A self-assembled polymeric micellar immunomodulator for cancer treatment based on cationic amphiphilic polymers Hyeona Yim a, 1 , Wooram Park a, 1 , Dongin Kim b , Tarek M. Fahmy b, c , Kun Na a, * a Department of Biotechnology, The Catholic University of Korea, 43 Jibong-ro, Wonmi-gu, Bucheon-si, Gyeonggi do 420-743, Republic of Korea b Department of Biomedical Engineering, Yale University, 55 Prospect St., New Haven, CT 06511, USA c Department of Chemical and Biomedical Engineering, Yale University, 55 Prospect St., New Haven, CT 06511, USA article info Article history: Received 12 August 2014 Accepted 17 August 2014 Available online xxx Keywords: Cancer Cationic polymer Self-assembly Necrosis Antitumor immune responses abstract Here, we report a self-assembled polymeric micellar immunomodulator (SPI) for enhanced cancer treatment based on cationic amphiphilic polymers. To obtain the cationic amphiphilic polymer, the hydrophobic all-trans-retinoic acid (ATRA) was conjugated with a hydrophilic low-molecular-weight PEI ( Low PEI, M n ¼ 1.8 kDa). The ATRAe Low PEI conjugates could self-assemble in aqueous media, forming micelles with a strong positive charge (~þ40 mV) and particle sizes of ~70 nm. Compared to conventional therapeutic agents (e.g., cisplatin), the SPI exhibited enhanced anti-cancer activity regardless of drug resistance. After mechanistic in vitro cell death studies, we revealed that the mechanical disruptive force generated by the cationic charge of SPI primarily induced necrotic cell death. Furthermore, the organelle fragments induced by the necrotic cell death triggered antitumoral immune responses. Therefore, SPI induced synergistic effects of the cationic charge-induced necrosis and antitumoral immune responses could produce an effective cancer treatment. In addition, the SPI was shielded by hyaluronic acid (HA/SPI complex) to enhance its tumor selectivity in vivo. Finally, the HA/SPI complex accumulated selectively into tumor sites after systemic administration into tumor-bearing mice, exhibiting effective antitumoral effects without systemic toxicity. Therefore, this technology holds great potential for translation into a clinical cancer treatment. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Despite the great efforts to develop cancer treatments, including new chemotherapeutic drugs, the clinical therapeutic efficacies of conventional chemotherapy are not as high as expected due to their lack of selectivity and their susceptibility to resistance [1]. More- over, because tumors consist of a heterogeneous population of malignant cancer cells carrying multiple genetic mutations, drug resistance arises from additional genetic and epigenetic alterations [2,3]. Consequently, treating cancer with a single low molecular chemotherapeutic drug is almost impossible [4]. Cancer immunotherapy holds great potential as a treatment strategy; it might enhance the natural ability of the immune system to recognize and kill cancer cells [5e8]. Modulating immune re- sponses by administrating cytokines (e.g., interleukin-12 (IL-12)) that facilitate the innate and adaptive immune systems is one of the most effective strategies used in cancer immunotherapy [6,9,10]. However, similar to many other therapeutic proteins, cytokine- based cancer immunotherapeutic strategies still have only limited clinical applications due to their instability and very low in vivo targeting efficiency [11]. Additionally, due to the difficulties encountered when manufacturing these cytokines, these thera- peutic proteins are relatively expensive, limiting their clinical use [12]. Recently, many studies have revealed the relationship between the modes of cancer cell death (e.g., apoptosis and necrosis) and the efficiency of inducing an immune response. The methods of cancer therapy that predominantly induce necrosis are significantly better than the methods that predominantly induce apoptosis when activating the immune system. During necrosis, the cytosolic con- stituents spill into the extracellular region through the damaged plasma membrane, promoting a powerful inflammatory response. More recently, we reported that cationic polymers, such as poly- ethylenimine (PEI), exhibit strong anti-cancer effects through ne- crosis due to cationic charge-induced cellular membrane damage [13,14]. * Corresponding author. E-mail address: kna6997@catholic.ac.kr (K. Na). 1 These authors contributed equally to this work. Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials http://dx.doi.org/10.1016/j.biomaterials.2014.08.029 0142-9612/© 2014 Elsevier Ltd. All rights reserved. Biomaterials xxx (2014) 1e8 Please cite this article in press as: Yim H, et al., A self-assembled polymeric micellar immunomodulator for cancer treatment based on cationic amphiphilic polymers, Biomaterials (2014), http://dx.doi.org/10.1016/j.biomaterials.2014.08.029