Generation of novel diagnostic and therapeutic exosomes to detect and deplete protumorigenic M2 macrophages

Given their protumorigenic function and prevalence in most malignant tumors with lower survival; early detection, and intervention of CD206‐positive M2 macrophages may boost the clinical outcome. To determine in vivo distribution of M2 macrophages, researchers from Augusta University adopted 111In‐oxine‐based radiolabeling of the targeted exosomes. When these radiolabeled targeted exosomes are injected into breast tumor‐bearing mice, exosomes accumulate at the periphery of the primary tumor, metastatic foci in the lungs, spleen, and liver. Ex vivo quantification of radioactivity also shows similar distribution. Injecting DiI dye‐labeled exosomes into the same mice shows adherence of exosomes to the CD206‐positive M2 macrophages on ex vivo fluorescent microscopy imaging. In addition, these engineered exosomes are utilized to carry the Fc portion of IgG2b with the intention of augmenting antibody‐dependent cell‐mediated cytotoxicity. It is demonstrated that M2 macrophage targeting therapeutic exosomes deplete M2 macrophages both in vitro and in vivo, and reduce tumor burden, increasing survival in a metastatic breast cancer model.

Generation of CD206‐positive M2 macrophage‐targeting therapeutic exosomes
to induce antibody‐dependent cell‐mediated cytotoxicity

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a) Schematic diagram showing the proposed mechanism of engineered exosome‐based antibody‐dependent cellular cytotoxicity. b) Schematic representation of the plasmid construct containing modified Lamp2b protein with CD206‐targeting sequence conjugated with Fc segment of mouse IgG2b. c) Confirmation of luciferase activity by transfected HEK293 cells. d) Flow‐cytometric analysis for validating the expression of Fc segment of mouse IgG2b on the surface of engineered exosomes. Three different engineered exosome samples were used for the flowcytometry. e,f) NTA analysis data showing size distribution of the engineered therapeutic exosomes. g) Transmission electron microscopy image for engineered therapeutic exosomes, Scale bar depicts 100 nm. h) Flow‐cytometric analysis of exosomal markers CD9 and CD63 for the engineered therapeutic exosomes. Three different engineered exosome samples were used for the flowcytometry.

Rashid MH, Borin TF, Ara R, Alptekin A, Liu Y, Arbab AS. (2020) Generation of Novel Diagnostic and Therapeutic Exosomes to Detect and Deplete Protumorigenic M2 Macrophages. Adv Ther (Weinh) 3(7):1900209. [article]

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