Scientists have used stem cells to treat brain cancer in mice.

Not only did the treatment extend the animals' survival, it also appeared to wipe out the cancer completely in almost one in three cases.

This is a precise way of tracking cells

Dr Keith Black

The researchers, from the Cedars-Sinai Medical Center in Los Angeles, took immature neural (nerve) cells from the bone marrow and used gene therapy to stimulate them to produce a cancer-killing protein.

The cells were then injected into mice with brain tumours.

Currently, the standard treatment for brain tumours is surgery, However, some tumours recur because cells have migrated away from the main site, and cannot be found.

The researchers were particularly keen to target these migratory cells.

Tracking device

They selected neural stem cells for their experiment because there is evidence that these cells are capable of tracking cancer cells as they move around the brain.

Although the way they are able to do this is still unclear, the cells have already been used in similar experiments to deliver other therapeutic proteins to the brain.

Researcher Dr Keith Black said: "This is a precise way of tracking cells - like a heat-seeking missile delivering a toxic payload."

Untreated mice lived on average for 25-35 days after developing a brain tumour.

But in the treated mice average survival time was increased by 50%.

The mice in which the cancer was wiped out are still alive.

Researcher Dr Moneeb Ehtesham said: "It may not sound like a lot, but a 50% increase in survival is huge."

Bone marrow harvest

Ultimately, the researchers hope to harvest stem cells from the bone marrow of individual brain cancer patients, attach the cancer-killing protein and introduce them back into the brain to track down remaining malignant cells.

Work is now underway to develop a workable method for harvesting the neural stem cells from bone marrow.

They estimate the therapy could be ready to test on humans in 18 months.

Eventually, they hope it will eventually also prove useful in treating other types of cancer.

Stem cells, which are derived from embryos, foetuses or umbilical cords as well as a person's own tissue, are the master cells which create all the body's specific cell types.

The research is published in the journal Cancer Research.