Abstract 1977: Therapeutic miRNAs targeted selectively to tumors by mesenchymal stem cell derived microparticles
Authors: Prokopi Marianna , Epenetos Agamemnon , Anayiotos Andreas , Pitsillides Costas , Kapnisis Konstantinos , Kousparou Christina 
Published: May 2015

Introduction: MiRNAs have been implicated in the development of some if not all cancer types and have been identified as attractive targets for therapy. However, systemic delivery of bare miRNAs faces its own set of limitations because of degradation by RNases and filtration and excretion by the kidneys. In this work we propose miRNAs as therapeutic agents. We have developed a novel system for miRNA delivery applicable for both local and systemic administration with the use of mesenchymal stem cell (MSC) microparticles (MPs).

Methodology: MSCs were isolated from the Wharton's jelly of human umbilical cords. The MSC cultures were subjected to serum deprivation, leading to the formation of MPs (secreted membrane vehicles &lt;1μm) which were harvested and characterized by SEM, PCR, FACS and Fluorescence Microscopy. Breast (MDA-MB-231 & MCF-7), colon (RKO & HT-29) and ovarian adenocarcinoma (SKOV3) cell lines were then exposed to MPs. The response to treatment was evaluated by cell morphology, proliferation, migration, gene expression and apoptosis. Furthermore, the therapeutic potential of MPs was tested in vivo in xenograft tumor mouse models. Innovative imaging modalities such as in vivo flow cytometry and whole body fluorescence-bioluminescence were employed to dynamically investigate the biodistribution and homing kinetics of MPs in mice.

Results: In vitro experiments confirmed that MSC-derived MPs can be internalized by the various cancer cell lines and induce a biological effect as evidenced by membrane damage, cell shrinkage and blebbing in the recipient cell. Significantly, there was evidence that MPs induce apoptosis, inhibit cell proliferation and tumor growth attenuation in a dose/time-dependent manner. The pro-apoptotic and anti-migration effects of MPs in cancer cells were almost completely abrogated by RNase treatment before administration to cultures. In vivo studies demonstrated that we were able to monitor and quantify fluorescently labelled MPs in circulation and to detect and image the biodistribution and incorporation in cells and organs in healthy and tumor-bearing mice.

Conclusion: MSC-derived MPs containing miRNAs possess tumor inhibitory properties both in vitro and in vivo. Administration of MPs after RNase treatment induces the loss of anti-cancer properties suggesting a horizontal transfer of small RNAs from MPs to cancer cells. MPs formulated to contain specific miRNAs, could affect the action of genes associated with carcinogenesis, neovascularization, metastasis and other cancer characteristics, thus leading to therapeutic benefit.

Citation Format: Marianna Prokopi, Agamemnon Epenetos, Andreas Anayiotos, Costas Pitsillides, Konstantinos Kapnisis, Christina Kousparou. Therapeutic miRNAs targeted selectively to tumors by mesenchymal stem cell derived microparticles. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1977. doi:10.1158/1538-7445.AM2014-1977