Tracking of Tumor Cell–Derived Extracellular Vesicles In Vivo Reveals a Specific Distribution Pattern with Consecutive Biological Effects on Target Sites of Metastasis

Abstract

Purpose: Extracellular vesicles, small vesicles carrying inter alia proteins, miRNA and RNA, are important mediators of intercellular communication. The purpose of this study was to assess the distribution of extracellular vesicles from highly malignant breast cancer and their subsequent effect on the immune cell infiltrate in target organs of metastasis. Procedures: Extracellular vesicles were isolated from the tissue culture supernatant of highly malignant 4T1 breast cancer cells or the serum of healthy BALB/c mice. The purity of the isolate was verified by electron microscopy and western blotting. Extracellular vesicles were additionally subjected to proteome analysis. After labeling with the fluorescent dye DiR, extracellular vesicles were injected into healthy BALB/c mice and their in vivo distribution was assessed using fluorescence reflectance imaging (FRI). Following ex vivo imaging of the organs, lung tissue samples were analyzed for extracellular vesicle-mediated changes of myeloid cells and T cell numbers, using flow cytometry. Proteome analysis revealed major differences in the cargo of tumor cell-derived versus extracellular vesicles from healthy serum.

Thinking Quantitatively of RNA-Based Information Transfer via Extracellular Vesicles: Lessons to Learn for the Design of RNA-Loaded EVs

“…We considered a 5 fold increase in inflamed tissues as a good approximation using this analogy. Tumors were shown to accumulate up to 18% of MSC-EVs [96] (rather 0.5-4% in our experience [97] and in other reported data [98]) and tumor-derived EVs seems to display a very similar distribution profile (±30%) compared to serum EVs [99]. We make the assumption that EV uptake and endosomal escape should be similar in a physiological and pathological context, although EV uptake might be biased towards a specific cell population.…”

Tumor extracellular vesicles drive metastasis (it's a long way from home)

“…Importantly, EVs from different cell types tend to accumulate in different organs and in general injected EVs do not arrest at the first capillary bed they encounter, suggesting the existence of specific targeting or retention mechanisms 106 . Indeed, an increasing number of studies demonstrated the existence of tumor EVs organotropism by showing that they accumulate preferentially in the organs where their secreting cells mostly form metastasis 35,46,52,109,110 . Similar to tumor cell organotropism, tumor EV organotropism could be dictated by a balance between hemodynamics, vascular patterns, and intrinsic adhesive properties 5,111 .…”

“… 106 Indeed, an increasing number of studies demonstrated the existence of tumor EVs organotropism by showing that they accumulate preferentially in the organs where their secreting cells mostly form metastasis. 35 , 46 , 52 , 109 , 110 Similar to tumor cell organotropism, tumor EV organotropism could be dictated by a balance between hemodynamics, vascular patterns, and intrinsic adhesive properties. 5 , 111 Accordingly, circulating EVs were shown to accumulate mostly in vascular regions with a low blood flow speed in zebrafish embryo.…”

How Different Albumin-Binders Drive Probe Distribution of Fluorescent RGD Mimetics

“…nanomedicines ( Kunjachan et al, 2013 ). FRI has been shown to be particularly feasible for evaluation of murine xenograft models in nude mice, where absorption and scattering of superficial tissue and fur are negligible ( Ntziachristos et al, 2003 ; Gerwing et al, 2020 ). FMT can be used for a deeper insight into the murine body ( von Wallbrunn et al, 2007 ; Razansky et al, 2012 ; An et al, 2018 ), especially when combined with small animal CT (µCT) in a hybrid system, where a considerable benefit for the accuracy of signal correlation and additional attenuation correction for improved signal quantification can be realized ( Rosenhain et al, 2017 ).…”