VEGF165 is the predominant isoform of vascular endothelial growth factor-A, hailed as the "master switch" of angiogenesis. Through its precise regulation of new blood vessel formation, it plays a central role in development, repair, and numerous disease processes. This article provides a comprehensive analysis of what VEGF165 is, its unique functions and mechanisms, and explores in detail its pivotal role in cancer, ocular diseases, cardiovascular and neurological disorders, while also reviewing revolutionary therapies targeting it.

1. What is VEGF165? Understanding the "Chief Engineer" of Blood Vessels

VEGF165 is the most important, abundant, and biologically active isoform in the vascular endothelial growth factor family. To comprehend its central role in physiology and pathology, we must first understand its fundamental characteristics.

Structural and Functional Properties of VEGF165

The "versatile" isoform: The VEGF-A gene generates multiple isoforms (e.g., VEGF121, VEGF165, VEGF189) through alternative splicing. VEGF165 stands out because it retains all critical functional domains:

Vascular endothelial growth factor receptor-binding domain: Enables binding to VEGFR1 and VEGFR2.

Heparin-binding domain: This structure allows VEGF165 to diffuse freely while also binding to extracellular matrix and cell-surface heparan sulfate proteoglycans, creating a localized signaling gradient that precisely guides endothelial cell migration.

Core Biological Functions

Potent angiogenesis: It is the strongest known mitogen for endothelial cells, directly stimulating new blood vessel formation.

Enhanced vascular permeability: It dramatically increases microvascular permeability, playing a key role in inflammation and tumor development, earning it the name "vascular permeability factor."

Promotes cell survival and migration: By activating anti-apoptotic pathways, it supports endothelial cell survival and guides their migration toward hypoxic or injured areas.

Mechanism Overview

VEGF165 primarily binds to its receptor VEGFR2, triggering receptor dimerization and autophosphorylation, which activates downstream MAPK, PI3K/Akt, and other signaling pathways. Like a "master key" initiating vascular construction, it sends instructions for cell proliferation, migration, and survival.

2. What Diseases Are Associated with VEGF165?

The regulation of VEGF165 expression is like a precise valve. Under normal physiological conditions, moderate expression maintains homeostasis; however, excessive expression can lead to a "flood," causing severe diseases.

1. Cancer

This is where VEGF165 is most "notorious," serving as the lifeline for tumor survival and metastasis.

Mechanism: Rapidly growing tumors create a hypoxic microenvironment, which induces tumor cells to secrete large amounts of VEGF165.

Consequences:

Tumor angiogenesis: VEGF165 stimulates the formation of numerous twisted, malformed, and dysfunctional new blood vessels, providing oxygen and nutrients to support malignant growth.

Promotes metastasis: These abnormal vessels facilitate cancer cell infiltration, while VEGF165 increases vascular permeability, opening pathways for distant metastasis.

Clinical significance: In most solid tumors (e.g., lung, colorectal, breast cancer), high VEGF165 expression is closely linked to poor prognosis, making it a primary therapeutic target.

2. Ocular Diseases

In the eye, uncontrolled blood vessel growth is a direct cause of vision loss.

Wet age-related macular degeneration (wAMD):

Mechanism: Beneath the retina, abnormal new blood vessels grow under VEGF165's influence. These fragile vessels leak, causing hemorrhage, exudation, and retinal detachment, leading to rapid and severe central vision loss.

Diabetic macular edema (DME):

Mechanism: Hyperglycemia and hypoxia elevate intraocular VEGF165 levels, increasing retinal vascular permeability and causing fluid leakage and macular edema, the primary cause of blurred vision and decline in diabetics.

Others: VEGF165 also drives vascular diseases like retinal vein occlusion.

3. Cardiovascular and Ischemic Diseases

Here, VEGF165 shows its "angelic" side, offering hope for regenerative medicine.

Mechanism: In myocardial infarction, limb ischemia, and similar conditions, blood supply is blocked, causing severe hypoxia.

Therapeutic potential: Introducing VEGF165 via gene therapy or protein delivery aims to promote collateral circulation—"therapeutic angiogenesis"—providing new blood supply to ischemic tissue and salvaging dying tissue.

4. Other Diseases

Rheumatoid arthritis: In inflamed synovial joints, VEGF165 promotes pannus formation, delivering "supplies" to inflammatory cells and exacerbating joint swelling.

Neurological disorders: In amyotrophic lateral sclerosis (ALS), impaired neuroprotective functions of VEGF165 may contribute to disease progression.

3. Clinical Prospects: Successes and Future of Targeting VEGF165

Inhibiting the VEGF165 pathway is one of modern medicine's most successful targeted therapies.

Anticancer drugs:

Bevacizumab: A recombinant humanized anti-VEGF monoclonal antibody that acts like a "sponge," binding and neutralizing all VEGF-A isoforms (including VEGF165). It is part of standard chemotherapy regimens for many cancers.

VEGFR tyrosine kinase inhibitors: Such as sunitinib and pazopanib, which block the pathway by inhibiting intracellular VEGF signal transduction.

Ophthalmic drugs:

Ranibizumab, aflibercept, bevacizumab: Administered via intravitreal injection, they directly target the retina, inhibiting neovascularization and reducing vascular leakage. These are first-line therapies for wAMD and DME, saving millions from vision loss.

Challenges and future directions:

Drug resistance: Long-term anti-VEGF therapy may lead to resistance.

Side effects: May include hypertension, proteinuria, etc.

Next-generation therapies: Research focuses on longer-lasting drugs, therapies targeting specific isoforms (e.g., VEGF165b, an inhibitory isoform), and combining anti-VEGF with other treatments (e.g., immunotherapy).

Conclusion

The VEGF165 protein, as the "core commander" of angiogenesis, perfectly illustrates the biological principle of "too much of a good thing." It is both the foundation of development and tissue repair and a powerful driver of serious diseases like cancer and blindness. By developing precision drugs targeting VEGF165, humanity has achieved milestone victories in the fight against these diseases. Moving forward, with deeper understanding and more precise regulation of VEGF signaling, we can better harness its regenerative potential while curbing its pathogenic effects, opening new therapeutic horizons for human health.

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