"There are very, very few selective molecules out there like this," Vivek Rangnekar, professor of radiation medicine in the University of Kentucky College of Medicine, said in a statement.

"If you look at the pain that cancer patients go through, not just from the disease, but also from the treatment -- it's excruciating," Rangnekar said. "If you can not only treat the cancer, but also not harm the patient, that's a major breakthrough. That's happening with these animals."

"The mouse itself does not express a large number of copies of this gene, but the pups do, and then their pups start expressing the gene," Rangnekar said.