FRIDAY, Feb. 13, 2009 (HealthDay News) -- Scientists say certain tumors in mice have shrunk or disappeared after the animals were injected with genetically engineered immune system cells that target a protein found in certain human cancers.
The lab-altered T-cells zeroed in on mesothelin, a still mysterious protein produced in abundance by all pancreatic cancers and mesotheliomas, as well as many ovarian and non-small-cell lung cancers. The protein is believed to play a role in the spread and growth of cancer cells, a theory backed by past animal and human studies that found attacking mesothelin can shrink tumors.
"Based on the size of the tumors and the number of cells administered, we estimate that one mesothelin-targeted T-cell was able to kill about 40 tumor cells," study leader Dr. Carl H. June, a professor of pathology and laboratory medicine at the University of Pennsylvania School of Medicine, said in a news release issued by the school and its partner in the research, the U.S. National Institutes of Health. "This finding indicates that small doses of these cells may have potential in treating patients with large tumors."
According to the study, published in this week's online issue of the Proceedings of the National Academy of Sciences, the altered T-cells secrete proteins attracted to mesothelin. Once bound to the mesothelin, the T-cells fighting ability shifts into overdrive, producing multiple cytokines that boost the immune system. Other proteins are released by the T-cells to make them less susceptible to tumor's defenses.
The researchers tested the new T-cells on mice with tumors that developed from the implantation of human mesothelioma cells in their skin. When the T-cells were injected into tumors or into the veins of the mice, the tumors disappeared or shrank.
"Mesothelin is a promising candidate for generating tumor-targeting T-cells, given its limited expression in normal tissues and high expression in several cancers," study collaborator Dr. Ira Pastan, chief of the molecular biology laboratory of the U.S. National Cancer Institute's Center for Cancer Research, said in the news release.
Clinical trials that would use the altered T-cells in patients with mesothelioma and ovarian cancer are in the works, June said.
The U.S. National Cancer Institute has more about mesothelioma.