Abstract 3313: Biocompatible nanocarrier mediated delivery of STAT-6 siRNA to cancer cells.
Authors: Youngren Susanne R. , Tekade Rakesh K. , Hoffmann Peter R. , Chougule Mahavir B. 
Published: August 2014

Signal transducer and activator of transcription 6 (STAT-6) is a transcription factors that is highly expressed in various types of cancers including lung cancer and its expression was reported to be significantly correlated with tumor progression. Several studies showed that down-regulation of STAT-6 using short interfering RNA (siRNA) leads to the induction of apoptosis and inhibition of tumor growth. The use of siRNA for cancer therapy represents a promising approach for STAT-6 silencing due to its efficient knockdown of targeted genes compared to other conventional anti-cancer therapies. Despite this huge therapeutic potential, the clinical utility of siRNA therapy has been greatly hampered due to its poor cell penetration, rapid degradation, short half-life and non-specific effects.

To overcome these limitations, we herewith propose to formulate STAT-6 siRNA (S6S) as a nanotherapeutic by encapsulating them within the gelatin nanocarrier (GNC) to achieve its successful intratumoral delivery. The nanoformulation was prepared by two step desolvation technique and characterized exhaustively for loading efficiency, size, charge, release kinetics, stability and cytotoxicity performance. The stability of S6S-GNC was assessed under conditions of varying pH and serum level to determine the stability of developed formulation. The S6S-GNC was incubated in a phosphate buffer (pH 6.4, 7.4 and 8.4) to assess the influence of pH on charge and size of the GNC. Additionally, the stability was also accessed using an electrophoretic assay. In vitro cytotoxicity was evaluated against A549 lung cancer cells following MTT cytotoxicity assay. The developed formulation contained ≈10,000 GNC/ml, and the average particle size and surface charge was observed to be 69.6±6.5 nm and +10±1.5 mV, respectively. The optimized S6S-GNC formulations showed an encapsulation efficiency of 85±4%. S6S-GNC showed an insignificant (p&gt;0.05) change in the size in the presence of buffer solutions (pH 6.4 to 8.4) and FBS (10% v/v). A549 cells were treated with native S6S, S6S-lipofectamine, placebo GNC and S6S-GNC using untreated cells as a control. It was observed that cell viability was decreased significantly with S6S-GNC by 55±4 % (p&lt;0.001) compared to native S6S (2±0.5%) and S6S-lipofectamine (40±3 %). Placebo GNC treatment showed &gt;97% viability of cells demonstrating non-toxicity and safety of GNC formulation The increased cytotoxicity with S6S-GNC can be attributed to the accumulation of positively charged GNCs through electrochemical diffusion. Overall, these results suggest FDA approved gelatin polymer based nanocarriers may be a more robust, stable and biocompatible strategy to deliver S6S via parenteral route with the potential to develop them as cancer targeted nanocarrier by subsequently anchoring them to cancer specific ligands (such as RGD, Folate etc) via freely available amine and carboxy terminals of gelatin.

Citation Format: Susanne R. Youngren, Rakesh K. Tekade, Peter R. Hoffmann, Mahavir B. Chougule. Biocompatible nanocarrier mediated delivery of STAT-6 siRNA to cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3313. doi:10.1158/1538-7445.AM2013-3313