Scientists in the United States have genetically engineered normal immune cells to become specialized fighters and used them to attack cancerous tumours.
Researchers at the National Cancer Institute (NCI) have demonstrated for the first time that such engineered cells can persist in the body and shrink large tumours in humans.
Of 17 people with advanced melanoma, a deadly form of skin cancer, who received the experimental treatment, two saw their tumours shrink and were declared clinically free of disease more than a year and half after the therapy began.
Steven A. Rosenberg of the National Cancer Institute and his team say the work represents the first time that gene manipulations have been shown to cause tumour regression in humans, and has demonstrated ways to engineer similar immune cells in the laboratory that would attack more common tumours such as breast, lung and liver cancers.
However fifteen patients failed to respond to the treatment and they say more work is needed to make it more effective.
The researchers removed tumour-fighting T cells from melanoma patients and multiplied these cells in the laboratory.
Chemotherapy was then used to clear out the patient's old T cells and the researchers re-populated the patients' immune systems with the new fighter cells.
Rosenberg says as some people with melanoma lack the tumour-fighting T cells, they had to come up with a way to create these types of T cells from scratch.
T cells carry a receptor protein on their surface that recognizes specific molecules called antigens on tumour cells and some cells contain genes that make a T cell receptor that targets melanoma cells, while other cells contain genes that make a T cell receptor that targets breast or lung cancer cells.
By removing normal T cells from people with melanoma, the researchers were able to genetically engineer them and create tumour fighters which were then returned to the body to rebuild the patients' immune systems.