Targeted RNAi of BIRC5/Survivin Using Antibody-Conjugated Poly(Propylene Imine)-Based Polyplexes Inhibits Growth of PSCA-Positive Tumors.

Willi Jugel,Achim Aigner,Stefanie Tietze,Gabriele Schackert,Dietmar Appelhans,Alexander Ewe,Susanne Michen,Achim Temme,Alexander Hagstotz

doi:10.3390/pharmaceutics13050676

Abstract

Delivery of siRNAs for the treatment of tumors critically depends on the development of efficient nucleic acid carrier systems. The complexation of dendritic polymers (dendrimers) results in nanoparticles, called dendriplexes, that protect siRNA from degradation and mediate non-specific cellular uptake of siRNA. However, large siRNA doses are required for in vivo use due to accumulation of the nanoparticles in sinks such as the lung, liver, and spleen. This suggests the exploration of targeted nanoparticles for enhancing tumor cell specificity and achieving higher siRNA levels in tumors. In this work, we report on the targeted delivery of a therapeutic siRNA specific for BIRC5/Survivin in vitro and in vivo to tumor cells expressing the surface marker prostate stem cell antigen (PSCA). For this, polyplexes consisting of single-chain antibody fragments specific for PSCA conjugated to siRNA/maltose-modified poly(propylene imine) dendriplexes were used. These polyplexes were endocytosed by PSCA-positive 293TPSCA/ffLuc and PC3PSCA cells and caused knockdown of reporter gene firefly luciferase and Survivin expression, respectively. In a therapeutic study in PC3PSCA xenograft-bearing mice, significant anti-tumor effects were observed upon systemic administration of the targeted polyplexes. This indicates superior anti-tumor efficacy when employing targeted delivery of Survivin-specific siRNA, based on the additive effects of siRNA-mediated Survivin knockdown in combination with scFv-mediated PSCA inhibition.

Highlights

The destruction of a specific cellular mRNA can be achieved by transfection of chemically synthesized small interfering RNAs (siRNAs) molecules, which enter the RNAi pathway
The silencing by siRNA is highly efficient due to RNA-induced silencing complex (RISC)-mediated protection of the guide strand from degradation and its catalytic activity, leading to the cleavage of many mRNA molecules [2]
We explore for the first time the targeted delivery of a therapeutic siRNA, namely Survivin-siRNA, using an maltosemodified PPI dendrimers (mPPI)-based polyplex system with scFv-mediated targeting of prostate stem cell antigen (PSCA), for treatment of PSCA-positive target cells and tumors

Summary

Introduction

The siRNA-mediated silencing (RNAi) of genes utilizes a conserved biological process among multicellular organisms that mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes. It relies on 21 bp to 23 bp doublestranded, so-called small interfering RNAs (siRNAs), whose guide strand is integrated into the RNA-induced silencing complex (RISC), which, upon sequence-specific binding, Pharmaceutics 2021, 13, 676. Pharmaceutics 2021, 13, 676 promotes the destruction of target mRNAs through an enzymatic activity integrated in the complex [1]. The silencing by siRNA is highly efficient due to RISC-mediated protection of the guide strand from degradation and its catalytic activity, leading to the cleavage of many mRNA molecules [2]

Methods

Results

Conclusion