Genetic engineering promises improved bone marrow transplants

First clinical trial shows partial donors can be used in blood cancer treatments. Andrew Masterson reports.

Bone marrow transplants involve major surgery, but can be the best hope for bone cancer patients.

Bone marrow transplants involve major surgery, but can be the best hope for bone cancer patients.

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More people may soon be able to receive bone marrow transplants for the treatment of bone cancer, following a successful clinical trial carried out in Australia.

For people with certain high-risk forms of blood cancers, such as leukaemia and lymphoma, bone marrow transplants are the only clinical option with a chance of success.

Sadly, however, many patients never have the opportunity to undergo the procedure because a suitably matched donor cannot be found.

The main criteria for matching bone marrow content is the immune cell profiles of both parties.

“The key to bone marrow transplantation is the immune cells. Immune cells are a double-edged sword – they are necessary for fighting cancer and infection but they can also cause unwanted tissue damage, known as graft-versus-host disease,” explains Siok-Keen Tey of the QIMR Berghofer medical research institute in Queensland, Australia, who led the latest trial.

Searching for a way to reduce the risk of incompatibility, Tey and her colleagues turned to genetic engineering.

Using cells derived from partially matched donors, they inserted an extra gene which functions essentially as a kill-switch. If the transplanted bone marrow starts to cause graft-versus-host disease, the extra gene kills them off.

In a Phase 1 clinical trial – to ascertain the safety of the procedure – blood cancer patients first received a transplant from a part-matched donor, followed by the genetically engineered immune cells.

The results, which appear in the journal Clinical Cancer Research, were impressive, the researchers believe.

“What we found really amazing was that these immune cells can massively grow in number in the patients,” Tey says.

“We were able to show, using two independent molecular techniques that a single genetically modified immune cell, when challenged by a cancer, could split into millions and millions of cells within a few days.

“This immense capacity for rapid expansion was something that had not been shown before and really demonstrates the ‘power of one’: One cell, if it is the right cell, can grow rapidly and help control cancer or infection.”

The researchers are now planning a larger clinical trial.

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