RNA interference in vivo: toward synthetic small inhibitory RNA-based therapeutics.

Small interfering RNA (siRNA) mediated inhibition of gene expression has rapidly become a major tool for in vitro analysis of protein function. In vivo gene silencing by siRNAs will play an important role for target validation and is the first step towards the development of siRNA-based therapeutics. This chapter reviews the early and intriguing successes in using siRNAs for in vivo gene silencing. The impact of chemical modification on siRNA efficacy in vitro and the potential for employing such modifications to alter the pharmacokinetic properties of siRNAs is also summarized. A protocol describing siRNA-based gene silencing in tumor models can serve as guide for the design of individual in vivo RNA interference experiments.