U.S. researchers say they've shown that blood stem cells can be engineered to create cancer-killing T-cells that seek out and attack a human melanoma.

Jerome Zack -- a scientist with the University of California, Los Angeles, Jonsson Comprehensive Cancer Center and the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research -- said the tests, conducted on mice, prove blood stem cells can be genetically altered in a living organism to fight cancer.

"We knew from previous studies that we could generate engineered T-cells, but would they work to fight cancer in a relevant model of human disease, such as melanoma," Zack said Tuesday in a release.

In four of the nine mice studied, the antigen-expressing melanomas were eliminated. In the other five mice, the antigen-expressing melanomas decreased in size.

Researcher Dimitrios Vatakis said the approach turned a few engineered stem cells into an army of T-cells that responded to the presence of the melanoma antigen.

"These cells can exist in the periphery of the blood and if they detect the melanoma antigen, they can replicate to fight the cancer," he said.

The study appeared Monday in the early online edition of the Proceedings of the National Academy of Sciences.