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GENETICALLY engineered stem cells can hunt down and kill cancerous brain
cells, say researchers in the US.

Brain cancers can be almost impossible to treat since they spread so quickly.
Often, a few cancer cells set off on their own and establish new tumours. Neural
stem cells can also migrate throughout the brain, so Evan Snyder of Harvard
Medical School in Boston and his colleagues wondered if they are drawn to
injured areas, such as tumours.

They injected neural stem cells into rats with brain cancer. Some of the
animals got injections into the tumour, but others were injected on the opposite
side of the brain鈥攐r even in the tail.

Within just a few days, the transplanted stem cells had migrated significant
distances through healthy tissue to get to the cancer cells. In all cases, the
neural stem cells were found to have migrated throughout the tumour, but stopped
at its edge.

The only exception was when they trailed rogue tumour cells migrating away
from the main tumour. 鈥淭he result went beyond my wildest expectations,鈥� says
Snyder. 鈥淸The stem cells] are riding these cells piggyback, and chasing tumours
from the other side of the brain.鈥�

The researchers repeated the experiment with stem cells modified to make an
enzyme that converts a non-toxic substance into a cancer-killing agent.
Injecting both the 鈥減rodrug鈥� and stem cells into rats reduced tumour mass by 80
per cent, they found.