A new formulation of magnetic nanoparticles used to deliver nucleic acids that slow tumour progression in mice is reported online in Nature Nanotechnology this week. Cancer gene silencing RNA delivered using these nanoparticles showed better anti-tumour effects than when delivered using commercially available nanoparticles. This formulation is expected to be an effective gene-delivery system for treating a variety of cancers.

The success of cancer gene therapy relies on effective delivery of small interfering RNA (siRNA) to the specific genes that cause disease, in order to switch them off. Yoshihisa Namiki and colleagues injected magnetic nanoparticles carrying an optimized sequence of siRNA into the bloodstream of mice. They then guided the siRNA-carrying nanoparticles to the tumour using magnets that were either glued on or implanted under the skin near the tumour. The siRNA – which was designed to silence the expression of a particular gene in the blood vessels of tumours – reached its destination and stopped the growth of tumour blood vessels after an optimized dose of eight injections. The team showed that tumour growth decreased without any adverse immune reaction or side effects and further analysis confirmed that the gene-silencing effects were due to RNA interference.

The authors believe that this new formulation – which showed better anti-tumour effects than the magnetic nanoparticles available at present – could be a robust gene-delivery system for a variety of cancer gene therapy applications.

DOI: 10.1038/nnano.2009.202