Gene-silencing RNAs get guidance

An RNA guidance systemcan be used to target gene-silencing RNA molecules to specific cells, according to two independent reports. Delivering appropriate short interfering RNAs (siRNAs) is a potential therapeutic approach for killing cancer cells. In both studies, the researchers use ligand-binding RNA molecules called aptamers to pilot siRNA molecules to prostate cancer cells. The aptamers recognize a cell-surface receptor specific to prostate cancer. Bruce A. Sullenger and coworkers at Duke University Medical Center have shown that injecting chimeric aptamer-siRNA molecules into mouse tumors results in cell death and tumor shrinkage (Nat. Biotechnol., published online June 25). Matthew Levy, Andrew D. Ellington, and coworkers at the University of Texas, Austin, connect a different aptamer to siRNA via a streptavidin link (Nucl. Acids Res., published online June 1). In both cases, the RNA molecules enter only cells with the prostate-cancer-specific receptor on the surface. The siRNAs effectively silence their target genes in both cases. It remains to be seen whether either version of the aptamer-siRNA conjugates can be adapted for systemic delivery.