Scientists at MIT report a breakthrough in growing so called cancer stem cells that could aid research into the disease.

The researchers have found a way to grow large quantities of cells that initiate tumours. These are not normally available in large quantities, so the discovery could be a real boon to those who study them.

The work also suggests that some normal cells, once they become cancerous, are more prone to becoming stem cells than others. These cells are also more likely to cause the cancer to spread from one part of the body to another, the researchers said.

MIT biology professor Robert Weinberg says these findings run contrary to conventional wisdom that any cell can, with the right alterations and mutations, become malignant and acquire the ability to spread to other tissues.

The discovery was somewhat serendipitous. Tan Ince, the researcher who first engineered the "stem cells", did not set out to do so.

As a postdoc in Weinberg's lab, Ince was trying to create breast cancer models that look right under the microscope and behave as they do in patients. To this end he developed a new culture medium to grow a type of breast cell that normally dies in culture.

After following standard procedure and inserting a few genes to make the cell cancerous, Ince discovered that he had created a particularly powerful carcinogen. Tests on mice saw the rodents quickly develop massive, fatal tumours that spread to other tissues, even when the mice were injected with as few as 100 cancerous cells.

Ordinarily, scientists expect to see no effect with fewer than a million cells injected.

"The operational definition of a cancer stem cell is the ability to initiate a tumour, so these are cancer stem cells," Weinberg says.

The work is published in the 13 August edition of Cancer Cell. ®

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