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Aug. 31, 2006 -- Genetic engineers now can arm normal white blood cells with tools that let them weed out cancer cells and shrink large tumors.
Researchers in a National Cancer Institute study had success using the technique to treat skin cancerskin cancer in two men.
"These results represent the first time gene therapy has been used successfully to treat cancer," said NIH director Elias A. Zerhouni, MD, in a news release. "We hope it will be applicable not only to melanomamelanoma, but also for a broad range of common cancers."
The genetically engineered cells can persist in the body for at least two months, report researchers including Steven A. Rosenberg, MD, PhD.
The researchers use a virus to transfer a gene into the normal blood cells. The gene carries the code for a specific tumor-targeting molecule called a T-cell receptor or TCR. Once it has the TCR, the cell is able to seek out and uproot tumors.
"We are currently treating advanced melanoma patients using [this technique]," Rosenberg said, in a news release.
His team has also been able to engineer white blood cells aimed at other cancers, including breast and lung cancers. The researchers report their findings in the Aug. 31 online edition of the journal Science.
Only Partial Success -- So Far
Rosenberg tried different versions of the treatment on 17 patients with late-stage melanoma that was spreading rapidly through their bodies. It freed two of the patients from the disease.
One is a 52-year-old man whose cancer had spread to his armpit and liver. The tumor in his armpit went away completely. His liver tumor shrank by 89%, to a point where doctors could surgically remove it. He was disease-free 19 months after treatments.
The other patient is a 30-year-old man whose cancer spread to his lung. After treatment, the lung tumor shrank. He was disease-free 18 months after treatment.
The new technique aims to improve on an older strategy called "adoptive lymphocyte transfer." This old adoptive transfer technique depends on finding tumor-specific immune cells in patients' blood.
Natural tumor-specific cells aren't easy to find. But when they can be found, the cells are removed and grown in the laboratory. Meanwhile, the rest of the patients' white blood cells are killed by radiation. Then the lab-grown cells are transferred back to the patient. About half the time, this has a powerful cancer-fighting effect.
The new technique would avoid many of the pitfalls of the old one by turning normal cells into tumor-fighting cells. But the 2-in-17 success rate means there's a lot more work to do.
Rosenberg's team is exploring several strategies, including using radiation to kill off the rest of a patient's white blood cells to give the new tumor-fighting cells more room to grow. The researchers also are working to give the genetically engineered cells additional tumor-fighting tools.
SOURCES: Morgan, R.A. Science, online Science Express edition published Aug. 31, 2006. News release, National Cancer Institute. News release, American Association for the Advancement of Science.