"A team led by John Yu at the Cedars-Sinai Medical Center in Los Angeles took neural stem cells from mice fetuses and genetically engineered them to produce interleukin 12. This is an immune stimulating chemical known to kill gliomas. The team then injected the modified stem cells into implanted gliomas in the brains of mice. "

This is so neat.

New Scientist - 'Seek and destroy' stem cells kill brain tumours