Background: Extracellular vesicles (EVs) have been shown to play an important role in intercellular communication as carriers of DNA, RNA and proteins. While the intercellular transfer of miRNA thorough EVs has been widely studied, the stability of extracellular miRNA (ex-miRNA) once engulfed by recipient cell remains to be determined.

Materials and Methods: Lung cancer cells (A549 cell line) were incubated with neutrophils or their supernatant or isolated EVs from these supernatant. Kinetics of expression of miR-223-3p were followed by RT-qPCR. FOXO1 expression and EMT expression markers were used as endpoints to follow effective effect or miR-223-3p in recipient cells.

Results: We identified the ex-miRNA-directed phenotype to be transient due to the rapid decay of the ex-miRNA. We demonstrated that the ex-miR-223-3p transferred from neutrophils to cancer cells was functional as demonstrated by the decreased expression of its target, FOXO1, and the occurrence of epithelial-mesenchymal transition reprogramming. We showed that the engulfed ex-miRNA, unlike endogenous miRNA, was unstable, enabling dynamic regulation and a return to a non-invasive phenotype within less than 8 hours. This transient phenotype could be modulated by targeting XRN1/PACMAN exonuclease. Indeed, its silencing was associated with slower decay of ex-miR-223-3p and subsequently prolonged the invasive properties.

Conclusion: We showed that the “steady step” level of engulfed miRNA (ex-miR-223-3p) and its subsequent activity was dependent on the presence of a donor cell in the surroundings to constantly fuel the recipient cell with ex-miRNAs and of XRN1 exonuclease, which is involved in the decay of these imported miRNAs.

Citation Format: Joséphine Zangari, Marius Ilie, Florian Rouaud, Laurie Signetti, Mickaël Ohanna, Robin Didier, Barnabé Roméo, Dana Goldoni, Nicolas Nottet, Cathy Staedel, Jocelyn Gal, Bernard Mari, Baharia Mograbi, Paul Hofman, Patrick Brest. Rapid decay of engulfed extracellular miRNA by XRN1 exonuclease promotes transient epithelial-mesenchymal transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3044. doi:10.1158/1538-7445.AM2017-3044