Paclitaxel is incorporated by mesenchymal stromal cells and released in exosomes that inhibit in vitro tumor growth: A new approach for drug delivery Luisa Pascucci a , Valentina Coccè b , Arianna Bonomi b , Diletta Ami c , Piero Ceccarelli a , Emilio Ciusani f , Lucia Viganò d , Alberta Locatelli d , Francesca Sisto b , Silvia Maria Doglia g , Eugenio Parati e , Maria Ester Bernardo h , Maurizio Muraca i , Giulio Alessandri e , Gianpietro Bondiolotti j , Augusto Pessina b, ⁎ a Department of Veterinary Medicine, University of Perugia, Italy b Department of Biomedical, Surgical and Dental Sciences, University of Milan, Milan, Italy c Department of Biotechnology and Biosciences, University of Milan Bicocca, Milan, Italy d Department of Medical Oncology, Ospedale S. Raffaele Scientific Institute, Milan ,Italy e Cellular Neurobiology Laboratory, Department of Cerebrovascular Diseases, IRCCS Neurological Institute C. Besta, Milan, Italy f Laboratory of Clinical Pathology and Neurogenetic Medicine, Fondazione IRCCS Neurological Institute Carlo Besta, Milan, Italy g Department of Physics, University of Milan Bicocca, Milan, Italy h Department of Onco-Hematology, Children's Hospital Bambino Gesù, Roma, Italy i Laboratory Medicine, Children's Hospital Bambino Gesù, Roma, Italy j Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy abstract article info Article history: Received 29 March 2014 Accepted 20 July 2014 Available online 30 July 2014 Keywords: Mesenchymal stromal cells Exosome Microvesicles Paclitaxel Drug delivery Mesenchymal stromal cells (MSCs) have been proposed for delivering anticancer agents because of their ability to home in on tumor microenvironment. We found that MSCs can acquire strong anti-tumor activity after priming with Paclitaxel (PTX) through their capacity to uptake and then release the drug. Because MSCs secrete a high amount of membrane microvesicles (MVs), we here investigated the role of MVs in the releasing mechanism of PTX. The murine SR4987 line was used as MSC model. The release of PTX from SR4987 in the conditioned medium (CM) was checked by HPLC and the anti-tumor activity of both CM and MVs was tested on the human pancreatic cell line CFPAC-1. MVs were isolated by ultracentrifugation, analyzed by transmission (TEM) and scanning elec- tron microscopy (SEM), and the presence of PTX by the Fourier transformed infrared (FTIR) microspectroscopy. SR4987 loaded with PTX (SR4987PTX) secreted a significant amount of PTX and their CM possessed strong anti- proliferative activity on CFPAC-1. At TEM and SEM, SR4987PTX showed an increased number of “vacuole-like” structures and shed a relevant number of MVs, but did not differ from untreated SR4987. However, SR4987PTX-derived-MVs (SR4987PTX-MVs) demonstrated a strong anti proliferative activity on CFPAC-1. FTIR analysis of SR4987PTX-MVs showed the presence of an absorption spectrum in the corresponding regions of the PTX marker, absent in MVs from SR4987. Our work is the first demonstration that MSCs are able to package and deliver active drugs through their MVs, suggesting the possibility of using MSCs as a factory to develop drugs with a higher cell-target specificity. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Mesenchymal stromal cells (MSCs) have been indicated as a poten- tial new important tool for delivering anticancer agents [1,2]. The ther- apeutic use of MSCs is mainly favored by the easy procedures for their isolation and in vitro expansion, combined with their presence in many different mammal tissues (e.g. adipose tissue, bone marrow, skin, umbilical cord blood, placenta, etc.). More important, it has also been demonstrated that MSCs, after systemic injection, are able to home in on inflammatory microenvironments or are able to migrate into tumor mass [3]. Based on these MSC properties, several laboratories set up models of engineered MSCs for producing anti-cancer molecules (such as interferons, interleukins, chemokines) to be delivered more specifically into the tumor microenvironment [4–6]. Besides the ability to engineer MSCs, we have recently shown that MSCs are able to deliver drugs without genetic manipulation. Indeed, Journal of Controlled Release 192 (2014) 262–270 ⁎ Corresponding author at: Department of Biomedical, Surgical and Dental Sciences, University of Milan, Via Pascal 36, 20133 Milan, Italy. Tel.: +39 02 50315072; fax: +39 02 50315093. E-mail address: augusto.pessina@unimi.it (A. Pessina). http://dx.doi.org/10.1016/j.jconrel.2014.07.042 0168-3659/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Controlled Release journal homepage: www.elsevier.com/locate/jconrel