[Off-target effects update]
>>Nat Cell Biol. 2003 Sep;5(9):834-9. Epub 2003 Aug 24.
Activation of the interferon system by short-interfering RNAs.
Sledz CA, Holko M, De Veer MJ, Silverman RH, Williams BR.
[1] Department of Cancer Biology, Lerner Research Institute, NB40, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195 USA. [2] Molecular Virology Program, Case Western Reserve University, Cleveland, OH 44106, USA.
RNA interference (RNAi) is a powerful tool used to manipulate gene expression or determine gene function. One technique of expressing the short double-stranded (ds) RNA intermediates required for interference in mammalian systems is the introduction of short-interfering (si) RNAs. Although RNAi strategies are reliant on a high degree of specificity, little attention has been given to the potential non-specific effects that might be induced. Here, we found that transfection of siRNAs results in interferon (IFN)-mediated activation of the Jak-Stat pathway and global upregulation of IFN-stimulated genes. This effect is mediated by the dsRNA-dependent protein kinase, PKR, which is activated by 21-base-pair (bp) siRNAs and required for upregulation of IFN-beta in response to siRNAs. In addition, we show by using cell lines deficient in specific components mediating IFN action that the RNAi mechanism itself is independent of the interferon system. Thus, siRNAs have broad and complicating effects beyond the selective silencing of target genes when introduced into cells. This is of critical importance, as siRNAs are currently being explored for their potential therapeutic use.<<
But in the link in your post (thanks for that!), Williams and others downplay this issue, and say delivery is the big one. As I had speculated earlier, designing the siRNA to the optimal sequence to limit the off-target effects is doable (see the Tuschl interview). Further, Williams notes that while the interferon system is present in all humans, it is not usually a pathway found to be functional for tumor cell lines, so it's not a problem in every therapeutic area.
Cheers, Tuck |
