Gene Therapy Halts Skin Cancer
Researchers Shrink Tumors in 2 Patients With Advanced Melanoma
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 a kind of immune cell called a T cell. The gene carries the code for a specific tumor-targeting molecule called a T-cell receptor or TCR. Once the cell has the tumor-targeting TCR, it is able to seek out and uproot tumors.
"We are currently treating advanced melanoma patients using [this technique]," Rosenberg said, in a news release.
Promise for Lung, Breast, Other Cancers
Rosenberg's team previously showed that tumor-fighting cells called tumor-infiltrating lymphocytes or TILs can be extracted from a melanoma patient. The TILs are multiplied in the lab, and -- after the patient undergoes chemotherapy to kill off existing white blood cells -- given back to the patient.
In 50% of patients, this technique shrinks the tumor -- to date, a much higher success rate than seen with the genetically engineered cells. But there's a problem. These natural tumor-fighting cells aren't easy to find.
An even bigger problem is that this technique is practical only for melanoma. Natural antitumor immune cells are much rarer for other cancers.
That's why genetically engineered antitumor immune cells are a breakthrough, says Patrick Hwu, MD, chairman of the melanoma department at the University of Texas MD Anderson Cancer Center. Hwu is a former member of the Rosenberg team.
"The Rosenberg group's finding is exciting because for the first time you don't have to fish out TILs," Hwu tells WebMD. "You can train any T cell to recognize the tumor. It opens up the possibility of doing T-cell therapy beyond just melanoma -- for lung and breast tumors, for example."
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.
Nevertheless, the 2-in-17 success rate means there's a lot more work to do.
Rosenberg's team is exploring several strategies, such as going back to the strategy of using radiation or chemotherapy to kill off the rest of a patient's white blood cells. If this is necessary, the treatment will be used only in patients in relatively good health.
The researchers also are working to give the genetically engineered cells additional tumor-fighting tools.