One of the most promising ways to tackle cancer is by improving gene therapy — the manipulation of defective genes. Now, Yoshihisa Namiki and co-workers at the Jikei University School of Medicine in Japan1 describe a novel way to improve gene therapy by guiding genetic agents to tumors using magnetic nanoparticles and a magnetic field.

The study is primarily aimed at treating gastric cancer, one of the biggest public concerns in Japan and a form of cancer for which gene therapy has had limited success. “Genetic factors in Japanese people, Japanese eating habits such as high-salt dishes, and the prevalence of the highly toxic bacterium Helicobacter pylori cause a big health problem,” says Namiki.

Magnetic particles are promising vessels for delivering genetic agents because they can be ‘steered’ directly to the tumor using a magnetic field. However, most magnetic-biological hybrid particles are time-consuming and complicated to prepare.

Fig. 1: LipoMag nanostructures for delivery of siRNA to cancerous tumor sites. The assembly process (clockwise from left) begins with magnetite nanocrystal cores (gray), which are coated with oleic acid (green) then a cationic lipid shell (pink), and finally affixed with siRNA strands. 2009 Yoshihisa Namiki

Namiki and his co-workers developed a simple new approach to the problem, which they have named ‘LipoMag’. LipoMag particles consist of magnetite nanocrystal cores coated with oleic acid and a layer of lipids to which nucleic acid can bind (Fig. 1).

The researchers functionalized their LipoMag particles with pieces of small interfering RNA (siRNA) designed to knock down the expression of EGFR, a gene associated with tumor progression. They injected the particles into mice with gastric tumors, and glued magnets onto or under the skin near tumor lesions. The mice showed an impressive 50% average reduction in tumor growth after 28 days.

Mice given a commercially available magnetic treatment called PolyMag showed no changes in their tumors. “PolyMag formed large clusters of over one micrometer in size, which are easily removed by the reticuloendothelial system in the lungs, liver and spleen,” says Namiki. LipoMag particles do not seem to form such clusters, and more importantly, don’t seem to have any adverse effect on the body.

The researchers are hopeful about the future of their invention. “Our system could treat other types of cancer, because it targets tumor vessels and inhibits tumor angiogenesis,” says Namiki. “We will soon perform clinical trials of LipoMag and transplantable magnets.”