Research papers Anti-angiogenic inhibition of tumor growth by systemic delivery of PEI-g-PEG-RGD/pCMV-sFlt-1 complexes in tumor-bearing mice Won Jong Kim a , James W. Yockman a , Ji Hoon Jeong a , Lane V. Christensen a , Minhyung Lee b , Yong-Hee Kim b , Sung Wan Kim a, ⁎ a Center for Controlled Chemical Delivery, Department of Pharmaceutics and Pharmaceutical Chemistry, 20 S 2030 E RM 205 BPRB, University of Utah, Salt Lake City, UT 84112-5820, USA b Department of Bioengineering, College of Engineering, Hanyang University, Seoul, Korea Received 8 March 2006; accepted 31 May 2006 Available online 7 June 2006 Abstract Vascular endothelial growth factor (VEGF) is an endogenous mediator of tumor angiogenesis. Blocking associations of the VEGF with its corresponding receptors (Flt-1, KDR/flk-1) have become critical for anti-tumor angiogenesis therapy. Previously, we synthesized PEI-g-PEG-RGD conjugate and evaluated as an angiogenic endothelial polymeric gene carrier. In this study, PEI-g-PEG-RGD/pCMV-sFlt-1 complexes are evaluated in terms of tumor growth inhibition in vivo. Complexes were repeatedly injected systemically via tail vein into subcutaneous tumor-bearing mice. As a result, tumor growth was inhibited in the PEI-g-PEG-RGD/pCMV-sFlt-1 injected group. However, this effect was not identified in PEI-g-PEG/pCMV- sFlt-1 or PEI-g-PEG-RGD/pCMV-GFP control groups. Moreover, the survival rate increased in the PEI-g-PEG-RGD/pCMV-sFlt-1 group compared with the controls group. These results suggest that delivery of pCMV-sFlt-1 using PEG-g-PEG-RGD may be effective for anti-angiogenic gene therapy. © 2006 Elsevier B.V. All rights reserved. Keywords: Systemic injection; Anti-angiogenesis; Tumor therapy; Soluble Flt-1; Targeted gene delivery 1. Introduction Angiogenesis, the development of new blood vessels from the endothelium of a pre-existing vasculature, is a critical process required by most solid tumors to support their growth and metas- tasis [1–4]. Therefore, anti-angiogenic therapy has been demon- strated to be an attractive strategy for cancer treatment. Among the known angiogenic growth factors and cytokines implicated in the modulation of normal and pathological angiogenesis, the VEGF [3] family (VEGF-A, VEGF-B, VEGF-C, VEGF-D) and their corresponding receptor tyrosine kinases [VEGF-R1 (Flt-1), VEGF- R2 (KDR/flk-1) and VEGF-R3 (Flt-4)] play a paramount and indispensable role in regulating the angiogenic processes, as well as the induction of vascular permeability and inflammation [1,2,5–7]. Increased expression of VEGFs by tumor cells, VEGF-R1 (Flt-1) and VEGF-R2 (KDR/flk-1), by the tumor-associated vasculature is a hallmark of a variety of tumors in vivo and correlate with tumor growth rate, microvessel density/proliferation, tumor metastatic potential and poorer patient prognosis in a variety of malignancies [1–6]. The soluble form of VEGF-R1 (sFlt-1), an alternatively spliced form of Flt-1, is a potent endogenous agent for anti- angiogenic therapy. The sFlt-1 sequesters VEGF produced by tumor cells and forms a heterodimeric complex with a wild type VEGF receptor in a dominant negative fashion, inhibiting its signal transduction [8–11]. Recently, several reports have been published on gene therapy with the soluble VEGF receptors. These include ex vivo transfection of cancer cells with a plasmid encoding sFlt-1 receptor [12], regional administration of an adenovirus-mediated sFlt-1 cDNA [13], systemic administration of an adenovirus-mediated sFlt-1 cDNA [14] and intraperitoneal transduction of a sFlt-1 cDNA using HVJ-cationic liposomes [15]. However, the efficient delivery of anti-angiogenic genes to tumors remain a major obstacle. Especially in the case of the Journal of Controlled Release 114 (2006) 381 – 388 www.elsevier.com/locate/jconrel ⁎ Corresponding author. Tel.: +1 801 581 6834; fax: +1 801 581 7848. E-mail address: rburns@pharm.utah.edu (S.W. Kim). GENE DELIVERY 0168-3659/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jconrel.2006.05.029