Abstract 1139: CD206 positive M2-macrophage targeting engineered exosomes as a potential diagnostic and therapeutic tool
Mohammad H. Rashid, Thaiz F. Borin, Roxan Ara, Kartik Angara, Achyut Bhagelu, Jingwen Cai, Yutao Liu and Ali S. Arbab
DOI: 10.1158/1538-7445.AM2019-1139 Published July 2019
Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA
Abstract
Tumor
initiation and evolution is driven by the reciprocal actions between
stromal and immune cells within the tumor microenvironment (TME).
Tumor-associated macrophages (TAMs) specifically M2-macrophages, a
critical component of TME; participate in immune suppression, epithelial
to mesenchymal transition, invasion, angiogenesis, tumor progression
and subsequent metastasis foci formation. Given their prevalence in most
of the human tumor tissue and correlation of their higher infiltration
with lower survival, M2-macrophages represent promising targets for
diagnosis, prognosis and anticancer therapy. Hence, early in vivo
detection and intervention of M2-macrophages in the TME may boost the
clinical outcome. Exosomes are biological nanoparticles sizing 30-150
nm, recently drawing huge attention for their potential application as
therapeutic and diagnostic tool because they are more biocompatible and
biodegradable with lesser toxicity than other synthetic nanoparticles
and can easily percolate through the body’s barrier systems or through
abnormally formed blood vessels in tumor tissue. We have generated
engineered exosomes from HEK293 cells by lentiviral transfection system
that carry specific peptide sequence on their external surface for
targeting CD206 positive M2-macrophages. To determine the in vivo
distribution of M2-macrophages, we adopted 111In-oxine based
radio-labeling of the targeted exosomes and single-photon emission
computed tomography (SPECT). Up to the time, among the used techniques,
nuclear imaging is the foremost method to trace exosomes in vivo for
better tissue penetration, sensitivity and quantitative analysis. After
the labeling with 111In-oxine, we analyzed the binding
efficacy and serum stability of the targeted exosome by thin layer paper
chromatography (TLPC) using 100% methanol and 2M Sodium acetate
solution (1:1) as eluent. More than 98% of 111In-oxine was bound to exosomes and only 5% of free 111In-oxine
was dissociated from the exosomes even 24 hours after the incubation
with 20% serum. When we injected these radio-labeled targeted exosomes
in to 4T1 breast tumor-bearing mice, they went mostly to the periphery
of the primary tumor, metastatic area in the lungs, spleen and to the
liver. We performed ex vivo quantification of radioactivity from
individual organ by gamma counter after final SPECT scan and observed
similar distribution of the radio-labeled targeted exosomes. We also
labeled the exosomes with DiI dye and injected into the same mice
followed by euthanasia after 3 hours and organ collection. Fluorescent
imaging from the tumor and spleen showed the adherence of exosomes to
the CD206 positive macrophages confirming the targeting efficacy of the
exosomes. Henceforth, we intend to utilize these exosomes as a
therapeutic probe for carrying chemotherapeutic or antibody to intervene
the actions of M2-macrophages in primary and distal TME.