+ T-cell exhaustion are multifaceted, encompassing external influences such as the upregulation of IRs, reduction of effector cytokines, and internal changes within the immune cell, including transcriptomic alterations, epigenetic landscape remodeling, and metabolomic shifts. The impact of the altered TNBC tumor microenvironment (TME) on Tex is also a critical consideration. The production of exhausted CD8+ T-cells (CD8+ Tex) is positively correlated with poor prognosis and reduced response rates to immunotherapy in TNBC patients, underscoring the urgent need for the development of novel TNBC immunotherapeutic strategies that target the mechanisms of CD8+ T-cell exhaustion. This review delineates the dynamic trajectory of CD8+ T-cell exhaustion development in TNBC, provides an update on the latest research advancements in understanding its pathogenesis, and offers insights into potential immunotherapeutic strategies.

Targeting TIGIT for cancer immunotherapy: recent advances and future directions

As a newly identified checkpoint, T cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif (ITIM) domain (TIGIT) is highly expressed on CD4+ T cells, CD8+ T cells, natural killer (NK) cells, regulatory T cells (Tregs), and tumor-infiltrating lymphocytes (TILs). TIGIT has been associated with NK cell exhaustion in vivo and in individuals with various cancers. It not only modulates NK cell survival but also mediates T cell exhaustion. As the primary ligand of TIGIT in humans, CD155 may be the main target for immunotherapy due to its interaction with TIGIT. It has been found that the anti-programmed cell death protein 1 (PD-1) treatment response in cancer immunotherapy is correlated with CD155 but not TIGIT. Anti-TIGIT alone and in combination with anti-PD-1 agents have been tested for cancer immunotherapy. Although two clinical studies on advanced lung cancer had positive results, the TIGIT-targeted antibody, tiragolumab, recently failed in two new trials. In this review, we highlight the current developments on TIGIT for cancer immunotherapy and discuss the characteristics and functions of TIGIT.

Oncolytic adenoviruses expressing checkpoint inhibitors for cancer therapy

Despite the remarkable success of immune checkpoint inhibitors (ICIs), primary resistance to ICIs causes only subsets of patients to achieve durable responses due to the complex tumor microenvironment (TME). Oncolytic viruses (OVs) can overcome the immunosuppressive TME and promote systemic antitumor immunity in hosts. Engineered OVs armed with ICIs would likely have improved effectiveness as a cancer therapy. According to the diverse immune cell landscapes among different types of tumors, we rationally and precisely generated three recombinant oncolytic adenoviruses (OAds): OAd-SIRPα-Fc, OAd-Siglec10-Fc and OAd-TIGIT-Fc. These viruses were designed to locally deliver SIRPα-Fc, Siglec10-Fc or TIGIT-Fc fusion proteins recognizing CD47, CD24 or CD155, respectively, in the TME to achieve enhanced antitumor effects. Our results suggested that OAd-SIRPα-Fc and OAd-Siglec10-Fc both showed outstanding efficacy in tumor suppression of macrophage-dominated tumors, while OAd-TIGIT-Fc showed the best antitumor immunity in CD8+ T-cell-dominated tumors. Importantly, the recombinant OAds activated an inflammatory immune response and generated long-term antitumor memory. In addition, the combination of OAd-Siglec10-Fc with anti-PD-1 significantly enhanced the antitumor effect in a 4T1 tumor model by remodeling the TME. In summary, rationally designed OAds expressing ICIs tailored to the immune cell landscape in the TME can precisely achieve tumor-specific immunotherapy of 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.

Focusing on NK cells and ADCC: A promising immunotherapy approach in targeted therapy for HER2-positive breast cancer

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer has a high metastatic potential. Monoclonal antibodies (mAbs) that target HER2, such as trastuzumab and pertuzumab, are the cornerstone of adjuvant therapy for HER2-positive breast cancer. A growing body of preclinical and clinical evidence points to the importance of innate immunity mediated by antibody-dependent cellular cytotoxicity (ADCC) in the clinical effect of mAbs on the resulting anti-tumor response. In this review, we provide an overview of the role of natural killer (NK) cells and ADCC in targeted therapy of HER2-positive breast cancer, including the biological functions of NK cells and the role of NK cells and ADCC in anti-HER2 targeted drugs. We then discuss regulatory mechanisms and recent strategies to leverage our knowledge of NK cells and ADCC as an immunotherapy approach for HER2-positive breast cancer.

