Expression of ILT3 predicts poor prognosis and is inversely associated with infiltration of CD45RO+ T cells in patients with colorectal cancer

LILRB4 in acute myeloid leukemia: From prognostic biomarker to immunotherapeutic target

ABSTRACT

Leukocyte immunoglobulin-like receptor (LILR) B4 (also known as ILT3/CD85k) is an immune checkpoint protein that is highly expressed in solid tumors and hematological malignancies and plays a significant role in the pathophysiology of cancer. LILRB4 is highly expressed in acute myeloid leukemia (AML), and this phenotype is associated with adverse patient outcomes. Its differential expression in tumors compared to normal tissues, its presence in tumor stem cells, and its multifaceted roles in tumorigenesis position it as a promising therapeutic target in AML. Currently, several immunotherapies targeting LILRB4 are undergoing clinical trials. This review summarizes advancements made in the study of LILRB4 in AML, focusing on its structure, ligands, expression, and significance in normal tissues and AML; its protumorigenic effects and mechanisms in AML; and the application of LILRB4-targeted therapies in AML. These insights highlight the potential advantages of LILRB4 as an immunotherapeutic target in the context of AML.

Human leukocyte immunoglobulin-like receptors in health and disease

Human leukocyte immunoglobulin (Ig)-like receptors (LILR) are a family of 11 innate immunomodulatory receptors, primarily expressed on lymphoid and myeloid cells. LILRs are either activating (LILRA) or inhibitory (LILRB) depending on their associated signalling domains (D). With the exception of the soluble LILRA3, LILRAs mediate immune activation, while LILRB1-5 primarily inhibit immune responses and mediate tolerance. Abnormal expression and function of LILRs is associated with a range of pathologies, including immune insufficiency (infection and malignancy) and overt immune responses (autoimmunity and alloresponses), suggesting LILRs may be excellent candidates for targeted immunotherapies. This review will discuss the biology and clinical relevance of this extensive family of immune receptors and will summarise the recent developments in targeting LILRs in disease settings, such as cancer, with an update on the clinical trials investigating the therapeutic targeting of these receptors.

Targeted splicing therapy: new strategies for colorectal cancer

RNA splicing is the process of forming mature mRNA, which is an essential phase necessary for gene expression and controls many aspects of cell proliferation, survival, and differentiation. Abnormal gene-splicing events are closely related to the development of tumors, and the generation of oncogenic isoform in splicing can promote tumor progression. As a main process of tumor-specific splicing variants, alternative splicing (AS) can promote tumor progression by increasing the production of oncogenic splicing isoforms and/or reducing the production of normal splicing isoforms. This is the focus of current research on the regulation of aberrant tumor splicing. So far, AS has been found to be associated with various aspects of tumor biology, including cell proliferation and invasion, resistance to apoptosis, and sensitivity to different chemotherapeutic drugs. This article will review the abnormal splicing events in colorectal cancer (CRC), especially the tumor-associated splicing variants arising from AS, aiming to offer an insight into CRC-targeted splicing therapy.

Comprehensive analysis of LILR family genes expression and tumour-infiltrating immune cells in early-stage pancreatic ductal adenocarcinoma

Leucocyte immunoglobulin-like receptors (LILRs) are closely related to tumourigenesis, but their clinical value in early-stage pancreatic ductal adenocarcinoma (PDAC) after pancreaticoduodenectomy remains unknown. Kaplan-Meier and Cox proportional hazards regression models is used to investigate the association between LILR expression and prognosis in tumour biopsies and peripheral blood mononuclear cells. Risk score was calculated for each patient based on the prognostic model. DAVID, STRING, GeneMANIA, and GSEA were used to conduct pathway and functional analyses. The CIBERSORT algorithm is used to analyse tumour-infiltrating immune cells. Survival analysis showed that high levels of LILRA4 (p = 0.006) and LILRB4 (p = 0.04) were significantly associated with better overall survival. High levels of LILRA2 (p = 0.008) and LILRB4 (p = 0.038) were significantly associated with better relapse-free survival. JAK-STAT signalling pathway, regulation of T cell activation, regulation of the immune effector process, and tumour necrosis factor superfamily cytokine production were involved in molecular mechanisms that affected poor prognoses in the high-risk group in GSEA. CIBERSORT demonstrated that the high-risk group had significantly higher infiltrating fraction of memory-activated CD4 T cells and activated NK cells and lower fraction of resting dendritic cells and neutrophils. LILRB4 plays crucial roles in affecting the clinical outcomes of early-stage PDAC.

