Many readers will be familiar with the concept of RNA interference. RNAi is a system in the cells of most higher organisms that regulates gene expression. The mechanism is respectably complex (see Nature Reviews RNAi collection), but the essence is that specific double-stranded RNA molecules can silence the expression of target genes.
One can easily extrapolate the potential practical application of RNAi: if unregulated expression of a gene is leading to a disease state, then tamp down the gene with RNAi and cure the disease.
This is easier said than done, of course, but a recent publication provides a proof of concept in humans (Nature 464:7291 [15 April 2010] 1067–1070). The authors, based in California, Texas, and Massachusetts, administered small interfering RNAs (siRNAs) to patients with advanced melanoma. Two tricks were used: first, nanoparticles carried the siRNA, because naked RNA cannot be usefully administered to humans; and second, the nanoparticles were directed to the tumor cells by also attaching a tumor-specific ligand.
The results show for the first time that siRNA can elicit the RNA interference response in human patients. Further, the target gene (ribonuceotide reductase) is indeed down regulated by the treatment, so the predicted mechanism appears to be operative.
The clinical trial is ongoing, so, although the results show that RNAi can be employed as a gene-specific therapy, we don’t yet know if the therapy worked to make the patients better. Hope so.