Enhanced targeting with heterobivalent ligands.

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Targeting tumor cells for detection and treatment requires specific molecular strategies.
• Heteromultivalent ligands offer a novel approach by crosslinking multiple cell surface receptors.
• Previous studies showed enhanced binding with homomultivalent ligands, but cross-linking needed validation with distinct binding moieties.

Purpose of the Study:

• To demonstrate the proof-of-concept for synthetic heterobivalent ligands in crosslinking distinct cell surface receptors.
• To investigate the binding affinity of heterobivalent ligands to engineered cell lines coexpressing specific G-protein-coupled receptors.
• To establish a foundation for developing multivalent ligands targeting cancer-specific receptor combinations.

Main Methods:

• Engineered cell lines coexpressing human melanocortin 4 receptor (MC4R) with either human delta-opioid receptor (deltaOR) or human cholecystokinin-2 receptor (CCK2R).
• Quantified receptor expression levels using time-resolved fluorescence saturation binding assays with Europium-labeled ligands.
• Synthesized heterobivalent ligands linking MC4R agonists to either deltaOR or CCK2R agonists via chemical linkers.

Main Results:

• Heterobivalent ligands exhibited significantly higher binding affinity to cells coexpressing both target receptors compared to single-receptor cells.
• Competitive blocking assays confirmed the specific crosslinking of distinct receptors by heterobivalent ligands.
• Demonstrated successful noncovalent crosslinking of two unrelated cell surface receptors using synthetic heterobivalent ligands.

Conclusions:

• Synthetic heterobivalent ligands can effectively noncovalently crosslink distinct cell surface receptors.
• This capability enables the targeted approach for combinations of cell surface receptors.
• The developed in vitro models pave the way for multivalent ligand development against identified human cancer targets.