Scientists have found that certain unique properties of the rabies virus may hold promise for treating brain cancer patients. The virus, itself responsible for the deaths of tens of thousands annually, has the ability to use nerve cells as a path to infect brain tissue. Scientists are trying to emulate this process to bring anti-tumor nanoparticles directly into brain tumors. The approach has so far only been found successful in mice, but success in humans would mean a new way to treat tumors without hurting other healthy cells.
Rabies, which is most often transmitted through bites from infected animals, uses hijacked nerve cells to make its way from infected muscle tissue to the brain. This unique ability helps rabies to bypass the blood-brain barrier, a membrane which helps to defend from pathogens in the bloodstream. Unfortunately, this barrier can also prevent cancer drugs from reaching infected cells. Scientists are now using the resourceful rabies virus as a model to get around this problem. Researchers have already put anti-cancer drugs into nanoparticles, which are then coated with part of the rabies surface protein that helps the virus to enter the central nervous system.
Recently, researchers from Sungkyunkwan University in Suwon, South Korea have pushed this idea even further. Yu Seok Youn, an expert on nanoparticles, and his team, have produced gold particles with the same shape and size as the rabies virus. With more surface area than spherical particles, the particles improve the ability of the rabies protein to bind with receptors that allow for entry in to the nervous system. While these particles do not contain any drugs, the gold particles absorb laser light easily, heating them to kill nearby tissue.
The team then injected the gold particles into the veins of four mice with brain tumors. The nanoparticles made their way to the brain, building up near the sites of tumors. Using an infrared laser, the team heated the particles to almost 50 degrees Celsius. The laser did not harm skin or bone, but allowed heat to radiate from the gold particles, significantly reducing the size of the tumors.
Another experiment on mice with tumor cells injected into their flanks found that two of the mice had their tumors disappear after 7 days. The initial experiment reduced tumors to roughly half of their original size.