Abstract LB-363: Intravesical delivery of lipid nanoparticle formulated p21(Waf1/Cip1) activating dsRNA induces tumor regression and enhances animal survival in a orthotopic bladder cancer model

Abstract

Abstract Small RNA molecules are a promising new class of drugs by offering expanded targets not druggable by conventional therapies with high target specificity and low toxicity. However, their clinical use is significantly hindered by the lack of vehicles that deliver the molecules efficiently to target tissues and cells. The bladder is an easily accessible hollow organ and is ideal for local delivery of drugs or molecules such as small RNA. RNA activation (RNAa) is a newly discovered mechanism of gene induction triggered by promoter targeted double-stranded RNA, also known as small activating RNA (saRNA). In this study, we investigate, in an orthotopic bladder cancer model, antitumor effects of a saRNA (dsP21) targeting the promoter of the p21WAF1/CIP1 (p21) gene, a key negative regulator of the cell cycle rarely mutated or deleted in bladder cancer. Introducing dsP21 into bladder cancer cells activated p21 expression with subsequent inhibition of cell proliferation, arrest of the cell cycle and induction of apoptosis accompanied by the activation of caspase 3 and PARP. Chemical modification (2′-Fluoro) and subsequent formulation of dsP21 in lipid nanoparticles (LNPs) retained its RNAa activity with minimal immunostimulatory effect and extended its stability in urine, and when delivered intravesically it could well diffuse into the bladder wall. Delivery of LNP-formulated dsP21 (LNP-dsP21) into mouse bladder with established human bladder cancer significantly inhibited tumor growth and extended animal survival with demonstrated p21 activation in vivo. Of particular significance, LNP-dsP21 treatment caused the regression or disappearance of established tumors in 30% of the treated mice. Our results provide proof-of-principle that targeted activation of p21 can be applied to the treatment of bladder cancer and LNP-formulated small RNA can be successfully delivered to the bladder by intravesical instillation. Further clinical development of RNAa-based intravesical therapy is warranted for the treatment of residual and recurring bladder cancer in humans. Acknowledgement: financial support from the AACR Henry Shepard Bladder Cancer Research Grants (09-60-30-LI). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-363. doi:1538-7445.AM2012-LB-363