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Tuesday, Octoberテつ* 15, 2002. Posted: 11:52:17 (AEDT)

Stem cells used to treat brain cancer in mice
Researchers say injecting neural stem cells engineered to produce a cancer-killing protein into mice with brain cancer extends the animals' survival and even immunises a third of them against the cancer.

"Malignant brain tumors are highly invasive. The main tumor mass often spawns outgrowth ... this is a way to target cancer cells that migrate away from the primary brain tumor," said Dr Moneeb Ehtesham, an author of the study conducted at Cedars-Sinai Medical Centre in Los Angeles.

The results are published in the latest issue of the journal, Cancer Research.

Currently, the standard treatment for brain tumors is surgical removal but tumors often recur because the migrated tumor cells can not be found, he said.

The Cedars-Sinai researcher theorised that neural stem cells could be used to deliver interleukin 12 (IL-12), a potent anti-tumor agent, to cancerous brain tumors because preliminary evidence showed that the cells were capable of tracking migrating cancer cells within the brain and they were used in other animal studies to deliver another therapeutic protein.

"This is a precise way of tracking cells -- like a heat-seeking missile delivering a toxic payload," said Dr Keith Black, another of the study's authors.

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.

"We found that inoculating the mice with IL-12-secreting stem cells significantly lengthened survival and we were able to completely eradicate the cancer in 30 per cent of the test animals," Dr Ehtesham said. The mice in which the cancer was wiped out are still alive, he noted.

Overall, median survival for the untreated mice was 25-35 days after tumors were established but lifespans increased by 50 per cent in the treated group, the researcher said.

"It may not sound like a lot, but a 50 per cent increase in survival is huge," Dr Ehtesham said.

Ultimately, the researchers said, the idea would be to harvest stem cells from the bone marrow of individual brain cancer patients, attach IL-12 and introduce them back into the brain to track down remaining malignant cells.

Dr Black said work is now underway to develop a workable method for harvesting the neural stem cells from bone marrow.

He estimated it will be another 18 months to two years before the therapy could be tested in humans.

The researcher also noted that the exact mechanism that enables neural stem cells to track malignant brain tumors is unknown but it could exist in other stem cell types, such as breast or lung, which could then also be engineered to treat different types of cancer.