Tumor Targeting or Tumor Homing Peptides

Cancer is a complex tissue containing a multitude of stromal cells as well as extracellular matrix. Hence, targeting the microenvironment of a tumor or cancer cell may allow destroying the malignant tumor cells. Peptides derived from natural sources or synthetic screens exhibit high specificity, are flexible and have low antigenicity. Tumor targeting or homing peptides bind to specific sites in the vasculature allowing targeting of organs or pathological tissues. When conjugated to drugs or oligonucleotides, these peptides can increase the uptake of the conjugates by tumors with reduced accumulation at non-targeted sites.

Tumor homing or tumor targeting peptides are short chains of amino acids with usually fewer than 50 residues designed or naturally occurring to deliver molecules, nanoparticles, or drugs to specific targets in cells, tissues, or organs. These peptides are often used in research, diagnostics, and therapeutic applications because they enhance the precision of delivery, reducing the risk of 'off-target effects'-unintended interactions with non-diseased cells or tissues that can lead to side effects.

Key Characteristics of Targeting Peptides

Specificity: Targeting peptides bind selectively to receptors, proteins, or other molecular targets predominantly on specific cells or tissues. Examples include tumor-specific peptides that target cancer cells or peptides that bind to inflamed tissues.

Small Size: The compact structure of targeting peptides, which is a result of their short chain of amino acids, allows for efficient penetration into tissues and cells. This compactness enables them to navigate through biological barriers and reach their intended targets more effectively.

Customizable: Modifications of targeting peptides enhance their stability, binding affinity, or resistance to enzymatic degradation.

Types of Targeting Peptides

Tumor-Homing Peptides: Tumor-homing peptides target cancer cells by binding to markers like integrins, such as RGD peptides for αvβ3 integrins.

Cell-Penetrating Peptides (CPPs): CPPs facilitate cellular uptake of large or impermeable molecules, such as TAT peptide, derived from HIV.

Organ-Targeting Peptides: Organ-targeting peptides enable the delivery of therapeutic agents to specific organs, such as brain-targeting peptides that cross the blood-brain barrier.

Inflammation-Targeting Peptides: These peptides target inflamed or damaged tissues and are often used in autoimmune or wound-healing therapies.

Antimicrobial Peptides: Antimicrobial peptides bind to microbial membranes for targeted action against bacteria, fungi, or viruses.

Applications of Targeting Peptides

Drug Delivery: Targeting peptides attached to drugs or nanoparticles allow for precise delivery to diseased cells.

Imaging: Conjugation of targeting peptides to imaging agents for diagnostic purposes allow detection of tumors.

Therapeutics: Targeting peptides when used as therapeutic agents can block disease pathways.

Biosensing: Incorporation of targeting peptides in biosensors enable detection of specific biological markers.

Targeting peptides are a vital component of modern biomedicine. Their ability to improve efficacy and safety in various therapies, from drug delivery to imaging and therapeutics, is significant.

Targeting Peptides

Reference

Le Joncour V, Laakkonen P. Seek & Destroy, use of targeting peptides for cancer detection and drug delivery. Bioorg Med Chem. 2018 Jun 1;26(10):2797-2806. [Sciencedirect]

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