Please cite this article in press as: Gul-Uluda˘ g H, et al. Polymeric nanoparticle-mediated silencing of CD44 receptor in CD34 + acute myeloid leukemia cells. Leuk Res (2014), http://dx.doi.org/10.1016/j.leukres.2014.08.008 ARTICLE IN PRESS G Model LR-5232; No. of Pages 10 Leukemia Research xxx (2014) xxx–xxx Contents lists available at ScienceDirect Leukemia Research journa l h om epage: www.elsevier.com/locate/leukres Polymeric nanoparticle-mediated silencing of CD44 receptor in CD34 + acute myeloid leukemia cells Hilal Gul-Uluda˘ g a,∗ , Juliana Valencia-Serna a , Cezary Kucharski a , Leah A. Marquez-Curtis b , Xiaoyan Jiang c,d , Loree Larratt e , Anna Janowska-Wieczorek b,e , Hasan Uluda˘ g a,f,g a Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada b Canadian Blood Services, Centre for Innovation (Formerly R&D), Edmonton, Alberta, Canada c Terry Fox Laboratory, British Columbia Cancer Agency, Canada d Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada e Department of Medicine, University of Alberta, Edmonton, Alberta, Canada f Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta, Edmonton, Alberta, Canada g Faculty of Pharmacy & Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada a r t i c l e i n f o Article history: Received 11 May 2014 Received in revised form 15 July 2014 Accepted 16 August 2014 Available online xxx Keywords: CD44 receptor Acute myeloid leukemia Polymeric nanoparticle siRNA silencing a b s t r a c t The adhesion receptor CD44 plays an important role in the survival and retention of leukemic stem/progenitor cells (LSPC) within the bone marrow (BM) niche, as well as in the high relapse rates of acute myeloid leukemia (AML). Down-regulating CD44 could be clinically relevant not only for suppression of the deregulated function of LSPC but also in LSPC response to chemotherapeutic agents. Small interfering RNA (siRNA) delivery is a promising approach for AML treatment, and we recently reported effective siRNA delivery into difficult-to-transfect AML cell lines using lipid-substituted polyethylenimine/siRNA complexes (polymeric nanoparticles). In this study, we investigated polymeric nanoparticle-mediated silencing of CD44 in CD34 + LSPC cell models (leukemic KG-1 and KG-1a cell lines) as well as primary AML cells. Polymeric nanoparticle-mediated silencing decreased surface CD44 levels in KG-1, KG-1a and primary AML cells by up to 27%, 30% and 20% at day 3, respectively. Moreover, CD44 silencing resulted in induction of apoptosis in KG-1 cells, reduced adhesion of KG-1 and KG-1a cells to hyaluronic acid-coated cell culture plates and BM-MSC, and decreased adhesion of primary AML cells to BM-MSC. Our results suggest that polymeric nanoparticle-mediated silencing of CD44 might be a useful technique for inhibiting LSPC interactions with their microenvironment, thereby prohibiting leukemia progression or sensitizing LSPC to chemotherapy. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Acute myeloid leukemia (AML), a heterogeneous group of dis- orders, arises from critical genetic alterations in hematopoietic stem/progenitor cells (HSPC) that alter normal mechanisms of self- renewal, proliferation and differentiation [1]. The most effective way to eradicate AML is to use cytotoxic drugs, the current standard of clinical care. AML cells generally respond well to therapy at the onset of treatment, but even the most advanced drugs lose their effectiveness over the long term, and relapse rates remain quite high (more than 85%) [2,3]. The high relapse rate in AML ∗ Corresponding author at: Department of Biomedical Engineering, University of Alberta, 2-020 Research Transition Facility, Edmonton, Alberta T6G 2V2, Canada. Tel.: +1 780 492 0344; fax: +1 780 492 2881. E-mail address: hilal.gul@ualberta.ca (H. Gul-Uluda˘ g). patients has been attributed to existence of a rare population of leukemia stem/progenitor cells (LSPC) [4,5]. LSPC, which are capa- ble of propagating leukemia, are able to engraft, self-renew, and interact similar to normal HSPC with cells within the bone marrow (BM) niche (e.g., mesenchymal stromal cells (MSC) and osteoblasts) [6,7]. In fact, during the development of leukemia, the BM niche converts into an environment with dominant signals that favor LSPC survival and expansion and protect LSPC from chemother- apy [8–10]. Thus, the development of novel strategies to displace these cells from the BM niche is required for the inhibition of AML progression and elimination of drug resistance. The adhesion receptor CD44, a ubiquitously expressed trans-membrane glycoprotein that mediates cell–cell and cell–extracellular matrix interactions through binding with its major ligand hyaluronic acid (HA) [11], has been shown to play a pivotal role in the trafficking of HSPC [11] and in the homing and maintenance of AML LSPC [12]. In fact, it has been reported that http://dx.doi.org/10.1016/j.leukres.2014.08.008 0145-2126/© 2014 Elsevier Ltd. All rights reserved.