TNFSF4

Detailed Information

TNFSF4, also known as OX40 ligand (OX40L), is an important immune regulatory molecule located on human chromosome 1q25 and belongs to the tumor necrosis factor (TNF) superfamily. The gene encodes a type II transmembrane glycoprotein, with multiple transcript variants generated through alternative splicing, producing either soluble or membrane-bound biologically active forms. TNFSF4 primarily binds to TNFRSF4 (OX40), forming a key ligand–receptor axis in co-stimulatory immune signaling. Structurally, TNFSF4 exists as a trimer, and its extracellular domain mediates receptor binding, initiating downstream signaling cascades.

Figure 1. The co-stimulatory T-cell receptor OX40 is expressed predominantly on effector and regulatory T-cells. (Lé AM, et al., 2022)

Gene expression analyses show TNFSF4 is predominantly expressed in antigen-presenting cells (APCs), including dendritic cells, B cells, and macrophages, as well as vascular endothelial cells. Activated T lymphocytes also exhibit significant expression. This tissue-specific pattern indicates TNFSF4's critical role in adaptive immunity, particularly in interactions between T cells and APCs. Evolutionarily, TNFSF4 is highly conserved among mammals, highlighting its functional importance. Its expression is regulated by transcription factors such as NF-κB, AP-1, and NFAT, which are induced upon immune activation. Epigenetic modifications, including DNA methylation and histone marks, influence TNFSF4 expression and may contribute to dysregulation in autoimmune diseases. Several single-nucleotide polymorphisms (SNPs) in the TNFSF4 locus have been linked to susceptibility to autoimmune diseases such as systemic lupus erythematosus (SLE) and Sjögren's syndrome.

Molecular Function and Immune Regulation

As a co-stimulatory molecule, TNFSF4 plays a precise regulatory role in T cell-mediated immunity. The binding of TNFSF4 on APCs to TNFRSF4 on T cells activates co-stimulatory signaling essential for full T cell activation and clonal expansion. This interaction recruits adaptor proteins including TRAF2, TRAF3, and TRAF5, activating PI3K/AKT, NF-κB, and MAPK pathways, thereby promoting T cell proliferation, survival, and effector function. Co-stimulation is especially critical for CD4+ helper T cells, enhancing IL-2 production and suppressing activation-induced cell death. Upregulation of TNFSF4 at the immunological synapse stabilizes adhesion between T cells and APCs, prolonging interactions and strengthening immune responses.

TNFSF4 also modulates regulatory T cells (Tregs) in a context-dependent manner. High TNFSF4 expression in the tumor microenvironment is associated with enhanced Treg immunosuppressive function, whereas blockade of the TNFSF4-TNFRSF4 axis diminishes Treg-mediated suppression and enhances effector T cell cytotoxicity. In mesenchymal stem cell (MSC) therapy studies, TNFSF4-low MSCs (TNFSF4^low-MSCs) exhibit stronger induction of Tregs and therapeutic effects in models of idiopathic pulmonary fibrosis (IPF), increasing the proportion of activated, central memory, and effector Tregs.

TNFSF4 also plays a key role in endothelial function. During inflammation, it mediates adhesion between activated T cells and endothelial cells, promoting lymphocyte migration to sites of inflammation, which is important in atherosclerosis and autoimmune diseases. In tumor vasculature, TNFSF4 upregulation may enhance angiogenesis, providing a favorable microenvironment for tumor growth. TNFSF4 signaling intersects with other immune checkpoint pathways, including CTLA-4 and PD-1, suggesting potential for combinatorial immunotherapies.

Disease Associations and Mechanisms

TNFSF4 has been implicated in autoimmune diseases, cardiovascular disorders, and cancer. Genome-wide association studies (GWAS) link TNFSF4 polymorphisms to SLE, rheumatoid arthritis, and Sjögren's syndrome. These variants, mainly in regulatory regions, may alter transcription factor binding and chromatin accessibility, modulating TNFSF4 expression. In SLE, TNFSF4 mRNA is elevated in peripheral blood mononuclear cells and correlates with disease activity. Soluble TNFSF4 may serve as a biomarker for disease monitoring. Mechanistically, overexpression can lead to aberrant survival of autoreactive T cells, breaking immune tolerance and promoting autoantibody production.

In cardiovascular disease, TNFSF4 contributes to vascular inflammation, mediating monocyte adhesion, foam cell formation, and plaque progression. In cancer, TNFSF4 displays context-dependent roles. In hepatocellular carcinoma (HCC), higher expression in adjacent normal tissue correlates with improved prognosis, and TNFSF4 knockout reduces JAK-STAT3 activity, increases p53 and cleaved caspase-3, and decreases MDM2 and TGFβ1/2, suppressing proliferation and invasion while enhancing sorafenib sensitivity. In lung cancer, low TNFRSF4 expression correlates with poor prognosis, reduced CD4+ T cells, elevated CD4+/CD8+ ratios, and increased pro-inflammatory cytokines, indicating immune dysregulation.

In fibrosis, particularly IPF, TNFSF4 signaling regulates Treg-mediated modulation of fibroproliferative processes. TNFSF4^low-MSCs enhance Treg differentiation, reduce profibrotic factors (TGF-β, CTGF), and increase antifibrotic cytokines (HGF, IL-10), mitigating lung collagen deposition and demonstrating extended tissue retention and increased Treg induction compared to conventional MSCs. In neurological diseases, TNFSF4 polymorphisms are associated with multiple sclerosis susceptibility and progression, potentially influencing blood-brain barrier integrity and CNS inflammation.

Therapeutic Applications and Translational Potential

The TNFSF4-TNFRSF4 axis is a promising therapeutic target in cancer immunotherapy, autoimmune diseases, and antifibrotic therapy. Agonist antibodies targeting TNFRSF4 (e.g., MEDI6469) enhance effector T cell expansion and tumor infiltration, showing safety and efficacy alone or with PD-1 inhibitors. Conversely, TNFSF4-blocking antibodies (e.g., KY1005) inhibit Treg function and restore effector T cell activity. Preclinical combination therapies with PD-1 blockade achieve superior tumor growth inhibition.

In autoimmune disease models, anti-TNFSF4 antibodies reduce autoantibody titers, ameliorate renal pathology in SLE, and improve survival by dampening hyperactive T-B cell interactions. Clinical trials (KY1005, RG7888) demonstrate promising response rates with manageable safety profiles. In cardiovascular disease, anti-TNFSF4 treatment reduces aortic plaque size and increases plaque stability.

In fibrosis, TNFSF4^{low-MSCs offer enhanced therapeutic benefits, improving Treg-mediated antifibrotic effects, decreasing profibrotic factor expression, and prolonging MSC retention in lung tissue. First-in-human trials evaluating TNFSF4}low-MSCs in IPF are in preparation. Gene therapy and RNA-targeting approaches (CRISPR-Cas9, ASO, siRNA) are under investigation, enabling long-term modulation of TNFSF4 expression for autoimmune and inflammatory conditions. Advances in delivery systems and gene editing may realize TNFSF4-targeted therapies as a clinical reality within the next decade.