Scientists are exploiting the fact that neural stem cells are attracted to cancer cells because they emit a signal that is similar to a damaged neuron. The stem cell migrates to the cancer cell in order to repair the damage. If these stem cells are engineered to deliver a drug that can kill the tumor, it is a highly specific way of only selectively killing the tumor cells without damaging normal cells. In this case, in the brain. The drawback has been that it is hard to get neural stem cells but with new technology that can turn a skin cell into any type of stem cell, this overcomes that barrier. This research is still far off from being applicable to humans but is a huge step in that direction.