Extracting cancers cells from transplants

Cells that might cause cancer can now be extracted from transplants grown from embryonic stem cells, removing a major barrier to this kind of tissue repair. What's more, if things go wrong, the entire transplant could be ordered to self-destruct.

At the moment, specialised tissues grown from ESCs are always contaminated with stem cells that have not differentiated into any specialised cell type. When transplanted into mice, these cells often cause a form of tumour called a teratoma. The fear is that the same thing could happen in humans given transplants grown from ESCs.

The gene for a jellyfish protein called green fluorescent protein has been linked to the control region of another gene that is only expressed in stem cells. This was then put this into human ESCs. When tissues are grown from these cells, any remaining stem cells fluoresce green in UV light. A machine called a cell sorter can then separate them out.

In case patients or regulators have qualms about transplants containing a jellyfish gene, fluorescent antibodies have been created that can bind to particular cell types. This allows the marked cells to be removed by cell-sorting machines without any genetic engineering.

Similar methods are already being used to hunt down any cancer cells remaining in the blood of leukaemia patients who are in remission.

A back-up plan is also available. "Suicide" genes are being inserted into human ESCs that make them self-destruct when exposed to an antibiotic. So if a transplant goes awry, or shows signs of becoming cancerous, it could be killed off with a short course of drugs.

Item provided courtesy of New Scientist