Reconstructed Stem Cell Nanoghosts: A Natural Tumor Targeting Platform Naama E. Toledano Furman, Yael Lupu-Haber, Tomer Bronshtein, Limor Kaneti, Nitzan Letko, Eyal Weinstein, Limor Baruch, and Marcelle Machluf* ,† Faculty of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel * S Supporting Information ABSTRACT: The ultimate goal in cancer therapy is achieving selective targeting of cancer cells. We report a novel delivery platform, based on nanoghosts (NGs) produced from the membranes of mesenchymal stem cells (MSCs). Encompassing MSC surface molecules, the MSC-NGs retained MSC-specific in vitro and in vivo tumor targeting capabilities and were cleared from blood-filtering organs. MSC-NGs were found to be biocompatible. Systemic administration of drug loaded MSC-NGs demonstrated 80% inhibition of human prostate cancer. KEYWORDS: Nanoghosts, drug delivery, mesenchymal stem cells, cancer targeted therapy T he ultimate goal in cancer therapy is a “magic bullet” that allows selective targeting of cancer cells. 1,2 Three main considerations must be addressed when designing any such delivery system: biocompatibility, long circulation time, and selectivity. 1 In cancer therapy, passively targeted drug-carrying particles are still the predominantly used drug-delivery platform. 1 On the basis of their nanosize and physical properties, such systems were shown to accumulate in the tumor surroundings, owing to the enhanced permeability and retention (EPR) effect of tumor vasculature and microenvironment. Passive targeting, however, is still limited due to varying degrees of tumor vascularization and permeability affected by the tumor type and stage. 3 To overcome these limitations, active cancer targeting moieties, such as antibodies, have been incorporated into polymeric drug-carriers made from nanoparticles, micelles, or liposomes. 4-6 However, the relatively short circulation times 4 and the complexity of producing such actively targeted carriers 7 hinder their clinical applications. Here we report on a novel targeted delivery platform, based on nanoghosts (NGs) that are reconstructed from the whole cell membrane of mesenchymal stem cells (MSCs). To ensure targeting, the lineage integrity of the MSCs from which the NGs were produced was continuously validated using flow cytometry for typical MSC markers (Supporting Information Figure S1). In contrast to exosomes or other extracellular vesicles that are shed or bud from cells, MSC-NGs are manufactured in a reproducible process by isolating intact MSC cell membranes (ghost cells), and homogenizing them into nanosized vesicles (nanoghosts) while entrapping a therapeutic of choice. This approach, presenting a new paradigm for active cancer-targeted drug- delivery, is supported by our previous publication demonstrating the in vitro targeting of HIV-infected cells by NGs expressing the receptor for a viral ligand found on infected cells. 8,9 The reasoning for choosing MSCs as a source to produce cancer-targeting NGs lies in their hypo-immunogenicity and ability to target many kinds of cancers at different developmental stages. 10,11 Such targeting was shown to involve both chemo- taxis 12 and surface interactions. 13 Nonetheless, isolated mem- brane fractions of tumor cells, and not their cytoplasmatic fractions, appear to contain the most potent MSC attrac- tants. 14,15 The MSC targeting mechanism is also known to be tumor-specific but not species-specific, allowing the targeting of susceptible tumors by MSCs isolated from different species. 16,17 Moreover, MSCs expressing exogenous anticancerous proteins, suggested for cell-based cancer therapy due to their homing abilities and hypo-immunogenicity, demonstrate some benefits when administered as whole cells into animal models. 18 Therefore, using MSC-derived NGs (MSC-NGs), a variety of tumors requiring MSC support 10,19 may be targeted by their own invitation, extended to these Trojan horses. Most importantly, this targeting system does not entail the elaborate production of targeting molecules and their incorporation into passive vehicles, constituting a simpler and more clinically relevant approach than existing particulate drug-delivery vehicles. Unlike exosomes, shed-vesicles or cell-based delivery systems, which are predom- inantly intended for the delivery of products manufactured by the Received: April 17, 2013 Revised: June 6, 2013 Published: June 20, 2013 Letter pubs.acs.org/NanoLett © 2013 American Chemical Society 3248 dx.doi.org/10.1021/nl401376w | Nano Lett. 2013, 13, 3248-3255