Polyethylenimine-coated SPION exhibits potential intrinsic anti-metastatic properties inhibiting migration and invasion of pancreatic tumor cells Vladimir Mulens-Arias a,1 , José Manuel Rojas a,1 , Sonia Pérez-Yagüe a , María del Puerto Morales b , Domingo F. Barber a, ⁎ a Department of Immunology and Oncology and NanoBiomedicine Initiative, Centro Nacional de Biotecnología (CNB)/CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain b Department of Biomaterials and Bioinspired Materials, Instituto de Ciencia de Materiales de Madrid (ICMM)/CSIC, Sor Juana Inés de la Cruz 3, Cantoblanco, 28049 Madrid, Spain abstract article info Article history: Received 13 May 2015 Received in revised form 28 July 2015 Accepted 4 August 2015 Available online 8 August 2015 Keywords: Tumor cell invasion Nanoparticle Proliferation Matrix degradation Tumor cell migration Due to its aggressive behavior, pancreatic cancer is one of the principal causes of cancer-related deaths. The high- ly metastatic potential of pancreatic tumor cells demands the development of more effective anti-metastatic approaches for this disease. Although polyethylenimine-coated superparamagnetic iron oxide nanoparticles (PEI-coated SPIONs) have been studied for their utility as transfection agents, little is known of their effect on tumor cell biology. Here we demonstrated that PEI-coated SPIONs have potent inhibitory effects on pancreatic tumor cell migration/invasion, through inhibition of Src kinase and decreased expression of MT1-MMP and MMP2 metalloproteinases. When treated with PEI-coated SPIONs, the pancreatic tumor cell line Pan02 showed reduced invadosome density and thus, a decrease in their ability to invade through basement membrane. These nanoparticles temporarily downmodulated microRNA-21, thereby upregulating the cell migration inhibi- tors PTEN, PDCD4 and Sprouty-1. PEI-coated SPIONs thus show intrinsic, possibly anti-metastatic properties for modulating pancreatic tumor cell migration machinery, which indicates their potential as anti-metastatic agents for treatment of pancreatic cancer. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Pancreatic cancer is one of the most lethal pathologies worldwide, with only a 6% five-year relative patient survival rate [1–3]. The effec- tiveness of current chemotherapy, radiotherapy and surgical strategies is very limited. The aggressive phenotype of pancreatic cancer is one of the main factors in this outcome; the extreme invasiveness of pancre- atic tumor cells leads to formation of metastatic niches in adjacent tissues and organs, first in the abdomen and liver, and later in lungs, brain and bone [4,5]. There is thus an urgent need to find new anti- metastatic strategies that reverse this phenomenon. Research efforts have concentrated on superparamagnetic iron oxide nanoparticles (SPIONs), as they are used in magnetic resonance imaging (MRI) and cancer treatment [6,7]. The possible tuning of bio- logical effects by diversifying their surface chemistry [8] and thus, their biocompatibility and reactivity, endows these nanosystems with properties that might be exploited for additional pathologies [9–11]. Gene therapy is one approach to cancer treatment in which SPIONs have found application [12]. Some polycations (highly positive polymers) are used as a coating to stabilize SPIONs and to condense DNA/RNA, protecting them from the often aggressive biological micro- environment [13,14]. PEI stands out among polycations for use in gene delivery [11,15,16] due to the ‘sponge effect’, which leads to early endo- some rupture and DNA/RNA release into the cytoplasm. Due to their unique properties [17,18], the PEI/SPION combination has been ex- plored for cancer gene therapy, but the effect of ‘naked’ PEI-coated SPIONs on cells, in particular on tumor cells, has not been studied thoroughly. Inorganic nanoparticles, including SPIONs, can impair cell motility in a dose-dependent manner [19–21]. The underlying molecular mechanisms that lead to these effects, which might depend on cell type and nanoparticle surface charge and shape [22], are nonetheless poorly understood. Several parameters involved in tumor cell migration might be affected by nanoparticle treatment either directly, such as downmodulation of factors that induce cell death or immobilization, or indirectly via other processes such as mitochondrial respiration mechanism [23], which influence cytoskeletal rearrangement. Invadosomes or invadopodia are actin-rich structures with struc- tural and functional similarities to podosomes, which drive cell mi- gration and invasion [24,25]. Invadosomes are normally associated with tumor cell motility, as a molecular mechanism co-opted and deregulated from normal cells [26,27]. Invadopodia can nonetheless Journal of Controlled Release 216 (2015) 78–92 ⁎ Corresponding author. E-mail address: dfbarber@cnb.csic.es (D.F. Barber). 1 These authors contributed equally to this work. http://dx.doi.org/10.1016/j.jconrel.2015.08.009 0168-3659/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Controlled Release journal homepage: www.elsevier.com/locate/jconrel