Polymer nanoparticles for enhanced immune response: Combined delivery of tumor antigen and small interference RNA for immunosuppressive gene to dendritic cells Min Beom Heo a , Mi Young Cho a , Yong Taik Lim b,⇑ a Graduate School and Department of Analytical Science and Technology, Chungnam National University, Yuseong, Daejeon 305-764, Republic of Korea b SKKU Advanced Institute of Nanotechnology (SAINT), School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea article info Article history: Received 19 June 2013 Received in revised form 3 December 2013 Accepted 26 December 2013 Available online 4 January 2014 Keywords: Nanoparticles Dendritic cells Antigen delivery SOCS1 Cancer vaccine abstract In this study, we report on polymer nanoparticles (NPs) that can induce an enhanced immune response in dendritic cell (DC)-based cancer immunotherapy by the combined delivery of tumor antigen and small interference RNA (siRNA) for the immunosuppressive gene to DCs. DCs are specialized antigen-presenting cells (APCs) that capture, process and present antigens and induce an antigen-specific cytotoxic T lymphocyte response. Because the suppressor of cytokine signaling 1 (SOCS1) is a negative regulator of the APC-based immune response, the inhibition of SOCS1 gene expression is essential for DCs to enhance antigen-specific anti-tumor immunity. Multifunctional poly(lactide-co-glycolic acid) (PLGA) NPs that can deliver tumor antigen and siRNA for immunosuppressive SOCS1 genes to DCs simultaneously were fabricated by the emulsion solvent evaporation method. We have found that the encapsulation efficiency of small-sized and hydrophilic SOCS1 siRNA into hydrophobic PLGA matrix is drastically enhanced by the help of a tumor model antigen such as ovalbumin (OVA), and the encapsulation efficiency of siRNA in PLGA (SOCS1 siRNA only) NPs and PLGA (OVA/SOCS1 siRNA) NPs was 2% and 57.6%, respectively. PLGA (OVA/SOCS1 siRNA) NPs were efficiently taken up by bone-marrow-derived dendritic cells (BMDCs) and showed no detectable toxic effect. The knockdown of SOCS1 in BMDCs by PLGA (OVA/SOCS1 siRNA) NPs enhanced pro-inflammatory cytokine (tumor necrosis factor-alpha (TNF-a), interleukin-6 (IL-6), IL-12 and IL-2) expression. Additionally, PLGA (OVA/SOCS1 siRNA) NP-treated BMDCs could elicit an immune response through cross-presentation in OVA-specific CD8 T cells that express IL-2 cytokine. Taken together, the combined delivery of NPs that can deliver both tumor antigen and immunosuppressive gene siRNA to BMDCs simultaneously could be a potent strategy to enhance immunotherapeutic effects in BMDC-based cancer therapy. Ó 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. 1. Introduction Nanostructured materials have been used as delivery systems for antigens and adjuvant molecules in immune cell-based cancer therapies [1–8]. Polymer nanoparticles fabricated from biodegrad- able and biocompatible polymers, such as poly(lactide-co-glycolic acid) (PLGA), have been attractive as delivery carriers of small molecules, peptides and proteins, due to their efficient controlled release properties. In cancer immunotherapy, these copolymers are attractive from a clinical point of view because they show minimal systemic toxicity and have been approved for human use by the US Food and Drug Administration (FDA) [9,10]. Dendritic cells (DCs) are specialized antigen-presenting cells that capture, process and present antigens and induce an antigen-specific cytotoxic CD8 + T lymphocyte response. Immunization of DCs loaded with antigen such as ovalbumin (OVA) protein can induce an antigen-specific immune response by efficiently presenting to T cells [11]. In an antigen presentation pathway, a process known as cross-presentation allows DCs to load extracellular antigenic peptides on major histocompatibility complex (MHC)-I molecules, which is important for activating cytotoxic T cells. Many studies have reported that antigen-loaded PLGA particles elicit cytotoxic T cell responses through antigen cross-presentation pathways [12,13]. Moreover, many research scientists have focused on the promotion of DC maturation and activation for enhanced anti- tumor immunity [14]. However, immunosuppressive factors, such as suppression of cytokine signaling 1 (SOCS1), represent a major http://dx.doi.org/10.1016/j.actbio.2013.12.050 1742-7061/Ó 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +82 42 821 8543; fax: +82 42 821 8541. E-mail address: yongtaik@cnu.ac.kr (Y.T. Lim). Acta Biomaterialia 10 (2014) 2169–2176 Contents lists available at ScienceDirect Acta Biomaterialia journal homepage: www.elsevier.com/locate/actabiomat