Abstract 17622: Targeted Therapeutic Gene Knockdown Using Ultrasound and Microbubble-mediated Delivery of a Transcription Factor Decoy
Introduction: Ultrasound (US)-based therapies using microbubbles (MB) have the potential for targeted delivery of molecular therapies. Preclinical studies demonstrate that daily intratumoral injection of a STAT3 decoy inhibits STAT3 signaling and growth of squamous cell carcinoma (SCC), but daily tumor injection is invasive, cumbersome, and not clinically feasible. Thus, we tested the hypothesis that MB loaded with STAT3 decoy + US inhibit STAT3 signaling and tumor growth with in vitro and in vivo models of murine SCC.
Methods: Cationic lipid MB were loaded with STAT3 or mutant decoy as a control (10 μg decoy per 1х109 MBs). Therapeutic US was delivered using a clinical scanner (1.3 MHz, MI setting=1.6, 4 frames/burst, pulse interval 2 sec). Cultured SCC-VII cells expressing luciferase (luc) under a STAT3 responsive promoter were treated with US as MB were infused into the cell suspension over 5 min. Luc activity was measured 8 hrs post treatment. For in vivo studies, mice with subcutaneous SCC-VII tumors were treated with US during 20 min i.v. MB infusion every 3 days (total 3 treatments). Tumor volume was tracked with 3D US. Other control mice (no US) received i.v. infusions of 10 μg free STAT3 decoy or saline only.
Results: Compared to mutant decoy-loaded MB (n=13), US treatment of cells in vitro with STAT3 decoy-loaded MB (n=14) reduced luc expression by 28 ± 11% (p < 0.001). US treatment of tumor-bearing mice with STAT3 decoy MB (n=6) significantly increased tumor doubling time (DT) compared to control groups (n=7-8; p < 0.05, Figure 1). Compared to control groups, US and STAT3 decoy MB treated tumors were 31-40% smaller on day 4 (p < 0.02), 51-61% smaller on day 7 (p < 0.02), and 44-64% smaller on day 10 (p < 0.02).
Conclusions: US/MB treatment delivers a transcription factor decoy to selectively knock down gene expression and inhibit tumor growth. This approach has the potential to deliver small molecular weight therapeutic nucleic acids to target tissues in a range of diseases.
Author Disclosures: J.A. Kopechek: None. A.R. Carson: None. X. Chen: None. C.F. McTiernan: None. B. Hasjim: None. M. Sen: None. J.R. Grandis: None. F.S. Villanueva: None.
- © 2014 by American Heart Association, Inc.