Fibronectin EDB domain: A key molecule of tumor-specific splice variants and targeted theranostics

Author: Senior Product Manager of UA Views：6

This article focuses on the molecular characteristics and splicing regulatory mechanisms of the fibronectin EDA and EDB domains, systematically elaborating the structural differences and functional differentiation of the three forms of fibronectin—plasma fibronectin, cellular fibronectin, and fetal fibronectin—analyzing the molecular basis for the overexpression of the EDA and EDB domains in embryonic tissues, placental tissues, and malignant cells, and exploring the clinical value of EDA/EDB as tumor-specific markers and targeted therapeutic targets.

Recent Advances
Product Information

Recent Advances

Fibronectin EDB Domain: A Tumor-Specific Splice Variant and a Key Molecule for Targeted Theranostics

Summary: This article focuses on the molecular characteristics and splicing regulatory mechanisms of the fibronectin EDA and EDB domains, systematically elaborating the structural differences and functional differentiation of the three forms of fibronectin—plasma fibronectin, cellular fibronectin, and fetal fibronectin—analyzing the molecular basis for the overexpression of the EDA and EDB domains in embryonic tissues, placental tissues, and malignant cells, and discussing the clinical value of EDA/EDB as tumor-specific markers and targeted therapeutic targets.

I. The Three Forms of Fibronectin and Its Structural Diversity.

Fibronectin exists primarily in three forms. The first is synthesized by hepatocytes or endothelial cells and exists as a soluble dimer in plasma and body fluids, known as plasma fibronectin. The second is synthesized by different types of cells, including fibroblasts, astrocytes, and early mesenchymal cells, and is deposited as dimers or multimers on cell surfaces, in the extracellular matrix, in intercellular spaces, in basement membranes, and in connective tissues, known as cellular fibronectin. The first two types of fibronectin are similar in molecule, structure, and function and can interconvert. The third is mainly synthesized by embryonic tissues, placental tissues, and malignant cells, known as fetal fibronectin, and is produced by overexpression of the gene sequences EDA and EDB. The differences among these three forms in tissue distribution and expression regulation constitute the structural basis for the functional diversity of fibronectin.

At least 20 fibronectin polypeptides have been identified to date. The different subunits of fibronectin are products of the expression of the same gene, differing only in post-transcriptional RNA splicing, thereby producing different mRNAs. Each subunit of fibronectin is composed of several structural domains with high-affinity binding sites for cell surface receptors, collagen, fibrin, and sulfated proteoglycans. This “one gene, multiple products” splicing regulatory pattern enables fibronectin to produce functionally specialized variants under different tissue and physiological conditions.

II. Splicing Regulation and Expression Characteristics of the EDA and EDB Domains.

EDA and EDB are two type III repeat domains in the fibronectin gene that are regulated by alternative splicing. In normal adult tissues, the EDA and EDB domains are usually spliced out of fibronectin mRNA, so normal mature fibronectin contains almost none of these two domains. However, in embryonic tissues, placental tissues, and malignant cells, the splicing patterns of EDA and EDB are altered, leading to overexpression of fibronectin variants containing these two domains. This expression characteristic is highly tumor- and embryo-specific—the low expression of EDA and EDB in normal adult tissues contrasts sharply with their high expression in tumor tissues, making them ideal molecular targets for tumor-targeted theranostics. Of particular note is that the expression of the EDB domain shows high consistency across various solid tumors, while it is almost undetectable in normal tissues; this expression difference provides a potential safety window for targeted therapy.

III. Biological Functions and Clinical Significance of Fibronectin.

The functions of fibronectin are highly complex. It is currently known that fibronectin is involved in cell adhesion, cell migration, and chemotaxis, and thus plays a role in combating inflammation, tissue repair, and wound healing. Fibronectin strongly promotes the phagocytic function of mononuclear macrophages and possesses nonspecific opsonin activity, which is of great significance in anti-infection, clearance of immune complexes, and promotion of tumor gene transformation. Fibronectin is present in the α granules of platelets; thrombin and collagen can cause platelets to release fibronectin and secrete it onto the platelet surface. During clot formation, fibronectin promotes platelet attachment to damaged vascular sites. In the final stage of coagulation, coagulation factor XIIIa can catalyze the covalent binding of fibronectin to fibrin. When vascular endothelium is damaged and collagen is exposed, fibronectin can regulate the relationship between fibrin and collagen, accelerate the clearance of fibrin and its degradation products, maintain the dynamic balance of coagulation and fibrinolysis, and exert antithrombotic effects.

