Phage-Display-Derived Peptide Binds to Human CD206 and Modeling Reveals a New Binding Site on the Receptor

Abstract

We recently identified a tumor homing peptide (mUNO: "CSPGAK") that specifically interacts with mouse CD206 (mCD206) to target CD206/MRC1-expressing tumor-associated macrophages in mice. Here, we report studies on the binding of mUNO to human recombinant CD206 (hCD206) and on modeling the mUNO/hCD206 interaction by computational analysis. Fluorescence anisotropy analysis demonstrated that fluorophore-labeled mUNO interacts with hCD206. Microsecond timescale molecular dynamic simulations and docking predictions showed that mUNO binds to a newly identified epitope between C-type lectin domains 1 and 2. The physical mechanisms that contribute to the docking interactions of mUNO include electrostatic interactions, aromatic interactions, and hydrogen bonds. We also demonstrate selectivity of FAM-mUNO for CD206 + cultured human macrophages. The peptide mUNO appears to be the first ligand capable of interacting with this epitope of hCD206, to which no ligands have been reported. Our study has implications for targeting human M2-like tumor-associated macrophages, a subpopulation of immune cells with major protumoral role.

Pro-Tumorigenic Macrophage Infiltration in Oral Squamous Cell Carcinoma and Possible Macrophage-Aimed Therapeutic Interventions

“…We identified and published a CD206-targeting peptide, called “mUNO”, that binds to mouse and human CD206 ( 83 ), is selective to mouse and human CD206+ macrophages ( 84 ), and delivers payload specifically to M2-like TAMs in mouse models of melanoma, glioblastoma, gastric carcinoma, and breast cancer ( 83 ) with very low accumulation in healthy organs ( 83 , 85 ). We showed that mUNO binds to a different binding site than mannose on CD206 ( 84 ), making it more specific to CD206 than mannose-based ligands. Additionally, mUNO only targets CD206 in the tumor and not in the liver; a moderate affinity of mUNO for CD206, and a higher dwelling time in tumor than in liver (due to leaky tumor vasculature) may explain this phenomenon ( 85 ).…”

Conventional Nanosized Drug Delivery Systems for Cancer Applications

“…They are basically amphipathic molecules having microbial origin that reduce interfacial and surface tension at liquid-solid-gas-interfaces. Bansal and coworkers [16] demonstrated that GQDs NCs conjugated with folic acid (FA) and biosurfactants could be used as therapeutic and diagnostic agents in clinical cancer treatment. In the future, the use of GQD-bioconjugates may allow the detection and treatment of cancer at an early stage.…”

“…In the future, the use of GQD-bioconjugates may allow the detection and treatment of cancer at an early stage. This may increase the life span of cancer patients [16]. Furthermore, black phosphorus QDs are incorporated into liposomes to make DDS with excellent NIR photothermal properties and drug release properties controlled by light.…”

“…Recently we reported the identification of a peptide (mUNO, sequence: CSPGAK) that binds to mouse CD206 and homes to M2 TAMs in multiple solid tumor models, suggesting that peptide homing is dependent on the presence of M2 TAMs and not on the tumor type [16,175]. Systemically administered fluorescein-labeled mUNO homes exclusively to CD206 high M2 TAMs in metastatic breast cancer, with no accumulation in tumor-free liver [16,175]. Importantly, M2 TAMs internalize FAM-mUNO complexes, suggesting that the peptide can be used for intracellular payload delivery.…”

Depletion of CD206+ tumour macrophages by mUNO targeted nanoconjugate inhibits tumourigenesis and dissemination in triple negative breast cancer

“…To target the CD206 + TAMs, we took advantage of a CD206-binding peptide to precisely guide the delivery of a cytotoxic compound. The mUNO peptide (sequence: CSPGAK) targets a CD206 site that differs from the mannose-binding site and displays low accumulation in the liver [41][42][43][44] .…”