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Gene Therapy Shows Progress
The patients, all of whom had previously undergone surgery and immune-based treatments, were given chemotherapy to temporarily wipe out their immune systems. The engineered cells were then re-injected, with the hope that they would proliferate as the immune system recovered. The patients also received interleukin-2, which is a cytokine, or immune-system hormone.
One of the patients, a 52-year-old man, had melanoma in his neck, armpit and liver. It disappeared every place but one spot in the liver; surgeons removed that area. The other man, age 30, had cancer in his lungs and just outside them in the middle of the chest. His cancer disappeared, also.
The paper published yesterday provided few details of previous treatment the men had received. Rosenberg also did not analyze any of the reintroduced lymphocytes to see if, in fact, they had the ability to kill cancer cells.
Because of that, it is difficult to say with certainty that the engineered cells were responsible for the tumors' disappearance. However, Lotze, the Pittsburgh expert, said "it is unlikely" that it was the result of other treatments.
Rosenberg said he and his colleagues have engineered lymphocytes to recognize tumor markers, or antigens, found in about half of all cancers, including breast, colon and lung cancers. He said many of the modified cells have a much better ability to bind to tumor cells than the anti-melanoma cells he used in the study reported yesterday, which was conducted two years ago.
The research team recently applied to the Food and Drug Administration to try the new cells in about a hundred patients. The FDA is expected to respond to the request by the middle of this month.
Other researchers are working on similar strategies. Hwu, of M.D. Anderson, is engineering lymphocytes that have receptors for substances called chemokines that some tumors put out. This will help the lymphocytes home in on the cancer.
"We need to figure out how to get the T cells to migrate into the tumor more efficiently," he said. "If the T cells are able to recognize the cancer but are circulating in the bloodstream, then they are not on the battlefield where they need to be."