Because fibronectin has very complex biological functions, changes in its levels are closely related to the severity and prognosis of various clinical diseases. In hepatitis and cirrhosis, serum fibronectin levels decrease during the active phase, and a rebound in serum fibronectin levels indicates improvement. In coronary heart disease, serum fibronectin levels increase; the high-fibronectin state, on the one hand, promotes wound repair of necrotic myocardium, and on the other hand, promotes platelet adhesion to damaged vascular sites, exerting antithrombotic effects. In malignant tumors, serum fibronectin levels in patients with gastrointestinal tumors are lower than those in normal controls, while fibronectin levels in malignant effusions are higher than in other infectious and nonspecific effusions; therefore, it is of great value for detecting early tumor invasion, guiding treatment, and predicting prognosis. In hematological diseases, plasma fibronectin in patients with acute leukemia and septicemia is significantly lower than normal values, and its levels gradually recover as the condition improves. In type II diabetes, plasma fibronectin is significantly reduced, and after treatment with hypoglycemic drugs, plasma fibronectin significantly increases and is negatively correlated with fasting blood glucose levels. In preterm birth screening, amniotic fluid and cervicovaginal secretions in normal mid-to-late pregnancy contain only a small amount of fetal fibronectin; when preterm labor contractions occur, the chorion-decidua interface ruptures, and fetal fibronectin leaks into the amniotic fluid and cervix; therefore, detecting fetal fibronectin levels provides a monitoring method for the prevention and treatment of preterm birth. In pregnancy-induced hypertension syndrome, plasma fibronectin levels in patients are significantly higher than normal values and increase with worsening of the condition and increasing gestational weeks. In rheumatoid arthritis, the need for repair after tissue injury may promote accelerated biosynthesis of cellular fibronectin, part of which enters the blood, leading to secondary elevation of plasma fibronectin; its concentration changes may serve as an indicator for efficacy observation and prognosis assessment.

IV. The Value of EDA/EDB as Targets for Tumor-Targeted Theranostics.

The specific overexpression of the EDA and EDB domains in tumor tissues makes them highly attractive molecular targets in the field of tumor-targeted theranostics. At the diagnostic level, antibodies or probes directed against the EDB domain can be used for specific imaging of tumors, distinguishing tumor tissue from normal tissue. At the therapeutic level, EDB-targeting antibody-drug conjugates, immunotoxins, and CAR-T cell therapies can exploit the high expression of EDB in the tumor extracellular matrix to achieve precise drug delivery. Because EDB is expressed in the tumor-associated extracellular matrix rather than in tumor cells themselves, EDB-targeting strategies can not only act on tumor cells but also indirectly inhibit tumor growth by disrupting the stromal support of the tumor microenvironment; this mechanism is particularly important for highly heterogeneous solid tumors.

V. Conclusion.

In basic research related to fibronectin EDB and the development of tumor-targeted theranostics, high-quality recombinant EDB protein is a core tool for elucidating its binding mechanisms with targeting antibodies and probes. The His tag facilitates purification by immobilized metal affinity chromatography and enables detection and capture by anti-His tag antibodies. To meet the needs of EDB functional research and tumor-targeting strategy exploration, Univ provides Fibronectin type III EDB His Tag protein, Human. This product is suitable for applications such as binding activity analysis of EDB with targeting antibodies, in vitro screening and evaluation of EDB-specific probes and antibody-drug conjugates, research on the expression and function of EDB in the tumor microenvironment, and development of EDB-based tumor-targeted theranostic strategies.

This article is reviewed and published by the technical expert team of UA

Disclaimer: This article partially utilizes artificial intelligence assistance in its creation. If any content involves copyright or intellectual property issues, please let us know and we promise to verify and remove it as soon as possible.

Purchase recombinant protein, choose

UA protein focuses on providing various protein reagents, raw materials, and services required for drug research and development, cell therapy, gene therapy, and basic scientific research, including drug target proteins, immune checkpoint proteins, cytokines, tool enzymes, customized protein expression, and full-length transmembrane protein development. Nanjing Univ is committed to providing customers with high-quality products and professional services, and building a High-tech Biological Enterprise with International Competitiveness.

Buy antibodiesFind UA www.ua-bio.com | 15 years of protein development experience

Nanjing UNIV Biotechnology Co., Ltd. Email：order@ua-bio.com Phone：+86-25-56221161

more products

Product Information

The Last The Next