Scientists at Stanford University Medical Center have developed a technique for turning off harmful genes and used it to cure mice of cancer.

In plants and lower organisms such as flies, scientists have been able to turn off genes by inserting RNA, which cells use to create proteins. By injecting inhibitory RNA, researchers can effectively prevent disease-causing genes from functioning by preventing the creation of harmful proteins.

In higher organisms such as mice, previous attempts at injecting inhibitory RNA to turn off genes had been unsuccessful. But scientists from Stanford University have reported in today’s issue of the journal Science that they have found a successful method and used it to cure mice of cancer.

Cancer usually occurs after cells accumulate a number of mutations in cancer-related genes called oncogenes. Because of this, most scientists had thought that gene therapy for cancer would be difficult if not impossible because of the number of genes involved and the fact that the genes would return to causing disease when treatment stopped.

But in the Stanford experiment, researchers interfered with just one mutant gene. And when treatment stopped after 10 days, the cancer usually didn’t return. When it did, another 10-day treatment usually stopped it again.

The process of switching off harmful genes could have applications for a number of diseases. But the researchers caution that results that show up in mice often don’t apply to humans.