BioEd Online

Human embryonic stem cells could be used to seek out and destroy a fatal form of brain cancer, according to US researchers.

Experiments in mice with brain tumours show that the cells will migrate across the brain and deliver an anticancer payload. Human clinical trials could begin in two years' time, the researchers said on 24 October at the annual meeting of the Society for Neuroscience, held in San Diego.

Biologist Evan Snyder modified stem cells taken from a human embryo, adding a gene that made the cells express a tried and trusted antitumour molecule known as TRAIL. When injected into mice with brain tumours, the cells homed in on the cancer and pumped out enough TRAIL to cut the tumour size by an average of 50%, and up to 70% in some cases.

The cells are thought to track the tumour by following chemical signals emitted by the immune system molecules that attack, but ultimately fail to destroy, the cancer. Snyder, who is based at the Burnham Institute in La Jolla, California, says similar behaviour has been observed in other animal models of brain injury, where naturally occurring stem cells will travel towards and attempt to repair damaged areas.

Hunting satellites

Snyder believes the technique could be used to treat an aggressive type of tumour known as an intracranial glioblastoma. The cancer is impossible to cure using conventional techniques such as radiotherapy, because numerous satellite tumours form from the central cancer. Snyder, who was prompted to work in this area after losing a close friend to brain cancer, says the stem cells should track satellite tumours effectively.

"This is low-hanging fruit," he says. "All you are asking the stem cells to do is find the nasty bit, get rid of it and not cause mischief along the way."

His work is conducted with Kook In Park of the Yonsei University College of Medicine in Seoul, South Korea. The pair stress that the technique will not remove the tumours on its own, but they would like to run clinical trials on patients for whom conventional treatment has failed.

The stem cells could be added to the cavity left behind after a central tumour has been surgical removed, or injected directly into the brain. Snyder is now looking for a medical company to support his work.

Snyder adds that the work is an important proof of principle and that TRAIL is not necessarily the best way of attacking cancer. Stem cells could be modified to express other anticancer molecules, or a combination of cells, each equipped with different molecules, could be used in concert.