Adoptive Transfer

New Therapy Trains Killer T-cells To Fight Cancer

By Pascal Barollier

WASHINGTON

An experimental cancer treatment that replaces a patient's immune system with cancer-fighting cells has shown promising results in preliminary trials.

    Researchers at the National Cancer Institute who tested the technique on 13 patients with a deadly form of melanoma or skin cancer found that it shrank the tumors of six of their volunteers by half.

    The six volunteers showed no growth or appearance of new tumors. Four additional patients showed mixed results, with some tumors regressing, while the remaining three reported no benefits from the therapy. All 13 had previously failed to respond to standard treatment.

    The therapy, known as "adoptive transfer," uses the latest advances in immunotherapy to program the body's immune system to combat the cancer cells. During the clinical trial, researchers used a small fragment of each patient's melanoma tumor to grow T-cells in the laboratory, using T- or killer immune cells taken from the patients.

    Once these T-cells, which were programmed to attack the cancer cells by virtue of their previous exposure to the tumor, had multiplied to a sufficient number, they were administered to the patient. The volunteers were also given an immune system booster in the form of a high dose of protein called interleukin-2, which stimulates continued T-cell growth in the body. The laboratory-cultivated T-cells were used to re-colonize the volunteer's own immune system which had been depleted by chemotherapy in order to remove ineffective T-cells.

    Tests showed the new cells went to work "multiplying rapidly and attacking tumor tissue." They persisted for several months, killing off 95 percent of the cancerous tissue in two of the patients.

    While scientists have used this approach before to treat cancer, the success of this experiment, such as it was, was due largely to advances in immunotherapy, researchers said.

    "In the past, only a fraction of a percent of the cells we injected were able to survive, and they would persist for only a few days," said the National Cancer Institute's Steven Rosenberg, the lead researcher on the study. "We have been able to generate a very large number of immune cells that appear in the blood and constitute a majority of the immune system of the patient. These persist for over four months and are able to attack the tumor."

    While the technique is still very much in its infancy, the researchers are hopeful it could be refined to treat other types of cancer, and infectious diseases such as AIDS.