Anticancer natural products targeting immune checkpoint protein network

Normal cells express surface proteins that bind to immune checkpoint proteins on immune cells to turn them off, whereby the immune system does not attack normal healthy cells. Cancer cells can also utilize this same protective mechanism by expressing surface proteins that can interact with checkpoint proteins on immune cells to overcome the immune surveillance. Immunotherapy is making the best use of the body's own immune system to reinforce anti-tumor responses. The most generally used immunotherapy is the control of immune checkpoints including the cytotoxic T lymphocyte-associated molecule 4 (CTLA-4), programmed cell deathreceptor 1 (PD-1), or programmed cell death ligand-1 (PD-L1). In spite of the clinical effectiveness of immune checkpoint inhibitors, the overall response rate still remains low. Therefore, there have been considerable efforts in searching for alternative immune checkpoint proteins that may work as new therapeutic targets for treatment of cancer. Recent studies have identified several additional novel immune checkpoint targets, including lymphocyte activation gene-3, T cell immunoglobulin and mucin-domain containing-3, T cell immunoglobulin and immunoreceptor tyrosine-based inhibition motif domain, V-domain Ig suppressor of T cell activation, B7 homolog 3 protein, B and T cell lymphocyte attenuator, and inducible T cell COStimulator. Natural compounds, especially those present in medicinal or dietary plants, have been investigated for their anti-tumor effects in various in vitro and in vivo models. Some phytochemicals exert anti-tumor activities based on immunoregulatioby blocking interaction between proteins involved in immune checkpoint signal transduction or regulating their expression/activity. Recently, synergistic anti-cancer effects of diverse phytochemicals with anti-PD-1/PD-L1 or anti-CTLA-4 monoclonal antibody drugs have been continuously reported. Considering an increasing attention to noteworthy therapeutic effects of immune checkpoint inhibitors in the cancer therapy, this review focuses on regulatory effects of selected phytochemicals on immune checkpoint protein network and their combinational effectiveness with immune checkpoint inhibitors targeting tumor cells.

LIGHT (TNFSF14) Costimulation Enhances Myeloid Cell Activation and Antitumor Immunity in the Setting of PD-1/PD-L1 and TIGIT Checkpoint Blockade

Coinhibition of TIGIT (T cell immunoreceptor with Ig and ITIM domains) and PD-1/PD-L1 (PD-1/L1) may improve response rates compared with monotherapy PD-1/L1 blockade in checkpoint naive non-small cell lung cancer with PD-L1 expression >50%. TIGIT mAbs with an effector-competent Fc can induce myeloid cell activation, and some have demonstrated effector T cell depletion, which carries a clinical liability of unknown significance. TIGIT Ab blockade translates to antitumor activity by enabling PVR signaling through CD226 (DNAM-1), which can be directly inhibited by PD-1. Furthermore, DNAM-1 is downregulated on tumor-infiltrating lymphocytes (TILs) in advanced and checkpoint inhibition-resistant cancers. Therefore, broadening clinical responses from TIGIT blockade into PD-L1low or checkpoint inhibition-resistant tumors, may be induced by immune costimulation that operates independently from PD-1/L1 inhibition. TNFSF14 (LIGHT) was identified through genomic screens, in vitro functional analysis, and immune profiling of TILs as a TNF ligand that could provide broad immune activation. Accordingly, murine and human bifunctional fusion proteins were engineered linking the extracellular domain of TIGIT to the extracellular domain of LIGHT, yielding TIGIT-Fc-LIGHT. TIGIT competitively inhibited binding to all PVR ligands. LIGHT directly activated myeloid cells through interactions with LTβR (lymphotoxin β receptor), without the requirement for a competent Fc domain to engage Fcγ receptors. LIGHT costimulated CD8+ T and NK cells through HVEM (herpes virus entry mediator A). Importantly, HVEM was more widely expressed than DNAM-1 on T memory stem cells and TILs across a range of tumor types. Taken together, the mechanisms of TIGIT-Fc-LIGHT promoted strong antitumor activity in preclinical tumor models of primary and acquired resistance to PD-1 blockade, suggesting that immune costimulation mediated by LIGHT may broaden the clinical utility of TIGIT blockade.

Update in TIGIT Immune-Checkpoint Role in Cancer

The in-depth characterization of cross-talk between tumor cells and T cells in solid and hematological malignancies will have to be considered to develop new therapeutical strategies concerning the reactivation and maintenance of patient-specific antitumor responses within the patient tumor microenvironment. Activation of immune cells depends on a delicate balance between activating and inhibitory signals mediated by different receptors. T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT) is an inhibitory receptor expressed by regulatory T cells (Tregs), activated T cells, and natural killer (NK) cells. TIGIT pathway regulates T cell-mediated tumor recognition in vivo and in vitro and represents an exciting target for checkpoint blockade immunotherapy. TIGIT blockade as monotherapy or in combination with other inhibitor receptors or drugs is emerging in clinical trials in patients with cancer. The purpose of this review is to update the role of TIGIT in cancer progression, looking at TIGIT pathways that are often upregulated in immune cells and at possible therapeutic strategies to avoid tumor aggressiveness, drug resistance, and treatment side effects. However, in the first part, we overviewed the role of immune checkpoints in immunoediting, the TIGIT structure and ligands, and summarized the key immune cells that express TIGIT.