LILRB4, an immune checkpoint on myeloid cells

Leukocyte immunoglobulin-like receptor B4 (LILRB4) is an inhibitory receptor in the LILR family mainly expressed on normal and malignant human cells of myeloid origin. By binding to ligands, LILRB4 is activated and subsequently recruits adaptors to cytoplasmic immunoreceptor tyrosine inhibitory motifs to initiate different signaling cascades, thus playing an important role in physiological and pathological conditions, including autoimmune diseases, microbial infections, and cancers. In normal myeloid cells, LILRB4 regulates intrinsic cell activation and differentiation. In disease-associated or malignant myeloid cells, LILRB4 is significantly correlated with disease severity or patient survival and suppresses T cells, thereby participating in the pathogenesis of various diseases. In summary, LILRB4 functions as an immune checkpoint on myeloid cells and may be a promising therapeutic target for various human immune diseases, especially for cancer immunotherapy.

The Fibronectin-ILT3 Interaction Functions as a Stromal Checkpoint that Suppresses Myeloid Cells

Suppressive myeloid cells inhibit antitumor immunity by preventing T-cell responses. Immunoglobulin-like transcript 3 (ILT3; also known as LILRB4) is highly expressed on tumor-associated myeloid cells and promotes their suppressive phenotype. However, the ligand that engages ILT3 within the tumor microenvironment and renders tumor-associated myeloid cells suppressive is unknown. Using a screening approach, we identified fibronectin as a functional ligand for ILT3. The interaction of fibronectin with ILT3 polarized myeloid cells toward a suppressive state, and these effects were reversed with an ILT3-specific antibody that blocked the interaction of ILT3 with fibronectin. Furthermore, ex vivo treatment of human tumor explants with anti-ILT3 reprogrammed tumor-associated myeloid cells toward a stimulatory phenotype. Thus, the ILT3-fibronectin interaction represents a "stromal checkpoint" through which the extracellular matrix actively suppresses myeloid cells. By blocking this interaction, tumor-associated myeloid cells may acquire a stimulatory phenotype, potentially resulting in increased antitumor T-cell responses.

Not Only Immune Escape-The Confusing Role of the TRP Metabolic Pathway in Carcinogenesis

BACKGROUND

The recently discovered phenomenon that cancer cells can avoid immune response has gained scientists' interest. One of the pathways involved in this process is tryptophan (TRP) metabolism through the kynurenine pathway (KP). Individual components involved in TRP conversion seem to contribute to cancerogenesis both through a direct impact on cancer cells and the modulation of immune cell functionality. Due to this fact, this pathway may serve as a target for immunotherapy and attempts are being made to create novel compounds effective in cancer treatment. However, the results obtained from clinical trials are not satisfactory, which raises questions about the exact role of KP elements in tumorigenesis. An increasing number of experiments reveal that TRP metabolites may either be tumor promoters and suppressors and this is why further research in this field is highly needed. The aim of this study is to present KP as a modulator of cancer development through multiple mechanisms and to point to its ambiguity, which may be a reason for failures in treatment based on the inhibition of tryptophan metabolism.

Leukocyte immunoglobulin-like receptor subfamily B: therapeutic targets in cancer

Inhibitory leukocyte immunoglobulin-like receptors (LILRBs 1–5) transduce signals via intracellular immunoreceptor tyrosine-based inhibitory motifs that recruit phosphatases to negatively regulate immune activation. The activation of LILRB signaling in immune cells may contribute to immune evasion. In addition, the expression and signaling of LILRBs in cancer cells especially in certain hematologic malignant cells directly support cancer development. Certain LILRBs thus have dual roles in cancer biology—as immune checkpoint molecules and tumor-supporting factors. Here, we review the expression, ligands, signaling, and functions of LILRBs, as well as therapeutic development targeting them. LILRBs may represent attractive targets for cancer treatment, and antagonizing LILRB signaling may prove to be effective anti-cancer strategies.

ILT3 promotes tumor cell motility and angiogenesis in non-small cell lung cancer

Immunoglobulin-like transcript (ILT) 3 is an immunosuppressive molecule that negatively regulates myeloid cell activation. ILT3 overexpression in tumor cells induces immune escape of solid tumors and facilitates invasion of monocytic acute myeloid leukemia cells. However, the expression and function of ILT3 in non-small cell lung cancer (NSCLC) cells remain elusive. Herein, we found that ILT3 was enriched in human NSCLC cells, and predicted advanced disease and poor overall survival. ILT3 overexpression enhanced the migration and invasion of NSCLC cells and tubule formation of human umbilical vein endothelial cells by upregulating and interacting with its ligand apolipoprotein E (ApoE) in vitro. Mechanistically, ILT3 recruited SHP2 and SHIP1, and subsequently activated ERK1/2 signaling mediating epithelial-mesenchymal transition (EMT) and increasing vascular endothelial growth factor (VEGF)-A expression in NSCLC cells, which are responsible for tumor cell motility and angiogenesis, respectively. Using murine metastasis models, we further confirmed ILT3 promoted NSCLC metastasis and explored the exact correlation of ILT3 with ApoE, EMT, and VEGF-A in vivo. These results unraveled novel mechanisms for ILT3-induced tumor progression and proposed ILT3 as a potential therapeutic target and prognostic biomarker for NSCLC patients.