Tumor microenvironmental cytokines bound to cancer exosomes determine uptake by cytokine receptor-expressing cells and biodistribution

Metastatic spread of a cancer to secondary sites is a coordinated, non-random process. Cancer cell-secreted vesicles, especially exosomes, have recently been implicated in the guidance of metastatic dissemination, with specific surface composition determining some aspects of organ-specific localization. Nevertheless, whether the tumor microenvironment influences exosome biodistribution has yet to be investigated. Here, we show that microenvironmental cytokines, particularly CCL2, decorate cancer exosomes via binding to surface glycosaminoglycan side chains of proteoglycans, causing exosome accumulation in specific cell subsets and organs. Exosome retention results in changes in the immune landscape within these organs, coupled with a higher metastatic burden. Strikingly, CCL2-decorated exosomes are directed to a subset of cells that express the CCL2 receptor CCR2, demonstrating that exosome-bound cytokines are a crucial determinant of exosome-cell interactions. In addition to the finding that cytokine-conjugated exosomes are detected in the blood of cancer patients, we discovered that healthy subjects derived exosomes are also associated with cytokines. Although displaying a different profile from exosomes isolated from cancer patients, it further indicates that specific combinations of cytokines bound to exosomes could likewise affect other physiological and disease settings.


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Software and code
Policy information about availability of computer code Data collection Biotek Gen5™ microplate reader software v2.09 (Bradford, BCA and ELISA assays); BD FACSDiva™ software v8 (acquisition of flow cytometric data); PerkinElmer Living Image software v4.4 (acquisition of fluorescence images of harvested tissues).
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Life sciences study design
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Female C57Bl/6 wild-type mice were used at 8-10 weeks of age and purchased from the Walter and Eliza Hall Institute (Melbourne, Australia). C57Bl/6 CCR2-/-mice were bred and maintained at the QIMR Berghofer Medical Research Institute. Animals were housed in passive air flow EVC (environmentally ventilated cage) mice system. These mouse cages are housed in an environmentally controlled room that is maintained at 20oC-21oC, 60% relative humidity and a 12 hour light cycle (8am to 8pm) with no external or natural light sources. All exhaust air from the mouse racks is vented external to the building.

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